Investigation of the Various Applications of WiMAX Standars in Telecommunication Engineering

8/8/2019 Investigation of the Various Applications of WiMAX Standars in Telecommunication Engineering

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INVESTIGATION INTO THE APPLICATIONS OF WiMAX STANDARDS

DEPLOYED BY TELECOMMUNICATIONS SERVICE PROVIDERS IN

NIGERIA

BY

ADEWOLE ABOSEDE ABOLANLE

(TP08/09/H/2442)

A PROJECT SUBMITTED IN PARTIAL FULFILMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF

TECHNOLOGY

IN

THE DEPARTMENT OF ELECTRONICS TELECOMMUNICATION

ENGINEERING, FACULTY OF TECHNOLOGY,

OBAFEMI AWOLOWO UNIVERSITY CAMPUS


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ILE-IFE, NIGERIA

2010

ACRONYM AND ABBREVIATIONS

AAA Authentication, Authorization, and Accounting

AAS Advanced Antenna Systems

ADSL Asymmetric Digital Subscriber Loop

AES Advanced Encryption Standard

ARQ Automatic Repeat Request

ASN Access Services Network

ASP Application Service Provider

BPSK Binary Phase Shift Keying

BWA Broadband Wireless Access

CCK Complementary Coded Keying

CLEC Competitive Local Exchange Carrier

CSMA/CA Carrier Sense Multiple Access with Collision Avoidance

CSMA/CD Carrier Sense Multiple Access with Collision Detection (Ethernet)

DCF Distributed Control Function

DES Digital Encryption Standard

DS-CDMA Direct Sequence Code Division Multiple Access

DSL Digital Subscriber Line

DSSS Direct Sequence Spread Spectrum

EDCA Enhanced Distributed Control Access

ETSI European Telecommunications Standards Institute


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EV-DO Enhanced Version-Data Only (Data Optimized)

FBWA Fixed Broadband Wireless Access

FCC Federal Communications Commission

FDD Frequency Division Duplex

FDX Full Duplex

FEC Forward Error Correction

FHSS Frequency Hopping Spread Spectrum

GPRS General Packet Radio Service

GPS Global Positioning System

3GPP Third generation Partnership Project

GSM Global System for Mobile Communication

Hz Hertz

HARQ Hybrid-ARQ

HFDD- Half-Duplex Frequency Division

HIPERMAN- High-Performance Metropolitan Area Network

HSDPA- High-Speed Downlink Packet Access

HUMAN- High-speed Unlicensed Metropolitan Area Network

IEEE- Institute of Electrical and Electronic Engineers

IETF- Internet Engineering Task Force

ILEC- Incumbent Local Exchange Carrier

ISDN- Integrated Services Digital Network

ISM- Industrial, Scientific, and Medical

ITU- International Telecommunications Union

LAN- Local Area Network

LTE- Long Term Evolution

LR- Location Register

LS- Least Squares


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MAC- Media Access Control

MBS- Multicast Broadcast Service

MC- Multiple Carrier

MIMO- Multiple Input-Multiple Output

MMDS- Multi-channel Multipoint Distribution Service

MMS- Multimedia Messaging Service

MPDU- MAC Protocol Data Unit

MS - Mobile Station

NLOS - Non-Line-of-Sight

NWG - Network Working Group

OFDM - Orthogonal Frequency Division Multiplexing

OFDMA- Orthogonal Frequency Division Multiple Access

PAN- Personal Area Network

PCF- Point Control Function

PoP- Point of presence

QoS- Quality of Service

QPSK Quadrature Phase Shift Keying

RC4- Ron.s Code-4

SCDMA- Synchronous Code Division Multiple Access

SAE- System Architecture Evolution

SIM- Subscriber Identity Module

SONET- Synchronous Optical Network Interface

SSID- Service Set Identifier

STC- Space Time Coding

TDD- Time Division Duplex

TKIP- Temporal Key Integrity Protocol

UE- User Equipment


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UEA1- UMTS Encryption Algorithm 1

UEA2- UMTS Encryption Algorithm 2

UIA1- UMTS Integrity Algorithm 1

UIA2- UMTS Integrity Algorithm 2

UMTS- Universal Mobile Telecommunication System

U-NII- Unlicensed National Information Infrastructure

VoIP - Voice over IP

VPN - Virtual Private Network

WBA- Wireless Broadband Access

WCDMA Wideband Code Division Multiple Access

WEP - Wired Equivalent Privacy

Wi-Fi- Wireless Fidelity

WiMAX- Worldwide Interoperability for Microwave Access

WISP- Wireless Internet Service Provider

WLAN- Wireless Local Area Network

WMAN- Wireless Metropolitan Area Network

x-QAM x-level Quadrature Amplitude Modulation

ZF- Zero Forcing


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ABSTRACT

The world of wireless telecommunication is evolving rapidly. This thesis is on the

Investigation into the applications of WiMAX Standards deployed by telecommunications Service

Providers in Nigeria. The Broadband Wireless Access Industry that provides high-rate network

connections to fixed sites had matured to the point that it has Standards for Third-Generation (3G)

Wireless Metropolitan Area Network. The architectures are also suitable for use in a Fourth-

Generation (4G) Standard which is characterised by the support of much higher data rates that are

possible with former cellular solutions.

This work will present the emerging technologies helping wireless communication to grow

from where it was before to what it is today. It will cover the applications, characteristics and

differences of the emerging wireless technologies such as Wireless Local Area Network (WiFi-

802.11n), Wireless Personal Area Networks (ZigBee) and Wireless Metropolitan Area Networks

(WiMAX and LTE).

WiMAX (Worldwide Interoperability for Microwave Access) a set of Wireless Broadband

Standards is a Standard for Wireless Data Transmission covering a range similar to cellular phone

towers which represents a joint effort between traditional standards development, organisation and

industry. This hybrid approach had added significant value to the overall development of WiMAX

technology and services. This thesis describes the process by which WIMAX evolved, explores its

market potential and impact on the telecommunication Industry. WiMAX shows great promise as

an Internet Protocol native, high quality, high throughput, wireless pipe with greater range than

existing competing technologies.


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to as Fixed WiMAX. In December 2005, the IEEE group completed and approved IEEE

802.16e-2005, an amendment to the IEEE 802.16-2004 standard that added mobility support.

It formed the basis for WiMAX solution for nomadic and mobile applications and is often

referred to as mobile WiMAX. These standards were developed to suit a variety of

applications and deployments scenarios and hence offer a large amount of design choices for

system developers. So we could say that IEEE 802.16 is a collection of standards not one single

interoperable standard.

WiMAX technology has evolved through four stages albeit not fully distinct or clearly

sequential:

Narrowband Wireless local-loop system

First-Generation Line-of-Sight (LOS) broadband system

Third-Generation Non-Line-of-Sight broadband system and

Standard-based Wireless system.

1.2 PROBLEM STATEMENT

Despite the promise of WiMAX as an IP-base, high throughput long range fixed/mobile

wireless technology, there are serious challenges to its ultimate success which fall into three (3)

general categories;

Business plans

Real World performance and

Competition for growth in international standardization.

These problems could be base on:-

WiMAX Availability problem: Where WiMAX deployments will use licensed Radio

Frequency (RF) Spectrum positively granting them some degree of protection from

unintentional interference. It is reasonably simple however for an attacker to use

readily available tools to jam the spectrum, for all planned WiMAX deployments


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which implies that an attacker can use legacy management frames to forcibly

disconnect legitimate stations.

WiMAX Authentication Problem: A primary standard in WiMAX (802.16)

networks is that each subscriber station (SS) must have a X.509 certification that

will exclusively recognise the subscriber. Its use makes it difficult for an attacker to

spoof the identity of subscriber, adding sufficient protection against theft of service.

A basic problem in the authentication mechanism used by WiMAX is privacy and

key Management (PKM) protocol which lack in authentication of Base Station (BS)

or Service Provider. This makes WiMAX network vulnerable to man-in-the-middle

attack exposing subscribers to various confidentiality and availability attacks.

Some of this dissatisfaction surfaced with the technical performance, include range

and penetration of WiMAX. While WiMAX has been touted as a key standard for 4G

telephony, because of its potential for high quality IP streaming video in addition to high

throughput voice and data, some manufacturer clustering their support around competing

technologies such as Long Term Evolution (LTE) standards based on CDMA technology.

Finally ITU Standardization approval for WiMAX indicates that if not the backbone of

telecommunication, 4G technology is likely to be a major supported standard for WiMAX.

1.3 JUSTIFICATION FOR THE STUDY

Since we require detailed information in the form of voice, data, fax and video to be

transmitted quickly and reliably to and from anywhere at anytime, the emergence of 802.16

standards creates complete new area for innovation concerning flexible broadband

connectivity in the internet. Wide adoption of broadband wireless access and mesh

networking can eventually provide ubiquitous connectivity to the internet at anytime. Using a

simple case study of present application, we can show that connectivity to the internet in the


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world is possible without using an expensive, low bandwidth and high-latency satellite

backhaul.

1.4 AIM AND OBJECTIVES OF THE STUDY

The aim of this study is to investigate the application of WiMAX standard in while the

objectives of this study is to

i.) Compare WiMAX Standard with existing standards

ii.) Identify the WiMAX features

iii.)Determine the Problems faced by the Telecommunication industry in Nigeria.

1.5 METHODOLOGY

This thesis is not an economic analysis but a descriptive narrative means to explore the

role of WiMAX standardization in Telecommunication Engineering as a new technology and

resulting market creation and projected impacts. To conduct a thorough economic analysis of

WiMAX, is still several years too early. The lack of an available methodology for measuring

impact is also constraining factor.

1.6 LIMITATIONS

WiMAX is a great technology for next generation with potential applications such as

cellular backhaul, return trip of freight, hotspot, VoIP Mobiles and broadband connection but

it has some limitation as explained as follows:

Low bit rate over long distance: WiMAX technology offers long distance data range

which is 70 Km and high bit rate which is 70 Mbit/s that is good but both features


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does not look together when the distance is increased, the bit rate will decrease and

if the bit rate is increased, then the distance range should be reduced.

Speed connectivity: The WiMAXs other drawback is that any user closer to the

tower can get high speed which is can be up to 30Mbit/s but if a user exists at the

cell edge from the tower, such can obtain only 14Mbit/s speed.

Sharing bandwidth: In all wireless technology, the bandwidth is shared between

users in a specified radio sector. Therefore functionality could go down if more than

one user exists in a single sector, resulting to additional radio cards to be added to

the base station, to boost the capability as necessary.

WiMAX over Wi-Fi: it is easy for any one to build up a Wi-Fi network but to setup

WiMAX network is really expensive so it very hard for everyone that they pay

large amount for the setup and frequency licenses of WiMAX in any region.

WiMAX technology and different architecture: Because of low bit range on long

distance, speed of connectivity from long range and low bandwidth among users,

the different granular and dispersed network architectures are being unsupported

into WiMAX during the period of making decision about the choice of WiMAX.

1.7 APPLICATIONS

WiMAX technology applications are means by which services providers present data,

video, voice, mobile and internet access. The benefits of WiMAX technology are such as

provision of simple based prospective cost saving and service efficiency but to be capable to

allow VOIP calling, mobile devices, video making and high-speed data transfer. The basic

strength behind the WiMAX technology application are high bandwidth, high quality

services, security, deployment, full duplex including DSL versus cable and its cost.


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CHAPTER TWO

LITERATURE REVIEW

2.0 Literatures obtained were reviewed in this chapter. The overview of wireless

communication including its network concept was covered. The concept of Wi-Fi, ZigBee

and WiMAX standards in the telecommunication as the focus was also covered.

2.1 OVERVIEW OF WIRELESS COMMUNICATION.


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In telecommunications, Wireless communication is referred to as telecommunication system

such as radio transmitters and receivers, remote controls, computer networks, network terminal and

so on which uses some form of energy such radio frequency (RF), infrared light, laser light, visible

light, acoustic energy and so on to transfer information without the use of wires and cables. The

distances involved may be short, a few meters as in television remote control or long, thousands of

kilometres for radio and telemetry communication (Wikipedia). The term is often shortened to

WIRELESS. It encompasses various types of fixed, mobile and portable two-way radios, cellular

telephones, personal digital assistants (PDAs), and wireless networking. Other examples of wireless

technology include GPS units, garage openers and remote controls. Wireless operationspermits

services, such as long range communications, that are impossible or impractical to implement with

the use of wires. (Microsoft Student with Encarta Premium 2007).

2.1.1 PRINCIPLES OF WIRELESS COMMUNICATIONS

Wireless communications begin with a message that is converted into an electronic signal by

a device called a transmitter. There are two types of transmitters: analog and digital. An analog

transmitter sends electronic signals as modulated radio waves. The analog transmitter modulates the

radio wave to carry the electronic signal and then sends the modified radio signal through space. A

digital transmitter encodes electronic signals by converting messages into a binary code, the series

of zeros and ones that are the basis of all computer programming. The encoded electronic signal is

then sent as a radio wave. Devices known as receivers decode or demodulate the radio waves and

reproduce the original message over a speaker.

Wireless communications provide more flexibility than wire-based means of

communication. However, there are some drawbacks. Wireless communications are limited by the

range of the transmitter and since radio waves travel through the atmosphere they can be disturbed

by electrical interferences that cause static.

Wireless communications systems involve either one-way transmissions, in which a person

merely receives notice of a message, or two-way transmissions, such as a telephone conversation


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between two people. Two-way transmissions require both a transmitter and a receiver for sending

and receiving signals. A device that functions as both a transmitter and a receiver is called a

transceiver. Cellular radio telephones and two-way radios use transceivers, so that back-and-forth

communication between two people can be maintained.

2.1.2 MODES OF WIRELESS COMMUNICATION

Wireless communications systems have grown and changed as technology has improved.

Several different systems are used today, all of which operate on different radio frequencies. New

technologies are being developed to provide greater service and reliability (Microsoft Encarta

2007).

2.1.3 WIRELESS NETWORKS

Wireless networking (i.e. the various types of unlicensed 2.4 GHz Wi-Fi devices) is used to

meet many needs. Perhaps the most common use is to connect laptop users who travel. Another

common use is for mobile networks that connect via satellite. A wireless transmission method is a

logical choice to network a LAN segment that must frequently change locations (Understand

Telecommunications Engineering). The following situations justify the use of wireless technology:

To span a distance beyond the capabilities of typical cabling,

To provide a backup communications link in case of normal network failure,

To link portable or temporary workstations,

To overcome situations where normal cabling is difficult or financially impractical, or

To remotely connect mobile users or networks.

2.1.4 WIRELESS NETWORK TOPOLOGY

In computer networking, topology refers to the layout of connected devices. Topology is

taking to be a network's virtual shape or structure which does not necessarily correspond to the

actual physical layout of the devices on the network. For example, the computers on a


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homeLAN may be arranged in a circle in a family room, but it would be highly unlikely to find a

ring topology there.

Network topologies are categorized as below:

(i) Bus Topology

Bus networks (not to be confused with the system bus of a computer) use a common

backbone to connect all devices that is a single cable. The backbone functions as a shared

communication medium that devices attach or tap into with an interface connector. A device

wanting to communicate with another device on the network sends a broadcast message

onto the wire that all other devices see, but only the intended recipient actually accepts and

processes the message. Ethernet bus topologies are relatively easy to install and don't require

much cabling compared to the alternatives. 10Base-2 ("ThinNet") and 10Base-5

("ThickNet") both were popular Ethernet cabling options many years ago for bus topologies.

However, bus networks work best with a limited number of devices. If more than a few

dozen computers are added to a network bus, performance problems will likely result. In

addition, if the backbone cable fails, the entire network effectively becomes unusable.

(Bradley Mitchell, 1999)

(ii) Ring Topology

In a ring network, every device has exactly two neighbours for communication purposes.

All messages travel through a ring in the same direction (either "clockwise" or "counter-

clockwise"). A failure in any cable or device breaks the loop and can take down the entire

network. To implement a ring network, one typically uses FDDI, SONET, orToken

Ring technology. Ring topologies are found in some office buildings or school campuses.

(iii) Star Topology

Many home networks use the star topology. A star network features a central connection

point called a "hub" that may be a hub,switch orrouter. Devices typically connect to the

hub with Unshielded Twisted Pair (UTP) Ethernet. Compared to the bus topology, a star

network generally requires more cable, but a failure in any star network cable will only take
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down one computer's network access and not the entire LAN. (If the hub fails, however, the

entire network also fails.) (Bradley Mitchell, 1999)

(iv)Tree Topology

Tree topologies integrate multiple star topologies together onto a bus. In its simplest

form, only hub devices connect directly to the tree bus and each hub functions as the "root"

of a tree of devices. This bus/star hybrid approach supports future expandability of the

network much better than a bus (limited in the number of devices due to the broadcast traffic

it generates) or a star (limited by the number of hub connection points) alone. (Bradley

Mitchell, 1999)

(v) Mesh Topology

Mesh topologies involve the concept of routes. Unlike each of the previous topologies,

messages sent on a mesh network can take any of several possible paths from source to

destination. (Recall that even in a ring, although two cable paths exist, messages can only

travel in one direction.) SomeWANs, most notably the Internet, employ mesh routing. A

mesh network in which every device connects to every other is called a full mesh. A partial

mesh networks also exist in which some devices connect only indirectly to others. (Bradley

Mitchell, 1999)

While more complex networks can be built as hybrids of two or more of the above basic topologies.

WIRELESS NETWORK SETUP

There are basically three (3) ways to setup a wireless network,

Point-to-Point Bridges: - Since a bridge is used to connect two (2) networks. A point-to-

point bridge therefore interconnects two building having different networks. For

example, a wireless LAN bridge can interface with an Ethernet network directly to

a particular access point.

Point-to-Multiple Bridge: - This topology is used to connect three or more LANs that

may be located on different floors in a building or across buildings.
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Mesh or ad hoc network: -This network is an independent LAN that is not connected to

a wired infrastructure and in which all stations are connected directly to one

another. Since An ad hoc network is a wireless network using peer to peer

communication for network connectivity. (Ranveer Chandra, Christof Fetzer, Karin

HOgstedt)

WIRELESS TECHNOLOGIES

Wireless technologies can be classified in different ways depending on their range. Each

wireless technology is designed to serve a specific usage segment. The requirements for each usage

segment are based on a variety of variables, including Bandwidth needs, Distance and Power needs.

i.) Wireless Wide Area Network (WWAN): enables one to access the Internet via a

wireless wide area network (WWAN) access card and a laptop. It provides a very fast data

speed compared with the data rates of mobile telecommunications technology, and their

range is also extensive. Cellular and mobile networks based on CDMA and GSM are good

examples of WWAN.

ii.) Wireless Personal Area Network (WPAN): are very similar to WWAN except

their range is very limited.

iii.) Wireless Local Area Network (WLAN): enables one to access the Internet in

localized hotspots via a wireless local area network (WLAN) access card and a PDA or

laptop. It is a type of local area network that uses high-frequency radio waves rather than

wires to communicate between nodes. These networks provide a very fast data speed

compared with the data rates of mobile telecommunications technology, and their range is

very limited. Wi-Fi is the most widespread and popular example of WLAN technology.


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equipment. It offers an effective, complementary solution to wireline broadband, which has become

globally recognized by a high percentage of the population.

2.1.9 CORDLESS

The term wireless should not be confused with the term cordless which is generally

used to refer to powered electrical or electronics devices that are able to operate from a

portable power source, a battery pack without any cable or cord to limit the mobility of the

cordless device through a connection to the mains power supply.

2.2 OVERVIEW SURVEY OF EMERGING WIRELESS TECHNOLOGY

802.11n is an extension of the popular 802.11a/b/g technology known as WiFi. UWB is

standardized as IEEE 802.15.4 for low power, low-data rate applications. The technology

innovation called ZigBee make it possible to remotely monitor various types of sensors-for air-

conditioning, lighting, smoke alarms, and many more. In effect, most of these wireless technologies

are not islands in themselves, but offer some interconnectivity between each other, which help in

creating a perfectly connected environment. The various wireless network technology options are

shown in Fig. 2.1

Fig. 2.1. Types of Wireless Access.

2.2.1 Wireless Fidelity (Wi-Fi) 802.11N

WLAN


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Wi-Fi technology is most commonly found in notebook computers and internet access

devices such as routers and DSL or cable modems. A wireless LAN (WiFi) is a data transmission

system designed to provide location-independent network access between computing devices by

using radio waves rather than a cable infrastructure. Wi-Fi is meant to be used generically when

referring to any type of 802.11 network, whether 802.11b, 802.11a, 802.11g and so on. The 802.11b

networks could move data at up to 11 megabits per second (Mbps). 802.11a followed, shortly after

by 802.11g, each with maximum speeds of 54Mbps and throughput of around 25Mbps. WLAN

hardware built around 802.11g was quickly embraced by consumers and businesses seeking higher

bandwidth. The Wi-Fi speed standard, 802.11n, offers a bandwidth of around 108Mbps and it is an

industry standard, n-compliant devices will be interoperable. (Broadcom, 2006)

2.2.1.1 Characteristics of 802.11n

The emerging 802.11n specification differs from the predecessors in that it provides for a

variety of optional modes and configurations that dictate different maximum raw data rates. This

enables the standard to provide baseline performance parameters for all 802.11n devices, while

allowing manufacturers to enhance or tune capabilities to accommodate different applications and

price points. With every possible option enabled, 802.11n could offer raw data rates up to 600

Mbps. But WLAN hardware does not need to support every option to be compliant with the

standard. (Broadcom, 2006)

2.2.1.2 MAJOR COMPONENTS OF 802.11N

1) Better OFDM

In the 802.11n draft, the first requirement is to support an OFDM implementation

that improves upon the one employed in the 802.11a/g standards, using a higher maximum

code rate and slightly wider bandwidth. This change improves the highest attainable raw

data rate to 65 Mbps from 54 Mbps in the existing standards. (Broadcom, 2006)

2) MIMO Improves Performance


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One of the most widely known components of the specification is known as Multiple

Input Multiple Output, or MIMO (Broadcom, 2006). MIMO exploits a radio-wave

phenomenon called multipath. Transmitted information bounces off walls, doors, and other

objects, reaching the receiving antenna multiple times via different routes and at slightly

different times. Uncontrolled, multipath distorts the original signal, making it more difficult

to decipher and degrading Wi-Fi performance. MIMO harnesses multipath with a technique

known as space division multiplexing. The transmitting WLAN device actually splits data

stream into multiple parts, called spatial streams, and transmits each spatial stream through

separate antennas to corresponding antennas on the receiving end. The 802.11n provides for

up to four spatial streams, even though compliant hardware is not required to support that

many (Broadcom, 2006). Doubling the number of spatial streams from one to two

effectively doubles the raw data rate. There are trade-offs, however, such as increased power

consumption and to a lesser extent, cost. The specification includes a MIMO power-save

mode, which mitigates power consumption by using multiple paths only when

communication would benefit from the additional performance. The MIMO power save

mode is a required feature in the specification.

3) Improved Throughput and Higher Data Rates

Another optional mode in the 802.11n effectively doubles data rates by doubling the

width of a WLAN communications channel from 20 MHz to 40 MHz. The primary trade-off

here is fewer channels available for other devices. In the case of the 2.4-GHz band, there is

enough room for three non-overlapping 20-MHz channels. Meaning, a 40-MHz channel

does not leave much room for other devices to join the network or transmit in the same

airspace. It implies that intelligent, dynamic management is critical to ensuring that the 40-

MHz channel option improves overall WLAN performance by balancing the high-

bandwidth demands of some clients with the needs of other clients to remain connected to

the network.

2.2.1.3 Applications of 802.11n


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Because it promises far greater bandwidth, better range, and reliability, 802.11n is

advantageous in a variety of network configurations. And as emerging networked applications take

hold in the home, a growing number of consumers will come to view 802.11n not just as an

enhancement to their existing network, but also as a necessity. Some of the current and emerging

applications that are driving the need for 802.11n are listed as follows:

i. Voice over Internet Protocol (VoIP): It is realized that VOIP can save money on

long distance phone calls by using the Internet instead of traditional phone services. An

increasingly popular way to make Internet calls is with VoIP phones, which are battery-

powered handsets that typically connect to the Internet with built-in 802.11b or 802.11g.

Telephony does not demand high bandwidth, although it does require a reliable network

connection to be usable. Both 802.11b and 802.11g consume less power than 802.11n in

MIMO modes, but single-stream 802.11n may be prevalent in VoIP phones. VoIP phones

can benefit today from the increased range and reliability of a 802.11n access point.

ii. Streaming video and music: As with voice, streaming music is an application that

requires a highly reliable connection that can reach throughout the home. Growing numbers

of consumers are streaming music directly from the Internet. Though higher bandwidth is

not absolutely necessary, the additional range and reliability that 802.11n offers may be

better suited to streaming music than older generation WLAN hardware.

iii. Gaming: Gaming is an application that increasingly is making use of home WLANs,

whether users connect wirelessly to the Internet from their computers and portable gaming

devices or use the network to compete with others in the home.

iv. Network attached storage: A growing application that demands all that 802.11n has

to offer high data rates as well as range and reliability is Network-Attached Storage, or

NAS. NAS has become popular in the enterprise as an inexpensive, easy-to-install

alternative for data backup.


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v. Transferring large files such as pre-recorded TV shows from a personal video

recorder onto a notebook computer or portable media player for viewing outside the home

takes planning and patience on an older WLAN.

Fig. 2.2 compares the time it would take to transfer a 30-minute video file. At the best data transfer

rate, it would take 42 minutes to copy the file using 802.11b, and less than a minute with a two

antenna 802.11n client.

Fig. 2. 2 Time (Best case) to Transfer 30-Minute Video

2.2.2 ZIGBEE 802.15.4

ZigBee is one of the technologies that enable Wireless Personal Area Networks (WPAN).

ZigBee is the name of a specification for a suite of high level communication protocols using small,

low-power digital radios based on the IEEE 802.15.4 standard. The technology is intended to be

simpler and cheaper than other WPANs such as Bluetooth. ZigBee protocols are intended for use in

embedded applications requiring low data rates and low power consumption. WPAN implies a

reach of only a few meters, 9.5m in the case of ZigBee, the network will have several layers, so

designed as to enable intrapersonal communication within the network, connection to a network of

higher level and ultimately an uplink to the Web.

The ZigBee Standard has evolved standardized sets of solutions, called layers' (P. Kinney,

2003). These layers facilitate the features that make ZigBee very attractive, low cost, easy

implementation, reliable data transfer, short-range operations, very low power consumption and

adequate security features.

802.11n

802.11g

802.11b


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i. Network and Application Support layer:The network layer has been designed to allowthe network to spatially grow without requiring high power transmitters. The network

layer also handle large amounts of nodes with relatively low latencies.

ii. Physical layer: The IEEE 802.15.4 physical layer accommodates high levels of

integration by using direct sequence to permit simplicity in the analog circuitry and enable

cheaper implementations.

iii. Media access control layer: The IEEE 802.15.4 Media Access Control (MAC) layer

permits the use of several topologies without introducing complexity and is meant to work

with large numbers of devices.

Fig.2.3 IEEE 802.15.4 / ZigBee Stack Architecture

2.2.2.1 CHARACTERISTICS OF ZIGBEE

ZigBee is poised to become the global control/sensor network standard. It has been designed

to provide the following features: (TG4)

1) Low power consumption, with battery life ranging from months to years.

2) Maximum data rates allowed for each of the frequency bands are fixed as 250kbps

@2.4GHz, 40kbps @ 915MHz, and 20kbps @868MHz.

3) High throughput and low latency for low duty-cycle applications (


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5) Addressing space of up to 64 bit IEEE address devices, 65,535 networks.

6) 70-100m range.

7) ZigBees simplicity allows for inherent configuration and redundancy of network devices

provides low maintenance. It has low cost (device, installation, maintenance).

8) High density of nodes per network: ZigBees use of the IEEE 802.15.4 PHY and MAC

allows networks to handle any number of devices. This attribute is critical for massive

sensor arrays and control networks.

9) Fully reliable hand-shake data transfer protocols.

10) Different topologies like: star, peer-to-peer and mesh

2.2.2.2 APPLICATIONS OF ZIGBEE

ZigBee networks consist of multiple traffic types with their own unique characteristics,

including periodic data, intermittent data, and repetitive low latency data. The characteristics of

each are as follows:

Periodic data usually defined by the application such as a wireless sensor or meter. Data

typically is handled using a beaconing system whereby the sensor activates at a set time and

checks for the beacon, exchanges data, and switches off.

Intermittent data either application or external stimulus defined such as a wireless light

switch. Data can be handled in a beaconless system or disconnected. In disconnected

operation, the device will only attach to the network when communication is required, saving

significant energy.

Repetitive low latency data uses time slot allocations such as a security system. These

applications may use the guaranteed time slot (GTS) capability. GTS is a method of QoS that

allows each device a specific duration of time as defined by the PAN coordinator in the Super-

frame to do whatever it requires without contention or latency. In all applications, the smaller

packet sizes of ZigBee devices results in higher effective throughput values compared to other

standards. ZigBee networks are primarily intended for low duty cycle sensor networks (


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2.2.3 WiMAX

Worldwide Interoperability for Microwave Access (WiMAX) is currently one of the hottest

technologies in wireless. The Institute of Electrical and Electronics Engineers (IEEE) 802

committee, which sets networking standards such as Ethernet (802.3) and Wi-Fi (802.11), has

published a set of standards that define WiMAX. IEEE 802.16-2004 (also known as Revision D)

was published in 2004 for fixed applications; 802.16 Revision E (which adds mobility) is publicised

in July 2005. The WiMAX Forum is an industry body formed to promote the IEEE 802.16 standard

and perform interoperability testing. The WiMAX Forum has adopted certain profiles based on the

802.16 standards for interoperability testing and WiMAX certification. These operate in the

2.5GHz, 3.5GHz and 5.8GHz frequency bands, which typically are licensed by various government

authorities. WiMAX, is based on an RF technology called Orthogonal Frequency Division

Multiplexing (OFDM), which is a very effective means of transferring data when carriers of width

of 5MHz or greater can be used. Below 5MHz carrier width, current CDMA based 3G systems are

comparable to OFDM in terms of performance.

WiMAX is a standard-based wireless technology that provides high throughput broadband

connections over long distance. WiMAX can be used for a number of applications, including last

mile broadband connections, hotspots and high-speed connectivity for business customers. It

provides wireless metropolitan area network (MAN) connectivity at speeds up to 70 Mbps and the

WiMAX base station on the average can cover up to 5 to 10 km. The WiMAX Overview is given in

Figure 2.4 (Sanida Omerovic, 2008) and table 1 give the differentiation between the Fixed and

Mobile WiMAX.

Figure 2.4. WiMAX Overview (Sanida Omerovic, 2008)


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Fixed or mobile WiMAX

Fixed WiMAX Mobile WiMAX

Standard 802.16-2004 802.16e-2005

Access Fixed Fixed, portable and mobile

Modulation and

duplexing

OFDM TDD, FDD SOFDMA TDD, possibly FDD

Handoffs No Yes

Service providers

targeted

DSL and cable modem

service providers,

wireless and wired ISPs

Mobile operators, DSL and cable

modem service providers, wireless and

wired ISPs

Subscriber unit Outdoor or indoor CPE,

eventually PCMCIA

card

Indoor CPE, PCMCIA card, mini-card

built in laptops, mobile devices, phones

Spectrum bands 3.5 GHz, 5.8 GHz 2.3-2.4 GHz, 2.5-2.7 GHz, 3.3-3.4 GHz,

3.4-3.8 GHz

Certified products January 2006 2007

Table 2.1. Comparison of Fixed and mobile WiMAX (Monica Paolini, 2006)

2.2.3.1 CONCEPT OF WIMAX

WiMAX, or Worldwide Interoperability for Microwave Access, is a form of broadband

wireless access which is based on the IEEE 802.16 standard for wireless metropolitan-area

networks (MANs). Unlike many technologies in the broadband wireless access domain that provide

only line of sight (LOS) coverage, the technology behind WiMAX has been optimized to provide

excellent non line of sight (NLOS) coverage. As a result, WiMAX products are able to support

downlink data rates of 65 Mbits/s at close range to 16 Mbits/s at distances of 9 to 10 km, which is

enough bandwidth and transmission range to deliver high-speed simultaneous access to voice, data,

and video services (multimedia) to hundreds of businesses or thousands of residences. (Darcy

Poulin, 2005, SR Telecom Inc., 2004, C. Eklund et al., 2002).

WiMAX is able to overcome the impediments found in NLOS propagation and deliver such

high speed access using the following technologies and techniques:

OFDM technology.


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Sub-Channelization.

Directional antennas.

Transmit and receive diversity.

Adaptive modulation.

Error correction techniques.

Power control.

1.) Orthogonal Frequency Division Multiplexing (OFDM)

OFDM is a multi-carrier transmission technology that provides superior means of

transmitting wireless information in high multi-path environments in 2-11 GHz frequency range.

OFDM works by dividing the data stream into several parallel bit streams. Each bit stream is

carried by a separate subcarrier and all subcarriers transmit in unison and simultaneously. Figure

2.4 depicts exactly how OFDM works in WiMAX. (C. Y. Wong et al, 1999)

Fig.2.5 OFDM Technology

Advantages of OFDM: (Z. Shen, J. G. Andrews, and B. L. Evans, 2003)

i. Multi-carrier multiplexing and transmission technique

ii. Achieves high spectral efficiency and data rates

iii. Has high resilience to RF interference

iv. Eliminates multi-path distortion effectively

v. Minimizes frequency selective fading (FSF)

vi. Eliminates Inter Symbol Interference (ISI)

2.) Sub-Channelization


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WiMAX supports sub-channelization which means that instead of transmitting on all

192 data subcarriers, one can transmit on just a subset. As a result, the system achieves greater

range by using the same amount of power over fewer carriers. Since the power limitation in the

CPE, balancing the power in the uplink and downlink can be done by concentrating the power

over fewer subcarriers in the uplink (Darcy Poulin, 2005). The mechanism of Sub-channelization

is very well depicted in the figure below;

Figure 2.6 The Effect of Sub-channelization.

3.) DIRECTIONAL ANTENNAS

The effectiveness of using directional antennas over omni-directional antennas have

been proven and successfully deployed in several systems that operate under significant NLOS

fading. This is due to several advantages found in directional antennas.

Advantages of Directional Antennas

i. Increase of link availability compared to omni-directional antennas

ii. Decrease of the delay spread at both the Base Station and the CPE

iii. Suppression of any multi-path signals that arrive in the side-lobes and back-lobes.

4.) TRANSMIT AND RECEIVE DIVERSITY

Diversity schemes are used to take advantage of multi-path and reflections signals

that occur in NLOS conditions. In transmit diversity, several antennas are placed at the transmitter

side with a separation between them that guarantees independent fading between the transmitted

signals across the wireless channel. This reduces the fade margin requirement and combats

interference. The same scheme applies for receive diversity where several antennas are placed at


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the receiver side instead of being placed at the transmitter side which helps in overcome fading

and reduce pathloss (Alamouti, S. M., 1998).

5.) ADAPTIVE MODULATION

Adaptive modulation allows the WiMAX system to adjust the signal modulation

scheme depending on the signal to noise ratio (SNR) condition of the radio link. The highest

modulation scheme is used when the radio link is high in quality. This gives more capacity for the

system. During a deep signal fade, the WiMAX system can transfer to a lower modulation scheme

to maintain the connection quality and link stability. This feature allows the system to overcome

time-selective fading. The main feature of adaptive modulation is that it allows one to transmit at

higher data rates during best case conditions as opposed to having a fixed scheme which transmits

always at low data rates to account for the worst case conditions. As illustrated in fig. 2.6

Figure 2.7 Relative Cell Radii for Adaptive Modulation

6.) ERROR CORRECTION TECHNIQUES

WiMAX utilizes several error correction techniques in its receiver structure to reduce the signal to

noise ratio requirements and significantly improve the bit error rate (BER) performance of the

system. These techniques, such as the Strong Reed Solomon FEC and convolution coding, are

used to recover frames in error which may have been lost due to deep fades in the channel (] D.

M. Mandelbaum, 1974, S. Lin and P. Yu., 1982)

7.) POWER CONTROL

WiMAX incorporates several power control algorithms to reduce the overall power consumption

of the CPE, thus decreasing potential interference with other co-located units. This improves the

overall performance of the system dramatically. It is implemented by the base station sending

power control information to each of the CPEs to regulate the transmit power level to a fixed


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threshold. Concerning a LOS system, the transmit power of the CPE is approximately

proportional to its distance from the base station. However in the NLOS system, this level

depends on many other factors such as the obstructions lying in the path between the CPE and the

base station.

After presenting a general introduction about the WiMAX wireless system and shedding

light on its different attributes, there is need to discuss the physical properties of the

electromagnetic waves which are the main carriers of data in wireless communication systems.

2.2.3.2 CHARACTERISTICS OF WIMAX

Technical aspects of 802.16a that are instrumental in powering robust performance include

the following characteristics:

Power varies with band, Profiles from 100 Mw up to 2W.

Configuration is P-P and P-MP Cellular.

Spectrum initially 3.5 GHz licensed and 5.8 GHz unlicensed bands.

Radio interface is OFDM, using 256 tones.

Access Protocols is downstream - TDM (Broadcast), upstream - TDMA with access

contention.

Security via station authentication and encryption.

Data rates variable with channel bandwidth 3.5 MHz in 3.5 GHz band, 20 MHz in 5.8 GHz

band.

Actual realizable data rates are ~ 2b/Hz.

Maximum range ~2Km for indoor Non-LOS cellular service at 3.5 GHz.

2.2.3.3 Applications of WiMAX


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WiMAX will allow people to go from their homes to their cars, and then travel to their

offices or anywhere in the world, all seamlessly. WiMAX can serve the business, residential and

mobile segments. The applications in these areas are listed as follows:

Residential users

Basic voice services, low cost domestic & international calls

Basic (dialup speed) to advanced (over 1Mbps)

Bundled voice and data services

Business users

Basic data connectivity for small businesses

Advanced data services to medium and large businesses

Feature-rich, low cost voice services (VoIP)

Mobile users (mobile WiMAX only)

Data connectivity for mobile workforce

Data connectivity for international visitors

2.2.3.4 WIMAX WORKING PRINCIPLE

WiMAX make possible the broadband access to conservative cable or DSL lines. The working

method of WiMAX is little different from Wifi network, because Wifi computer can be connected via

LAN card, router, or hotspot, while the connectivity of WiMAX network constitutes of two parts in

which one is WiMAXTower or booster also known as WiMAX base station and second is WiMAX

receiver (WiMAX CPE) or Customer Premise Equipment.

Figure 2.8 WiMAX Working Principle (How stuff works)


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The WiMAX network is just like a cell phone, where a user send data from a subscribers device

to a base station, the wireless signal is broadcasted into channel known as uplink by the base station.

The base station transmits to the same or another user known as downlink. The WiMAX base station

has higher broadcasting power, antennas and enhanced additional algorithms. WiMAX technology

providers build a network with the help of towers that enable communication access over many miles.

The broadband service of WiMAX technology is available in coverage areas. The coverage areas of

WiMAX technology separated in series of over lied areas called channel.

The orthogonal frequency division multiplexed access (OFDMA) in WiMAX technology, is a

great technique used to professionally take advantage from the frequency bands. The transmission

frequencies of WiMAX technology from 2.3MHz to 3.5 GHz make it low price wireless network. Each

spectral profile of WiMAX technology may need different hardware infrastructure. Each spectrum

contain its bandwidth profile which resolved channel bandwidth. The bandwidth signal is separated in

OFDMA (Orthogonal Frequency Division Multiplexed Access) is used to carry data called sub carrier.

Transmitted data is divided into numerous data stream where every one belongs to another sub carrier

and then transmitted at the same broadcast interval. At the downlink path the base station broadcast the

data for different user professionally over uninterrupted sub-carriers.

The independency of data is a great feature ofOFDMA (Orthogonal Frequency Division

Multiplexed Access) that prohibit interfering and is been multiplexed. It also makes possible power

prioritization for various sub carriers according to the link quality. The sub carrier having good quality

carry more data since the bandwidth is narrow. But those that have low quality carry nun data.

WiMAX is providing quality of service (WiMAX QoS) which enables high quality of data like

VoIP or TV broadcasts. The data communication protocol from base station is an alternative of quality

of service (WiMAX QoS) application and offers video streaming. This type of data is translated into

parameters or sub carriers per user. All type of technique is carrying out together to speed up coverage,

bandwidth, efficiency and number of users. The base station of WiMAX has ability to cover up 50 Km.

WiMAX technology supports various protocols such as VLAN, ATM, IPv4 Ethernet etc.
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2.2.4 LONG TERM EVOLUTION (LTE)

The LTE evolves from the Third-Generation technology which is based on Wideband Code

Division Multiple Access (WCDMA) and defines the LTE of the 3-GPP UMTS/HSPA cellular

technology. The specifications of these efforts are formally known as the Evolved UMTS

Terrestrial Radio Access (E-UTRA) and Evolved UMTS Terrestrial Radio Access Network (E-

UTRAN), commonly referred to by the 3-GPP Project LTE. The first version of LTE is documented

in Release 8 of the 3-GPP specifications. It defines a new physical layer radio access technology

based on Orthogonal Frequency Division Multiple Access (OFDMA) for downlink, Similar in

concept to the PHY layer of Mobile WiMAX and uses Single carrier FDMA (SC-FDMA) for the

uplink.

LTE supports high performance mobile access functional up to 350 Km/h with 500Km/h

under consideration peak data rates range from 100 to 326.4 Mbps on the downlink and 50 to 86.4

Mbps on the uplink depending on the antenna configuration and modulation depth. The LTE target

is to achieve the data rates set by the 4G IMT-Advanced standard. The development of the LTE

interface is linked closely with the 3GPP system architecture evolution (SAE) which defines the

overall system architecture and Evolved Packet Core (EPC). The LTE aim is to provide an all IP

backbone with reduction in cost per bit, better service provisioning, flexibilyt in user of new and

existing frequency bands, simple network architecture with open interfaces and lower power

consumption.

2.3 ELECTROMAGNETIC WAVE PROPAGATION

In wireless communications, the information that is transmitted propagates in the form of

electromagnetic (EM) waves. The amplitude, phase, or frequency (wavelength) of a wave can all be

modified to represent the information. As a result, it is very fundamental to understand EM waves

and how information is propagated from one place to another in order determine the performance of

a wireless link (Anderson, Harry R., 2003).


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2.3.1 FREE SPACE PROPAGATION

Free-space transmission is a principal consideration in basically all fixed broadband wireless

communication systems. Although free space primarily means in vacuum, it can be practically

implemented in short-range space-wave paths between elevated terminals. In free space, the signal

gets attenuated as it travels from the transmitter to the receiver.

This attenuation factor is characterized by the free space pathloss given by:

2

4

===

rGTGR

PP

PLFathlossFreespacepT

R

(Anderson, Harry R., 2003)

The free space pathloss is characterized by the following:

i. Inversely proportional to square the distance

ii. Proportional to the wave length ()

Proportional to the antenna gains (GT and GR)

However, free space propagation alone cannot depict what will exactly happen to the signal

as it travels from the transmitter to the receiver as there are many effects that can substantially

impact the communication link performance (Anderson, Harry R., 2003).

2.3.2 REFLECTION

Reflection is one of the most important wave propagation phenomena involved in almost

every type of fixed wireless systems (Anderson, Harry R., 2003)

There are two basic reflection types:

i. Specular reflection from smooth surfaces.

ii. Reflections (scattering) from rough surfaces.

2.3.2.1 SPECULAR REFLECTION


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This occurs when a signal intersects the ground, a wall or any other surface that that does

not have any edges or discontinuities. Reflection takes place on the specular point where the

angle of incidence of the transmitted wave equals the angle of reflection of the reflected wave,

(Anderson, Harry R., 2003) as illustrated in fig.2.7

Pi Pr

( )

Fig. 2.9 Two dimensional geometry showing specular reflection (Anderson, Harry R., 2003)

2.3.2.2 REFLECTIONS FROM ROUGH SURFACES

In the real world, seldom do we encounter reflections along a smooth surface. However,

most of the times, we encounter surfaces that have random variations as in the earths surface or

have systematic variations such as in the walls and roofs of artificial structures. In severe scenarios,

the surface may appear to be a pure scatterer. The degree of roughness is given by the Rayliegh

criterion:0

sin8 yhR

(Anderson, Harry R., 2003)

where hR is the difference in the maximum and minimum surface variations; y0 is the angle between

the incident ray and the surface as illustrated in fig. 2.8

Fig. 2.10 Reflection and Scattering from a rough surface

GroundSpecular

Reflection


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2.3.3 DIFFRACTION

Diffraction is an important wave propagation mechanism which can occur to any

propagating wave in wireless communications. Diffraction only happens when an object partially

blocks the path of a propagating wave. Since our environment deals with a non-line of sight

scenario, we will be heavily relying on diffraction in our study, there are typically two models used

in a wireless system design to model diffraction (Anderson, Harry R., 2003)

2.3.3.1 WEDGE DIFFRACTION

It occurs at the corner of buildings, at the edge of walls where they intersect roofs, and at the

junction of walls with the ground or street and it is considered very important features. The wedge

diffraction scheme is used to find the diffraction attenuation for an obstructed interference path over

a rooftop edge or the parapet of a building but it is highly computational (Anderson, Harry R.,

2003).

2.3.3.2 KNIFE-EDGE DIFFRACTION

It is a special case of the wedge diffraction that is when the interior angle of the wedge is

assumed to be zero. Because of its resulting simplicity and speed of calculation efficiency, knife-

edge diffraction is used in many propagation models. The knife-edge diffraction scheme is used as a

model for many obstructed path circumstances including paths with terrain obstructions such as

gently rolling hills that have very little resemblance to a knife-edge (Anderson, Harry R., 2003).

2.3.4 FRESNEL ZONE AND PATH CLEARANCE

A crucial design objective in a fixed wireless design is to achieve adequate path clearance

for the link, which means that any point along the path between the transmitter and the receiver

should have a certain distance from any obstacle along the path.


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As a result, a wireless link could fall to one of three categories, which are determined by the

obstacles positions with respect to the Fresnel zone. Fresnel zone is the locus of the points where

the diffracted path length is multiples of 180 degrees different from the direct path length. As

shown in Figure 2.9, the fresnel zones form elliptically shaped solids of revolution around the

transmit-receive propagation path. In concept, the first fresnel zone is the zone where the significant

power is transmitted, meaning that the power available at the receiver will be diminished if the first

fresnel zone is significantly obstructed or blocked. A general criterion for link system design is to

set the path clearance so that a radius equal to 60% of the first fresnel zone is unobstructed. This is

so called the 0.6 first fresnel zone criterion (Anderson, Harry R., 2003, Erceg, V. et al.).

The first fresnel zone with the 0.6 criterion is depicted in the Fig. 2.9 (a)

Fig. 2.11 (a)RF Propagation and Fresnel Zone (Mirza M Wahaj, 2004)

2.4 LINE OF SIGHT (LOS)

Fig. 2.11b LOS (Line of Sight) Demonstration

LOS Attributes:

Requires 60% Fresnel (1st) zone clearance

Diffraction losses are negligible

Free space signal attenuation determines coverage


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2.5 OLOS (OBSTRUCTED LINE OF SIGHT)

Figure 2.12. OLOS demonstration

OLOS Attributes :

Fresnel zone obstruction- above the 60% mark

Diffraction Losses are from 0-6dB

Requires higher tower heights

Seasonal effects due to the nature of the obstruction

2.6 NLOS (NON LINE OF SIGHT)

Figure 2.13 NLOS demonstration (Mirza M Wahaj, 2004)

NLOS Attributes:

More propagation loss

Higher delay spread

Higher ISI (Inter Symbol Interference)

Pronounced multipath distortion

Higher Tx power required to meet SNR/BER limits


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2.7 COMPARISON OF EMERGING WIRELESS TECHNOLOGIES

The use of wireless technologies is beginning to appear similar to the initial

development of the railways. Each technology seems to have a different gauge and

compatibility issues seem to confuse the novice. The main points of comparison of Wi-Fi,

ZigBee and WiMAX are listed in table 2.2 while the key highlights of the comparison between

the two next generation broadband wireless access technologies: 3GPP LTE and WiMAX

IEEE 802.16e is presented in Table 2.3

Table 2.2 Comparison of Emerging Wireless Technologies (Bhavneet Sidhu, Hardeep Singh, and Amit

Chhabra)

Technology WiFi -802.11n ZigBee WiMAX

Application Wireless LAN Internet Sensor Networks Metro Area Broadband

Internet connectivity

Typical Range 100m 70-100m 50 km

Frequency Range 2.4 GHz 2.4 GHz 2-11GHz

Data Rate 108 - 600Mbps 250Kbps 75Mbps

Modulation DSSS DSSS QAM

Network IP & P2P Mesh IP

IT Network

Connectivity

Yes No Yes

Network Topology Infrastructure (Ad-hoc also possible) Ad-hoc Infrastructure

Access Protocol CSMA/CA CSMA/CA Request/Grant

Key Attributes Wider Bandwidth, Flexibility Cost, Power Throughput, Coverage


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Table 2.3 Highlights of LTE and WiMAX comparison

Aspect 3GPP LTE Mobile WiMAX IEEE 802.16eLegacy GSM/GPRS/EDGE/UMTS/HSPA IEEE 802.16 a through d

Core Network UTRAn moving towards ALL-IP,

Evolved-UTRA (EUTRA) core

network with IMS with Sae

Architecture

WiMAX Forum All-IP Network

Access Technology:

Downlink (DL)

Uplink (UL) OFDMA

SC-FDMA

OFDMA

OFDMA

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

Radio Access

modes

TDD and FDD TDD and FDD

Frequency Band Existing (800, 900, 1800, 1900

MHz) and new Frequency

bands (Range 800 MHz 2.62

GHz)

NLOS 2 11 GHz

Peak date rate

DL

UL 100 to 326.4 Mbps

50 to 86.4 Mbps

75 Mbps

25 Mbps

Channel

bandwidth

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

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

~ 8.4 Km for 5 to 10 MHz BW

Cell capacity >200 Users at 8 MHz

>400 Users for larger BW

100 200 Users


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Mobility:

Speed

Handover Up to 350 Km/h

Inter-cell soft handovers supported

Up to 120 Km/h

Optimised hard handovers

supported

Antenna Scheme

DL

UL

MIMO

2 Tx X 2 Rx

2 Tx X 2 Rx

MIMO

2 Tx X 2 Rx

1 Tx X NRx (collaborative)

Number of Code

words

2 1

Roaming New Auto through existing

GSM/UMTS

Security

Algorithms

UEA1, U1A1, UEA2 (Snow

Algorithms supporting 256 bits

of keys) and U1A2

PKMV1 RSA, HMAC, AES-

CCM and PKMV2-EAP,

CMAC, AES-CTR, MBS

Security


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CHAPTER THREE

WIMAX STANDARD PRINCIPLES

3.0 The following is the investigative methodologies that would be use for this work;

Study and investigation of the technical features of WiMAX network

Investigate the requirement for the deployment of the WiMAX Networks.

Investigate the basic security requirement for the WiMAX technology.

Discuss about the security functions of WiMAX technology.

Study the recent developments in the WiMAX technology security.


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3.1 TECHNICAL FEATURES OF WIMAX NETWORK

WiMAX is a great invention in wireless technology providing 70Km broadband access to

mobile users. WiMAX technology is based on IEEE 802.16 Standard and it is a

telecommunication protocol offering full access to mobile internet across cities and countries with a

wide range of devices. WiMAX technology has salient features namely:

3.1.1 WiMAX support multipath

WiMAX technology is offering OFDM-basedphysical layer which is based on orthogonal

frequency distribution. The WiMAX technology provides confrontation to multipath. Due to its

good architecture it allows the user to operate in NLOS conditions. Now WiMAX is familiar as a

technique of multi path for wireless network.

3.1.2 WiMAX broadband access

WiMAX technology is offering very high speed broadband access to mobile internet. When

using 20MHz, the data rate can be high up to 74Mbps. Generally 10MHz with the TDD scheme

provides 3:1 up and down link ratio. WiMAX providing very good signals therefore higher data

rates can be achieved with multiple antennas. Antennas are used for beam forming, space time

coding and so on.

WiMAX offer high speed data rate

Higher speed data rates are offered by the scalable architecture of physical layer. WiMAX

technology provides easy scaling of data with possible bandwidth of channel. If the bandwidth of

channels may be from 1.25MHz to 10MHz then a system can use 128, 512, 1024, 2048 bit FFTs

which provide dynamically roaming across numerous networks having dissimilar bandwidth.

3.1.4 WiMAX offer modulation and error correction

The use ofWiMAX technology increased rapidly because it supports lots of modulation and

error correction facilities to users. It also allows a user to change the scheme according to channel
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condition. AdaptiveModulation and Coding (AMC) is a valuable method to exploit throughput in a

varying channel.

3.1.5 WiMAX support reliability of data

Automatic retransmission of data supported by WiMAX at data link layer for links is a great

feature. It does not only improve reliability but also enabled ARQ which necessitates each

broadcast packet to be recognized by the receiver, and if any unacknowledged data packets are

unspecified, to be misplaced and retransmitted.

3.1.6 WiMAX support TDD and FDD

WiMAX technology supportsTime Division Duplexing (TDD) and Frequency Division

Duplexing (FDD). They both offer low cost system accomplishments.

3.1.7 WiMAX TDM scheme

The WiMAX technology holds all systems therefore any data may be in form of uplink or

downlink, checked by scheduler from the base station. The total capacities are shared between

several users according to their demand. And it is done by WiMAX Time Division

Multiplexing (TDM) scheme.

3.1.8 WiMAX MAC layer

The architecture of WiMAX technology based on MAC layer is a connection oriented layer.

Through MAC layer a user can perform a variety of functions such as voice including multimedia.

It supports best efforts for data traffic as bit, real time, traffic flows and so on. The aim of WiMAX

technology design is to facilitate large number of users with variety of connections per terminal.

3.1.9 WiMAX strong encryption

WiMAX technology also facilitates the user with strong encryption, using Advanced

Encryption standard (AES). A user can get strong privacy and administration. The EAP
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protocol offer flexible authentication architecture which enable a user to get access to username,

password, certificates, and smart card.

3.1.10 WiMAX mobility

The basic and most important feature of WiMAX technology is to support mobility

applications as VoIP. The power saving mechanism of WiMAX technology is used to extend the

battery life of handheld devices. It supports mobile applications including channel estimation, sub-

channelization, power control and so on.

To get access to WiMAX base station is not a huge task now because the wide range of

connectivity of WiMAX provides access to base station from home. Installation of hardware is very

easy with WiMAX technology. With the growth of WiMAX technology there are more feature

coming up.

3.2 TYPES OF WIMAX TECHNOLOGY (802.16)

The WiMAX family of standards (802.16) concentrate on two types of usage models; fixed

WiMAX usage model and mobile WiMAX usage model. The basic element that differentiates

these systems is the ground speed at which the systems are designed to manage. Based on mobility,

wireless access systems are designed to operate on the move without any disruption of service;

wireless access can be divided into three classes; stationary, pedestrian and vehicular. A mobile

WiMAX network access system is one that can address the vehicular class, whereas the fixed

WiMAX serves the stationary and pedestrian classes. While the nomadic wireless access system is

referred to as a system that works as a fixed WiMAX network access system but can change its

location.

Fixed WiMAX: Broadband service and consumer usage of fixed WiMAX access is

expected to reflect that of fixed wire-line service, with many of the standards-based requirements

being confined to the air interface. Because communications takes place via wireless links

from WiMAX Customer Premise Equipment (WiMAX CPE) to a remote Non Line-of-sight
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(NLOS) WiMAX base station, requirements for link security are greater than those needed for a

wireless service. The security mechanisms within the IEEE 802.16 standards are sufficient for fixed

WiMAX access service.

Another challenge for the fixed WiMAX access air interface is the need to set up high

performance radio links capable of data rates comparable to wired broadband services, using

equipment that can be self installed indoors by users, as is the case for Digital Subscriber Line

(DSL) and cable modems. IEEE802.16 standards provide advanced physical (PHY) layer

techniques to achieve link margins capable of supporting high throughput in NLOS environments.

Mobile WiMAX: The 802.16a extension, refined in January 2003, uses a lower frequency

of 2 to 11 GHz, enabling NLOS connections to be made. The 802.16e task group was capitalized on

the capabilities that this provided by working on developing a specification to enable mobile

WiMAXclients. These clients were able to hand off between WiMAX base stations, enabling users

to roam between service areas.

WiMAX backhaul: It is actually a connection system from the Access Point (AP) back to

the provider and to the connection from the provider to the network. A WiMAX backhaulcan set

out any technology and media provided. It connects the system to the backbone. In most of the

WiMAX deployments situation, it is possible to connect several WiMAX base stations by using

high speed WiMAX backhaul microware links thereby allowing roaming between WiMAX

subscribers within or outside base stations. This is similar to roaming enabled by cellular phone

companies.

There can be two cases of portability namely, full mobility or limited mobility. The

effortless case of portable service involves a user transporting a WiMAX modem to a different

location. Provided this visited location is served by wireless broadband service, in this scenario the

user re-authenticates and manually re-establishes new IP connections. Broadband service at the

visited location is afforded. In the fully mobile scenario, user expectations for connectivity are

comparable to facilities available in third generation (3G) voice/data systems. Users may move
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around while engaging in a broadband data access or multimedia streaming session. Mobile

wireless systems need to be robust against rapid channel variations to support vehicular speeds.

There are significant implications of mobility on the IP layer owing to the need to maintain

rout-ability of the host IP address to preserve in-flight packets during IP handoff. This may require

authentication and handoffs for uplink and downlink IP packets and Medium Access Control

(MAC) frames. The need to support low latency and low packet loss handovers of data streams as

users transition from one base station to another is clearly a challenging task. For mobile data

services, users will not easily adapt their service expectations because of environmental limitations

that are technically but not directly relevant to the mode of use. For these reasons, the network and

air interface must be designed to anticipate these users expectations and deliver accordingly.

3.3.0 WIMAX DEPLOYMENTS

WiMAX Technology is a great development in wireless technology offering long distance

broadband access. After viewing the rapid growth of WiMAX technology in large business

companies, multimedia project software and hardware manufacturers started to develop and test the

compulsory components to deploy WiMAX Technology network.

In 2004, cables and DSL technologies used to fetch wireless broadband access to rural areas

advanced quickly and in 2009 WiMAX technology has widely spread to everywhere. Fixed

WiMAX technology was introduced in 2008. The rapid developments of both WiMAX

technologies are rolling out now. The WiMAX Technology will take over the mobile industries.

The WiMAX deployment skill set to overcome the digital divide because of easiness and efficiency.

Along with traditional factors such as link budgets and signal-to-noise ratio (SNR), deployment

considerations for WiMAX systems should include the cost saving opportunities offered by the

802.16 standard.

3.3.1 Designing a WiMAX Network: A wide variety of technical points need to be addressed

when designing WiMAX networks. A significant consideration is the efficiency, cost and
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performance involved in providing coverage and capacity, while avoiding the build-out of a large

number of new cell sites. The first item to be considered is the link budget, the loss and gain sum of

signal strength through the varying medium of the transmission path. The link budget determines

the maximum cell radius for an adequate service-level agreement (SLA). Additionally a good SNR

is critical for the system to perform at the optimum level. The ability to scale while maintaining

constant symbol duration provides more flexibility in equipment components. Most importantly,

operators can deploy systems today and develop system bandwidth in the future at lower cost

without impact to earlier deployments.

3.3.2 Environmental Factors: Wireless design criteria vary across four types of environments:

i. Dense Urban: A city centred with many businesses and high-density residential units

represents a challenge due to multipath effects among the multi-story buildings.

ii. Urban: Surrounding a city center, average building heights may be lower than the

mast of a base station, but the propagation environment remains equally challenging.

iii. Suburban: With lower-density housing (primarily single-family dwellings) and fewer

businesses, average building heights are much lower than base station towers and

structures are more spread out, thus creating a more favourable propagation

environment.

iv. Rural: Where homes are far apart and businesses widely scattered, this environment

offers no obstruction to wireless propagation so long as the terrain is flat.

3.3.3 Determining Coverage Boundaries: To take full advantage of WiMAX scalability, system

operators need to use the right software tools to predetermine coverage boundaries. These tools

perform propagation simulations and drive tests. Careful deployment planning is critical in order to

have room to scale, anticipating growing customer demands while ensuring a quality user

experience. This planning is important in urban areas, where deployments are most likely to be

driven by capacity requirements.


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3.3.4 Sector and Frequency Reuse: A 3-sector base station is standard for cellular, and it also

suits WiMAX systems (Figure 3.1). To make the best use of available wireless spectrum, WiMAX

systems can utilize both sector and frequency reuse. Sector reuse is using one sector to cover

multiple areas, at least one of which is closer to another base station. Frequency reuse is using a

frequency to serve multiple sectors that do not mutually interfere.

Fig . 3.1 Sector Wireless System with Frequency (Channel) Reuse

With a frequency reuse of fig.1, each of a base stations three sectors uses the same channel

(thus effectively combining the three sectors into a single sector). A frequency reuse of three

eliminates co-channel interference at the sector boundaries. This reuse also significantly decreases

co-channel interference between neighbouring cells due to the increased spatial separation for

channels operating at the same frequency provided that the cell sector boundaries are properly

aligned. Getting the right alignment involves down-tilting antennas and performing drive tests to

see if each sector covers the proposed azimuths. The inherent properties of WiMAXs Orthogonal

Frequency Division Multiple Access (OFDMA) scheme controls adjacent channel interference

(ACI) at the sector boundaries.


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Beam-forming thus addresses the fundamental power problem encountered in delivering

personal broadband with high data rates. With beam-forming, a base station does not need enough

RF power to broadcast high data rates to every part of the coverage area simultaneously. Base

stations can apply their power selectively, thus providing excellent coverage at lower costs. All

customer devices must support beam-forming as part of the WiMAX Forum Wave2 certification for

PHY and MAC features. However, the quality of the beam-forming implementation varies

considerably from one vendor to another.

3.4.0 SECURITY IN WIMAX TECHNOLOGY

Security is a broad and complex subject, and this section provides only a brief introduction

to it. However, basic security issues are being covered, introducing some terminology, and

providing a brief overview of some of the security mechanism of WiMAX Technology.

Well designed security architecture for a WiMAX and other wireless communication

networks should support the following essential requirements:

i. Privacy: Provides protection from eavesdropping as the user data traverses the network

from source to sink.

ii. Data integrity: This ensures that user data and control/management messages are

protected from being tampered with while in transit.

iii. Authentication: Have a mechanism to ensure that a given user/device is the one it claims

to be. Conversely, the user/device should also be able to verify the authenticity of the

network that it is connecting to. Together, the two are referred to as mutual

authentication.

iv. Authorization: Has a mechanism in place to verify that a given user is authorized to

receive a particular service.

v. Access control: Ensures that only authorized users are allowed to get access to the offered

services.
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Documents

Investigation of the Various Applications of WiMAX Standars in Telecommunication Engineering