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A unifying theory for uplink and downlink multiuser beamforming

: Schubert, M.; Boche, H.


Institute of Electrical and Electronics Engineers -IEEE-, Switzerland Section:
Accessing, transmission, networking. Proceedings : 2002 International Zurich Seminar on Broadband Communications, February 19 - 21, 2002, ETH Zürich, Switzerland
Piscataway: IEEE Operations Center, 2001
ISBN: 0-7803-7257-3
International Zurich Seminar on Broadband Communications (IZS) <17, 2002, Zürich>
Conference Paper
Fraunhofer HHI ()
adaptive antenna arrays; array signal processing; cellular radio; crosstalk; dispersive channels; iterative methods; matrix algebra; minimisation; multiuser channels; personal communication networks; power control; statistical analysis; telecommunication control; multiuser beamforming; spatially dispersive channels; frequency flat channels; base station; adaptive antenna array; second-order statistics; iterative optimization; crosstalk matrix; cellular communication system; personal communication system; power minimization; signal-to-interference ratio; sir

The problem of multiuser beamforming and power control for spatially dispersive, frequency flat channels is addressed, assuming that the base station is equipped with an antenna array and knows the second-order statistics of the channel. There is an interesting duality between the uplink and the downlink problem. In particular, it is shown that both cases can be solved efficiently by an iterative optimization scheme, wherein the conventional uplink beamformer plays a central role. The antenna weights that solve the uplink problem also solve the more complicated downlink problem. The reason for this can be found in the special structure of the crosstalk matrix coupling all users. This leads to an elegant theory, which may also prove useful for solving related problems.