Cooperative diversity in wireless networks based on best relay selection:4th G mobile communication

Transmit diversity generally requires more than one antenna at the transmitter. But many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in multi-user environment to share their antennas and form a virtual multiple-antenna transmitter that allow them to achieve transmit diversity. However, most of proposed methods require distributed space-time coding algorithms which is very critical. We propose a method that provides transmit diversity gain on the order of the number of relays in the network. Our scheme first selects the best relay from a set of M available relays then uses this ldquobestrdquo relay for cooperation between the transmitter and the receiver. The selection of best relay is not required any topology information and is based on local measurements of the instantaneous channel conditions. The theoretic analysis of outage probability shows that our scheme achieves the same diversity-multiplexing tradeoff as achieved by more complex protocols, where distributed space-time coding for M relays is required.