Space-time coding for receive switch and stay combining

Switch and stay diversity combining offers a substantial complexity reduction at the cost of modest performance degradation compared to systems implementing selection diversity. In this work, the design and performance of space time coded multiple input multiple output (MIMO) systems employing switch and stay combining at the receiver, with two antennas, is considered. Assuming known channel at the receiver, a novel switching algorithm is proposed and an upper bound on the pairwise error probability (PEP) is derived. Based on this upper bound, the optimal switching threshold is derived and it is shown that full diversity is achieved when the optimal switching threshold is used. For the case when the channel has to be estimated at the receiver, a minimal complexity training scheme suitable for both switching and channel estimation is described, where it is shown that full diversity is still achievable. By comparing the PEP expressions for the system with perfect channel knowledge at the receiver against the system with imperfect channel knowledge, the power distribution between the training and the data space-time (ST) codewords is optimized to minimize the loss suffered due to channel estimation. Simulation results have also been included to corroborate our results.