Joint Transmit Precoding for the Relay Interference Broadcast Channel

TL;DR

This paper introduces a novel algorithm for joint transmit precoding in relay interference broadcast channels, optimizing end-to-end sum-rates in relay-based cellular systems with interference coupling.

Contribution

It proposes a distributed precoding design method that maximizes end-to-end sum-rates by iteratively optimizing second-hop and first-hop transmissions, addressing rate mismatch issues.

Findings

Outperforms separate single-hop interference management strategies.

Provides a fast-converging, distributed implementation.

Enhances end-to-end sum-rate performance in relay interference channels.

Abstract

Relays in cellular systems are interference limited. The highest end-to-end sum rates are achieved when the relays are jointly optimized with the transmit strategy. Unfortunately, interference couples the links together making joint optimization challenging. Further, the end-to-end multi-hop performance is sensitive to rate mismatch, when some links have a dominant first link while others have a dominant second link. This paper proposes an algorithm for designing the linear transmit precoders at the transmitters and relays of the relay interference broadcast channel, a generic model for relay-based cellular systems, to maximize the end-to-end sum-rates. First, the relays are designed to maximize the second-hop sum-rates. Next, approximate end-to-end rates that depend on the time-sharing fraction and the second-hop rates are used to formulate a sum-utility maximization problem for designing the transmitters. This problem is solved by iteratively minimizing the weighted sum of mean square errors. Finally, the norms of the transmit precoders at the transmitters are adjusted to eliminate rate mismatch. The proposed algorithm allows for distributed implementation and has fast convergence. Numerical results show that the proposed algorithm outperforms a reasonable application of single-hop interference management strategies separately on two hops.