Partial relay-based cooperative primary user detection in cognitive radio networks

In order to identify spectrum holes, secondary users (SUs) should detect whether the spectrum band is occupied by primary user (PU). Cooperative PU detection is the most prevalent PU detection method in cognitive radio (CR) networks. Existing cooperative PU detection usually consumes a dedicated reporting channel to share the detection results. This paper proposes a partial relay-based cooperative PU detection scheme that does not require any reporting channels. Our idea is to let the SU with higher signal-to-noise ratio (SNR) sacrifices part of its detection period acting as the relay node to help other SUs. Although the performance of this SU is inevitably impaired, other SUs may benefit from the relay, and performance of the whole CR network can be improved. Moreover, this paper investigates the relay policy of proposed scheme under two criteria. Considering the criterion of balancing detection accuracy, an interesting conclusion that the optimal relay policy merely depends on the SNR gap is derived. Both lower and upper bounds of the optimal relay policy are deduced as well. Considering the criterion of maximizing detection agility, numerical approach to obtain the optimal relay policy is introduced, and the agility gain is also analyzed. Simulation results are provided to verify all conclusions above.