Opportunistic Multi-channel MAC protocol for Cognitive Radio Networks

Due to the fast development of the wireless applications and services, cognitive radio networks have been proposed to dynamically accessing the spectrum to efficiently improve the spectrum utilization. Cognitive Radio users or secondary users (SUs) should enter the licensed channels only when the primary users (PUs) arc absent. They also have to release the licensed channel whenever a primary user occupies the channel, in order to limit the interference to the primary users. Managing the spectrum access of the cognitive users is the main rule of the medium access control (MAC) layer. Due to the time varying channel availability this introduces a nontrivial number of design challenges to the MAC layer (e.g. multichannel hidden terminal problem, SUs synchronization, and achieving high throughput with limiting interference to the PUs). In this paper a new MAC protocol for ad hoc networks, named ACAP-MAC protocol, has been proposed based on seasonal autoregressive integrated moving average (SARIMA) forecasting technique. The proposed protocol provides a reliable forecast for the off state time of the primary users to be opportunistically utilized by secondary users. The OPNET Modeler network simulation tool is used as a powerful tool to collect and show statistics that verify the reliability of the proposed MAC protocol. The simulation results show that the proposed MAC protocol offers high throughput and low collision rate.