The Approximate Capacity of the MIMO Relay Channel

TL;DR

This paper analyzes the capacity bounds of the MIMO relay channel, demonstrating that partial decode-forward and compress-forward schemes can approximate the capacity within a small, quantifiable gap.

Contribution

It provides new bounds showing that practical coding schemes can achieve near-optimal capacity in MIMO relay channels.

Findings

Partial decode-forward achieves within min(t1,r2) bits of the cutset bound.

Compress-forward achieves within min(t1 + t2, r3) + r2 bits of the cutset bound.

Both schemes provide good approximations of the channel capacity.

Abstract

Capacity bounds are studied for the multiple-antenna complex Gaussian relay channel with t1 transmitting antennas at the sender, r2 receiving and t2 transmitting antennas at the relay, and r3 receiving antennas at the receiver. It is shown that the partial decode-forward coding scheme achieves within min(t1,r2) bits from the cutset bound and at least one half of the cutset bound, establishing a good approximate expression of the capacity. A similar additive gap of min(t1 + t2, r3) + r2 bits is shown to be achieved by the compress-forward coding scheme.