Abstract

The MAC layer protocols utilizing enhanced distributed channel access (EDCA) in the recently published IEEE 802.11-2007 are able to provide differentiated QoS for different traffic types in wireless networks through varying the Arbitration Inter-Frame Spaces (AIFS) and contention window sizes. However, the performance of high priority traffic can be seriously degraded in the presence of strong noise over the wireless channels. The noise problem is further aggravated in wireless mesh networks when packets traverse multiple-hops from source to destination. The noise problem can be mitigated by distributing network traffic across multiple vacant channels to reduce the node density per transmission channel. Although multiple non-overlapped channels exist in the 2.4GHz and 5GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel at anytime. As a result, these networks cannot fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. In this paper, we propose the Power-Controlled Rate-Adaptive MAC (CPCRA) protocol for single transceiver based Cognitive Radio Networks (CRNs) which combines adaptive modulation and coding with dynamic spectrum access. Simulation results demonstrate that CPCRA can achieve better performance in terms of lower delay and higher throughput.

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