Full-Duplex Radio for Uplink/Downlink Wireless Access with Spatially Random Nodes

TL;DR

This paper investigates full-duplex multi-antenna access points supporting simultaneous uplink and downlink transmissions with spatially random users, demonstrating significant sum rate improvements over half-duplex systems even with imperfect interference cancellation.

Contribution

It introduces precoding schemes for FD APs based on stochastic geometry, providing analytical insights and showing potential for doubling system performance compared to HD modes.

Findings

FD precoding improves UL/DL sum rate.

Performance gains persist with imperfect LI cancellation.

Increasing receive antennas enhances sum rate more than increasing transmit antennas.

Abstract

A full-duplex (FD) multiple antenna access point (AP) communicating with single antenna half-duplex (HD) spatially random users to support simultaneous uplink (UL)/downlink (DL) transmissions is investigated. Since FD nodes are inherently constrained by the loopback interference (LI), we study precoding schemes for the AP based on maximum ratio combining (MRC)/maximal ratio transmission (MRT), zero-forcing and the optimal scheme for UL and DL sum rate maximization using tools from stochastic geometry. In order to shed insights into the system's performance, simple expressions for single antenna/perfect LI cancellation/negligible internode interference cases are also presented. We show that FD precoding at AP improves the UL/DL sum rate and hence a doubling of the performance of the HD mode is achievable. In particular, our results show that these impressive performance gains remain substantially intact even if the LI cancellation is imperfect. Furthermore, relative performance gap between FD and HD modes increases as the number of transmit/receive antennas becomes large, while with the MRC/MRT scheme, increasing the receive antenna number at FD AP, is more beneficial in terms of sum rate than increasing the transmit antenna number.