Subspace Estimation and Decomposition for Hybrid Analog-Digital Millimetre-Wave MIMO systems

TL;DR

This paper presents a distributed subspace estimation and decomposition method for hybrid mmWave MIMO systems, enabling efficient channel estimation and precoding with significantly fewer RF chains, reducing cost and power consumption.

Contribution

It introduces a novel distributed Krylov subspace-based channel estimation and a subspace decomposition technique tailored for hybrid mmWave MIMO architectures.

Findings

Achieves comparable performance to fully digital systems

Reduces RF chain count by 4 to 8 times

Demonstrates effective channel estimation using echoing in TDD systems

Abstract

In this work, we address the problem of channel estimation and precoding / combining for the so-called hybrid millimeter wave (mmWave) MIMO architecture. Our proposed channel estimation scheme exploits channel reciprocity in TDD MIMO systems, by using echoing, thereby allowing us to implement Krylov subspace methods in a fully distributed way. The latter results in estimating the right (resp. left) singular subspace of the channel at the transmitter (resp. receiver). Moreover, we also tackle the problem of subspace decomposition whereby the estimated right (resp. left) singular subspaces are approximated by a cascade of analog and digital precoder (resp. combiner), using an iterative method. Finally we compare our scheme with an equivalent fully digital case and conclude that a relatively similar performance can be achieved, however, with a drastically reduced number of RF chains - 4 ~ 8 times less (i.e., massive savings in cost and power consumption).