A new method of channel feedback quantization for high data rate MIMO systems

Abstract

In this work we study a Multiple-Input Multiple-Output wireless system where the channel state information is partially available at the transmitter through a feedback link. Based on Singular Value Decomposition, the MIMO channel is split into independent sub-channels which allows separate, and therefore, efficient decoding of the transmitted data signal. Effective feedback of the required spatial channel information entails efficient quantization/encoding of a Haar unitary matrix. The parameter reduction of anparameters is performed through Givens decomposition. We prove that Givens matrices of a Haar unitary matrix are statistically independent. Subsequently, we derive the Probability Distribution Function (PDF) of the corresponding matrix elements. Based on these analyses, an efficient quantization scheme is proposed. 2The performance evaluation is provided for a scenario where the rates allocated to each independent channel are selected according to its corresponding gain. The results indicate a significant performance improvement compared to the performance of MIMO systems without feedback at the cost of a very low-rate feedback link.

Variable-Rate Transmission for MIMO Time-Correlated Channels With Limited Feedback

“…The expression of in (10) contains the term that is not known to the transmitter. To have an estimate of based on the previous bit loading, we can use (10) and the bounds in (11) as in the above discussion to obtain (13) where we have replaced by as before. The above lower and upper bounds depend only on the previous bit loading and can be used to design the quantizer for quantizing the prediction error in Section 4.…”

“…The feedback rate and the number of substreams transmitted is updated periodically without using extra feedback as described in Section 4.2, and a two-bit quantizer is used for quantizing the prediction errors. The quantizer is adapted according to the upper bound of prediction error variance in (13), labeled as 'upper bound', and according to the lower bound ('lower bound'). We have also shown PQB for the case the quantizer is not adapted ('fixed quantizer'), and for the case the bit loading is the integer part of the unquantized bit loading in (3), labeled as 'unquantized'.…”

“…Spatial modulation for MIMO systems with adaptive constellation selection is considered in [11]. Feedback of quantized precoder, power allocation and/or bit allocation is considered in [12], [13]. Successive quantization of power and bit allocation is proposed in [14].…”

Beamforming matrix quantization with variable feedback rate

“…An effort to reduce the amount of information in V was reported in [11][12][13] where a matrix Σ was multiplied with V to form À V , such that the last row of À V consists of only real numbers. Hence, we may re-express (2) as:…”

“…One is codebook based such as the vector quantization (VQ) scheme proposed in [5][6][7][8][9][10], and another is by using the Givens Rotation (GR) [1,4,[11][12][13]. Compared with the GR-based scheme, the VQ approach requires a higher storage, as a set of codebooks is needed for a particular antenna setting.…”