On the transmit strategy for the interference MIMO relay channel in the low power regime

TL;DR

This paper investigates optimal transmit strategies for a MIMO relay-assisted interference channel in low power conditions, proposing a scheme that achieves linear sum rate growth with power and simplifies at high relay power.

Contribution

It introduces a novel transmission scheme combining block Markov encoding, beamforming, and backward decoding for low power regimes in MIMO relay channels.

Findings

Sum rate is linear in power at low transmit powers.

Power allocation scheme achieves the rate region.

Simplified strategy at high relay power.

Abstract

This paper studies the interference channel with two transmitters and two receivers in the presence of a MIMO relay in the low transmit power regime. A communication scheme combining block Markov encoding, beamforming, and Willems' backward decoding is used. With this scheme, we get an interference channel with channel gains dependent on the signal power. A power allocation for this scheme is proposed, and the achievable rate region with this power allocation is given. We show that, at low transmit powers, with equal power constraints at the relay and the transmitters, the interference channel with a MIMO relay achieves a sum rate that is linear in the power. This sum rate is determined by the channel setup. We also show that in the presence of abundant power at the relay, the transmit strategy is significantly simplified, and the MAC from the transmitters to the relay forms the bottle neck of the system from the sum rate point of view.