Multi-channel medium access control for cognitive radio networks

Abstract

Cognitive radio networks (CRNs) have been regarded as a potential enabling technology to solve the spectrum scarcity due to the fixed spectrum assignment policy and the rapid rise of wireless devices. In CRNs, the spectrum utilization is improved by allowing secondary users (SUs) to opportunistically access the channels which are not occupied by primary users (PUs) in the licensed bands such as “TV white spaces”. Although the CR technology is very attracting to increase overall spectral efficiency, in practice, the CR-MAC design faces up several challenges: control channel design for sharing sensing result and negotiating multi-channel access, coexistence between SUs and PUs, multi-channel operation for network throughput improvement, ease of switching overhead reduction, and radio cost effectiveness. The subject of this dissertation is the design of multi-channel medium access control (MAC) protocols which effectively solve the challenges in distributed or centralized CRNs where each SU has only one half-duplex radio for the minimal radio cost. In the first part, a slow hopping based cooperative sensing MAC (SHCS-MAC) protocol is proposed for the distributed network architecture where the spectrum utilization is improved by allowing different source-destination pairs to simultaneously exchange data packets in different channels. The proposed SHCS-MAC protocol features bootstrapping, multi-channel operation, cooperative sensing, and self-coexistence. Bootstrapping algorithm enables a new SU to join a common hopping based network. Slow hopping based multi-channel operation improves network throughput by enabling concurrent data exchange in different channels on common hopping sequence in which the slot duration can be flexibly selected. Furthermore, for the slow hopping based multi-channel MAC, this thesis presents a cooperative sensing protocol which enables SUs to promptly evacuate from the channel in which a PU appears. Additionally, self-coexistence protoco...