Broadband/the WiMAX system

CHAPTER 1
INTRODUCTION
1.1 Introduction
The experienced growth in the use of digital networks has led to the need for the design of new communication networks with higher capacity. The telecom industry is expected to continue to grow as demand increases for cable and high-speed internet in previously un-serviced locations and as local telephone companies upgrade their lines in response to increasing competitions.
Broadband wireless sits at the confluence of two of the most remarkable growth stories of the telecommunications industry in recent years. Both wireless and broadband have on their own enjoyed rapid mass-market adoption. Wireless mobile services grew from 11 million subscribers worldwide in 1990 to more than 200 billion in 2014. During the same period, the Internet grew from being a curious academic tool to having about a billion users. This staggering growth of the Internet is driving demand for higher-speed Internet-access services, leading to a parallel growth in broadband adoption. In less than a decade, broadband subscription worldwide has grown from virtually zero to over 200 million. Will combining the convenience of wireless with the rich performance of broadband be the next frontier for growth in the industry? Can such a combination be technically and commercially viable? Can wireless deliver broadband applications and services that are of interest to the end users? Many industry observers believe so.
Before we delve into broadband wireless, let us review the state of broadband access today. Digital subscriber line (DSL) technology, which delivers broadband over twisted-pair telephone wires, and cable modem technology, which delivers over coaxial cable TV plant, are the predominant mass-market broadband access technologies today. Both of these technologies typically provide up to a few megabits per second of data to each user, and continuing advances are making several tens of megabits per second possible. Since their initial deployment in the late 1990s, these services have enjoyed considerable growth. Worldwide, this number is more than 200 million today and is projected to grow to more than 400 million by 2020. The availability of a wireless solution for broadband could potentially accelerate this growth.
What are the applications that drive this growth? Broadband users worldwide are finding that it dramatically changes how we share information, conduct business, and seek entertainment.
Broadband access not only provides faster Web surfing and quicker file downloads but also enables several multimedia applications, such as real-time audio and video streaming, multimedia conferencing, and interactive gaming. Broadband connections are also being used for voice telephony using voice-over-Internet Protocol (VoIP) technology. More advanced broadband access systems, such as fiber-to-the-home (FTTH) and very high data rate digital subscriber loop (VDSL), enable such applications as entertainment-quality video, including high-definition TV (HDTV) and video on demand (VoD). As the broadband market continues to grow, several new applications are likely to emerge, and it is difficult to predict which ones will succeed in the future.
So what is broadband wireless? Broadband wireless is about bringing the broadband experience to a wireless context, which offers users certain unique benefits and convenience. There are two fundamentally different types of broadband wireless services. The first type attempts to provide a set of services similar to that of the traditional fixed-line broadband but using wireless as the medium of transmission. This type, called fixed wireless broadband, can be thought of as a competitive alternative to DSL or cable modem. The second type of broadband wireless, called mobile broadband, offers the additional functionality of portability, nomadicity, and mobility. Mobile broadband attempts to bring broadband applications to new user experience scenarios and hence can offer the end user a very different value proposition. WiMAX (worldwide interoperability for microwave access) technology is designed to accommodate both fixed and mobile broadband applications.
In this chapter, we provide a brief overview of broadband wireless. The objective is to present the background and context necessary for understanding WiMAX.

1.2 Evolution of Broadband Wireless
The history of broadband wireless as it relates to WiMAX can be traced back to the desire to find a competitive alternative to traditional wire line-access technologies. Spurred by the deregulation of the telecom industry and the rapid growth of the Internet, several competitive carriers were motivated to find a wireless solution to bypass incumbent service providers. During the past decade or so, a number of wireless access systems have been developed, mostly by start-up companies motivated by the disruptive potential of wireless. These systems varied widely in their performance capabilities, protocols, frequency spectrum used, applications supported, and a host of other parameters. Some systems were commercially deployed only to be decommissioned later. Successful deployments have so far been limited to a few niche applications and markets. Clearly, broadband wireless has until now had a checkered record, in part because of the fragmentation of the industry due to the lack of a common standard. The emergence of WiMAX as an industry standard is expected to change this situation.
Given the wide variety of solutions developed and deployed for broadband wireless in the past, a full historical survey of these is beyond the scope of this section. Instead, we provide a brief review of some of the broader patterns in this development. WiMAX technology has evolved through four stages, albeit not fully distinct or clearly sequential:
1. Narrowband wireless local-loop systems,
2. First-generation line-of-sight (LOS) broadband systems,
3. Second-generation non-line-of-sight (NLOS) broadband systems, and
4. Standards-based broadband wireless systems.
1.2.1 Narrowband Wireless Local-Loop Systems
Naturally, the first application for which a wireless alternative was developed and deployed was voice telephony. These systems, called wireless local-loop (WLL), were quite successful in developing countries such as China, India, Indonesia, Brazil, and Russia, whose high demand for basic telephone services could not be served using existing infrastructure. In fact, WLL systems based on the digital-enhanced cordless telephony (DECT) and code division multiple access (CDMA) standards continue to be deployed in these markets.
In markets in which a robust local-loop infrastructure already existed for voice telephony, WLL systems had to offer additional value to be competitive. Following the commercialization of the Internet in 1993, the demand for Internet-access services began to surge, and many saw providing high-speed Internet-access as a way for wireless systems to differentiate them. For example, in February 1997, AT&T announced that it had developed a wireless access system for the 1,900MHz PCS (personal communications services) band that could deliver two voice lines and a 128kbps data connection to subscribers. This system, developed under the code name ‘Project Angel,’ also had the distinction of being one of the first commercial wireless systems to use adaptive antenna technology. After field trials for a few years and a brief commercial offering, AT&T discontinued the service in December 2001, citing cost run-ups and poor take-rate as reasons.
During the same time, several small start-up companies focused solely on providing Internet-access services using wireless. These wireless Internet service provider (WISP) companies typically deployed systems in the license-exempt 900MHz and 2.4GHz bands. Most of these systems required antennas to be installed at the customer premises, either on rooftops or under the eaves of their buildings. Deployments were limited mostly to select neighborhoods and small towns. These early systems typically offered speeds up to a few hundred kilobits per second. Later evolutions of license-exempt systems were able to provide higher speeds.
1.2.2 First-Generation Broadband Systems
As DSL and cable modems began to be deployed, wireless systems had to evolve to support much higher speeds to be competitive. Systems began to be developed for higher frequencies, such as the 2.5GHz and 3.5GHz bands. Very high speed systems, called local multipoint distribution systems (LMDS), supporting up to several hundreds of megabits per second, were also developed in millimeter wave frequency bands, such as the 24GHz and 39GHz bands. LMDS based services were targeted at business users and in the late 1990s enjoyed rapid but short-lived success. Problems obtaining access to rooftops for installing antennas, coupled with its shorter range capabilities, squashed its growth.
In the late 1990s, one of the more important deployments of wireless broadband happened in the so-called multichannel multipoint distribution services (MMDS) band at 2.5GHz. The MMDS band was historically used to provide wireless cable broadcast video services, especially in rural areas where cable TV services were not available. The advent of satellite TV ruined the wireless cable business, and operators were looking for alternative ways to use this spectrum. A few operators began to offer one-way wireless Internet-access service, using telephone line as the return path. In September 1998, the Federal Communications Commission (FCC) relaxed the rules of the MMDS band in the United States to allow two-way communication services, sparking greater industry interest in the MMDS band. MCI WorldCom and Sprint each paid approximately $1 billion to purchase licenses to use the MMDS spectrum, and several companies started developing high-speed fixed wireless solutions for this band.
The first generation of these fixed broadband wireless solutions was deployed using the same towers that served wireless cable subscribers. These towers were typically several hundred feet tall and enabled LOS coverage to distances up to 35 miles, using high-power transmitters. First-generation MMDS systems required that subscribers install at their premises outdoor antennas high enough and pointed toward the tower for a clear LOS transmission path. Sprint and MCI launched two-way wireless broadband services using first-generation MMDS systems in a few markets in early 2000. The outdoor antenna and LOS requirements proved to be significant impediments. Besides, since a fairly large area was being served by a single tower, the capacity of these systems was fairly limited. Similar first-generation LOS systems were deployed internationally in the 3.5GHz band.
1.2.3 Second-Generation Broadband Systems
Second-generation broadband wireless systems were able to overcome the LOS issue and to provide more capacity. This was done through the use of a cellular architecture and implementation of advanced-signal processing techniques to improve the link and system performance under multipath conditions. Several start-up companies developed advanced proprietary solutions that provided significant performance gains over first-generation systems. Most of these new systems could perform well under non-line-of-sight conditions, with customer-premise antennas typically mounted under the eaves or lower. Many solved the NLOS problem by using such techniques as orthogonal frequency division multiplexing (OFDM), code division multiple access (CDMA), and multiantenna processing. Some systems, such as those developed by SOMA Networks and Navini Networks, demonstrated satisfactory link performance over a few miles to desktop subscriber terminals without the need for an antenna mounted outside. A few megabits per second throughput over cell ranges of a few miles had become possible with second generation fixed wireless broadband systems.
1.2.4 Emergence of Standards-Based Technology
In 1998, the Institute of Electrical and Electronics Engineers (IEEE) formed a group called 802.16 to develop a standard for what was called a wireless metropolitan area network, or wireless MAN. Originally, this group focused on developing solutions in the 10GHz to 66GHz band, with the primary application being delivering high-speed connections to businesses that could not obtain fiber. These systems, like LMDS, were conceived as being able to tap into fiber rings and to distribute that bandwidth through a point-to-multipoint configuration to LOS businesses.
The IEEE 802.16 group produced a standard that was approved in December 2001. This standard, Wireless MAN-SC, specified a physical layer that used single-carrier modulation techniques and a media access control (MAC) layer with a burst time division multiplexing (TDM) structure that supported both frequency division duplexing (FDD) and time division duplexing (TDD).
After completing this standard, the group started work on extending and modifying it to work in both licensed and license-exempt frequencies in the 2GHz to 11GHz range, which would enable NLOS deployments. This amendment, IEEE 802.16a, was completed in 2003, with OFDM schemes added as part of the physical layer for supporting deployment in multipath environments. By this time, OFDM had established itself as a method of choice for dealing with multipath for broadband and was already part of the revised IEEE 802.11 standards. Besides the OFDM physical layers, 802.16a also specified additional MAC-layer options, including support for orthogonal frequency division multiple access (OFDMA).
Further revisions to 802.16a were made and completed in 2004. This revised standard, IEEE 802.16-2004, replaces 802.16, 802.16a, and 802.16c with a single standard, which has also been adopted as the basis for HIPERMAN (high-performance metropolitan area network) by ETSI (European Telecommunications Standards Institute). In 2003, the 802.16 group began work on enhancements to the specifications to allow vehicular mobility applications. That revision, 802.16e, was completed in December 2005 and was published formally as IEEE 802.16e-2005.
It specifies scalable OFDM for the physical layer and makes further modifications to the MAC layer to accommodate high-speed mobility. As it turns out, the IEEE 802.16 specifications are a collection of standards with a very broad scope. In order to accommodate the diverse needs of the industry, the standard incorporated a wide variety of options. In order to develop interoperable solutions using the 802.16 family of standards, the scope of the standard had to be reduced by establishing consensus on what options of the standard to implement and test for interoperability. The IEEE developed the specifications but left to the industry the task of converting them into an interoperable standard that can be certified. The WiMAX Forum was formed to solve this problem and to promote solutions based on the IEEE 802.16 standards. The WiMAX Forum was modeled along the lines of the Wi-Fi Alliance, which has had remarkable success in promoting and providing interoperability testing for products based on the IEEE 802.11 family of standards.
The WiMAX Forum enjoys broad participation from the entire cross-section of the industry, including semiconductor companies, equipment manufacturers, system integrators, and service providers. The forum has begun interoperability testing and announced its first certified product based on IEEE 802.16-2004 for fixed applications in January 2006. Products based on IEEE 802.18e-2005 are expected to be certified in early 2007. Many of the vendors that previously developed proprietary solutions have announced plans to migrate to fixed and/or mobile WiMAX. The arrival of WiMAX-certified products is a significant milestone in the history of broadband wireless.
1.3 WiMAX versus 3G and Wi-Fi
How does WiMAX compare with the existing and emerging capabilities of 3G and Wi-Fi? The throughput capabilities of WiMAX depend on the channel bandwidth used. Unlike 3G systems, which have a fixed channel bandwidth, WiMAX defines a selectable channel bandwidth from 1.25MHz to 20MHz, which allows for a very flexible deployment. When deployed using the more likely 10MHz TDD (time division duplexing) channel, assuming a 3:1 downlink-to-uplink split and 2 ” 2 MIMO, WiMAX offers 46Mbps peak downlink throughput and 7Mbps uplink. The reliance of Wi-Fi and WiMAX on OFDM modulation, as opposed to CDMA as in 3G, allows them to support very high peak rates. The need for spreading makes very high data rates more difficult in CDMA systems.
More important than peak data rate offered over an individual link is the average throughput and overall system capacity when deployed in a multicellular environment. From a capacity standpoint, the more pertinent measure of system performance is spectral efficiency. The fact that WiMAX specifications accommodated multiple antennas right from the start gives it a boost in spectral efficiency. In 3G systems, on the other hand, multiple-antenna support is being added in the form of revisions. Further, the OFDM physical layer used by WiMAX is more amenable to MIMO implementations than are CDMA systems from the standpoint of the required complexity for comparable gain. OFDM also makes it easier to exploit frequency diversity and multiuser diversity to improve capacity. Therefore, when compared to 3G, WiMAX offers higher peak data rates, greater flexibility, and higher average throughput and system capacity.
Another advantage of WiMAX is its ability to efficiently support more symmetric links’useful for fixed applications, such as T1 replacement’and support for flexible and dynamic adjustment of the downlink-to-uplink data rate ratios. Typically, 3G systems have a fixed asymmetric data rate ratio between downlink and uplink.
What about in terms of supporting advanced IP applications, such as voice, video, and multimedia? How do the technologies compare in terms of prioritizing traffic and controlling quality? The WiMAX media access control layer is built from the ground up to support a variety of traffic mixes, including real-time and non-real-time constant bit rate and variable bit rate traffic, prioritized data, and best-effort data. Such 3G solutions as HSDPA and 1x EV-DO were also designed for a variety of QoS levels.
Perhaps the most important advantage for WiMAX may be the potential for lower cost owing to its lightweight IP architecture. Using an IP architecture simplifies the core network’3G has a complex and separate core network for voice and data’and reduces the capital and operating expenses. IP also puts WiMAX on a performance/price curve that is more in line with general-purpose processors (Moore’s Law), thereby providing greater capital and operational efficiencies. IP also allows for easier integration with third-party application developers and makes convergence with other networks and applications easier.
In terms of supporting roaming and high-speed vehicular mobility, WiMAX capabilities are somewhat unproven when compared to those of 3G. In 3G, mobility was an integral part of the design; WiMAX was designed as a fixed system, with mobility capabilities developed as an add-on feature.
In summary, WiMAX occupies a somewhat middle ground between Wi-Fi and 3G technologies when compared in the key dimensions of data rate, coverage, QoS, mobility, and price.
1.4 Motivation
Nowadays, life does not seem feasible without wireless networks in one or the other form. Wireless is becoming the leader in communication choices among users. In the current era life is converging towards the cable less environment where the last mile connectivity can be easily achievable without the need of physical connections. So the field of wireless communication is continuously emerging one which is the demand for the transfer of data with high speed and with long coverage range. The claim for broadband mobile services continues to grow. Usually, high-speed broadband solutions are based on wired-access technologies such as digital subscriber line (DSL). This type of solution is not easy to deploy in remote rural areas, and furthermore it lacks support for terminal mobility.]
Also the gradual development in the use of wireless networks has led to the requirement for the design of new modern communication networks with higher capacity and lower error rate. The telecommunication industry is also upgrading, with a requirement for a greater range of services, such as video conferences, or applications with multimedia contents. The increased dependence on computer networking and the internetwork has resulted in a larger demand for connections to be allotted any time, any place, leading to a increase in the requirements for greater capacity and ultimate reliable broadband wireless communication systems.
For this issue, new technologies with high throughput with less requirement of bandwidth have been designed. As a matter of fact the requirements on bandwidth and spectrum availability are endless. As a result, the designers working in the domain of wireless communication has to face the lots of difficulties to fulfill the requirement of bandwidth for the efficient and accurate transmission and reception. Moreover the problems of time varying nature of channel such as fading and multipath put the limitation on the performance of high data rate with good quality of service. The demands for greater capacity, high reliability as well as accuracy are the prime requisites for the forth coming generations of the wireless networking systems such as Wi-Fi, WiMAX, etc.
1.5 Objective of Thesis
How to deal with fading and with interference is central aim to the design of wireless communication systems, and by taking the advantage of multi-path fading and improving the system capacity and bit rate of 4G modern wireless system will be the fundamental objective of this research work. The research work includes the performance analysis of following points:
‘ To study and to analysis the performance of forthcoming future generation wireless networking technique i.e. WiMAX as the upcoming 4G standard for meeting the requirements of last mile end to end wireless network with greater system capacity with improved bit error rate.
‘ To analyze the features of antenna diversity techniques in wireless communication for nullifying the limitations due to multipath fading by simulating the system in terms of system throughput and bit error rate under MATLAB based environment.
‘ To simulate the complete WiMAX system by implementing antenna diversity techniques and Alamouti coding in it to fulfill the current demands of the modern wireless networks with the anticipation of improvement in bit error rate thereby increment in system reliability.
1.6 Organization of Thesis
This research work examines the modeling, simulation and comparative analysis of WiMAX system along with the implementation of various antenna diversity techniques in it built with MATLAB. The whole thesis is organized in 6 chapters.
Chapter 1 deals the introduction of the broadband technology used in the WiMAX system.
Chapter 2 deals the all related work by the previous researchers. In this chapter we discuss the paper based on the previous work associated with the WiMAX system and found problem in the WiMAX system.
Chapter 3 deals the fundamentals of the WiMAX system. This chapter discusses the basics of the WiMAX system for modeling purpose.
Chapter 4 deals the technology used in the WiMAX system. In these chapter diversity techniques is conceptually discussed. Also discuss the antenna diversity too.
Chapter 5 is based on the chapter 3 to 4. In this chapter a simulink model is generated with the result to analyzed the WiMAX physical layer for antenna diversity.
Chapter 6 is the conclusion and future work of the thesis.

CHAPTER 2
LITRATURE REVIEW
CHAPTER 2
LITRATURE REVIEW
2.1 Introduction
In this section, a brief review of literature on Performance of Antenna Diversity Techniques, Alamouti Coding Scheme, WiMAX Broadband Wireless Access Technology, Mobile WiMAX Technology, IEEE 802.16 Standards, Efficient Wireless Channels and Orthogonal Frequency Division Multiplexing Technique are reported and discussed.
2.2 Related work
Abdulrahman Yarali, Saifur Rahman [6] describes the overview of the forthcoming most promising wireless system WiMAX-Worldwide Interoperability for Microwave Access. In this research paper the basic WiMAX introduction, comparison with the existing wireless systems, types of IEEE standards as well as layered structure has been included. This paper presented a brief description of some of the major functions of a WiMAX network architecture currently being designed and specified in the network group. This paper is useful to analyze the basic architecture and supporting features of WiMAX for this research work.
Mai Tran, George Zaggoulos, Andrew Nix and Angela Doufexi [7] describes the current demand of wireless communication system is to achieve highest capacity with lowest requirement of bandwidth and improved error rate. The mobile WiMAX is the wonderful invention which is fulfilling the latest demand. This research paper presents the theoretical aspect of the mobile WiMAX system whose remarkable features are scalable OFDM and Advanced antenna techniques such as MIMO. Each and every parameter which are required to build and to model the WiMAX system such as channel coding, sampling frequency, sampling period, symbol duration of OFDM, modulation scheme, etc. have been discussed in this paper which are the useful matters to develop a simulation model of this research work.
Liangshan Ma, Dongyan Jia [8] analyses both the competitive and cooperative relationships between WiMAX, WLAN and 3G from various aspects such as technical standards, current status and future trends, etc. WiMAX and WLAN are two most emerging IEEE standards for providing efficient wireless networking whereas 3G is the most important mobile communication standard for providing highest speed along with maximum accuracy. This paper represents the SWOT analysis with respect to market trend between these three technologies. This paper will be helpful to understand the role of one technique to cope up with other technologies.
Abdulrahman Yarali Bwanga Mbula Ajay Tumula [9] identifies the cost effective, flexible 4th generation standard of IEEE i.e. WiMAX system which is becoming the perfect solution to meet the current demands of the future wireless networks thereby providing the tough competition to the existing 3G standards. This paper includes the modeling of WiMAX layer by considering its physical layer as well as various parameters related to it which is the main utilization in this research work. The two variants of WiMAX system i.e. fixed WiMAX (IEEE 802.16d) and mobile WiMAX (IEEE 802.16e) have been included in the paper which helps to derive the characteristics of WiMAX system. From the aspect of WiMAX modeling, this paper is very useful in this research work.
Sassan Ahmadi, Intel Corporation[10] presents the thorough analysis of IEEE 802.16 architecture which is becoming the most popular 4G standard for the different mobile communication applications. The growing demand for mobile Internet and wireless multimedia applications has motivated the development of broadband wireless access technologies in recent years. Mobile WiMAX has enabled convergence of mobile and fixed broadband networks through a common wide-area radio-access technology and flexible network architecture. The theoretical aspect of WiMAX architecture and parameters of this paper at very minute level helps in this research work to understand the whole WiMAX system.
Hicham Yehia and Hany Kamal [11] discusses the effect of interference in the WiMAX network thereby analyzing the effect of the same on the capacity of the network. Due to imperfections at both the ends of the system i.e. at transmitter and at the receiver, the interference can occur which limits the system performance. At the transmitter due to inefficient filter response, spurious transmission can be encountered and at the receiver, due to insufficient selectivity, the interference will occur. The paper checks the effects of this kind of interference in the WiMAX system which is the main reason behind the degradation in the network capacity.
Raj Jain, Chakchai So-In, And Abdel-Karim Al Tamimi [12] basically deals with the analysis of one to one layer of the WiMAX network which is the very important issue from the view point of service providers and network developers. The paper includes the system level modeling at various levels such as physical layer modeling, MAC layer modeling, interference level modeling, frequency level modeling, etc so as to analyze many system level parameters. The readings and observations generated at the abstract level are the very useful outcomes for this research work.
Nedeljko Cvejic and Seppanen, Tapio [13] illustrate that for the efficient and fruitful wireless communication, the virtual channel i.e. radio channel of propagation should be modeled properly. This paper estimates the efficiency of AWGN channel and Rayleigh channel under different scenarios. As per the nature of application, the type of channel modeling should get selected. In this paper, the concentration is on the modern digital video compression technique i.e. mp3 system where during watermarking, the impairment due to noise in the transmission would be analyzed by modeling the channel as Rayleigh channel which is frequency selective channel not by AWGN channel. This paper justifies the utility and use of channel modeling in this research.
Daniele Lo Iacono, Marco Ronchi, Luigi Della Torre, and Fabio Osnato[14] discuss that in today’s world, the main goal of any system is to achieve highest system capacity with lowest error rate which is not possible with single transmitter and single receiving antenna because it can’t overcome the effects of fading. For this particular reason, the current wireless communication trend is tilting towards the multiple transmitter and multiple receiver antenna systems i.e. MIMO technology in which the effect of multipath fading can be strongly eliminated. This research paper is based on the same fundamental by considering the effect and application of MIMO technique with the implementation of OFDM in wireless communication system. The methodology and results derived from the experiment of MIMO and OFDM are very useful deductions for this research work.
Onsy Abdel Alim, Hiba S. Abdallah and Azza M. Elaskary [15] discusses two main issues. The first one presents models for simulating OFDM WiMAX system in Simulink including channel estimation and equalization subsystems in MATLAB functions. Next, the effect of channel estimation error on the performance of MIMO VBLAST receivers in uncorrelated Rayleigh flat fading channels is investigated. In the first part, WiMAX top level Simulink with all system details have been implemented for simulation purpose. In the second part, the performance of MIMO VBLAST ZF receivers over uncorrelated Rayleigh flat fading channels in the presence of channel estimation error is investigated. This IEEE transaction is very much useful to derive the simulation model of the WiMAX system along with the reference BER reading with MIMO implementation.
Mohab Shalash, Tallal El Shabrawy and Waleed Diab [16] covers a thorough study of wideband frequency selective channels from the perspective of multi-carrier modulation system. Wideband communications systems suffer from frequency selective channels. Accordingly, 3G/4G systems have endorsed the concept of multi-carrier modulation such as OFDM and MC-CDMA, where the wideband channel is sub-divided into numerous subcarriers. This research paper is useful to analyze the behavior of various wireless channels such as Rayleigh and Rician channel along with the basic parameters of it for modeling purpose. For 3G and 4G systems how the different channels and their parameters are affecting the behavior of the whole system while modeling was the true strength of this paper for this research work point of view.
Muhammad Nadeem Khan, Sabir Ghauri [17] discusses the model building of the WiMAX Physical layer using Simulink in MATLAB. This model is a useful tool for performance evaluation of the WiMAX standards 802.16e under the various parameters like carrier frequency, frequency bands, bandwidth, radio technology etc which have been mentioned. For this research work, this IEEE transaction will be the mile stone. This paper is useful to find the most valuable information regarding the modeling of the WiMAX physical layer with the various aspects of OFDM and MIMO. For WIMAX System modeling, this research paper may come across the very minute detailing of each and every blocks of the WiMAX modeling along with the most precise readings.
Vahid Tarokh, Nambi Seshadr and A. R. Calderbank [18] basically includes the characterization of wide band wireless channel for the future wireless technologies along with the feature of antenna diversity. In this paper the most practical approach of increasing the capacity of the channel has been presented for modern wireless communication systems with the introduction of antenna diversity and space time codes i.e. Alamouti coding. This paper provides the base for this research work regarding the different antenna diversity techniques such as SIMO, MISO, MIMO along with the space time coding.
Tao Jiang and Weidong Xiang [19] describes Multimedia Multicast and Broadcast service (MBS) over wireless links, such as mobile TV and IP radio broadcasting. As one of the most promising enabling technologies, mobile WiMAX can offer scalability in both radio access and network architecture, thus providing important flexibility in terms of network services and deployment options. This paper presents the overview of network architecture of OFDM based WiMAX system. Also the enhanced features such as antenna diversity, multiple modulation schemes, etc which can be a part of WiMAX system for improved network performance are the helpful contents for this research work.
Kamran Etemad [20] discusses the brief of Mobile WiMAX technology with the layered architecture and evolution. Mobile WiMAX combines OFDMA and advanced MIMO schemes along with flexible bandwidth and fast link adaptation, creating a highly efficient air interface that exceeds the capacity of existing and evolving 3G radio access networks. This research paper is useful for the implementation of advanced antenna techniques and OFDMA in the physical layer of WiMAX to improve Quality of Service.
Chengshan Xiao, Jingxian Wu, Sang-Yick Leong and Yahong Rosa Zheng [21] presents a new discrete-time channel model for MIMO systems over space-selective (or spatially correlated), time-selective (or time-varying), and frequency-selective Rayleigh fading channels, which are referred to as triply selective Rayleigh fading channels. MIMO is the current trends in the modern cellular system towards achieving high data rate with low error rate. This paper is helpful in deriving the performance analysis of MIMO system with Rayleigh channel for the research work. Here in this the discrete time channel model has been developed which evaluates the statistical properties of the system.
Zakhia Abichar, Yanlin Peng and J. Morris Chang [22] includes the brief of WiMAX and its layered architecture i.e. physical layer and MAC layer. The theoretical aspects presented in this chapter define the functioning as well features of MAC layer and Physical layer. The MAC layer of the WiMAX technology decides the quality of service and the algorithms related to error control while physical layer is responsible for data transfer with high capacity and low error rate. This paper is purely helpful for the theoretical survey of WiMAX system in the research work.
H. Farhat, G. Grunfelder, A. Carcelen and G. El Zein [23] Illustrate that to improve data rates and to enhance the quality of the system for the future generation wireless systems, the most prominent solution is antenna diversity techniques i.e. MIMO. The referred reference paper gives the design of MIMO channel sounder utilized for the WiMAX technology. The basic illustrations given in this paper related to MIMO system design along with channel characteristic analysis are the useful estimates for this research work.
Onsy Abdel Alim, Nemat Elboghdadly, Mahmoud M. Ashour, Azza M. Elaskary [24] has the objective of building a System level model for a WiMAX Orthogonal Frequency Division Multiplexing based transceiver. OFDM technique theoretically saves the bandwidth about 50%. Modeling irradiation noise as an external effect added to the Additive White Gaussian noise (AWGN). This paper represents the basic simulation model of WiMAX OFDM system which is the most important helpful aspect of the paper in this research work.
Mikko Majanen, Pekka H. J. Perala and Thomas Casey [25] describes that the demand for mobile internet access is continuing its growth at increasing speed. New wireless access technologies compete with each other at the global market and it is still unsure which one will be the winner. One of the most promising ones is WiMAX which is based on IEEE 802.16 air interface standard. This paper includes the WiMAX simulation model along with the handover process. The paper is useful to analyze the three types of handover process i.e. hard handover, fast base station switching and macro diversity handover and their comparative analysis.
Ibrahim A.Z. Qatawneh [26] represents the bit error rate performance comparison of AWGN channel and Rician fading channels by considering their application in multi carrier DE-APSK and single carrier DE-APSK system. Frequency flat Rayleigh fading is a typical channel model found in land mobile radio situations. This model is suitable for modeling urban areas that are characterized by many obstructions where a line of sight path does not exist between the transmitter and receiver. In suburban areas a line of sight path may exist between the transmitter and receiver and this will give rise to Rician fading. The analysis of the channel comparison is the helpful conclusion for this research work.
Alireza Seyedi, Vasanth Gaddam, and Dagnachew Birru [27] represent performance analysis of OFDM UWB system with two antennas at the receiver side. Different antenna selection and combining methods, such as simple antenna selection, antenna selection per sub-carrier, equal gain combining and maximal ratio combining are considered. This paper discusses the simulation model, different antenna selection and combining techniques which are the important conclusions for this research work.
Shigenobu Sasaki Hisakazu Kikuchi Jinkang ZHU [28] discussed the performance of system over the type of frequency non-selective Rayleigh fading scenario. Fading and interferences are the two phenomenons that make the problem domain of modern wireless communication system most challenging and interesting. This paper illustrates the implementation of the diversity techniques for the significant reduction in Bit Error Rate performance over fading channel. The degradation of performance is over come by introducing the selection diversity and time diversity techniques. This research paper is useful to introduce the time diversity technique i.e. Reed-Solomon coding in physical layer modeling of WiMAX system for the remarkable reduction in system BER.
Koon Hoo Teo, Zhifeng Tao, and Jinyun Zhang [29] discussed the IEEE 802.16e Standards for Mobile WiMAX. This paper illustrates the implementation of frequency diversity technique for the high speech mobile service perspective. Also the comparison of WiMAX standards with WLANs and cellular is mentioned. More specifically this paper focused on the exploitation of technology in Mobile WiMAX standards. This paper is useful for the modeling of WiMAX System using IEEE 802.16e standards.
Rick S. Blum, Senior, Jack H. Winters and Nelson R. Sollenberger [30] discussed the benefits of transmitting the information through the multiple antennas over the fading channels. It also describes that the mutual information of a single, isolated, multiple transmit and receive antenna array link is exploited by transmitting the maximum number of independent data streams for a flat fading channel with independent fading coefficients for each path. This paper is useful in this research works as it purely focused on great potential achieved by transmit and receive antenna arrays used in Multiple Input Multiple Output antenna system.
CHAPTER 3
FUNDAMENTAL OF WIMAX SYSTEM MODELING

CHAPTER 3
FUNDAMENTAL OF WIMAX SYSTEM MODELING
3.1 Introduction
WiMAX, the Worldwide Interoperability for Microwave Access is the highly anticipated technology that aims to provide business and consumer wireless broadband services in form of Metropolitan Area Network (MAN). The technology has a target range of up to 31 miles and a target transmission rate exceeding 100 Mbps and is expected to challenge DSL and T1 lines (both expensive technologies to deploy and maintain) especially in emerging markets.
The mobile WiMAX is the wonderful invention which is fulfilling the latest demand. Through its high coverage and data rate characteristics, it fulfills the idea of complete network architecture thereby providing a flexible and cheap solution for the last-mile. The interoperability is a very critical issue, on which equipment cost and volume of sales will be based. Operators will not be bound to a sole equipment supplier, as the radio base stations will be able to interact with terminals produced by different suppliers. From the point of view of cost and accuracy, the customer’s must get the benefit of supplier’s competition. WiMAX may be seen as the fourth generation (4G) of mobile systems as the convergence of cellular telephony, computing, Internet access, and potentially many multimedia applications become a real fact.
WiMAX’s attributes open the technology to a wide variety of applications. With its large range and high transmission rate, WiMAX can serve as a backbone for 802.11 hotspots for connecting to the Internet. Alternatively, users can connect mobile devices such as laptops and handsets directly to WiMAX base stations without using 802.11 which can be very well observed from Figure 3.1. Developers project this configuration for the WiMAX mobile version, which will provide users broadband connectivity over large coverage areas compared with 802.11 hotspots’ moderate coverage. Mobile devices connected directly to WiMAX base stations likely will achieve a range of 5 to 6 miles, because mobility makes links vulnerable.
Figure 3.1 WiMAX Senario
The technology can also provide fast and cheap broadband access to markets that lack infrastructure (fiber optics or copper wire), such as rural areas and unwired countries. Currently, several companies offer proprietary solutions for wireless broadband access, many of which are expensive because they use chipsets from adjacent technologies, such as 802.11. Manufacturers of these solutions use the physical layer and bypass the medium access control layer by designing a new one. Unlike these proprietary solutions, WiMAX’s standardized approach offers economies of scale to vendors of wireless broadband products, significantly reducing costs and making the technology more accessible. Many companies that were offering proprietary solutions, however, have participated in the WiMAX forum and now offer WiMAX based solutions. WiMAX can be used in disaster recovery scenes where the wired networks have broken down. Similarly, WiMAX can be used as backup links for broken wired links. Additionally, WiMAX will represent a serious competitor to 3G cellular systems as high speed mobile data applications will be achieved with the 802.16e specification.
The main operators have concentrated their interests and efforts on the future applications of this new technology. The WiMAX forum created in April 2002, is a no-profit organization that groups companies promoting the broadband access based on the wireless communication standard, point to multipoint IEEE 802.16 for Metropolitan Area Network. WiMAX forum activities aim to:
‘ support the standardization process of IEEE 802.16 for MAN
‘ select and promote some of the WiMAX profiles defined in the 802.16
‘ certificate the interoperability between WiMAX equipment of different suppliers
‘ make WiMAX a universally accepted technology
3.2 Relationship with other Wireless Technology
Wireless access to data networks is expected to be an area of rapid growth for mobile communication systems. The huge uptake rate of mobile phone technologies, WLANs and the exponential growth that is experiencing the use of the internet have resulted in an increased demand for new methods to obtain high capacity wireless networks. WiMAX is expected to have an explosive growth, as well as the Wi-Fi, but compared with the Wi-Fi, WiMAX provides broadband connections in greater areas, measured in square kilometers, even with links not in line of sight. For these reasons WiMAX is a MAN, highlighting that ‘metropolitan’ is referred to the extension of the areas and not to the density of population. But Wi-Fi and WiMAX are not competing technologies. While WiMAX can provide high capacity internet access to residences and business seats, Wi-Fi allows the extension of such connections inside the corporate sites buildings. Figure-3.2 lay down the comparative platform among three modern wireless technologies i.e. WiMAX, WiFi and 3G cellular telephony.
In any case, both WLAN and cellular mobile applications are being widely expanded to offer the demanded wireless access. However, they experience several difficulties for reaching a complete mobile broadband access, bounded by factors such as bandwidth, coverage area, and infrastructure costs.
As shown in following Figure-3.2, Wi-Fi provides a high data rate, but only on a short range of distances and with a slow movement of the user. On the other hand, cellular offers larger ranges and vehicular mobility, but instead, it provides lower data rates, and requires high investments for its deployment.

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