Beamforming matrix quantization with variable feedback rate

Abstract

We propose a new technique to quantize and feedback the parameters when a beamforming matrix is compressed with the Givens Rotation (GR). We suggest to feedback the parameters with variable feedback rate, and use efficient source coding and codebook to quantize the GR parameters. The variable feedback rate means that the number of bits used to represent the quantized beamforming matrix is based on the value of the matrix itself. And due to the non-uniform distribution of the GR parameters, source coding and code book can be designed to quantize those parameters in a more effective manner. Compared with the fixed feedback rate scheme, the proposed method delivers a better performance without incurring additional feedback bandwidth.

Robust Multi-Antenna Multi-User Precoding Based on Generalized Multi-Unitary Decomposition With Partial CSI Feedback

“…The arbitrary second eigenvectors, including the actual second eigenvector, form a plane normal to the principal eigenvector of SVD. For a general n × n case, by using the definition of the Givens rotations in [19], we need n − 1 eigenvectors, and the last arbitrary eigenvector can be calculated from the n − 1 eigenvectors.…”

“…The complex channel H is first transformed into H = UΛV H using SVD, where Λ ∈ R L×L is a diagonal matrix containing all the singular values λ i in descending order, and both U and V are orthonormal matrices. For GMUD, its matrix R r with prescribed r can be arranged in the form of R r = W H ΛX, where Λ is the same SVD diagonal matrix of H, whereas W and X are unitary matrices defined by the following Givens rotations [18], [19] …”

Efficient Limited Feedback Technique for FDD MIMO Systems

“…Givens Rotation Quantization GR-Q is proposed in [17]. The authors propose a reduction of the feedback overhead by exploiting the unitary property of the precoder matrix V .…”

“…Here, Givens rotation is used to decompose the unitary beamforming matrix. After the decomposition, the receiver only feeds back the GR parameters necessary for the reproduction of the beamforming matrix by the transmitter [17]. The GR approach is adopted in IEEE 802.11ac standard for TxBF mode [2].…”