Massachusetts Institute of Technology
ITC Consortium
FUTURE DIRECTIONS OF
PERSONAL MULTIMEDIA COMMUNICATION SPACE
Investigation of wireless markets, systems, and standards in regard to multimedia over IP
Christer Englund
MIT Center for Technology, Policy and Industrial Development
Aug 15, 1997
EXECUTIVE SUMMARY
Mobile communications and Internet based computer communications are the two fastest growing
areas of communications indicating an enormous business potential in the intersection of these
two domains. Since the introduction of cellular networks, wireless communications have focused
on speech only, while mobile data has played a minor role. This paradigm is likely to change
drastically in the near future. A new phenomenon, reflected by a nomadic lifestyle, is spreading all
over the industrialized countries. Clear evidence of this is discernible particularly in Japan and
Scandinavia. Nomadic lifestyle suggests that we are now at the advent of a new era of mobile
communications, which will be fueled by rapid evolution of key technologies such as mobile
computing, low-power consuming RISC and signal processor technologies, wireless channel
aggregation, wireless packet data, and Internet based multimedia communications.
The current trend of network evolution implies that the Internet will serve as a core for future
service provision, whereas traditional telecommunication networks offer access paths to those
services. Internet telephony reflects the beginning of a new communication era, which is characterized by running real-time applications over Internet/Intranet based computer communication
infrastructure. We can envision that soon they not only contain speech, but data, graphics and
video as well. It is obvious that also the nomadic users will require access to these services and
applications as they gain more popularity in the landline environments. Moreover, new wireless
Web applications are likely to emerge with no wireline counterpart.
Evolution of wireless communications will be driven by the rapidly growing Chinese market,
which is expected to be the largest one by year 2000. By its nature, this market is likely to
leverage new digital technologies, which enable low cost terminals, higher bandwidths, and
cheaper call rates. The downside of this technology is its limited coverage and vehicular operation
at low-velocities only. Industrialized countries will also benefit from this evolution, since they
share a growing need for high speed, low delay asymmetric wireless data access to the Internet.
Low-tier micro-cell technology is capable of addressing best those needs of current terrestrial
wireless systems. The problem of limited coverage will be solved with multi-mode transceivers.
We have characterized in this investigation the new paradigm of mobile communications by
introducing a virtual model of personal multimedia communication space. On the basis of our
model, we have reviewed the impact of international standards on low bit-rate real-time multimedia communications with some basic considerations of system architectures.
The feasibility of wireless Internet telephony over packet radio networks has been assessed. It
seems that the latency problem faced also in the wireline IP environments becomes overwhelming.
Moreover, wireless packet switched IP environments lack the cost incentive of the Internet. Endusers are not likely to accept such wireless Internet telephony. Full-fledged voice-over-IP in
wireless networks is not feasible before low cost, low latency wireless packet access is available.
The need for such a service is an open question. Therefore, usability experiments are needed.
Multimedia applications are likely to play much more important role as a driving force for voiceover-IP in wireless environments than in the fixed network. In a limited scale and in the medium
term, Web browsing with concurrent voice communication may become available, based on multilink packet radio extensions of current digital cellular networks.
ACKNOWLEDGEMENTS
I wish to thank professor Dan Roos head of MIT Center for technology, Policy and Industrial
Department (CTPID) and Dr. Lee McKnight, manager of ITC Project from for the opportunity to
do this investigation as a project team member of the Internet Telephony Consortium (ITC).
This 1 year tenure in MIT has meant a significant change in my career. When I came to MIT I had
to start everything from scratch, to collect all relevant source material, to build up a network and
get acquainted in the IP world, which was mostly alien to me. This required all my effort.
Moreover, it took some time to learn to use the MIT resources and the MIT way of doing
research, as well as get acquainted with the challenging new realm of Internet telephony.
Working conditions at CTPID have been very good and I have enjoyed many inspiring discussions
with MIT staff, in particular with Dr. McKnight and Ph.D. Student Joseph Bailey and other
members of the ITC project team. Joe Bailey’s help has also been indispensable in solving a
number of networking problems I have faced with my notebook computer.
I would like to thank also Agnes Chow for her friendly and encouraging attitude towards me and
all the guidance she has given to cope with the problems that a visiting scholar at MIT is bound to
come across with.
The interaction with the local Nokia staff as well as with that of Nokia Mobile Phones, Tampere,
Finland has been fruitful, in particular I have enjoyed many inspiring discussions with Raj Bansal.
Professor Olli Martikainen from Helsinki University of Technology (HUT) has given me some
valuable hints and ideas, how to tackle my wide topic. My intention is to continue my Ph.D.
studies under his supervision in HUT.
Furhtermore, I would like to mention Senior Research Scientist Eija Kaasinen from VTT
Information Technology has given many useful comments on the usability testbed and usability
testing issues.
My tenure would not have been possible without the financial support of VTT Information Technology and I would like to express special thanks to Research Director Pekka Silvennoinen, head
of VTT Information Technology. Moreover, I am very grateful for the scholarships I have been
granted by Wihuri Foundation and Telecom Finland, which have been important for funding my
participation in MIT courses as a special student.
Last but not least, I will thank my wife for her encouragement and my daughter, with whom I had
the opportunity to spend many happy moments together in Boston.
Cambridge, August 15, 1997
Christer Englund
TABLE OF CONTENTS
EXECUTIVE SUMMARY........................................................................................................ II
ACKNOWLEDGEMENTS....................................................................................................... III
TABLE OF CONTENTS..........................................................................................................IV
FIGURES .................................................................................................................................VI
TABLES................................................................................................................................. VII
1. INTRODUCTION .................................................................................................................. 3
2. OVERVIEW ON INTERNET AND MOBILE INDUSTRIES MARKETS............................. 5
2.1 World Market Evolution.................................................................................................... 5
2.2 Asian Market Outlook and its Implications ........................................................................ 6
2.3 Market Evolution of Cordless Phone Systems.................................................................... 8
2.4 Market Outlook of Wireless Data and Internet Access ....................................................... 9
2.5 Semiconductor Market Trends......................................................................................... 10
2.5.1 CPU Chips................................................................................................................ 11
2.5.2 Memory Chips .......................................................................................................... 11
2.5.3 Digital Signal Processor (DSP) and Programmable Logic Chips ................................ 12
2.5.4 Monolithic Microwave Integrated Circuits (MMIC).................................................. 12
2.6 Market Outlook on Batteries ........................................................................................... 12
3. BRIEF HISTORY OF PERSONAL COMMUNICATIONS.................................................. 15
3.1 Early Phase of Evolution ................................................................................................. 15
3.2 Second Phase of Evolution: Dawn of Personal Communications ...................................... 15
3.3 The 3rd Phase of Evolution: Digital Cellular ..................................................................... 16
4. OUTLOOK ON DIGITAL WIRELESS COMMUNICATION.............................................. 19
4.1 Overview on Existing Wireless Systems........................................................................... 19
4.1.1 Satellite and Other High Altitude Systems................................................................. 19
4.1.2 Digital Cellular Systems ............................................................................................ 20
4.1.3 Low-Tier Systems..................................................................................................... 24
4.1.4 Dedicated Data Networks ......................................................................................... 27
4.2 Evolution towards 3rd Generation Systems....................................................................... 29
4.2.1 Potential Threats to Wireless Communications.......................................................... 29
4.2.2 Technical Design Objectives for 3rd Generation Systems............................................ 29
4.2.3 Non-Terrestrial Systems ........................................................................................... 30
4.2.4 Upgrades of the 2nd Generation Terrestrial Networks ................................................ 31
4.3 Feasibility for Supporting Real-Time Multimedia Applications ......................................... 35
4.3.1 Delay Considerations ................................................................................................ 35
4.3.2 HW Considerations................................................................................................... 35
4.3.3 Cost and QoS Considerations ................................................................................... 35
4.3.4 Comparison of High-Tier and Low-Tier Systems ...................................................... 36
5. VIRTUAL MODEL OF PERSONAL MULTIMEDIA COMMUNICATION SPACE .......... 37
5.1 General............................................................................................................................ 37
5.2 Design Criteria ................................................................................................................ 38
5.2.1 User Interface ........................................................................................................... 38
5.2.2 Mobile Computing Environment ............................................................................... 39
5.2.3 QoS.......................................................................................................................... 40
5.2.4 User Indications and Help Functions ......................................................................... 40
5.3 Basic Architecture and Core Technologies....................................................................... 40
6. PRODUCT DESIGN AND MARKETING STRATEGY CONSIDERATIONS.................... 43
6.1 Adoption and Diffusion ................................................................................................... 43
6.2 Case Studies.................................................................................................................... 45
6.2.1 Case Study 1:Sony Walkman .................................................................................... 45
6.2.2 Case Study 2: Mobile phone ..................................................................................... 47
6.2.3 Case Study 3: Personal Digital assistant (PDA) ......................................................... 51
6.2.4 Summary and Conclusion.......................................................................................... 53
6.3 Terminal Environment of a Multimedia Walkman............................................................. 54
6.3.1 Characteristic Features.............................................................................................. 54
6.3.2 User Interface and Role of Agents ............................................................................ 55
6.3.4 Significance of Mobile-Aware Platforms ................................................................... 58
6.4 Perceptual Mapping......................................................................................................... 59
7. STANDARDS FOR INTERNET TELEPHONY AND MULTIMEDIA SYSTEMSError! Bookmark not def
7.1 Overview on ITU-T Standards......................................................................................... 50
7.2 Speech Codecs for Wireless Multimedia and Internet Telephony...................................... 51
7.2.1 Speech Coding Standards ......................................................................................... 51
7.2.2 Evaluation Methods of Speech Quality...................................................................... 51
7.2.3 Delays in Speech Communication ............................................................................. 52
7.3 ITU-T H.324 Recommendation [ITU 96d] ...................................................................... 53
7.3.1 H.324 Functional Entities and Communication Procedures........................................ 54
7.3.2 Call Initialization....................................................................................................... 55
7.3.3 Mobile Extension of H.324 (H.324/M)...................................................................... 56
7.4 ITU-T H.323 Recommendation [ITU 96e]....................................................................... 58
7.4.1 Audio ....................................................................................................................... 59
7.4.2 H.263 Video [ITU 96i] ............................................................................................. 60
7.4.3 Data ......................................................................................................................... 60
7.4.4 System, Media Stream and QoS Control ................................................................... 60
7.4.5 Wireless Interworking............................................................................................... 61
7.4.6 H.323 Extensions...................................................................................................... 62
7.5 IETF standards for RTP and RTCP (RFC 1890).............................................................. 63
7.6 Future Directions of Wireless Multimedia Standardization ............................................... 63
7.6.1 Potential H.323 Extensions ....................................................................................... 63
7.6.2 IETF RSVP Standard ............................................................................................... 65
7.6.3 MPEG4 Standard ..................................................................................................... 65
7.6.4 Global Initiatives for Future Wireless Standards ........................................................ 66
8. SYSTEM ARCHITECTURE CONSIDERATIONS.............................................................. 67
8.1 Classification of Applications........................................................................................... 67
8.2 Quality of Service [Framework for Wireless Multimedia .................................................. 69
8.2.1 QoS Reference Model and Design Principles............................................................. 69
8.2.2 QoS Parameter Values.............................................................................................. 70
8.3 Real-Time Services over Packet Radio Links ................................................................... 75
8.3.1 Reference Model....................................................................................................... 75
8.3.2 Routing and Mobility Management ........................................................................... 76
8.3.3 Multiple Access over Packet Radio ........................................................................... 77
8.3.4 Voice and Multimedia over Wireless IP..................................................................... 78
8.4 Real-Time Services on HCSCD Links.............................................................................. 82
8.4.1 Reference Model....................................................................................................... 82
8.4.2 Voice and Multimedia over Wireless Circuit Switched links to IP.............................. 82
8.4.3 H.323/M Scenario: Using CS Air Interface for Packet Transfer................................. 83
8.4.4 Addressing and Numbering ....................................................................................... 84
8.5 User Data Management ................................................................................................... 85
8.5.1 Self-Configuration of Service Profile......................................................................... 86
8.5.2 Customization of Application Content....................................................................... 87
8.6 Charging and Billing Principles ........................................................................................ 88
8.6.1 Wireless Link............................................................................................................ 88
8.6.2 Advice of Charge...................................................................................................... 88
8.7 Electronic Commerce and Payment.................................................................................. 89
9. USABILITY AND USER INTERFACE DESIGN CONSIDERATIONS ............................. 90
9.1 Usability and QoS Testbed Design................................................................................... 90
9.2 User Interface.................................................................................................................. 92
10. CONCLUSIONS................................................................................................................. 94
ABBREVIATIONS .................................................................................................................. 96
REFERENCES: ........................................................................................................................ 99
FIGURES
Figure 1 Installed base of mobile phone users in March 1997....................................................... 5
Figure 2 Markets of core technologies for portable smart appliances.......................................... 14
Figure 3 GSM architecture [Rap 96] ......................................................................................... 20
Figure 4 PACS System Architecture.......................................................................................... 24
Figure 5 Architecture of GSM High Speed Circuit Switched Data Service [Häm 96] ................. 33
Figure 6 Three realms of study and personal multimedia communication space .......................... 38
Figure 7 Architecture for personal multimedia communication space ......................................... 41
Figure 8 Positioning the products of case studies on Roger’s diffusion curve ............................. 44
Figure 9 US mobile phone users ................................................................................................ 48
Figure 10 Wireless service definitions factors (Source: Business Research Group[Mey 97])....... 50
Figure 11 Architecture of agent services.................................................................................... 56
Figure 12 Perceptual mapping of personal information appliances.............................................. 61
Figure 13 Product hierarchy of personal information appliances................................................. 62
Figure 14 Delay introducing entities in digital speech communicationError! Bookmark not defined.
Figure 15 H.324 block diagram [Lin 96].................................................................................... 54
Figure 16 Protocol architecture of a H.324 system .................................................................... 55
Figure 17 Error control scheme for H.324 in error-prone environments ..................................... 57
Figure 18 Protocol architecture of a H.324/M system ................................................................ 57
Figure 19 Block diagram of a H.323 terminal [ITU 96e]............................................................ 58
Figure 20 Protocol architecture for H.323 ................................................................................. 59
Figure 21 Illustration of interworking between H.323, and other H series terminals ................... 62
Figure 22 Suggested block diagram of a H.323/M terminal........................................................ 64
Figure 23 A potential protocol architecture for H.323/M ........................................................... 65
Figure 24 Taxonomy of Applications [Pet 96] ........................................................................... 67
Figure 25 Quality of Service and network performance reference model .................................... 69
Figure 26 QoS performance concept of ITU-T Rec. E.800 ........................................................ 71
Figure 27 GPRS Reference Model............................................................................................. 76
Figure 28 Routing of packets using the mobile IP protocol [Häm 96, Per 96a]........................... 77
Figure 29 Delay introducing entities in a call between wireless IP and H.324 terminals .............. 80
Figure 30 Delay introducing entities in a call between H.324/M and H.323 terminals ................. 82
Figure 31 A scenario of H.323 potential developments .............................................................. 84
Figure 32 Suggested testbed architecture................................................................................... 91
Figure 33 A model of a MMW remote controller with chording keys......................................... 93
TABLES
Table 1 Cellular penetration and markets in South-East Asia [HuR 96]........................................ 6
Table 2 Comparison of wireless system parameters [Gar 96],[Rap 97]....................................... 21
Table 3 Comparison of standardized low-tier mobile systems [Gar 96],[Rap 97],[Noe 96]......... 27
Table 4 Planned or ongoing satellite projects [Wil 96], [Nou 97], [Stu 96] ................................ 30
Table 5 Sony’s technological leadership in personal portable stereos [San 95]............................ 45
Table 6 Comparison of studied cases ......................................................................................... 53
Table 7 Assessed HW characteristics of a multimedia Walkman ................................................ 57
Table 8 Affinity diagram of a multimedia Walkman.................................................................... 64
Table 9 Phases of communication between two H.324 terminals.. Error! Bookmark not defined.
Table 10 Quality of Service Classes for MDC Applications........................................................ 72
Table 11 Suggested QoS classes for wireless low bit-rate multimedia applications ..................... 73
Table 12 Relationship between MMCF error free intervals of QoS Class 2 and BER.................. 75
Table 13 Transit delays of the Internet....................................................................................... 79
Table 14 Delay calculation of the configuration depicted in Fig. 28 [mobile IP to PSTN]........... 80
Table 15 Delay calculation of the configuration depicted in Fig. 29 [CS digital mobile to IP ] .... 83
1. INTRODUCTION
Mobile communications and Internet based computer communications are the two fastest
growing areas of communications indicating an enormous business potential in the
intersection of these two domains. Since the introduction of cellular networks, wireless
communications have focused on speech only, while mobile data has played a minor role.
We are now at the advent of a new era of mobile communications, which will be fueled by
rapid evolution of key technologies such as wearable computing, wireless channel
aggregation, wireless packet data, and Internet based multimedia applications. This
investigation deals with the concept personal multimedia communications space, which is
a new paradigm for personal communication. In this context, we study product concepts
and service architectures capable of supporting a whole plethora of new services and
applications.
Ubiquitous computing, a concept introduced by Mark Weiser from Xerox Palo Alto
research labs, is a state of computing made indistinguishable to the users [Wei 91], [Wei
93] and in which intelligence is dispersed all over in our physical environment. The
previously mentioned foreseen paradigm shift reflects Weiser’s scenario of ubiquitous
computing in the sense that computing is becoming more unobtrusive in the future
wireless portable information appliances, dedicated to serve the needs of our everyday life
in a similar manner like electric motors in all kinds of appliances from cameras to washing
machines. A widespread adoption of such appliances may change dramatically the inherent
nature of computing. As a result, the computer could be harnessed in the future to serve
us cost-effectively with much lower learning overhead. The driving force for lightweight,
low-power portable appliances is the continuing progress of semiconductor technology
[Mak 96], following the paradigm of Moore’s law.
The current trend of network evolution implies that the Internet will serve as a core for
future service provision, whereas traditional telecommunication networks offer access
paths to those services. Internet telephony reflects the beginning of a new communication
era, which is characterized by running real-time applications over Internet/Intranet based
computer communication infrastructure. We can envision that soon real-time applications
not only contain speech, but data, graphics and video as well. Running real-time multimedia in IP networks is a great technological challenge. Upgrading of network admission
control, policing, and billing technologies is necessary for giving quality of service
guarantees on peer-to-peer level. Furthermore, novel technologies for low bit rate
multimedia communications and digital wireless information appliances are emerging.
These trends suggest a change in the existing paradigm of wireless communications. We
can foresee, that the user’s natural need for accessing truly personalized information
content anywhere and anytime is gradually becoming a reality.
A new phenomenon, reflected by a nomadic lifestyle, is spreading all over the
industrialized countries. Clear evidence of this is discernible particularly in Japan and
Scandinavia. The nomadic lifestyle is characterized by young, well-dressed and business
oriented cellular phone users, engaged in conversation with their network in the streets,
railway stations and other public places. It is apparent that these nomadic users will
demand access from their portable terminals i.e. from mobile hosts any time and
anywhere [Häm 96] to same services and applications, that are accessible from wireline
networks. Therefore, the interoperability between mobile hosts in terms of Internet based
voice + data (VOI, voice-over-Internet) needs to be considered. Moreover, new wireless
Web applications are likely to emerge with no wireline counterpart to serve nomadic
users.
Besides nomadic lifestyle and other factors fueling wireless communications, we have also
handled some threats that may influence the evolution.
This task deliverable relates to the personal mobile multimedia research activity of Internet
Telephony Consortium of MIT. The concept of Internet telephony is ambiguous. If we
would focus on speech only a more precise term would be voice-over-IP. However, In
this context we have treated Internet telephony in a broader meaning on the basis of the
recently issued ITU-T H.323 standard, which addresses a complete real-time multimedia
system. This approach has been chosen also by VoIP Forum of IMTC, the largest
industrial cooperative body for furthering Internet telephony and respective standards
[VoIP97].
In the wireless context we aim at identifying basic operational and functional requirements
of an open service architecture, capable of supporting real-time personal multimedia
communications across narrowband tetherless links. Our aim is to focus on the
intersection of the Internet, wireless networks with enhanced data transfer capabilities,
and personal multimedia communications.
Special attention will be paid to usability considerations, user need for personalized
content, and interoperability with the Internet[Bra 94][Per 96a] as well as ITU-T H-323
and H.324 real-time multimedia systems.
Subsequently we have described the whole concept of such wireless communication
environment titled personal multimedia communication space, which would serve as a
foundation for ubiquitous personal multimedia communications of the 21th century. For
the time being, personal multimedia communication space is an abstraction which is based
on a virtual model. We intend to validate the model later on with practical usability tests in
a testbed as well as quantitative and qualitative measurements of user preferences using
the methodology presented by Glenn Urban and John Hauser [Urb93]. We have also
investigated the product and service concept from strategic and market acceptance point
view through input derived from case studies. The selected products for the case studies
are: a mobile phone, a personal digital assistant (PDA) and a portable audio cassette
recorder (“Sony Walkman” ™).
2. OVERVIEW ON INTERNET AND MOBILE
INDUSTRIES MARKETS
The intent of this section is to review the markets and assess how they may leverage
evolution of networks and enduser equipment.
2.1 World Market Evolution
The two most rapidly expanding forms of communication are Internet and mobile
communications. According to Internet demographics studies [Nie 96], access to Internet
jumped 50% from August 1995 to March 1996. This corresponds to 70-80% annual
growth. In January 1997 the total number of Internet Hosts was 16146000 [NW 97].
From these figures we derive a growth of 1 million hosts/month. Albeit the fact that there
is no reliable estimate of the number of Internet users connected to those hosts, it is likely
the number is around 60-80 million. The Internet penetration is dominated by US
continent with around 86 % of the estimated 18 million Internet hosts. For Europe the
figure is close to 10% and for Asia only 1,2%. Asia is expected to catch up in the next
few years due to the huge potential and rapid economic growth.
Installed base of mobile phone users in
March 1997
50
45
40
Million
35
30
25
Series1
20
15
10
5
0
USA
Europe
Asia
Other
Figure 1 Installed base of mobile phone users in March 1997
Currently the installed base of mobile phones is roughly twice as large as the number of
Internet users. According to data publicized by Cellular Telecommunications Industry
Association, the number of US mobile phone users was 33.8 million at the end of 1995
[Don 96] and the forecast for end of 1996 was 43.8 million. [Par 96] estimated that in
September 1996 the number was some 42 million, which is fairly well in line with the
CTIA forecast of the market growth [CTIA97]. Therefore, we can on good grounds
assume that 45 million by the end of 1996 is fairly accurate estimate. In Asia and Pacific
mobile phone subscribers amounted to 21.74 million at the end of 1995 [Brom 96] and
according to the market forecast of Jardine Fleming Securities 11.8 million more
subscribers signed up in 1996 entailing a user base of more than 30 million. In Europe the
figure is around the same as in Asia [ACT 96]. The European market is growing 40-50%
annually, but in Asia the growth rate is 70-80%. Therefore, the installed base in Asia is
now March 1997 around 40 million and in Europe 35 million. A rough estimate of mobile
phone users in Australia, South America, Africa, in states of former Soviet Union, and
other areas, not included in the above statistical surveys, is around 20 million. As a
conclusion, the number of mobile phone users is currently around 140 -150 million total
(see Fig. 1).
What is even more important that the market of Internet and mobile phone industries
continue to expand in the explosive manner we have witnessed during the past few years.
There is no doubt about the enormous, still almost entirely unexploited business potential,
that resides in the intersection of the two domains.
2.2 Asian Market Outlook and its Implications
The telecommunications market of Asian-Pacific area will impact deeply the evolution of
wireless communications. According to Coopers & Lybrand, the projected telecom
investments in Asia-Pacific area are $ 331 bn during the period 1995-2000. The predicted
Chinese share of the cake is enormous $ 120 bn [Tho 97].
Huge potential of the rapidly growing Chinese economy as well as Russia and other states
of the former Soviet Union will in particularly fuel the evolution of mobile telephony,
because of the poor coverage of landline subscriber networks and low penetration of
telephony, which was for example in China only 3,4% of households[WuW 96]. This is
the case also for some densely populated Asian countries such as India, Pakistan, Indonesia and Philippines with geographical circumstances that are less favorable for landline
telecommunications. Therefore, in many areas of the countries, there may not be any other
means for accessing the Internet than across a mobile link. By the year 2000 the Chinese
market is expected to become the largest in the world [McC 96] Even if the mobile
industries market is likely to saturate in some industrialized countries, the overall low
penetration and new markets fuel the growth. We can assess that in the medium and long
term, the market of mobile phones, either cellular and/or satellite ones as well as wireless
smartphones with a range of value-added features, will increase heavily.
Table 1 Cellular penetration and markets in South-East Asia [HuR 96]
Area
Hong Kong
Indonesia
Malaysia
Philippines
Singapore
Penetration of cellular services/% Cellular handheld market (in
of residents
millions)
1994
1995
1996
1997
1994
1995
1996
1997
7.2
8.7
10.0
14.0
0.440
0.530
0.610
0.854
0.06
0.1
0.15
0.21
0.121
0.205
0.308
0.431
2.5
3.0
3.4
3.6
0.495
0.611
0.699
0.750
0.24
0.32
0.44
0.61
0.162
0.226
0.317
0.443
7.8
8.5
9.2
10.1
0.221
0.243
0.267
0.294
Taiwan
Thailand
Total
2.7
0.88
2.8
1.04
3.7
1.2
4.7
1.5
0.562
0.517
2.518
0.594
0.620
3.029
0.766
0.744
3.711
0.996
0.893
4.661
Though 71% of Chinese population live in rural areas, the remaining 29%, which
correspond to 350 million people, represent most of the rapidly growing purchasing
power. For the rural areas, satellite systems are the optimum solution to offer quickly
telephone services. In urban areas, cellular networks are being launched in large quantities.
This is a natural course of development, because of the huge supply of terrestrial wireless
networks based on regional cellular standards. However, cellular networks are not fit for
meeting communication needs of all user groups.
Also for the other countries in South-East Asia, the market outlook suggests healthy
growth. The Table 1 [HuR 96] indicates that for the time being, the penetration levels are
so low that a huge unexploited potential still exists. Only in Hong Kong and Singapore,
the penetrations are higher. The predicted market volumes are fairly modest compared to
that of the enormous Chinese market. Hu et al point out that rather than reflecting the
overall demand in the region the figures presented in Table 1 indicate the achievable
penetrations and market growths determined by the available system capacities and
resources.
The evolving wireless communications market in the South-East Asia is likely to leverage
a paradigm shift from high-tier cellular vehicular systems to low-tier, low mobility
pedestrian systems due to following reasons:
• High density of Chinese urban population favors micro cell networks
• The amount of pedestrians and slow motion vehicles in Chinese cities is significantly
higher than in USA, Japan and Europe
• The road infrastructure of China is less developed restricting the velocities of the
vehicular traffic
• Wireless replacement of a landline subscriber network i.e. wireless local loop (“the last
mile”) is the becoming a viable alternative.
• The Chinese market is likely to exert special emphasis on low-cost mobile services and
enduser equipment.
The above bullet points hold true also for many of the other South-East Asian countries.
Currently, many consortia are setting up both analog and digital cellular networks in
Chinese metropolitan areas such as Shanghai. As the cellular penetration increases, the
demand for a low-tier network will increase in the same fashion as in Japan, where the
break-through of PHS took place many years after the launch of cellular networks. The
Chinese low-tier market is probably going to be quite different from the Japanese one. In
Japan the need to use low-tier wireless technology for the last mile of the wireline network
is much lower. Also the yuppie label of PHS users may not at all match with the Chinese
user profile.
2.3 Market Evolution of Cordless Phone Systems
For many years after their introduction, low-tier cordless phone systems such as PHS have
been successful in a fairly limited scale, but now the situation is changing. In Japan the
number of PHS users has jumped to 4 million after 18 months from release and in March
1997 it is expected to reach 6 million [Har 96]. A PHS phone is the first Japanese
consumer product in history to sell 1 million units in its first year of launch. In Europe
orders of DECT handhelds placed for this year amounts to 4,5 million [Tut 96]. In USA
the deployment of ANSI standardized PACS networks has not begun yet, but there are
indications that the roll-out will take place soon. [Noe 96].
As far as the other East-Asian countries are concerned, Hu et al. [HuR 96] emphasize that
there is a market need for a low-tier system such as PACS based on respective arguments
than those given in the previous Section. These countries, in particular Hong Kong and
Taiwan are likely to act as market drivers also for the market of the Chinese mother
country. Therefore, there are very strong signs that China and the other South-East Asian
countries will play a leading role in the deployment of PACS. These countries are not
likely to adopt PHS as they have not done so for PDC either. PACS is by far the most
advanced low-tier system and Taiwan has already decided to provide PACS for wireless
local loops in 1997 and a public PACS network in 1998 [Wu-J 96].
Compared to Asia, the market drivers are different in USA and Europe where low-tier
wireless systems are expected to mainly support provision of Wireless Centrex and PBX
services. Furthermore, the need for better performance in indoor environments by using
dual mode handhelds will leverage the evolution of low-tier wireless systems. These are an
ideal complementary solution for macrocellular high-tier systems by filling the gap of
limited indoor performance and by serving very high-traffic densely populated urban areas.
The latter argument is becoming a more and more important market driver for PHS in
Japan, because PDC capacity cannot be extended any more due to lack of frequencies to
meet the rapidly increasing traffic demand, in particular in the Tokyo-Osaka-Nagoya
passage area. In USA, Universal Service may be extended to wireless networks, which
would open wireless services to low-income urban consumers [Loc 97]. The low-cost
PACS would be a good solution for this user group.
The market research of PHS user profiles in Japan indicated that a typical PHS user is a
young male, well educated, and with an income well above the average [Ish 96]. The
PHS handheld is acquired basically for private use, while Japanese companies as a rule
provide cellular phones for their employees and pay the service charges. Fashionable
design of the handhelds and low service charges were the major factors to encourage
private use. Half of the PHS users had a PC of their own, which is more than twice the
average 20 % PC penetration in Japanese households. These interesting demographic
results suggest that the paradigm shift to low-tier wireless systems might be also a matter
of a new life style.
Even if we cannot draw to far-reaching conclusions about the PHS success in Japan, it is
clear that in densely populated areas there is a market gap for a low tier system with
roaming, handoff, and incoming call capability. There is, however, no guarantee that the
market for PACS or DECT would behave in similar manner in USA and Europe albeit
geographic and demographic conditions would be otherwise similar.
2.4 Market Outlook of Wireless Data and Internet Access
For the time being, the mobile data market is roughly only 5% of the total mobile
industries market. This figure is likely to grow rapidly in the near future. According to the
market forecasts of Giga Information Group[Blo 97], by year 2000 the number of US
mobile data users will increase from current 1 million to 9 million. The Web is widely
considered the killer application for wireless data. Currently the data transfer rates, available in various mobile networks, are fairly low and mostly inadequate for Web browsing.
According to recently published market research information, the number of mobile data
users has doubled in UK over the past 12 months. The Mobile Data Association projects
more than 100% annual growth over the next five years. The proliferation of notebook
computers together with the low cost of software based mobile data connectivity will
drive the market (Newsbytes, Jul 21, 1997).
The reason for the slow take-off of mobile data is a fragmented market due to lack of
common standards and application protocols. The situation will change in the near future
as the three leading manufacturers Motorola, Nokia, and Ericsson have decided to develop
a joint wireless application protocol standard WAP [Taa 97]. This will enable economies
of scale for development of advanced wireless applications. The WAP will be a mixture of
proprietary schemes developed by Unwired Planet, Nokia, and Ericsson.
The most appropriate wireless technology for Internet access is a packet switched one. A
user will be billed for the wireless link usage in proportion to the number of packets
transmitted and received. However, the packet switched mode does not suit well for realtime multimedia [Häm 96] due to long delays and large buffers needed for delay jitter
compensation. For voice-over-the-Web, the packet mode might be applicable, but hardly
for videoconferencing.
The US mobile data market has been dominated by proprietary systems such as ARDIS
and RAM Mobitex. Furthermore, a dedicated national standard for packet data CDPD
exists in USA. CDPD is an overlay technology of analogue AMPS, supporting packet
switched data up to 19.2 kbps. Because of the rapid evolution towards digital networks,
CDPD may become obsolete fairly quickly. Even if the roll-out for CDPD has been very
slow, its market in USA is growing steadily due to good coverage (39 out of 50
metropolitan areas in US), Internet access, and good availability of CDPD modems from
several vendors[Brod 96]. The CDPD competitor, digital cellular data is plagued by
different standards, poor availability and limited coverage. CDPD being an overlay
technology of analogue AMPS, there is no market segment for such a data service in
Europe and Japan.
The data speeds of all above mentioned networks are significantly lower than those
available in the fixed network. In PSTN, where widely used V.34 modems offer 28.8 kbps
(V.34 upgrade V.34Q operates up to 33.6 kbps) and now asymmetric modems support
bit-rates up to 56 kbps downstream. In ISDN, an access rate of 128 kbps is available. In
wireless networks, the BER of a raw wireless data is typically around 10-2 - 10-3, which is
entirely insufficient for most services. This implies that error recovery in some form or
another is necessary to achieve adequate QoS and unfortunately at the expense of
additional overhead.
Given that nomadic users are not willing to bargain on performance of Internet and Web
applications in regard to what they have been used to on a low bit-rate wireline connection, there is a huge need to increase bandwidth for cellular data communication. Channel
aggregation technologies will increase the available current 9.6 kbit/s data rate up to 64
kbps. For instance in a TDMA frame, several timeslots can be concatenated to set up one
high speed multiple link. In GSM Phase 2+, the aggregation mechanism bears notation
HSCSD. Also a packet switched mode GPRS is being standardized [ETS96b],[Häm 96].
HSCSD will be launched very soon whereas the roll-out of GPRS may take 1-2 years
more. Similar enhancements are to be included in IS-54 (TDMA based US Digital Cellular
standard)[Hoo 96] and probably also for IS-95 (CDMA based US cellular standard). In
addition to narrowband CDMA, also wideband CDMA with data rates up to 256 kbps is
under development [Gar 96] and both circuit switched and connection oriented packet
switched services are being planned. The deployment of these services is not likely to take
place in the near and medium term.
In mobile satellite networks, data transfer rates are even lower than in cellular networks
[Wil 96]. The ambitious Teledesic project [Sav 96], [Stu 96] suggests a dramatic change
by offering data rates up to 2 Mbit/s, which enable the use of high quality multimedia
applications. The roll-out is scheduled to take place in 2002, but the high risks both in
terms of the market and technology may delay the start-up.
Cordless networks are capable of supporting better the performance levels available in
PSTN than the cellular ones. In PHS, a 14.4 kbps data service has been available for some
time and in Spring 1997 a full 32 kbps service will be opened by all Japanese PHS
operators [Har 96]. It is likely that a channel aggregation scheme will be included in the
standard as well to raise the data rate in 32 kbps multiples. Japan has a leading edge to
launch wireless access to Internet based multimedia applications.
2.5 Semiconductor Market Trends
The semiconductor market has exploded during the past years from $ 30 bn to $150 bn
[Mak 96]. The average growth rate has been 15% in the nineties. The market size in year
2000 is predicted to approach $300 bn. The key building blocks for portable multimedia
appliances are: low power consuming and low-cost chips, in particular such as RISC
processors, microcontrollers (MCU), field programmable signal processors and gate
arrays as well as MMICs.
2.5.1 CPU Chips
RISC processor architecture is particularly suitable for lightweight portable intelligent
appliances, which exert special emphasis on low cost and low power consumption. Due to
these reasons, a bright future is envisioned for RISC processor as a workhorse for the
general purpose computing in next generation portable smart appliances. The cost of
RISC processing power lies currently within the range of 1-5 MIPS/$ and it is expected to
reach 10 MIPS/$ by the end of the millennium [Mak 96].
2.5.2 Memory Chips
Like in any intelligent electronic device, memory chips are key component of the future
information appliances, in particular nonvolatile memories with very low power
consumption. DRAMs form he core of the CPU memory. The size of DRAMs has grown
enormously during the past twenty years. A DRAM of 1 Gb is expected to be available
around the year 2000 [Mak 96]. For mass storage, nonvolatile FLASH memories with
automatic sleep mode for saving power in an inactive state are much more suitable than
power-hungry hard-disks. The latter ones have a huge price advantage of tens of times in
cost ($/Mbyte). However, if we compare the price ($/Mbytes) of more expensive
miniature disk-drives intended for PDAs and handheld computers, the price gap is not so
wide anymore. Given that the predicted rapid expansion of the FLASH market will fuel
price reduction, FLASH is becoming also a competitive alternative for mass storage
device of portable intelligent appliances. Benefits of the low power consumption and
resilience to environmental stress factors justify a higher price for FLASH to stay at the
competitive edge.
Unlike conventional EEPROM’s, a significant advantage of FLASH memories is their
reprogrammability. Since SW updating cycles are becoming shorter and it is easy to
download patches or additional plug-ins over the air interface from the Web, it is apparent
that the popularity of FLASH EEPROMS will increase sharply in portable information
appliances. This prediction is not so far-fetched, because currently cellular phones
consume over 40% of the total $ 3.5 bn market [Cra 97]. The projected annual growth is
healthy 25% in the next few years.
Besides, FLASH memories, FRAM, a new non-volatile semiconductor memory
technology has emerged into the market. Its market share is negligible, but the potential is
high, particularly in portable devices, since it consumes less power and can be powered
from a single low-voltage battery source. The endurance of the reprogrammability was
initially a problem, which has been currently overcome. They have one downside as well,
namely reading a FRAM is destructive to its contents. Therefore, after every reading
cycle, the stored data has to be reloaded in the memory. For the time being, no market
forecasts are available for FRAMs.
2.5.3 Digital Signal Processor (DSP) and Programmable Logic Chips
DSPs are key components of current mobile phones. They have been used for speech
processing, delay spread equalization, and echo cancellation. DSPs and FPGAs) are partly
competing and partly complementary technologies. The market volume of signal processors embedded in portable battery-powered devices has not been publicized, but the
total DSP market volume was $1.7 bn in 1995 and in 1996 around $2.2 bn [Ana97]. The
predicted size of the market in year 2000 is $ 9.1 bn.
Besides DSPs, FPGAs are predicted to play important role in future portable information
appliances. Recent advances in this technology enable instant reconfiguration of same
basic set of HW to rapid execution of specific tasks. Hence, you can use same circuitry in
sequential order for a number of different purposes requiring high performance. Field
programmability enables also rapid response to market needs and flexibility to
accommodate future upgrades.
Typical tasks fit for FPGA are complex digital coding such as encryption, channel coding,
bit interleaving, and pattern recognition, in particular image and handwriting recognition.
[Vil 97]. The FPGA approach is particularly important in mobile computing environments
where minimizing power consumption is essential. General purpose processor chips
cannot offer same performance in execution of dedicated computational tasks with
stringent real-time requirements. In 1996 the size of FPGA market in USA was around
$1.5 bn with an annual growth of 20% [PACE97], but a higher growth is expected over
the next few years.
2.5.4 Monolithic Microwave Integrated Circuits (MMIC)
Another strategic component for the future wireless information appliances is a MMIC,
monolithic microwave integrated circuit. These Gallium-Arsenide (GaAs) or silicon based
chips are needed for multi-mode wireless terminals. Recent market forecasts predict
explosive growth for MMIC chips, the production of which is now well under control with
a good yield. They are essential also for the future satellite systems such as Teledesic. The
multi-mode MMICs enable wireless terminals to support air interfaces of different
standards in a cost-effective manner. In USA, such terminals with multi-mode capability
are a must to achieve a nationwide coverage. This holds true also for terminals with both
good indoors and outdoors operation. The current market volume of MMICs used in
wireless terminals is rather low. The market forecast made by Allied Business Intelligence
predicts that the number of shipped dual-mode MMIC chips is 26.6 million in year 2000
[EBT 97]. As these chips tend to be more expensive, the figures translates into a market
value of $ 2-3 bn.
2.6 Market Outlook on Batteries
Probably the most critical hardware component of a portable device is the battery, since
battery life in regard to stand-by and active operation time is a crucial issue for the overall
usability. Regardless of huge efforts to develop more efficient battery technologies, the
progress has been rather slow compared to other core technologies of intelligent portable
electronic appliances. However, during the last 2-3 years the progress has been quite good
due to rapid growth of notebook computer market, which has boosted the market of Liion technology despite its moderately high cost. Now Li-ion batteries threaten the
dominance of Nickel metal hybrid (NiMH) batteries, which are commonly used in mobile
phones [Smi 97]. There are two versions of Li-Ion technology depending on the
electrolyte. The liquid Li-Ion version is not considered suitable enough for portable
devices, because of inadequate safety, heavy weight, and cost (a rigid metal housing is
necessary). The solid state versions, based on a polymer electrolyte, are safer, non-toxic,
and cannot leak. During the next few years an explosive growth is expected for
rechargeable, high performance batteries, which currently make only 10% of total battery
market ($ 27 bn). Gradually this growth is likely to accelerate significantly also the
technological development.
The market of smart batteries, which regulate their recharging without external circuitry,
is expanding constantly. However, no break-through is discernible, which would enable
significantly higher capacity at a lower price. Therefore, the insatiable need for low power
hardware still exists and will continue also in the future.
Recharging of the batteries is a nuisance to the user, and the bigger, the shorter the standby time between recharging cycles is. A truly portable information appliance should not
depend on the availability of mains power. So far a low cost battery recharger, which
utilizes human kinetic energy, is not available.
The following Figure 2 is a synthesis of various core technology market forecasts.
Sources: Electronic Business Today, Dataquest,
Analog Devices, Pace Technologies
20
18
16
12
1996
10
2000
8
6
4
Batteries
FPGAs
DSPs
MCUs
0
FLASH
memories
2
RISC
prosessors
$bn
14
Figure 2 Markets of core technologies for portable smart appliances
3. BRIEF HISTORY OF PERSONAL COMMUNICATIONS
This section aims at reviewing in brief the evolution of wireless communications and use
this information as input for future scenarios.
3.1 Early Phase of Evolution
In the history of personal communication we can distinguish several phases. If we
conceive the word personal in this context as the ability to communicate anywhere any
time across wireless links using a terminal dedicated to personal use only, the first phase
took place in the early eighties when first wide area analog cellular networks were
launched in Scandinavia based on NMT regional standards. A bit later, the launch of
cellular TACS services took place in UK. Despite the fact that cellular technology was
developed in the seventies by AT&T Bell labs, USA did not launch AMPS services until
1983 [Pau 95] when FCC allocated the frequency bands for AMPS. At that point of time,
the cellular phone was more or less permanently mounted into a vehicle and it is debatable,
whether such terminals completely fulfilled the nature of a truly personal communication.
There are still a lot of mobile phones permanently mounted in vehicles. In this case it more
appropriate to speak of vehicular communications. Not until 1986 did the cellular industry
enter the business in earnest. Now there are more than 400 carriers operation around 1500
cellular systems in USA [Pau 95].
In Scandinavia, the common NMT standard and open market of mobile stations and
network equipment boosted the evolution of NMT. The market forecasts were briskly
exceeded and the analysts had to readjust their predictions over and over again.
Also other analogue systems such as system C in Germany were deployed in Europe in the
early eighties based on national standards. The market remained closed, which kept
service and equipment cost high and no similar healthy growth, experienced in
Scandinavia, took place.
3.2 Second Phase of Evolution: Dawn of Personal Communications
In the second phase, in the late eighties, lightweight handhelds were introduced and at that
point of time the mobile phone was adopted in strictly personal use. New chipsets and
more advanced technologies enabled downsizing the terminal. The usability of first pocket
size phones was restricted by a 1 hr talk-time and less than 24 hours stand-by time. Those
mobile phones required constant recharging. At that time, a special cradle mounted in a
car with an automatic recharging capability became very popular, which it still is. The first
modems for mobile data were introduced. The coverage of the analogue cellular in
Scandinavia and UK reached almost 100%. In the late eighties the first digital cordless
CT2 phones made their debut into the UK market, but the endeavor resulted in a complete
failure. The cordless networks did not support routing of incoming calls, which turned out
fatal. Mobile communications was not after all plain sailing if user needs were not met.
3.3 The 3rd Phase of Evolution: Digital Cellular
Deployment of digital cellular networks started in 1992 [Udd 95]. By 1993 there were 36
GSM networks in 22 countries [Pau 95]. The European GSM standard began to spread
also into other continents such as Asia and Australia. Digital systems offered better speech
quality and a wide
range of functionality such as call forwarding, voice mail, call completion and number
identification services. Since the launch of GSM, 153 mobile systems has been launched in
service in 91 countries around the world [Ber 96]. GSM subscriber base is currently
approximately 25 million.
The Japanese PDC (Personal or Pacific Digital Cellular) was launched a bit later. Unlike
GSM, no other country except Japan has adopted PDC. The number of cellular phones,
including analogue and digital systems, was 15.3 million in September 1996 [Har 96] with
a monthly growth of 800000 subscribers. By the end of 1995, the number of analogue
cellular phones was roughly 4,8 million [Ish 96]. The total number of cellular phone users
is now around 21 million. Assuming that the growth has been larger for PDC, we derive
from the above calculations for PDC a figure of approximately 14 million.
In USA the roll-out of GSM based PCS 1900 digital cellular system took place in 1995 by
American Personal Communications in Washington D.C. All frequency blocks for digital
cellular were auctioned off in 1996. Now a full-fledged roll-out of all three digital PCS
systems, based on GSM and US standards IS-54 (North American TDMA, i.e. D-AMPS)
and IS-95 (North American CDMA), is underway.
Besides cellular phones, also other portable appliances serving personal data processing
needs were introduces. The laptop and notebook PCs have all gained a substantial rapidly
growing market. However PDA, the other intelligent device for less demanding personal
information processing and management, did not become a success story after their launch
in the early nineties.
Mobile communication in Scandinavia and many other European countries differs
significantly by nature from what is typical of the US wireless communications market. In
Europe the mobile phone is visible, usually attached to a the user’s belt. The overall call
density and duration are considerably higher than in USA. The mobile phone is distinctly a
means of satisfying everyday personal communication needs of the user. Therefore, the
usage of mobile phones reflects a different lifestyle than in USA, where users keep their
mobile phones hidden in their pockets, often with power turned off. The results of CTIA
year-end 1996 user market studies indicate that 56% of the cellular subscribers use their
mobile phone for outgoing calls only, whereas for PCS subscribers the figure is 43%.
These results suggest that an average American cellular phone user has acquired it mainly
for personal safety reasons. It duly turned out from the user CTIA study that 46% of the
users purchased the mobile phone for being able to communicate in an emergency and
more than 30% had used it in emergency situations [CTIA].
Since their introduction cellular telephones have evolved into highly sophisticated and
intelligent products with processing power of hundreds of MIPS. The size, weight and
power consumption have declined steadily. However, some physical constraints still
remain that cannot be disregarded. The moderately high transmitting RF power and
computationally intensive signal processing, resulting from high system complexity,
consume plenty of battery power, which we can reduce to a limited extent only. In
contrast to other core technologies of mobile communications, battery technology has
made rather slow progress [Cox 95] as we have noted in the previous Section. In
particular, efficient battery technologies such as Lithium-ion technology tend to be too
expensive. Sophisticated power saving software has played an important role in cutting
down the power consumption.
Now we are on the verge of next phase of personal communications, which is characterized by advanced data communication capabilities and new services. Furthermore, mobile
communications is penetrating into new, yet unexploited markets, It is very likely that
these trends will change the existing paradigm of mobile communications in a profound
manner.
The vision of ubiquitous computing fathered by Mark Weiser, is becoming true in the
personal space. Mobile systems will be split into a number of intelligent appliances, each
accomplishing specific tasks. The devices will be interconnected over a PAN, personal
area network in the future.
4. OUTLOOK ON DIGITAL WIRELESS
COMMUNICATION
In this section we will handle very briefly the evolution of digital mobile communications
and some underlying key technologies particularly in regard to low bit-rate multimedia
applications. We have restricted our studies on public digital networks only. Albeit analog
networks support data transmission, it is unlikely that those capabilities would ever be
used for multimedia communications. Therefore, we focus only on digital systems, which
include cellular, cordless and satellite networks.
4.1 Overview on Existing Wireless Systems
Currently no single wireless technology exists, which would be fit for diverse operational
conditions. In the one end we have satellite systems as wide coverage high-tier systems
and in the other end the low-tier, limited coverage, low mobility cordless systems. Cellular
systems fall between these two extremes. There is a market gap for all of these and rather
than being rivals they complement each other. The satellite is a cost effective way of
offering mobile services to large fairly sparsely populated geographical areas, whereas cellular is ideal for vehicular operation in more densely populated areas. Satellite has also the
advantage of global coverage, which make it an ideal solution for a world traveler. Both
the satellite and the cellular systems do not operate reliably in indoor environments. The
low-tier systems fill this gap and furthermore, they can be used very cost effectively
outdoors as well, in limited urban areas, and in shopping malls based on a microcell
architecture and low-power basestations, which allow handoff to relatively slowly moving
users. [Cox 95], [Mad 96], [Noe 96]. These technologies are foreseen to merge in such
manner that user can access wireless services anytime, anywhere at a reasonable cost both
in terms of enduser equipment and service charges.
4.1.1 Satellite and Other High Altitude Systems
Only a minor part of the existing satellite systems are mobile satellite systems dedicated to
personal communications. For instance, Inmarsat has offered for maritime users and world
travelers digital phone and data services for a long time over geostationary satellites.
These services require expensive transceivers with an antenna of less convenient size.
Therefore, they do not meet the characteristics of personal communication services in their
broad meaning i.e. to be fit for an ordinary consumer. In order to rival the rapidly evolving
terrestrial systems, satellite technology needs to find new market segments and
overwhelming competitive factors such as global connectivity. Unfortunately, in the past,
the excellent coverage had been shadowed by inferior QoS resulting from long
transmission delays. New satellite technology, characterized by low-earth orbit satellites,
low-cost handheld terminals and high speed data transfer capabilities, is about to challenge
the leading edge of terrestrial wireless systems.
The satellite systems for personal communications are moving from conventional
geostationary orbit satellites (GEO) towards novel low earth orbit (LEO) and intermediate
circular orbit (ICO) satellites. GEO satellites incur lowest overall cost including space
segment, terrestrial gateways, and satellite system. Their operational complexity is
simplest and no hand-over is required due to a large spot beam. They have some
downsides as well and the worst of all is the long delay of a satellite hop amounting to a
round-trip delay of more than 0,5 seconds, which severely impairs human interaction as
well as interactive transfer of data. Also the overall system capacity is very low. Therefore,
there is a business opportunity for ICO and LEO based personal satellite communications.
The LEO and ICO systems are capable of serving large number of users and the round-trip
delay is significantly lower than that of GEO systems. Since low power is a must for the
return link from handhelds, link margin is bound to remain low, which translates into poor
indoor operation.
4.1.2 Digital Cellular Systems
Current digital cellular systems provide a wide coverage wireless connection to PSTN.
The mobile phone services dominate the usage, but both analogue and digital cellular
networks support also data transmission, but as a rule up to speeds of no more than 9.6
kbps. The role of mobile data is still fairly modest, but it is increasing rapidly due to
widespread deployment of mobile computing applications. The GSM architecture is
presented in Fig. 3. The basestation controller BSC is a complex and expensive system
entity, and therefore it has been separated from the basestation BTS. One controller,
serving a group of BTSs, transcodes the GSM (RELP-LTP) speech signals into 64 kbps
speech to be switched through the digital MSC to PSTN.
HLR
BTS
Abis interface
VLR
SS7
A interface
BSC
AUC
MSC
PSTN
ISDN
PSTN
Data Networks
BTS
OMC
MS
HLR: Home Location Register
VLR: Visiting location Register
AUC: Authentication Center
BTS: Base Transceiver Station
BSC: Base Station Controller
MSC: Mobile Service Switching Center OMC:
Operations and Maintenance Center
Figure 3 GSM architecture [Rap 96]
There are different technologies for the air interface competing with each other. Currently
the dominant access technologies are TDMA and CDMA. TDMA system allocates a
cyclically repeating timeslot for each user in a predetermined sequence of data called a
frame. In CDMA the payload data is multiplied by a very large bandwidth spreading
signal. All users share the same carrier simultaneously and they are distinguished by a
pseudo-random code unique to each endpoint. Therefore, all other generated codewords
appear as noise.
As a rule both TDMA and CDMA based systems use different frequency bands and
carriers for the forward and reverse links. The maximum capacity of cellular system is an
important design constraint in densely populated high-traffic areas. The transmitted signal
is accessible only within a small geographic area called a cell, and the same frequency can
be reused in another cell located at some distance away. If a user moves from one cell to
another a handoff takes place i.e. the call will be switched to another basestation. The signal power is measured constantly and the decision is taken in accordance with the adopted
handoff strategy and signal threshold level. The handoff is seamless, which means that it is
imperceptible to the user. The size of a cell is usually several kilometers in diameter.
Signal power control is the key to efficient frequency reuse and good overall QoS
management.
The following Table 2. Contains some basic data of the existing digital cellular standards.
The CDMA is the most efficient system in terms of radio spectrum utilization. However,
huge traffic loads entail degradation of quality, because interference level will increase in
proportion to the number of users sharing the same bandwidth. Wideband CDMA,
offering enhanced data transfer capabilities comparable to aggregated multiple channel
TDMA, is under planning. In America, derivatives of GSM and IS-54, PCS 1900 and PCS
2000 employ the same frequency blocks as CDMA.
Table 2 Comparison of wireless system parameters [Gar 96],[Rap 97]
Characteristics/Wireless
System
Region
Optimized target environment
Multiple Access/Duplexing
Frequency band (MHz)
Slots/frame (channels/carrier)
Number of channels
GSM
IS-54
IS-95
PDC
Global
outdoors
TDMA/FDM
A
FDD
890-915 [R]
935-960 [T]
USA
outdoors
TDMA/FDM
A
FDD
824-849 [R]
869-894 [T]
USA
outdoors
CDMA/FDM
A
FDD
1850-1910
[R]
1930-1990
[T]
8
1000
3
2500
NA
4000
Japan
outdoors
TDMA/FDM
A
FDD
810-830
&
1429-1453
[R],
935-960
&
1477-1501[T]
3
3000
Modulation data rate(kbps)
Carrier spacing (kHz)
Spectral efficiency (bps/Hz)
Speech coding
270.833
200
1.35
RELP-LTP
@ 13 kbps
EFR
Speech quality (MOS)
3.54/4.0
Transmitter power of port- 125
ables (mW) Max. avg.
Traffic Erlang/sq.km
27.7
Channel coding
Cyclic (CRC)
&
convolutional
Channel equalization
Adaptive
Interleaving delay (ms)
40
End-to-end speech delay
90
48.6
30
1.62
VSELP
@ 7.95 kbps
3.6
100
1288
50
2.58
QCELP
@ 9.6 kbps/
@ 14.4 kbps
3.45/4.2
200
41
65
Cyclic (CRC) NA
&
convolutional
Adaptive
Adaptive
50
110
42
25
1.68
VSELP
@ 6.7 kbps
3.2
125
50
Cyclic (CRC)
&
convolutional
Adaptive
27
80
PSTN is the most important one among interfaces to the fixed network, and different
interfaces are needed for speech and data. As a rule, the speech is routed from the mobile
network to PSTN across a E1 or T1 interface of a PCM system (4-wire cross connect),
which means that speech is transcoded in accordance with A-law or µ-law into 64/56 kbps
G.711 speech.
Two options are available for data. Either the terminal has a voice-band modem or the
data is transmitted in a baseband mode. The output of a voice band modem is converted
into a digital data stream and sent over the air interface. A baseband data generates a
digital output, which is converted into a 56/64 kbps T1 or E1 channel. In the other end of
routed to PSTN across a modem pool, which is located in the MSC. Current digital air
interfaces restrict data rate to 9.6 kbps. Channel aggregation schemes are now being
standardized for all major cellular technologies to increase the data rate. The aim is to
minimize potential ramifications on the current network interfaces. The multi-link
operation is described in more detail in Section 4.2.4.
Bit error rates of, say 10-2 to 10-3 are typical of a radio channel. Furthermore, the errors
tend to appear in bursts, which would induce severe artifacts without appropriate counter
measures. The needed error detection and correction scheme is rather sophisticated.
Instead of sending the bits in sequential order, the source bits are permuted by a process
called bit-interleaving. Thus adjacent bits are spread in time to deal with deep fades or
noise bursts. Interleaving allows the use of error control coding (channel coding) to
correct the errors [Rap 96]. Another serious source of impairments is multipath fading,
which results in intersymbol interference due to time dispersed nature of received radio
signals. Multipath fading requires sophisticated channel equalization technology in
conjunction with so called diversity technologies. The latter ones constitute a simple yet
powerful means to reduce impairments of fading channel for instance by using additional
antennae at the basestation.
The radio frequencies constitute a limited natural resource, which needs to be exploited as
effectively as possible. Therefore, the current 25 kHz channel spacing (bandwidth) has
been gradually reduced by virtue of novel technology. Another option for more effective
exploitation of bandwidth is using technologies such as CDMA for the radio interface. The
capacity increase is however a trade-off between system complexity and cost. The reuse
factor of cellular system is constrained by co-channel and adjacent channel interference.
Furthermore, diminishing the cell size and reducing the transmitting power is possible in a
limited scale only, because of increase of hand-offs. This would incur excessive overhead
in the form of intersystem signaling. With the aid of subtle power control, the frequency
reuse factor of TDMA systems can be increased reducing the gap to CDMA in terms of
spectral efficiency. The advantage of CDMA is constrained by increased noise level under
heavy traffic conditions
The characteristic features of cellular system are:
• different frequency bands for up-link and down-link (FDMA)
• wide delay spread of multi-path propagation due to moderately large cell size and high
transmitting power
• high complexity and cost of base stations
• complex and power consuming signal processing needed for speech and channel
coding, channel equalization and bit-interleaving
• long propagation delay due to bit-interleaving, channel coding and equalization
For the moment, there is no single global standard available for digital cellular systems. In
Europe the shift from regional analog systems resulted in pan-European common standard
GSM, which has been adopted beyond Europe as well, among others in Australia, Near
East and India altogether in more than 90 countries. In USA the evolution has taken a
reverse course in the sense that three digital regional standards have been introduced as
heirs of the Pan-American analog AMPS system. A full-fledged roll-out of GSM based
PCS 1900 as well as IS-54 and IS-95 based PCS 2000 networks is underway.
The evolution path of US PCS networks is voice communication oriented as is the case in
other countries deploying digital wireless communications. Of the 50 million mobile phone
user population (CTIA, Aug -97) less than 1 million are mobile data users. Basically,
mobile data has not taken off. In Europe, the market research studies indicate a slightly
higher figure.
In Japan PDC (known also as JDC) is the common regional standard of a TDMA based
digital cellular system, which has not yet been adopted by the other Far East countries.
The amount of PDC phones was 80510000 at the end of 1995 [Ish 96] with growth rate
of 41,1%. It is likely that installed base is now around 11 million. The rapid growth and
envisioned shortage of PDC frequencies has spurred the Japanese to expedite the
standardization of the 3rd generation system FPLMTS, currently renamed IMT2000.
4.1.3 Low-Tier Systems
Low-tier systems include micro or pico cellular low-power mobile systems, which operate
on limited coverage areas. The System architecture of PACS is depicted in Fig. 4.
Currently various cordless telephone systems such as CT2, DECT, PHS and PACS
constitute the main group of low-tier systems.
Subscriberun
it (SU)
A-Interface
P-Interface
C-Interface(s)
Operations &
Management
center
CGeneric
Radio Port 1
Radio Port
Control Unit
Radio Port 2
Fixed subscriber unit
of wireless
local loop
AM
Local
switch or
PBX
CSW
SS7
to CSN
HLR/
VLR
•
•
•
SS7
Radio Port n
Radio Port
Control Unit
Access
Manager
(AM)
CMA
Telepoint
SS7=signaling system n:o 7
CSN=circuit switched network
Figure 4 PACS System Architecture
HLR=home location register
VLR=visitor location register
to CSN
HLR/
VLR
Unlike PACS, CT2, DECT and PHS are mainly air interface standards, which leave many
value-added system features open to proprietary implementations [YuC97b]. A huge
amount of work remains to be done, before they can measure up GSM.
In the past cordless systems supported only outgoing call capability without any hand-off
and roaming. Currently most of the cordless systems support also reception of incoming
calls with hand-off and roaming, which imply that the distinction from macrocellular hightier systems is based on other factors listed as follows:
• Low-tier systems provide wireless services within a limited coverage area
• Support low mobility from a few mph to 70 mph [Noe 96]
• Employ radio ports i.e. basestations of low complexity, cost and short coverage range
(radius < 400 m)
• Enable the use of light-weight, simple and cheap handsets with excellent speech
quality, low transmitted RF power, and low battery power consumption.
They can be used
• as a cordless extension of wireline subscriber line or even as a wireless local loop,
• outdoors in densely populated urban environments, such as shopping malls, railway
station etc. public places (Telepoint application),
• in office buildings with weak macrocellular coverage and
• as cordless Centrex or PBX extensions.
They offer a cost-effective way to fill gaps and dips in the coverage area of a macrocellular
system [O’Sh 96]. Furthermore, PACS and PHS support aggregation of multiple radio
links or subchannels based circuit for high speed circuit and packet switched data as well
as messaging services [YuC97b]. Regardless of this versatility and many good features,
they have made only limited success compared to the macrocellular networks, except in
Japan. There is, however, no doubt that the growing demand of high speed data will
leverage the low-tier system market. Another reason, which may give a strong thrust to
low-tier systems is the growing doubt that the current transmitter power levels of cellular
and satellite systems raise the risk of various health problems.
The TDD based air interface, used in the unlicensed PACS, reserves two timeslots per
call, one for forward link and the other one for the reversed link of a TDMA frame. Bursts
of data associated with each TDMA frame are sent repeatedly in forward and reversed
directions, one at a time by using same radio frequency. The scheme is also called “pingpong”. Low transmitting power results in short delay spread. Therefore, we can use very
simple channel equalization technology. The basic 32 kbps data transfer rate of a radio
channel suits better for multimedia and other data communication.
Basic data of the three major regional standards for low-tier systems PACS, DECT and
PHS is presented in Table 3. The alternative data concerns PACS-UB, which is the
unlicensed access.
The Radio Port Control Unit transcodes 32 kbps ADPCM coding into or 64 or 56 kbps
G.711 speech. In case we use the 32 kbps channel for multimedia data (e.g. H.324/M),
this is indicated in the setup message. The controller strips off redundant MAC layer data
blocks and stuffs the residual bits into 64/56 kbps channels. The inverse multiplexing of
aggregated channels takes place in a gateway located in the local switch. Local switch
routs the data to a modem pool, ISDN or a data network.
Table 3 Comparison of standardized low-tier mobile systems [Gar 96],[Rap 97],[Noe
96]
Wireless System
DECT
PHS
PACS
Region
Optimized target
environment
Multiple Access/
Duplexing
Europe
indoors
Japan
outdoors
USA
outdoors
TDMA/FDM
A/TDD
TDMA/FDM
A/TDD
TDMA/FDM
A/FDD
Frequency band (MHz)
1880-1900
1895-1918
Number of carriers
Slots/frame
(channels/carrier)
Number of channels
Channel bit-rate (kbps)
Speech coding
10
12
77
4
TDMA/FDM
A/FDD or
TDD
1850-1910
[R]
1930-1990
[T]or 19201930 (PACSUB)
400 or 32
8 or 4
120
1152
32 kbps
ADPCM
4.1
10/250
308
384
32 kbps
ADPCM
4.1
10/80
3200 or 128
384
32 kbps
ADPCM
4.1
25/100
1000
270.833
13 kbps
RELP-LTP
3.5 (EFR 4.0)
125/1000
Cyclic (CRC)
Cyclic (CRC)
Cyclic (CRC)
Hand-over
seamless
seamless
Channel equalization
Frame duration (ms)
Max. radio port or base
station range (km)
End-to-end speech
delay(ms)
User speed (km/h)
None
10
0.1
1s
interruption
None
5
0.15
CRC and
convolutional
seamless
None
2.5 or 2.0
0.4
Adaptive
4.62
6
23
13
9
90
5
50
100
200
Speech quality (MOS)
Transmitter power of
portables (mW)
avg./peak
Channel coding
4.1.4 Dedicated Data Networks
Typical hightier (GSM)
Europe
outdoors
890-915 [R],
935-960 [T]
125
8
The previously mentioned ARDIS (Motorola) and RAM MOBITEX (Ericsson) support
low bit-rate data only ranging from 4.8 kbps to 8 kbps, which do not meet current
demands of many applications. The merit of these proprietary schemes is close to full
nationwide coverage in USA. Based on upgrades of a new RD-LAP protocol, ARDIS is
now capable of supporting 19.2 kbps data rate [Rap 96]. For the time being, the
availability of the upgraded capability is limited.
CDPD is gaining rapidly larger share of the market and the coverage is improving as well.
CDPD supports packet data up to 19.2 kbps. CDPD is, however, an interim technology,
which is expected to be superseded by packet radio overlay technologies of IS-54 and IS95 within a few years. Therefore, the long term prospects of CDPD are less good, because
the demand for higher data rates is clearly indicated and the new emerging digital wireless
data technology has a competitive edge in this respect. In the short and medium term, the
prospects of CDPD are good due to the wide coverage and good availability of CDPD
products.
4.2 Evolution towards 3rd Generation Systems
In this section we deal with some design considerations and trend towards the 3rd
generation wireless networks. The 3rd generation network concepts are FPLMTS,
currently renamed IMT 2000 and UMTS. Standardization work for IMT 2000 is
underway in ITU-R TG8/1 and for UMTS in ETSI. The current digital cellular and
cordless networks represent 2nd generation wireless networks. Of satellite systems the
previously mentioned Teledesic can be classified as 3rd generation satellite technology by
its wideband digital capabilities. Wireless ATM, which is strongly bound to the evolution
of wireline ATM, is considered mainly a wideband wireless access technology for indoor
environments. For this reasons, it falls out of our scope.
4.2.1 Potential Threats to Wireless Communications
Some researchers [Fir 96 ] claim that even the relatively low transmitting power of
existing wireless handhelds is harmful to the human body. In particular, doubts have been
expressed that continuous exposure of the human brain to the radiation of an antenna
transmitting digital data at high frequencies may cause hemorrhages and cancers, harmful
syndromes in the nervous system, genetic damages, and reproduction abnormalities [Fir
96]. These health hazards are a widely argued issue that need very extensive statistical
analyses with large sample and reference groups to proof convincingly that using a
wireless phone is a health risk.
The 1996 issued FCC safety standard permits a power density ranging from 533 to 1000
µW/cm2 depending on the frequency, which according to [Fir 96] exceeds at least 10
million times of the radiation levels of earth surface (eg. broadcast radio and TV) and 10
billion times those of cosmic origin. Furthermore, the trend moving towards higher
frequencies means shorter wavelengths and higher risks. Digital cellular and most of the
forthcoming MSS satellite systems operate around 2 GHz band, and the stratospheric
systems of Sky Station International in the 47 GHz band (see Section 4.2.3).
A movement opposing to the increased amount of “electronic pollution” is getting more
and more air under its wings, in particular in USA. Whatever the outcome of the research
will be, the suspected health hazards of power levels of the current high-tier wireless
communications may become an additional factor to drive the evolution towards low-tier
systems. As we have noted in the subsequent Section 4.3, there are more clear-cut reasons
to drive the evolution towards low-tier systems.
4.2.2 Technical Design Objectives for 3rd Generation Systems
In the evolution towards 3rd generation systems, there are some very important
requirements that need to be met regardless of the technology. One of the perhaps critical
ones is the security issue. The cost of fraudulent usage is now growing much faster than
the revenues of telecommunication service providers [Fik 96]. By their nature, wireless
networks are much more vulnerable to frauds than their fixed counterparts. Therefore,
more stringent countermeasures are needed. Robert Fike stresses the significance of
international co-operation. The main issues are roaming clone prevention, authentication,
and subscription fraud control. In 1995 the estimated cost of frauds to the cellular industry
was $ 650 Million in USA [CTIA]. Therefore, fraudulent service usage is becoming a
large-scale problem, which needs more advanced counter measures such as authentication
procedures to keep it under control.
Internet and forthcoming interactive digital television have activated the need for high
speed asymmetric data transfer with high-speed reception capability. This capability has
not been addressed by current wireless networks. The technology for meeting those needs
is considerably cheaper and simpler than full-fledged 2-way high-speed communications.
Since the need is clearly indicated and the technology favors such capabilities, it is likely
that they will be introduced fairly soon in the terrestrial mobile systems as well. Wideband
downstream data on demand is the basis of LEO satellite based Teledesic [Stu 96].
On the way to a global standard, cellular, cordless, and satellite based systems need to be
integrated seamlessly into one functional entirety. Seamlessly means in this context that
during an ongoing call a user does not perceive any interruptions or impairments in QoS,
when shifting from one system to another. This implies that the appropriate user profile is
included in the roaming messages and the visited network is capable of supporting the
desired features.
Since the 3rd generation systems will encounter very tough competition from the existing
digital mobile systems, an evolutionary approach is more likely than a revolutionary one.
The key factors steering the evolution will be:
• seamless interoperability with the applications and services provided in the existing
wireless and wireline networks including the Internet,
• increased bandwidth, in particular downstream,
• improved security and new functional capabilities, which bring additional value to a
user and which are accomplished among other things by advanced IN technologies.
4.2.3 Non-Terrestrial Systems
As we noted in section 4.1.1, market share of personal communication satellites is
relatively small compared to terrestrial systems. Regardless of this fact, a number of
ambitious projects are underway and satellites intend to increase their market share
substantially. A brief summary of satellite projects appear in Table 4.
Table 4 Planned or ongoing satellite projects [Wil 96], [Nou 97], [Stu 96]
Proposed mobile satel- Number
lites for handhelds
satellites
Iridium
64
Globalstar
48
Ellipsat/Ellipso
24
of Orbit
LEO
LEO
LEO/ellip.
Date of operation
1998
1998-1989
1999
System
cost
$ bn
3.8
2.2
Not available
Odyssey
ICO-global
Teledesic
12
10
840
ICO
ICO
LEO
2000-2001
2000
2002
3.2
3.4
9
Aims of the ambitious Teledesic project are to provide fast downlink from Internet,
typically 2Mbit/s anywhere in the world. The cell size is 53 by 53 km. Teledesic satellites
render propagation delays comparable to fiber. Therefore, the Teledesic provides over
satellite similar service capabilities to those of ADSL on copper lines. The distinction from
the terrestrial systems is a universal access anywhere and anytime. Besides consumer
oriented services, Teledesic is capable of offering a broad spectrum of different data
communication services for the business/professional market [Stu 96]. Motorola has
unveiled recently their competing initiative for Teledesic, which bears the name Celestri
System. This development is a tangible indication that the wireless industry has strong
faith in satellite based wideband video and data communications [Sch 97].
Sky Station International has been granted by FCC a license in 47 GHz band to launch
digital narrowband and broadband services GSTS (Global Stratospheric
Telecommunication Service) to fixed or mobile stations from stationary platforms floating
above large population centers at an altitude of 13 miles (21 kilometers) [FCC 96a], [FCC
96b]. The stations are helium-filled Zeppelin-formed blimps weighing around 10 tons. The
services are scheduled to be launched year 2000. The service mix include wireless
telephone, videophone, data and Internet access with data rates ranging from 64 kbps to
2Mbps. The services include 64 kbps Internet access. The size of the required dish is only
5” in diameter. The high frequency band suggests that the services are targeted mainly to
business customers. The coverage of the spot beams ranges from 45 kilometers
(metropolitan areas) to 450 kilometers (rural areas). The company plans to launch 250 stations covering into US air space. This is an exciting new technology, which has no rivals
yet. Sky Station International claims significant cost benefits in regard to other nonterrestrial systems. The technology falls between wide area terrestrial systems and low-tier
local systems. If the equipment cost and service charges can be kept low enough this kind
of technology might boost mobile multimedia communications [Fer 97].
4.2.4 Upgrades of the 2nd Generation Terrestrial Networks
Currently the digital cellular systems are optimized for speech and the value-added
functions are overlays of wireless voice communications. In the future data traffic is likely
to increase rapidly, which will influence upgrading of the 2nd generation systems. Only
GSM is a mature well developed system. So far the new entrants IS-95 and IS-54 are not
yet much more than radio access technologies. Therefore, it is natural that GSM will be on
the leading edge in the forthcoming upgradings. ETSI has issued an extension of GSM
standard based on channel aggregation of circuit switched data [ETS96]. Similar actions
are underway in USA as well both for IS-54 [Hoo 96] and IS-95 [Emm 97].
There is an urgent need for increasing bandwidth of data communication in existing
cellular and cordless systems. The incentive is coming from PSTN, in which the upgrade
to V.34 modems has taken place very rapidly. Now introduction of asymmetric modems
will further increase the bandwidth up to 56 kbps. It is very likely that nomadic users will
require similar data transfer capabilities and QoS available in PSTN
In digital cellular networks the current limit is 9,6 kbps, which will be enhanced in the near
future by subsequently described channel aggregation technologies.
In Europe the development path to 3rd generation system from GSM goes through GSM
phase 2, which includes high-speed circuit switched and packet switched data services
[Ber 96],[Häm 96]. In GSM phase 2, the former one employs multi-link operation to
increase the overall access bit-rate (see Fig. 5).
MS
BTS
Radio interface
MSC
BSC/
TRAU
A-bis
interface
A interface
IWF
N full-rate timeslots
or subchannels per
TDMA frame
Multiplexing of
subchannels into a
64 kbps A interface
link
Figure 5 Architecture of GSM High Speed Circuit Switched Data Service [Häm 96]
The data stream is split into subchannels i.e. separate timeslots in a TDMA frame for
transmission over the radio link. The subchannels are aggregated on the link level by using
LAPB protocol in the receivers. The maximum bit-rate is limited by the number N of free
timeslots in the TDMA frame, which may be from 2 to 8. If the raw bit-rate of data is 16
kbps for each subchannel, four channels can be aggregated into one 64 kbps channel. The
HSCSD employs to modes of communication: transparent and non-transparent. The nontransparent one includes an ARQ with retransmission of corrupted bytes. This makes the
use of a pure ARQ based link protocol unfeasible for real-time multimedia applications,
since delays of the order 400 ms have been experienced due to retransmissions. Besides
impaired QoS, a large buffer is needed in the terminal to deal with the retransmitted data
blocks [Ham96].
The packet switched mode GPRS of GSM phase 2 employ IP and reduced channel coding
enabling a net bit rate of 14.4 kbps/timeslot. In theory, this translates into a maximum
overall data rate of 115.2 kbps. Respective enhanced packet switched data transmission
capabilities are under development for the US market as well. The TDMA Forum has
begun to standardize such a packet radio service for IS-54 based on Digital Packet Data
Specification 1.1 by embedding packets into a digital TDMA frame.[Hoo 96] in an overlay
mode. The adopted approach allows also higher data rates without hampering
interoperability with existing CDPD applications. Like GPRS, such upgrades are not likely
to be deployed in the near future, which means prolongation of the CDPD market. The
role of CDPD as market driver for the digital packet data is important.
The frequency bands for IMT-2000 (FPLMTS) have been allocated by ITU-R, albeit the
frequencies are currently occupied in some countries, among others in USA for PCS
networks. The standardization of IMT 2000 must be market driven in the sense that there
is a strong demand for new enhanced IMT-2000 services. Given the low mobile data
market volume the market thrust is too weak for the moment.
4.3 Feasibility for Supporting Real-Time Multimedia Applications
4.3.1 Delay Considerations
The upgraded second generation cellular systems are capable of supporting low bit-rate
multimedia communications, but their feasibility is another matter. Donald Cox has in his
baseline survey on various mobile systems [Cox 95], indicated that current high-tier
mobile system based evolution is an unfortunate course, which may seriously impede the
market growth of more advanced data services (the high-tier cellular systems are
characterized by attributes such as high velocity mobility, large cell size, high-power, high
complexity, and long delays).
The delay particularly impairs human-to-human interaction in conversational multimedia
applications. Latency and long round-trip delays are a difficult problem, in particularly
when real-time video is present. This stems from the fact that video coding delay of the
order 150-300 ms is added to the inherently long propagation delay of a digital mobile
link. The round-trip delay may rise up to 1 second or beyond, which is unacceptable from
QoS point of view. Even on non-real-time applications the long round-trip delay distracts
the operation, because of too long response times. For coding delay is considerably
shorter for speech, usually less than 50 ms. However, the delay of the video codec is
decisive in case lip synchronism is desired, because then additional delay has to be inserted
in the speech path. However, capability to disable the lip synchronism is essential to insure
fluid interaction.
4.3.2 HW Considerations
From the wireless multimedia terminal point of view, most of the available computing
power has to be sacrificed for heavy communication oriented signal processing and coding
instead of mobile multimedia computing. The situation improving, because of the rapid
progress of both signal processing and FPGA technologies, which is characterized by
voltage and power level reduction as well as higher degree of integration.
According to Texas Instruments release, the chip voltage will be reduced to 1 V and
power consumption to one fifteenth of the current 3.3 V chips in their next generation
0.18 micron technology.
As we noted in Section 2, FPGA is one of the core HW technologies for future portable
information appliances. The latest developments of FPGA chips enable reconfiguration in
less 100 µseconds and even higher speeds of reconfiguration are in sight. This opens
fantastic possibilities for logic arrays to accomplish a wide variety of different tasks on the
same HW platform, leading to both improved cost effectiveness and lower power
consumption. Together with MMICs, the advances of DSP and FPGA technologies pave
the way for dual or even triple mode wireless multimedia terminals at a reasonable
additional cost.
4.3.3 Cost and QoS Considerations
The cost of the precious air interface is substantial even for one channel. For aggregated
channels the cost will be multiplied. In low-tier networks the aggregation of two channels
makes up a 64 kbps overall bit-rate, whereas in GSM HSCSD we need 7 slots from one
frame to achieve the same rate. Whatever the pricing will be, the difference in cost is huge.
Unlike less cost sensitive business market, the consumers would not tolerate the increase
of cost. On the other hand business market tends to accept the higher cost, but is probably
much more sensitive to long delays than the consumer market.
The higher initial data transfer capacity of a low tier system enable higher overall
bandwidths by channel aggregation. This in turn translates into improved QoS and
capability to support a wider range of multimedia applications. In particular, ISDN 2B rate
is achievable by aggregation of 4 time slots (channels).
4.3.4 Comparison of High-Tier and Low-Tier Systems
For these reasons, there is no doubt that using aggregated multiple timeslots of a digital
cellular system, is a less attractive alternative for particularly real-time multimedia.
By contrast, the low-tier systems do not share many the above shortcomings, which make
them a logical choice for multimedia communications. There are several good arguments
for this point of view:
•
•
•
•
•
bandwidth, incremented in 32 kbps multiples by channel aggregation
low latency due to short system round-trip delay
low complexity, no channel equalization and echo cancellation needed
low power consumption due to simple construction and low transmitting power
lower cost of bandwidth
The limited coverage does not fulfill the fundamental design criteria stating that a nomadic
user should be able to access the services and applications anywhere and anytime from his
wireless multimedia information appliance. As a compromise, users who wish to have
wide coverage as well, may be provided a dual mode terminal with cellular speech or
limited multimedia capability only.
The simplicity of low-tier wireless access entails that most of the processing capacity and
battery power can be allocated for multimedia computing, user friendly interface
implementation, interoperability, and background processes. Besides the G.726 ADPCM
speech codec, interoperability with Internet requires an additional G.723.1 codec. The
standard video coding platforms needed are H.263 and H.261, pure SW implementations
of which are already available.
Digital cellular networks may become more attractive later on if and when the more
complex technologies become a commodity. In particular packet radio overlay modes,
such as GPRS for GSM with high throughput, meets well the needs of Internet and Web
applications. For conversational multimedia applications with speech we face same
fundamental problems as in Internet i.e. high latencies, excessive delay jitter and packet
drop-outs. The error-prone environment adds its own impairments to the soup making in
still more bitter, because packet radio protocols are optimized for elastic delay tolerant
applications. For instance, GPRS employs the IP and the MAC protocol includes an ARQ
[Ham 95], which makes GPRS less attractive for conversational applications such as Web
voice browsing. On the other hand one-way transmission of Web pages with multimedia
content seems feasible provided that we have enough buffering capacity available in the
terminal.
However, provisions should be taken in case future research comes up with convincing
evidence that current RF power levels of wireless networks increase health risks.
5. VIRTUAL MODEL OF PERSONAL MULTIMEDIA
COMMUNICATION SPACE
5.1 General
Wireless multimedia communications is under fairly intense study. This is reflected by
development of novel wireless data terminals and respective underlying technologies.
However, less attention is paid to the personal multimedia communication space in a
broader sense as seen from the user viewpoint. In this model personal multimedia
communication space is defined to encompass generic functionality and platforms for
supporting personalized voice + data applications adapted to the needs of an average
nomadic user (see Fig. 6). The Fig. 6 characterizes also the three realms related to our
investigation. In this context we are interested in what kind of elements and building
blocks are needed for our concept to meet the basic user and interworking needs. In the
first place, our conception of the user preferences are based on our expectations and
experiences obtained so far. Therefore, the model is virtual or hypothetical.
In our scenario of personal multimedia communication space consists of the following
building blocks:
• Personal user space, which is the private space of a pedestrian or vehicular user for
communication and accessing information residing in the Internet.
• Multimodal human-computer interface, which contains input and output devices for
controlling communications and other terminal functions as well as using available
applications, both distributed and stand-alone.
• Background processes such as digital voice recording, intelligent user agent, functions
of a personal organizer, electronic payment facility etc. Normally the background
processes are in a dormant state in the periphery, but a user can invoke any of them
into the foreground whenever he wishes.
• Voice and data applications with personalized information content
• Wireless information appliance i.e. a multimedia Walkman, with basic multimedia and
communication capabilities
Internet telephony
and multimedia
Personal space
Multimodal manmachine interface
Enhanced wireless
data (GSM/PCS/
PDC/PHS/PACS,
FPLMTS)
Personal mm
communication space
Three realms of study
Background processes
Background
processes
LBR voice
dataplatforms
applications
Access
tools+and
for
Mobile
multimedia
with personalized
content
multimedia
communications
computing and comWireless
multimedia
munication
terminal
information appliance
Characterization of personal
multimedia communication space
Figure 6 Three realms of study and personal multimedia communication space
5.2 Design Criteria
Given that our target users are ordinary consumers, who may have
• different needs and interests
• none or fairly limited experience of computer usage
• access to the Internet across different wireless networks
we have chosen the following design criteria for our model. To fulfill all these criteria may
imply a big technical challenge.
To serve well an ordinary consumer the concept should fulfill the following generic
criteria:
• flexibility to meet wide range of individual user needs and life styles i.e. individual
service profiles
• interoperability and salability of applications across networks boundaries
• capability to access personalized information content
• user friendliness in the sense that also a computer illiterate user can use the terminal
and access the services/applications he desires.
• light-weight portable terminal, capable of operating several hours a day with tens of
hours stand-by capability without being in the meantime frequently recharged from the
mains
• no significant impairment of QoS in regard to respective low bit-rate landline services/applications.
• support for self-configurable Web homepage and service/application management
through simple easy-to-learn procedures
• high degree of security against frauds and unauthorized usage
5.2.1 User Interface
User interface is one of the most critical components of a multimedia Walkman. In
particular the input device is difficult to implement. Recent advances in speech recognition
technology may provide useful means to design a user-friendly input device [Emm96].
Speech recognition can hardly replace a keyboard, which is essential for applications such
as e-mail. Instead of a full-sized QWERTY keyboard, a remote control unit with a limited
text editing capability may be used. Using the arrow keys for menu selections is a simple
solution, but it needs definitely some enhancements. Speech recognition with a speaker
dependent command set adds value to the remote controller. Instead of selecting the bar 3
in a menu, the user could utter the word three. Furthermore, speech recognition may serve
as speed access to the Web. To give an example, without a bookmark “weather in San
Francisco” would require a large number of search operations and selections [Mei 96].
Speech recognition cannot replace a mouse, because it is unsuitable for specifying a
position in a 2-dimensional space [Hum 96]. Speech recognition fits well in the overall
profile of a Multimedia Walkman, since, as defined in our scenario, the device is equipped
with advanced capabilities for digital storage and playback of audio sequences. The digital
sound recording capability can be used as a personal memo instead of a notepad.
The limited text editing capability can be accomplished with a chording keyboard. In a
chording keyboard each key generates a given set of characters determined by the position
of chording keys. The most trivial keyboards with respective capability appear on cellular
phones, but they are really slow for text editing. To change the character, you have to
press twice or three times the same key. By integrating different modalities, we probably
can implement the chording operation in a more user friendly fashion without reducing the
typing speed. In any case the integration of the modalities is a great challenge to
accomplish a smoothly operable user interface, fit also for the computer illiterate users.
Miniature sized output devices have made much more progress. By combining
microelectronics with micro-optics, displays comparable to the resolution of desk-top
monitors have emerged into the market from several vendors. Therefore, good candidates
for the output devices virtual display and earphones are available.
A headset or an ear-piece with a microphone is a must anyway if we use the terminal for
voice communication and in the same manner as a Walkman. In order to avoid false
operation of the speech recognition interface, we need to distinguish the voice commands
in simple manner from normal verbal conversation. One possibility is a headset with a
micro switch, which deactivates the microphone when turned aside. Voice menu
controlled operation is a controversial issue. It is unclear how users react to the idea of
talking to their computer. This issue needs to be addressed in subsequent usability tests.
5.2.2 Mobile Computing Environment
The unique features of mobile systems such as scarce channel (frequency) resources,
limited bandwidth, unreliable wireless link with inherent burst error tendency, frequent
hand-offs and limited CPU power of the mobile host impose specific constraints on a
mobile computing environment. Chen and Suda have mentioned the following design
constraints that stem form the above characteristics of mobile system[Che 97]:
• Minimum host-network (server) coupling to maintain low latency applications.
• Connection transparency and application partitioning with the ability to cope with
frequent disruptions of communications due to hand-offs, link failures, etc. In case of
disconnected operation the applications or some of their components should be able to
run seamlessly in the mobile host.
• Indirect interaction with user input/feedback processing done as close as possible to
the mobile host thus minimizing direct interaction over the unreliable wireless link.
• Adaptability of protocols to scale to different bandwidths and platforms.
5.2.3 QoS
The QoS of the multimedia applications and underlying services should not differ
significantly from what the users have been used to on respective low-bit rate wireline
connections i.e. in the PSTN. The available bandwidth now in PSTN is around 56 kbps
downstream and 28.8 kbps upstream. The previously described channel aggregation
technologies of wireless networks will offer roughly the same bandwidth, but due to larger
overhead and severe operational environment, the achieved overall quality is likely to
remain slightly below that provided in PSTN.
The delays introduced by wireless networks are also higher, but design criteria for them
should be such that the difference does not distract users. This may be difficult in a cellular
network, because the network channel coding is bound to increase round-trip delays.
5.2.4 User Indications and Help Functions
System failures occur now and then and it is good design practice to give the user
appropriate indications and guidance during different phases of the call. The help functions
of most PC applications are very user unfriendly and there is no doubt that such helps are
less attractive for an everyman’s multimedia information appliance. The user should be
notified of a system failure and this should automatically trigger relevant user guidance as
how to deal with the problem. Furthermore, the user should be able to access a help-desk
for asking guidance from a human operator.
Advice of charge should be available during all phases of the call and when a user is
changing his service profile (see Section 8.5).
5.3 Basic Architecture and Core Technologies
The architecture consists of three main entities: a belt mounted or handheld terminal with
advanced mobile computing and communication capabilities, which is subsequently named
personal multimedia appliance, a set of core services/applications and personalized
application content. The architecture is depicted in Fig. 7.
Internet phone and
multimedia desk-top
PSTN
LEC
Multimedia
Walkman
IWF
ISP
Mobile
Network
Internet
LAN/Intranet
Content
provider
Personal space
Service/
Applic.
provider
Background
processes
Corporate
multimedia
terminal
Applications and
content
Figure 7 Architecture for personal multimedia communication space
A multimedia Walkman user can establish calls in circuit switched mode over the mobile
network to PSTN, Internet, and ISDN as well as to other mobile users. In case the
Internet is the destination, the call can be routed straight across an Internet gateway or via
PSTN supporting the appropriate Interworking Functions (IWF). The former case
concerns also the packet radio mode. The residential terminal is connected to the Internet
service provider (ISP) over a copper line and the local access provider (LEC).
The functional capabilities of the Personal Multimedia Communication Space are listed as
follows:
•
•
•
Mobile computing capabilities: CPU + OS + firmware including local buffering and
storage media and a set of generic platforms, yet adaptable to specific needs, to
support core applications,
Energy supply capabilities: battery and recharger possibly based on
capture/conversion of kinetic and/or solar energy
Connectivity capabilities: Air interface, embedded firmware, protocol SW and
network interfaces
•
•
•
•
•
•
•
•
•
I/O capabilities: input/output devices including related HW and SW for supporting
human-computer interaction
Location identification capability(GPS)
Core communication capabilities : voice communications, e-mail, file transfer, client
emulation, Web browsing with on-line VOI
Additional communication capabilities: videophone, digital imaging & storage
(optional adds-on)
Sound recording capabilities: digital voice recording and playback
Customization capabilities: self-configurable applications based on Java applets to
meet specific user needs such as personalized news, personalized navigation aid,
personalized entertainment, and personalized health monitoring [Mar1996]
Supporting capabilities: such as facilities for security and authentication(e.g. smart
card), electronic payment, net shopping, tools for personalizing content e.g. based on
Internet push technologies, an organizer with a clock, reminder with remembrance
support.
Multi-mode operation: wireless wide area access in non-residential environment with
seamless shift to a cordless extension of the residential fixed telephone line at home
Addressing and call routing capabilities: unique access number i.e. the identity of a
mobile user is transferred to the wireline telephone, either manually or automatically at
home (UPT support in the fixed network required)
The architecture should be flexible based on a modular design, which allows the user to
acquire the terminal in many different configurations. Additional functions and features
should be embedded in a cost-effective manner to a basic functional framework. The basic
configuration may contain only the mobile computing platforms, POTS, e-mail, WebApplet browsing, and Java applet retrieval (“tune-in”) with on-line speech (voice browsing)
i.e. it would not differ significantly from a Network Computer (NC).The communication
interface should support multiple slot data access to the Internet
6. PRODUCT DESIGN AND MARKETING STRATEGY
CONSIDERATIONS
The development of a multimedia Walkman is not only going to be a great technical challenge, but very much so also in terms of marketing. Therefore we have investigated what
basic factors should be taken into account in product design and marketing strategy by
applying the classic adoption and diffusion theory [Rog 62]. We have reviewed in three
case studies success factors of products, which bear resemblance with our target. The
objective is to identify factors, which have been decisive for the success as well as those
that have been less fortunate choices. Furthermore we have applied perceptual mapping to
position our target product in regard to the referenced products.
6.1 Adoption and Diffusion
John Howard [How 88] points out that the most frequently cited reason for failure of new
products in the marketplace is the inability to judge consumer reactions to them. In his
theory. Howard distinguished three different classes of products. Extensive Problem
Solving (EPS) occurs when a consumer confronts a new brand in a new product class.
Limited Problem Solving (LPS) occurs when the conditions are as above, except that
product has been already established. In the third category Routinized Response Behavior
(RRB) the product represent a familiar brand in a familiar product class. Duly when an
innovation creates a new product class as would be the case for a multimedia Walkman, all
users face EPS. As time goes by and other entrants emerge in the business, the brands are
new, but consumers already have advance knowledge about the product class and they
move to LPS. Gradually users slide into RRB as the brands become familiar to them. It is
apparent that the barrier to make a purchase is the higher the more problem solving is
present in the process. This implies that risk of rejection is also higher.
The adoption is the acceptance and continued use of product, service or idea [How 88].
There are several hierarchical models, which assume that consumer adoption moves
forward sequentially through distinct cognitive, affective and behavioral stages. Everett
Rogers and Floyd Shoemaker[Rog 62] have classified in their model the adoption process
into four stages, which they named Knowledge, Persuasion, Decision and Confirmation. In
the Knowledge stage a user receives some stimulus that arouses his interest and he gains
some understanding of how the innovation functions. In the Persuasion phase the user
forms either positive or negative attitude towards the innovation. In the Decision stage the
he or she takes decision to accept or reject the innovation after having engaged in
discussions with other people and retrieval of additional information. After making the
decision, the user still need reinforcement to take the final step. He may reverse his
previous decision in case he derives contrary evidence. The consumer decision making is
affected by his individual personal characteristics, his social characteristics such as
cosmopoliteness and the strength of his perceived need for the innovation. Regardless of
their widespread use, the models have not been widely accepted by the researchers. John
Howard and William Moore consider the models reasonably feasible for describing the
adoption process in simple terms, under such circumstances when the product is new and
different.
Diffusion is the spread of an innovation throughout a social system [How 88]. The
consumers do not necessarily advance in same pace from one stage to another in the
adoption process. We have learned through a number of investigations that some people
are inclined to adopt new innovations more quickly than others. Furthermore, the speed of
which an innovation is being adopted may vary within a broad range depending on the
characteristics of the innovation.
Rogers and Shoemaker developed a classification in which they divided the consumers
into five basic categories depending on their adoption behavior. In each category the
consumers share some stereotype values, which are assumed to influence strongly their
consumer behavior. Innovators are characterized by ventureness, hazardousness, daring
and desire to be ahead of others. Early adopters are associated with attributes such as
respected socio-economic status, high education, leadership and good product category
knowledge. The early majority consists of users, who deliberate some time with care, but
who are willing to adopt innovations before the average member of a social system. The
late majority is characterized by skepticism and they tend to adopt new ideas after the
average member of the social system. The pressure exerted by their peers is usually
necessary to induce the adoption. The Laggards are the last to adopt innovations and they
possess no leadership in opinions. Their values are strongly related to traditions and those
cherished in the past. When they at last adopt an innovation, it may have been superseded
already by a new innovation
Number of users adopting at
time t
Cellular Phone
Walkman (portable audio
cassette recorder)§
PDA
Smartphone
Innovators
2.5%
µ-2σ
Early
adopters
13.5%
µ-σ
Early
majority
34%
µ
Late
majority
34%
µ+σ
Laggards
16%
t = time of adoption
Figure 8 Positioning the products of case studies on Roger’s diffusion curve
We have positioned some existing product categories on Roger’s and Shoemakers well
known diffusion curve (see Fig. 8). Each of the products appears in different position on
the curve. Furthermore the evolution history is quite different.
Sony Walkman was targeted to the consumer market from the very beginning, but some of
the later versions such as model WMD6 attracted also professional market.
The mobile phone addressed the demand of the business market, but is now penetrating
per force to the consumer market.
The PDA, as we conceive it, emerged 1992 in the business market. In our studies we have
made a distinction from handheld PCs or subnotebooks by classifying the PDA as a pen
based computer. By contrast handheld PCs or Subnotebooks are miniaturized replicas of
notebook PCs, which implies that they constitute a logical step in the portable PC
evolution procedure incorporating a typical computer architecture, a keyboard and a set of
basic office applications. It is debatable whether the location of PDAs should be placed in
the innovators or early adopters category on the curve.
The smartphones or personal communicators appeared in the market 1996 offering a
lightweight all-in-one mobile office communications solution for business travelers. Their
profile differs from that PDAs in the sense that the emphasis is in communications i.e. in
capabilities such as wireless telephony, telefax, e-mail, and Web browser, whereas PDAs
are devices with limited connectivity, but excellent for rapid storage and retrieval of data.
There is no doubt that for the time being, only early innovators possess a smartphone.
6.2 Case Studies
6.2.1 Case Study 1:Sony Walkman
We chose Sony Walkman as a target for our case studies for a number of reasons. First it
resembles the multimedia Walkman of our scenario in many respects. Second it is a
portable consumer device, that has been studied rather extensively. Third, it was an
innovation that created a new life style.
The invention of Walkman was accidental, which is the case for many great innovations.
The production of Sony radio cassette recorders was transferred to company’s radio
division from audio tape recorder division and this forced the tape recorder division to
come up with e new product idea, which they contrived in a brainstorming event. The
engineers in the audio group had developed the Pressman, a portable cassette recorder
with high quality sound for reporters in the business market, which constituted basis of the
Walkman.
Table 5 Sony’s technological leadership in personal portable stereos [San 95]
Feature
First Walkman
AM/FM stereo radio
Firm (innovator)
Sony
Sony
Date
79
80
Imitated by competitors
Yes
Yes
Stereo recording
Sony/Aiwa
80-81
Yes
FM tuner cassette
Toshiba
80-81
Yes
Autoreverse
Sony
81-82
Yes
FM headphone radio
Sony
81-82
Yes
Dolby
Sony/Aiwa
82
Yes
Short-wave tuner
Sony
83
Remote control
Sony
83
Yes
Separate speakers
Sony
83
Yes
Water resistance
Sony
83-84
Graphic equalizer
Sony
85
Yes
Solar-powered
Sony
86
Radio presets
Panasonic
86
Yes
Dual cassette
Sony
86
TV audio band
Sony
86-87
Yes
Digital tuning
Panasonic
86-87
Yes
Child’s model
Sony
87
Enhanced bass
Sony
88
Yes
Some other coincidences contributed to the success. At the same time a research group
was developing miniature earphones without being aware of the portable audio cassette
project. By accident Sony’s honorary chairman dropped by and made connection between
the two projects.
Sony has invested heavily in product development during the whole life cycle of the Sony
Walkman. This is reflected by the Table 5, which clearly shows the exceptionally strong
dominance of Sony in developing novel value-added features to Walkman.
Walkman was not only a technical innovation. Subtle marketing strategy shaped the
market and created a new life style [Uey1982],[San1995]. The CEO Akio Morita took
himself the leadership of the Walkman project team. He insisted on a global brand name
“Walkman”, which facilitated the worldwide dissemination of the product. At the same
time the engineers did their best to bring down the production cost. Rapid take-off of the
market enabled economies of scale, which turned the business rapidly into a profitable one.
The target customer segment was young, active, and sporty people, frequently in motion.
The initial price was set by Morita’s decision below the break-even level. The attractive
pricing accommodated the purchasing power of teenagers.
Production of the Walkman started in 1978 to the Japanese market with a batch of 30000
units. It was sold out in three months. In 2 years the first model had sold 2 million units
the production lagging constantly the demand. Since the introduction of the Walkman
Sony has been leader in both technology and product diversification. Sony launched as
many as 250 new models to the US market in the eighties. Being first at the market is a
huge benefit, which has certainly contributed to Sony’s success.
Analysis
The longevity of the Sony Walkman market is unusual in consumer electronics. The main
reason is of course the lack of serious competing technologies. Another reason is the
strong demand and new life style that was created. The third reason is the strong
innovative effort in the development of brands. The consumers were constantly offered
new models with better performance and new features. The Walkman case suggests that
to gain a sustainable dominating market position, we need an innovative product concept,
a set of core technologies, QoS acceptable to the user (high quality stereo sound),
constant product diversification with new innovations, and a well organized marketing
strategy.
6.2.2 Case Study 2: Mobile phone
The cellular phone has come of age after 16 years of evolution. First products were
launched in 1981. In Scandinavia they were sold through service providers. The current
distribution channels, such as home electronics and cellular phone retailers, were not
created until in the nineties. Both Nokia and Ericsson entered the business at that point in
1981. Motorola came somewhat later, but took full advantage of the expanding US AMPS
market. Already in the eighties the company reached the leading market position.
The penetration approaches 30% in Finland, Norway and Sweden. USA and Japan are
catching up rapidly. In August 1997 the number of US mobile subscribers exceeded the
level of 50 million users corresponding to 18%, which is fairly close to that of Japan. Just
a year ago there was a significant difference in penetration between USA and Japan. Now
Japan seems to have been overtaken by wireless communications. This conclusion can be
drawn from the impressing growth rates, which are twice as large as in USA and Europe.
The booming PHS business seems to have given an additional impact to the entire market.
Rather than competing against each other, low-tier and high-tier systems are making
excellent progress side by side. The US statistics suggest a slight decline in growth rate in
USA.
The cellular phones have diversified enormously during their 16 years of existence. Lowend consumer terminals with only the basic functions have emerged as well as high-end
smartphones and all kind of variants falling between these extremes. The main competitive
factors have been size, overall weight, fashionable design, user-friendliness, operational
usability i.e. stand-by and talk time between battery recharging cycles and value-added
features. A broad range of different accessories play important role for most users.
The big manufacturers, dominating the market Motorola , Ericsson and Nokia have been
in the business for a long time. It is no doubt about the importance of an early entry into
the business. The Japanese big electronics companies awaited too long and have not
succeeded in gaining any significant market share. The cellular phone itself is a highly
refined electronics product, which have intelligence of the order 100 MIPS. The degree of
integration has grown steadily as more powerful signal processors and other chips have
been developed. The competition is extremely hard even if the market is growing. Profits
have eroded and economies of scale are becoming more and more important.
According to CTIA survey, in 1995, 39% were sold through carriers and the remaining
61% mainly by cellular phone or consumer electronics retailers. In USA, 57% of cellular
phone users use it for outgoing calls only and one third had used the phone in emergency
situations. We lack respective data from Europe and Japan, but it is likely that personal
safety plays a minor role in the decision making of Japanese and European consumers.
45000000
US mobile phone users
(CTIA mid-1996 survey)
40000000
35000000
30000000
25000000
Year
20000000
1987 1988 1989 1990 1991 1992
1993 1994 1995 1996
15000000
10000000
5000000
0
1
2
3
4
5
6
7
8
9
10
Figure 9 US mobile phone users
The weight of cellular phone has reduced steadily, but there are some hard constraints,
which still remain. The research for more effective batteries is making rather slow
progress. Signal processor needed for channel and speech coding as well as delay spread
equalization and echo cancellation tend to be power-hungry. Therefore, to increase the
stand-by and talk time, a more powerful and heavier battery is required resulting in less
comfort.
The adoption of cellular telephone by far exceeded the wildest expectations in the eighties.
There was a very strong unsatisfied need, which burst out into a frantic demand once
supply appeared. Customer polls carried out in the Scandinavian countries [Mag 85]
showed that cellular phone solved the problem of reachability, which was crucial for small
business enterprises with only a few key persons to serve customers. In those days voice
mail systems were not yet very widely used. Therefore, there was no realistic substitute to
mobile phone, which enabled the customers to reach key sales and marketing people at
any time from any place. This factor turned out vital for the business, since the high
terminal price and service charges did not deter the market growth. The value the
customer gained in using the mobile phone was high enough in the form of increased sales,
better customer service, and more effective use of human resources. Besides sales and
marketing personnel, there is a fairly large group of other people in all social systems, for
whom it is vital to be reachable 24 hours a day regardless of their whereabouts. This user
group consists of physicians, social workers, lawyers, CEOs, service personnel, truck
drivers, etc.
The results of following market research (see Fig. 10) suggests that low service price,
geographic coverage and sound quality are the most important factors to induce adoption
of mobile phones. Therefore, subsidizing terminal prices at the expense of high service
charges is a bad policy, which is not supported by the users. Speech quality and broad
service mix are decisive factors to encourage adoption. This assumption is confirmed by
the recent success of GSM all over the world including USA, where the growth rate of
PCS 1900 subscribers has been well above the average of the analogue AMPS.
Subsidizing handhelds with service charges and charging recipients for incoming calls as
well have contained the diffusion and kept the utilization rate at a fairly low level of 125
minutes per user per month [Don 96]. This explains the high number of users in USA, who
use their mobile phone for outgoing calls only. These users usually have got a pager to be
alerted for incoming calls.
WIRELESS SERVICE DECISION FACTORS
Don't know
Other
Service provider name
Past experience with
company
Large/well-established
company
Filter/screen calls
Total voice interface
knowing how charged
Important
Most Important
Company with best
product/service
Easy roaming
Customer support
Long battery life
Easy to use
Geographic coverage
Low equipment price
Sound quality
Low service price
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Figure 10 Wireless service definitions factors (Source: Business Research
Group[Mey 97])
Analysis:
In the future, the growth will depend more and more on the consumer market and
consumer behavior. The products are becoming ubiquitous and high level skills to make
them is not required to same extent as before. New entrants are to be expected in
particular from the Far-East countries such as China with tremendous internal market
potential. It is likely that the share of the three companies, dominating the market, will
decline in the next few years even if the volumes would increase due to huge expected
market growth. The current experiences indicate that the low price of the usage is most
important accompanied by wide geographic coverage and good speech quality. We cannot
map these results directly into Internet telephony. For instance, many mobile Internet
phone users might accept an inferior speech quality provided that the service charge would
be much lower than placing a call over PSTN. For the precious radio access, users are
metered and charged anyway, which means that low-cost wireless IP telephony does not
look realistic. In USA, geographic coverage is fuzzy as seen from the end-user perspective
due to fragmentation of the mobile market and different standards. One particular system
does not guarantee operation in all places of the continent. Users moving around need a
dual-mode phone or at least a pager to be reachable anytime anyplace.
6.2.3 Case Study 3: Personal Digital assistant (PDA)
The evolution of PDAs started in the late eighties, when GO corporation was founded
[Kap95]. Subsequently GO was merged with AT&T, but commercial exploitation of the
innovations of GO corporation fell through. Apple launched development of its first
version of Newton a bit later. From the very beginning the objective was to use pen as the
main input device to address the needs of a number of users, who spend a large amount of
their time away from a desk and who need a lightweight portable device for information
storage and management.
Therefore characteristic features of a PDA are pen based user interface, handwriting
recognition, and information storage/management capabilities. Regardless of the expected
huge market potential, stemming from the wide user group, we may ask, why these
devices have not been accepted by the market. There probably is no simple answer. The
main reason might be inadequate value in regard to price. The other reasons are weak
communications and applications support, too bulky implementations to really fit into
pocket, too slow hardware, and unreliable handwriting recognition software. For instance
Apple’s Newton MessagePad 2000, representing a result of 5 year evolution, is still is too
big to serve well as a device for personal information management, which would be
certainly appreciated by business travelers. The US Robotics Pilot, which has taken the
market by storm, does not suffer from any of the above deficiencies. The price is
attractive, the user interface is simple and user friendly and the device is light and pocket
size. The PDAs will now face increasing competition from handheld computers and
personal communicators. In the professional market, there is a demand for pen based
computers, but for this market segment value-added applications play important role. In
particular in healthcare applications PDAs have been used already and prospects are good
in this enormous $1.3 trillion industry [Mar 97]. Another important market segment is the
utilities sector [Gia 97]
Regardless of the modest market so far, the potential seems huge, once the price vs.
performance
and technology are in balance to offer the good value to the user. The number of new
entrants in the business including IBM is a clear signal about growing faith in PDAs. The
high end PDAs have a large high resolution display and the price is on same level as that
of notebook PCs. These markets are differentiated to narrow professional market
segments. In the middle between the high end and low end applications, the PDAs are
confronting tough competition from subnotebooks and smartphones in the less costsensitive business market segments. In the low-end PDAs do not have competition, which
has furthered the success of USR Pilot. Before the launch of Pilot the price level had been
far to high from consumer adoption point of view. From our research point of view the
Pilot is the most interesting one and therefore, we will take a closer look at it.
Since the launch of first Newton, it was apparent that PDA could not and should not be
either a portable computer or its replica. The notebook by far outscored a PDA in all
respect in heavy-duty data processing. In other words, a PDA should be something else
with different, yet distinct profile. This has been the starting point of USR Pilot design
[Sbi 97]The development team set three prime design constraints: lightweight and small in
size to fit to pocket, speed, small memory requirements. These design goals dictated the
technical solution, which automatically contributed to low overall cost. The designers’ aim
was to make the OS simple and fast with minimal services, without supporting any heavyduty processing. They assumed that users anyway prefer to do this in their own desk-top
environment. The built-in SW applications consume ROM capacity from 14kB to 54 kB.
Power consumption is amazingly low due to simple construction and clever power save
modes. Pilot can operate for 8-12 weeks with two alkaline AAA batteries. The Pilot has
been highly successful due to clever design and good understanding of user needs. In
terms of shortcomings, the user would appreciate better connectivity across a mobile link.
In the new version, also e-mail is supported, but you need an auxiliary modem and
communication software. Web browsing in this kind of low-end device is less realistic
given the design goals, at least for the moment.
Analysis:
Adoption of PDAs has been rather slow in a highly differentiated professional market. The
products have been designed to serve a specific purpose. Operating systems have been
launched by a number of vendors, neither of which has gained a strong market position.
Feasibility of Microsoft’s CE for PDAs remains to be seen. For the moment CE has gained
popularity in HPCs only. Not until generic HW/SW platforms are available can we expect
a substantial price reduction in the differentiated high-end business markets. In the
consumer market the early adoption is underway. Between the low-end and high-end, we
have devices such as Sharp Zaurus with color display and digital camera. More provision
and competition is to be expected in the low-end market. This is likely to boost the market
into a higher gear. Given the experiences derived so far from low-end PDAs, the
multimedia Walkman should not address same capabilities as a notepad computer. The
significance of keeping it lean and mean is obvious. However, definitely better connectivity
is required than what is the case typically for PDAs, which are becoming personal
information appliances.
6.2.4 Summary and Conclusion
The investigated three cases (see Table 6) have some common denominators as well as
differentiating factors. The Sony Walkman was adopted very rapidly which entailed rapid
diffusion. The market was well prepared for this product. The diffusion of audio cassette
recorders into homes was widespread. There was a lot of prerecorded material. Albeit a
novel product, the user interface functions were familiar such as PLAY, REW and FFWD
functions. Therefore, even if the brand and product category were novel, users were
familiar with audio recorders. Similar conditions prevailed for the first mobile phones. It
was after all a telephone and placing a call did not differ significantly from normal POTS.
The diffusion was not as rapid as was the case for Sony Walkman. There are many
reasons, which contained the speed of diffusion. Offering wide geographical coverage and
appropriate infrastructure took a long time. In Europe, there was no common open
standard. During the first years of deployment, the technology was very bulky an not
really portable. As for the PDAs, the product was so different from what potential
customers were used to and this has therefore probably raised the barrier for adoption.
The Sony Walkman started to create a new life style from the very beginning. To some
extent, this was the case for mobile phones, but mainly in Scandinavia and at much later
stage when the small handhelds were introduced. The handheld hanging on the belt
became a sign of active businessmen, always within the reach of their network. For PDAs
we cannot yet perceive any similar tendency.
The market volume of portable audio cassette recorders is probably declining, because of
evolving digital audio recording technology. The mobile phone market is likely to expand
up to $ 25 billion or beyond by year 2000. As for PDAs it is very difficult to make any
predictions. It is likely that the market growth in the next few years will be not be as rapid
as one might imagine.
Table 6 Comparison of studied cases
Attribute
Market volume ($ bn)
Launched into market
Diffusion
Target user groups/
market at launch
Sony Walkman
6
1979
rapid
youths/outdoors recreational/consumer
Mobile phone
13
1981
medium
small business venture
professionals/
business
Prime function to
attract user adoption
Playback of high
quality audio stereo
High quality speech
anytime, any place,
PDA
1.1 (incl. HPCs)
1992
slow
Medical etc. public
services/business
desk-top PC users/
consumers
Quick access and
management of per-
recordings
Life style
Key technologies
Required infrastructure
User problem solving
at time to market
familiarity of
adjoining product
categories
Network externality
Yes (global phenomenon)
Miniaturized audio
cassette with 4-track
stereo and earphones,
Audio C-cassette
24 h reachability,
emergency aid
Yes (regional phenomenon)
Mobile-aware signal
processing, air-interface design
Cellular networks
sonal or task oriented
data
No
Extended
Extended
Extended
high
high
low
Recorded cassettes
Phone calls to and
from PSTN
Connectivity to own
desk-top
pen computing, OS,
handwriting recognition
Desk-top PC
6.3 Terminal Environment of a Multimedia Walkman
6.3.1 Characteristic Features
In the section 5 we defined and characterized the personal multimedia communications
space in general terms. Subsequently we deal with the terminal environment more in detail,
both in terms of terminal capabilities and their influence on basic HW characteristics. We
claim that a multimedia Walkman will change the existing paradigm of personal
communications, which address mainly the needs of business traveler and other
professional users. The new paradigm does not preclude from using multimedia
information appliances also in professional applications. On the contrary, they are likely
to be the driving force, in particular such applications, which require hands-free operation.
However, it is important to apply a consumer oriented approach from product design,
even if products from the first batches may be somewhat expensive.
The multimedia Walkman can be implemented in a number of different configurations. The
profile of the product in our scenario should clearly distinguish itself from personal
communicators and PDAs. We may ask, what are those functions and multimedia features
that make the distinction. The subsequent list exhibits functional and physical
characteristics of a multimedia Walkman :
• Terminal is pocket size (e.g. belt-mounted), lightweight, and for personal use only
• User interface:
-Input devices: a remote controller with speech recognition
-Output devices: Head mounted virtual display and headset or ear piece with
a separate microphone
• Connectivity: access to digital cellular and low-tier wireless networks with multi-link
reservation capability
•
•
•
•
•
•
•
•
•
Digital audio recording and playback, based on either a stand-alone or networked
storage media
GPS transceiver
Access to potential own desktop and personal information residing therein over the
Internet
A set of core communication applications: voice communications, voice mail, e-mail,
Web browsing with VOI (simultaneous voice-over-Internet), file transfer (FTP), and
Telnet
An interface agent acting as user assistant and broker between heavy-weight
information agents residing on the network
Optional features such as an auxiliary CD-ROM and a digital camera with still imaging
and video transmission, 3D virtual augmented reality
A set of mobile aware Internet tools, consisting of a browser and push technologies to
access customized self-configurable applications such as home shopping, personalized
news, and games.
A set of stand-alone applications such as a smart card reader, calendar, a clock, a
personal notepad, and a word processor
An array of background processes such as personal health monitoring, remembrance
aid.
User interface is definitely different from both that of PDAs and communicators. Good
implementations for the input device, remote control unit do not exist yet. For the output
device, there are head-mounted displays from several vendors, which would serve
relatively well this purpose [Eus 97]. Speech recognition has progressed a lot during the
past few years [Emm 96]. Since the terminal is intended for personal use, we can use
speaker dependent technology, which is cheaper and more reliable.
6.3.2 User Interface and Role of Agents
The agent technologies, based among other things on artificial intelligence, are on the
verge of commercial exploitation after 20 years of development. Modern agents have a
capability to learn through mistakes and the user’s past preferences. The user agent assists
the user to access such services and information content he is interested in. This entails
that the agent “knows” users’ habits and preferences. Furthermore, the agent
communicates with other agents residing in Internet servers and performing dedicated task
services. The agent can bring value in many ways to a nomadic user
• by simplifying complex access procedures
• by supporting user in search for customized content and
• by reducing information transfer across a costly, high latency air interface.
The architecture is depicted in following Fig. 11. The interface agent i.e. user agent
handles the user requests, displays incoming data and acts as broker between the user and
the information agent, which accomplishes heavy-weight searching and filtering tasks. The
database of the Web server contains user profiles, task oriented information and query
rules for accessing remote databases. Location information derived from the GPS system
enables location dependent services such as sightseeing navigation for tourists.
Extensive research is being carried out on itinerant or mobile agents [Che 96b]. A mobile
agent is a program, dispatched from the client to roam among a set of network servers to
accomplish specific, user initiated tasks. The security is the most crucial issue for itinerant
agents. The access of such agents to visit foreign servers will be strictly regulated. The
problem is two-fold: the roaming agent may be contaminated also by viruses injected by
the servers or vice versa. In mobile environments it is fundamental that amount of garbage
(read: undesired information) transferred over an expensive air interface is minimized. In
wireline environments you have same goal, but the consequences of excessive “chaff” are
not so unpleasant for the user as in the wireless networks. Another problem is platform
incompatibility, which is also present except when using Java based agents. An
information agent residing in the network, may have the same capabilities as the itinerant
agent under much better controlled security conditions and compatibility. Due to these
reasons, the significance of itinerant agents remains unclear in regard to the simple agent
architecture presented in Fig.11.
World Wide Web
Interface agent
Information
agent
Mobile link
GPS
transceiver
Location
information
User profiles
Local databases
Query rules
Client
Figure 11 Architecture of agent services
There is no doubt, however, that agents have a large potential in mobile computing environments, because the benefit an agent can bring to the user is even higher than in the
fixed one due to the narrow bandwidth of wireless air interfaces and limitations in user
interface implementations. Consequently lightweight computing environment, constrained
by scarce radio link resources, can interact with heavy-weight applications without prior
Server
knowledge of the remote server’s capabilities. The market opportunity for software agents
is not yet present due to modest value of mobile data communications market.
6.3.3 Terminal HW Characteristics
The following Table 7 contains some basic data based on a rough assessment of HW
characteristics. The architecture of a multimedia Walkman should be very flexible to
support broad terminal offerings from lean and mean low-end to high-end. Connectivity is
a key element of a multimedia Walkman. Given that a cellular phone is already a highly
sophisticated product with a processing capacity of a PC, all the functions listed in Table
7. would make the terminal very expensive, very power hungry and probably too bulky to
be accepted by users. Too reduce the complexity and keep memory size at its minimum, it
is important not to have any other permanently stored application SW on the terminal own
storage media than what is absolutely necessary. By and large, the idea of a network
computer i.e. down-loading the application SW data from the network is sound in this
context.
Table 7 Assessed HW characteristics of a multimedia Walkman 1
Function
Memory
DRAM/IDE/
FLASH
EPROM(MB)
Wireless system category
high-tier low-tier
Air interface incl, RF-ampl., 1/3
0/0.5
signaling, channel coding, delay
spread equalization
Speech codec(s), IS-54, IS-95, 0.5/1
0.5/1
GSM speech + G.723.1, G.726
(ADPCM)
CPU (RISC)
(8 - 16) (4 -8)
OS with basic services
3/3
3/3
E-mail, SMTP, FTP, Web 3/5
3/5
browser, HTTP, data interface
Audio recording & playback
8/0
8/0
user interface, display + con- 1.5/64
1.5/64
troller
Receive Buffer
1/0
1/0
GPS transceiver
1/1
1/1
Video and imaging (fully SW 1/5
1/5
based H.263)
1
signal processing
capacity (MIPS)
Average power
budget (W)
high-tier low-tier
50 - 60 10
high-tier low-tier
1.0-1.5 0.3-0.5
20
0.2
0.2
100-200 100
NA
NA
NA
NA
0.5-0.7
0
0
0.5
0
0
30
70-100
30
70-100
0.1
0.7
0.1
0.7
NA
NA
NA
NA
NA
NA
0.1
0.1
0
0.1
0.1
0
20
Table 7 represent a very rough estimate of the needed HW characteristics. At this point, it is difficult to
assess more accurately the HW needs without a deeper understanding of the terminal architecture and
implementation.
Organizer functions
Radio receiver (VHF/UHF)
User agent
TCP/IP
Other apps and firmware
Total
0/0.2
0/0
0/0.3
0/0.5
0/2
20/85
0/0.2
0/0
0/0.3
0/0.5
0/2
16/82.5
NA
0
NA
NA
NA
270-410
NA
0
NA
NA
NA
230-260
0
0.1
0
0
0.1
2.9-3.6
0
0.1
0
0
0.1
2.2-2.4
However, down-loading heavy applications with large amount data has one downside.
Besides being costly, the down-loading time tends to last too long due to the narrow
bandwidth currently available for mobile data links. Therefore, the applications mix is
restricted to lighter, in particular Java applications residing in the Internet. For instance
most games include a lot of data, and it is not reasonable for the user to down-load it from
the network. In this case, the use of an auxiliary portable CD-ROM is recommended.
In terms of FLASH memory capacity, in particular a speech recognition based user
interface consumes most of it. The high cost stemming thereof is the prime factor that
impedes the use of speech recognition based user interfaces. Otherwise, the technology is
mature. Therefore, to keep the price of a MMW at a reasonable level, only a limited set of
commands is possible. A dedicated signal processor for the voice recognition is
recommended. As far as RAM is concerned, a voice recording capacity say up to 30
minutes requires a lot of memory. The rough calculation suggests that a processing power
of around 300-500 MIPS is needed depending on supported functionality. An IDE
FLASH memory of around-96 MB, fit for severe environmental conditions, is
recommended instead of a hard-disc. Current price level of the FLASH memory technology is high, but prices are slumping rapidly.
6.3.4 Significance of Mobile-Aware Platforms
It is obvious that a broad range of future portable information appliances is likely to utilize
different operating systems. This setup favors platform independent applications such as
Java. The current Web applications are tailored to wireline networks. This implies that
they do not conform to the bandwidth restrictions, limited memory and CPU capabilities,
small display sizes, that are typical of wireless terminals. The big players of mobile
industry have agreed to develop a wireless application protocol (WAP) to prevent the
mobile data market from fragmentation [Tee 97].
Furthermore, a wide variety of application specific user interfaces raises the barrier of
adoption. In a restrictive mobile computing environment, a vast majority of users are likely
to use such applications only, which they can access across a common universal interface.
Java technologies will provide tools for addressing this need. As the amount of
Internet/Web users is almost doubling every year, the market diffusion for generic Web
browsers is expanding in huge proportions. Therefore, it is a sound strategy to choose the
browser as a generic tool for accessing all kind of multimedia services across the Internet
as well as personalized content. However, the unique characteristics of wireless links
impose special requirements on the Web tools, which means that they need to be also
mobile aware. Such SW tools are already available now from Unwired Planet and more
soon from other vendors as well. This entails effective use of the restricted bandwidth with
low protocol overhead. The Web browsers of the first communicators support text only to
maintain low latency in browsing. The expected increase in bandwidth due to aggregation
of multiple radio links and high speed satellite data communication will enable transfer of
multimedia content as well, but the user should be given the possibility to revert to plain
text when he or she wishes to.
The Web browser is a must for business communication oriented terminal, but besides
unreliable best-effort based communications, business users require a reliable service with
predetermined QoS guarantees. Furthermore, mobile videotelephony in accordance with
forthcoming mobile extension of H.324 standard is likely to be desired. Given the fact that
we are dealing with two highly intelligent and sophisticated products, it is logical to
assume that the evolution is driven by the business market oriented products.
6.4 Perceptual Mapping
Urban and Hauser [Urb 93] point out that successful new products deliver benefits that
customers need and they can be obtained only by listening to the customer. However,
when a product concept is radically new, it is difficult for the user to say, whether the
delivered benefits meet his/hers needs. Therefore, besides interviewing the user interviews,
the user should be given the possibility first to test a replica of the product simulated in a
testbed. In the second phase of this investigation, we intend to carry out the tests.
Urban and Hauser have presented various perceptual mapping techniques to facilitate the
understanding of a product category. Rather than addressing the physical characteristics
and functions of a product, perceptual maps focus on the user needs and value he/she
gains from using the product. Users make judgments through the reality they perceive.
Urban and Hauser emphasize the importance of identifying opportunities, selecting target
position and steering the product design process in such a manner to establish so called
Core Benefit Position. Most products are evaluated within the perceptual realm of the
category they belong to. However, if we feel that a new emerging dimension will have
significant impact on the way users perceive the product, our best choice might be to
identify that revolutionary dimension. Because a multimedia Walkman is a new product
combining wireless telephony, mobile computing, digital sound recording and Internet
tools, it is likely that a new dimension will influence users perceptions. To put a multimedia Walkman into perspective, we have mapped it together with our case study products and some of their close relatives in perceptual map appearing in Fig 12. The nomadic
or yuppie lifestyle relates to young consumers with substantial purchasing power, respect
for physical strength, beauty, desire for traveling, and good education. Sony Walkman was
welcomed by young people, who wanted to listen to their favorite music regardless of time
and place. It turned out that a user could enjoy his favorite melodies even during rollskating, jogging and hiking. A multimedia Walkman is bound to absorb more of a user’s
attention and therefore it is less likely that the device would be used under similar
circumstances. This does not make a difference in the selection of the target user group,
but different strategy, than what was applied for Sony Walkman is needed to address the
desires and preferences of the target user group.
We claim that ease and convenience of use will become the prime strategic success factor
which means that more and more of the processing power need to be allocated for user
interface technologies. For the multimedia Walkman, those technologies do not exist yet
and it is fairly difficult to foresee, what kind of solutions could fulfill our needs.
The nomadic and yuppie lifestyles are gaining more and more widespread adoption,
Scandinavia and Japan being the forerunners [Mak 96]. The user interface of a Sony
Walkman is extremely simple, which is the case also for the Pilot. User interfaces of a
personal communicator and a subnotebook bear some resemblance, which is characterized
by a keyboard and lack of user-friendliness. Without past computer experience a user
would
feel
uncomfortable
with
such
devices.
Psychological comfort
• Mobile phone
Conservative lifestyle
• Sony Walkman
• PDA (such as USR Pilot)
personal
communicator
•
Sub-notebook
•
• Multimedia Walkman
Ease and convenience of use
Nomadic/yuppie lifestyle
Figure 12 Perceptual mapping of personal information appliances
The user interface of mobile phones is usually a bit awkward due to complex menu structures and the fact that a user has to manage numerous operations with a minimum set of
keys.
The third dimension is psychological comfort, an attribute of high importance in consumer
decision making and adoption. It is likely that this will be one of the prime adoption
criteria of future intelligent personal appliances. The possibility to access in user friendly
fashion such information content, which is important for the user, i.e. to satisfy the user
need, is likely to influence strongly the psychological comfort as well. In the Sony
Walkman case, there would not have been a market for the cassette recorders without
prerecorded music that met the user taste. It is obvious that personalized content is going
to be a strategic success factor also for personal multimedia appliances.
In order to characterize a multimedia Walkman, we have applied also other mapping
techniques. We have designed a product hierarchy of personal information appliances,
appearing in Fig 13. It describes the product hierarchy with evolution paths, either known
or predicted.
Personal communication and
information processing
Portable devices for
information management
Pen tablet
Organizer PDA
Cellular phones
Personal computers (PC)
Portable PCs
Multimedia
desktop
Network
computer(NC)
Set-top
unit
Notebook PC
Wearable
computer
Smartphones
Multimedia
Walkman™
Handheld PC
Personal multimedia
communicator
Multimedia
Notebook PC
Wireless NC/
Internet phone
Nomadic Age
Note: the dashed lines suggest potential evolution paths
Figure 13 Product hierarchy of personal information appliances
If we take a look at the two products appearing at the bottom of the picture, we can make
the following observations. The multimedia Walkman reflects the next evolution phase in
the consumer market and the personal multimedia communicator the next evolution phase
in the business market. It is highly likely that the consumer oriented multimedia Walkman
will rely heavily on the Internet. This goes also for the speech communication i.e. mobile
Internet telephony. This implies that enabling also wireless phone access to the Internet,
appropriate gateways have to be embedded in the networks. Insuring interoperability is
more complicated than in the landline case, because protocols and speech codecs are
usually more robust i.e. adapted to error-prone environment. Transcoding of speech and
video may degrade the QoS, possibly to an unacceptable level from the user point.
Affinity diagrams represent another technique [Urb 93] to identify and map user needs.
Usually they are implemented based on data derived from user feed-back. In this case,
such feed-back does not exist. Therefore, the next diagram (see Table 8) is an educated
guess of user needs, a set of core functions, and strategic benefits they bring to the
customer within the concept of multimedia communication space. The diagram will be
updated later on based on test results.
Table 8 Affinity diagram of a multimedia Walkman
Strategic User Benefit Tactical User Need
Customized
terminal Support for customized service
configuration
mix and media components in
accordance with user needs
Underlying Core Technologies
Modular
architecture
with
negotiable platforms for voice,
video, and data, down-loading of
apps stored in the network
Low-tier mobile network, multi-link
operation, low latency codecs,
gateways and IWUs, multi-mode
transceivers
Ubiquitous
Possibility to establish phone,
communication anytime multimedia and data calls to
anywhere
other networks at a reasonable
cost with roaming capability, online advice of charge
Accessing Internet/Web Web browsing, (VOI), voice wireless data with bit-rates up to 64
services/applications
browsing, file transfer, down- kbps, Inet gateway, packet radio
loading of data
access,
mobile
aware
OS,
protocols, and applications
Accessing data located Up- and down-loading data, Telnet, FTP, ppp, LDAP
on own desk-top or sending and reading e-mail
servers
Accessing customized Retrieval of information accor- user agents, Java tools, Web push
service/application
ding to user profile, self-confi- technologies and tools, in-band data
content
gurable homepage and user for charging and billing, access
profile, On-line advice of charge control.
Convenience and overall Good ergonomics, light-weight Low power technologies for HW,
operability
terminal, continuously operable, OS and SW platforms, self generusage
supporting
functions ated power, organizer functions and
(directory etc.)
remembrance aid, user interface and
agent technologies
Ease of Use
User Friendly user Interface
Voice recognition, a remote controller, context based user guidance, a user agent
Interactivity
Short response Times
low latency coding and protocols
Mobility
Moving around while using the Mobility management, Voice menu
terminal, roaming into other controlled user interface, hands-free
networks
operation
Controlled QoS
QoS levels adapted to user needs Both
upgrade
and
graceful
under user control (a set of degradation of QoS, error control
Privacy and security
Navigation
profiles) , no significant impairment of QoS compared to
respective landline data links
Verification of authorized service
provider, protection against
fraud, secure transactions
Location data
for end-to-end and air interface,
gateways with rate adaptation and
transcoding capabilities
Access device for information
security with authentication, personal ID and password, RSA and
other encryption facilities
GPS, digital map applications