Modeling and analysis of an opportunistic transmission scheme based on channel quality information in multi-channel cognitive networks

This paper considers the problem of cognitive access to channels of primary users in a hierarchical network with multiple practical time varying channels. The proposed access strategy is not only based on the sensing about the occupation of the channel by the primary user, but also based on the channel state of the secondary user. We have established a new and more meaningful performance metric to measure secondary user´s total throughput among channels, rather than just the channel occupation rate. The optimization objective of cognitive access is designed to maximize the total throughput among multiple channels subject to collision constraints used for primary users protection. It is shown that our proposed algorithm can achieve higher throughput under tight collision constraints through grasping the access opportunities which have good channel qualities. Numerical results are also presented to validate the theoretical analysis and the expressions of algorithm parameters. This paper shows that the total throughput can be improved significantly by introducing the new access strategy, which takes the advantage of access opportunities of the channel in time domain when it is free and of high quality.