4G communications

ABSTRACT
The approaching 4G (fourth generation) mobile communication systems are projected to
solve still remaining problems of 3G (third generation) systems and to provide a wide variety of
new services, from high-quality voice to high definition video to high-data-rate wireless
channels. The term 4G is used broadly to include several types of broadband wireless access
communication systems, not only cellular telephone systems. One of the terms used to describe
4G is MAGIC Mobile multimedia, anytime any-where, Global mobility support, integrated
wireless solution, and customized personal service. As a promise for the future, 4G systems, that
is, cellular broadband wireless access systems have been attracting much interest in the mobile
communication arena. The 4G systems not only will support the next generation of mobile
service, but also will support the fixed wireless networks.
This paper presents an overall vision of the 4G features, framework, and integration of
mobile communication. The features of 4G systems might be summarized with one word
integration. The 4G systems are about seamlessly integrating terminals, networks, and
applications to satisfy increasing user demands.
The continuous expansion of mobile communication and wireless networks shows
evidence of exceptional growth in the areas of mobile subscriber, wireless network access,
mobile services, and applications. An estimate of 1 billion users by the end of 2003 justifies the
study and research for 4G systems.
History
The history and evolution of mobile service from the 1G (first generation) to fourth
generation are discussed in this section. Table 1 presents a short history of mobile telephone
technologies.
This process began with the designs in the 1970s that have become known as 1G. The
earliest systems were implemented based on analog technology and the basic cellular structure of
mobile communication. Many fundamental problems were solved by these early systems.
Numerous incompatible analog systems were placed in service around the world during the
1980s.
The 2G (second generation) systems designed in the 1980s were still used mainly for
voice applications but were based on digital technology, including digital signal processing
techniques. These 2G systems provided circuit switched data communication services at a low
speed. The competitive rush to design and implement digital systems led again to a variety of
different and incompatible standards such as GSM (global system Mobile), mainly in Europe;
TDMA (time division multiple access) (IS-54/IS-136) in the U.S.; PDC (personal digital
cellular) in Japan; and CDMA (code division multiple access) (IS-95), another U.S. system.
These systems operate nationwide or internationally and are today's mainstream systems,
although the data rate for users in these system is very limited.
During the 1990s, two organizations worked to define the next, or 3G, mobile system,
which would eliminate previous incompatibilities and become a truly global system. The 3G
systems would have higher quality voice channels, as well as broadband data capabilities, up to
2Mbps. unfortunately, the two groups could not reconcile their differences, and this decade will
see the introduction of two mobile standards for 3G. In addition, China is on the verge of
implementing a third 3G systems.
An interim step is being taken between 2G and 3G, the 2.5G. It is basically an
enhancement of the two major 2G technologies to provide increased capacity on the 2G RF
(radio frequency) channels and to introduce higher throughput for data service, up to 384 kbps.
A very important aspect of 2.5G is that the data channels are optimized for packet data, which
introduces access to the Internet from mobile devices, whether telephone, PDA (personal digital
assistant) or laptop.
Although the new, third generation (3G) wireless technology has not yet been
implemented, leading companies in the industry are already laying the groundwork for what
some are calling fourth generation (4G) technology. Researchers are continuing their ideas in the
development of an undefined wireless world, which could become operational by 2010. The first
generation (1G) and second generation (2G) of mobile telephony were intended primarily for
voice transmission. The third generation of mobile telephony (3G) will serve both voice and data
applications.
There really is no clear definition of what 4G will be. It is generally accepted that 4G will
be a super-enhanced version of 3G i.e., an entirely packet switched network with all digital
network elements and extremely high available bandwidth. For the most part, it is believed that
4G will bring true multimedia capabilities such as high-speed data access and video
conferencing to the handset. It is also envisioned that 4G systems will be deployed with
software-defined radios, allowing the equipment to be upgraded to new protocols and services
via software upgrades. 4G also holds the promise of worldwide roaming using a single handheld
device.
As with all technology progressions, the “next” upgrades must be in planning and
development phases while its predecessors are being deployed. This statement holds true with all
mobile telecommunications to date. It seems that it will also hold true for the next generations of
wireless networks. The original analog cellular systems are considered the first generation of
mobile telephony (1G). In the early 1980s, 1G system was deployed. At the same time, the
cellular industry began developing the second generation of mobile telephony (2G). The
difference between 1G and 2G is in the signaling techniques used: 1G used analog signaling, 2G
used digital signaling. As experience shows, the lead-time for mobile phone systems
development is about 10 years. It was not until the early to mid 1990s that 2G was deployed.
Primary thinking and concept development on 3G generally began around 1991 as 2G systems
just started to roll out. Since the general model of 10 years to develop a new mobile system is
being followed, that timeline would suggest 4G should be operational some time around 2011.
4G would build on the second phase of 3G, when all networks are expected to embrace Internet
protocol (IP) technology. During the last year, companies such as Ericsson, Motorola, Lucent,
Nortel and Qualcomm came up with "3G-plus" concepts that would push performance of
approved, though still emerging, standards beyond current ones.
However, the demand for higher access speed multi-media communication in today's
society, which greatly depends on computer communication in digital format, seems unlimited.
According to the historical indication of a generation revolution occurring once a decade, the
present appears to be the right time to begin the research on a 4G mobile communication system.
b
Legend:
1xRTT = 2.5G CDMA data service up to 384 kbps
AMPS = Advanced Mobile Phone Service
CDMA = Code Division Multiple Access
EDGE = Enhanced Data for Global Evolution
FDMA = Frequency Division Multiple Access
GPRS = General Packet Radio Service
GSM = Global System for Mobile communication
NMT = Nordic Mobile Telephone
PDC = Personal Digital Cellular
PSTN = Pubic Switched Telephone Network
TACS = Total Access Communications System
TDMA = Time Division Multiple Access
WCDMA = Wideband CDMA
4G Communication
This new generation of wireless is intended to complement and replace the 3G systems,
perhaps in 5 to 10 years. Accessing information anywhere, anytime, with a seamless connection
to a wide range of information and services, and receiving a large volume of information, data,
pictures, video, and so on, are the keys of the 4G infrastructures. The future 4G infrastructures
will consist of a set of various networks using IP (Internet protocol) as a common protocol so
that users are in control because they will be able to choose every application and environment.
Based on the developing trends of mobile communication, 4G will have broader
bandwidth, higher data rate, and smoother and quicker handoff and will focus on ensuring
seamless service across a multitude of wireless systems and networks. The key concept is
integrating the 4G capabilities with all of the existing mobile technologies through advanced
technologies.
Application adaptability and being highly dynamic are the main features of 4G services
of interest to users. These features mean services can be delivered and be available to the
personal preference of different users and support the users' traffic, air interfaces, radio
environment, and quality of service. Connection with the network applications can be transferred
into various forms and levels correctly and efficiently. The dominant methods of access to this
pool of information will be the mobile telephone, PDA, and laptop to seamlessly access the
voice communication, high-speed information services, and entertainment broadcast services.
Figure 1 illustrates elements and techniques to support the adaptability of the 4G domains
The fourth generation will encompass all systems from various networks, public to
private; operator driven broadband networks to personal areas; and ad hoc net works. The 4G
systems will interoperate with 2G and 3G systems, as well as with digital (broadband)
broadcasting systems. In addition, 4G systems will be fully IP based wireless Internet.
This all encompassing integrated perspective shows the broad range of systems that the
fourth generation intends to integrate, from satellite broadband to high altitude platform to
cellular 3G and 3G systems to WLL (wireless local loop) and FWA (fixed wireless access) to
WLAN (wireless local area network) and PAN (personal area net work), all with IP as the
integrating mechanism.
With 4G, a range of new services and models will be available. These services and
models need to be further examined for their interface with the design of 4G systems. Figures 2
and 3 demonstrate the key elements and the seamless connectivity of the networks.
Table 2: Comparisons between the earlier technologies
Feature 2G 2G+ 3G
Handsets Voice only terminals
New type of terminal
Dual mode TDMA and
CDMA Voice and data
terminals WAP, no
multimedia support
New type of terminal
Multiple modes Voice,
data and video terminals
WAP, multimedia mgmt
Databases HLR, VLR, EIR, Auk HLR, VLR, EIR, Auk
Enhanced HLR, VLR,
EIR, AuC
Data Rates Up to 9.6 Kbps
Up to 57.6 Kbps (HSCSD)
Up to 115Kbps (GPRS)
Up to 384 Kbps (EDGE)
Up to 2Mbps
Applications
Advanced voice, Short
Message Service
(SMS)
SMS, Internet Internet, multimedia
Compatibility Not compatible to 3G Not compatible to 3G
Compatible to 2G, 2G+
and Blue tooth
Interoperability and the Evolution of Network Architectures
One of the most challenging issues facing deployment of 4G technologies is how to make
the network architectures compatible with each other. New signaling techniques are being
designed specifically to enhance today's second generation (2G) networks, deliver unprecedented
functionality for 3G, and successfully drive the Fourth Generation (4G) of wireless, thus
delivering immediate and long-term benefits to carriers. With the architecture of each generation
of wireless devices addressed in the development of advanced technologies, carriers can easily
evolve their systems without additional network modifications, significantly reducing costs and
implementation time. Currently, different wireless technologies (e.g., GSM, CDMA, and
TDMA) are used throughout the world for the 2G, 2.5G, and virtually 3G networks. There are
two approaches being used to develop 4G access techniques: 3xRTT (currently 1xRTT for 2.5
and 3G) and Wideband CDMA (W-CDMA). These disparate access techniques currently do not
interoperate. This issue may be solved with software-defined radios. Link Air Communications
is developing a new access technology called large-area-synchronized code-division multiple
access (LAS-CDMA). LAS-CDMA will be compatible with all current and future standards, and
there is a relatively easy transition from existing systems to LAS-CDMA (using software defined
radios). Link Air emphasizes that LAS-CDMA will accommodate all the advanced technologies
planned for 4G and that LAS-CDMA will further enhance either 3xRTT or W-CDMA system’s
performance or capacity.
Quality of Service Challenges
In wireless networks, Quality of Service (QOS) refers to the measure of the performance
for a system reflecting its transmission quality and service availability (e.g., 4G is expected to
have at least a reliability of 99.99%). Supporting QOS in 4G networks will be a major challenge.
When considering QOS, the major hurdles to overcome in 4G include:
Varying rate,
Channel characteristics,
Bandwidth allocations,
Fault tolerance levels, and Handoff support among heterogeneous wireless networks.
Fortunately, QOS support can occur at the packet, transaction, circuit, and network
levels. QOS will be able to be tweaked at these different operating levels, making the network
more flexible and possibly more tolerant to QOS issues. Varying rate channel characteristics
refers to the fact that 4G applications will
Have varying bandwidth and transition rate requirements. In order to provide solid network
access to support the anticipated 4G applications, the 4G networks must be designed with both
flexibility and scalability. Varying rate channel characteristics must be considered to effectively
meet user demand and ensure efficient network management. Spectrum is a finite resource. In
current wireless systems, frequency licensing and efficient spectrum management are key issues.
In 4G systems, bandwidth allocations may still be a concern. Another concern is
interoperability between the signaling techniques that are planned to be used in 4G (e.g., 3xRTT,
W-CDMA). In comparison with current 2G and 2.5G networks, 4G will have more fault
tolerance capabilities built-in to avoid unnecessary network failure, poor coverage, and dropped
calls. 4G technology promises to enhance QOS by the use of better diagnostic techniques and
alarms tools. 4G will have better support of roaming and handoffs across heterogeneous
networks.
Users, even in today’s wireless market, demand service transparency and roaming. 4G
may support interoperability between disparate network technologies by using techniques such
as LAS-CDMA signaling. Other solutions such as software-defined radios could also support
roaming across disparate network technologies in 4G systems. These major challenges to QOS
in 4G networks are currently being studied and solutions are being developed. Developers
believe that QOS in 4G will rival that of any current 2G or 2.5G network. It is anticipated that
the QOS in 4G networks will closely approximate the QOS requirements in the wire line
environment (99.999% reliability).
4G Applications and Their Benefits to
Public Safety
One of the most notable advanced applications for 4G systems is location-based services.
4G location applications would be based on visualized, virtual navigation schemes that would
support a remote database containing graphical representations of streets, buildings, and other
physical characteristics of a large metropolitan area. This database could be accessed by a
subscriber in a moving vehicle equipped with the appropriate wireless device, which would
provide the platform on which would appear a virtual representation of the environment ahead.
For example, one would be able to see the internal layout of a building during an emergency
rescue. This type of application is sometimes referred to as "Telegeoprocessing", which is a
combination of Geographical Information Systems (GIS) and Global Positioning Systems (GPS)
working in concert over a high-capacity wireless mobile system. Telegeoprocessing over 4G
networks will make it possible for the public safety community to have wireless operational
functionality and specialized applications for everyday operations, as well as for crisis
management. The emergence of next generation wireless technologies will enhance the
effectiveness of the existing methods used by public safety. 3G technologies and beyond could
possibly bring the following new features to public safety:
Virtual navigation: As described, a remote database contains the graphical representation of
streets, buildings, and physical characteristics of a large metropolis. Blocks of this database are
transmitted in rapid sequence to a vehicle, where a rendering program permits the occupants to
visualize the environment ahead. They may also "virtually" see the internal layout of buildings to
plan an emergency rescue, or to plan to engage hostile elements hidden in the building.
Tele-medicine: A paramedic assisting a victim of a traffic accident in a remote location
could access medical records (e.g., x-rays) and establish a videoconference so that a remotely
based surgeon could provide “on-scene” assistance. In such a circumstance, the paramedic could
relay the victim's vital information (recorded locally) back to the hospital in real time, for review
by the surgeon.
Crisis-management applications: These arise, for example, as a result of natural disasters
where the entire communications infrastructure is in disarray. In such circumstances, restoring
communications quickly is essential. With wideband wireless mobile communications, both
limited and complete communications capabilities, including Internet and video services, could
be set up in a matter of hours. In comparison, it may take days or even weeks to re-establish
communications capabilities when a wire line network is rendered inoperable.
Limitations of 4G
Although the concept of 4G communications shows much promise, there are still
limitations that must be addressed. One major limitation is operating area. Although 2G
networks are becoming more ubiquitous, there are still many areas not served. Rural areas and
many buildings in metropolitan areas are not being served well by existing wireless networks.
This limitation of today’s networks will carry over into future generations of wireless
systems. The hype that is being created by 3G networks is giving the general public unrealistic
expectations of always on, always available, anywhere, anytime communications. The public
must realize that although high-speed data communications will be delivered, it will not be
equivalent to the wired Internet – at least not at first. If measures are not taken now to correct
perception issues, when 3G and later 4G services are deployed, there may be a great deal of
disappointment associated with the deployment of the technology, and perceptions could become
negative. If this were to happen, neither 3G nor 4G may realize its full potential. Another
limitation is cost. The equipment required to implement a next-generation network is still very
expensive. Carriers and providers have to plan carefully to make sure that expenses are kept
realistic. One technique currently being implemented in Asian networks is a Pay-Per-Use model
of services. This model will be difficult to implement in the United States, where the public is
used to a service-for-free model (e.g., the Internet).
Conclusion
As the history of mobile communications shows attempts have been made to reduce a
number of technologies to a single global standard. Projected 4G systems offer this promise of a
standard that can be embraced worldwide through its key concept of integration. Future wireless
networks will need to support diverse IP multimedia applications to allow sharing of resources
among multiple users. There must be a low complexity of implementation and an efficient means
of negotiation between the end users and the wireless infrastructure. The fourth generation
promises to fulfill the goal of PCC (personal computing and communication)—a vision that
affordably provides high data rates everywhere over a wireless network
4G networks may eventually deliver on all the promises. At times, it seems that
technological advances are being made on a daily basis. These advances will make high-speed
data/voice-over-Internet-protocol (Vo IP) networks a reality. In the meantime, it is important for
industry to develop a strong 3G offering that is palatable for the general public. Equally as
important, industry must ensure that expectations are realistic and that services meet and exceed
those expectations. If all goes according to what the industry envisions, it may be sooner, rather
than later that we will see wireless communications evolve. This evolution will give the general
public as well as the public safety community amazing functionality from the convenience of a
single handheld device.