FDD FORWARD LINK BEAMFORMING METHOD FOR A FDD COMMUNICATIONSSYSTEM

摘要

A highly bandwidth-efficient communications method is disclosed, to maximi ze the signal-to-interference-noise ratio (SINR) of transmissions from a base station to a remote station in a wireless communications system. The method is used for base stations that have a plurality of antenna elements that are capable of spatial beam steering by altering the relative phase of transmission of signals from the respective elements. The method of the invention is based on providing calibration frames that sequentially transmit calibration bursts from the respective antenna elements for a particular destination remote station. The calibration bursts include a plurality of to ne frequencies arranged in a distinctive orthogonal frequency division multiplexed pattern unique to the base station. The unique pattern enables a remote station to distinguish the base station's bursts from other signals present in a crowded area. The distinctive orthogonal frequency division multiplexed pattern can be a Hadamard code pattern, for example. Th e plurality of calibration bursts are part of a transmission frame having a reference phase. The remote station receives the calibration bursts and measures values related t o the relative phase difference between the calibration bursts and the reference phase. The remote station also measures the SINR of the received bursts. The measured values a re then prepared as a sampling data message that is transmitted by the remote statio n back to the base station. The base station then calculates therefrom a beam steering correction to modify the relative phase difference. This beam steering correction is then applied to traffic bursts that are respectively transmitted from the plurality of anten na elements at the base station, to steer the plurality of traffic bursts toward the remote station. The beam steering correction steers the traffic bursts to maximize the signal-to - interference-noise ratio (SINK) of the traffic bursts at the remote station.