A Per-User QoS Enhancement Strategy via Downlink Cooperative Transmission Using Distributed Antennas

Abstract

In this letter we address a strategy to enhance the signal to interference plus noise ratio (SINR) of the worst case user by using cooperative transmission from a set of geographically separated antennas Unlike previously reported schemes which are based on either the power control of individual antennas or cooperative orthogonal transmission the presented strategy utilizes the minimum mean squared error (MMSE) filter structure for beamforming which provides Increased robustness to the external interference as well as the background noise at the receiver By iteratively updating the cooperative transmission beamforming vector and power control (PC) the balanced SINR is obtained for all users while the transmission power from each antenna also converges to within the con strained value It is demonstrated that proposed MMSE beamforming significantly outperforms other existing schemes in terms of the achievable minimum SINR