Incremental decode and forward relaying using distributed space time coding

Distributed space time coding (DSTC) is an efficient way to exploit spatial diversity for cooperative system. In regular cooperative diversity networks, relays forward the source signal to the destination every time regardless of the channel conditions which limits the system throughput. In this paper, we propose an incremental relaying protocol based on decode and forward transmission in conjunction with DSTC to save the channel resources. If the destination requests the help from the relays, they cooperate with each other and decode and forward an Alamouti coded version of their signals. The average bit error probability (BEP) is derived in a closed form expression. Simulations are performed to confirm our theoretical analysis. The effect of the signal to noise ratio (SNR) threshold and the position of relays on the bit error probability are discussed. Moreover, our results show that the proposed scheme offers better performance than incremental-selective DF relaying when the relays are near the source.