COOPERATIVE SPECTRUM SENSING IN COGNITIVE RADIO

In cognitive radio (CR) networks, cooperative spectrum sensing is utilized to improve the sensing performance to avoid potential interference to primary users (PUs) and increase spectrum access opportunities for secondary users (SUs). The problem of how to collect sensing data should be solved for the implementation of the cooperative sensing. A cooperative spectrum sensing process is divided into three phases: individual sensing/detection, reporting/fusion, and data transmission. In the reporting phase, one or more reporting channels are needed to transmit individual sensing results to a fusion center (FC), and global spectrum sensing results are determined at the FC. The number of required reporting channels depends on the number of spectrum sensors or SUs, which relates to reporting channel efficiency and channel scheduling complexity. In the proposed scheme, random access is used to collect the spectrum sensing data of the secondary users during collection period and the length of the collection period is determined adaptively based on the sensing data collected so far. Thus, complex slot management for the collection of the sensing data is not necessary. Also we design a reporting channel scheme based on random access protocols, including slotted Aloha and reservation-Aloha. Performance evaluations in terms of PU detection probabilities and false alarm probabilities considering the proposed reporting channels are presented.