Multiple Relay aided Cooperative Communication Scheme

In wireless channel multipath propagation and time variations results in fading. To mitigate fading, diversity is used. In diversity, multiple antennas is used at the transmitter, receiver, or at both ends of transmit and receive side are used which is known as Multiple input Multiple Output (MIMO). But in some wireless networks, due to size of devices multiple antennas at the user terminal is difficult. Thus, cooperative communications (Virtual MIMO) is implemented with one or several single antenna relays to assist the transmission between a source and a destination. In this work, we have used multiple decode and forward relays and have combined the signals at the destination using Maximal Ratio Combining. Even the location of relay plays an important part in our work, in which the relay is located in the middle of source and destination, as it gives the best system performance. We have also considered the relay to be located close to the source thus the quality of source-relay link is good, and the relay can decode the received information. On the other hand, when the relay node is located close to the destination, the system performance degrades. Through simulation results, it is shown the positive role that the relay plays, as it improves significantly the performance of the system and leads to lower BER.