SWITCH: A Multichannel MAC Protocol for Cognitive Radio Ad Hoc Networks

Cognitive radio (CR) technology will empower wireless devices with the capabilities to dynamically exploit opportunities in both licensed and unlicensed spectra. Thus, the spectrum shortage problem that occurs due to the ever-increasing of wireless devices can be handled. In CR ad hoc network, a secondary user (SU) is allowed to utilize a channel of the primary system provided the channel is idle from primary user (PU) activity. In this environment, the way the SU copes with a sudden appearance of the PU is the most important feature of distributed CR-MAC protocols. In this paper, a multichannel CR-MAC protocol, which reacts efficiently to PU appearance, is developed. The new protocol is named opportunistic Spectrum access WITh backup CHannel (SWITCH). The SWITCH protocol is a decentralized, asynchronous, and contention-based MAC protocol for CR ad hoc networks. The proposed protocol operates over both licensed and unlicensed spectra. In addition, the concept of backup channel is introduced and employed to make the SU extremely robust to the appearance of PUs. The simulation results show that SWITCH accomplishes 91% throughput gain over other CR-MAC protocols.