Int. J. Communications, Network and System Sciences, 2010, 3, 472-476
doi:10.4236/ijcns.2010.35063 Published Online May 2010 (http://www.SciRP.org/journal/ijcns/)
Interoperability of Wireless Networks with 4G Based
on Layer Modification
Dilshad Mahjabeen1, Aminul Haque Mohammed Sayem1, Anis Ahmed2, Shahida Rafique2
1Electrical and Electronics Engineering, Stamford University Bangladesh, Dhaka, Bangladesh
2Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka, Bangladesh
Received February 26, 2010; revised March 21, 2010; accepted April 23, 2010
Abstract
Fourth generation wireless communication systems feel the necessity of transparent and seamless user
roaming with end-to-end connectivity. These systems also demand higher data rate, higher mobility support
and QoS guarantees due to rapid development of wireless and mobile networks. These requirements open
potentials for the operators to increase their service portfolio and for the users to experience context-rich and
personalized services. Consequently the interoperability between different wireless network platforms
emerges as a crucial necessity. Here focus is given to the significance of the network interoperability aspect
based on layered approach and its role in the development towards 4G. This paper also gives an overview of
the major 4G features and differentiating characteristics from other generations.
Keywords: 4G, Interoperability, Reconfigurability, Cooperativeness, Cross Layer
1. Introduction
Different generations of wireless communication impro-
ve the facilities for users day by day. The generations are
classified into three groups namely 1G, 2G and 3G. 1G
was completely analog and used for only voice trans-
mission [1]. 2G networks were built mainly for voice
services and slow data transmission. The cellular servi-
ces combined with GPRS became 2.5G. This generation
provides services such as Wireless Application Protocol
(WAP) access, Multimedia Messaging Service (MMS)
and for Internet communication services such as email
and World Wide Web access. Although 2G is very pop-
ular and successful but it lacks single worldwide radio
band technology standard as well as inefficient use of sp-
ectrum resources for bursty data. 3G networks represent
the natural evolution from previous standards. In this
case the networks enable network operators to offer users
a wider range of more advanced services while achieving
greater network capacity through improved spectral eff-
iciency. 3G networks offer a greater degree of security
than 2G predecessors. This generation (3G) allows sim-
ultaneous use of speech and data services and higher data
rates. The services provided by 3G are wide-area wireless
voice telephone, video calls, and wireless data, all in a
mobile environment [2]. However 3G performances may
not be sufficient to meet needs of future high quality
applications. 3G does not provide mobility and service
portability since it is based on primarily a wide-area con-
cept. For this facility hybrid network (wireless LAN con-
cept and cell or base-station wide area network design) is
required. We need all digital packet networks that utilize
IP in its fullest form with converged voice and data capa-
bility. And this great opportunity will be fulfilled by 4G
wireless communications. In this paper we mainly deal
with interoperability—the most important and special
characteristic of 4G wireless communications. Section II
describes the characteristics of 4G and the motivation for
4G other than 3G. This section also differentiates 4G
from other generations. Section III focuses how 4G
based on layered modification provide interoperability.
Section IV describes about the role of cross layer at in-
teroperable issue by 4G.
2. Journey towards 4G from 3G
The limitations of previous generation lead to improved
generation. Their characteristics vary depending on some
demanding features. Some of the differentiating charac-
teristics are given in Table 1. The first generation of
cellular networks consisted of analog systems capable of
carrying only voice. 2G were packet switched transfer-
ring voice only. 3G is basically a circuit switched cellu-

D. MAHJABEEN ET AL. 473
lar network and so they have their own gateway to inter-
pret IP from the back bone network. They also have their
own protocol and interfaces for communication within
themselves. To make this problem end, the only solution
is 4G networks. Moreover, 3G is lacking from the fol-
lowings: limitation of spectrum allocation, challenging
gradually increasing bandwidth and high data rate for
multimedia service, difficulty to roam across distinct
service environment, lack of end environment, and lack
of end to end continuous transmission mechanism [3]. To
face these challenges, the new level of mechanism, 4G
communications is introduced.
4G is an all IP packet switched network. This genera-
tion is the upgrade strategy in world of wireless commu-
nications. 4G system is expected to provide a compre-
hensive and secure IP based solution with facilities like
voice, data and streamed multimedia. The key character-
istics of 4G are global mobility, service portability, sca-
lability and seamless handoff. It will be very friendly to
comprehensive like “Anytime, Anywhere, Anyhow and
Always-on” basis and at much higher data rates compa-
red to previous generations. This will secure IP based
solution with facilities like voice, data and streamed mul-
timedia. Another special characteristic of 4G is the in-
teroperability with existing wireless standards [4]. This
generation provides integration across different network
topologies i.e., hybrid network architecture that inte-
grates wireless wide area networks wireless.
3. Interoperability
With the rapid development of various wireless commu-
nication systems worldwide, there are also gradual chan-
ges in users’ expectation and demand. Consequently the
corresponding wireless networks work many fold at their
capacity limits. So there is every chance of emergency
crisis and/or disasters at the peak and crucial period. Th-
us interoperability can offer network providers with a
possibility to switch between alternative wireless access
networks. The basic theme of interoperability will yield
the necessity of (user transparent) reconfigurability and
Table 1. Comparison of different generations.
Properties 2G 3G 4G
Network Architecture LAN, Wide area cell-based Hybrid -
Driving Architecture Only voice dominantly voice; also data Converged data and voice over IP
Switching Packet switched Circuit and Packet All digital with packetized voice
Radio Access FDMA, TDMA, CDMA WCDMA, CDMA2000, IWC-136 MC-CDMA, OFDMA
Database HLR,VLR, EIR, AuC EHLR, VLR, EIR, AuC EHLR, VLR, EIR, AuC
Data rates 9.6 to 384 kbps Up to 2 Mbps 100Mbps
Roaming Restricted Global Global
Compatible Not compitable to 3G Compitable to 2G, 2G+ and blu-
tooth Compatible to 3G
Handsets Dual mode TDMA and CDMA
Voice and data terminals
Multiple mode voice, data, vedio
terminals
Multiple mode voice, data streamed
video at higher data rates.
Applica-
tions SMS, Internet Internet, SMS Internet, MMS, Mutimedia, HDTV, M TV
Bandwidth 25 MHz 5-20 MHz 100 MHz
Frequency Band Tri Band800, 900,1800,1900 MHz Dependent on country (1800-2400
MHz) Higher frequency bands (2-8 GHz)
Component design Optimized antenna design Optimized antenna design,
multi-band adapters
Smarter Antennas, software multiband
and wideband radios
FEC tech Convolutional coding Convolutional rate 1/2, 1/3 Concatenated coding scheme
IP No IP
Connection
A number of air link protocols,
including IP 5.0 All IP (IP6.0)

D. MAHJABEEN ET AL. 474
cooperativeness in various communication systems tun-
neling towards the 4G journeys.
3.1. Reconfigurability
The reconfigurable interoperability can be done at the
network level, the user level or both. This will be very
helpful for both the network providers and the users’
perspective. The reconfigurable interoperability will pro-
vide selection between alternative wireless access net-
works. The selection could be based on several recon-
figurable interoperability issues such as:
 Channel state;
 Outage probability;
 Vertical handover probability;
 Users’ QoS requirements;
 Context awareness;
 Load sharing and distribution between different
spatially coexisting wireless networks;
 Efficient spectrum sharing;
 Preferred gateway selection and network dis-
covery and
 Congestion control.
The mechanism of reconfigurability refers not only to
the physical layer, but span across the entire protocol
stack (including cross-layer optimizations). The recon-
figurable interoperability of the heterogeneous 4G sys-
tem will lead to more efficient end-to-end connectivity
and service delivery in heterogeneous environments, ea-
sier worldwide roaming and dynamic adaptation to re-
gional contexts, enhanced personalization and richer ser-
vices. At the network level, the reconfigurable interop-
erability will offer network providers with a possibility
to choose between alternative wireless accesses networks
at minimal cost. At the user level, the interoperability of
the heterogeneous 4G systems will provide more effi-
cient end-to-end connectivity and service delivery in
heterogeneous environments, easier global roaming and
dynamic adaptation to regional contexts, enhanced per-
sonalization and enriched services [5].
3.2. Cooperativeness
3G specify the PHY and MAC of the radio link. This
alone is not adequate to build an interoperable broadband
wireless network. Interoperable networks involve the
following issues:
 End-to-end service such as IP connectivity;
 Session management;
 Security;
 QoS;
 Mobility;
 Connectivity issues;
 Self organization;
 Authentication, Authorization, and Accounting.
Cooperativeness comes to ensure these issues. This
means connectivity between all the entities of a network
in a consistent manner across all access technologies for
any service. In 4G, a cooperative network (CoNet) con-
sists of three distinct layers such as application, connec-
tivity and access that form logically separate subsystems.
Each of the layers can be further divided into different
sub layers as shown in the Figure 1. The layers should
have well defined interfaces and be functionally inde-
pendent of each other for an approach is required to ens-
ure easy adaptation of heterogeneous access technologies,
related technology changes, and flexible support for rap-
id service innovation. Actually the connectivity layer pl-
ays an important role for cooperation across various real-
izations of networks, which in turn ensures the interoper-
ability. This layer will be independent of the various tra-
nsport technologies used to link the nodes of the network
together. Finally, the user will enjoy seamless roaming
across different access technologies and administrative
domains without any manual user intervention [6].
One of the 4G’s major goals is integration, which of-
fers seamless interoperability of different types of wire-
less networks with the wire line backbone. Some of the
available attempted heterogeneous interoperable inte-
grated architecture are: a loosely-coupled, Mobile IPv6
(MIPv6)-based GPRS/WLAN/LAN heterogeneous net-
work, implementation of IPv6-based mobility-enabled
network architecture with Authentication, Authorization,
Accounting and Charging (AAAC) services and support
for Quality of Service (QoS) [7].
3.3. Access Network
From the point of view of access network, 3G access
Application
Layer
User Plane Control
Plane
Management
Plane
Connectivity
Layer Network Control Sub Layer
Transport Sub Layer
Service Support Sub Layer
Service Application Sub Layer
Access
Layer
Figure 1. Layers of 4G providing interoperability.

D. MAHJABEEN ET AL. 475
network uses WCDMA, cdma 2000. But these are com-
plicated and require more protocol for system structure
coverage. On the other hand, 4G access network uses the
OFDMA, 3  RTT and MIMO antennas. Also hybrid
multiple access technique is used for high speed mobile
or nomadic user, data or voice traffic, call centre or
boundary conditions [8]. But the abovementioned access
techniques currently do not interoperate LAS CDMA
(Large area synchronized CDMA) access technique
solves this problem. LAS CDMA will be compatible
with all current and future standards and there is a
relatively easy transition from the existing system to
LAS CDMA. Link air emphasizes that LAS CDMA will
accommodate all the advanced technology planned for
4G. LAS CDMA will also further improve the prevailing
the techniques like WCDMA, 3  RTT [1].
4. Cross Layer
In wireless network, interoperable systems provide coor-
dination among layers. Cross-layer design or “cross-lay-
ering” provides functionalities associated with the origi-
nal layers to allow coordination, interaction and joint
optimization of protocols crossing different layers. In
order to provide improvement in terms of some per-
formance metric, the cross-layer approach to system de-
sign derives from the interaction among protocols oper-
ating at different layers of the protocol stack. The main
advantage deriving cross layering paradigm is the modu-
larity in protocol design, which enables interoperability
and improved design of communication protocols. An
example of cross layer approach for interoperability is
shown in Figure 2.
MAC-PHY Cross Layer: The physical layer transmits
power, which can be tuned by the Medium Access Con-
trol (MAC) layer to increase the range of transmission.
NET–MAC Cross Layer: Network layer could use
NET-MAC-PHY
Cross
Layer
Management
Plane
Network
Layer
MAC-PHY
Cross Layer
Management
Plane
MAC
Layer
Physical
Layer
NET-MAC
Cross Layer
Management
Plane
Figure 2. Cross-Layer approach for Interoperability.
MAC layer events like handoff to reduce Mobile-IP
hand-off latency for seamless connectivity.
NET-MAC-PHY Cross Layer: This layer provides
seamless connectivity and enhanced transmission range
[9].
5. Conclusions
For higher data rates, higher mobility support and seam-
less communication 4G utilizes a common platform that
will unify a variety of evolving access technologies, un-
interupted internetworking and interoperability solutions
and adaptive multimode user terminals. Reconfigurable,
co-operative and cross layer architecture based on laye-
red approach for interoperability are mentioned here. The
co-net architecture also provides end to end services,
security and self organization. More over using multiple
descriptions coding at application layer combined with
orthogonal frequency division multiplexing at the link
level provides robustness against hostile wireless chan-
nels. Negotiation between application, data link control
and physical layer is exploited to increase user quality of
service in terms of picture signal to noise ratio and
bandwidth efficiency. 4G networks suffer from the lack
of Layer 2 QoS provisioning in heterogeneous networks,
mainly due to the non-uniform nature of the QoS models
and service interfaces among different wireless tech-
nologies. Other problem is the lack of coordination of L3
QoS with L2 QoS and mobility. All these problems can
be solved by introducing QoS abstraction layer in be-
tween layer 2 and 3 in the control plane which will be
discussed in our next paper.
6. References
[1] “Emerging Wireless Technologies: A Look into the Future
of Wireless Communications-Beyond 3G”.
http://www.safecomprogram.gov/NR/rdonlyres/5C74C631-
ACF6-433F-B313-C
[2] D. I. Axiotis, F. I. Lazarakis and C. Vlahodimitro,
“Mobility and Traffic Parameters for Simulating Inte-
roperating UMTS and HIPERLAN/2 MTMR Enabled
Networks,” The 57th IEEE Seminual Vehicular Tech-
nological Conference, Jeju,Vol. 4, 2003, pp. 2745-2749.
[3] S. Hussain, Z. Hamid and N. S. Khattak, “Mobility
Management Challenges and Issues in 4G Heterogenous
Networks,” ACM, New York, USA, 2006.
[4] “Evolution of wireless connection”.
http://4G-wirelessevolution.tmcnet.com/topicsmostigov/
my/mosti/images/stories/DICT/policy
[5] L. M. Gavrilovska and V. M. Atanasovski, “Interopera-
bility in Future Wireles Communications Sytems: A
Roadmap to 4G,” Microwave Review,Vol. 13, No. 1,
2007, pp. 19-28.

D. MAHJABEEN ET AL. 476
[6] “Cooperative Networks of 4G”.
www-scf.usc/edu/~ssaraf/ EE555.pdf
[7] L. Gavrilovska, V. Atanasovski, V. Rakovic, O. Ognenoski
and A. Momiroski, “Providing Interoperability in Hetero-
geneous Environments towards 4G,” ELMAR, 50th Inter-
national Symposium, Zadar, Vol. 1, 2008, pp. 223-226.
[8] L. D. Uomo and E. Scarrone, “All-IP 4G Network arc-
hitecture for Efficient Mobility and Resource Manageme-
nt,” 5th International Symposium on Wireless Personal
Multimedia Communications, Honolulu, Vol. 2, 2002, pp.
591-595.
[9] D. Kliazovich, M. Devetsikiotis and F. Granelli, “Formal
Methods in Cross Layer Modeling and Optimization of
Wireless Networks,” In: Kotsopoulos, S. and Ioannou, K.
Ed., Handbook of Research on Heterogeneous next
Generation Networking: Innovations and Platforms, 2009,
pp. 1-24.