Design and Performance Analysis of Multichannel MAC Protocol for Cognitive WLAN

Dynamic spectrum access (DSA) allows the spectrum to be utilized efficiently through opportunistic access. Cognitive radio (CR) is a technology used to enable DSA. Unlike a wireless local area network (WLAN) that operates in unlicensed band, cognitive WLAN allows CRs to identify spectrum holes in licensed bands and opportunistically use it. DSA makes the design of the medium access control (MAC) layer in the cognitive WLAN challenging. In this paper, we design and carry out performance analysis of IEEE 802.11 DCF based MAC protocol for multichannel cognitive WLAN. Our main contributions are as follows: 1) A Markov chain model for CRs and 2) another Markov chain to model the joint usage of the channel by the licensed users and CRs. These coupled Markov chain models are then solved for stationary probability distribution. Using the above models, we derive throughput and delay of the CRs and study their variation against the number of CRs, the number of channels, and spectrum availability. Theoretical results are validated using simulation and compared with results from existing literature.