Optimal Transmit Antenna Selection Rule for Interference-Outage Constrained Underlay CR

Transmit antenna selection (TAS) is a low hardware complexity multiple antenna technique that exploits spatial diversity to improve the performance of an interferenceconstrained cognitive radio (CR) system. In the underlay access mode of CR, the choice of the transmit antenna depends on the link between the secondary transmitter (STx) and its receiver, the interference link from the STx to the primary receiver (PRx), and also the interference constraint imposed on the CR system. We propose a novel selection rule called the lambda-weighted interference indicator rule for an underlay CR system that is subject to the interference-outage probability constraint, which constrains the probability that the interference power at the PRx exceeds a threshold. This general constraint also encompasses the widely studied peak interference power constraint. We prove that the proposed rule minimizes the average symbol error probability (SEP) of the CR system. It applies to a general class of fading models with continuous probability distributions and many constellations, and outperforms the many selection rules studied in the literature. We analyze its SEP, and present several insights about its novel structure and behavior.