Limited Feedback Design for Interference Alignment on MIMO Interference Networks with Heterogeneous Path Loss and Spatial Correlations

TL;DR

This paper introduces a new limited feedback design for MIMO interference networks with heterogeneous path loss and spatial correlations, improving feedback efficiency and preserving degrees of freedom.

Contribution

It proposes a novel spatial codebook and dynamic bit allocation scheme that adapt to interference topology asymmetry, enhancing feedback efficiency in complex MIMO networks.

Findings

Sum degrees of freedom are maintained when feedback scales with SNR.

Dynamic quantization improves feedback efficiency in asymmetric interference.

Scaling coefficient can be reduced in networks with asymmetric interference topology.

Abstract

Interference alignment is degree of freedom optimal in K -user MIMO interference channels and many previous works have studied the transceiver designs. However, these works predominantly focus on networks with perfect channel state information at the transmitters and symmetrical interference topology. In this paper, we consider a limited feedback system with heterogeneous path loss and spatial correlations, and investigate how the dynamics of the interference topology can be exploited to improve the feedback efficiency. We propose a novel spatial codebook design, and perform dynamic quantization via bit allocations to adapt to the asymmetry of the interference topology. We bound the system throughput under the proposed dynamic scheme in terms of the transmit SNR, feedback bits and the interference topology parameters. It is shown that when the number of feedback bits scales with SNR as C_{s}\cdot\log\textrm{SNR}, the sum degrees of freedom of the network are preserved. Moreover, the value of scaling coefficient C_{s} can be significantly reduced in networks with asymmetric interference topology.