Maximum Eigenmode Relaying with statistical Channel State Information at the Relay

TL;DR

This paper investigates optimal relay precoding strategies to maximize ergodic capacity in multi-antenna relay channels using statistical channel information, introducing the Maximum Eigenmode Relaying method for simplified transmission.

Contribution

It derives the optimal precoding directions based on eigenvectors of the channel covariance and establishes conditions where single eigenvector transmission suffices for capacity maximization.

Findings

Optimal precoding aligns with eigenvectors of channel covariance.

Maximum Eigenmode Relaying (MER) achieves capacity under specific conditions.

Conditions for single eigenvector transmission to be capacity optimal.

Abstract

Optimal precoding in the relay is investigated to maximize ergodic capacity of a multiple antenna relay channel. The source and the relay nodes are equipped with multiple antennas and the destination with a single antenna. It is assumed that the channel covariance matrices of the relay's receive and transmit channels are available to the relay, and optimal precoding at the relay is investigated. It is shown that the optimal transmission from the relay should be conducted in the direction of the eigenvectors of the transmit-channel covariance matrix. Then, we derive the necessary and sufficient conditions under which the relay transmission only from the strongest eigenvector achieves capacity; this method is called Maximum Eigenmode Relaying (MER).