A Review on Relay Selection Techniques in Cooperative Communication

the next generation wireless systems are supposed to handle high data rate as well as large coverage area. It should consume less power and utilize bandwidth efficiently. At the same time, the mobile terminals must be simple, cheap, and smaller in size. In wireless environment, the quality of received signal level degraded due to path-loss and shadowing from various obstacles in propagation path. In addition to this, signal quality suffers from fading due to constructive and destructive interference of multi-path components which makes it difficult for the receiver to extract the message correctly. Effect of fading can be suppressed by diversity technique Diversity can be achieved with the help of Multiple Input Multiple output system (MIMO). However, implementing multiple antennas at wireless terminal is not practical due to size, power, cost, and weight constraints. So, Virtual MIMO known as Cooperative Diversity was introduced. In cooperative wireless networks, it is often the case that multiple sources and multiple relays cooperate to transmit their data to destination. For the cooperative systems, selecting an appropriate relay node is of prime importance. This paper presents the different relay selection techniques to select an appropriate relay to reduce transmission power and to improve overall performance of the wireless network.