The Future of Mobile Communications
Professor Rolando Carrasco
BSc(Hons), PhD, CEng, FIEE
R.Carrasco@newcastle.ac.uk
School of Electrical, Electronic
and Computing Engineering
1
Research Project 1
• The Capacity and Throughput Improvement of Fixed
Broadband Wireless Access Systems
Dr. Pei Xiao, Research Fellow (three years)
Mr. M. K. Khan BEng, MSc, Research Student (21/2
years)
EPSRC Grant in collaboration with Dr. I. Wassell,
Cambridge University and Cambridge Broadband Ltd
2
VectaStar System Configuration
Standard 4 Sector Base Station
Subscriber Unit
AP beam patterns
23° x 23°
antenna
90° x 8°
antenna
90
15
120
60
12
9
150
AP
30
256 x CPE
6
AP
AP
AP
256 x CPE
3
AP AP
180
0
AP
0
AP
256 x CPE
256 x CPE
210
330
240
300
270
3 options for user interfaces
100 BaseT
100 BaseT & E1
100 BaseT & 2x POTS
Copyright Cambridge University
Network Interface
SDH / ATM
Network
3
Research Project 2
• Space-Time Diversity Coding Combined with
Equalisation for MIMO Wireless Channels.
Mr. Cameron B Shaw BEng(Hons), MEng
(PhD Student), 15 months remaining
EPSRC grant in collaboration with Lancaster
University (Professor Honary) and MOD
(Ministry Of Defence)
4
The world of mobile communications
•Have you ever heard the phrase “the future is
here today”? Well, in the case of mobile
communication technologies, this phrase is true.
•However, it is not yet fully realized.
5
Contents
• Introduction
• Challenges in the Migration to Future
Mobile Systems
• 2G, 3G and 4G wireless systems
• Research Challenges:
– Mobile Stations, Systems, Services
• Conclusion
6
Introduction (2)
• 2G Mobile Systems
– GSM, IS-95 and CDMA one carry speech and low bit
rate data
• 3G Mobile Systems
–
–
–
–
–
–
–
Higher data rate
Multi-media systems
GPRS
IMT 2000
Bluetooth
WLAN and HiperLAN
Developing new standards and hardware
7
4G Mobile Systems (2006)
•
•
•
•
•
•
•
Access, handoff
Location coordination
Resource coordination to add new users
Support for multicasting and Quality of Service
Wireless security and authentication
Network failure and backup
Pricing and billing
8
The world of mobile communications
•Out of a world population of 6.32 billion people,
approximately 1.12 billion, or 1 in 6, have a mobile phone
and 71.6% are GSM customers
•Total Operator revenues for 2006 have been estimated
to be over $100 billion for Western Europe
•China Mobile with over 100 million customers are
connecting 2 million new customers each month
•About 2 billion people in the world have yet to make a
phone call and it is likely that when it happens it will be on
a mobile phone rather than a fixed line
9
What is Wireless Data?
•
•
•
•
•
•
•
•
Paging/short messaging
Vehicle tracking and dispatch
Transaction processing
Warehouse inventory
Subscriber information services
Wireless remote access to host
File transfer to/from laptop,J2ME
Wireless Internet access and Video
Teleconferencing
• Browsing on Laptops, PDAs ,Phones
• Messaging,E-mail,SMS,Fax,Voice,Pager
10
Mobile Computing Systems
• Future Mobile Systems
– Personalised Services providing stable system
performance and Quality of Service (QoS)
– Challenges:
• Mobile Station
• System(Networks)
• Service and standards
Mobile VCE (www.mobilevce.com), MIRAI and DocoMo
VCE = Virtual Centre of Excellence in Mobile and Personal Communication
11
Mobile Computing Systems
• Some key features of Future Mobile Systems
– High usability:
• Anytime, anywhere and with any technology (all-IP
based heterogeneous networks)
– Support for Multi-media Services at low
transmission cost
– Personalisation(having human characteristics)
– Integrated Services
12
Everything is IP
13
Research Challenges
• Mobile Station
– Multimode user terminals(multi-functional,software upgrades)
– Wireless system discovery(searching for wireless system)
– Wireless system selection(suitable technology)
• System
–
–
–
–
Terminal Mobility(to locate and update the locations)
Network infrastructure and QoS support
Security, performance and complexity
Fault tolerance and Survivability
• Service
– Multi-operators and billing system
– Personal mobility
– New Applications
14
Mobile Stations
Multimode user Terminals: To design a single user terminal that can operate in different
wireless networks
An ideal software radio system
• New coding/interleaving/diversity/equalisation/SISO channel/MIMO channels
• Multicarrier, spread spectrum and antenna solutions
• Adaptive coding modulation, detection, synchronisation and automatic repeat request
• Multimedia protocols, new access,timing control and QoS
• New applications
• A software radio approach can be used so that the user terminal adapts itself to the wireless
• interface
15
Technical Challenges
• Low-Power/Low-Cost Implementations
• Scarce Radio Spectrum
• Radio Channel Characteristics
- Limits on Signal Coverage
- Limits on Data Rates
• Efficient Network Architectures and Protocols
• Seamless Internetworking
• Authentication and Security
16
Radio Environment
•
•
•
•
•
•
Path Loss
Shadow Fading
Multipath
Interference
Infrared Versus Radio
Doppler Spread
17
Link Performance Measures Efficiency
• Spectral Efficiency
-
a measure of the data rate per unit bandwidth for a given bit error
probability and transmitted power
• Power Efficiency
-
a measure of the required received power to achieve a given
data rate for a given error probability and bandwidth
• Throughput/Delay
18
HOW DO WE OVERCOME THE LIMITATIONS
IMPOSED BY THE RADIO CHANNEL?
•
Flat Fading Counter measures
- Fade Margin
- Diversity
- Coding and Interleaving
- Adaptive Techniques
• Delay
Spread Counter measures
- Equalization
- Multicarrier
- Spread Spectrum
- Antenna Solutions
19
EQUALIZER TYPES AND STRUCTURES
20
Turbo Equalisation
AWGN
data
Convolutional ‘outer’
code
I
ISI Channel
I
Estimated data
SISO ‘outer’ decoder
I-1
SISO Equaliser
Turbo Equaliser
21
MIMO Turbo Equalisation
Data Model: 2-User, 2-Path, 2-Antenna (Example)
Space Domain Sampling
h11(1)
h11(0)
h12(0)
b1(n)
h12(1)
r1(n)
User 1
h21(0)
h21(1)
b2(n)
User 2
h22(0)
h22(1)
r2(n)
 h ( 0) 
 h (1) 
r (n)   11 b1 (n)   11 b1 (n  1)
h12 (0)
h12 (1)
 h ( 0) 
 h (1) 
  21 b2 (n)   21 b1 (n  1)  n(n)
h22 (0)
h22 (1)
 h1 (0).b1 (n)  h1 (1).b1 (n  1)
 h 2 (0).b2 (n)  h 2 (1).b2 (n  1)  n(n)
22
Algebraic-Geometric Codes
•
Algebraic geometry is a powerful tool for constructing codes with good parameters
e.g. Hamming distance, code rate and large code length.
•
Very long codes can be constructed by choosing curves containing many points.
Reed Solomon codes are constructed from a line, which has less points, and
hence they are much shorter than AG codes
•
There is almost no limit to the number of AG codes that can be constructed from a
variety of different classes of curve. There are not many Reed Solomon codes.
•
AG codes perform better than Reed Solomon codes for high code rates over
smaller finite fields and are suitable for application in mobile communications and
storage devices
•
Further investigation is needed into constructing new codes from different classes
of curves and the development of low complexity decoding algorithms for future
hardware implementation.
23
Algebraic-Geometric Codes
Hermitian curves can be used to construct very long codes:
Example: C(x,y) = x5 + y4 + y, defined over GF(16) gives codes 64 symbols long. A
Reed Solomon code over GF(16) is only 15 symbols long
1.E+00
1.E-01
(64,39)AG, R=0.61
(15,9)RS, R=0.6
Uncoded BPSK
1.E-02
1.E-03
BER
•
1.E-04
1.E-05
1.E-06
-4
-3
-2
1.E-07
-1 0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23
Eb/N0 , dB
24
Construction of LDPC codes for Application with
Broadband Communication Systems
• LPDC codes are a class of Block codes that perform very close to
Shannon limit.
• Uses efficient encoding and iterative decoding schemes to achieve low
latency .
• Highly parallel nature and low complexity of decoding algorithm results
in fast iterative decoding and less complex Hardware architecture.
• Better performance using equalisation techniques in dispersive
MIMO/SISO ISI fading channels.
•Performance is drastically improved by concatenating with Space time
Codes
•Suitable for high data rate applications.
25
SUI-3 LDPC-QPSK With SRK Equalisation
26
Broadband Fixed Wireless Access (BFWA)
systems
• Aim of BFWA is to deliver broadband data services to homes and
businesses in a flexible and efficient manner.
• Main driver is to provide Internet access for applications such as E-mail,
web-browsing, file downloading and transfer, audio and video services
over Internet.
• In BFWA systems, radio signal travels via multipath from transmitter to
receiver antennas. Multipath propagation causes intersymbol interference
and degrade the system performance.
• Turbo equalization is a powerful technique to remove the effect of
intersymbol interference.
27
Comparison of different equalisation schemes in BFWA
systems
28
MIMO Channels for BFWA Systems
• Use MIMO space-time coding to increase the capacity of
BFWA system.
• Signals from different antennas can be separated through
orthogonal design, such as Alamouti algorithm.
• When used over frequency selective channels, a channel
equalizer has to be used at the receiver along with the spacetime decoder.
• STBC can be applied in conjunction with OFDM which
converts the frequency selective channel into a set of
independent parallel frequency-flat subchannels. The
Alamouti scheme is then applied to each subcarrier.
29
Space-Time Ring Trellis Coded Modulation
g11(x)
ST-Ring TCM Decoder
r1(x)
Tx1
g21(x)
QPSK
Demodulator
State = 0
00
32
33
State = 1
g12(x)
22
Tx2
g22(x)
QPSK
Demodulator
32
21
10
13
r2(x)
20
State = 2
21
10
13
22
20
03 01
12
31
22
02
03 01
30

33
33
02
11
State = 3
00
00
11
12
31
23
30
11

The uncorrelated fading
channels are used to provide
diversity
Very good results can be
obtained with just 2 tx & 2 rx
antennas.
23
1.E+00

1.E-01
BER
1.E-02
1.E-03
Indoor (21/3)
Indoor (Delay diversity)
Indoor (212/31)
Pedestrian (21/3)
Pedestrian (Delay diversity)
Pedestrian (212/31)
Vehicular (21/3)
Vehicular (Delay diversity)
Vehicular (212/31)
Indoor (2103/132)
Pedestrian (2103/132)
Vehicular (2103/132)
1.E-04
1.E-05
-4
-3
1.E-06
-2 -1 0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
SNR (dB)
Higher coding gains achieved and error
floors removed by using higher state
codes.
 Higher coding gains are achieved and
error floors removed by using higher state
codes.
 Cannot fully recover vehicular channel
data. Equalisation is needed.
30
Maximum a-posteriori Turbo Equalisation

Realistic channel models are created to properly test
the mobile communication systems.
 Indoor, pedestrian and vehicular scenarios are
simulated based on actual measured results from
urban mobile radio channels.
0
-10
-20
-30
-40
-50
-60

Over realistic channels (such as the urban mobile
channel) the intersymbol interference produced
needs mitigation to improve performance.
 The goal of equalisation is the cancellation of the
Inter-Symbol Interference (ISI), or equivalently the
flattening of the radio channel’s frequency response
 Turbo equalisation combines decoding and
equalisation by converting the channel into a type of
‘code’ which can then be iteratively decoded with a
symbol-by-symbol decoder.
5
10
15
20
recieved
message (y)
a priori
information
Lext (ct)
MAP
Equaliser
25
30
a posteriori
information
L(ct|y)
- 
extrinsic information

Lext (ct)
+
Lext (ct|y)

extrinsic information
 -
+
L(ct)
a posteriori
information
MAP
Decoder
Lext (ct|y)
a priori
information
31
Mobile Station
Wireless system discovery
GSM
GPRS
Via PC server
CDMA
Via PDA
Scanning…
Via smart card
OTA
UMTS
WLAN
Via Memory
card
Available Systems
Way to download Software
• To discover available wireless systems by processing the signals sent from different wireless
systems (different access protocols)
32
Mobile Station
Wireless System Selection: Selection of the most suitable
technology for a particular service
• We can choose any available wireless device for each particular
communication session (fit to user QoS requirements)
• Right network selection can ensure the QoS required by each Session Initiation
Protocol (SIP) messages.
• Adequate knowledge of each network is required before a selection is made
Location information of the source mobile nodes, available networks of both
mobile nodes and user preference are all taken into account in the selection
when a mobile node makes a call to another mobile node
33
System
Location Management
Terminal Mobility
Terminal moves between
subnets
The system tracks and locates a
mobile terminal for possible
connection
• To locate and update the locations of the terminals in various
systems
• Location Management: Information about the roaming terminals
such as original and current located cells, authentication
information and QoS
• Service Mobility: Keep same service while mobile
34
System
• Enhanced Mobile IPv6 Schemes
Figure shows an example of horizontal and vertical handoff
UMTS coverage
GSM coverage
Vertical handoff
Horizontal handoff
WLAN coverage
• Main problems: - handover performance
- handover failure due to lack of resources
- authentication of redirection
35
System
Problems
• Real-Time Multimedia Services that are highly time-sensitive
• It is unacceptable if the MIPv6 handoff process significantly
degrades system performance.
• New handoff decision policies and new handoff algorithms.
The terminal moves from one cell to another (two different
wireless systems e.g. WLAN and GSM).
36
System
Network Infrastructure and QoS Support
• To integrate the existing non-IP-based and IP-based systems
• Non-IP-based systems (voice delivery) e.g. GSM, CDMA2000
and UMTS
• IP-based systems (data services) e.g. 802.11 WLAN and
HiperLAN, 802.16/802.20
Problems: Integration, QoS guarantee for end-to-end
time-sensitive (3GPP)
37
System
Security
• The heterogeneity of wireless networks complicates the security
issues
• 2G/3G have been widely studied
• The key concern in security designs for 4G networks is flexibility.
The key sizes and encryption and decryption algorithms of
existing schemes are also fixed.
• Reconfigurable security mechanisms are needed (Tiny SESAME)
• Modifications in existing security schemes may be applicable to
heterogeneous systems
38
Mobile Station – GSM Functional Architecture
Radio Subsystem
Points of reference
Base Station Subsystem (BSS)
Network and Switching Subsystem
(NSS)
Operation Subsystem (OSS)
MS
VLR
BTS
AuC
BSC
HLR
MS
OMC
BTS
MS
BSC
MSC
Radio Interface
BTS
Interface to other networks
BTS-BSC Interface
Transition to ISDN, PDN, PSTN
EIR
39
System
Fault Tolerance and Survivability: To minimise the failures and
Their potential impacts in any level of tree-like topology
Reliability, availability and survivability of the network
• A cellular wireless access network is typically designed as a tree-like topology
that has several levels (device, cell, switch and network levels)
Problems: Any level fails (hardware/software), all levels below will be affected
• Consideration, power consumption, user mobility, QoS management, security,
system capacity and link error rates of many different wireless networks.
• The first is to use hierarchical cellular network systems
The second is to use collocated or overlapping heterogeneous wireless network
40
Services
Multiple Operators and Billing System
• More comprehensive billing and accounting systems are needed (different types of
services)
• Multiple service providers
• Operators need to design new business architecture, accounting processes and
accounting data maintenance.
• Future Wireless Networks support multimedia communications, which consists of
different media components with possibly different charging units
• This adds difficulty to the task of designing a good charging scheme for all customers
• Scalability, flexibility, stability, accuracy and usability
41
Services
Personal Mobility: different terminals, same address
• The movement of users instead of users’ terminals and involves the provision of
personal communication and personalised operating environments
At 10.00am a video message is sent
to Mary. She reads the message using
her PC in her office
At 6.00pm another video
message is sent to Mary.
She reads the message
using her PDA when
driving her car.
At 8.30pm a video message
is sent to Mary again. She
reads the message using
her laptop PC at home
Laptop computer
Pen computer
42
Services
Personal Mobility
• Mobile-agent
based infrastructure is one widely studied
(Agent Support for Personal Mobility)
• Agents act as intermediaries between the user and the
Internet
43
Application
• Mobile computing in a Fieldwork Environment
Ecologists, archaeologists, computer scientists
and engineers
• Communication and Ad Hoc Networking in the
field, prevent disaster, reduce crime and terrorism
• Health and Education
• E-Commerce, E-Business, E-Government
• Partnership Universities
• Entertainment, games, smart home
44
Improving the way we work
•The way and means that people use to
communicate is changing
•People need the ability to work anywhere,
anytime, anyplace
•Best Value, being effective and efficient
•Work is an activity not a building or place
45
Conclusions
• In this presentation research challenges in the
emigration to future networks are studied and
described
• The challenges are grouped into three
aspects: Mobile Station, System and Service
• Wireless technologies used to decrease crime
and prevent emergency disasters and
terrorism
46
Conclusions
• The challenges were identified, such as
multicarrier user terminals, wireless system
discovery, terminal mobility, QoS support and
business opportunities
• Mobile communication impact in urban/rural
areas
• Project of Innovation for job creation using
wireless technologies
47