Access Delay of Cognitive Radio Networks Based on Asynchronous Channel-Hopping Rendezvous and CSMA/CA MAC

Abstract

As a promising approach to the rendezvous problem in cognitive radio networks (CRNs), a blind rendezvous paradigm has recently spawned various asynchronous channel-hopping (CH) rendezvous schemes that enable any two neighboring secondary users to meet among multiple channels within a finite time, even with no synchronization. However, the rendezvous delay that was derived in existing work is unable to reflect the actual channel access delay performance in multiuser CRNs, as it only relies on hopping patterns of the elaborately designed CH sequences (CHSs) and ignores the impact of network factors (e.g., channel availability and multiuser contention). In this paper, channel access delay is investigated by jointly considering asynchronous CH rendezvous schemes, channel availability, and a medium-access control (MAC) protocol in a single-hop multiuser CRN. To coordinate multiuser contention, a carrier sense multiple access with collision avoidance (CSMA/CA) MAC is adopted by tailoring the IEEE 802.11 distributed coordination function (DCF) properly to the operation features of existing asynchronous CH rendezvous schemes. The channel access delay is analyzed based on a modified Bianchi model and an absorbing Markov chain model, which captures the aggregate effect of hopping patterns of CHSs, the dynamic nature of channel availability, and the behavior of the MAC protocol. The analytical results are verified through extensive simulations. Both simulation and analytical results reveal that the rendezvous delay in existing asynchronous CH rendezvous schemes is insufficient to ensure satisfactory channel access delay in multiuser CRNs.