4G MOBILE COMMUNICATION SYSTEM

 4G (also known as Beyond 3G), an abbreviation for Fourth-Generation, is a term

used to describe the next complete evolution in wirelesscommunications. A 4G

system will be able to provide a comprehensive IP solution where voice, data and

streamed multimedia can be given to users on an "Anytime, Anywhere" basis, and

at higher data rates than previous generations.

As the second generation was a total replacement of the first generation networks

and handsets; and the third generation was a total replacement of second

generation networks and handsets; so too the fourth generation cannot be an

incremental evolution of current 3G technologies, but rather the total replacement

of the current 3G networks and handsets. The international telecommunications

regulatory and standardization bodies are working for commercial deployment of

4G networks roughly in the 2012-2015 time scale. There is no formal definition for

what 4G is; however, there are certain objectives that are projected for 4G. These

objectives include, that 4G will be a fully IP-based integrated system. 4G will be

capable of providing between 100 Mbit/s and 1 Gbit/s speeds both indoors and

outdoors, with premium quality and high security.

1.INTRODUCTION

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 anywhere, 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.

2.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 system would have higher quality voice channels, as well as broadband data

capabilities, up to 2 Mbps. 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 system. 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. However, the demand for higher access speed multimedia 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.

Table 1. Short History of Mobile Telephone Technologies

Symbols:

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 system

GSM = global system for mobile

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

3.VISION OF 4G

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 domain.

The fourth generation will encompass all systems from various networks, public to private;

operator-driven broadband networks to personal areas; and ad hoc networks. 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 network),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.

4.KEY 4G TECHNOLOGIES

Some of the key technologies required for 4G are briefly described below:

4.1 OFDMA

Orthogonal Frequency Division Multiplexing (OFDM) not only provides clear advantages

for physical layer performance, but also a framework

for improving layer 2 performance by proposing an additional degree of free- dom. Using

ODFM, it is possible to exploit the time domain, the space domain, the frequency domain

and even the code domain

to optimize radio channel usage. It ensures very robust transmission in multi-path

environments with reduced receiver complexity.

OFDM also provides a frequency diversity gain, improving the physical layer performance .It

is also compatible with other enhancement

Technologies, such as smart antennas and MIMO.OFDM modulation can also be employed

as a multiple access technology (Orthogonal Frequency Division Multiple Access; OFDMA).

In this case, each OFDM symbol can transmit information to/from several users using a

different set

of sub carriers (sub channels). This not only provides additional flexibility for resource

allocation (increasing the capacity), but also enables cross-layer optimization of radio link

usage.

4.2 SOFTWARE DEFINED RADIO

Software Defined Radio (SDR) benefits from today’s high processing power to develop

multi-band, multi-standard base stations and terminals. Although in future the terminals will

adapt the air interface to the

available radio access technology, at present this is done by the infrastructure.

Several infrastructure gains are expected from SDR. For example,

to increase network capacity at a specific time (e.g. during a sports event),an operator will

reconfigure its network adding several modems at a given Base Transceiver Station (BTS).

SDR makes this reconfiguration easy. In the context of 4G systems, SDR will become an

enabler for the aggregation of multi-standard pico/micro cells. For a manufacturer, this can

be a powerful aid to providing multi-standard, multi-band equipment with reduced

development effort and costs through simultaneous multi-channel processing.

4.3 MULTIPLE-INPUT MULTIPLE –OUTPUT

MIMO uses signal multiplexing between multiple transmitting antennas (space multiplex)

and time or frequency. It is well suited to OFDM, as it is possible to process independent

time symbols as soon as the OFDM waveform is correctly designed for the channel. This

aspect of OFDM greatly simplifies processing. The signal transmitted by m antennas is

received by n antennas. Processing of the received signals may deliver several performance

improvements:range, quality of received signal and

spectrum efficiency. In principle, MIMO is more efficient when many multiple path signals

are received. The performance in cellular

deployments is still subject to research and simulations . However,

it is generally admitted that the gain in spectrum efficiency is directly related to the minimum

number of antennas in the link.

4.4 HANDOVER AND MOBILITY

Handover technologies based on mobileIP technology have been considered for data and

voice. Mobile IP techniques are slow but can be accelerated with classical methods

(hierarchical, fast mobile IP).

These methods are applicable to data and probably also voice. In single-frequency networks,

it is necessary to reconsider the handover methods. Several techniques can be used when the

carrier to interference ratio is negative (e.g. VSFOFDM,bit repetition), but the drawback of

these techniques is capacity. In OFDM, the same alternative exists as in CDMA, which is to

use macro-diversity. In the case of OFDM, MIMO allows macro-diversity processing with

performance gains. However, the implementation of macro-diversity implies that MIMO

processing is centralized and transmissions are synchronous. This is not as complex as in

CDMA, but such a technique should only be used in situations

where spectrum is very scarce.

5.QUALITY OF SERVICE

Traffic generated by the different services will not only increase traffic loads on the

networks, but will also require different quality of service (QoS) requirements (e.g.,

cell loss rate, delay, and jitter) for different streams (e.g., video, voice, data).

Providing QoS guarantees in 4G networks is a non-trivial issue where both QoS

signaling across different networks and service differentiation between mobile flows

will have to be addressed.

One of the most difficult problems that are to be solved, when it comes to IP mobility,

is how to insure the constant QoS level during the handover.

Depending on whether the new access router is in the same or some other

subnetwork, we recognize the horizontal and vertical handover.

However, the mobile terminal can not receive IP packets while the process of

handover is finished. This time is called the handover latency.

Handover latency has a great influence on the flow of multimedia applications in real-

time.

Mobile IPv6 have been proposed to reduce the handover latency and the number of

lost packets.

The field “Traffic Class” and “Flow Label” in IPv6 eader enables the routers to

secure the special QoS for specific packet series with marked priority

6.SECURITY

The heterogeneity of wireless networks complicates the security issue.

Dynamic reconfigurable, adaptive, and lightweight security mechanisms should be

developed.

Security in wireless networks mainly involves authentication, confidentiality,

integrity, and

authorization for the access of network connectivity and QoS

resources for the mobile nodes flow.

AAA (Authentication Authorization Auditing) protocols provide a framework for

such suffered especially for control plane functions and installing security policies in

the mobile node such as encryption, decryption and filtering.

7.BENEFITS

7.1 CONVERGENCE OF CELLULAR MOBILE NETWORKS AND

WLANS

7.1.1 Benefits for Operators:

Higher bandwidths

.

Lower cost of networks and equipment.

The use of licence-exempt spectrum.

Higher capacity and QoS enhancement.

Higher revenue.

7.1.2 Benefits for Users:

Access to broadband multimedia services with lower

cost and where mostly needed.

Inter-network roaming.

7.2 CONVERGENCE OF MOBILE COMMUNICATIONS

AND BROADCASTING

7.2.1 From broadcaster point of view:

Introducing interactivity to their unidirectional point-to multipoint Broadcasting systems.

That is, a broadband downlink based on DAB/DVB-T and a narrowband uplink based on

3G cellular systems.

7.2.2 From the cellular mobile operator point of view:

Providing a complementary broadband downlink in vehicular environments to support IP-

based multi-media traffic which is inherently asymmetrical.

7.3 CONVERGENCE BENEFITS

Broadcasters will benefit from the use of cellular mobile systems to adapt the content of their

multi-media services more rapidly in response to the feedback from customers.

Cellular operators will benefit from offering their customers a range of new broadband multi-

media services in vehicular environments.

Users will benefit from faster access to a range ofbroadband multi-media services with

reasonable QoS and lower cost.

7.4 WIRELESS SYSTEM DISCOVERY

•

A multimode terminal attaches to the WLAN and scans the available systems.

•

It can download suitable software manually or automatically.

Figure 4

.

Wireless System Discovery

7.5 RE-CONFIGURABLE TECHNOLOGY

• In order to use the large variety of services and wireless networks, multimode user

terminals are essential as they can adapt to different wireless networks by reconfiguring

themselves.

• This eliminates the need to use multiple terminals (or multiple hardware components in a

terminal).

• The most promising way of implementing multimode

user terminals is to adopt the software radio approach.

An ideal software radio receiver

Figure 5

.

SDR(Software Defined Radio)

RE-CONFIGURABLE TECHNOLOGY

CHALLENGES:

• Regulatory and Standardisation issues

• Business models

• User preference profiles

• Inter-system handover mechanisms and criteria

• Software download mechanisms

• Flexible spectrum allocation and sharing between operators

RE-CONFIGURABLE TECHNOLOGY

BENEFITS FOR:

USERS:

•

Select network depending on service requirements and cost.

•

Connect to any network – Worldwide roaming.

•

Access to new services.

OPERATORS:

•

Respond to variations in traffic demand (load balancing).

•

Incorporate service enhancements and improvements.

•

Correction of software bugs and upgrade of terminals.

•

Rapid development of new personalised and customised services.

MANUFACTURERS:

•

Single platform for all markets.

•

Increased flexible and efficient production.

PERSONAL MOBILITY:

In addition to terminal mobility, personal mobility is a concern in mobility

management.

Personal mobility concentrates on the movement of users instead of users’ terminals,

and involves the provision of personal communications and personalized operating

environments.

Once the caller’s agent identifies user’s location, the caller’s agent can directly

communicate with his agent.

8.APPLICATIONS

8.1 VIRTUAL PRESENCE

: This means that 4G provides user services at all times,

even if the user is off-site.

8.2 VIRTUAL NAVIGATION

: 4G provides users with virtual navigation through

which a user can access a database of the streets, buildings etc.

8.3 TELE-GEOPROCESSING APPLICATIONS

: This is a combination of

GIS(Geographical Information System) and GPS (Global Positioning System) in which a

user can get the location by querying.

8.4 TELE-MEDICINE AND EDUCATION

:

4G will support remote health

monitoring of patients. For people who are interested in life long education, 4G provides a

good opportunity.

8.5 CRISIS MANAGEMENT

:

Natural disasters can cause break down in

communication systems. In today’s world it might take days or 7 weeks to restore the system.

But in 4G it is expected to restore such crisis issues in a few hours.

8.6 MULTIMEDIA – VIDEO SERVICES

4G wireless systems are expected to deliver efficient multimedia services at very high

data rates.

Basically there are two types of video services: bursting and streaming video services.

Streaming is performed when a user requires real-time video services, in which the

server delivers data continuously at a playback rate.

Bursting is basically file downloading using a buffer and this is done at the highest

data rate taking advantage of the whole available bandwidth.

9.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 is expected to be launched by 2010 and the world is looking forward

for the most intelligent technology that would connect the entire globe.

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