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Optimal and sub-optimal resource allocation in multiple-input multiple-output-orthogonal frequency division multiplexing-based multi-relay cooperative cognitive radio networks

The authors consider the resource allocation issue in multiple-input multiple-output-orthogonal frequency division multiplexing-based cooperative cognitive radio networks with the decode-and-forward (DF) as the cooperation strategy. The dual decomposition technique is recruited to obtain an optimal subcarrier pairing, relay selection and power allocation. The optimal resource allocation is performed subject to the individual power constraints in source and relays so that the sum-rate is maximised while the interference induced to the primary system is kept below a pre-specified interference temperature limit. Moreover, because of the high computational complexity of the optimal approach, a sub-optimal algorithm is further proposed. In the sub-optimal scheme, the joint allocation of the resources is performed taking into account the channel qualities, the DF cooperation strategy, the interference induced to the primary system and the individual power budgets. The performance of different approaches and the impact of the constraint values and deploying multiple-antennas at users are explored through numerical simulations.