Selection Combining for Differential Amplify-and-Forward Relaying Over   Rayleigh-Fading Channel
  This paper proposes and analyses selection combining (SC) at the destination for differential amplify-andforward (D-AF) relaying over slow Rayleigh-fading channels. The selection combiner chooses the link with the maximum magnitude of the decision variable to be used for non-coherent detection of the transmitted symbols. Therefore, in contrast to the maximum ratio combining (MRC), no channel information is needed at the destination. The exact average bit-error-rate (BER) of the proposed SC is derived and verified with simulation results. It is also shown that the performance of the SC method is very close to that of the MRC method, albeit with lower complexity 
M. R. Avendi and Ha H. Nguyen
cs.IT math.IT