CR-MAC: A multichannel MAC protocol for cognitive radio ad hoc networks

摘要

This paper proposes a cross-layer based cognitive radio multichannel mediumaccess control (MAC) protocol with TDMA, which integrate the spectrum sensingat physical (PHY) layer and the packet scheduling at MAC layer, for the ad hocwireless networks. The IEEE 802.11 standard allows for the use of multiplechannels available at the PHY layer, but its MAC protocol is designed only fora single channel. A single channel MAC protocol does not work well in amultichannel environment, because of the multichannel hidden terminal problem.Our proposed protocol enables secondary users (SUs) to utilize multiplechannels by switching channels dynamically, thus increasing network throughput.In our proposed protocol, each SU is equipped with only one spectrum agiletransceiver, but solves the multichannel hidden terminal problem using temporalsynchronization. The proposed cognitive radio MAC (CR-MAC) protocol allows SUsto identify and use the unused frequency spectrum in a way that constrains thelevel of interference to the primary users (PUs). Our scheme improves networkthroughput significantly, especially when the network is highly congested. Thesimulation results show that our proposed CR-MAC protocol successfully exploitsmultiple channels and significantly improves network performance by using thelicensed spectrum band opportunistically and protects PUs from interference,even in hidden terminal situations.