Performance analysis of decouple-and-forward MIMO relay systems in Rayleigh fading

In this paper we analyze the ergodic capacity and outage probability for a decouple-and-forward (DCF) MIMO relaying system with three nodes and direct link between the source and destination over a Rayleigh fading. The nodes employ multiple antennas and orthogonal space-time block coding (OSTBC). In the DCF relay, the incoming signal is decoupled, amplified and forwarded to the destination. Under assumption that source and destination have full CSI (Channel State Information) for source-relay, relay-destination and source-destination links we derive simple expressions for approximation of the ergodic capacity and outage probability. By means of these approximations it is shown that the system with direct link has better capacity and outage performance. For all considered scenarios the increase of the number of antennas per node results in increase of the ergodic capacity, decrease of the outage probability and increase of the diversity gain.