Communicating over Filter-and-Forward Relay Networks with Channel Output Feedback

TL;DR

This paper introduces a new lower bound for the capacity of relay channels with feedback, extending it to multi-hop networks with minimal processing, and proposes a coding strategy to improve communication rates in such systems.

Contribution

It presents a novel lower bound for relay channel capacity with feedback, extends it to general relay networks, and develops an optimized coding scheme for practical applications.

Findings

Improved lower bounds on relay channel capacity with feedback.

Enhanced achievable rates in multi-hop relay networks.

Effective coding strategy for noisy feedback in relay channels.

Abstract

Relay networks aid in increasing the rate of communication from source to destination. However, the capacity of even a three-terminal relay channel is an open problem. In this work, we propose a new lower bound for the capacity of the three-terminal relay channel with destination-to-source feedback in the presence of correlated noise. Our lower bound improves on the existing bounds in the literature. We then extend our lower bound to general relay network configurations using an arbitrary number of filter-and-forward relay nodes. Such network configurations are common in many multi-hop communication systems where the intermediate nodes can only perform minimal processing due to limited computational power. Simulation results show that significant improvements in the achievable rate can be obtained through our approach. We next derive a coding strategy (optimized using post processed signal-to-noise ratio as a criterion) for the three-terminal relay channel with noisy channel output feedback for two transmissions. This coding scheme can be used in conjunction with open-loop codes for applications like automatic repeat request (ARQ) or hybrid-ARQ.