Sensing-Saturated Throughput Performance in Multiple Cognitive CSMA/CA Networks

A common scenario of cognitive radio system consists of a primary network and a secondary network. In our paper, we generalized the scenario to a primary network with the coexistence of multiple secondary networks. An approximate analytical formulation of the saturated throughput of multiple secondary cognitive carrier sense multiple access with collision avoidance (CSMA/CA) networks in the presence of a primary network is presented. Each of these secondary cognitive networks uses a quiet period in a superframe structure to sense the primary network. The longer the sensing time, the lower the probability of false alarm for a fixed detection probability. Numerical results of the saturated throughputs of two secondary cognitive CSMA/CA networks corresponding to typical parameter values are presented. These values are derived from IEEE 802.11n MAC and WiMedia MAC. These results show that the saturated throughputs of these networks can be maximized for certain probabilities of false alarm with sufficient protection of the primary network. These probabilities of false alarm give rise to the corresponding sensing times for these secondary cognitive networks. It is also shown that for some scenarios, the saturated throughputs of these cognitive networks with sensing can be significantly better than those without sensing. The effects of varying the data rates of these networks are also studied.