Rate Bounds for MIMO Relay Channels Using Message Splitting

This paper considers the multi-input multi-output (MIMO) relay channel where multiple antennas are employed by each terminal. Compared to single-input singleoutput (SISO) relay channels, MIMO relay channels introduce additional degrees of freedom that allow for partial cooperation between the transmitter and the relay. A partial cooperation strategy that combines transmit-side message splitting and block-Markov encoding is presented. New lower capacity bounds that improve on a previously proposed non-cooperative lower bound are derived for both discrete memoryless relay channels and Gaussian relay channels.