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Chapter 1Introduction

It is common knowledge that over the last decade there has been a major boost in communication networks. In fact, the development of high-performance backbone networks was immediately followed by the rapid dissemination of broadband wired access technologies, such as leased lines based on fiber-optic links, cable modems using coaxial systems, and digital subscriber line (xDSL) access networks. This gave users a whole new class of services that exploit the increasing number of available network resources. Many new services are based on multimedia applications, such as voice over IP (VoIP), video conferencing, video on demand (VoD), massive online gaming, and peer-to-peer. Unlike traditional TCP/IP services, multimedia applications usually require strict network guarantees such as reserved bandwidth or bounded delays. In today environment Wi-Fi is a very popular term that use for wireless access in short campus. A Wi-Fi enabled device such as a personal computer, video game console, mobile phone, MP3 player or personal digital assistant can connect to the Internet when within range of a wireless network connected to the Internet[47] .1.1 WiMAXWiMAX is an acronym meaning Worldwide Interoperability for Microwave Access (WiMAX). WiMAX is based on Wireless Metropolitan Area Networking (WMAN) standards developed by the IEEE 802.16 group. WiMAX enables the delivery of broadband wireless services anytime, anywhere [3][47]. The IEEE 802.16 standard was developed to deliver Non-Line-Of-Sight (NLOS) connectivity between a subscriber station and base station with typical cell radius of three to ten kilometres. WiMAX systems can be expected to deliver capacity of up to 40 Mbps per channel. This is enough bandwidth to simultaneously support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL (Digital Subscriber Line) speed connectivity. A broad industry consortium, the WiMAX Forum has begun certifying broadband wireless products for interoperability and compliance with a standard [47]. The WiMAX mobile network deployments are to provide up to 15 Mbps of capacity within a typical cell radius of up to three kilometres. WiMAX technology already has been incorporated in notebook computers and PDAs (Personal Digital Assistant) to deliver high speed mobile Internet services anytime, anywhere[3] [4]. WiMAX is the next generation of wireless technology deliberated to facilitate high speed mobile Internet access to the large array of devices including notebook PCs, smart-phones etc. It makes possible the delivery of last mile wireless broadband access as an alternative to cable and Digital Subscriber Line (DSL).IEEE 802.16 is a standard for wireless broadband access network. The main advantages of 802.16 when compared to other network access technologies, such as 802.11, are the longer transmission range and more sophisticated support for Quality of-Service (QoS) at the MAC level. Various application and service types can be used in 802.16 networks and the MAC layer is designed to support this convergence [3][4] .1.2 Background of WiMAX Network 802.16The IEEE 802.16 Working Group is the IEEE group for Wireless Metropolitan Area Networks (WMANs) air interface for Fixed Broadband Wireless Access Systems. IEEE 802.16 group was formed in 1998 to develop standards and recommended practices to support the development and deployment of fixed broadband wireless access systems or air-interface standards. The first 802.16 standard was approved in December 2001. it is designed as to use the single carrier physical layer with time division multiplexing [25][47] IEEE-802.16a was an amendment to 802.16. 802.16a was ratified in January 2003 and was intended to provide last mile fixed broadband access 802.16c. In September 2003, a revision project called 802.16d commenced IEEE 802.16d which is for fixed subscriber stations. This project concluded in 2004 with the release of 802.16-2004 which replaced all prior versions including the a/b/c amendments and formed the basis for the first WiMAX solution [23]. These early WiMAX solutions based on IEEE 802.16-2004 targeted fixed applications, and are referred to as Fixed WiMAX. IEEE 802.16e which supports mobility. WiMAX devices are created to operate the three different bands 2.5, 3.5 and 5.7 GHz. The physical layer In WiMAX uses orthogonal frequency division multiplexing (OFDM) technology and the maximum data rate in WiMAX is 70 Mbps. Wi-max is intended to give a higher coverage area of 20 miles. WiMAX standard eliminate the problem of last mile and act as an alternative to cable and DSL technologies. Since it support mobile application thats why it is called as mobile WiMAX [9]. [23] Table 1.1 [9] shows the data for WiMAX standards.

Parameters802.16802.16-2004802.16e-2005

StatusCompleted December 2001Completed June 2004 Completed December 2005

Frequency band10GHz66GHz2GHz11GHz2GHz11GHz for fixed; 2GHz6GHz for mobile applications

ApplicationFixed LOSFixed NLOSFixed and mobile NLOS

MAC architecturePoint-to-multipoint, meshPoint-to-multipoint, meshPoint-to-multipoint, mesh

Transmission schemeSingle carrier onlySingle carrier, 256 OFDM or 2,048 OFDMSingle carrier, 256 OFDM or scalable OFDM with 128, 512, 1,024, or 2,048 subcarriers

ModulationQPSK, 16 QAM, 64 QAMQPSK, 16 QAM, 64 QAMQPSK, 16 QAM, 64 QAM

Gross date ratio32Mbps-134.4Mbps1Mbs-75Mbps1Mbps -75 Mbps

MultiplexingBurst TDM/ TDMABurst TDM/ TDMA/OFDMABurst TDM/ TDMA/OFDMA

DuplexingTDD and FDDTDD and FDDTDD and FDD

Channel Bandwidth20 MHz, 25MHz, 28MHz1.75MHz to 8.75MHz1.75MHz to 8.75MHz

WiMAX implementationNone OFDMA as fixed WiMAXOFDMA as mobile WiMAX

Table 1.1 Basic Data on IEEE 802.16 Standards1.3 WiMAX Architectural Issues Figure 1.1 shows a WiMAX Network Management Reference Model. WiMAX uses MIB, which stands for Management Information Base, to store information pertinent to network management. WiMAX is used as metropolitan area network wireless connectivity. WiMAX provides broadband data access for urban and rural areas. It provides point-to-point links, residential broadband and high-speed business connections. WiMAX systems also support mesh networks, allowing WiMAX system to forward packets between base stations and subscribers without having to install communication lines between base stations[4] [16].

Figure 1.1: WiMAX Network Management Reference ModelVarious architectural issues involved with WiMAX like point to point Vs point to multipoint, Los Vs NLOS are discussed in following :1.3.1 P2P Vs PMP There are two scenarios for wireless deployment: point-to-point and point-to-multipoint [1][2].1.3.2 Point-to-Point (P2P)Point to point is used where there are two points of interest: one sender and one receiver. This is also a scenario for backhaul or the transport from the data source (data center, fiber, Central Office, etc) to the subscriber or for a point for distribution using point to multipoint architecture. Backhaul radios comprise an industry of their own within the wireless industry.

Figure 1.2 : Point-to Point and Point-to-Multipoint ConfigurationsAs the architecture calls for a highly focused beam between two points range and throughput of point-to point radios will be higher than that of point-to-multipoint products. 1.3.3 Point-to-Multipoint (PMP) As shown in the figure 1.1, point-to-multipoint is synonymous with distribution. One base station can service hundreds of dissimilar subscribers in terms of bandwidth and services offered. 1.3.4 LOS Vs NLOS Earlier wireless technologies were unsuccessful in the mass market as they could not deliver services in non-line-of-sight scenarios. This limited the number of subscribers they could reach. WiMAX functions best in line of sight situations and, unlike those earlier technologies, offers acceptable range and throughput to subscribers who are not line of sight to the base station. LoS and non-LoS configuration shown in fig. 13.WiMAX's ability to deliver services non-line-of-sight, the WiMAX service provider can reach many customers in high-rise office buildings to achieve a low cost per subscriber because so many subscribers can be reached from one base station[9][25].

Figure 1.3: The difference between line of sight and non-line of sight1.4 WiMAX Types Various WiMAX types like Fixed WiMAX and Mobile WiMAX are discussed in following subtopics [10]: 1.4.1 Fixed WiMAXWiMAX provides fixed, portable or mobile non-line-of sight service from a base station to a subscriber station, also known as customer premise equipment (CPE). Some goals for WiMAX include a radius of service coverage of 6 miles from a WiMAX base station for point-to-multipoint, non-line-of-sight service. This service should deliver approximately 40 megabytes per second (Mbps) for fixed and portable access applications. The WiMAX cell site should offer enough bandwidth to support hundreds of businesses with T1 speeds and thousands of residential customers with the equivalent of DSL services from one base station [4]. 1.4.2 Mobile WiMAXMobile WiMAX takes the fixed wireless application a step further and enables cell phone-like applications on a much larger scale. For example, mobile WiMAX enables streaming video to be broadcast from a speeding police or other emergency vehicle at over 70 MPH. In addition to being the final leg in a quadruple play, it offers superior building penetration and improved security measures over fixed WiMAX. Mobile WiMAX will be very valuable for emerging services such as mobile TV and gaming [4][17].1.5. Challenges in WiMAX NetworkIn WiMAX there are few important technical areas. They are listed in the followings [19][9].Wireless radio channel-wireless radio play a very important role in WiMAX . As compared to other communication channels the signals are protected by the physical medium which is comparably stable and robust. There are certain more factors like obstructions, terrain undulations, relative motion between the transmitter and the receiver, interference, noise created by some other source can affect the radio channel and these factors are more unpredictable. These are the some factors which need to be taken care in WiMAX, for example shadowing, multipath fading, inter symbol interference, Doppler spread, Additive white Gaussian noise (AWGN) [9][19].1.5.1 Spectrum scarcity:-In WiMAX the range of spectrum allocation has a very less as compared to other wireless network. WiMAX is designed especially for the need of providing service for increasing number of users and providing flexible applications user services thats why the designers need to use the spectrum more efficiently [9].1.5.2 Quality of service:-WiMAX designed to provide a high range of application. An application can be of different type such as voice, data, video and multimedia [2].Every application is depend upon the terms like data rate, traffic flow, packet loss, delay and so on. So it is a challenge to rightly balance the resource allocation with various applications and users and another factor the QoS requirement across the wireless link, Quality of service has to be defined for end-to-end users in the network that includes switching a variety of aggregation, switching and routing elements between the end to end users [9][26].1.5.3 Latency - Latency is the end-to-end delay of the voice signal from the person on one side of the conversation to the person on the other end of the conversation. [20].1.5.4 Packet Loss - Packet loss occurs when one or more of these packets are lost during transmission. Packet loss can occur due to network congestion or connectivity errors between end- points. To decrease packet loss in VoIP , the Service Provider should ensure that sufficient bandwidth is available for the given VoIP session regardless of whether it is over a wired or wireless medium [4][20].1.5.5 Jitters - Jitter is variation in the order and time in which packets are sent and received. In an attempt to smooth the incoming voice packets, a jitter buffer has been implemented in all modern VoIP deployments. [8]1.5.6 Mobility:-The challenge for mobility is comes from the fact of handling roaming and handoff process. It is very important thing to find the right way of handling the resource consumption and the performance. The future of WiMAX network consist of IP based network so it is also important to define the IP-based mobility management [9].1.5.7 Power consumption:-Power consumption is another very important issue in the WiMAX network. Portability and mobility are key points in power management. The need of low power saving protocols, better signal-processing algorithms, circuit-design with low power and fabrication, and battery technologies with long life are key issues in the field of power consumption. In WiMAX there is need to search for power efficient transmission schemes and power saving protocols [9].1.5.8 Security:- Security is important feature for any network and it is also play important role in the WiMAX. From the user perspective the privacy and data integrity are the essential parameters in security and from service providers perspective they want to prevent unauthorized use of the network resources and provide service per user demand [9].1.5.9 Support IP in wireless :-IP-based networking has the advantages of cost and flexibility for supporting more applications and their popularity in the modern communication protocol However challenges are following like efficient bandwidth, more reliability and quality of service. These points should be more precise and more flexible and it should be changes according to the changes in the network [9].1.6 Features of WiMAXWiMAX is a wireless broadband solution that offers a rich set of features with a lot of flexibility in terms of deployment options and potential service are offerings. Some of the more salient features that deserve highlighting are as follows [19] [24]: 1.6.1Very high peak data rates: WiMAX is capable of supporting very high peak data rates. In fact, the peak PHY data rate can be as high as 74Mbps when operating using a 20MHz wide spectrum. More typically, using a 10MHz spectrum operating using TDD scheme with a 3:1 downlink-to-uplink ratio, the peak PHY data rate is about 25Mbps and 6.7Mbps for the downlink and the uplink, respectively[19][10].1.6.2 OFDM-based physical layer: The WiMAX physical layer (PHY) is based on orthogonal frequency division multiplexing, a scheme that offers good resistance to multipath, and allows WiMAX to operate in NLOS conditions. OFDM is now widely recognized as the method of choice for mitigating multipath for broadband wireless [7][10]. 1.6.3 Adaptive modulation and coding (AMC): WiMAX supports a number of modulation and forward error correction (FEC) coding schemes and allows the scheme to be changed on a per user and per frame basis, based on channel conditions. The adaptation algorithm typically calls for the use of the highest modulation and coding scheme that can be supported by the signal-to-noise and interference ratio at the receiver such that each user is provided with the highest possible data rate [19]. 1.6.4 Support for advanced antenna techniques: The WiMAX solution has a number of hooks built into the physical-layer design, which allows for the use of multiple-antenna techniques, such as beam forming, space-time coding, and spatial multiplexing. These schemes can be used to improve the overall system capacity and spectral efficiency by deploying multiple antennas at the transmitter and/or the receiver [19]. 1.6.5 Quality-of-service support: The WiMAX MAC layer has a connection-oriented architecture that is designed to support a variety of applications, including voice and multimedia services. The system offers support for QoS parameters such as constant bit rate, variable bit rate, real-time, and non-real-time traffic flows, in addition to best-effort data traffic. WiMAX MAC is designed to support a large number of users, with multiple connections per terminal, each with its own QoS requirement [18][19]. 1.6.6 Link-layer retransmissions: For connections that require enhanced reliability, WiMAX supports automatic retransmission requests (ARQ) at the link layer. ARQ-enabled connections require each transmitted packet to be acknowledged by the receiver; unacknowledged packets are assumed to be lost and are retransmitted. WiMAX also optionally supports hybrid-ARQ, which is an effective hybrid between FEC and ARQ [19]. 1.6.7 IP-based architecture: The WiMAX Forum has defined a reference network architecture that is based on an all-IP platform [12]. All end-to-end services are delivered over an IP architecture relying on IP-based protocols for end-to-end transport, QoS, session management, security, and mobility. Reliance on IP allows WiMAX to ride the declining cost curves of IP processing, facilitate easy convergence with other networks, and exploit the rich ecosystem for application development that exists for IP [19]. 1.6.8 Robust security: WiMAX supports strong encryption, using Advanced Encryption Standard (AES), and has a robust privacy and key-management protocol. The system also offers a 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[19]. 1.7 Applications of WiMAXWiMAX has the potential to replace a number of existing telecommunications infrastructures. In a fixed wireless configuration, it can replace the telephone company's copper wire networks, the cable TV's coaxial cable infrastructure while offering Internet Service Provider (ISP) services. In its mobile variant, WiMAX has the potential to replace cellular networks.[16] This Broadband technology, which put forward Point-to-Multi Point (PMP) broadband wireless access. It offers both fixed and mobile broadband wireless Internet access with a high range equal to 30 miles, and can transport broadband at around 1 gigabits/sec. WiMAX covers large regions such as metro cities, suburban, or rural, supporting mobile broadband Internet access at speeds similar to existing broadband. It also provides the mobility features, i.e., connection to Internet will be always be there even when moving. It permits right to use broadband Internet in high 77.5 miles per hour vehicular speed [16] [46].WiMAX major application area is to provide portable mobile broadband connectivity among different cities and countries. WiMAX makes available coverage areas in miles which is enough to cover whole city. Even though, WiMAX backhaul can cover entire nation. WiMAX can presents same speed as a DSL line presents, thus WiMAX use will be cost effective instead of deploying DSL line. WiMAX can handle all kinds of network traffics, i.e., voice, video, and data with Quality of Service (QoS) related issues .ApplicationsBandwidth GuidelinesLatency GuidelinesSuitable QoS Class

Multiplayer Interactive Gaming Low50 kbpsLow