Resource management in cognitive opportunistic access femtocells with imperfect spectrum sensing

Recently, cognitive radio enabled femtocell is regarded as a promising technique in wireless communications, where the issues of resource allocation and interference management have been investigated intensively. However, spectrum sensing errors are neglected in most of the existing works. In this paper, we propose a resource allocation scheme for orthogonal frequency division multiple access (OFDMA) based cognitive femtocells. The target is to maximize the sum rate of all femtocell users (FUs) under QoS constraints and co-tier/cross-tier interference constraints under imperfect channel sensing. The subchannel and power allocation problem is first modeled as a mixed integer programming problem, and then transformed into a convex optimization problem by relaxing subchannel sharing and imposing co-tier interference constraints, which is finally solved using the dual decomposition method. Based on the obtained solution, an iterative subchannel and power allocation algorithm is proposed. The effectiveness in terms of instantaneous maximum achievable rate of the proposed algorithm as compared with perfect spectrum sensing schemes is verified by simulations.