Adaptive Feedback for MIMO Beamforming systems


B. Mondal and Robert W. Heath Jr


In Proc. IEEE Int. Workshop on Signal Processing Advances in Wireless Communication (SPAWC), Lisbon, Portugal, July. 11 - 14, 2004.


Multiple-input multiple-output wireless systems can achieve significant diversity and array gain by using transmit beamforming and receive combining techniques. In the literature, quantization techniques for the beamforming vector are designed and optimized assuming a particular channel distribution, commonly uncorrelated Rayleigh. When the channel is not uncorrelated Rayleigh, these quantization strategies result in considerable degradation of signal to noise ratio. In those cases, the spatial and temporal correlations in the beamforming vector are exploited to develop quantization schemes that adapt to the distribution of the channel. Two scenarios are considered - (i) when the feedback rate is fixed and distortion is minimized (ii) when distortion is constrained and rate is minimized. Both the algorithms largely outperform quantization schemes that are based on uncorrelated Rayleigh fading assumption.

Preprint is available here.