4G mobile communications (The future technology of mobiles)

ABSTRACT

4G is a short for fourth generation

cellular communication systems. It is a

network that operates on Internet

technology, combines it with other

applications and technologies such as

Wi-Fi and WiMAX, and runs at speeds

ranging from 100 Mbps (in cell-phone

networks) to 1 Gbps (in local Wi-Fi

networks). The key concept is integrating

the 4G capabilities with all of the

existing mobile technologies through

advanced technologies. The key

technologies like OFDM, Multi-antenna

systems, SDR are useful in making 4G a

reality. The transmission of multimedia

applications at faster rates is achieved

by Cache and Pico-cell methods. The

factors like low cost, high speed data

transfer; increased microprocessor

performance has moved the 4G forward.

The 4G is successfully implemented in

Japan and soon South Korea will follow

it. The killer application of 4G is not

clear, though the improved bandwidths

and data throughput offered by 4G

networks should provide opportunities

for previously impossible products and

services to be released. One of the terms

used to describe 4G is MAGIC (Mobile

multimedia, Anytime anywhere, Global

mobility support, Integrated wireless

solution, and Customized personal

service.)

INDEX

1. Introduction 2. Evolution 3. Objectives 4. Key 4G technologies 4.1 OFDMA 4.2 Multi Antenna systems 4.3 Software defined radio 4.4 Caching and Pico cells5. Access schemes6. Coverage 7. Drivers 8.Features 9. Applications10. Conclusion11. References

1. INTRODUCTION

The 4G will be a fully IP-based

integrated system of systems and

network of networks achieved after the

convergence of wired and wireless

networks as well as computer, consumer

electronics, communication technology,

and several other convergences that will

be capable of providing 100 Mbps and

1Gbps, respectively, in outdoor and

indoor environments with end-to-end

QoS and high security, offering any

kind of services anytime, anywhere, at

affordable cost and one billing. The

Wireless World Research Forum

(WWRF) defines 4G as a network that

operates on Internet technology,

combines it with other applications and

technologies such as Wi-Fi and

WiMAX, and runs at speeds ranging

from 100 Mbps (in cell-phone networks)

to 1 Gbps (in local Wi-Fi networks). 4G

is not just one defined technology or

standard, but rather a collection of

technologies and protocols to enable the

highest throughput, lowest cost wireless

network possible. The official

designation from the IEEE for 4G is

beyond 3G (B3G). 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.

2.EVOLUTION The first generation (1G) mobile

systems were designed in 1970 to offer a

single service i.e. speech. These are

implemented on analog technology and

basic cellular technology of mobile

communications.

Second generation (2G) mobile systems

were also primarily designed to offer

speech with a limited capability to offer

data at low rates in 1980’s but based on

digital technology including digital

signal processing techniques. These 2G

systems provided circuit-switched data

communication services at a lower

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),CDMA(Code Division Multiple

Access).these systems operate

nationwide or internationally and are

today’s mainstream systems although the

data rates in these systems are limited.

3G mobile systems are expected

to offer high-quality multimedia services

and operate in different environments. It

was designed in 1990’s for higher

quality voice channels and broadband

data capabilities upto 2Mbps.

Limitations of 3G :

Difficulty of CDMA to provide

higher data rates

For high speed data rates and

band width to meet multimedia

requirements.

Limitation of spectrum and its

allocation.

Inability to roam between

different services.

To provide a seamless transport

end-to-end mechanism.

To introduce a better system

with reduced cost.

All the above limitations and demand

for higher access speed multimedia

communication in today’s society which

greatly depends upon computer

communication in digital format seems

unlimited. This led to the research and

evolution of fourth generation (4G).

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

.

3. OBJECTIVES

To cater the quality of service and rate

requirements set by the forthcoming

applications like wireless broadband

access, Multimedia Messaging Service,

video chat, mobile TV,

High definition TV content, DVB and

minimal service like voice and data at

anytime and anywhere, the 4G working

groups have defined the following as the

objectives of the 4G wireless

communication standard

Spectrally efficient system (in

bits/s/Hz and bit/s/Hz/site)[6]

High network capacity[7]

Nominal data rate of 100 Mbps at

high speeds and 1 Gbps at

stationary conditions as defined

by the ITU-R[1]

Data rate of at least 100 Mbps

between any two points in the

world[1]

Smooth handoff across

heterogeneous network[8]

Seamless connectivity and global

roaming across multiple

networks[9]

High quality of service for next

generation multimedia support

(real time audio, high speed data,

HDTV video content, mobile

TV, etc)[9]

Interoperable with the existing

wireless standards[10]

All IP system, packet switched

network[9]

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 frame work for

improving layer 2 performance by

proposing an additional degree of

freedom

OFDM

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. As shown in Figure 5, the

signal is split into orthogonal sub

carriers, on each of which the signal is

“narrowband” (a few kHz) and therefore

immune to multi-path effects, provided a

guard interval is inserted between each

OFDM symbol. 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.

Summary of advantages Can easily adapt to severe

channel conditions without complex equalization

Robust against narrow-band co-channel interference

Robust against Intersymbol interference (ISI) and fading caused by multipath propagation

High spectral efficiency Efficient implementation using

FFT Low sensitivity to time

synchronization errors Tuned sub-channel receiver

filters are not required (unlike conventional FDM)

4.2. Multi-antenna Systems

In the early 90s, to cater the growing

data rate needs of data

communication, many transmission

schemes were proposed. One

technology, spatial multiplexing,

gained importance for its bandwidth

conservation and power efficiency.

Spatial multiplexing involves

deploying multiple antennas at the

transmitter and at the receiver.

Independent streams can be

transmitted simultaneously from all

the antennas. This increases the data

rate into multiple folds with the

number equal to minimum of the

number of transmit and receive

antennas.

This is called as Multiple-input multiple-

output communications (MIMO). Apart

from this, the reliability in transmitting

high speed data in the fading channel can

be improved by using more antennas at the

transmitter or at the receiver. This is called

transmit or receive diversity.

FIGURE:SPACE TIME CODING FOR

MIMO SYSTEMS

ADVANTAGES:

Increases data rates due to

multiple transmit and receive

antennas

Combats fading

Increases base station-to-user

capacity

Cost is scalable with

performance

4.3. Software Defined Radio (SDR)

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 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 simultaneous

multi-channel processing

.

4.4. Caching and Pico Cells

Memory in the network and terminals

facilitates service delivery. In cellular

systems,

This extends the capabilities of the MAC

scheduler, as it facilitates the delivery of

real-time services. Resources can be

assigned to data only when the radio

conditions are favorable. These methods

can double the capacity of a classical

cellular system. In pico cellular

coverage, high data rate (non-real-time)

services can be delivered even when

reception/transmission is interrupted for

a few seconds. Consequently, the

coverage zone within which data can be

received/transmitted can be designed

with no constraints other than limiting

interference. Data delivery is preferred

in places where the bit rate is a

maximum. Between these areas, the

coverage is not used most of the time,

creating an apparent discontinuity. In

these areas, content is sent to the

terminal cache at the high data rate and

read at the service rate. Coverages are

“discontinuous”.The advantage of

coverage, especially when designed with

caching technology, is high spectrum

efficiency, high scalability (from 50

to500 bit/s/Hz), high capacity and lower

cost. A specific architecture is needed to

introduce cache memory in the network.

An example is shown. At the entrance of

the access network, lines of cache at the

destination of a terminal are built and

stored. When a terminal enters an area in

which a transfer is possible, it simply

asks for the line of cache following the

last received. Between the terminal and

the cache. A simple, robust and reliable

protocol is used between the terminal

and the cache for every service delivered

in this type of coverage.

PICO CELL NETWORK DESIGN

Multimedia service delivery, service

adaptation and robust transmission

Audio and video coding is scalable. For

instance, a video flow can be split into

three Flows which can be transported

independently: one base layer (30

kbit/s), which is a robust flow but of

limited quality (e.g.5 images/s), and two

enhancement flows (50 kbit/s and 200

kbit/s). The first flow provides

availability, the other two quality and

definition. In a streaming situation, the

terminal will have three caches. In pico

cellular coverage, the parent coverage

establishes the service dialog and service

start-up(with the base layer). As soon as

the terminal enters Pico cell coverage,

the terminal caches are filled, starting

with the base cache.

Video (and audio) transmissions are

currently transmitted without error and

without packet loss. However, it is

possible to allow error rates of about 10-

5 /10-6 and a packet loss around 10-

2/10-3. Coded images still contain

enough redundancy for error correction.

It is possible to gain about 10 dB in

transmission with a reasonable increase

in complexity. Using the described

technologies, multimedia transmission

can provide a good quality.

5. ACCESS SCHEMES

The existing wireless standards use

TDMA, FDMA, CDMA and

combinations of these to multiplex

multiple mobile stations (handsets, etc)

use of spectrum, with CDMA (IS-2000,

W-CDMA, TD-CDMA, TD-SCDMA)

dominating the 3G space. However, all

these technologies are limited; TDMA

suffers from inherent inefficiencies due

to the need for guard periods between

frames, and CDMA from poor spectrum

flexibility and scalability.

Recently, new access schemes like

OFDMA, Single Carrier FDMA, and

MC-CDMA have been proposed as part

of the upcoming next generation UMTS,

802.16e and 802.20 standards. These

offer the same efficiencies as older

technologies like CDMA, but offer

advantages in scalability.

In addition to improvements in these

multiplexing systems, improved

modulation techniques are being used.

Whereas earlier used to mitigate the

dwindling number of IPv4 addresses.

In the context of 4G, IPv6 also enables a

number of applications with better multi-

cast, security and route optimization

capabilities. With the available address

space and number of addressing bits in

IPv6, many innovative coding schemes

can be developed for 4G devices and

applications that could aid deployment

of 4G networks and services.

6. COVERAGE Coverage is achieved by adding

new technologies (possibly in overlay

mode) and progressively enhancing

density. Take a WiMAX deployment, for

example: first the parent coverage is

deployed; it is then made denser by

adding discontinuous pico cells, after

which the pico cell is made denser but

still discontinuously. Finally the pico cell coverage is made continuous

either by using MIMO or by deploying

another pico cell coverage in a different

frequency band .Parent coverage

performance may vary from 1 to 20

bit/s/Hz/km?, while pico cell technology

can achieve from 100 to

500bit/s/Hz/km?, depending on the

complexity of the terminal hardware and

software.

7. DRIVERS OF 4G

In the future, low cost, high speed data

will drive forward the fourth generation

(4G) as

Short-range communication emerges.

Service and application ubiquity, with a

high degree of personalization and

synchronization between various user

appliances, will be another driver. At the

same time, it is probable that the radio

access network will evolve from a

centralized architecture to a distributed

one.

Technological drivers:

Microprocessor performance

increase (Moore's law)

Battery performance increase (a

much slower exponential curve

than Moore's Law) (batteries are

the big bottleneck)

Air interfaces with increasingly

better spectral efficiency*

Better processor

performance/power consumption

ratio

Handset display power

consumption efficiency

8. FEATURES OF 4G

Support interactive

multimedia,

voice,wireless internet,

video services.

High speed, high capacity

and low cost per bit.

Global mobility, service

portability and scalable

mobile networks.

Seamless switching,

variety of services based

on Quality of

Service(QoS)

Better scheduling and call

admission control

techniques

Ad hoc and multi hop

networks

9. APPLICATIONS

Already at rates of 15-30 Mbps, 4G

should be able to provide users with

streaming high-definition television. At

rates of 100 Mbps, the content of a

DVD, for example a movie, can be

downloaded within about 5 minutes for

offline access.

Few applications are as follows:

Virtual presence : 4G provides

user services at all times, even if

user is off site.

Virtual navigation : 4G provides

user with virtual navigation

through which a user can access

a database of streets, buildings

etc .

Tele-geoprocessing : this is a

combination of GIS (Geographical

information system) and GPS

(Global Positioning System) by

which we can get location by

querying.

4G can be used in Tele-medicine

and education

Crisis management : natural

disasters can cause breakdown in

communication systems. In today’s

world it might take days or weeks

to restore the system, but in

4G it is expected to restore such

crisis issues in a few hours.

10. CONCLUSIONThe provision of megabit/s data rates to

thousands of radio and mobile terminals

per square kilometer presents several

challenges. Some key technologies

permit the progressive introduction of

such networks without jeopardizing

existing investment. Disruptive

technologies are needed to achieve high

capacity at low cost, but it can still be

done in a progressive manner. The key

enablers are:

• Sufficient spectrum, with associated

sharing mechanisms.

• Coverage with two technologies:

parent (2G, 3G, WiMAX) for real-time

delivery, and discontinuous pico cell for

high data rate delivery.

• Caching technology in the network and

terminals.

• OFDM and MIMO.

• IP mobility.

• Multi-technology distributed

architecture.

• Fixed-mobile convergence (for indoor

service).

• Network selection mechanisms.

4G seems to be a very promising

generation of wireless communication

that will change the people’s life in

wireless world. It is expected to be

launched by 2010 and the world is

looking forward for the most intelligent

technology that would connect the entire

world.

Thus we can

conclude that using 4G concept the

user has freedom and flexibility to

select any desired service with

reasonable QoS and affordable price,

anytime anywhere.

11. REFERENCES C. R. Casal, F. Schoute, and R.

Prasald, “A novel concept for

fourth generation mobile

multimedia communication.”

T. Ottosson, A. Ahl´en, A.

Brunstr¨om, M. Sternad and A.

Svensson, “Toward 4G IP-based

wireless systems: A proposal

for the uplink.” 5th Wireless

World Research Forum.

www.4gfeatures.com

www.4gheterogeneousnetworks.

com

Ambient Networks Project An EU financed research project for "Mobile and Wireless Systems Beyond 3G".

BG Evans and K.Baughan

“visions of 4G”

ECE journal, Dec2002.

ABBREVIATIONS

OFDM: Orthogonal Frequency

Division Multiplexing

SDR: Software Defined Radio

QoS: Quality of Service

WLAN: Wireless Local Area

Network

MIMO: Multiple Input Multiple

Output

DVB: Digital Video

Broadcasting

HDTV: High Definition Television