QoS‐driven spectrum sharing game in cognitive radio systems: a variational inequality approach

Cognitive radio CR technology aspires to the efficient usage of the limited and underutilised radio spectrum resources. Constituting a flexible and intelligent network, the unlicensed secondary users SUs may coexist with the licensed primary users PUs, under the prerequisite not to disturb their communication. A spectrum interweave CR system is considered, where SUs coexist with a single PU pair in a fading environment. The SUs are allowed to transmit their data 'peacefully', only with the absence of PU's transmission, by exploiting spectrum holes of the licensed band. A quality of service QoS-driven spectrum sharing scheme is proposed. Specifically, the problem of licensed spectrum sharing among SUs is formulated as a novel non-cooperative game with a view of maximising the effective capacity of each SU that has specific delay QoS requirements, subject to the coupled constraint of the available bandwidth. Because this game constitutes a generalised Nash equilibrium problem, we apply the variational inequality framework to solve it. The variational solution is proven to be unique, and it is obtained through a distributed iterative algorithm. The performance of the proposed scheme is evaluated through numerical simulations, and the results confirm the importance of incorporating the delay QoS factor in spectrum sharing studies. Copyright © 2014 John Wiley & Sons, Ltd.