Low-Complexity Distributed Spectrum Sharing Among Multiple Cognitive Users

The problem of sharing multiple primary channels among multiple cognitive users is considered. The occupancy of each primary channel is modeled by a continuous time on-off process with exponentially distributed idle (off) period and arbitrarily distributed busy (on) period. Each cognitive user follows a slotted sensing-before-transmission access protocol, with the capability of sensing one primary channel in each slot. To limit the interference to the primary users, the transmissions of cognitive users on each channel are subject to a prescribed collision constraint. In the absence of sensing error, it is shown that a distributed spectrum sharing scheme with low complexity achieves the throughput region under tight collision constraints. Cognitive access with sensing error is also investigated and optimal transmission policy is obtained for the orthogonalized periodic sensing. Packet level simulations are conducted to validate the performance of the spectrum sharing scheme under various channel models as well as perfect and imperfect channel sensing.