DF-AF selection MIMO relaying with orthogonal space-time block codes in wireless networks

DF-AF selection MIMO relaying, where the relay equipped with multiple antennas can adaptively switch between decode-and-forward (DF) protocol and amplify-and-forward (AF) protocol according to its decoding state of the source message, is investigated in cooperative networks. We consider orthogonal space-time block coded transmission for a DF-AF selection MIMO relaying system in Rayleigh fading environment, and a closed-form expression of the outage probability valid at arbitrary SNR is derived. In addition, the diversity order is obtained based on the expression. We also obtain the closed-form expressions of the outage probability and the diversity order for AF MIMO relaying scheme and DF MIMO relaying scheme. Theoretical analysis which has been further verified through Monte-Carlo simulations demonstrates that DF-AF selection MIMO relaying has better outage performance than AF MIMO relaying and DF MIMO relaying.