On Gaussian Half-Duplex Relay Networks

TL;DR

This paper analyzes Gaussian half-duplex relay networks, characterizing their capacity and degrees-of-freedom, and introduces schemes that achieve near-capacity performance with different relay switching strategies.

Contribution

It provides the first characterization of generalized Degrees-of-Freedom for half-duplex relay networks and demonstrates capacity approximations within a constant gap for multiple relays.

Findings

Capacity can be achieved within a constant gap regardless of channel parameters.

Random relay switching generally outperforms deterministic switching.

The generalized Degrees-of-Freedom for multiple relays can be computed via linear programming.

Abstract

This paper considers Gaussian relay networks where a source transmits a message to a sink terminal with the help of one or more relay nodes. The relays work in half-duplex mode, in the sense that they can not transmit and receive at the same time. For the case of one relay, the generalized Degrees-of-Freedom is characterized first and then it is shown that capacity can be achieved to within a constant gap regardless of the actual value of the channel parameters. Different achievable schemes are presented with either deterministic or random switch for the relay node. It is shown that random switch in general achieves higher rates than deterministic switch. For the case of K relays, it is shown that the generalized Degrees-of-Freedom can be obtained by solving a linear program and that capacity can be achieved to within a constant gap of K/2log(4K). This gap may be further decreased by considering more structured networks such as, for example, the diamond network.