A DoF analysis of compress-and-forward in MIMO Gaussian relay channel with correlated noises

This paper studies the effectiveness of compress-and-forward (CF) relaying scheme for a multiple-input multiple-output (MIMO) Gaussian relay channel with an out-of-band finite-capacity relay-to-destination link in which noises at the relay and destination are correlated due to common sources of interference. This scenario is motivated by the possibility of using device-to-device links for inter-cell interference mitigation in cellular networks. We characterize the necessary and sufficient conditions on the number of antennas under which the relay link rate can result in a near one-to-one improvement to the overall throughput in the high signal-to-noise-ratio and interference-to-noise-ratio regime. We show that these conditions coincide with the necessary and sufficient condition under which full cooperation between relay and destination can improve the degrees of freedom of the relay channel. Simultaneous diagonalization by ∗congruence enables this characterization.