Shaojie Zhang, Haitao Zhao, Shan Wang
Jan 5, 2017
The tradeoff between decreasing interference to primary user (PU) and increasing secondary user's (SU's) throughput is of great importance for cooperative sensing in cognitive radio networks. Non-ideal spectrum sensing in PHY and multiple SUs' access contention in MAC jointly impact SUs' transmission and the tradeoff. In this study, the authors investigate the joint impact from a cross-layer perspective. First, they quantify the reliability of cooperative sensing and compute SUs' transmission probability under the conditions of non-ideal sensing and access contention. Closed-form expressions of the interference probability to PU and SUs' throughput are derived. Specially, two widely-used contention-based MAC protocols, i.e. slotted Aloha and distributed coordination function, are studied. Then, they formulate the sensing-throughput tradeoff problem by using interference probability to PU, rather than the detection probability, as the constraint. Finally, a 2-dimension search algorithm is proposed to obtain the optimal solution, including the optimal fusion rule, sensing duration and detection threshold. Simulation results validate the outperformance of the cross-layer scheme. They also demonstrate how the optimal solution varies with some key parameters, i.e. PU's signal-to-noise ratio and the number of contending SUs.