Antenna selection and transmit beamforming optimisation with partial channel state information in distributed antenna systems

This study studies the joint antenna selection and transmit beamforming optimisation in the downlink of a single-cell multi-user distributed antenna system, assuming that all users are delay sensitive and only partial channel state information is available at the transmitter side. Under the constraint of the maximum transmit power of each distributed antenna unit, the authors formulate an optimisation problem to minimise the total power consumption while maintaining the rate outage ratio of each user below a threshold. To mitigate the signalling overhead, they firstly propose an adaptive antenna selection strategy based on the received pilot signal power strength. Then, considering that the remaining transmit beamforming problem may be infeasible and non-convex, a series of relaxation and convex approximation are applied. Finally, they propose a transmit beamforming algorithm based on successive convex approximation and user admission control. Simulation results show that the authors proposed algorithm can achieve a near optimal system performance in both the satisfied user ratio and total power consumption.