Abstract
In the Alamouti-coded multiple-input multiple-output relay systems, we consider selecting two transmit antennas from all available antennas, at the source and relay respectively, to maximize received signal-to-noise ratio (SNR) at the destination. Since the optimal antenna selection rule is intractable, we propose three suboptimal antenna selection rules (rule one, two and three). While these rules all select two best antennas at the relay to maximize the SNR of relay-destination link. They have different selection criteria at the source. Rule one maximizes the SNR of source-relay link but ignores source-destination link. Oppositely, rule two maximizes the SNR of source-destination link but ignores source-relay link. Rule three considers both links together. We derive the closed-form outage probability expressions of rule one and two, and find an upper bound for the outage probability of rule three. The analysis results show that rule one and two cannot achieve full diversity order, and rule three can. Simulation results verify the analysis results.