SLNR beamforming based iterative power allocation in TD-LTE-A downlink

In TD-LTE-A downlink, multi-user beamforming is used to decrease co-channel interference of different users and increase system performance, and Signal-to-Leakage-and-Noise Ratio (SLNR) beamforming algorithm has been proved to have better performance in terms of sum capacity and average BER performance compared with other beamforming algorithms with moderate complexity. In order to further improve the performance, the power allocation algorithm is combined with the framework of SLNR beamforming. Based on the combined algorithm, we can maximize sum capacity and guarantee users' requirements in multiuser downlink scenario with multiple-input-multiple-output (MIMO). The problem is transformed into convex optimization and then solved by geometric programming. Simulation results show that sum capacity of the proposed algorithm is slightly inferior to water-filling algorithm, however, the proposed algorithm can satisfy users' requirement while water-filling algorithm cannot. Then, a sub-optimal algorithm is also proposed to reduce implementation complexity at the cost of 10% sum capacity loss.