Opportunistic Interference Alignment in MIMO Interference Channels

TL;DR

This paper introduces interference alignment techniques allowing a secondary MIMO link to reuse the same frequency band as a primary link without causing interference, by exploiting unused channel singular modes under power constraints.

Contribution

It proposes a linear pre-coder and power allocation scheme for perfect interference alignment in MIMO channels, enabling secondary links to achieve high data rates without disrupting primary links.

Findings

Significant data rates achieved with few antennas.

Interference alignment effectively nullifies impact on primary link.

Power allocation enhances secondary link performance.

Abstract

We present two interference alignment techniques such that an opportunistic point-to-point multiple input multiple output (MIMO) link can reuse, without generating any additional interference, the same frequency band of a similar pre-existing primary link. In this scenario, we exploit the fact that under power constraints, although each radio maximizes independently its rate by water-filling on their channel transfer matrix singular values, frequently, not all of them are used. Therefore, by aligning the interference of the opportunistic radio it is possible to transmit at a significant rate while insuring zero-interference on the pre-existing link. We propose a linear pre-coder for a perfect interference alignment and a power allocation scheme which maximizes the individual data rate of the secondary link. Our numerical results show that significant data rates are achieved even for a reduced number of antennas.