Performance Analysis of Relay and Combining Methods in Wireless Networks

The quality signal in a wireless transmission occasionally suffers from severe bad channel quality due to effects like fading caused by multi-path propagation. Diversity is one of the methods that used to reduce such effect whereby different samples of the same signal are transferred over essentially independent channels. Cooperative wireless communication it resolves this problem by transmitting a message to a destination with the assistance of a relay. Upon receiving the message from the transmission source, the relay retransmits the message to the destination. Therefore, the combination of the direct and relay transmissions, improves signal reception at the receiver whereby the signal is clearer and better. As such, this paper compares and evaluates the performance of different relays and combining methods in cooperative relay network under noisy and Rayleigh fading channel. This paper examines the Amplify and Forward (AAF) and Decode and Forward (DAF) relay protocols using Maximal-Ratio Combining (MRC), Fixed-Rate Combining (FRC) and Equal-Rate Combining (ERC) methods with BPSK and QPSK modulation based on simulations. The result of the simulations, show that AAF performs better than DAF in terms of Bit Error Rate (BER) without the introduction of error correcting code. Another finding reveals that the relative distances between the relay and the stations affect the performance of BER. The unique of this work is, presented different combining methods with different distance channels between users, distention and relay using different modulation technique. The best performance is achieved when the relay is located in the middle between the source and destination. Finally, the combination of FRC and BPSK shows the best BER performance for SNR up to 20 dB.