Spectral efficient cooperative transmission for half-duplex relay communications

A new transmission protocol using MIMO (Multiple Input Multiple Output) half-duplex relays is proposed to improve the capacity and the diversity gain of uplink relay communication systems. The proposed protocol employs two half-duplex DF (Decode-and-Forward) relays and Alamouti coded 2 x 2 MIMO communication for links between each relay and the destination. A low complexity receiver using maximum ratio combining and Alamouti decoding is introduced to detect the signal of the proposed protocol. Performance is evaluated by theoretical analysis and computer simulations, and the results show that the proposed protocol outperforms conventional IEEE 802.16j systems in terms of ergodic capacity and outage probability.