Throughput Analysis of the Intermittent DCF for Opportunistic Spectrum Access

Abstract

Recently, the opportunistic spectrum access (OSA) technologies have drawn a lot of the research community attention, because, by utilizing cognitive radio (CR) capabilities, they provide us with solutions to compensate for the spectrum underutilization. The MAC design is an important aspect of this on-going research. In this paper we study the performance of the distributed coordination function (DCF) in the OSA environment, which requires periodic intermissions to the MAC operation for spectrum scan procedures and opportunities identification. We present several modifications to the DCF that render it robust and operational in demanding environments of frequent spectrum scan procedures and low achievable transmission rates. We also present an analytical model for the throughput calculation of the resulted Intermittent DCF, which is based on the Bianchi's Markov model and extends it so as to include the intermittent nature of the OSA environment. The proposed model is validated through simulations. A new parameter, controllable by the CR terminals, is used to optimize the throughput performance in realistic OSA scenarios. Using the presented analytical model we evaluate the performance of the Intermittent DCF under the effect of certain design parameters.