Maximal-Ratio-Combining Array Beamformer Assisted by a Training Sequence for Space Division Multiple Access in Power-Limited Channels

This paper describes a nonblind digital beamformer for SDMA (space division multiple access) systems used when channels are power-limited. An array antenna with many elements is usually required to obtain high antenna gain for the reception of a low-level desired signal and the degree of freedom for the spatial discrimination of many users using the same frequency. The proposed beamformer is designed for such array antennas by employing the combination of a multibeam former and a maximal-ratio-combining (MRC) technique. The MRC technique is extended to a nonblind combiner that uses a training sequence contained in the desired signal. Basic analysis and numerical simulations of its performance, under the power-limited condition and with fixed user terminals, show that the speed and robustness of desired-signal acquisition and undesired-signal suppression may outperform recursive-least-squares (RLS) beamformer with less computation, when it is applied to an array antenna with many elements. key words: digital beamforming, smart antenna, adaptive an-