CHAPTER : 1 INTRODUCTION. 1.1 Basic. 1.2 System Modeling and Simulation

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1 CHAPTER : 1 This research work is presented for the topic MODELING, SIMULATION AND COMPARATIVE ANALYSIS OF WIMAX SYSTEM USING MIMO-OFDM AND ALAMOUTI CODING SCHEME, to the department of Electronics and Communication Engineering, J.J.T. University, Jhunjhunu-Rajasthan. 1.1 Basic 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 [1]. The increased reliance on computer networking and the internet has resulted in a wider demand for connectivity to be provided "any where, any time", leading to a rise in the requirements for higher capacity and high reliability broadband wireless telecommunication systems. 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. One of such strong wireless network contender is the WiMAX system which has been analyzed completely with an innovative aspect of antenna diversity techniques in the research work. Let s inspect and evaluate the main technical aspects of the research work in a brief glimpse. 1.2 System Modeling and Simulation This section describes the very basic terms of the research work that are in short kind of operational processes through which the technology has been implemented for real time use. 1

2 1.2.1 Model A model is a simplified demonstration of the actual system intended for understanding. Whether a model is a good model or not depends on the level to which it facilitates the understanding of the basic concept. Since all models are simplifications of reality there is always a trade-off as to what level of stuff is included in the model. If too little detail is included in the model one takes the risk of missing relevant exchanges and the resultant model does not provide up to the mark sympathetic. If too much detail is included in the model the model may become excessively complicated and actually exclude the development of understanding. Figure-1.1 Basic modeling structure Figure-1.1 shows the analogy between the real time system and its prototype modeling. Here it can be observed that by developing the model of a specific system, the virtual reality of that system can be achieved. Basically the model is analogous to a virtual system that is considered as a real world entity. For a real time system, the behavior can 2

3 be derived by performing real time experiments over it and its outcome can be observed as its response to a particular input data. Now for any emerging technology which has been figured out still on paper, the real time experimentation is not possible in the initial stage of designing. For that issue, the modeling would be the most suitable prototype to analyze its behavior to a maximum extent. By developing the model of a system and performing simulation of it is more or less analogous to the experimentation performed in a real time system. If the model fulfills all possible specifications that is if the derived simulation results approximate towards the experimentation results of a system then the model is said to possess all time validity and its output results are considered almost same to that of the real time system Simulation A simulation is the exploitation of a model in such a means that it operates on time or space to compress it, thus enabling one to make out the interactions that would not otherwise be clear because of their separation in time or space. It generally refers to a computerized translation of the model which is run over time to understand the implications of the defined interactions. Simulations are generally iterative in there design. One develops a model, simulates it, analyses from the simulation, manipulates the model, and continues the iterations until a defined and sufficient level of understanding is developed. Simulations allow setting up a logical situation that allows for integration of simulated systems in the early analysis phase via mixed virtual systems with first typical components to an implicit test environment for the final system. If managed properly, the situation can be migrated from the development and test domain to the training and thereby enabling to develop real time system implementation scenario Modeling and Simulation Modeling and Simulation is a process for developing a level of understanding of the interface of the parts of a system, and of the system as a whole. The level of understanding which may be developed via this process is seldom achievable via any other process. It is the utilization of models, including emulators, prototypes, 3

4 simulators, and stimulators to develop data as a basis for making supervisory or technical decisions. The use of modeling and simulation within engineering is well recognized. Simulation technology belongs to the tool set of engineers of all application domains and has been incorporated into the body of knowledge of engineering management. M&S has already helped to reduce costs and increase the excellence of systems and lessons learned are documented and archived [2] WiMAX System WiMAX may be seen as the most emerging wireless networking standard approved by IEEE for realizing the improved mobile system scenario as the convergence of cellular telephony, computing, Internet access, and potentially many multimedia applications become a real fact. WiMAX is an IEEE standard based technology responsible for bringing the Broadband Wireless Access to the world as an alternative to wired broadband. It provides an appropriate solution to certain rural access zones that are today prevented from having access to broadband internet because of cost consideration. Figure-1.2 Cellular and wireless network evolutions Figure-1.2 shows the WiMAX standard as a convergence of two modern wireless and cellular systems. In other words, WiMAX fills the gap between the two emerging trends 4

5 of the future generation. In a fixed wireless communication, WiMAX can replace the telephone company's copper wire networks, the cable TV's coaxial cable infrastructure while offering Internet Service Provider services. The WiMAX standard e provides fixed, nomadic, portable and mobile wireless broadband connectivity without the need for direct line-of-sight with the base station. Hence WiMAX system which is becoming the perfect solution to meet the current demands of the future wireless networks thereby provides the tough competition to the existing 3G standards [3] Antenna Diversity Diversity is a powerful communication transmitter-receiver technique that provides wireless link improvement at relatively low cost. It exploits the random nature of radio propagation by finding independent (or at least highly uncorrelated) signal paths for communication. While dealing with multipath environment, the individual signal path arriving at the receiver faces independent or highly uncorrelated fading. 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 [4]. If one radio path undergoes a deep fade, another independent path may have a strong signal. This phenomenon of independent fading in various paths can be exploited as an advantage to achieve improved performance in wireless communication provided that out of multiple paths, at least one path can be obtained with minimum distortion and maximum signal strength. This phenomenon leads towards the concept of diversity which can dramatically improve the performance over fading channels. In a channel with multiple transmit or receive antennas spaced sufficiently far enough, diversity can be obtained over space known as an antenna diversity. Two kinds of space diversity can be obtained to improve the capacity of the system. Transmit diversity in which multiple transmit antennae are used for the signal transmission which in term results in Multiple Input Single Output (MIMO) diversity (n x 1 system). While receive Diversity in which multiple receive antennae are used for the signal reception which in term results in Single Input Multiple Output (1 x n system). By employing multiple 5

6 antennas at both the sides, the advantages of both the above mentioned techniques can be encountered. This technique is known as MIMO technology. In MIMO, by spatially allocating more and more no. of antennas with sufficient distance, the maximum throughput can be obtained with minimum error rate. If identical data are going to be transmitted through all the antennas, then at least one strong path can be recognized through which data would be received with the lowest errors and that is how the diversity gain can be achieved. Through this implementation of MIMO the error rate can be improved. To improve spatial capacity in terms of improved multiplexing gain, multiple antennas will have to pass multiple no. of information through spatial multiplexing process which is another facilitating feature of MIMO technique Alamouti Coding Space-time coding (STC) is an efficient approach to exploit the enormous diversity offered by the Multiple Input Single Output and Multiple Input Multiple Output. It is used to obtain gains due to spatial diversity via multiple transmit and receive antennas. Moreover, a diversity gain proportional to the number of antennas at both transmit and receive sides can be achieved. One popular representation of these codes is the Alamouti scheme for two transmits antennas [5]. It has been already discussed that the MIMO system improves the performance of the system drastically by exploiting the advantage of antenna diversity in the wireless communication system with multipath scenario. By transmitting the information through multiple transmitter antennas which are placed at a comparable distance, the same signal can travel in a different path and reach towards the receiver with independent amount of fading depending on the channel conditions that it has encountered. So out of two, one path may have offered less fading to data and it can be received with comparatively better accuracy which is what the unique feature of transmit diversity. But the advantage of this feature can be gained unless and until the antennas are placed sufficiently far apart so that there would be no interference among the same signals transmitted by multiple antennas. Now this factor puts the limitation on capacity of the system. Due to some minimum distance requirement between to consecutive antennas, no. of antennas can t be increased 6

7 beyond some limit and hence the diversity gain would be limited to that extent only. Here what the concept of Alamouti coding comes into the picture. In the implementation of Alamouti coding with transmit diversity, prior to transmission of same signals through multiple antennas, they get coded by taking their complex conjugates and then get transmitted. So now if the separation between antennas is getting lowered then also information can t be interfered because of the coding and this is how diversity gain can be increased thereby anticipating the much improved performance. As a whole Alamouti coding with transmit diversity provides enormous time and space diversity to the wireless system [6] OFDM As the Orthogonal Frequency Division Multiplexing (OFDM) is the primary technology used in the WiMAX systems in the physical layer, it is essential to understand the basics of this technology and how it enables high bit rates to be sustained in a wireless environment with NLOS operation. In real-life transmission environments, multipath propagation and echoes from objects lead to the received signals arriving at the destination in a time-delayed fashion. These signals suffer frequency selective fading as a result of the multi-path propagation effects. When a carrier is used to carry high data rates (i.e. a short symbol time), the received signals have enough delay spread to fall into the slots of other symbols thereby causing inter symbol interference. In the case of a single carrier modulation, this type of propagation limits the data rates that can be used in non line-of-sight (NLOS) environments. The technology of OFDM is based on the use of a large number of carriers spread in the allocated bandwidth, with each carrier being modulated by a proportionately lower data rate than would be the case in a single-carrier scenario. OFDM technique theoretically saves the bandwidth about 50% and provides a very robust transmission technique for NLOS environments. 1.3 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 as justified 7

8 from Figure-1.3 which depicts the growth of wireless communication on the scale of time in terms of generations. It is not anymore a backup solution for nomadic travelers but really a new mood naturally used everywhere even when the wired communications are possible. Many technologies evolve then continuously, changing the telecommunication world. 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. Wireless access has been available to us for many years now. Its most visible manifestation has been in the form of wireless LANS and the Wi-Fi hotspots [8]. These allow internet access using universally available Wi-Fi cards or embedded chips in laptops, PDAs, and other devices from airports, hotels, and cybercafés to university campuses and yachts. Figure-1.3 Wireless system generation scenario [7] 8

9 The users can browse the internet; make VoIP calls using software such as skype, access mail, or upload pictures and videos from digital cameras. They can also watch video by streaming from any of the video sources or downloading video files. 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. Now in next generation for wireless communication, mobile terminals will face mass data service. Thus signal process in mobile terminal is needed to economize power, while high spectrum efficiency and wireless data networks reliability should be guaranteed at the same time. 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. 9

10 1.4 Problem Definitions There are two fundamental phenomenon of wireless communication that makes the problem challenging and interesting. First is the phenomenon of fading: the variations in the signal strength, frequency and time delay i.e. phase as well as time-variation of the channel strengths due to the small-scale effect of multi path fading, as well as larger scale effects such as path loss via distance attenuation, shadowing, refraction or reflections by obstacles [9]. Second, unlike in the wired communication in which each transmitter-receiver pair can often be identified as an isolated point-to-point link, wireless users communicate over the air spectrum and there is significant interference between them in wireless communication. The interference can be between transmitters communicating with single receiver (e.g. uplink of a cellular system), between signals from a single transmitter to multiple receivers (e.g. downlink of a cellular system), or between different transmitterreceiver pairs (e.g. interference between users in different cells). The WiMAX networks form a very important part of the wireless rollout of the nextgeneration networks. They also provide a replacement for major wired extensions of broadcast services, broadcast content feeder networks, and news-gathering networks available today by enriching them with the new broadband features. In this way, the WiMAX may be seen as the last mile solution providing very high data rate along with large coverage area [10]. Figure-1.4 shows the present status of WiMAX system in India. Various operators are now looking for the WiMAX technology as the filling bridge between the existing cellular system and the future demand of highest speed communication with lowest errors. Up till now the WiMAX is configures with the traditional way of single transmitter and receiver antenna but it can t exactly form the shape of 4G technology. 10

11 Figure-1.4 WiMAX in India [7] Now is the time when the potential of WiMAX to develop an entirely new generation of applications is at its prime. As discussed in the present scenario of WiMAX system, the maximum research work is done in Single Input Single Output WIMAX system physical layer model and maximum data throughput received accordingly. However in present scenario, during the phase of real time voice or image transmission through WiMAX system, the available Bit Error Rate and Signal to Noise Ratio and hence capacity of the systems are serious limitations for real time implementation. So in 4G transmission system, link reliability and maximum data throughput is the need for transmitting voice as well as image at high speed. Implementation of antenna diversity techniques along with OFDM technique is one of the promising solutions for this. But very few resources are available in which the modeling and critical comparative analysis of WiMAX system with antenna diversity such as Single Input Single Output, Single Input Multiple Output, Multiple Input Single Output and Multiple Input Multiple Output along with Alamouti coding have been done. 11

12 Very few results for simulating and modeling of WiMAX system are available for real time data transmission (such as image and speech) to achieve the lower Bit Error Rates, higher Signal to Noise Ratio and higher system capacity. 1.5 Contribution of Research Work to the Problem Definitions 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 first phase of this research work deals with the analysis of the most recent wireless networking technique; WiMAX along with its physical layer functioning which is based on the Orthogonal Frequency Division Multiplexing technique. Despite being a nearly 50-year-old concept, it is only in the last decade that OFDM becomes the choice of modem in wireless applications. One of the biggest advantages of an OFDM modem is the ability to convert dispersive broadband channels into parallel narrowband sub channels, thus significantly simplifying equalization at the receiver end. The basic OFDM technique along with advanced antenna structure i.e. MIMO principle is used to increase the system capacity by reducing the effects of ISI. First of all, the simulation and performance analysis of OFDM technique will be carried out for the physical layer functioning of WiMAX system. Then after the modeling of physical layer i.e. single antenna WiMAX system will be carried out and simulation results will be displayed mainly in terms of input data, coding techniques as per IEEE standards, digital modulation techniques, OFDM technique, channel SNR and Bit Error Rate. Another aspect of this research work deals with the simulation and performance analysis of various Diversity techniques. With the transmit diversity, the space time coding i.e. Alamouti coding would be implemented so as to increase the capacity of the system with low bit error rates. Also comparative analysis of single antenna system and multiple antennas systems will be carried out for the successful modeling, simulation and performance analysis of WiMAX system. To improve the bit error rate and the capacity of the WiMAX system, in the final phase the various antenna diversity techniques are to be implemented in the WiMAX model 12

13 with the Alamouti coding scheme. The performance of the WiMAX model would be evaluated by means of real time transmission of image and speech signals. 1.6 Objectives The objectives of the present research work include the performance analysis of following points: a. 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. b. To model the complete WiMAX system according to the IEEE standards. c. To study the various types of antenna diversity techniques for mitigating one of the most challenging and interesting problem of wireless communication i.e. effects of small scale as well as large scale fading. d. 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 e. To derive and model the effects of various efficient wireless channels for getting the utility of them as efficient wireless channels in terms of bit error rate with respect to signal to noise ratio. f. 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. g. To feel the virtual reality of WiMAX system by modeling the WiMAX IEEE standard with MATLAB simulink for real time data i.e. image and speech analysis. This objective can be undertaken by processing the whole flow in the following way: 13

14 Thorough analysis of WiMAX model by end to end simulation of inner parameters of basic sub blocks and deciding final throughput by input output characteristics. Implementation of various antenna diversity techniques, Alamouti coding and OFDM in the WiMAX model for the improvement of system performance in terms of bit error rate and capacity. Real time data implementation in WiMAX system by real time transmitting and receiving the signals such as image and speech inputs. The achievement of improved WiMAX system performance under real time data scenario with the implementation of antenna diversity techniques. Ultimately the main objective of this research work is to simulate, design and model the most sophisticated future generation wireless networking standard i.e. WiMAX system with the implementation of antenna diversity techniques along with Alamouti coding by observing the improvement in BER and system capacity with the real time transmission of image and speech input signals. The mentioned objective can be graphically described as part of summery by means of Figure-1.5 which shows the flow of research in brief. Figure-1.5 Flow of research 14

15 Basically Figure-1.5 indicates the requirement of current era along with the existing status of current technology. In today s world, the highly required feature of any system design is to achieve the highest capacity with lowest error rate. The blocks outside the red boarder indicate the requirement of future generation technology and the challenges coming in the path to achieve those requirements. Right now the focus is on designing and implementation of efficient 4G technology which should support data as well as real time image and speech signals. To develop such futuristic technology, the fearful challenges are the presence of fading and interference of the multipath environment. This research work basically overcomes the multipath limitations and create the most sophisticated and efficient platform for the modeling of one of the most emerging IEEE standard; WiMAX for wireless communication. For such development, this research has dealt with many phenomenons such as modeling and simulation of WiMAX system, investigation of quality based algorithms for antenna diversity techniques along with simulation of efficient wireless channels and implementation of the same in WiMAX system with real time image and speech transmission. These all processes which have contributed in the problem domain are indicated inside the red boundary which is what the main objective of the complete research work. 1.7 Methodology Figure-1.6 shows the basic design flow of the complete research work as a part of design methodology. The research work has been initiated by taking literature review and analysis of most innovative wireless networking standard i.e. WiMAX. Then through modeling and performance analysis of WiMAX system, some of the limitations have been encountered that limits the system performance in terms of capacity and error rate which led to the implementation of various kinds of diversity techniques into it. So in the next phase, the quality based algorithms of antenna diversity have been developed and implemented in WiMAX physical layer along with time and frequency diversity. Finally the comparative analysis of complete WiMAX system along with diversity has been undertaken by real time transmission of image and speech signals with efficient wireless channels. 15

16 Literature Review and Analysis of IEEE Standards Modeling and Performance Analysis of Traditional WiMAX System Performance Analysis of Diversity Techniques Time Space Frequency Implementation of Channel Coding Antenna Diversity Simulation and Performance Analysis of OFDM Technique Designing and Implementation of Quality Based Algorithms for Antenna Diversity Techniques Simulation Results and Comparative Analysis Simulation and Performance Analysis of Efficient Wireless Channels Simulation of WiMAX using SISO, SIMO, MISO and MIMO Techniques Simulation Results and Comparative Analysis Modeling of Traditional WiMAX System using Real Time Image and Speech Data Transmission Modeling of WiMAX System with SISO, SIMO, MISO and MIMO Techniques in Noisy and Fading Environments using Real Time Image and Speech Data Transmission Experimental Results and Comparative Analysis Figure-1.6 Methodology 16

17 1.8 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 thesis is organized in five chapters, all of which deal with the logical, analytical and mathematical detailing of every element or sub system of the WiMAX structure by taking into account standard specifications provided by IEEE as well as literature review of the corresponding theoretical aspects for its modeling and designing perspective. The present chapter discusses the meaning and significance of primary terms used through out the thesis. In order to understand the objectives and the applications of this research work, the basic understanding of modeling and simulation of system along with an overview of WiMAX system, Antenna Diversity techniques, Alamouti coding as well as OFDM system have been elaborated in the chapter. For making the clear distinction between the present status and future demands of wireless communication, a comparison between WiMAX and other wireless systems is also included. Further the problem domain and contribution of thesis to the problem domain have been included by considering implementation of antenna diversity techniques in WiMAX system. Finally the whole methodology of research work in terms of flow chart has been included to achieve the set goal. The remaining four chapters discuss the modeling and simulation of WiMAX system based on IEEE standard and implementation of various antenna diversity algorithms in it. Chapter 2 includes the complete theoretical analysis of the WiMAX system along with the comparative study of the system with other systems i.e. Wi-Fi and Cellular systems. The different WiMAX standards along with the features have been discussed. At the final phase of this chapter, this performance analysis has been implemented in a form of WiMAX modeling. The traditional model of WiMAX system has been implemented according to the IEEE standard as a core part of this chapter in which the effect of time diversity can be observed by simulating the model with and without the presence of FEC coder. Moreover, the effect of frequency diversity can be analyzed by changing the cyclic prefix of OFDM sub block of the WiMAX system. As the most 17

18 important remark, it can be deduced from the modeling of traditional WiMAX that the performance of the system in terms of BER is totally dependant on channel SNR and its not possible to increase the SNR beyond certain limit to improve the performance for the distinct level. This limitation becomes the motivation for the designing of chapter 3. Chapter 3 introduces performance analysis of various Antenna Diversity Techniques as well as frequency diversity technique i.e. OFDM. The main limitation of WiMAX deduced from second chapter that its performance is bounded to channel SNR range. This limitation has been overcome with the implication of space diversity and that is central idea of this chapter. The use of multiple antennas at the transmitter and/or at the receiver in a communication link opens a new dimension in reliable wireless communications, improving the performance of the system substantially. The core idea in the MIMO transmitter is STC in which signal processing in time is completed with signal processing in the spatial dimension by using multiple spatially distributed antennas at both link ends. By means of multiple antennas at the transmitter and/or at the receiver side, the performance of the system will be improved by reducing BER at a fixed SNR. This chapter includes the MATLAB algorithms and simulations of different antenna diversity techniques. As a second part the mathematical modeling of antenna diversity with Alamouti coding has also been analyzed. Also the effect of changing modulation order over system BER has been observed. at last with the analysis of OFDM which is the base of physical layer of WiMAX system, the 50% of the bandwidth can be saved with the orthogonal principles. Chapter 4 deals with the designing, implementation and simulation of quality based algorithms of WiMAX system along with the effect of time, frequency and antenna diversity techniques. In this chapter, the SNR bound limitation of traditional WiMAX system has been overcome by the implementation of antenna diversity algorithms. Through this the straight forward improvement in system performance in terms of BER can be obtained with diversity implementations. In the later phase of the chapter, multiple no. of modulation techniques have been implemented in the physical layer of WiMAX system with diversity and their comparative performance evaluation has been obtained. 18

19 Similarly by changing the different values of cyclic prefix, the effect of frequency diversity has also been elaborated. As a whole this chapter evaluates the various effects of different diversities and their parameters over BER of WiMAX system so as to derive the optimum values of the same for the real time operation of WiMAX system. Chapter 5 includes the most important part rather main goal of the research work i.e. real time modeling of the whole WiMAX system by passing image and speech signals along with the implementation of time, frequency and antenna diversity. In the first phase the traditional WiMAX modeling with single transmitting and receiving antenna has been undertaken by considering the optimized values of each and every sub systems which form the complete WiMAX architecture according to IEEE standards. With this the innovative touch to the complete model has been given by passing the real time image and speech signals through it. In the next consecutive phases, the effect of antenna diversity with/without Alamouti coding over system BER has been observed with again real time image and speech transmission. As a whole at the end of this chapter, the complete WiMAX system modeling can be obtained with the most innovative and efficient approach with lowest error rate. Finally, the concluding remarks and future enhancement are summed up in Chapter 6 and the number of presentations and publications followed by references in appendix A and B respectively.. 19