Downlink Interference Alignment

TL;DR

This paper introduces a downlink interference alignment technique that requires only intra-cell feedback, offering substantial throughput gains especially in scenarios with dominant interferers, with minimal implementation effort.

Contribution

The paper presents a novel downlink interference alignment scheme that simplifies implementation by requiring only intra-cell feedback, unlike uplink schemes.

Findings

Four-fold throughput gain in isolated two-cell layout.

Approximately 20% throughput gain in realistic hexagonal layout.

Potential for significant gains in macro-pico cellular networks.

Abstract

We develop an interference alignment (IA) technique for a downlink cellular system. In the uplink, IA schemes need channel-state-information exchange across base-stations of different cells, but our downlink IA technique requires feedback only within a cell. As a result, the proposed scheme can be implemented with a few changes to an existing cellular system where the feedback mechanism (within a cell) is already being considered for supporting multi-user MIMO. Not only is our proposed scheme implementable with little effort, it can in fact provide substantial gain especially when interference from a dominant interferer is significantly stronger than the remaining interference: it is shown that in the two-isolated cell layout, our scheme provides four-fold gain in throughput performance over a standard multi-user MIMO technique. We show through simulations that our technique provides respectable gain under a more realistic scenario: it gives approximately 20% gain for a 19 hexagonal wrap-around-cell layout. Furthermore, we show that our scheme has the potential to provide substantial gain for macro-pico cellular networks where pico-users can be significantly interfered with by the nearby macro-BS.