Successive convex approximation for rate maximisation in cooperative multiple-input–multiple-output-orthogonal frequency-division multiplexing systems

In this study, the authors propose a continuous rate and power allocation algorithm for multiuser downlink multiple-input-multiple-output orthogonal frequency-division multiplexing systems with coordinated multi-point transmission. The optimisation problem is formulated as a weighted sum-rate maximisation problem subject to per-antenna power constraints across multiple cooperating base stations (BSs). The practical consideration of the per-antenna power constraint limits the average transmit antenna power which indirectly controls the inherent issue of high peak powers in OFDM. The proposed algorithm employs a successive convex approximation (SCA) technique to dynamically allocate powers to multiple co-channel user terminals. They provide a convexity proof of the transformed optimisation problem and they show that the proposed algorithm converges to a unique solution. They compare the proposed SCA algorithm with two alternative approaches: (i) iterative waterfilling (IWF) and (ii) zero-forcing beamforming (ZFB) with semi-orthogonal user selection under both per-antenna and per-BS power constraint scenarios. Their simulation results highlight that the proposed SCA algorithm outperforms the existing IWF and ZFB in noise-limited environments under both power constraint scenarios.