Comparative Analysis of Various Cooperative Communication Schemes

Abstract

Whenever size, power, or other constraints preclude the use of multiple transmit antennas, wireless systems cannot benefit from the well-known advantages of spacetime coding methods. Cooperation between wireless users has been proposed as a means to provide transmit diversity in the face of this limitation. This thesis firstly analyse a network with a sender, a destination and a third station acting as a relay is analysed. Different combining methods and diversity protocols are compared. The relative distances between the relay and the stations has a large effect on the performance, which shows that when the relay is midway on the link of source to destination, best performance is achieved. It is then extended by increasing the number of relays, which shows that as number of relay increases system performance improves significantly. Secondly in this thesis Cooperative communication is performed with various well-known codes like convolutional code, punctured convolutional code and Turbo code. Using Convolutional code with cooperative communication provides full diversity and excellent coding gain. Punctured convolutional increasing the rate of the code. Coded cooperation using punctured convolutional code generally performs better than other cooperative methods for moderate to high SNR. Turbo code offer better performance than any of the other codes at very low signal to noise ratio. The analysis of turbo code is then performed using EXIT chart which is mainly influence by SNR, size of interleaver,code polynomail and code rate. Finally, on this basis code is designed and used with cooperative communication. Almouti code is a special code because it is the only STBC with rate 1. Using Alamouti codes shows that AF and DF protocols improves their performs and solves the problem of bad performance at low SNR. Thus it is concluded that cooperative communication with channel coding is better then cooperative communication without channel coding in terms of BER and SNR performance, which overall increase system performance.