A novel Sense-Transmit-Wait strategy for coexistence of Cognitive Radio networks with IEEE 802.11 WLANs

Detection of spectral white space and the adoption of optimal secondary user transmission policies are the two crucial aspects of a Cognitive Radio system. In this paper we study the problem of optimal utilization of time domain holes in an unsaturated IEEE 802.11 network. We also design a scheme for the coexistence of a secondary system with an IEEE 802.11 network such that it does not affect the Medium Access Control (MAC) layer behavior of the network by mitigating the infamous “Capture Effect”. Specifically, we propose a Sense-Transmit-Wait strategy which allows the secondary user to effectively decide how often to transmit, when to transmit and the duration for which to transmit while adhering to strict interference constraints imposed via an upper bounded Probability of Collision (p0). Through extensive simulations and analysis of real world 802.11 packet captures, we demonstrate the ability of our proposed system to successfully setup a cognitive network and deliver a significant throughput enhancement.