Modeling and analysis of interference in Listen-Before-Talk spectrum access schemes

Spectrum measurement studies have shown that substantial portions of the allocated wireless spectrum are highly underutilized. Frequency-agile radios (FARs) have the potential to make opportunistic use of such spectrum holes without causing harmful interference to users of the allocated spectrum. Toward this goal, we develop a framework for modeling the interference caused by FARs employing spectrum access mechanisms based on the simple ListenBefore-Talk (LBT) scheme. Two variations of LBT are considered: individual LBT, whereby the FARs act independently of each other; and collaborative LBT, whereby the FARs communicate with each other in order to more accurately identify the spectrum holes. Our analysis of the LBT scheme reveals the fundamental interdependencies among key system design metrics and provides a basis for analyzing more complex spectrum access methods. In particular, the analysis of LBT provides a lower bound on the capacity gain achievable by FARs employing spectrum-sharing schemes. Our numerical results show that the individual LBT scheme can provide substantial capacity gains, while even more gain can be achieved using the collaborative LBT schemes. Our analysis suggests that much greater gains should be achievable via spectrum access schemes that incorporate location information and/or more sophisticated group behaviors. Copyright © 2006 John Wiley & Sons, Ltd.