ABSTRACT: The number of subscribers for mobile

communications has increased much

faster than predicted. In the year 2010,

more than 1.8 billion mobile subscribers

are anticipated. The majority of traffic is

changing from speech oriented

communication to multimedia

communication. The major step from

second generation to third generation

and further to fourth generation was the

ability to support advanced and

wideband services including e-mail, file

transfers and distribution services like

radio, TV and software provisioning, In

this paper we address about the 4TH G

mobile communications.

The Fourth Generation (4G) Mobile

Communications not only focuses on the

data-rate increase and new air

interface.4G Mobile converges the

advanced wireless mobile

communications and high-speed wireless

access systems into an Open Wireless

Architecture (OWA) platform which

becomes the core of this emerging next

generation mobile technology. Based on

this OWA model, 4G mobile will deliver

the best business cases to the wireless

and mobile

industries,i.e.cdma2000/WLAN/GPRS

3-in-1 product,

WCDMA/OFDM/WLAN 3-in-1

product, etc. Asia-Pacific is the most

dynamic market of new generation

mobile communications with over $100

Billion businesses in the next decade.

The 4G mobile technology -

convergence of wireless mobile and

wireless access, will definitely drive this

growth. Any single-architecture wireless

system, including 3G, HSDPA, WiMax,

etc., is a transitional solution only, and

will be replaced by open wireless

architecture system very soon where

various different wireless standards can

be integrated and converged on this open

platform.

.

The advent of 4G wireless

systems has created many research

opportunities. The expectations from 4G

are high in terms of data rates, spectral

efficiency, mobility and integration.

Orthogonal Frequency Division

Multiplexing (OFDM) is proving to be a

possible multiple access technology to

be used in 4G. But OFDM comes with

its own challenges like high Peak to

Average Ratio, linearity concerns and

phase noise. This paper proposes a

solution to reduce Peak to Average Ratio

by clipping method. ATLAB as used to

generate the OFDM signal to prove that

clipping does reduce Peak to Average

Ratio.

INTRODUCTION:

The first operational cellular

communication system was deployed in

the Norway in 1981 and was followed

by similar systems in the US and UK.

These first generation systems provided

voice transmissions by using frequencies

around 900 MHz and analogue

modulation.

The second generation (2G) of the

wireless mobile network was based on

low-band digital data signaling. The

most popular 2G wireless technology is

known as Global Systems for Mobile

Communications (GSM). The first GSM

systems used a 25MHz frequency

spectrum in the 900MHz band.

Planning for 3G started

in the 1980s. Initial plans focused on

multimedia applications such as

videoconferencing for mobile phones.

When it became clear that the real killer

application was the Internet, 3G thinking

had to evolve. As personal wireless

handsets become more common than

fixed telephones, it is

clear that personal wireless Internet

access will follow and users will want

broadband Internet access wherever they

go.

.

2G 3G 4G

The objective of the 3G was to develop a

new protocol and new technologies to

further enhance the\mobile experience.

In contrast, the new 4G framework to be

established will try to accomplish new

levels of user experience and multi-

service capacity by also integrating all

the mobile technologies that exist (e.g.

GSM - Global System for Mobile

Communications, GPRS - General

Packet Radio Service, IMT-2000 -

International Mobile Communications,

Wi-Fi - Wireless Fidelity, Bluetooth).In

spite of different approaches, each

resulting from different visions of the

future platform currently under

investigation, the main objectives of 4G

networks can be stated in the following

properties:

Ubiquity;

Multi-service platform;

Low bit cost

To achieve the proposed goals, a very

flexible network that aggregates various

radio access technologies, must be

created. This network must provide high

bandwidth, from 50-100 MHz for high

mobility users, to 1GHz for low mobility

users, technologies that permit fast

handoffs, an efficient delivery.

Migrating to 4G: The fact that 4G mobile networks intend

to integrate almost every wireless

standard already in use, enabling its

simultaneous use and interconnection

poses many questions not yet answered.

The research areas that present key

challenges to migrate current systems to

4G are many but can be summarized in

the following: Mobile Station, System

and Service. To be able to use 4G

mobile networks a new type of mobile

terminals must be conceived. The

terminals to be adopted must adapt

seamless to multiple wireless networks,

each with different protocols and

technologies. Auto reconfiguration will

also be needed so that terminals can

adapt to the different services available.

This adaptation may imply that it must

download automatically configuration

software from networks in range.

Moreover terminals must be able to

choose from all the available wireless

networks the one to use with a specific

service. To do this it must be aware of

specifications of all the networks in

terms of bandwidth, QoS supported,

costs and respect to user preferences.

Terminal mobility will be a key factor to

the success of 4G networks. Terminals

must be able to provide wireless services

anytime, everywhere. This implies that

roaming between different networks

must be automatic and transparent to the

user. There are two major issues in

terminal mobility, location management

and handoff management Location

management deals with tracking user

mobility, and handling information

about original, current and (if possible)

future cells. Moreover it must deal with

authentication issues and QoS

assurances. Handoff management

primary objective is to maintain the

communications while the terminal

crosses wireless network boundaries. In

addition, 4G networks, in opposition to

the other mobile generations, must deal

with vertical and horizontal handoffs,

i.e., a 4G mobile client may move

between different types of wireless

networks (e.g. GSM and Wi-Fi) and

between cells of the same wireless

network (e.g. moving between adjacent

GSM cells). Furthermore, many of the

Services available in this new mobile

generation like videoconference have

restricted time constraints and QoS

needs that must not be perceptible

affected by handoffs. To avoid these

problems new algorithms must be

researched and a prevision of user

mobility will be necessary, so as to avoid

broadcasting at the same time to all

adjacent antennas what would waste

unnecessary resources. Another major

problem relates to security, since 4G

pretends to join many different types of

mobile technologies, as each standard

has its own security scheme, the key to

4G systems is to be highly flexible.

Services also pose many questions as 4G

users may have different operators to

different services and, even if they have

the same operator, they can access data

using different network technologies.

Actual billing using flat rates, time or

cost per bit fares, may not be suitable to

the new range of services. At the same

time it is necessary that the bill is well

understood by operator and client. A

broker system would be advisable to

facilitate the interaction between the user

and the different service providers.

Another challenge is to know, at each

time, where the user is and how he can

be contacted. This is very important to

mobility management. A user must be

able to be reached wherever he is, no

matter the kind of terminal that is being

used. This can be achieved in various

ways one of the most popular being the

use of a mobile-agent infrastructure. In

this framework, each user has a unique

identifier served by personal mobile

agents that make the link from users to

Internet.

Multi-technology Approach: Orthogonal Frequency Division Multiplexing (OFDM)

Open wire less Architecture(OWA)

Multiple-input multiple-output ( MIMO )

GENERIC MIMO AND OFDM:

Increasing demand for high performance

4G broadband wireless mobile calls for

use of multiple antennas at both base

station and subscriber ends. Multiple

Antenna technologies enable high

capacities suited for Internet and

multimedia services and also

dramatically increase range and

reliability. This design is motivated by

the growing demand for broadband

wireless Internet access. The challenge

for wireless broadband access lies in

providing a comparable quality of

service for similar cost as competing

wire line technologies. The target

frequency band for this system is 2 to 5

GHz due to favorable propagation

characteristics and low radio-frequency

(RF) equipment cost. The broadband

channel is typically non LOS channel

and includes impairments such as time

selective fading and frequency-selective

fading. Multiple antennas at the

transmitter and receiver provide

diversity in a fading environment. By

employing multiple antennas, multiple

spatial channels are created and it is

unlikely all the channels will fade

simultaneously.

OFDM is chosen over a single carrier

solution due to lower complexity of

equalizers for high delay spread

channels or high data rates. A broadband

signal is broken down into multiple

narrowband carriers (tones), where each

carrier is more robust to multipath. In

order to maintain orthogonality amongst

tones, a cyclic prefix is added which has

length greater than the expected delay

spread. With proper coding and

interleaving across frequencies,

multipath turns into an OFDM system

advantage by yielding frequency

diversity. OFDM can be implemented

efficiently by using FFT's at the

transmitter and receiver .At the receiver,

FFT reduces the channel response into a

multiplicative constant on a tone-by-tone

basis .With MIMO, the channel response

becomes a matrix. Since each tone can

be equalized independently, the

complexity of space time equalizers is

avoided.

Multipath remains an advantage for a

MIMO-OFDM system since frequency

selectivity caused by multipath improves

the rank distribution of the channel

matrices across frequency tones, thereby

increasing capacity.

OPENWIRELESSARCHITECTURE:

The 4G Mobile communications will be

based on the Open Wireless Architecture

(OWA) to ensure the single terminal can

seamlessly and automatically connect to

the local high-speed wireless access

systems when the users are in the

offices, homes, airports or shopping

centers where the wireless access

networks (i.e. Wireless LAN, Broadband

Wireless Access, Wireless Local Loop,

HomeRF, Wireless ATM, etc) are

available. When the users move to the

mobile zone (i.e. Highway, Beach,

Remote area, etc.), the same terminal

can automatically switch to the wireless

mobile networks (i.e.GPRS, W-CDMA,

cdma2000, TD-SCDMA, etc.).This

converged wireless communications can

provide the following advantages.

_

Greatly increase the spectrum efficiency

mostly ensures the highest data-rate to

the wireless terminal. Best share the

network resources and channel

utilization optimally manages the service

quality and multimedia applications. 3G

wireless LAN and other wireless access

technologies will be converged into 4G

mobile platform to deliver the best

infrastructure of mobile communications

with optimal spectrum efficiency and

resource management. In fact, this OWA

model had already been accepted by

most wireless industries, for example,

the W-CDMA/W-LAN/Bluetooth 3-in-1

terminal is being designed in many

companies. The global 4G Mobile R&D

focuses on the following Open Wireless

Architecture:

GOAL:

The goal of 4th Generation (4G) mobile

communications technologies is to

realize wireless communications at the

same high data rate as is made possible

through use of the fiber-optic

transmission systems that are available

today. Realization of 4G mobile

communications is foreseen in the early

2010s, but various precursor

technologies and services have been

appearing as of late. A scrutiny on the

market trends, along with a close watch

on carrier reaction as to the introduction

of the Mobile Number Portability

(MNP) system planned for October 24,

2006, is of vital importance at this time

for all those interested in this business

field

.

Conclusion: In this paper we

present the evolution of mobile

communications through all its

generations. From the initial speech

vocation to an IP-based data network,

several steps were made. From the analog

voice centric first generation to the digital

second generation, the goal was to

enhance the voice experience of a user, by

improving the quality of the

communication while using more

efficiently the installed capacity. At the

same time the enhanced mobility provided

by seamless handover and the additional

data communications capacity (although

very small) advanced and opened the

doors to future developments Some of the

developments was brought by generation

2.5 namely by GPRS, which improved

data communications by supporting IP in

the GSM infrastructure. With the third

generation the goal changed from voice-

centric to data-centric. Moreover total

ability became an objective to pursuit. In

this generation it is possible to combine

voice, lntermedia applications and

mobility in a never experienced manner.

However, the global mobility, while an

important objective, was never really

reached. At the same time new

applications demand more bandwidth and

lower costs. The newcomer fourth-

generation tries to address this problem by

integrating all different wireless

technologies. In spite of all the evolving

technologies the final success of new

mobile generations will be dictated by the

new services and contents made available

to users. These new applications must

meet user expectations, and give added

value over existing offers.

6. References: [1] “Mobile cellular, subscribers per

100 people”, International

Telecommunication Union Statistics,

2002

http://www.itu.int/ITU-D/ict/statistics

/at_glance/cellular02.pdf

[2] Kim, Y., Jeong, B.J., Chung, J.,

Hwang, C., Ryu, J.S., Kim, K., Kim,

Y.K., “Beyond 3G: Vision,

Requirements, and

Enabling Technologies”, IEEE

Communications Magazine, March

2003, pp. 120-124

[3] ITU-R PDNR WP8F, “Vision,

Framework and Overall Objectives of

the Future Development of IMT-2000

and

Systems beyond IMT-2000,” 2002.

[4] “2G – 3G Cellular Wireless data

transport terminology”, Arc Electronics

www.arcelect.com/2G-

3G_Cellular_Wireless.htm

[5] Schiller, J., “Mobile

Communications”, slides

http://www.jochenschiller.de/

[6] Tachikawa, Keiji, “A perspective on

the Evolution of Mobile

Communications”, IEEE

Communications Magazine,

October 2003, pp. 66-73

[7] Hui, Suk Yu, and Yeung, Kai Hau,

“Challenges in the Migration to 4G

Mobile Systems”, IEEE

Communications

Magazine, December 2003, pp. 54-

59eamless handover and the additional

data communications