Signal-Aligned Network Coding in K-User MIMO Interference Channels with Limited Receiver Cooperation

TL;DR

This paper introduces a signal-aligned network coding scheme for K-user MIMO interference channels with limited receiver cooperation, achieving full degrees of freedom and outperforming existing methods in finite SNR scenarios.

Contribution

It proposes a novel SNC scheme that aligns signals and decodes network-coded messages, enabling efficient message recovery at the central processor.

Findings

Achieves full degrees of freedom using signal alignment and network coding.

Outperforms compute-and-forward scheme in finite SNR regimes.

Utilizes signal subspaces effectively for conveying independent message equations.

Abstract

In this paper, we propose a signal-aligned network coding (SNC) scheme for K-user time-varying multiple-input multiple-output (MIMO) interference channels with limited receiver cooperation. We assume that the receivers are connected to a central processor via wired cooperation links with individual limited capacities. Our SNC scheme determines the precoding matrices of the transmitters so that the transmitted signals are aligned at each receiver. The aligned signals are then decoded into noiseless integer combinations of messages, also known as network-coded messages, by physical-layer network coding. The key idea of our scheme is to ensure that independent integer combinations of messages can be decoded at the receivers. Hence the central processor can recover the original messages of the transmitters by solving the linearly independent equations. We prove that our SNC scheme achieves full degrees of freedom (DoF) by utilizing signal alignment and physical-layer network coding. Simulation results show that our SNC scheme outperforms the compute-and-forward scheme in the finite SNR regime of the two-user and the three-user cases. The performance improvement of our SNC scheme mainly comes from efficient utilization of the signal subspaces for conveying independent linear equations of messages to the central processor.