Linear Precoding in Cooperative MIMO Cellular Networks with Limited Coordination Clusters

TL;DR

This paper introduces soft interference nulling (SIN), a linear precoding method for cooperative MIMO cellular networks with limited coordination clusters, outperforming traditional techniques like ZF in various scenarios.

Contribution

The paper proposes SIN, a novel linear precoding technique that effectively manages interference in cooperative MIMO networks with limited cluster sizes, especially under overlapping clusters.

Findings

SIN performs at least as well as ZF beamforming.

SIN can outperform ZF with full coordination at moderate SNRs.

SIN achieves higher throughput with larger overlapping clusters.

Abstract

In a cooperative multiple-antenna downlink cellular network, maximization of a concave function of user rates is considered. A new linear precoding technique called soft interference nulling (SIN) is proposed, which performs at least as well as zero-forcing (ZF) beamforming. All base stations share channel state information, but each user's message is only routed to those that participate in the user's coordination cluster. SIN precoding is particularly useful when clusters of limited sizes overlap in the network, in which case traditional techniques such as dirty paper coding or ZF do not directly apply. The SIN precoder is computed by solving a sequence of convex optimization problems. SIN under partial network coordination can outperform ZF under full network coordination at moderate SNRs. Under overlapping coordination clusters, SIN precoding achieves considerably higher throughput compared to myopic ZF, especially when the clusters are large.