The Simulation Of Enhanced Wimax System Using Diversity Alamouti Code

We nowadays live in information era, we broadcast and generate information at the rate never recorded in history of mankind before. This also led to an increasing demand to develop wireless access technologies that support high throughput regardless of the transmission environment. In seriously considering this problem, The IEEE 802.1x committee oversees the development of standards for wireless systems, it formed the 802.16 working group to develop a standards based Wireless Metropolitan Area Network (MAN) solution. One of the results of this research is 802.16d standard, popularly known as fixed WiMAX. This standard specifies the air interface of fixed broadband wireless access (BWA) systems supporting multimedia services and it is also the subject of study in this thesis.A major limitation in wireless application like WiMax is multipath fading effect which occurs when signals arrive at the receiver both directly from the transmitter, and, indirectly, due to propagation through objects or reflection. These signals arrive at slightly different times, with different amplitudes and phases. They sum together constructively and also destructively. The effects of multipath include constructive and destructive interference, and phase shifting of the signal.The target of this thesis is solving the main problems in WiMAX system like: multipath fading, Bit Error Rate (BER), input and received Signal Noise Ratio (SNR) to enhance reliable of system. One of the effective methods is applying the diversity characteristic of Space Time Block Code (STBC), namely Alamouti Code with two transmit and one receive antennas.The efficiency of Alamouti codes is investigated from the bit level perspective. The thesis uses Matlab Simulink in simulating the whole WiMAX system and Alamouti branch. In simulation work, the thesis also gives out the results in comparing between the traditional WiMAX system and the one which deploys Alamouti Code. The results focus on indicating the different values of bit errors, BER and received SNR of two models. Based on such kind of these values, the thesis comes to a conclusion that the model applied Alamouti code always gives a better performance than that traditional one.