CSIT Sharing over Finite Capacity Backhaul for Spatial Interference Alignment

TL;DR

This paper proposes a quantization scheme for sharing channel state information over limited-capacity backhaul links in TDD cellular systems to enable interference alignment while preserving multiplexing gain.

Contribution

It introduces a novel quantization method that reduces backhaul load and derives the scaling law for bits needed to maintain IA performance.

Findings

Quantization scheme reduces backhaul data exchange

Scaling law for bits preserves multiplexing gain

Enables efficient interference alignment in TDD systems

Abstract

Cellular systems that employ time division duplexing (TDD) transmission are good candidates for implementation of interference alignment (IA) in the downlink since channel reciprocity enables the estimation of the channel state by the base stations (BS) in the uplink phase. However, the interfering BSs need to share their channel estimates via backhaul links of finite capacity. A quantization scheme is proposed which reduces the amount of information exchange (compared to conventional methods) required to achieve IA in a TDD system. The scaling (with the transmit power) of the number of bits to be exchanged between the BSs that is sufficient to preserve the multiplexing gain of IA is derived.