Joint Beamforming, Power and Channel Allocation in Multi-User and Multi-Channel Underlay MISO Cognitive Radio Networks

In this paper, we consider a joint beamforming, power, and channel allocation in a multi-user and multi-channel underlay multiple input single output (MISO) cognitive radio network (CRN). In this system, primary users’ (PUs’) spectrum can be reused by the secondary user transmitters (SUTXs) to maximize the spectrum utilization while the intra-user interference is minimized by implementing beamforming at each SU-TX. After formulating the joint optimization problem as a non-convex, mixed integer nonlinear programming (MINLP) problem, we propose a solution which consists of two stages.

In the first stage, a feasible solution for power allocation and beamforming vectors is derived under a given channel allocation by converting the original problem into a convex form with an introduced optimal auxiliary variable and semidefinite relaxation (SDR) approach. After that, in the second stage, two explicit searching algorithms, i.e., genetic algorithm (GA) and simulated annealing (SA)-based algorithm, are proposed to determine suboptimal channel allocations. Simulation results show that
beamforming, power and channel allocation with SA (BPCA-SA) algorithm can achieve close-to-optimal sum-rate while having a lower computational complexity compared with beamforming, power and channel allocation with GA (BPCA-GA) algorithm.
Furthermore, our proposed allocation scheme has significant improvement in achievable sum-rate compared to the existing zero-forcing beamforming (ZFBF).

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