Feedback Reduction for MIMO Broadcast Channel with Heterogeneous Fading

TL;DR

This paper introduces a cluster-based feedback scheme for MIMO broadcast channels with heterogeneous user fading, significantly reducing feedback load while maintaining near-optimal sum rate performance.

Contribution

A novel cluster-based feedback method that adapts to heterogeneous user SNR distributions, optimizing feedback efficiency and preserving multiuser diversity.

Findings

Achieves feedback load reduction without substantial sum rate loss.

Full multiuser diversity is attainable with large user numbers.

More efficient than conventional feedback schemes.

Abstract

This paper considers feedback load reduction for multiuser multiple input multiple output (MIMO) broadcast channel where the users' channel distributions are not homogeneous. A cluster-based feedback scheme is proposed such that the range of possible signal-to-noise ratio (SNR) of the users are divided into several clusters according to the order statistics of the users' SNRs. Each cluster has a corresponding threshold, and the users compare their measured instantaneous SNRs with the thresholds to determine whether and how many bits they should use to feed back their instantaneous SNRs. If a user's instantaneous SNR is lower than a certain threshold, the user does not feed back. Feedback load reduction is thus achieved. For a given number of clusters, the sum rate loss using the cluster-based feedback scheme is investigated. Then the minimum number of clusters given a maximum tolerable sum rate loss is derived. Through simulations, it is shown that, when the number of users is large, full multiuser diversity can be achieved by the proposed feedback scheme, which is more efficient than the conventional schemes.