MAC Protocol for Distributed Relay-Assisted Cognitive Radio Networks

Cognitive radio technology can improve spectrum efficiency by allowing potential secondary users (SUs) to use licensed spectrum when primary users (PUs) are absent. How to share and allocate the unoccupied spectrum among SUs directly affects spectrum utilization. Relay-assisted transmitting in cognitive radio networks (CRN) is an effective technology to improve spectrum utilization and increase transmitting range. This paper proposes a MAC protocol for CRN in which relay technology is adopted. According to whether SUs´ state messages are transmitted by certain unchangeable available common channel (ACC) in CRN, two kinds of mechanism for data exchanging are presented. We further propose an ACC assignment algorithm in order to increase SUs system´s total throughput and decrease interference to other neighboring SUs. Furthermore, we present performance results of our mechanism that applied to a SUs system based on opportunistic spectrum access, which proves the benefits of our mechanism.