web viewhsupa will initially boost the umts/wcdma uplink up to 1.4mbpsand in later releases up to...

7

COMMUNICATION AND INFORMATION AGENCY OF UZBEKISTAN TASHKENT UNIVERSITY OF INFORMATION TECHNOLOGIES

Admin to protection

Head of department

Amirsaidov U.B.

_____________

___________2012 y.

FINAL QUALIFICATION WORK OF BACHELOR

On the theme: “Comparative analyses of LTE and WiMAX technologies”

Graduating student _______ Klichkhanov R.A.

(signature)

Teacher _______ Abdurakhmanov R.P.

(signature)

Reviewer _______

(signature)

Adviser on LS _______ Aliyev.U.T

(signature)

Tashkent 2012

8

COMMUNICATION AND INFORMATION AGENCY OF UZBEKISTAN TASHKENT UNIVERSITY OF INFORMATION TECHNOLOGIES

Faculty Telecommunication Department________________________

Specialization Telecommunication

AFFIRMING

Head of Department

«__»_______2012y

TASK

On final qualification work of student Klichkhanov Rakhmatilla Abdullayevich

(Full name)

Theme of the work : “Comparative analyses of LTE and WiMAX technologies”

1. Confirmed by order of the University from «__»_______2012y. №___2. Term of delivery of the finished work______________________________3. Initial data to work : materials of pregraduation practice________________4. The maintenance of a settlement-explanatory note (the list of questions

subject to working out): 1) EVOLUTION OF WIRELESS COMMUNICATION TECHNOLOGIES , 2) COMPARATIVE ANALYSES OF LTE AND WIMAX TECHNOLOGIES, 3) SIMULATION OF LTE UPLINK IN COMPARISON WITH AN OFDM SYSTEM _________________________________________________

5. The list of a graphic material: Demonstration slides__________________6. Date of delivery of the task____________________________________

9

Teacher ____________ (signature)

Task accepted ___________ (signature)

7. Advisers for separate sections of final work

Name of the Chapter

Adviser

signature, date

Given mission

Received mission

1. Main chapters

2. LS

Abdurakhmanov R.P.

Aliyev U.T

8. Progress chart

№Name of the Chapter Due date

Signature of the adviser

1 EVOLUTION OF WIRELESS COMMUNICATION TECHNOLOGIES

2 COMPARATIVE ANALYSES OF LTE AND WIMAX TECHNOLOGIES

3 SIMULATION OF LTE UPLINK IN COMPARISON WITH AN OFDM SYSTEM

10

4 SAFETY VITAL ACTIVITY AND SAFETY ENGINEERING

Graduating student _______ Klichkhanov R.A. «__»______ 2012y.

(signature)

The head of FQW ________ Abdurakhmanov R.P. «__»________2012y. (signature)

11

INTRODUCTION

Over the last few years, there has been increasing demands for accessing the

Internet over the mobile devices. To address this, the wireless telecommunication

industry has been striving hard to define a new air interface for mobile

communications to provide a framework for high mobility broadband services and

increase the overall system capacity; reducing latency; and improving spectral

efficiency and cell-edge performance.

The communication industry has been formulating new standards to

efficiently deliver high speed broadband mobile access in a single air interface and

network architecture at low cost to operators and end users. Two technologies, the

IEEE 802.16 WiMAX (World wide Interoperability for Microwave Access) and

the 3GPP LTE (Third Generation Partnership Project Long Term Evolution) aim to

provide mobile voice, video and data services by promoting low cost deployment

and service models through Internet friendly architectures and protocols. Both

these technologies are being considered as candidates for the fourth generation

(4G) of mobile networks.

Worldwide Interoperability for Microwave Access (WiMAX) technology,

also known as the IEEE 802.16 standard, is based on WMAN (Wireless

Metropolitan Area Network). It provides data rates up to 75 Mbps over the

distance of 50 km. WiMAX uses frequency bands of 10-66 GHz, covering long

geographical areas using licensed or unlicensed spectrum.

Long term evolution (LTE) is the next step forward in cellular 3G services.

LTE technology is a based on a 3GPPstandard that provides for a downlink

speedof up to 100 megabits per second (Mbps) and an uplink speed of up to

50Mbps.Fixed wireless and wired standards are already approaching or achieving

100 Mbps or faster, and LTE is a way for cellular communications to operate at

that high data rate.

The objective of this final qualifying work is to conduct a brief comparison

between WiMAX and 3GPP LTE. The comparison is performed by discussing the

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system architectures, radio interface protocol architectures and some key features

of WiMAX and LTE. Also this work includes the link level simulation of LTE

uplink in comparison with an OFDM system. In addition to this, the capacity of

MIMO system is in comparison with a SISO system also discussed.

13

1. EVOLUTION OF WIRELESS COMMUNICATION

TECHNOLOGIES

1.1 Evolution of mobile technologies

Mobile wireless industry has started its technology creation, revolution and

evolution since early1970s. In the past few decades, mobile wireless technologies

have experience 4 generations of technology revolution and evolution, namely

from 1G to 4G. The cellular concept was introduced in the 1G technology which

made the large scale mobile wireless communication possible. Digital

communication has replaced the analogy technology in the 2G which significantly

improved the wireless communication quality. Data communication, in addition to

the voice communication, has been the main focus in the 3Gtechnologies and a

converged network for both voice and data communication is emerging. With

continued research and development, there are many killer application

opportunities for the 4G as well as technological challenges.

Mobile communications roadmap showing the convergence of various technologies towards 4G

14

Figure-1.1 Evolution Path of Mobile Technologies towards 4G

The first generation

1G stands for "first generation," refers to the first generation of wireless

telecommunication technology, more known as cell phones.

Its successor, 2G, which made use of digital signals, 1G wireless networks

used analog radio signals. Through 1G, a voice call gets modulated to a higher

frequency of about 150MHz and up as it is transmitted between radio towers. This

is done using a technique called Frequency-Division Multiple Access (FDMA).In

terms of overall connection quality, 1G compares unfavorably to its successors. It

has low capacity, unreliable handoff, poor voice links, and no security at all since

voice calls were played back in radio towers, making these calls susceptible to

unwanted eavesdropping by third parties [2].

However, 1G did maintain a few advantages over2G. In comparison to 1G's

analog signals, 2G'sdigital signals are very reliant on location and proximity. If a

2G handset made a call far away from a cell tower, the digital signal may not be

strong enough to reach it. While a call made from a1G handset had generally

poorer quality than that of a 2G handset, it survived longer distances. This is due to

the analog signal having a smooth curve compared to the digital signal, which had

a jagged, angular curve. As conditions worsen, the quality of a call made from a

1G handset would gradually worsen, but a call made from a 2G handset would fail

completely.

Different 1G standards were used in various countries. One such standard is

NMT (Nordic Mobile Telephone), used in Nordic countries, Eastern Europe and

Russia. Others include AMPS(Advanced Mobile Phone System) used in the United

States, TACS (Total Access Communications System) in the United Kingdom,C-

Netz in West Germany, Radiocom 2000 in France, and RTMI in Italy.

The second generation

2G is short for second-generation wireless telephone technology. It cannot

normally transfer data, such as email or software, other than the digital voice call

15

itself, and other basic ancillary data such as time and date. Nevertheless, SMS

messaging is also available as a form of data transmission for some standards.

Second generation2G cellular telecom networks were commercially launched on

the GSM standard in Finland by Radiolinja (now part of Elisa Oyj) in 1991. GSM

service is used by over 2 billion people across more than 212 countries and

territories. The ubiquity of the GSM standard makes international roaming very

common between mobile phone operators, enabling subscribers to use their phones

in many parts of the world.

2G technologies can be divided into Time Division Multiple Access

(TDMA) based and Code Division Multiple Access (CDMA) based standards

depending on the type of multiplexing used. 2G makes use of a CODEC

(Compression-Decompression Algorithm) to compress and multiplex digital voice

data. Through this technology, a 2G network can pack more calls per amount of

bandwidth as a 1G network. 2Gcellphone units were generally smaller than

1Gunits, since they emitted less radio power.

Some benefits of 2G were Digital signals require consume less battery

power, so it helps mobile batteries to last long. Digital coding improves the voice

clarity and reduces noise in the line. Digital signals are considered environment

friendly. The use of digital data service assists mobile network operators to

introduce short message service over the cellular phones. Digital encryption has

provided secrecy and safety to the data and voice calls. The use of 2G technology

requires strong digital signals to help mobile phones work. If there is no network

coverage in any specific area, digital signals would be weak.

2.5G – GPRS (General Packet Radio Service)

2.5G, which stands for "second and a half generation," is a cellular wireless

technology developed in between its predecessor, 2G, and its successor, 3G. The

term "second and a half generation" is used to describe 2G-systems that have

implemented a packet switched domain in addition to the circuit switched domain.

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"2.5G" is an informal term, invented solely for marketing purposes, unlike "2G" or

"3G" which are officially defined standards based on those defined by the

International Telecommunication (ITU).GPRS could provide data rates from 56

kbit/s up to115 kbit/s. It can be used for services such as Wireless Application

Protocol (WAP) access, Multimedia Messaging Service (MMS), and for Internet

communication services such as email and World Wide Web access. GPRS data

transfer is typically charged per megabyte of traffic transferred, while data

communication via traditional circuit switching is billed per minute of connection

time, independent of whether the user actually is utilizing the capacity or is in an

idle state [2].

2.5G networks may support services such as WAP, MMS, SMS mobile

games, and search and directory.

2.75 – EDGE (Enhanced Data rates for GSM Evolution)

EDGE (EGPRS) is an abbreviation for Enhanced Data rates for GSM

Evolution, is a digital mobile phone technology which acts as a bolt-on

enhancement to 2G and 2.5G General Packet Radio Service (GPRS) networks.

This technology works in GSM networks. EDGE is a superset to GPRS and can

function on any network with GPRS deployed on it, provided the carrier

implements the necessary upgrades.

EDGE technology is an extended version of GSM. It allows the clear and

fast transmission of data and information. It is also termed as IMT-SC or single

carrier. EDGE technology was invented and introduced by Cingular, which is now

known as AT& T. EDGE is radio technology and is a part of third generation

technologies. EDGE technology is preferred over GSM due to its flexibility to

carry packet switch data and circuit switch data.

The use of EDGE technology has augmented the use of black berry, N97

and N95 mobile phones. EDGE transfers data in fewer seconds if we compare it

with GPRS Technology. For example atypical text file of 40KB is transferred in

only 2seconds as compared to the transfer from GPRS technology, which is 6

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seconds. The biggest advantage of using EDGE technology is one does not need to

install any additional hardware and software in order to make use of EDGE

Technology. There are no additional charges for exploiting this technology. If a

person is an exGPRS Technology user he can utilize this technology without

paying any additional charges.

The third generation

3G is the third generation of mobile phone standards and technology,

superseding 2G, and preceding 4G. It is based on the International

Telecommunication Union (ITU) family of standards under the International

Mobile Telecommunications programme, IMT-2000.

3G technologies enable network operators to offer users a wider range of

more advanced services while achieving greater network capacity through him

proved spectral efficiency. Services include wide area wireless voice telephony,

video calls, and broadband wireless data, all in a mobile environment. Additional

features also include HSPA data transmission capabilities able to deliver speeds up

to 14.4Mbit/s on the downlink and5.8Mbit/s on the uplink. Spectral efficiency or

spectrum efficiency refers to the amount of information that can be transmitted

over a given bandwidth in a specific digital communication system. ... High-Speed

Packet Access (HSPA) is a collection of mobile telephony protocols that extend

and improve the performance of existing UMTS protocols.

Unlike IEEE 802.11 (common names Wi-Fi or WLAN) networks, 3G

networks are wide area cellular telephone networks which evolved to incorporate

high-speed internet access and video telephony. IEEE 802.11 networks are short

range, high-bandwidth networks primarily developed for data. Wi-Fi is the

common name for a popular wireless technology used in home networks, mobile

phones, video games and more. The notebook is connected to the wireless access

point using a PC card wireless card. A videophone is a telephone which is capable

of both audio and video duplex transmission.

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3G technologies make use of TDMA and CDMA.3G (Third Generation

Technology) technologies make use of value added services like mobile television,

GPS (global positioning system) and video conferencing. The basic feature of

3GTechnology is fast data transfer rates.

3G technology is much flexible, because it is able to support the 5 major

radio technologies. These radio technologies operate under CDMA, TDMA and

FDMA.CDMA holds for IMT-DS (direct spread), IMT-MC (multi carrier). TDMA

accounts for IMT TC (time code), IMT-SC (single carrier). FDMA has only one

radio interface known as IMT-FC or frequency code. Third generation technology

is really afford able due to the agreement of industry. This agreement took pace in

order to increase itsadoption by the users. 3G system is compatible to work with

the 2G technologies. The aim of the 3G is to allow for more coverage and growth

with minimum investment.

There are many 3G technologies as W-CDMA,GSM EDGE, UMTS, DECT,

WiMax and CDMA2000.Enhanced data rates for GSM evolution or EDGE is

termed to as a backward digital technology, because it can operate with

olderdevices.3G has the following enhancements over 2.5G and previous

networks:

- Enhanced audio and video streaming;

- Several Times higher data speed;

- Video-conferencing support;

- Web and WAP browsing at higher speeds;

- IPTV (TV through the Internet) support.

3.5G – HSDPA (High-Speed Downlink Packet Access)

High-Speed Downlink Packet Access(HSDPA) is a mobile telephony

protocol, also called 3.5G (or"3½G"), which provides a smooth evolutionary path

for UMTS-based 3G networks allowing for higher data transfer speeds.

HSDPA is a packet-based data service in W-CDMA downlink with data

transmission up to 8-10 Mbit/s (and 20 Mbit/s for MIMO systems) over a

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5MHzbandwidth in WCDMA downlink. HSDPA implementations includes

Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output

(MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced

receiver design.

3.75G – HSUPA (High-Speed Uplink Packet Access)

The 3.75G refer to the technologies beyond the well defined 3G

wireless/mobile technologies. High Speed Uplink Packet Access (HSUPA) is a

UMTS/WCDMA uplink evolution technology. The HSUPA mobile

telecommunications technology is directly related to HSDPA and the two are

complimentary to one another.

HSUPA will enhance advanced person-to-person data applications with

higher and symmetric data rates, like mobile e-mail and real-time person-to person

gaming. Traditional business applications along with many consumer applications

will benefit from enhanced uplink speed. HSUPA will initially boost the

UMTS/WCDMA uplink up to 1.4Mbpsand in later releases up to 5.8Mbps.

The fourth generation

4G refers to the fourth generation of cellular wireless standards. It is a

successor to 3G and 2Gfamilies of standards. The nomenclature of the generations

generally refers to a change in the fundamental nature of the service, non-

backwards compatible transmission technology and new frequency bands. The first

was the move from 1981analogue (1G) to digital (2G) transmission in 1992.This

was followed, in 2002, by 3G multi-media support, spread spectrum transmission

and at least200 kbit/s, soon expected to be followed by 4G,which refers to all-IP

packet-switched networks, mobile ultra-broadband (gigabit speed) access and

multi-carrier transmission. Pre-4G technologies such as mobile WiMAX and first-

release 3G Long Term Evolution (LTE) have been available on the market since

2006and 2009 respectively. It is basically the extension in the 3G technology with

more bandwidth and services offers in the 3G.

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The expectation for the 4G technology is basically the high quality

audio/video streaming over end to end Internet Protocol. If the Internet Protocol

(IP)multimedia sub-system movement achieves what it going to do, nothing of this

possibly will matter. WiMAX or mobile structural design will become

progressively more translucent, and therefore the acceptance of several

architectures by a particular network operator ever more common. Some of the

companies trying 4G communication at100 Mbps for mobile users and up to 1

Gbps over fixed stations. They planned on publicly launch in their first commercial

wireless network around 2010. As far as other competitor’s mobile communication

companies working on 4Gtechnology even more quickly. Sprint Nextel was

planned to launch WiMAX over 4 G broadband mobile networks in United States.

Some of the other developed countries like United Kingdom stated a plan to sale

via auction of 4G wireless frequencies couple of years back. The word “MAGIC”

also refers to 4G wireless technology which stands for Mobile multimedia, Any-

where, Global mobility solutions over, integrated wireless and Customized

services.

1.2 Wireless access network communication standards

The different approaches exist in theories wireless technology to their

categorizations.

Particular, following approaches are used:

Categorization of wireless technology by coverage area:

- WPAN — Wireless Personal Area Networks.

The Examples technology - Bluetooth.

- WLAN — Wireless Local Area Networks.

The Examples technology - Wi-Fi.

- WMAN — Wireless Metropolitan Area Networks.

The Examples technology –WiMAX

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Figure-1.2 Categorization of wireless technology by coverage area

Bluetooth

Bluetooth is an open specification technology for short range wireless data

and voice communication, available anywhere in the world. Bluetooth operates on

the 2.4 GHz band, a globally unlicensed band, allowing the anywhere to come into

effect. Open specification is from the Bluetooth Special Interest Group (SIG). SIG

produced a specification for Bluetooth which is royalty free and publicly available.

It is an effective radio transmission communication standard effective for

transmission of data and voice for distances under thirty feet.

Bluetooth supports both data and voice transmission, making it an effective

technology in today’s fast and ever-changing telecommunication world.

As mentioned already, Bluetooth operates on the 2.4 GHz ISM band. The

frequency spectrum is divided into 79 channels. When Bluetooth was originally

released in 2000, France and Spain only utilized the first 23channels. Later that

year, Japan became the first country to utilize all 79 channels. The bandwidth is

limited to 1 MHz per channel and spread spectrum (CDMA) communication

standards need to be employed (Miller, Bisdikian, 2002).

Bluetooth is an effective standard that can be utilized in the consumer

market, but it is most often utilized for direct network access onto LANs, which

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ispopular in the enterprise sector. For this direct access to work, the network must

employ Access Points. The connection to these wireless data access points is

virtually the same as that of any IEEE 802.11 wireless connection. This data

Access Point simply provides a “connection” to the network.

ZigBee

ZigBee technology uses 868 MHz (Europe – 20kb/s), 915 MHz (US

–40kb/s) and2.4 GHz (worldwide – 250kb/s) ISM bands, enabling regional or

global deployment, to provide low data rate wireless applications and offers a

published specification set of high level communication protocols designed to use

small, low-power digital radios based on the IEEE 802.15.4 standard. The 802.15.4

technology defines PHY and MAC layers allowing for near instantaneous

communication between devices without the need for network synchronization

delays. These capabilities facilitate to have thousands of devices on a single

wireless network. Zigbee is promoted by the Zigbee Alliance and is defined to

provide low cost, low power and reliable control and monitoring applications

within the private home and industrial environment, such as consumer electronics

control, lighting control, access control, HVAC, patient monitoring, security,

peripherals management and asset management [5].

IEEE 802.11

The IEEE 802.11 specification is an international standard describing the

characteristics of a Wireless Local Area Network (WLAN). The name is Wi-Fi

(Wireless Fidelity). Over the last several years, the explosion of Wi-Fi devices

made possible the discovery of the wireless network world. These standards are

sometimes associated with directional antennas to establish point-to-point

connections.

The first 802.11 wireless network standards were developed in 1997 as an

extension to the Local Area Network. It was known as wireless up to 2 Mbps. The

IEEE 802.11 standard can comprised of more than 20 different standards, each of

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which is denoted by a letter appended to the end of the name. The most familiar

standards are 802.11b and 802.11g which are used in the commercial Wi-Fi

devices [3, 4]. Both of these standards can operate 2.4 GHz band, and that only

major difference between two in the transfer rate, as seen in Table 1.1.

The IEEE 802.11b was a refined standard for the ordinal 802.11 and was

successful due to its high data rates of 11 Mbps- range of 100m to a maximum of a

few hundred meters, operates on 2.4GHz unlicensed band. 802.11b is most widely

deployed wireless network within the 802.11 wireless families [3, 4].

The IEEE 802.11a is a standard 5 GHz band with maximum data rate of

54Mbps. The major disadvantage in deploying 802.11a with the other 80211

standards (b and g) is that, they cannot co-exist, as they operate on different

frequency bands. 802.11b/g operates on the 2.4GHz spectrum. There are some

wireless cards and access points which are compatible to all the three standards

thereby supporting the 2.4GHz and 5GHz frequencies [3, 4].

Table 1.1: The IEEE 802.11 Family Standards

Standards 802.11b 802.11a 802.11gYear of

standardized1999 1999 2003

Frequency 2.4 GHz 5 GHz 2.4 GHzSpeeds 11 Mbps 54 Mbps 54 Mbps

IndoorRange 30-50 Meters 30-50 Meters 30-50 MetersAdvantages Interoperablewith

802.11g inexpensive

Reduced Wi-Fi interference more Non-Overlapping

Channels

Interoperable with 802.11b High

Speed Wireless Data

CommunicationData Transfer

Range Typical(MAX)

6.5(11)Mbps 25(54)Mbps 25(54)Mbps

The IEEE 802.11g wireless standard also operates on the 2.4 GHz band and

has similar range and characteristics as the 802.11b. it has a data rate of 54 Mbps.

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The 802.11g has backward compatibility with 802.11b and differs only on the

modulation technique.

IEEE 802.16 Standards

Telecommunication equipment manufacturers started introducing products

for Broadband Wireless Access (BWA) at the end of the 90’s. But they were still

looking for interoperable standard. The National Wireless Electronics Systems

Testbed (N-WEST) called a meeting in 1998, about the need of an interoperable

standard which resulted in the IEEE 802 standard. A lot of efforts were made in

this regard which resulted later in the formation of IEEE 802.16 standard. Initially,

the main focus of this group was to develop the radio interface for BWA which

used the radio spectrum from the 10-66 GHz range. It also supports the LOS based

Point to Multipoint (PMP) broadband wireless system.

IEEE 802.16-2001

The standard was developed in December 2001. It uses the spectrum range

of 10-66 GHz to provide fixed broadband wireless connectivity and single carrier

modulation techniques such as 16-QAM, 64-QAM and QPSK in physical layer and

Time division Multiplexed (TDM) techniques in MAC layer. The standard

includes Differential QoS techniques for the improvement of LOS based

conditions. The standard uses Time Division Duplex (TDD) and Frequency

Division Duplex (FDD) as duplexing techniques.

IEEE 802.16a-2003

The standard amended the basic IEEE 802.16 by using a frequency range of

2-11 GHz which includes both licensed and license free frequency bands. Due to

inclusion of the low frequencies, below 11 GHz, NLOS communication is

possible. The NLOS operations introduced the multipath propagation effects which

have been overcome through the adaptation of multicarrier modulation techniques

25

in the physical layer. OFDM was chosen as modulation technique. The standard

improved also security issues by making the features of privacy layer mandatory.

IEEE 802.16c

The standard developed the profile details of 10-66 GHz frequency band and

corrected the inconsistencies involved in the previous standard.

IEEE 802.16d-2004

Is the amendment of IEEE 802.16a. It was initially considered as the

revision of IEEE 802.16 standard and was named IEEE 802.16 REVd. But in

September 2004, due to the credibility of the amendments, it was named

IEEE.802.16d. The standard was designed for fixed, nomadic and portable users so

as to provide fixed BWA. It supports both TDD and FDD transmission modes. The

most important feature of this standard is the provision of support for advance

antenna systems and adaptive modulation and coding techniques.

IEEE 802.16e-2005

Is the amendment of IEEE 802.16d-2004 and provides support for mobility

of subscribers, who can move at vehicular speeds and provides services such as

high speed handoffs due to its technological advances. It enhances the overall

system performance due to support of Adaptive Antenna Systems (AAS) and

MIMO. It facilitates mobile, fixed and portable users. The standard updated the

security feature included privacy sub-layer.

1.3 Conclusion for current chapter

In this chapter, we have surveyed four wireless technologies namely 1G, 2G,

3G,4G and wireless access network standards . We conclude that the 4G

technologies will stimulate subscriber interest in broadband wireless applications

because of its ability and flexibility towards the world of wireless communications.

26

A concentrated effort seems to categorize how wireless mobile technologies can

accompaniment a more user focused world of wireless. Finally the report

elaborates the different wireless Communication Technologies that have been

developed in the past and their evolution and development towards 4th generation

such as3G Long Term Evolution (LTE) and first-release mobile WiMAX

communication systems. So we detailed study this two technologies in next chapter.

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2. COMPARATIVE ANALYSES OF LTE AND WIMAX

TECHNOLOGIES

2.1 Introduction

In recent years, communication industry have been keen to develop and

formulate new standards in order to provide high speed broadband mobile access

in a single air interface and network architecture for reasonable cost for end-users

and mobile operators. WiMAX and LTE are two leading standards as the results of

above efforts.

WiMAX belongs to the IEEE family of standards and refers to IEEE 802.16

standard. It enhances the WLAN (IEEE 802.11) by extending the wireless access

to Wide Area Network (WAN) and Metropolitan Area Network (MAN). It uses

OFDMA as physical layer radio access technology in the downlink and uplink.

The initial versions of WiMAX, IEEE 802.16-2004 (fixed WiMAX) supports fixed

and nomadic access, while IEEE 802.16-2005 (mobile WiMAX) supports

enhanced QoS and mobility up to 120 km/h. Mobile WiMAX uses IP based

services to provide downlink peak data rates up to 75 Mbps depending on the

modulation technique and antenna configuration used. WiMAX supports LOS and

NLOS propagations across 10 GHz to 66 GHz and 2 GHz to 11 GHz respectively.

LTE is the part of 3GPP and evolved from the evolution of UMTS/HSPA

cellular technology to meet current user demands of high data rates and spectral

efficiencies. LTE specifications are jointly based on E-UTRA and E-UTRAN. The

version specification for LTE is released in 3GPP Release 8. LTE uses OFDMA

radio access technology in downlink and SC-FDMA in the uplink. The use of SC-

FDMA in the uplink reduces PAPR as compared to OFDMA. The downlink peak

data rates range from 100 Mbps to 326.4 Mbps depending on the modulation

technique and antenna configuration used. LTE aims at providing data rates, IP

backbone services, flexible spectrum, lower power consumptions and simple

network architecture with open interfaces.

28

In this chapter we do a comparative study of WiMAX and LTE in context of

system architecture, air interfaces radio and protocol aspects (including multiple

access techniques, access modes and modulation. Further, we provide a

comparative summary that concludes this chapter.

2.2 System Architecture

The LTE and WiMAX System Architecture aims to improve latency,

capacity, and throughput while simplifying the core network and optimizing the IP

traffic and services. Both the architectures ensure seamless integration into the

existing 3GPP cellular wireless networks and provide simplified support and

handover to 3GPP and non-3GPP access technologies.

The LTE Architecture

LTE supports packet data services unlike previous cellular systems that

support circuit switched data model. In addition, LTE provides seamless IP

connectivity between Packet Data Network (PDN) and UE. LTE architecture is

comprised of Core Network (CN) and Access Network (AN), where CN

corresponds to the Evolved Packet Core (EPC) which comes from System

Architecture Evolution (SAE). The AN refers to E-UTRAN. The CN and AN

together correspond to Evolved Packet System (EPS). EPS connects the users to

PDN by IP address in order to access the internet and services like Voice over IP

(VoIP). Typically, the EPS bearer is associated with QoS. Multiple bearers can be

established for a user to provide connectivity to different PDNs or QoS streams.

The overall network architecture including various EPS elements is shown in

Figure 2.1[16].

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Figure 2.1 : Evolved Packet System (EPS) Network Elements

EPS elements are inter-linked with standard interfaces which allow the

operators to source the network elements from various vendors.

Core Network

Core network is known as EPC in SAE. The key responsibilities of CN

include bearer establishment and control of UE. EPC is made of various logical

nodes.

- Mobility Management Entity (MME).

- Packet Data Network Gateway (P-GW).

- Serving Gateway (S-GW).

- Policy Control and Charging Rules Function (PCRF).

- Home Subscriber Server (HSS).

Mobility Management Entity

It is the control node used to process signaling information between CN and

UE. The protocols running between CN and UE are called Non Access Stratum

(NAS) protocols. The key functions of MME are:

- Bearer Management Functions: Handled by the session management

layer in the NAS protocol and used to establish, maintain and release bearers.

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-Connection Management Functions: Handled by the mobility

management or the connection management layer in the NAS protocol. They are

used to manage security and connection establishment between UE and network.

Packet Data Network Gateway

Used to allocate the IP address for UE as well as flow based charging and

QoS enforcement. It filters the downlink user IP packets into the bearers typically

based on QoS. This is based on traffic flow templates. In addition, P-GW acts as

mobility anchor to work with Non-3GPP technologies i.e. WiMAX and

CDMA2000.

Serving Gateway

S-GW is responsible for transferring user IP packets. It stores local mobility

information for data bearers when UE runs between various eNodeBs. S-GW acts

as mobility anchor to work with 3GPP technologies (UMTS, GPRS etc). In

addition, it collects information about legal interception and charging, i.e. the

volume of data sent to or received from the user is called charging.

Policy Control and Charging Rules Functions

PCRF controls flow based charging functions which are part of Policy

Control Enforcement Function (PCEF) as well as it organize decision making

control policy. PCRF is part of P-GW. The key responsibility of PCRF is to

provide QoS authorization i.e. bit rate and QoS class identifier. QoS authorization

decides the method of treating certain data flows in the PCEF and ensures that the

data flow is in accordance with the subscription of the user profile.

Home Subscriber Server (HSS):

HSS is also called Home Location Register (HLR). It contains the SAE

subscription data of users such as roaming restrictions and EPS subscribed QoS

profiles. HSS contains the information of PDN in the form of access point or PDN

31

address. In addition, HSS contains dynamic information i.e. identity of the MME

to which an user is connected currently. The vectors for security keys and

authentication are generated as the result of AuC (Authentication centre)

integration.

Access Network

The Access Network (EUTRAN) is comprised of network of eNodeBs

connected to each other through interfaces called X2. The Architecture of

E-UTRAN is flat due to the absence of a centralized controller in the case of

normal traffic (as opposed to broadcast). The eNodeB is connected to EPC via S1

interface and to MME through S1-MME interface. The eNodeB and S-GW are

interlinked by means of S1-U interface. The S1-U interface carries user data

between serving GW and eNodeB. The protocols which run between eNodeB and

UE are known as Access Stratum (AS) Protocols.

TheArchitectureofAccessNetworkisshowninFigure 2.2[17].

Figure 2.2: Architecture of LTE Access Network (E-UTRAN)

32

The key responsibilities of E-UTRAN are as follows:

- Radio Resource Management (RRM): RRM includes radio bearers

related functions such as radio admission control, radio bearer control, scheduling,

radio mobility control and dynamic allocation of resources in downlink and uplink

to UEs.

- Header Compression: Due to IP header compression, the radio interface

can be utilized efficiently in case of small IP packets.

- Security: The data sent to the radio interface is secured by encryption.

- Connectivity to the EPC: Connectivity to the EPC consists of bearer path

towards S-GW and signaling towards the MME.

The functions described above reside in the eNodeB for network

prospective. In contrast to previous generation technologies, LTE embed radio

controller functionalities into eNodeB which allows tight interaction between the

protocol layers of AN. This distributed control eliminates the need for a processing

intensive radio controller which in turn reduces the cost and avoids a “single point

of failure”. In addition, due to absence of the radio controller improve the

efficiency of the network by reducing the latency. There is no soft handover in

LTE, which eliminates the need for a centralized data combining function.

The WiMAX Architecture

The WiMAX architecture is based on a network reference model to define

end-to-end WiMAX network.

The network reference model for WiMAX was developed by the WiMAX

Network Working Group (NWG). The model defines the entire WiMAX network.

The NRM ensures interoperability between various WiMAX enabled devices and

operators. The network architecture is based on IP services and it can be logically

divided into three parts; Mobile Station, Access Service Network and Connectivity

Service Network. The network reference model is described in Figure 2.3[15].

Mobile Station (MS): Used to access the network.

33

Access Service Network (ASN): Comprised of ASN GWs (Gateways) and

BSs to form Radio Access Network (RAN) at the edge.

Base Station: Provides air interface to MS. In addition, BS is responsible

for handoff triggering, radio resource management, enforcement of QoS policy,

Dynamic Host Control Protocol (DHCP) proxy, session management, key

management and multicast group management.

Access Service Network Gateway: Acts as layer 2 traffic aggregation point

within an ASN[14]. In addition, ASN-GW performs AAA client functionality,

establish and manage mobility tunnel with BSs, foreign agent functionality for

mobile IP and outing towards selected Connectivity Service Network (CSN).

Figure 2.3 Network Reference Model for WiMAX

Connectivity Service Network: Provides IP connectivity to internet, PSTN

(Public Switched Telephone Network), ASP and corporate networks. In addition, it

provides core IP functions. CSN is owned by the Network Service Provider (NSP),

and is comprised of AAA servers, Mobile IP Home Agent (MIP-HA), Operation

34

Supports Systems (OSS) and gateways. AAA servers are used to authenticate

devices, users and specific services. CSN has following responsibilities:

- IP address Management.

- Mobility, roaming and location management between ASN’s.

- Roaming between NSPs by Inter-CSN tunneling.

The logical link that connects two functional groups is called Reference

Point (RP). The NRM shown in Figure 2.3 has 8 RPs ranges from R1 to R8. The

description of RPs is given in Table 2.1.

Table 2.1: Description of Reference Points

ReferencePoints Description

R1 Connect Mobile Station (MS) and ASN

R2 Connect MSN and CSN

R3 Connect ASN and CSN

R4 Connect twoASNs

R5 Connect two CSN

R6 Connect BS and ASN- GW

R7 Represents the internal communication

within the gateway.

R8 Connect two Base Stations (BSs)

2.3 Air Interface Radio Aspects

The air interface radio aspects accounts for various radio transmission and

reception specifications.

Frequency bands

The LTE inherits all the frequency bands defined for UMTS, spectrum

which typically consists of the 800 MHz, 900 MHz, 1800 MHz and 1900

35

MHz.Depending on regional and local variables LTE deployments can be

undertaken in the any of the band range of 800 MHz to 2.62 GHz. WiMAX was

first designed for Line of-Sight (LOS) environments (IEEE 802.16c) at high

frequency bands of 10 66 GHz. Later versions (IEEE 802.16a, d, e) support Non-

Line- of-Sight (NLOS) modes in radio bands between 2-11 GHz.

Radio Access Modes

Both the LTE and WiMAX air Interface support FDD and TDD modes. The

earlier versions of WiMAX, prior to IEEE 8o2.16e (prior to WiMAX Forum

Release 1.5) only supported the TDD mode. The FDD mode in WiMAX defines a

half duplex FDD mode to support lower complexity terminals which time shares

the hardware resources between the uplink and downlink. This mode is in

consideration for LTE.

Data rates

Peak data rates for LTE range from 100 to 326.4Mbps on the downlink and

50 to 86.4 Mbps on the uplink depending on the antenna configuration and

modulation depth. The WiMAX systems have peak data rate capabilities of 75

Mbps in the downlink and 25 Mbps in the uplink.

2.4 Multiple Access Technology

Downlink and uplink transmissions in LTE and WiMAX are based on the

multiple access technologies. A technology called Orthogonal Frequency Division

Multiple Access (OFDMA) is used for downlink transmission of LTE and for

uplink and downlink transmission of WiMAX. The uplink transmission for LTE

uses a new technology called SC-FDMA (Single Carrier Frequency Division

Multiple Access). The SC-FDMA is superior to OFDMA, however is restricted to

LTE uplink because the increased time domain processing of SC-FDMA would

36

entail considerable burden on base stations. Both OFDMA and SC-FDMA

physical layer technologies are detailed further.

OFDMA (WiMAX Uplink/Downlink and LTE Downlink)

OFDMA is derived from OFDM (Orthogonal Frequency Division

Multiplexing), a digital multi-carrier modulation scheme which uses the principle

that information can be transmitted on a radio channel through variations of a

carrier signal's frequency, phase or magnitude. Instead of transmitting all the

information on to a single radio frequency carrier signal, the high data rate input

stream is multiplexed into parallel combination of low data rate streams. The

parallel streams are modulated onto separate subcarriers in the frequency domain

through the use of inverse fast Fourier transform (IFFT) and transmitted through

the channel. At the receiver, the signal is demodulated using an FFT process to

convert a time varying complex waveform back to its spectral components,

recovering the initial subcarriers with their modulation and thus the original digital

bit stream. The figure below shows frequency and time domain representation of

an OFDM signal.

Figure-2.4: OFDM signal representation in frequency and time domain

In OFDM, the subcarriers are spaced closely together without any guard

bands in frequency domain and use the FFT to convert the digital signals from time

37

domain into a spectrum of frequency domain signals that are mathematically

orthogonal to each other. The frequency domain null of one subcarrier corresponds

to the maximum value of the adjacent subcarrier which allows subcarriers to

overlap without interference and thus conserve bandwidth. By using TDMA with

basic OFDM, OFDMA is achieved thus allowing dynamic allocation of subcarriers

among different users on the channel. OFDMA provides a robust system with

increased capacity and resistance to multipath fading. The figure below shows the

OFDM and OFDMA subcarrier allocation.

Figure-2.5: OFDM and OFDMA subcarrier allocation

In LTE and WiMAX, each subcarrier is modulated with a conventional

modulation scheme depending on the channel condition. LTE uses QPSK,

16QAM, or 64QAM while WiMAX uses BPSK, QPSK, 16QAM, or 64QAM for

modulation at a low symbol rate. The FFT sizes of 128, 256, 512,1024 and 2048,

corresponding to WiMAX and LTE channel bandwidth of 1.25, 2.5, 5,10 and

20MHz are used. In time domain, guard intervals known as cyclic prefix (CP) are

inserted between each of the symbols to prevent inter-symbol interference at the

receiver caused by multi-path delay spread in the radio channel. The normal CP for

LTE is 4.69 µs while for WiMAX it is 1/8 the length of OFDMA symbol time,

typically 11.43 for OFDMA symbol duration of 102.86 µs. The detailed values and

configurations are listed further in the comparison of Modulation Parameters. The

CP is a copy of the end of the symbol inserted at the beginning. The figure below

shows OFDMA transmitting a series of QPSK data symbols.

38

Figure-2.6: OFDMA transmitting a series of QPSK data symbols

SC-FDMA (LTE uplink)

The LTE uses a new modulation technique called Single Carrier Frequency

Division Multiple Access which in essence creates a single carrier waveform and

shift it to the desired part of the frequency domain. This new technique provides

robust resistance to multipath without the problem of high PAR (Peak-to-average

ratio) Gaussian noise which occurs in OFDMA as the number of subcarriers

increase. The figure below provides a comparison in time and frequency domain

between SC-FDMA and OFDMA transmitting a sequence of four (M) QPSK data

symbols. In real, LTE signals are allocated in units of 12 adjacent subcarriers.

39

Figure-2.7: Comparison of OFDMA and SC-FDMA transmitting a series of QPSK

datasymbols

The SC-FDMA transmits the data symbols in series at four (M) times the

rate; with each data symbol occupying M x 15 KHz; as against OFDMA which

transmits the symbols in parallel, one per subcarrier. The SC-FDMA signal

appears to be more like a Single Carrier (hence the name 'SC') with each data being

represented by one wide signal. The SC-FDMA symbol contains M 'sub-symbols'

that represent the modulating data.

By transmitting M data symbols at M times the rate, the SC-FDMA

occupied bandwidth is the same as multicarrier OFDMA, but the PAR (Peak-to-

Average Ratio) remains the same as used in the original data symbols and does not

approach the Gaussian noise as in OFDMA.

40

2.5 Modulation Parameters

The modulation parameters such as system bandwidth, sampling frequency,

FFT size, subcarrier spacing, symbol duration, cyclic prefix for LTE and WiMAX

are compared below.

LTE

The LTE has a scalable channel bandwidth selectable from 1.25 to 20 MHz

with available system profiles of 1.25,1.4,2.5,3,5,10,15, and 20 MHz with both

FDD and TDD. It uses a subcarrier spacing of 15 KHz. If eMBMS (evolved

Multimedia Broadcast Multicast system), a technique to combine multi-cell

transmissions in the UE is used, the subcarrier spacing of 7.5 KHz is deployed.

The subcarrier spacing in LTE is constant and is independent of channel

bandwidth. The OFDMA and SC-FDMA symbol length is the same at 66.7 µs over

which the subcarriers of 15 KHz (downlink OFDMA) and 60 KHz (uplink SC-

FDMA) are each modulated by one QPSK data symbol. The smallest amount of

allocated resource in both the downlink and uplink is called a resource block (RB)

which is 180 KHz wide and lasts for 0.5 ms. An RB consists of 12 subcarriers at

15 KHz subcarrier spacing while for eMBMS the RB is 24 subcarriers at 7.5 KHz

spacing.

WiMAX

The WiMAX also has variable channel bandwidth and ranges from 1.25 to

20MHz with available system profiles of 1.25, 2.5, 5,10 and 20 MHz. The

WiMAX however uses a subcarrier spacing which for a given channel bandwidth

is inversely proportional to the number of subcarriers. The time duration of the

OFDMA symbol is set by the inverse of the subcarrier spacing. The inverse

relationship between the subcarrier spacing and symbol duration is a necessary and

sufficient condition to ensure that the subcarriers are orthogonal. The table below

lists the LTE modulation parameters as specified for mobile WiMAX 802.16e.

41

Table-2.2: WiMAX 802.16e Modulation Parameters

2.6 Multiple Antenna Techniques

The Antenna technologies play a very important role in any radio

transmission. Multiple antenna techniques intent to improve the signal robustness

and increase the system capacity and user data rates by taking advantage of the

spatial diversity of the radio channel. LTE and WiMAX use appropriate Multiple

Antenna Techniques to provide signal robustness and improve its system

performance. The figure below illustrates various antenna techniques from

simplest to more complex.

42

Figure-2.8 Antenna Techniques

WiMAX and LTE use multiple antenna configurations in uplink and

downlink in order to increase capacity, diversity, data rates and efficiency as

compared to single antenna systems.WiMAX support 1, 2, 4 antennas at the BS

and 1, 2 antennas at the MS.

The antenna configuration supported by LTE DL is (2x2) and (4x4) having 2

or 4 antennas at eNodeB and 2 or 4 antennas at UE. The UL of LTE supports 2x2

MIMO having 2 antennas at UE as well as at eNodeB. In addition, the number of

code words used by LTE is 2 which are independent of the antenna configuration.

43

2.7 Radio Interface Protocol Architecture

LTE

The figure below shows the radio interface protocol architecture defined for

the LTE system.

Circles between different layers or sub-layers indicate Service Access Points

(SAPs)

Figure-2.9: LTE Radio interface protocol architecture around the physical layer

The LTE Physical Layer provides the data transport services to the higher

layers which are accessed through the transport channels via the Layer 2 MAC

sub-layer. The MAC layer provides the logical channels to the Layer 2 RLC

(Radio Link Control) sub-layer. The Physical layer also has an interface with the

Layer 3 RRC (Radio Resource Control) layer.

A detailed Protocol Stack for Control Plane and User Plane defined for LTE

are depicted and illustrated below.

44

Figure-2.10: LTE Control Plane Protocol Stack

The Physical layer is concerned with the modulation and encoding/decoding

of the transport channels. The MAC layer handles the Hybrid Automatic Repeat

Request (HARQ) and mapping functions. The RLC (Radio Link Control) layer

provides segmentation, concatenation and ARQ services. In the control plane, the

PDCP (Packet Data Convergence Protocol) performs ciphering and Integrity

protection and transfer of control plane data between RRC and RLC layers. In the

user plane it performs header compression and decompression, ciphering and

transfer of user data between RRC and RLC layers. The RRC (Radio Resource

control) layer handles the mobility and handover control tasks. The protocols of

the Non-Access Stratum (NAS) in the control plane terminate in the wireless

device and in the Mobility Management Entity (MME) of the core network.

45

Figure-2.11: LTE User Plane Protocol Stack

WiMAX

The IEEE 802.16 uses the first two layers of the Open System

Interconnection (OSI) model. The PHY layer uses OFDM and Orthogonal

Frequency Division Multiple Access (OFDMA) as transmission techniques

whereas data link layer is divided into MAC and Logical Link Control (LLC) sub-

layers. The MAC layer is further divided into three sub-layers called Security

Sublayer, MAC Common Part Sublayer (MAC CPS) and Convergence Sublayer

(CS). The protocol stack of WiMAX is shown in Figure 2.12, and consists of the

first two layers (PHY and Data link) of OSI reference model. The upper layers

include network, transport, session, presentation and application layers of OSI

model.

46

Figure 2.12 Protocol Stack of IEEE 802.16

PHY layer of WiMAX not only establishes the connection between

communicating devices but is also responsible for defining the

modulation/demodulation type for transmission of the incoming bit sequence. It

uses OFDM and OFDMA as transmission schemes, which uses the frequency band

between 2-11 GHz. The frequency band below 11 GHz makes possible NLOS

wireless communication and the use of OFDM reduces multipath effects and Inter

Symbol Interference (ISI). PHY layer uses FDD and TDD as duplexing

techniques.

MAC provides the interface between PHY layer and the transport. From a

transmission prospective, MAC layer takes the packets from the upper layers and

organizes them in Protocol Data Units (PDU’s) for transmission over the air. The

CS of the MAC layer can interface with the protocols of upper layers.

Consequently, WiMAX supports both IP and Ethernet protocol. CS takes the

MSDU’s from upper layers and do key processing such as payload compression.

After payload compression the MSDU’s are sent to CPS through Service Access

Point (SAP). CS can accept data frames from the CPS. The MAC CPS is the core

part of the MAC layer and is responsible for connection maintenance, bandwidth

allocation, PDU framing, duplexing and channelization.The CPS takes MSDU’s

from the CS and organizes them in form of MPDU by performing fragmentation

47

and segmentation.CPS provides the connection identifier to identify the serving

MPDU, when MAC layer is connected to Subscriber Stations (SSs). The main goal

of the SS is to ensure privacy services to the subscribers across the wireless

network and give protection from theft of services to the operators. It provides

encryption, authentication and secure key exchange functions on MPDUs and

sends them to the PHY layer for further processing. The security sublayer connects

the MAC CPS and the PHY layer and provides the necessary methods for

encryption and decryption of data. Security sublayer is also used for authentication

and the secure exchange of keys.

The data, control and management plane of WiMAX are shown in

Figure 2.13.

Figure 2.13: Architecture of WiMAX

2.8 Frame Structure

The frame structures used in the LTE and WiMAX systems are presented in

the comparison below.

48

LTE

LTE uses two radio frame structures: frame structure type 1 (FS1) for full

duplex and half duplex FDD, and frame structure type 2 (FS2) for TDD. The

FS1framestructureisshowninfigurebelow.

Figure-2.14: LTE FS1 frame structure

FS1 is optimized to co-exist with the 3.84 Mbps UMTS systems. This

structure consists of ten 1 ms sub-frames, each composed of two 0.5 ms slots, for a

total duration of 10 ms. The FS1 is identical in the uplink and downlink in terms of

frame, sub-frame, and slot duration however the allocation in terms of physical

signals and channels is different. The uplink and downlink transmissions are

separated in the frequency domain[7].

The FS2 has a more flexible structure than FS1. The FS2 frame structure is

shown in the figure below.

49

Figure-2.15: LTE FS2 frame structure for 5 ms Switch-point periodicity

The example of FS2 above consists of two 5 ms half-frames for a total

duration of 10 ms for a 5 ms switch-point periodicity. Sub-frames consist of either

an uplink or downlink transmission, or a special sub-frame containing the

downlink and uplink pilot timeslots (DwPTS and UpPTS) separated by a

transmission gap (GP). The allocation of sub-frames for the uplink, downlink and

special sub-frames is determined by one of the seven different configurations. Sub-

frames 0 and 5 are always used for downlink transmissions, while sub-frame 1 is

always a special sub- frame. The composition of other sub-frames varies based on

the configuration.

WiMAX

The WiMAX 802.16e physical layer supports both TDD and FDD operation.

The WiMAX IEEE 802.16e Release 1.0 includes only TDD profile while the FDD

profile was added in Release 1.5.

The figure below shows the TDD frame structure used in WiMAX 802.16e

Release 1.0.

50

Figure-2.16: Mobile WiMAX frame structure and channelization for TDD system

Each frame is configured to be 5 ms long and is time-division duplexed into

downlink (DL) and uplink (UL) sub-frames. To avoid interference between

downlink and uplink signals, they are separated by small time gaps called Transmit

Time Gap (TTG) for the transition from downlink sub-frame to uplink sub-frame

and Receive Time Gap (RTG) for the transition from uplink sub- rame to downlink

sub-frame.

At the beginning of each frame, downlink control information is transmitted

and has a preamble, a Frame Control Header (FCH) and a Media Access Protocol

(MAP) message. The physical channels defined in the WiMAX frame and their

functionalities are detailed below:

• Preamble

It is broadcast in the first OFDM multiplexed symbol of the frame in DL and

used by the MS for BS identification, timing synchronization and channel

estimation. There are no preambles in the UL except for systems using AAS

(Adaptive Antenna System).

• Frame Control Header (FCH)

It follows the preamble and provides the frame configuration information,

such as MAP message length and coding scheme and usable sub-channels.

51

• DL-MAP and UL-MAP

The DL-MAP and UL-MAP provide resource allocation and other control

information for the DL and UL sub-frames, respectively. To reduce the MAP

overhead, the system supports multicast sub-MAPs that can carry traffic allocation

messages at higher Modulation and coding Scheme (MCS) levels for users closer

to the BS and with higher CINR conditions. Each MAP message includes several

information elements (lEs), and has a fixed part and a variable part. The size of

variable part is proportional to the number of downlink and uplink users scheduled

in that frame. The MAP contains the information such as the frame number,

number of zones, and the location and content of all bursts. Each burst is allocated

by its symbol offset, sub-channel offset, the number of sub-channels, number of

symbols, power level, and repetition coding.

• UL Ranging

The UL ranging sub-channel is allocated for an MS to perform closed-loop

time frequency and power adjustment, and bandwidth requests.

• UL CQICH (Uplink Channel Quality Indicator Channel)

The UL CQICH is allocated for the MS to provide feedback of channel state

information.

• UL ACK (Uplink Acknowledgement)

The UL ACK is allocated for the MS to feedback DL HARQ ACKs.

2.9 Quality of Service (QoS)

LTE supports "End-to End" QoS, meaning that bearer characteristic are

defined and controlled throughout the duration of a session between the mobile

device (UE) and the P-GW. QoS is characterized by an index, QCI (QoS Class

Identifier), and the parameter ARP (Allocation and Retention Priority). Bearer

types belong to two main classes with guaranteed and non guaranteed rates and

LABELS specify in more detail what values of packet delay and loss can be

tolerated for any given bearer[10].

52

The WiMAX MAC layer has a connection oriented architecture that is

designed to support a variety of applications, including voice and multimedia

services. WiMAX supports five types of QoS: UCS (Unsolicited Grant Service),

rtPS (Real time polling Service), ertPS (Extended Real-time Polling Service),

nrtPS (Non real-time Polling Service and BE (Best effort service). The Unsolicited

Grant Service (UGS) is designed to support real time service flows that generate

fixed size data packets on a periodic basis, such as T1/E1 and Voice over IP

without silence suppression. WiMAX MAC is designed to support a large number

of users, with multiple connections per terminal, each with its own

QoSrequirement[11].

2.10 Mobility

Mobile WiMAX supports idle mode and sleep mode connectivity. In idle

mode, UE is not registered with the BS whereas in sleep mode UE may scan

neighboring base stations or may power down. Mobile WiMAX supports three

types of handovers; Hard Handover (HHO), Macro Diversity Handover (MDHO)

and Fast Base Station Switching (FBSS). HHOs are mandatory in mobile WiMAX

whereas FBSS and MDHO are used optionally. Mobility speeds supported by

mobile WiMAX are up to 120 km/h.

LTE supports RRC_IDLE and RRC-CONNECTED modes to provide

mobility. In contrast to WiMAX, LTE supports Inter Cell Soft Handovers and Inter

RAT handovers with mobility speeds up to 350 km/h.

2.11 Security

LTE specifies a new layering of security and the enforcement of a clearer

separation of control plane security and user plane security providing strong

security features. LTE has support for UEA1(UMTS Encryption Algorithm),

UIA1(UMTS Integrity Algorithm), UEA2 (SNOW algorithm supporting 256 bits

53

of keys) and UIA2. Signaling at UPE(User Plane Entity) and MME relocation

allows the transfer of algorithm information to target UPE, MME and UE[12].

WiMAX supports strong encryption, using Advanced Encryption Standard (AES),

and has a robust privacy and key management protocol. It supports Privacy and

Key Management – PKMv1 RSA(Rivest-Shamir-Adleman), HMAC(Hash

Message Authentication Code), AES CCM(Counter mode, Cipher block chaining,

Message authentication code) and PKMv2 – EAP(Extensible Authentication

Protocol), CMAC(Cipher-based Message Authentication Code),

AES-CTR(Advanced Encryption Standard - Counter), MBS(Multicast Broadcast

Services) Security. The AES and the 3DES(Triple Data Encryption Standard) are

mandatory features and new high performance coding schemes, such as TC and

Low Density Parity Check (LDPC) are included. The system also offers very

flexible authentication architecture based on Extensible Authentication Protocol

(EAP), which allows for a variety of user credentials, including

username/password, digital certificates, and smart cards[11].

2.12 Comparison Summary

The key highlights of the comparison between the two next generation

broadband wireless access technologies: 3GPP LTE and WiMAX IEEE 8o2.16e is

presented in the table below.

Table-2.3 Highlights of LTE and WiMAXcomparation

Aspect 3GPP-LTE Mobile WiMAX

(IEEE 8o2.16e)

Legacy GSM/GPRS/EDGE/UMTS/HSPA IEEE 802.16 a through d

Core Network UTRAN moving towards All-IP

Evolved-UTRA (E-UTRA) core

network with IMS with SAE

Architecture

WiMAX forum All-IP

network

54

Access

technology:

Download (DL) OFDMA OFDMAUplink (UL) SC-FDMA OFDMA

FFT Sizes 64,128, 256, 512,1024, 2048 128, 256, 512,1024, 2048

Radio Access TDD and FDD TDD and FDDModes

Frequency Band Existing (800, 900,1800,1900

MHz) and new frequency

bands (Range 800 MHz - 2.62

GHz)

2-11 GHz

Peak Data rate:

DL

UL

100 to 326.4Mbps

50 to 86.4 Mbps

75 Mbps

25 Mbps

Channel Scalable from 1.25 to 20 MHz

with system profiles 1.25,1.4,

2.5, 3, 5,10,15, and 20 MHz

Scalable from 1.25 to 20

MHz with system profiles

1.25,2.5, 5,10,20 MHz

bandwidth

Cell radius 5 Km ~20.7 km for 3.5 or 7MHz

BW

~8.4 km for 5 or 10 MHz

BW

Cell Capacity >200 users for 5MHz

>400 users for larger BW

100-200 users

Mobility: Up to 350 Km/h Inter-cell soft

handovers supported

Up to 120 Km/h Optimized

hard handovers supportedSpeed Handover

55

Antenna Scheme:

Downlink

Uplink

Number of code

words

MIMO

2x2, 2x4, 4x2, 4x4

1x2, 1x4, 2x2, 2x4

2

MIMO

2x2, 2x4, 4x2, 4x4

1x2, 1x4

1

Roaming New Auto through existing

GSM/UMTS

Security

Algorithms

UEA1,UIA1,UEA2 and UIA2 PKMv1 RSA, HMAC,

AES-CCM and PKMV2 -

EAP, CMAC, AES-CTR,

MBS security


We conclude that both WiMAX and LTE are technically similar standards.

However, there are some differences present in the uplink access method used by

both technologies. LTE uses SC-FDMA whereas WiMAX uses OFDMA as an

access method. The adaptation of SC-FDMA in the uplink gives edge to LTE over

WiMAX because it resolves the PAPR problem of OFDMA due to its single

carrier nature.

We also conclude that, LTE gives better data rates in the uplink and

downlink due to support of MIMO system as compared to WiMAX which only

supports MIMO in the downlink direction.

We know brief difference and similarity between LTE and WiMAX

technologies. In next chapter, features of some main systems of this technologies

are analysed by simulation for detail studying.

56

3. SIMULATION OF LTE UPLINK IN COMPARISON WITH

AN OFDM SYSTEM

3.1 Introduction

This chapter presents simulation results along with underlying assumptions.

In the first part, we investigated LTE uplink and performed link level simulations

of Single Carrier Frequency Domain Equalization (SC-FDE) and SC-FDMA in

comparison with OFDM. We have used two types of multipath channels, i.e. ITU

Pedestrian A and ITU Vehicular A channels. In addition an Additive White

Gaussian Noise (AWGN) channel is also used. Furthermore, the simulation of

PAPR is performed for SC-FDMA and OFDMA systems. In the second part of this

chapter, we analyzed the capacity of the MIMO system and performed a

comparison with SISO.

All simulations are performed in MATLAB 7.40 (R2007a).

3.2 Link Level Simulation of SC-FDE

SC-FDE is a frequency domain equalization technique used to minimize the

frequency selective fading effects in LTE uplink. SC-FDE has similar spectral

efficiency and link level performance as OFDM. However, it has certain

advantages upon OFDM due to usage of Discrete Fourier Transform(DFT) and

Inverse Discrete Fourier Transform(IDFT) in the receiver. The block diagrams

used in the link level simulation of SC-FDE and OFDM are shown in Figure 3.1

and 3.2 respectively. We can see the similarity between two block diagrams as

they contain the same signal processing blocks.

57

The parameters used in simulation are described in Table 3.1. The

parameters are chosen only for 5 MHz transmission bandwidth of LTE system.

The number ofiterations used in the Monte Carlo simulation are 10^4. A Monte

Carlo simulation is a method which repeatedly counts the number of transmitted

symbols and symbol errors on every iteration.

Table 3.1: Simulation Parameters and Assumptions

Parameters Assumptions

System Bandwidth 5 MHz

Sampling Rate 5 Mega-samples per second

Pulse Shaping None

Modulation Format QPSK

Cyclic Prefix 4 μsor 20 samples

Subcarrier Spacing 5 MHz / 512 = 9.765 kHz

IFFT Size 512 Points

Input BlockSize 16 Symbols

Input FFT size 16

Channel coding None

Number of iteration 10^4

Equalization Minimum Mean Square Error (MMSE),

Zero Forcing (ZF)

Channel ITU Pedestrian A, ITU Vehicular A and

AWGN.

Detection Hard

ConfidenceInterval 32

58

Figure 3.1: Block Diagram of SC-FDE Link Level Simulator

Figure 3.2: Block Diagram of OFDM Link Level Simulator

59

The simulation results compute Symbol Error Rate (SER) for the

performance measurement of SC-FDE and OFDM in various scenarios.

SER for SC-FDE and OFDM using Minimum Mean Square

Error(MMSE) as Equalization Scheme

We have calculated SER measurement of SC-FDE and OFDM by using

three types of channels, ITU Pedestrian A, ITU Vehicular A and AWGN channel.

The equalization scheme used to obtain the SER curves is MMSE.

Figure 3.3: Comparison of SC-FDE and OFDM using MMSE Equalization in

Pedestrian A, Vehicular A and AWGN Channels

Simulation results show that in case of AWGN channel SC-FDE and OFDM

has similar SER performance. However, in case of Pedestrian A and Vehicular A

channel, SC-FDE outperforms the OFDM. As we know OFDM needs additional

channel coding to achieve this performance due to its sensitive nature to carrier

60

frequency. The comparative summary obtained from Figure 3.3 is described in

Table 3.2 and Table 3.3.

Table 3.2: Comparison between SC-FDE and OFDM in Various Channels Using

MMSE Equalization

Channels SNR (indB) SER

SC-FDE AWGN 10 0.001566

Pedestrian A 10 0.004029

Vehicular A 10 0.0577

OFDM

AWGN 10 0.001566



The Table 3.2 clearly shows that SC-FDE significantly reduces SER

as compared to OFDM in Vehicular A and Pedestrian A Channel.

Table 3.3: Comparison between SCFDE and OFDM in Vehicular A Channel using

MMSE Equalization

Channel SNR (indB) SER

SC-FDE Vehicular A 16 0.001578

20 8.594e-006

OFDM Vehicular A 16 0.02622

20 0.013

Table 3.3 illustrates an important result i.e. as SNR increases the SC-

FDE sharply reduces the Symbol error rate as compared to OFDM in case of

vehicular channel.

61

SER for SC-FDE and OFDM using Zero Forcing

The calculation of SER is performed using Zero Forcing as equalization

scheme for the comparison of SC-FDE and OFDM in AWGN, ITU Pedestrian A

and ITU Vehicular A channel.

Figure 3.4: Comparison of SC-FDE and OFDM using Zero Forcing Equalization

Simulation results show that SC-FDE outperforms the OFDM in case of

multipath channels i.e. ITU Pedestrian A and ITU Vehicular A channel. We see

that in case of Vehicular A channel, OFDM has a continuous reduction of SER and

it significantly minimizes the SER up to certain values of SNR as compared to SC-

FDE. However, SC-FDE outperforms OFDM for higher values of SNR. The

comparative summary of the results obtained from the simulation are shown in

Figure 3.4 and described in Table 3.4 and 3.5.

62

Table 3.4: Comparison of SCFDE and OFDM in various Channels

using Zero Forcing

Channels SNR (indB) SER

SC-FDE AWGN 10 0.001578



OFDM AWGN 10 0.001578



Table 3.4 shows that SCFDE has better performance in case of AWGN and

Pedestrian channel while OFDM is better in case of vehicular channel.

Table 3.5: Performance of SCFDE and OFDM using Zero Forcing in

Vehicular A Channel

Channel SNR (indB) SER

SC-FDE Vehicular A 14 0.1004

18 0.009742

22 4.492e-005

OFDM Vehicular A 14 0.04008

18 0.01804

22 0.009223

Table 3.5 shows that OFDM gives better performance for smaller values of

SNR but for higher values, the SC-FDE significantly reduces SER as compared to

OFDM system which continuously reduces the error as the value of SNR is

increased.

We observe from Figure 3.3 and 3.4 that MMSE gives better performance as

compared to zero forcing.

63

Comparison of SC-FDE and OFDM with/without CP

The comparison of SCFDE and OFDM is performed in Vehicular channel

with and without CP. The equalization scheme used in this simulation is MMSE.

Figure 3.5: Comparison of SC/FDE and OFDM with or without CP using

Vehicular Channel

Figure 3.5 shows that the use of CP reduces the SER as compared to the

system having no CP. In addition, it is clearly shown that SC-FDE system gives

low SER as compared to OFDM. Table 3.6 summarizes the comparison obtained

from simulation.

64

Table 3.6: Comparison of SC-FDE and OFDM With and Without CP

Channel

With CP Without CP Equalization

SNR

(indB)

SER SNR

(indB)

SER

SC- FDE

Vehicular A

16 0.00155 16 0.00377

18 0.0001684 18 0.00203

20 7.813e-006 20 0.00167

OFDM

Vehicular A

16 0.02626 16 0.02895

18 0.01823 18 0.02083

20 0.01292 20 0.01611

3.3 Link Level Simulation of SCFDMA

The simulation flow for SCFDMA is shown in Figure 3.6. We have

investigated two types of subcarrier mapping schemes for SCFDMA and compared

their performance in terms of SER and SNR. The types of subcarrier mapping

schemes are Interleaved FDMA (IFDMA) and Localized FDMA (LFDMA).

Parameters used in simulation are given in Table 3.7.

Table 3.7: Simulation Parameters of SC-FDMA



FFT Size 512

BlockSize 16 symbols

CP Length 20 samples

Rangeof SNR 0 to 30 dB

Modulation QPSK


Channel AWGN, Pedestrian A and Vehicular A.

MMSE

65

Equalization MMSE

Confidence Interval 32

Figure 3.6: System Model of SC-FDMA

66

Figure 3.7: Comparison of SER with Various Subcarrier Mapping Schemes

Figure 3.7 presents the performance of SC-FDMA system using subcarrier

mapping schemes IFDMA and LFDMA for various channels. It is clear from the

simulation that LFDMA outperforms the IFDMA in all channel conditions and

gives better performance.

67

Figure 3.8: SER Performance of SC-FDMA System Using Various Subcarrier

Mapping Schemes

Figure 3.8 presents the SER performance of SC-FDMA system in AWGN

and Pedestrian A channel using two subcarrier mapping schemes. In case of

AWGN channel, we see that IFDMA and LFDMA have similar performance

whereas for Pedestrian A channel the two subcarrier schemes have different SER

performance. In addition, it is clearly shown that the performance of IFDMA

system does not depend on location of subband and gives approximately similar

SER curves for subband 0 and subband 15. This is due to the inherent

characteristic of frequency diversity of the IFDMA scheme. As for LFDMA, the

performance of SC-FDMA is better in case of subband 0 and worst in case of

subband 15. This is because of channel gain which is higher than average at

subband 0 and below to average at subband 15.

68

3.4 Peak -to- Average Power Ratio

Peak to average power ratio is defined as “the ratio of peak signal power to

the average signal power”.

Mathematically, PAPR can be written as

Where

: n =0, 1, …, N-1 are the time domain symbols that come after the IDFT.

Wc= Carrier Frequency

symbol duration, and

P(t) = Baseband Pulse.

The simulation model for calculating PAPR of SC-FDMA system is shown

in Figure 3.9.

69

Figure 3.9: Simulation Model of PAPR Calculations for SCFDMA

For pulse shaping we used Raised Cosine (RC) and Square Root Raised

Cosine (RRC) filters because they make the receiver robust against timing

synchronization errors. The parameters used for the calculation of PAPR are

illustrated in Table 3.8. For the calculation of PAPR we use Complementary

Cumulative Distribution Function (CCDF). The CCDF is defined as the probability

for which PAPR is greater than any PAPR value i.e. PAPR0.

CCDF: Pr (PAPR >PAPR0)

Table 3.8: Parameters used in the simulation of PAPR calculation for SCFDMA


SystemBandwidth 10 MHz

Number of Subcarriers (N) 512

Number of Symbols (M)

Spreading Factor for IFDMA (Q)

128

Q= N/M=4

Spreading Factorfor LFDMA 2

Roll of Factor 0.25

70

Over Sampling Factor 4


Subcarrier Mapping Schemes IFDMA,DFDMA,LFDMA


PAPR-SCFDMA Calculation Using QPSK

The PAPR calculation using various subcarrier mapping schemes for

SCFDMA system is shown in Figure 3.10. The modulation scheme used for the

calculation of PAPR is QPSK.

Figure 3.10: Comparison of CCDF of PAPR for DFDMA, IFDMA and LFDMA

using QPSK

Figure 3.10 show that IFDMA gives lowest PAPR values as compared to

other subcarrier mapping schemes (DFDMA and LFDMA).

PAPR-SCFDMA Calculation Using 16-QAM

71

The PAPR calculation using various subcarrier mapping schemes for SC-

FDMA system is shown in Figure 3.11. The modulation scheme used for the

calculation of PAPR is 16-QAM.

Figure 3.11: Comparison of CCDF of PAPR for IFDMA, DFDMA and LFDMA

using 16-QAM

Figure 3.11 show that IFDMA has lowest value of PAPR at 3.2dB which is

0dB in case of QPSK as modulation technique. We can also observe from the

figure that we get higher values of PAPR by using 16-QAM which is undesirable

because they cause non linear distortions at the transmitter.

PAPR Calculation for OFDMA

We know theoretically that OFDMA gives higher PAPR values as compared

to SCFDMA due to its multicarrier nature. In addition, there is no pulse shaping

72

filter used in OFDMA. The simulation model for the calculation of PAPR for

OFDMA system is shown in Figure 3.12.

Figure 3.12: Simulation Model of PAPR Calculations for OFDMA

The simulation parameters used in the simulation are described in Table 3.9.

Table 3.9: Parameters Used in the Simulation of PAPR-Calculation

for OFDMA



Number of Subcarriers (N) 512

Number of Symbols (M) 128

Over Sampling Rate 4

Number of Iterations 10^4


Figure 3.13 shows the PAPR calculation of OFDMA system using QPSK

and 16-QAM modulation techniques. The graph shows that the PAPR value of

OFDMA system is much higher than SC-FDMA system. We can also observe that

the behavior of CCDF(Complementary Cumulative Distribution Function) is quite

similar in case of QPSK and 16-QAM.

73

Figure 3.13: Comparison of CCDF of PAPR for OFDMA using QPSK and 16-

QAM

3.5 Capacity of MIMO System

MIMO system consists of multiple transmit and receive antennas

interconnected with multiple transmission paths. MIMO increases the capacity of

system by utilizing multiple antennas both at transmitter and receiver without

increasing the bandwidth.

Where,

r = rank of matrix

λ= Positive eigenvalues of HHH(as HH is the conjugate of H)

ρ= SNR

Capacity of SISO= log2 (1+ ρh2)

74

Figure 3.14: Comparison of MIMO and SISO system in terms of Capacity

Figure 3.14 shows the comparison between MIMO and SISO systems in

terms of capacity. The graph depicts that the capacity of system can be increased

by increasing the number of antennas at transmitter and receiver. The graph also

show that 8x8 MIMO system has larger capacity whereas SISO system as lowest

capacity.

Table 3.10 summarizes simulation results obtained from Figure 3.13.

For SNR= 5dB

Table 3.10: Comparison between MIMO and SISO System with SNR=5 dB

Antenna Configuration Capacity (bits/s/Hz)

SISO 2.589

MIMO (2x2) 4.589

MIMO (3x2) 5.325

MIMO (4x4) 7.907

75

MIMO (8x8) 13.7

For SNR= 14dB

Table 3.11: Comparison between MIMO and SISO System with SNR=14 dB

Antenna Configuration Capacity (bits/s/Hz)

SISO 4.89

MIMO (2x2) 8.485

MIMO (3x2) 9.941

MIMO (4x4) 14.83

MIMO (8x8) 27.48


We conclude from our simulations that SC-FDE has low SER as compared

to OFDM in all channel conditions. Also, the use of LFDMA as a subcarrier

mapping scheme in SC-FDMA gives better SER performance when compared to

IFDMA in all channel conditions (ITU Pedestrian A, ITU Vehicular A, AWGN).

IFDMA gives lowest PAPR as compared to LFDMA and DFDMA

subcarrier mapping schemes. The use of QPSK further reduces the PAPR as

compared to 16-QAM.

We also conclude that OFDMA gives high PAPR values as compared to SC-

FDMA due to the use of multiple subcarriers.

4. SAFETY VITAL ACTIVITY AND SAFETY ENGINEERING

76

Although it is unlikely that computer equipment will be dangerous in itself,

it can be used in ways which can be a hazard to health of staff. This part of the

work provides an overview of the relevant law and risks relating to computer

health and safety and provides some guidance on avoiding problems.

4.1. Computer Health and Safety

The number of computers in the workplace has increased rapidly over the

last few years and it is now quite normal for most staff in voluntary organizations

to be exposed to computer usage. The Health and Safety at Work Act lays down

legal standards for computer equipment and requires employers to take steps to

minimise risks for all workers. Workers have received substantial damages for

injuries caused through use of computers where the employer could have foreseen

the risk but did nothing about it. The main regulations covering the use of

computer equipment include:

Health & Safety (Display Screen Equipment) Regulations

Management of Health & Safety at Work Regulations

Provision and Use of Work Equipment Regulations

Workplace (Health, Safety and Welfare) Regulations

Improving health and safety practice should be taken seriously, although it

need not take much time or expense. Measures employers should take include:

Understanding the law - make sure someone in your organization has a health

and safety brief covering all areas, not just computers.

Being aware of the health risks - the government officially recognizes some of

the risks although there are some grey areas you'll need to make up your own

mind about.

77

Assessing the risks - using procedures set out in the law - be systematic and get

help if you need it. Get a health and safety audit done by a competent

organization if necessary.

Taking steps to minimize the risks - this may only involve taking simple

measures.

Training all users to recognize the risks - if people aren't aware of the dangers

they can't take adequate precautions to protect their health.

4.2. The Risks

With the increase in computer use, a number of health and safety concerns

related to vision and body aches and pains have arisen. Many problems with

computer use are temporary and can be resolved by adopting simple corrective

action. Most problems related to computer use are completely preventable.

However it is important to seek prompt medical attention if you do experience

symptoms including:

continual or recurring discomfort

aches and pains

throbbing

tingling

numbness

burning sensation

or stiffness

Seek help even if symptoms occur when you are not working at your

computer.

Laptop computers can present particular problems due to small screens,

keyboards and inbuilt pointing devices (e.g. a small portable mouse or touchpad).

Prolonged use of laptops should be avoided. If using a laptop as a main computer

(i.e. use as a normal desktop computer in addition to use as a portable), it is

advisable to use the laptop with a docking station. This allows an ordinary mouse,

78

keyboard and monitor to be used with the laptop. The main risks associated with

using computers include:

Musculoskeletal problems

Eye strain and a greater awareness of existing eye problems

Rashes and other skin complaints have also been reported, although it is

thought these are caused by the dry atmosphere and static electricity associated

with display units rather then by the display units themselves. There are potential

risks from radiation though this is a contentious area.

4.3. Musculoskeletal problems

These can range from general aches and pains to more serious problems and

include:

Upper limb disorders such as repetitive strain injury (RSI) tenosynovitis and

carpal tunnel syndrome - by far the most important as it can quickly lead to

permanent incapacity

Back and neck pain and discomfort

Tension stress headaches and related ailments

These types of problem can be caused by:

Maintaining an unnatural or unhealthy posture while using the computer

Inadequate lower back support

Sitting in the same position for an extended period of time

An ergonomically poor workstation set up

Eye strain

Computer users can experience a number of symptoms related to vision

including:

Visual fatigue

Blurred or double vision

79

Burning and watering eyes

Headaches and frequent changes in prescription glasses

Computer work hasn't been proven to cause permanent eye damage, but the

temporary discomfort that may occur can reduce productivity, cause lost work time

and reduce job satisfaction. Eye problems are usually the result of visual fatigue or

glare from bright windows or strong light sources, light reflecting off the display

screen or poor display screen contrast.

4.4. Prevention is better than cure

Several relatively straightforward precautions can be taken by computer

users to avoid problems.

Avoiding musculoskeletal problems

General precautions to avoid musculoskeletal problems include:

Taking regular breaks from working at your computer - a few minutes at least

once an hour

Alternating work tasks

Regular stretching to relax your body

Using equipment such as footrests, wrist rests and document holders if you

need to

Keeping your mouse and keyboard at the same level

Avoiding gripping your mouse too tightly - hold the mouse lightly and click

gently

Familiarize yourself with keyboard shortcuts for applications you regularly use

(to avoid overusing the mouse)

It is also important to have your workstation set up correctly. Your

workstation includes monitor, keyboard, mouse, seating, desk, and where

80

appropriate, footrest (to enable you to put your feet flat if they would otherwise not

reach the floor), wrist rest, and document holder. Monitors should:

Swivel, tilt and elevate - if not use an adjustable stand, books or blocks adjust

the height

Be positioned so the top line of the monitor is no higher than your eyes or no

lower than 20° below the horizon of your eyes or field of vision

Be at the same level and beside the document holder if you use one

Be between 18 to 24 inches away from your face

Keyboards should:

Be detachable and adjustable (with legs to adjust angle)

Allow your forearms to be parallel to the floor without raising your elbows

Allow your wrists to be in line with your forearms so your wrists does not need

to be flexed up or down

Include enough space to rest your wrists or should include a padded detachable

wrist rest (or you can use a separate gel wrist rest which should be at least 50

mm deep)

Be placed directly in front of the monitor and at the same height as the mouse,

track ball or touch pad

Chairs should:

Support the back - and have a vertically adjustable independent back rest that

returns to its original position and has tilt adjustment to support the lower back

Allow chair height to be adjusted from a sitting position

Be adjusted so the back crease of the knee is slightly higher than the pan of the

chair (use a suitable footrest where necessary)

Be supported by a five prong caster base

Have removable and adjustable armrests

Have a contoured seat with breathable fabric and rounded edges to distribute

the weight and should be adjustable to allow the seat pan to tilt forward or back

81

Tables and desks should:

Provide sufficient leg room and preferably be height adjustable

Have enough room to support the computer equipment and space for documents

Be at least 900 mm deep

Have rounded corners and edges

Avoiding Eyestrain

Precautions that can be taken to avoid eyestrain include:

Exercising the eyes by periodically focusing on objects at varying distances

Blinking regularly

Keeping the air around you moist - for example using plants, open pans of

water or a humidifier (spider plants are said to be particularly good for this and

removing chemical vapours from the air)

Adjusting the screen height / seating so that when sitting comfortably your eyes

are in line with the top of the monitor screen

Adjusting the brightness control on your monitor for comfort

Adjusting the contrast on your monitor to make the characters distinct from the

background

Adjusting the refresh rate of your monitor to stop it flickering

Positioning monitors to avoid glare (e.g. not directly in front of windows)

Keeping your monitor the screen clean

Keeping the screen and document holder (if you use one) at the same distance

from your eyes

Servicing, repairing or replacing monitors that flicker or have inadequate clarity

Regular eye testing - do this at least once every 2 years and more frequently if

necessary - especially if you are experiencing eye problems related to using

display equipment. Indicate the distance from your eyes to the monitor to your

optician and talk to them regarding special lenses or the use of bifocals.

82

1.1 Summary for current chapter

Computers are an essential tool in the work of most organizations. Although

problems can occur through their use, with the proper equipment, ergonomic

workstation design, proper techniques and working practices, the risk of problems

can be greatly reduced. Safety engineering is one of the most important parts of the

finally work. In general every worker should learn rules of occupation and safety

engineering. Here is given an overview of the relevant law and risks relating to

computer health and safety and provides some guidance on avoiding problems.

The law places certain responsibilities firmly with the employer, however, as

individuals there are practical measures we all can and should take to avoid

harming our health.

83

CONCLUSION

The increasing demand for high speed broadband wireless access supporting

high data rate delivering capabilities for triple play (Voice, video, data) with

mobility has created an interest in the telecom circles to formulate new

technologies and architectures to offer such services at low cost and high

efficiency to the operators and end users.

With the ITU defining the requirements for 4G under the 'IMT Advanced'

tag, two technologies viz. WiMAX and 3GPP Long Term Evolution (LTE) are the

major contenders for attaining the '4G' crown. The comparative study revealed that

LTE and WiMAX are technically very alike providing similar access technologies,

radio access modes, FFT sizes, channel bandwidth, cell radius, antenna

configurations, QoS, and mobility in an All-IP network. However, in terms of

market perspective, the two technologies differ in terms of legacy and time-to-

market. WiMAX deployments have already begun throughout the world while

LTE is still in the development phase. Efforts are being made in the telecom circles

to provide seamless integration, roaming and mobility among these two

technologies and also with their legacy and non-3GPP WiFi and other wireless

access technologies.

New service providers, cable operators and non-3GPP DSL service

providers wishing to instantly deliver their customers with a mobile broadband

access may select Mobile WiMAX as their broadband wireless access system. On

the other hand, the existing 3GPP UMTS/HSPA cellular service providers may use

LTE as a convenient and natural way to upgrade their systems to the 4G standard.

For the GSM/EDGE and cdma2000 cellular service providers, either WiMAX or

LTE route can be employed to upgrade their technology while providing support

for their legacy systems. As both the WiMAX and LTE Systems have similar

technical profiles, the choice of the next- generation technology will more depend

84

on the timeline benefit of the technology and the legacy platform of the service

provider.

85

LITERATURE

[1] The report of the President the Republic of Uzbekistan Islam Karimov at

the cabinet council of Ministers devoted to the main results of 2011 and priorities

of social and economic development for 2012.

[2]Amos Edward Joel (Bell Labs), “Cellular Mobile Communication

System.”

[3]Ibikunle, F.A. 2009. “Comparative Analysis of Alternative Last Mile

Broadband Access Technologies (Wi-Fi and WiMAX)”.Pacific Journal of Science

and Technology. 10(1):280-285.

[4]. Scarfone, K., D. Dicoi, M. Sexton, and C. Tibbs. 2008. “IEEE 802.11

Wireless Networks” National Institute of Standards and Technology. White Paper.

[5] http://www.zigbee.org/

[6] Kamran Etemad.; "Overview of Mobile WiMAX Technology and

Evolution", IEEE Communications Magazine, Volume 46, No. 10, October 2008.

[7] Agilent Technologies, 3GPP Long Term Evolution: System

Overview, Product Development and Test Challenges, Application Note, literature

number 5989-8139EN, May 19, 2008.

[8]Syed Hamid Ali Shah,MudasarIqbal,TassadaqHussain“Comparison

between WiMAX and 3GPP LTE”Blekinge Institute of TechnologyAugust 2009.

[9] Moray Rumney et al., "Introducing the 3GPP LTE Downlink",

Agilent Measurement Journal, Issue 5, 2008.

[10] Mike Wolleben, "What QoS classes exists in LTE?", LTE University,

LTE FAQ. furl: http://lteuniversity. com/blogs/ltefaq/archive./2008/l l/OSAvhat-

qos-classes-exist-in- Ite.aspx)

[11] Tutorials Point, "WiMAX - Salient Features", Robust security.furl:

http:/Avww. tutorialspoint. cofnAvimaxAvimaxjsalient[features. htm)

http://lteuniversity/

http://www.zigbee.org/

86

[12] Ericsson, S3-060705, "On security algorithm selection for LTE",

3GPP TSG SA WG3 Security, SA3#45, Ashburn, USA, 31 October - 3 November,

2006.

[13] Market Intelligence Center, "The WiMAX/LTE Face-off", Industry

Intelligence Program, Communications, September 2008.

[14] Jeffrey G. Andrews, Arunabha Ghosh, RiasMuhamed, “Fundamentals

of WiMAX: Understanding Broadband Wireless Networking”, pp. 57, Prentice

Hall, 2007

[15] Jeffrey G. Andrews, ArunabhaGhosh, RiasMuhamed, “Fundamentals

of WiMAX: Understanding Broadband Wireless Networking”, pp. 338, Prentice

Hall, 2007

[16] Stefania Sesia, Issam Toufik, Matthew Baker, “LTE – The UMTS Long

Term Evolution: From Theory to Practice”, Ist ed., pp. 24, John Wiley & Sons Ltd,

2009

[17] Stefania Sesia, Issam Toufik, Matthew Baker, “LTE – The UMTS Long

Term Evolution: From Theory to Practice”, Ist ed., pp. 28, John Wiley & Sons Ltd,

2009

[18] The review of development of information and communication

technologies (IKT) in the Republic of Uzbekistan for 2006-2008.

[19] The information and analytical report «The analysis of a condition and

development prospects the Internet in Uzbekistan».

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