Robust downlink power adjustment in cellular communication systems with antenna arrays at base stations

A serious shortcoming of current downlink power adjustment and transmit beamforming methods is that their performance may become severely degraded when the downlink channel correlation (DCC) matrices are known imprecisely at base stations. A new downlink power adjustment method is proposed which provides a substantially improved robustness against imperfect knowledge of the wireless channel by means of maintaining the required quality of service (QoS) for the worst-case channel uncertainty. Our method can be straightforwardly used in a conjunction with any existing transmit beamforming techniques.