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S. Schwarz, R. W. Heath, M. Rupp:
"Adaptive Quantization on a Grassmann-Manifold for Limited Feedback Beamforming Systems";
IEEE Transactions on Signal Processing, 61 (2013), 18; S. 4450 - 4462.

This work considers delay limited adaptive quantization
on the Grassmann manifold of 1-dimensional subspaces
in n-dimensional space. Due to strict delay limits, vector quantization
over multiple time instants cannot be used to exploit
the temporal correlation of the source signal. Instead, a vector
predictive quantization technique is proposed that combines
prediction and differential quantization algorithms to achieve
an efficient quantization of the correlated Grassmannian source.
The proposed predictor is based on adaptive filters to adjust
to the temporal statistics of the source signal. It is shown that
the prediction error in the tangent space associated with the
Grassmann manifold behaves approximately Gaussian, provided
its norm is sufficiently small. The proposed quantization algorithm
is applied to channel state information quantization in
multi-user beamforming wireless communication systems. Large
throughput gains are demonstrated in comparison to independent
quantization, due to the improved quantization accuracy.

Adaptive quantization, limited feedback, quantized feedback, channel state information, Grassmann manifold, multiuser MIMO, LTE, OFDMA

http://dx.doi.org/10.1109/TSP.2013.2270466