We consider transmit antenna selection (TAS) in cognitive multiple-input multiple-output (MIMO) relay networks, as an interference-aware design for secondary users (SUs) to ensure power and interference constraints of multiple primary users (PUs). In doing so, we derive new exact and asymptotic expressions for the outage probability of TAS with maximal ratio combining (TAS/MRC) and with selection combining (TAS/SC) over Rayleigh fading. The proposed analysis and simulations highlight that TAS/MRC and TAS/SC with decode-and-forward relaying achieve the same diversity order in cognitive MIMO networks, which scales with the minimum number of antennas at the SUs. Furthermore, we accurately characterize the outage gap between TAS/MRC and TAS/SC relaying as a concise ratio of their array gains.
Yeoh, P. L., Elkashlan, M., Kim, K. J., Duong, T. Q., & Karagiannidis, G. K. (2016). Transmit Antenna Selection in Cognitive MIMO Relaying with Multiple Primary Transceivers. IEEE Transactions on Vehicular Technology, 65(1), 483-489. https://doi.org/10.1109/TVT.2015.2392753