Optimal power allocation for multiple input single output cognitive radios with antenna selection strategies

The opportunistic spectrum access technology is one of the most promising methods for alleviating the spectrum scarcity problem, which enables a secondary user (SU) to utilise a primary user spectrum band that is detected idle. However, the throughput achieved by cognitive radios is limited by the interference constraint imposing on the SU. Multiple input single output antenna techniques and antenna selection (AS) techniques are exploited to combat the interference constraint and improve the achievable average throughput of the SU. The optimal power allocation strategy is proposed to maximise the achievable average throughput. Performance analyses for the achievable average throughputs are performed under the maximum channel gain AS strategy, the minimum interference channel gain AS strategy and the ratio AS strategy. It is proved that the optimal transmitted AS strategy is the ratio AS strategy when the optimal power allocation strategy is used. The optimal sensing parameters are designed to further improve the maximum average throughput. Extensive simulation results are conducted to verify this analysis.