On the Capacity Regions of Single-Channel and Multi-Channel Full-Duplex Links

TL;DR

This paper characterizes the capacity regions of full-duplex links in single- and multi-channel systems, providing analytical insights, algorithms for boundary rate pairs, and methods to approximate non-convex regions for improved resource allocation.

Contribution

It offers the first analytical characterization of full-duplex capacity regions and introduces algorithms for boundary computation and convexification, aiding in resource optimization.

Findings

Full-duplex links can significantly outperform traditional TDD in capacity.

The capacity region's shape depends on channel and cancellation scenarios.

Algorithms enable efficient resource allocation within the capacity region.

Abstract

We study the achievable capacity regions of full-duplex links in the single- and multi-channel cases (in the latter case, the channels are assumed to be orthogonal -- e.g., OFDM). We present analytical results that characterize the uplink and downlink capacity region and efficient algorithms for computing rate pairs at the region's boundary. We also provide near-optimal and heuristic algorithms that "convexify" the capacity region when it is not convex. The convexified region corresponds to a combination of a few full-duplex rates (i.e., to time sharing between different operation modes). The algorithms can be used for theoretical characterization of the capacity region as well as for resource (time, power, and channel) allocation with the objective of maximizing the sum of the rates when one of them (uplink or downlink) must be guaranteed (e.g., due to QoS considerations). We numerically illustrate the capacity regions and the rate gains (compared to time division duplex) for various channel and cancellation scenarios. The analytical results provide insights into the properties of the full-duplex capacity region and are essential for future development of scheduling, channel allocation, and power control algorithms.