INVITED PAPER
IETE Technical Review
Vol 23, No 4, July-August 2006, pp 253-265
Fourth Generation (4g) Networks:
Roadmap- Migration to the Future
SAYAN KUMAR RAY
Department of Computer science & engineering, Heritage Institute of technology
Kolkata 700107, India.
email: raysk@rediffmail.com
and
ITI SAHA MISTA
ETCE Department, Jadavpur university, Kolkata 700 032, India.
email: itimisra@cal.vsnl.net.in
The mobile communication generations has traversed a long way through different phases of evolution since its birth early in the 1970s.
the steady global boom in the number of mobile users each year has periodically spurned the development of more and more
sophisticated technologies trying to strike the right chord primarily in terms of provision of seamless global roaming, quality services and
high data rate. today numerous different generation technologies with their individual pros and cons are existing globally. the coming era
of 4g systems is foreseeing a potential smooth merger of all these heterogeneous technologies with a natural progression to support
seamless cost-effective high data rate global roaming, efficient personalized services, typical user-centric integrated service model, high
Qos and overall stable system performance. However, every step in such technological advancements presents huge research
challenges. this article aims to focus upon some of these potential challenges along with different proposed feasible and non-feasible
solutions in the areas of mobile terminals and users, mobile services, mobile and wireless access networks, and communication, in order
to give an indepth view of the next-generation communication systems.
1.INTRODUCTION
IMAGINE a situation where while traveling in a vehicle in a
large metropolis with a small handheld wireless device, a
person can seamlessly visualize the entire environment ahead
(like buildings, streets, highways, and shopping malls) and, at
the same time can track other vehicles that may come in his
way to avoid any accidents. Era of next generation of intelligent
wireless systems ahead, effectively termed as 4G, is slowly
taking shape to make such highly intelligent, user-focused
personalized service like virtual navigation a reality. Different
industry and research organizations worldwide like NTT
DoCoMo, QualComm, Nokia, Ericsson, Motorola, Alcatel,
WWRF, ITU, IEEE, Mobile VCE and 4GW-PCC, to name a few,
are all set to make 4G wireless systems hit the commercial
market by 2010.
Network systems evolution starting way back at 1970 when the
design of the analog-voice-oriented First Generation (1G)
systems began. The transition to digital voice and data-oriented
Second Generation (2G) systems in 1991 marked the beginning
of a multi-service platform from the previous mono-service era.
Low bit-rate data and mono-media systems like GSM,
cdmaOne, IS-95 and TDMA are still existing in multiple global
locations. The 2.5G systems (like GPRS), an interim step
between 2G and 3G, provided enhanced channel capacity,
higher data rate and throughput and optimized packet-data
transmission enhancing Internet access from different wireless
devices. The commercialized transition to 3G systems in 2002
marked the beginning of a truly multimedia era [1] where more
person-to-machine interactions than person-to-person
interactions are prevalent. Core packet networked systems like
cdma2000 and WCDMA provide higher channel capacity,
broadband data up to 2 Mbps, high speed multimedia
transmission and global roaming across a cellular network.
___________________________________
Paper No 36-C; Copyright © 2006 by the IETE..
241
254
IETE TECHNICAL REVIEW, Vol 23, No 4, 2006
This era marked the beginning of full-fledged huge revenue
generating multimedia Internet applications and e-commerce.
However, with the huge worldwide increase in the number of
mobile users each day and with emerging demands like totally
user-centric services, high speed streaming Internet multimedia
services (telemedicine, tele-geoprocessing, virtual navigation
and VoIP), seamless global roaming with ubiquitous coverage
and unhampered QoS support, 3G systems have started
showing their limitations with bandwidth availability, spectrum
allocation, air interference standards and lack of seamless
transport mechanisms between different networks. Moreover,
different short range communication systems like WLAN,
Bluetooth and HIPERLAN as well as broadcast communication
systems with different features spanned during this time each
with its own merits and demerits targeting different types of
users and different service types [2] making the situation more
complicated for 3G systems.
dynamic and significantly handle the limitations of 3G systems.
So, consolidated solutions that can seamlessly operate on the
multiple, diverse networks migrating to the 4G environment
fulfilling the plethora of nextgeneration dream visualizations on
implementing a transparent open wireless architecture (OWA),
should be imperatively designed. This obviously invites new
challenges on every step and researchers worldwide face an
uphill task of designing suitable solutions. Figure 1, shows such
a 4G vision.
b. Migration to the Future
2.OVERVIEW OF THE POTENTIAL RESEARCH
CHALLENGES
These limitations and drawbacks have generated the
requirement for an universal framework encompassing all the
existing heterogeneous wired and wireless systems in use. This
IPv6-based potential 4G framework, commonly described as
MAGIC [3] (Mobile multimedia, Anytime anywhere access,
Global mobility support, Integrated wireless solution and
Customized personal service), would be highly
This paper is divided into four sections: introduction, overview of
the potential research challenges, highlighted research
challenges and conclusions. We have identified a whole lot of
probable 4G research challenges and have grouped them under
four research areas: mobile terminals and users, mobile and
wireless access networks, mobile services, and communication
challenges.
The different potential challenges are summarized in Table 1.
Section 3 discusses in details on few of the highlighted research
challenge areas. Table 2 represents the abbreviation used in
this article.
Fig 1 4G vision 2010
255
RAY & MISRA : 4G NETWORKS
TABLE 1 Summary of the different 4G research challenges
Aim
Vitally important
problems
challenges
and
Mobile Terminals and Users
Multistandard/Multimode User Terminals
A single wireless user terminal should be
designed, which can automatically operate
in
different
heterogeneous
access
networks.
Problems related to high cost,
limitations in terminal size, high power
consumption, high circuit complexity,
and
unimproved
analog-to-digital
converter (ADC) performance in
software defined radio (SDR)-based
implementations.
The different software downloading
schemes related to reconfigurable
terminals have got their own problems.
Automatic Network Tracking and Selection
A roaming user in a heterogeneous
environment should be able to automatically track and select the available
underlying wireless network. In each
communication session for a particular
service the most appropriate underlying
network should be chosen.
The different software downloading
schemes related to reconfigurable
terminals have got their own problems.
Provision of personalized services through
different
personalized
operating
environments to the same address.
Confusions regarding the choice of
either MIP or SIP as the core protocol
and also whether the ideal framework
be Network layer-based or Application
layer-based.
Streaming multimedia based services:
To provide very high speed (streaming)
video applications ensuring high QoS and
bandwidth usability.
UDP suffers from acute congestion
related problems, so TCP is gaining
importance as the ideal transport layer
protocol
for
video
streaming.
Opportunistic scheduling based video
streaming needs more attention.
Multioperator-oriented
system
Users subscribing to multiple service
operators for multiple different services
should ideally be charged a single bill
covering all the different billing schemes
involved. Users need not worry about the
different billing schemes.
Designing
new
packet-switched
oriented billing and accounting policies
for 4G users. From customers and
operators points of view handling
issues like QoS dependant charging,
real-time billing information support,
interworking prepaid systems support
and billing support to diverse service
accesses as well as cost calculation
flexibility, IP traffic billing support,
instant discontinuation of service if any
fraud
is
detected
and
correct
maintenance of customer’s profile, are
the real problems.
Users should be able to roam freely and
seamlessly across the various global
geographic locations. Location and
handoff managements should be done
properly.
Maintaining high data rate, best
possible QoS, reducing packet loss and
signaling overhead are the primary
challenges. The system throughput
should be increased with low handover
latency. In location management,
issues like optimally handling diverse
user calling and mobile patterns, and
better
inter-network
location
coordination
should
be
handled
properly. In handover
Mobile Services
Personal
Mobility
and
Session
intelligent
billing
Mobile and Wireless Access Networks
Seamless Terminal Mobility management
256
IETE TECHNICAL REVIEW, Vol 23, No 4, 2006
TABLE 1 (Contd...)
Vitally important
problems
Aim
challenges
and
Mobile Terminals and Users
management, challenges like reducing
call droppings and disruptions, reducing
handover time, and optimizing effective
call completion time need more
attention.
Integration and Interoperability of diverse
networks
Seamless integration and interworking of
the multiple heterogeneous existing and
new wireless access technologies to
provide unhampered connectivity, fully
broadband access, unhampered global
roaming, perfect QoS and user controlled
services.
Problems owing to diverse nature of the
constituent access technologies in
terms of varying bit rates, bandwidth
allocation,
channel
characteristics,
fault-tolerance levels and handoff
management mechanisms are the key
ones.
QoS Maintenance
Unaffected QoS should be provided
between the end users and end-to-end
services.
Significant overhead problems still
persist in different QoS schemes like
traffic control, dynamic resource
reservation and QoS renegotiation.
Ideal mixing of packet level and nonpacketlevel QoS mechanisms should
be done.
Dependability
To ensure fully fault-tolerant
survivable 4G systems.
and
Ideal fault discovery, notification service
& recovery schemes should be
designed to minimize failures and their
potential impacts on any level of the
hierarchical topologies of the 4G
networks.
Security aspects
Stronger end-to-end security services are
needed to get credentials of the
communicating
parties
(residing
in
different
environment)
authenticated
without even knowing each other.
Stronger levels of protection is needed
against eavesdropping, malicious calls,
and service denials. Adaptive and
lightweight security mechanisms should
be implemented.
Routing
To implement intelligent packet and call
routing techniques enhancing system
performance.
Lowest Power Consumption and best
QoS are the key attributes to be
addressed while defining a “best path”
routing technique. Efficient global and
ad-hoc
routing
techniques,
and
semantic routing based content delivery
techniques need to implemented. Mesh
network routing techniques are also
inadequately addressed.
Protocol Requirements
Unified networking protocol stack and
vertical protocol integration mechanisms
adapting to the 4G constituent networks
requirements should be designed.
Efficient 4G mobile network and
security
protocols
capable
of
dynamically adopting to variant channel
conditions and security requirements
should be implemented. New ad-hoc
protocols for self-organization to be
designed.
To enhance spectral efficiency and
channel capacity with wide area coverage
providing cost-effective very high data
rate. Increasing bandwidth usability and
minimizing multi-path effects.
Handling the different drawbacks
related to Orthogonal Frequency
Division Multiplexing (OFDM)-based air
interfaces, Ultra-Wideband (UWB) radio
transmission technology (UWBRT) and
smart antenna technology.
Communication Challenges
Enhancing spectrum efficiency and
channel capacity along with ubiquitous
coverage.
257
RAY & MISRA : 4G NETWORKS
3.HIGHLIGHTED RESEARCH CHALLENGES
Due to space limitation, we have focused our detailed
discussions on five most important research challenge areas. A
bunch of important proposed potential solutions to those
challenge areas are discussed and new as well as less
accessed challenges demanding further research attentions are
pointed out under sub-sections 3 (A), (B) and (C).
A. Mobile Terminals and Users
A.1. Automatic Network tracking and selection
Multiple heterogeneous wired and wireless networks each
having own its unique features and offering unique services
constitute the 4G environment. For efficient seamless global
roaming across the 4G OWA, users with multimode terminals
should be
automatically able to track and select a particular target wireless
system supposedly the most appropriate one in a specific
location offering the needed service. Choosing the best suitable
network is required to optimize the system performance, QoS,
resources accessibility, costs and service capabilities in that
particular session [2,3]. Suppose an user visits a shopping
center in the city where the wireless access network is WLAN or
WLL to get some vegetables Automatically his reconfigurable
terminal tracks and connects to the available local high-speed
wireless access system. Afterwards, when the user is driving
across a highway, say, his same terminal again selects and
automatically switches to the appropriate wireless mobile
network, say GPRS or CDMA2000. However in this entire
network selection mechanism transparent to the end users, the
mobile terminal plays a significant role.
258
IETE TECHNICAL REVIEW, Vol 23, No 4, 2006
Based on user preferences (user decides the location to visit
and services to accept at any particular time) the algorithms on
the mobile terminals detect and select the most suitable
underlying access network that provide better link layer
connectivity at that particular location and reconfigures itself as
per the chosen network’s needs and regulations. Figure 2 shows
how the promising 4G feature of automatic network tracking and
selection will be fruitful to the users.
Current State of Research: The feature of on-the-fly automatic
network tracking and selection is complicated in 4G
environments due to its heterogeneous nature. In this context,
one of the proposed solutions is Access Network Selection [3]
where for each particular communication session the multimode
terminal collects adequate information (like user subscription,
supported service types, costs, QoS, bandwidth requirements,
coverage and pricing policies) of the available underlying
networks and stores them in the Service Platform (SP). The
decision of which network to choose depends on the stored
information. However limited availability or non-availability and
inaccuracy in gathering the underlying network related
information are the major drawbacks of this approach. Unlike
this approach where user preferences on network selection is
optional, the Adoptive Service Access Solution (ASAM) [4]
significantly considers user preferences while selecting a
particular access network. Reference [5] describes a call
admission policy-based approach, which selects the least loaded
available network in any particular situation. However this
approach demands for more accurate load balancing approach.
In spite of all these research activities in this domain, till date the
most successful approach is the use of software radio devices
that scan the available networks and, after downloading the
appropriate software(s) reconfigure themselves as per the
selected network features. Different reconfiguration and
downloading modes exist each having its own advantages and
disadvantages. Few of them proposed in [6] are: (i)
Reconfiguration over the air: In this a dedicated channel
bridges between user terminal and base station facilitating
information exchange and error-free downloading of the
requested software module. However this approach suffers from
the problems of handling the varying bandwidth requirements
over narrow-band channels and also of realistically allocating a
dedicated physical channel for downloading. (ii)
Reconfiguration using advanced SIm Cards: Here based on
the prior stored information regarding the reconfigurable
software modules on the smart cards, downloading and
configuring of the appropriate services on the terminals take
place on insertion of the cards on the terminals. However this
approach is mostly suitable for stand-alone terminals.
(iii) Internet Download: Here software modules downloaded
from Internet by means of a modem, a PC and a terminal are
reconfigured on the user’s terminal. (iv) Over-the-air (OTA)
download [7]: In this approach multimode user terminals
constantly monitor the predefined broadcasting global pilot and
download channel (GPDCH) and, on detection of any available
network, the terminals decide whether to switch or not. This
approach suffers from slow speed of GPDCH and long
downloading time.
Possible Research Directions: Automatic network tracking and
selection in the 4G context is a primary research challenge. The
idea of seamless global roaming is much dependent on this.
Needs are there in framing out an universally accepted network
tracking and selecting solution, which on the basis of optimal
resource usage, QoS requirements and user preferences would
select the most appropriate available network. In this regard
problems discussed during the different downloading schemes
should be taken care of. However, it’s a big challenge to gather
adequate knowledge of each network before any selection is
made. To conclude in brief, future researches should focus on
the problem areas related to: Discovering the available access
networks and their respective points of presence (PoPs),
selecting the proper authentication identifier for each PoPs and
efficiently figuring out the best possible AAA routing and payload
routing means for seamless exchange of the authentication
conversation and payload packets between the endpoints.
b. Mobile Services
b.1. Personal and Session Mobility
In 4G eras it is critical to ensure that users get convenient
access to the services needed at any given situation. In this
context user mobility has become an important aspect in the
design of next-generation wireless communication systems.
Researchers have focused on three such mobility-related
research areas: terminal mobility deals with mobility of users
having a single device (discussed under sub-section 3.C.1),
session mobility deals with user in a PAN having multiple
personal devices to provide a live session and personal mobility
concentrates on provision of personalized operating
environments for users along with user movements [2]. In
personal mobility a service required by the user will be
instantaneously delivered irrespective of the user’s location,
device and device location, operator/provider domain and, type
of network. So, unlike terminal mobility, session and personal
mobility concentrate more on user movements rather than
terminal movements.
259
RAY & MISRA : 4G NETWORKS
Current State of Research: Insignificant volume of research
works related to personal mobility frameworks for 4G systems
have taken place till date. In this respect, two mobile agentbased personal mobility frameworks need mentioning. These
agents bridge the users and the Internet. The first of these
integrated personal mobility architectures proposed by Thai et al
[9], uses mobile agents and signaling protocols to facilitate
significant optional usage of the communication channels. This
improves the system usability and allows accessibility of
required services anytime globally. However though integrating
personal communication and personalized operating
environment, this framework suffers from considerable cost
overhead. The second framework facilitates users providing
assistance in browsing, accessing emails, accessing files and in
FTP related mechanisms [10]. Some researches on Session
Initiation Protocol (SIP)-based frameworks supporting both
personal and session mobility by augmented signaling
mechanisms are also being carried out.
Possible Research Directions: Both personal and session
mobility have drawn limited research attentions until now and
much needed to be done. The whole gamut of works done till
date towards a complete solution between the heterogeneous
nature of the 4G systems and the personal and session mobility
management issues is yet to achieve any significant break
through.
Major confusions regarding the choice of Mobile IP (MIP) or SIP
as the core protocol and whether the ideal framework should be
Network Layerbased or Application Layer-based in case of
personal and session mobility still persist with each having its
own pros and cons.
b.2. Streaming Multimedia Based Services:
4G wireless multimedia communication aims at efficient
transmission of streaming data for video applications such as
telemedicine, multimedia video conferencin, 3D virtual reality,
virtual navigation, which account for large portion of future traffic,
and needs overcoming the constraints like scarce system
resources, high QoS and bandwidth requirements, variations in
delays and packet loses [11]. Bursting and streaming video
services are the two types of video services to have gained
popularity in 4G systems. However, while memory requirement
for bursting is much large, streaming lacks in bandwidth
usability. So implementation of new streaming video application
schemes making optimum use of the available bandwidth in
limited available memory is the research activity of the future.
Choice of appropriate protocols is important in this context. UDP
and TCP are the two important transport layer protocols for
video streaming. However UDP suffers from acute congestion
related problems (like congestion collap and unfair bandwidth
allocation), which may be more conveniently handled by the
TCP.
Fig 2 (a) User is confused with the underlying technology to choose; (b) Multimode terminal helps him to automatically track and select the available
technology appropriate for his service
260
RAY & MISRA : 4G NETWORKS
Current State of Research: In this respect, an efficient scheme
facilitating video streaming at very high data rate has shown that
significant improvement in cellular capacity and video quality can
be achieved for closed-loop rate controlled encoded video [12] in
a cellular Multi-Code CDMA (MC-CDMA) wireless system using
TCP as the transport layer protocol and simultaneous MAC
Packet Transmission (SMPT) techniques. For open-loop
encoded video, however, this scheme failed to prove its
suitability. Achieving high performance gain is an important for
streaming video applications. Use of opportunistic scheduling
techniques proved fruitful in this regard. Reference [11]
considers both channel variation and burstiness of video traffic
and shows that significant performance gain for streaming video
applications is still achievable. Very high quality web service,
achievable through the use of Java-based i-mode and i-appli
programs, are suitable for e-commerce and mobile banking
applications.
Possible Research Directions: Work done till date on
opportunistic scheduling based video streaming over wireless
networks is negligible and needs significant research attention.
More TCP friendly video streaming schemes over wireless
networks are desirable to make TCP an automatic choice as the
transport layer protocol over UDP because with enhanced
streaming video applications all set to flood the coming
generation of wireless networks UDP may lead to the instability
of the Internet [12]. On another front, proper management of
bandwidth and efficient schemes for providing quality QoS
between the end-systems are two very important criteria for
quality multimedia services. Issues like proper traffic control,
admission control and QoS signalling schemes require more
attention in this regard.
C. Mobile and Wireless Access Networks
C.1. Seamless terminal mobility management
Users should be able to roam freely and seamlessly across the
geographic boundaries of different 4G constituent networks
maintaining high data rate, best possible QoS and satisfactory
connectivity with the application servers. Multimode terminals
capable of automatically tracking and selecting the appropriate
available underlying network play an important role in this
context. Ample research activities in this field have taken place
with prime concerns about reducing packet loss, signaling
overhead and handover latency
apart from increasing the throughput. IPv6, providing link-layer
independent mobility management solutions, is unanimously
accepted as the prime backbone of the future 4G core network.
Further protocol advancements in this context have implemented
Mobile IPv6 (MIPv6) and Hierarchical Mobile IPV6 (HMIPv6).
Effect of other protocols like Location Independent Network
Architecture for IPv6 (LIN6), Transmission Control Protocol
(TCP), User Datagram Protocol (UDP), Stream Control
Transmission Protocol (SCTP), Datagram Congestion Control
Protocol (DCCP), Multiple Address Service for Transport
(MAST), Session Initiation Protocol (SIP) and Dynamic Domain
Name System (DDNS) at the different layers are also being
studied [13] in depth. Slow increase in the number of effective
Personal Area Networks (PANs) have urged more research
activities in tackling issues related to mobility management of
roaming networks [14]. In this paper we have focused our
discussions on location management and handoff management
scenarios as the primary challenges related to seamless global
terminal mobility.
C.1.1. Location Management
The process of tracking and maintaining the exact whereabouts
of wireless terminals by the underlying system for possible
connections when powered-on, powered-off or on the move is
location management, which is a two phase technique. Location
tracking deals with tracking the exact location of the terminals
and location information storage [15] then maintains other
location information like QoS capabilities, authentication and
traffic. Roaming through diversified range of networks have
given rise to the need for efficient and integrated location
management schemes.
Current State of Research: Till date many effective location
management schemes have been proposed. An integrated
location management architecture for inter-network roaming is
discussed in [15]. Here the underlying networks can coordinate
amongst themselves, track whether terminals are located within
coverage and thus route incoming packets/calls meant for
individual terminal. Though ubiquitous coverage and high
dependability are the biggest advantages here, yet this scheme
may suffer from enhanced cost of complicated programmable
devices and intelligent hardware. Location of the coordinating
servers in the underlying networks also play an important role in
handling the location management problems. Proposed location
management architectures may be centralized, distributed or
hybrid depending on whether all the underlying coordinating
sub-networks are centrallymanaged (entire system’s location
management
261
RAY & MISRA : 4G NETWORKS
decisions are coordinated by a central server) or individuallymanaged (each sub-network manage its own decision) or part
centrally part individuallymanaged (location management
decisions jointly taken by central server and individual networks).
Though the centralized scenario seems optimal but it needs
close inter sub-network coordination and chances of signaling
bottlenecks are always there. The second approach has the
disadvantage of higher update cost but has much less paging
overhead than the third.
Possible Research Directions: Research analysis has shown
that nearly all the proposed Transport layer protocols for
wireless mobility management like TCP, UDP, SCTP and DCCP
have proved ineffective in handling problems related to location
management. However, nearly all Network layer and higher
layer protocols [13] supports efficient location management
features and might play fruitful roles in future location information
management researches on issues like location estimation,
location prediction and location privacy. Other related challenges
which needs attention are provision of better location
coordination among the different diverse sub-networks, and
optimally matching call to mobility ratio and location update rate.
Lastly, special mentioning is required about the challenges
related to managing the location of future mobile software
modules that will play an important role in the next generation
network era.
3 [2] shows the concept of horizontal and vertical handover
mechanisms of a mobile terminal. Problems like provision of
enriched QoS support, reducing call droppings and disruptions,
reducing handover time, ensuring correct handover completion
time, and optimizing effective call completion time are tricky to
handle and all the IP-based advanced protocols should be
thoroughly ensured of meeting the challenges. Current State of
Research: Global roaming with multimode terminals is supported
by IPv6 for both intra and inter technology handover
mechanisms. HMIPv6 also supports both type of handovers. It
reduces overloading and improves the handover speed [13].
Fast Handovers for MIPv6 (FMIPv6) [16] is a new proposal
trying to optimize MIPv6. It greatly reduces packet loss and
handover time in both types of handover. The other network,
transport and higher layer protocols (except DDNS) effectively
supports handover mechanisms.
C.1.2. Handoff management
Efficient handoff or handover management is another primary
area of concern for maintaining global mobility. While roaming,
smooth handover of the mobile terminals is necessary for
seamlessly maintaining the ongoing communication.
Advancements in the various protocols designed play a prime
role in this context. Though MIPv6 was designed as the future
standard mobility protocol it suffers from drawbacks like high
packet loss, increased system load, high handover latency [2]
and signaling scalability mainly due to absence of location
management hierarchy, absence of paging support and wastage
of mobile node’s battery power. HMIPV6 promoted by the
Internet Engineering Task Force (IETF) as a further
advancement to MIPv6 has till now proved to be a promising
technology for the next generation wireless networks efficiently
tackling the MIPv6 drawbacks. However, effects of HMIPv6 on
4G security aspects (like AAA) and roaming PANs have not
been studied in depth. Seamless handovers in a 4G scenario
requires to handle challenges related to both intra-network intercellular (horizontal)
handover and inter-network inter-cellular (vertical) handover
mechanisms and is thus complicated. Figure
Fig 3 Vertical and horizontal handover of a mobile terminal [2]
However, unlike horizontal handovers, dealing with vertical
handover mechanisms is much complicated. References [5] and
[17] describes effective 4G vertical handover management
architectures, which reduces unnecessary handover attempts
and simplifies the signaling effect.
Possible Research Directions: Much scope for further significant
research in developing a globally accepted handover
management framework for 4G systems is there. Though
several solutions combining Mobile IP with routing at lower layer
are proposed to significantly manage handover related
difficulties for different networks but plethora of challenges still
exist in every aspect. Like designing of new handover decision
policies and algorithms relating to soft, hard and hybrid
handovers and efficient handover selection policies for optimal
cross-layer performance in multiradio environments, to name a
few.
262
IETE TECHNICAL REVIEW, Vol 23, No 4, 2006
Problems relatingto reducing handover delays and QoS
variability in heterogeneous systems need the developments of
enhanced priority based algorithms and locationaware adaptive
application techniques. Another ongoing research area is to
finding out whether Virtual Connectivity Manager may emerge as
a better option than Mobile IP in terms of Internet mobility in
future. However it would take considerable amount of time
before a significant handover managing framework could be
successfully devised.
C.2. Integration and Interoperability of diverse networks:
4G systems intend to facilitate the seamless integration and
interoperation of a broad range of existing systems like satellite
broadband, 3G systems, WLL, fixed wireless access systems,
WLAN, PAN, ad-hoc systems, WiMAX and the new truly
broadband wireless access technologies with IP as the
infrastructure backbone. Such an open wireless architecture
intending to provide unhampered connectivity, fully broadband
access, unhampered global roaming, global Internet/ data/voice,
perfect QoS and user controlled services is really difficult to
achieve owing to diverse nature of the constituent access
technologies in terms of varying bit rates, bandwidth allocation,
channel characteristics, fault-tolerance levels and handoff
management mechanisms. Figure 4 [19] shows the probable 4G
interworking approach.
Current State of Research: A plethora of global diversified
research activities exists, which examined how and to what
extent the seamless merger of the diversified access networks
should be carried on. The merged Ipv6-based cooperative,
heterogeneous infrastructure would allow users with multimode
terminals to roam globally, accessing any service anywhere
without the QoS getting affected. In reference [18] Varsney and
Jain have discussed three such probable merged architectures
(shown in Fig 5 [18]). In the first integrated framework multimode
devices access the diverse services offered by the different
underlying networks. This architecture provides better call
completion and area coverage but is not cost-effective. The
second integrated framework is overlay network-based where
the different universal access points (UAPs) in the overlay
network select the available appropriate underlying network for
the user. This architecture is complex but supports better billing
and subscription. The third architectural framework uses
common access protocol and hence is less complicated but is
feasible only in case of wireless ATMs. Researchers have
pointed out that the extent to which an integration should be
carried out depends on whether it is possible to integrate the
subsystems within the existing standards or it needs
modifications. General trend of integration and interoperationoriented researches have identified loose coupling, tight
coupling and very tight coupling as the three potential integration
or coupling schemes for hot-spot extensions (like WLAN) to 3G
networks . Loose coupling provides authenticated billing but
poor
263
RAY & MISRA : 4G NETWORKS
seamless connectivity and QoS support, tight coupling supports
efficient vertical handoffs but is complicated as well as delay
prone and the much complicated very tight coupling architecture
can efficiently provide radio resource measurement (RRM) and
better QoS support. In this context, diversity of research
activities studying the different potential integration and
interoperation techniques of WLAN and 3G networks have taken
place. References [20-24] discusses effective integration
techniques between WLAN and UMTS/GPRS/WWAN each with
its own pros and cons improving the overall system
performance. The ambient networks proposed by Niebart et al
[25] is another multi-operator controlled, flexible, multinetwork
integration technique facilitating rich end-toend QoS support. An
unique convergence framework of TV broadcast and mobile
cellular technologies really enriching the 4G Information Society
is described in reference [26].
Possible Research Directions: Despite all these fruitful research
efforts there is still a long way to go before an universally
accepted, completely transparent, user-focused, cooperative
public-private wireless broadband communication framework
can be designed, which will provide seamless, ubiquitous
coverage to the public network using multiple different private
systems [27]. This envisioned IPv6 based completely packetswitched framework should be dynamically layered and
reconfigurable as well as dynamically self-organized and
cooperative in terms of network operations, control, maintenance
and reuse of independent modularized functional network blocks
[28]. Research on these aspects are currently channelized to
diversified directions. Several research groups worldwide like
IETF, IEEE, 3GPP and 3GPP2, WiMAX Forum to name a few
are competing against each other to provide fast, easy and cost
effective interoperable solutions between the different existing
standards. Huge research advancements are carried out each
day in terms of designing more enriched integrated WiFi-3G
cellular networks, WiFi-WiMAX networks, 3G-WiMax networks
and WiFi-Distributed Wireless Communication Systems (DWCS)
[29]. As a result each day different products with different
embedded features compliant with the different technologies are
flocking the global market but wait is still on for truly 4G devices
that would be universally compliant with all the different existing
technologies.
Fig 5 Possible 4G wireless architectures [18]
264
IETE TECHNICAL REVIEW, Vol 23, No 4, 2006
4. CONCLUSION
With the plethora of promising features 4G is truly moving
towards getting universally accepted as the ideal next
generation communication system. 4G is visualized as a
conglomeration of different heterogeneous access technologies.
With this view, this article discussed the probable research
challenges under the different headings of mobile terminals and
users, mobile services, mobile and wireless access networks,
and communication challenges along with their proposed
potential solutions. While some of these challenges like
multimode user terminals, automatic network selection,
seamless mobility management and smooth interworking of
different heterogeneous access networks have drawn much
research attentions, others like routing, protocol requirements,
services and the different communication-related challenges
demand much more research enhancements. The article also
identified the different unaccessed or less accessed research
topics, which need significant contributions for the 4G visions to
come true by 2010.
8.
Network Discovery and Selection Problem, InternetDraft of the Internet Engineering Task Force (IETF).
9.
B Thai, R Wan, A Seneviratne & T Rakotoarivelo,
Integrated Personal Mobility Architecture: A Complete
Personal Mobility Solution, Mobile Networks and
Applications 8, pp 27-36, 2003.
10. A D Stefano & C Santoro, NetChaser: Agent Support
for Personal Mobility, IEEE Internet Comp, vol 4, no 2,
Mar/April 2000, pp 74-79.
11. R S Tupelly, J Zhang & E K P Chong, Opportunistic
Scheduling for Streaming Video in Wireless Networks,
2003 Conference on Information Sciences and
Systems, The Johns Hopkins University, March 12-14,
2003.
ACKNOWLEDGEMENT
12. F H P Fitzek & M Reisslein, Wireless video streaming
with TCP and simultaneous MAC packet transmission
(SMPT), International Journal of Communication
Systems, vol 17, pp 421-435, 2004.
The author Iti Saha Misra is thankful to AICTE, India for the
financial support of this research under CAYT.
13. D Le, X Fu & D Hogrefe, A Review of Mobility Support
Paradigms for the Internet, IEEE Communications
Surveys & Tutorials, 1st Quarter 2006, pp 38-51.
REFERENCES
1.
2.
3.
4.
5.
6.
7.
B G Evans & K Baughan, Visions of 4G, IEE
Electronics and Communications engineering Journal,
Autumn/Winter 2000.
S Y Hui & K H Yeung, Challenges in the Migration to
4G Mobile Systems, IEEE Commuications, vol 41, no
12, Dec 2003, pp 54-59.
R Eijk, J Brok, J Bemmel & B Busropan, Access
Network selection in a 4G Environment and the Roles
of Terminal and Service Platform, Project: 4GPLUS,
Wireless World Research Forum.
M Calisti, T Lozza & D Greenwood, An Agent- Based
Middleware for Adaptive Roaming in Wireless
Networks, Workshop on Agents for Ubiquitous
Computing, AAMAS 2004, 20 July 2004, New York,
USA.
K Murray, R Mathur & D Pesch, Network Access and
Handover Control in Heterogeneous Wireless Networks
for Smart Apace Environments, 1st International
Workshop on Managing Ubiquitous Communications
and Services (MUCS), Dec 11, 2003, Waterford,
Ireland.
F Daneshgaran, M Laddamoda & M Mondin, On the
Reconfigurability of a Software Radio Terminal for
Supporting the Third and Fourth generation Wireless
Standards, IEEE International Conference on Third
Generation Wireless and Beyond, June 2001, San
Francisco.
T H Le & A H Aghvami, Performance of an Accessing
and Allocation Scheme for the Download Channel in
Software Radio, Proc IEEE Wireless Commun and Net
Conf, vol 2, pp 517-21, 2000.
14. F Paint, P Engelstad, E Vanem, T Haslestad, A M
Nordvik, K Myksvoll & S Svaet, Mobility Aspects in 4G
Networks, Telenor 2002, White Paper.
15. U Varshney, Location management for wireless
networks: issues and directions, Int J Mobile
Communications, vol 1, no 1 / 2, 2003.
16. R Koodli, Fast Handovers for Mobile IPv6, RFC 4068,
July 2005.
17. W Zhang, J Jaehnert, K Dolzer, Design & Evaluation of
a Handover Decision Strategy for 4th Generation
Mobile Networks, Proceedings of the 57th IEEE
Vehicular Technology Conference, VTC 2003 Spring,
Jeju, Korea, 2003.
18. U Varshney & R Jain, Issues in Emerging 4G Wireless
Networks, IEEE Computer, June 2001, vol 34, no 6, pp
94-96.
19. Pedro M Ruiz, Beyond 3G: Fourth generation Wireless
Networks, II Jornadas de Internet NG, Madrid, 22
October 2002.
20. J Chen, S H G Chan, J He & S C Liew, Mixed-Mode
WLAN: The Integration of Ad Hoc Mode with Wireless
LAN Infrastructure, IEEE Globecom 2003, 1-5
December, San Francisco, USA.
21. I S Misra & A Banerjee, MPLS Based Mobility
Framework in 4G Architectures, Proceedings of IEEE
Tencon 2003, 15-17 October, Bangalore, India, 2003.
265
RAY & MISRA : 4G NETWORKS
22. S L Tsao & C C Lin, Design and evaluation of UMTSWLAN Interworking Strategies, Proceedings of
Vehicular Technology Conference 2002, IEEE VTC
56th, Fall 2002
27. 27. K Ahmavaara, H Haverinen & R Pichna,
Interworking Architecture Between 3GPP and WLAN
Systems, IEEE Communications Magazine, vol 41, no
11, November 2003.
23. . M Jaseemuddin, An Architecture for Integrating UMTS
and 802.11 WLAN Networks, Proceedings of Eighth
IEEE International Symposium on Computers and
Communication ISCC03, 2003, p 716.
28. . C Politis et al, Cooperative Networks for the Future
Wireless World, IEEE Communications Magazine, vol
42, no 9, September 2004, pp 70-79.
29. S Zhou, M Zhao, X Xu, J Wang & Y Yao, Distributed
Wireless Communication System: A new Architecture
for Future Public Wireless Access, IEEE
Communications Magazine, March 2003, pp 108-113.
24. Flarion Technologies, Inc, 4 Ps for Carrier Employment
of Mobile Broadband Systems, White Paper, Aug 2004.
25. N Niebert, A Schieder, H Abramowicz, G Malmgren, J
Sachs & U Horn, Ambient Networks: An Architecture for
Communication Networks beyond 3G, IEEE Wireless
Communications, April 2004, vol 11, no 2, pp 14-22.
26. O Benali, K El-Khazen, D Garrec, M Guiraudou and G
Martinez, A Framework for an Evolutionary Path toward
4G by Means of Cooperation of Networks, IEEE.
Communications Magazine, May 2004, pp 82-89.
AUTHOR
Iti Saha misra is presently holding the
post of Reader in the Department of
Electronics and Telecommunication
Engineering,
Jadavpur
University,
Kolkata, India. She received her BTech
degree in Radio Physics and Electronics
from Calcutta University (1989) and
Masters
in
Telecommunication
Engineering from Jadavpur University
(1991), Kolkata. She completed PhD in
Engineering in the field of Microstrip Antennas from Jadavpur
University (1996). Her current research interests are in the areas
of Mobility Management Network Architecture and protocols,
Integration Architecture of WLAN and 3G Networks, Location
Management for Cellular Wireless Networks. Her other research
activities are related to Microstrip. Antennas, Design
Optimization of Wire Antennas using Numerical Techniques. Dr
Saha Misra has authored several journal and International
Conference papers. She is the recipient of the prestigious
Career award for Young teachers by All India Council for
Technical Education (AICTE) for the financial year 2003-2004.
*
*
http://folk.uio.no/paalee
*
Sayan Kumar Ray is currently a PhD scholar in the Network
Research Group in Department of Computer Science and
Software Engineering in the University of Canterbury,
Christchurch, New Zealand. He completed his BE from Gulbarga
University, Karnataka in Computer Science and Engineering in
1999 and MTech from University of Calcutta in Computer
Science and Engineering in 2002. He has worked in multiple
software companies after BE and prior to MTech served as
Lecturer in couple of reputed engineering colleges (Narula
Institute of Technology - 2002 to 2003 and Heritage Institute of
Technology - 2003 to 2006) in Calcutta in the Dept of Computer
Science and Engineering. His research interests is in the area of
4G networks.
*
*
*