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Table of contents

Chapter 1 Introduction 7

Chapter 2 Service Evolution

2.1 Dimensioning Targets

2.2 Dimensioning Objectives

2.3 Multi-technology Approach

13

14

15

15

Chapter 3 The User-centric system

3.1 Key Features of 4G

3.1.1 User Friendliness and User Personalization

3.1.2 Terminal Heterogeneity and Network

Heterogeneity

17

18

18

19

Chapter 4 The Real Technical Step-Up of 4G

4.1 Integration of Heterogeneous Systems

4.2 System Design Rules

4.3 Provisioning of Heterogeneous Services

4.4 Multimode/Reconfigurable and Interworking

Devices

22

23

24

25

27

Chapter 5 Key 4G Technologies

5.1 OFDMA

5.2 Software-defined Ratio

5.3 Multiple input Multiple output

5.5 Caching and Pico cells

5.6 Coverage

30

31

32

32

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Chapter 6 Conclusion 36

Appendices

Bibliography

List of Figures

Glossary

37

37

38

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Abstract

The ever-increasing growth of user demand, the limitations of the third generation of wireless mobile

communication systems and the emergence of new mobile broadband technologies on the market have

brought researchers and industries to a thorough reflection on the fourth generation. Many prophetic visionshave appeared in the literature presenting 4G as the ultimate boundary of wireless mobile communication

without any limit to its potential, but in practical terms not giving any design rules and thus any definition of

it.

The evolution from 3G to 4G will be driven by services that offer better quality (e.g. video and

sound) thanks to greater bandwidth, more sophistication in the association of a large quantity of information,

and improved personalization. Convergence with other network (enterprise, fixed) services will come about

through the high session data rate. It will require an always-on connection and a revenue model based on a

fixed monthly fee. The impact on network capacity is expected to be significant. Machine-to-machine

transmission will involve two basic equipment types: sensors (which measure parameters) and tags (which

are generally read/write equipment). It is expected that users will require high data rates, similar to those on

fixed networks, for data and streaming applications. Mobile terminal usage (laptops, Personal digital

assistants, and handhelds) is expected to grow rapidly as they become more user friendly. Fluid high quality

video and network reactivity are important user requirements. Key infrastructure design requirements

include: fast response, high session rate, high capacity, low user charges, rapid return on investment for

operators, investment that is in line with the growth in demand, and simple autonomous terminals.

Chapter 1 Introduction

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1Introduction

The Second Generation of Mobile Communication Systems (2G) was a huge success story because of

its revolutionary technology and the services brought to its customers. Besides high quality speech service,

global mobility was a strong reason for buying 2G terminals. The Third Generation (3G) has been started in

some parts of the world, but the success story of 2G is hard to be repeated . One reason is that the evolution

from 2G towards 3G has not brought any qualitatively new service for the customer, leaving the business

model largely unchanged. The well known services plus someadditional ones are provided, which may not

be enough to encourage the customers to change their equipment.

The lack of innovative services was encountered too late by the 3G Partnership Project(3GPP). In

the latest documents, an attempt was made to incorporate some advanced services into the 3GPP

architecture such as the Multimedia Broadcastand Multicast Service Center(MBMS) in combination with

theIP Multimedia System (IMS). However, these smaller corrections were made without the possibility to

adjust the access technology properly .

The upcoming Fourth Generation (4G) is projected to solve still-remaining problems of the

previous generation and to provide a convergence platform for a wide variety of new services, from high-

quality voice to high-definition video, through high-data-rate wireless channels. Various visions of 4G have

emerged recently among the telecommunication industries, the universities and the research institutes all

over the world .

There has been tremendous interest recently in the Fourth Generation (4G) mobile communication

technologies on the worldwide basis. Research and development on 4G technologies mainly focus on two

directions: Open Wireless Architecture (OWA), and Cost-effective and spectrum-efficient high-speed

wireless transmission. It is well predicted that the business of 4G industries will be over $800 billion by the

year 2020, and therefore major developed countries have already spent huge R&D funds on this emerging

communication technology.

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In Europe, the European Commission (EC) envisions that 4G will ensure seamless service

provisioning across a multitude of wireless systems and networks, from private to public, from indoor to

wide area, and provide an optimum delivery via the most appropriate (i.e., efficient) network available.

From the service point of view, it foresees that 4G will be mainly focused on personalized services . In Asia,

the Japanese operator NTT DoCoMo has introduced the concept of MAGIC for defining 4G: Mobile

multimedia; anytime, anywhere, anyone; Global mobility support; integrated wireless solution; and

Customized personal service, which mostly focuses on public systems and treats 4G as the extension of 3G

cellular service.This view is referred to as the linear 4G vision and, in essence, focuses on a future 4G

network that will generally have a cellular structure and will provide very high data rates (exceeding 100

Mb/s). In general, the latter is also the main tendency in China and South Korea . Nevertheless, even if 4G is

named as the successor of the previous generations, the future is not limited to cellular systems and 4G

should not be seen exclusively as a linear extension of 3G.

India aims to leapfrog to 4G (fourth-generation) wireless technologies, skipping 3G technologies as

it has not been found to be cost-effective. Even if 4G is named as the successor of previous Wireless

communication generations, it is not limited to cellular systems, therefore has not to be exclusively

understood as a linear extension of 3G.Figure1 shows the shift in paradigm.

There is clearly a need for a methodological change in the design of 4G. Indeed, in order to boost

innovation and define and solve relevant technical problems, the system-level perspective has to be

envisioned and understood with a broader view, taking the user as its departing point. This user-centric

approach can result in a beneficial method for identifying innovation topics at all the different protocol

layers and avoiding a potential mismatch in terms of service provisioning and user expectations. A new

user-centric methodology that considers users as the cornerstone in the design of 4G and identifies their

functional needs and expectations, reflecting and illustrating them in everyday life situations is needed. In

this way, fundamental user scenarios that implicitly reveal the key features of 4G, which are then expressed

explicitly in a new framework the user-centric system that describes the various level of

interdependency among them. This approach consequently contributes to the identification of the realtechnical step-up of 4G with respect to 3G and thus to a less prophetic and more pragmatic definition of the

forthcoming technology.

.

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Figure 1 Evolution from 2G to 4G[i]

While 2G was focused on full coverage for cellular systems offering only one technology and 3G

provides its services only in dedicated areas and introduces the concept of vertical handover through the

coupling with Wireless LocalArea Network(WLAN) systems, 4G will be a convergence platform extended

to all the network layers. Moreover, in order to boost the innovation and define and solve relevant technical

problems, it has to be envisioned and understood the system level at a broader view, taking primarily into

account the user. This approach can result in a beneficial method for identifying innovation topics at all thedifferent protocol layers. There is clearly a need for a methodological change in the design of the next

wireless communication generation

The design should be more user-centric to avoid potential flop of the system. Finally, it is also

worth to highlight that the forthcoming technology should be as less dependent as possible from any

geographical matter, addressing very different markets, such as Europe, Asia, and America.

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Chapter 2 Service Evolution

2.1 Dimensioning Targets

2.2 Dimensioning Objectives


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2Service Evolution

The evolution from 3G to 4G will be driven by services that offer better quality (e.g. video and

sound) thanks to greater bandwidth, more sophistication in the association of a large quantity of information,

and improved personalization. Convergence with other network (enterprise, fixed) services will come about

through the high session data rate. It will require an always-on connection and a revenue model based on a

fixed monthly fee. The impact on network capacity is expected to be significant. Machine-to-machine

transmission will involve two basic equipment types: sensors (which measure parameters) and tags (whichare generally read/write equipment). It is expected that users will require high data rates, similar to those on

fixed networks, for data and streaming applications[iv].

Mobile terminal usage (laptops, Personal digital assistants, handhelds) is expected to grow rapidly as

they become more user friendly. Fluid high quality video and network reactivity are important user

requirements. Key infrastructure design requirements include: fast response, high session rate, high

capacity, low user charges, rapid return on investment for operators, investment that is in line with the

growth in demand, and simple autonomous terminals.

The infrastructure will be much more distributed than in current deployments, facilitating the

introduction of a new source of local traffic: machine-to-machine. Figure 2 shows one vision of how

services are likely to evolve; most such visions are similar.

Figure 2 Service Evolution Vision

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2.1 Dimensioning targets

A simple calculation illustrates the order of magnitude. The design target in terms of Radio

performance is to achieve a scalable capacity from 50 to 500bit/s/Hz/khz (including capacity for indoor

use), as shown inFigure3.As a comparison, the expected best performance of 3G is around 10 bit/s/Hz/km2

using High Speed Downlink Packet Access (HSDPA), Multiple-Input Multiple-Output (MIMO), etc. No

current technology is capable of such performance[iv].

Figure 3 Dimensioning Examples

2.2 Dimensioning objectives

Based on various traffic analyses, the Wireless World Initiative (WWI) has issued target air interface

performance figures. A consensus has been reached around peak rates of 100 Mbit/s in mobile situations and

1 Gbit/s in nomadic and pedestrian situations, at least as targets. So far, in a 10 MHz spectrum, a carrier rate

of 20 Mbit/s has been achieved when the user is moving at high speed, and 40 Mbit/s in nomadic use. These

values will double when MIMO is introduced. Clearly, the bitrate should be associated with an amount of

spectrum. For mobile use, a good target is a network performance of 5 bit/s/Hz, rising to 8 bit/s/Hz in

nomadic use.


Many technologies are competing on the road to 4G, as can be seen in Figure 4. Three paths are

possible, even if they are more or less specialized. The first is the 3G-centric path, in which Code Division

Multiple Access (CDMA) will be progressively pushed to the point at which terminal manufacturers will

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give up. When this point is reached, another technology will be needed to realize the required increases in

capacity and data rates.

The second path is the radio LAN one. Widespread deployment of WiFi is expected to start in 2005

for PCs, laptops and PDAs. In enterprises, voice may start to be carried by Voice over Wireless LAN

(VoWLAN). However, it is not clear what the next successful technology will be. Reaching a consensus on

a 200 Mbit/s (and more) technology will be a lengthy task, with too many proprietary solutions on offer.

A third path is IEEE 802.16e and 802.20, which are simpler than 3G for the equivalent performance.

A core network evolution towards a broadband Next Generation Network (NGN) will facilitate the

introduction of new access network technologies through standard access gateways, based on ETSI-

TISPAN, ITU-T, 3GPP, China Communication Standards Association (CCSA) and other standards. How

can an operator provide a large number of users with high session data rates using its existing infrastructure?

At least two technologies are needed. The first (called parent coverage) is dedicated to large coverage and

real-time services. Legacy technologies, such as 2G/3G and their evolutions will be complemented by WiFi

and WiMAX. A second set of technologies is needed to increase capacity, and can be designed without any

constraints on coverage continuity. This is known as pico-cell coverage. Only the use of both technologies

can achieve both targets (Figure 4). Handover between parent coverage and pico cell coverage is different

from a classical roaming process, but similar to classical handover. Parent coverage can also be used as a

back-up when service delivery in the pico cell becomes too difficult.

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Figure 4 Multiple Overlay Architecture[iv]

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Chapter 3 The User-centric system



3.1.2 Terminal Heterogeneity and Network Heterogeneity

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3The User-Centric System

In this section, I list and describe all the key features derived from the previous user scenarios. Inspired by

the Helioscentric Copernican theory[i], the user is located in the center of the system and the different key

features defining 4G rotate around him on orbits with a distance dependent on a user-sensitive scale.



In order to encourage people to move towards a new technology, which is a process that usually

takes a long time and a great deal of effort from the operators side, a combination of user friendliness and

user personalization appears to be the winning concept. User friendliness exemplifies and minimizes the

interaction between applications and users thanks to a well designed transparency that allows the users and

the terminals to naturally interact (e.g., the integration of new speech interfaces is a great step for achieving

this goal). For instance, consider a scenario A, where even before leaving home to reach the place of a work

appointment, users would like to receive information about train/subway schedules, door-to-door delays,

and so forth, as well as more personalized information, such as knowing how long it takes to walking to be

on schedule in order to eventually wait for the next train. According to the users decisions, their time-plan

must consequently be scheduled in the most efficient way. During their stay on the train, users would like to

download e-mails, listen to radio, watch TV, and so on. Finally, before they get off the last planned train, the

most time-saving exit and way to reach their final destination must be known and available in multimedia

format.

User personalization refers to the way users can configure the operational mode of their device and

preselect the content of the services chosen according to their preferences. Since every new technology is

designed keeping in mind the principal aim to penetrate the mass market and to have a strongly impact on

peoples lifestyles, the new concepts introduced by 4G are based on the assumption that each user wants tobe considered as a distinct, valued customer who demands special treatment for his or her exclusive needs.

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Therefore, in order to embrace a large spectrum of customers, user personalization must be provided with

high granularity, so that the huge amount of information is filtered according to the users choices. This can

be illustrated in scenario where users can receive targeted pop-up advertisements. The combination between

user personalization and user friendliness provides users with easy management of the overall features of

their devices and maximum exploitation of all the possible applications, thus conferring the right value to

their expense.

3.1.2 Terminal Heterogeneity and Network Heterogeneity

In order to be a step ahead of 3G, 4G must not only provide higher data rates but also a clear and

tangible advantage in peoples everyday life. Therefore, we believe that the success of 4G will consist of a

combination of terminal heterogeneity and network heterogeneity. Terminal heterogeneity refers to the

different types of terminals in terms of display size, energy consumption, portability/weight, complexity,

and so forth (Figure5). Network heterogeneity is related to the increasing heterogeneity of wireless

networks due to the proliferation in the number of access technologies available (e.g., UMTS, WiMAX, Wi-

Fi, Bluetooth). These heterogeneous wireless access networks typically differ in terms of coverage, data

rate, latency, and loss rate. Therefore, each of them is practically designed to support a different set of

specific services and devices. As explained below, 4G will encompass various types of terminals, which

may have to provide common services independently of their capabilities. Therefore, tailoring content for

end-user devices will be necessary in order to optimize the service presentation.

Furthermore, the capabilities of the terminal in use will determine whether or not new services are to

be provisioned, so as to offer the best enjoyment to the user and prevent declining interest and elimination of

a service offering. This concept is referred to asservice personalization. It implicitly constrains the number

of access technologies supportable by the users personal device. However, this limitation may be solved in

the following ways:

Figure 5 Heterogeneous Terminals

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3.1.2.1 By the development of devices with evolutionary design.

A naive example can clarify this concept: in the case where a user has a watch-phone on which he

would like to see a football match, simply by pressing a button on the watchs side, a self extracting monitor

with a larger display can emerge. Therefore, having the most adaptable device in terms of design can

provide customers with the most complete application package, thus maximizing the number of services

supported[i].

3.1.2.2 By mean of a personalization transfer.

An example can clarify this concept: in the case where the user has a watch-phone on which he

would like to see a video, he does not need to possess larger display terminals, as all the publicly available

terminals can be borrowed for the displaying time. Therefore, the advantage for the customers is to buy a

device on which they have the potential to get the right presentation for each service, freeing it from its

intrinsic restrictions. Furthermore, in a private environment, users can optimize the service presentation as

they wish, thus exploiting the multiple terminals they have at disposal.

The several levels of dependency highlighted by the user centric system definitely stress the fact

that it is not feasible to design 4G starting from the access technology in order to satisfy the users

requirements. A contextual and a strong preliminary consideration of the user are a more relevant and

appropriate approach to the design.

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Chapter4 The Real Technical Step-Up of 4G




4.4 Multimode/Reconfigurable and Interworking Devices

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4The Real Technical Step-Up of 4G


The real technical step-up of 4G with respect to 3G can be summarized with the word integration

seamless integration of already existing and new networks, services, and terminals, in order to satisfy ever-

increasing user demands.

Figure 6. Heterogeneous Networks

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Regardless of the actual technology, the forthcoming generation will be able to allow complete

interoperability among heterogeneous networks and associated technologies, thus providing clear

advantages in terms of:

4.2.1 Coverage.

In Fig. 5, the shift in paradigm is shown: while 2G was focused on full coverage for cellular systems

offering only one technology and 3G provides its services only in dedicated areas and introduces the

concept of vertical handover through the coupling with wireless local area network (WLAN) systems,4G

will be a convergence platform extended to all the network layers. Hence, the user will be connected almost

anywhere thanks to widespread coverage due to the exploitation of the various networks available. Inparticular, service provision will be granted with at least the same level of quality of service (QoS) when

passing from one networks support to that of another one.

4.2.2 Bandwidth.

Resource sharing among the various networks available will smooth the problem related to the

spectrum limitations relative to 3G.

4.2.3 Power consumption.

Battery drain is a chronic problem of wireless devices and battery technology is not progressing at an

appropriate pace. For example, 2G mobile phones were shipped out with one battery, whereas 3G ones are

shipped out with two batteries. Therefore, if we follow this 3G rule, power consumption will increase

proportionally to more advanced services.

For example, a cellular system that also supports short-range communications among the terminalscan achieve the goals outlined above. The rationale for introducing short-range communications is mainly

due to the need to support peer-to-peer (P2P) high-speed wireless links between mobile stations (MSs) and

to enhance the communication between an MS and the base station (BS) by fostering cooperative

communication protocols among spatially proximate devices. This communication enhancement primarily

refers to higher link reliability, larger coverage, higher spectral efficiency, and lower power consumption

due to the use of exclusive cooperative stations (e.g., relay stations (RSs) deployed by operators) or short-

range communications among different MSs. Indeed, the concept of cooperation introduces a new form of

diversity where terminals are less susceptible to channel variations and shadowing effects. This results in an

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improvement of the reliability of the communication and the extension of the coverage. Furthermore,

whereas in voice networks the resources are dedicated separately for each user, in cellular-controlled short-

range data networks it is possible to group users in clusters and gain the following advantages:

Only the cluster head (CH) needs to have a dedicated channel to the BS, while the other MSs can

communicate using unlicensed bands; thus, more bandwidth is not required. The CH selection is an

important issue that should take into account, among other factors, the channel conditions of the short-

range links (RS-MS and MS-MS) and the long-range ones (BS-MS), the available rate, the speed, the

location, the computational power, and the residual energy of the MSs.

Due to the short range of the transmissions performed by the MSs to the CH, it is possible to reduce

their power consumption and hence prolong their battery life.


Services are heterogeneous in nature (e.g., different types of services such as audio, video, pop-up

advertisements, etc.), quality, and accessibility. In fact, at a certain time and place, the quality of and the

accessibility to a service may not be the same due to the intrinsic heterogeneity of the network. For instance,

users in proximity to the shopping mall but outside the coverage of a WLAN can still receive pop-up

advertisements by exploiting a possible multihop ad hoc network in their surroundings. Therefore, thanks to

the dynamics of the network environment (in which the number of users, terminals, topology, etc. can

change), 4G maximizes the probability to provide users with the requested connectivity. Therefore, contrary

to the previous generations, the services provided in 4G will depend on the time, place, terminal, and user:

S2G ~ const, (3)

S3G ~ f (place), (4)

S4G ~ f(time, place, terminal, user), (5)

where the service provisioning depends on terminal and user because of terminal heterogeneity and service

personalization, and user personalization, respectively.

Apart from some soft additional emerging services (e.g., fast Internet connection, pop-up

advertisements, etc.), there is still a lack of really new and distinct services that will enable new applications

with tangible benefits for their users. Therefore, we envision that the real advantage in terms of services that

4G will bring will be based on the integration of technologies designed to match the needs of different

market segments:

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Short-range wireless technologies, such as Wi-Fi and Bluetooth, will enable machine-to-machine

(M2M) communications, where users sign up online on the waiting list, which sends them back the

approximate waiting time, where they can transfer content to a publicly available larger display. In

particular, from the sociological point of view, in the latter case the private and public spheres are

definitely mixed. This recombination can result in the enhancement of public access such that the access

to displays will be as common as the access to public telephone booths is nowadays. Short-range

wireless technologies also open the possibility to cooperative communication strategies, which can

provide better services at lower costs, thus maximizing the users profit. In this way, they increase the

social cooperative behavior and empower the consumer to make clever use of it. Hence, the users

personal device is no longer a mere medium for transferring information, but a social medium that helps

to build groups and friendships.

Since 3G networks are not able to deliver multicast services efficiently or at a decent level of quality, the

synergy of Universal Mobile Telecommunication System (UMTS) and digital audio/video broadcasting

(DAB/DVB) will open the possibility to provide to mobile users interactive or on demand services so

called TP data casting and audio and video streaming in a much more efficient way than using the

point-to-point switch network .

The embedding in the user terminal of a Global Positioning System (GPS) receiver will offer the

essential feature of location-awareness that is necessary to provide users with the most comprehensive

and extensive level of information, thus bringing about real revolution in terms of personalized services.

The user terminal can hence provide not only location based information, such as maps and directions to

follow to reach a specific place, but also useful information relevant in time and space, such as pop-up

advertisements concerning offers in shops nearby. However, GPS technology can only support outdoor

localization. Indoor localization, which is important in order to provide, for instance, the guided tour in a

museum, requires the cooperation of short-range wireless technologies.

Finally, it is worth highlighting that although users are attracted by high data rates, they would

certainly be even more attracted by useful services exploiting high data rates. The support of imaging and

video as well as high-quality audio gives service providers (SPs) a myriad of possibilities for developing

appealing applications. These features, blended with the support of high data rates, result in a particularly

attractive combination. Indeed, in addition to an explosive increase in data traffic, we can expect changes on

the typically assumed downlink-uplink traffic imbalance. Data transfer in the uplink direction is expected to

increase considerably and, as a result of these trends, the mobile user will ultimately become a content

provider (CP). In future wireless networks, the CP concept will broaden to encompass not only the

conventional small- or middle-size business-oriented service companies, but also any single or group ofusers. Mobile CPs will open up a new chapter in service provision.

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4.4 Multimode/Reconfigurable and Interworking Devices

As illustrated in Fig. 5, 4G is characterized by the support of heterogeneous terminals, ranging from pen-

phones to cars. However, due to its wide acceptance and usage in the past ten years, the mobile phone is

still expected to be on the next edge of the wave of the mass market. Indeed, while the penetration of

other devices will occupy a restricted niche role in the market (e.g., personal digital assistants (PDAs),

watch phones, and pen-phones will continue to be restricted to an elite group of tech-savvy people), the

mobile phone will still have no competitor in the near future, due to its size and weight, which guarantee

high portability. Moreover, due to the casual and informal feeling it gives, people will pay more attention to

the pop-up advertisements/news/events they receive on it than on any other device.

Looking at the latest releases of mobile phones, the actual tendency is to use a General Packet Radio

System (GPRS) platform and provide users with the most complete range of applications possible, trying to

continually include new additional features (e.g., digital camera recorder, etc.). On the other hand, the

emerging UIMTS phones essentially provide the possibility to support the mobile video communication.

However, the real enhancement that 3G brings to our everyday life is not really clear. This new application

cannot necessarily be considered as the killer application, as the quality of the video is low and it is

practically limited to a semi-static situation that implies a complete concentration of users during the

conversation (e.g., it is obviously not practical to watch a mobile phone while walking in the street),

restricting the field of action and raising secondary problems, such as safety issues (e.g., for the driver and

pedestrians while driving, etc.). Since 4G is based on the integration of heterogeneous systems, the future

trend of wireless devices will move toward:

4.4.1 Multimode/reconfigurable devices.

The user terminal is able to access the core network by choosing one of the several access networks

available and to initiate the handoff between them without the need for network modification or

interworking devices. This leads to the integration of different access technologies in the same device

(multimodality) or to the use of the software-defined radio (SDR) (reconfigurability) . For example,

whereas the integration of Bluetooth in the user terminal will enable a personalization-transfer service, a

built-in GPS receiver will allow users to utilize their personal devices as navigators just by plugging them in

their cars and thus even lighten the number of needed devices. However, the reconfigurability of the user

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terminal could be a key aspect that would make the future 4G technology as highly adaptable as possible to

the various worldwide markets.

4.4.2 Exploitation of Interworking devices.

In order to reduce the hardware embedded in the user terminal and the software complexity, the use

of interworking devices is exploited. For example, this is the case of an integrated access point (AP)

performing the interworking between a wireless metropolitan area network (WMAN) technology and a

WLAN technology, such as WiMAX and Wi-Fi, respectively: the WMAN is considered as the backbone and

the WLAN as the distribution network; therefore, instead of integrating both technologies, the user terminal

will only incorporate the Wi-Fi card. The price to be paid for this relief is hence an increased system

(infrastructure) complexity.

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Chapter5 Key 4G Technologies

5.1 OFDMA

5.2 Software-defined Ratio

5.3 Multiple input Multiple output

5.4 Caching and Pico cells

5.5 Coverage

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5.2 Software defined radio

Software Defined Radio (SDR) benefits from todays 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.

5.3 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.

5.4 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. This method 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 bitrate is a maximum. Between these areas, the coverage is not used

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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 to

500 bit/s/Hz), high capacity and lower cost.

5.5 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.

Figure 8 Pico cell network design[iv]

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Finally the pico cell coverage is made continuous either by using MIMO or by deploying another

pico cell coverage in a different frequency band (see Figure 9). Parent coverage performance may vary from

1 to 20 bit/s/Hz/km, while pico cell technology can achieve from 100 to 500 bit/s/Hz/km, depending on the

complexity of the terminal hardware and software.

These performances only refer to outdoor coverage; not all the issues associated with indoor

coverage have yet been resolved. However, indoor coverage can be obtained by:

Direct penetration; this is only possible in low frequency bands (significantly below 1 GHz) and

requires an excess of power, which may raise significant interference issues.

Indoor short range radio connected to the fixed network. Connection via a relay to a pico cellular

access point.

Figure 9 Example of deployment in dense traffic areas

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6Conclusion

The 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.

Many other features, such as robust transmission and cross-layer optimization, will contribute to

optimizing the performance, which can reach between 100 and 500 bit/s/Hz/km2. The distributed, full IP

architecture can be deployed using two main products: base stations and the associated controllers.

Terminal complexity depends on the number of technologies they can work with. The minimum number of

technologies is two: one for the radio coverage and one for short range use (e.g. PANs).

However, the presence of legacy networks will increase this to six or seven.

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7Appendices

7.1 References : Journals and Magazines

i. Simone Frattasi, Hanane Fathi, Frank H.P Fitzek, and Ramjee Prasad, Aalborg University, Marcos

D. Katz, Samsung Electronics, Defining 4G Technology from the Users Perspective,published by

IEEE Jan/Feb 2006

ii. Third/fourth generation wireless networks, proceeds of the IEEE conference 2001

iii. K.R.Santhi, G. Senthil Kumaran, Migration to 4 G: Mobile IP based Solutions,

published by IEEE 2006

iv. D. Rouffet, S. Kerboeuf, L. Cai, V. Capdevielle, 4G Mobile, technical paper published by Alcatel.

v. Linda Doyle, Beyond 3G: 4G Based Mobile Networks

7.2 References : Websites

vi. www.wikipedia.org

vii. www.alcatel.com

viii. www.ieee.org

ix. www.eurotechnology.com

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7.3 List of Figures and Tables used

Fig.1 Evolution from 2G to 4G 10

Fig.2 Service Evolution Vision 14

Fig.3 Dimensioning Examples 14

Fig.4 Multiple Overlay Architecture 16

Fig.5 Heterogeneous Terminals 20

Fig.6 Heterogeneous Networks 23

Fig.7 OFDM Principles 31

Fig.8 Pico cell network Design 34

Fig.9 Example of deployment in dense traffic areas 35

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7.4 Glossary

Access Point(AP): An access point is a station that transmits and receives data (sometimes referred to as a

transceiver). An access point connects users to other users within the network and also can serve as the point

of interconnection between the WLAN and a fixed wire network.

Bandwidth: Bandwidth is the width of the range (or band) of frequencies that an electronic signal uses on a

given transmission medium.

Broadband: Broadband refers to telecommunication in which a wide band of frequencies is available to

transmit information.

CDMA: CDMA is a form of multiplexing, which allows numerous signals to occupy a single transmission

channel, optimizing the use of available bandwidth. The technology is used in ultra-high-frequency (UHF)

cellular telephone systems in the 800-MHz and 1.9-GHz bands.

Fourth Generation Mobile Systems: 4G is the short term for fourth-generation wireless, the stage of

broadband mobile communications that will supersede the third generation (3G). While neither standards

bodies nor carriers have concretely defined or agreed upon what exactly 4G will be, it is expected that end-

to-end IP and high-quality streaming video will be among 4G's distinguishing features.

GSM: GSM digitizes and compresses data, then sends it down a channel with two other streams of user

data, each in its own time slot.

IP: The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another

on the Internet.

MIMO: MIMO (multiple input, multiple output) is an antenna technology for wireless communications inwhich multiple antennas are used at both the source (transmitter) and the destination (receiver).

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OFDM: Orthogonal frequency-division multiplexing (OFDM) is a method of digital modulation in which a

signal is split into several narrowband channels at different frequencies.

Pico Cell: Very small cell in a mobile network for boosting capacity within buildings.

UMTS: UMTS (Universal Mobile Telecommunications Service) is a third-generation (3G) broadband,

packet-based transmission of text, digitized voice, video, and multimedia at data rates up to 2 megabits per

second (Mbps).

WiMAX: WiMAX (Worldwide Interoperability for Microwave Access) is a wireless industry coalition

whose members organized to advance IEEE 802.16 standards for broadband wireless access ( BWA )

networks.

4G Wirless System

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