Exploiting group structure in MAC protocol design for multichannel ad hoc Cognitive Radio Networks

The design of an efficient Medium Access Control (MAC) protocol for multichannel ad hoc Cognitive Radio Networks is an important problem and has been the topic of extensive recent research. In this paper, we present the design and performance evaluation of a protocol, Group MAC (GMAC), which is customized for a situation that commonly arises in ad hoc networks: the network consists of multiple groups of nodes such that a large fraction of the traffic of each node needs to be sent to other nodes of its own group. Some examples are: (a) units (e.g., platoons) in a military ad hoc network, (b) divisions in an emergency or disaster relief network, (c) departments in a corporate or university network. Our protocol requires each secondary node to have only one narrowband transceiver, does not rely on a control channel and incorporates a novel technique for dynamically balancing the traffic load of secondary nodes across the set of free channels. We analyze the stability region of the protocol using a queuing theoretic framework. Our extensive simulations show that a large fraction of the bandwidth unoccupied by primary users is utilized by the GMAC protocol for data transmissions.

I. Introduction

Traditionally, government agencies have been allocating radio spectrum by assigning exclusive licenses to users to operate their networks in different geographical regions [1]. However, this has led to an artificial spectrum scarcity, wherein most of the usable radio spectrum is allocated, but underutilized [7]. Cognitive Radio Networks (CRNs) are emerging as a promising solution to this dilemma; in these networks, there are two types of spectrum users-primary users (PUs), which have prioritized access to channels, and secondary users (SUs) that detect and use “spectrum holes”, i.e., chunks of spectrum that are currently not in use by PUs [1]. The design of an efficient Medium Access Control (MAC) protocol is crucial in order to ensure high utilization of the free spectrum by SUs, its effective sharing among different SUs and the provision of a high Quality of Service (QoS) (e.g., throughput, delay) to SUs [6]. In particular, the design of a MAC protocol for multichannel ad hoc CRNs is an important problem and has been the topic of extensive recent research (a literature review is provided in Section II).