A Simple Distributed Antenna Processing Scheme for Cooperative Diversity
  In this letter the performance of multiple relay channels is analyzed for the situation in which multiple antennas are deployed only at the relays. The simple repetition-coded decodeand- forward protocol with two different antenna processing techniques at the relays is investigated. The antenna combining techniques are maximum ratio combining (MRC) for reception and transmit beamforming (TB) for transmission. It is shown that these distributed antenna combining techniques can exploit the full spatial diversity of the relay channels regardless of the number of relays and antennas at each relay, and offer significant power gain over distributed space-time coding techniques. 
Yijia Fan, Abdulkareem Adinoyi, John S Thompson, Halim Yanikomeroglu,   H. Vincent Poor