# Interference Exploitation in Full Duplex Communications: Trading Interference Power for Both Uplink and Downlink Power Savings

## TL;DR

This paper introduces a novel approach for full-duplex wireless systems that exploits interference constructively, enabling significant power savings and improved energy efficiency by balancing uplink and downlink power use.

## Contribution

It proposes a multi-objective optimization framework that leverages data and channel knowledge to exploit interference, unlike traditional suppression methods, and extends to robust designs with imperfect CSI.

## Key findings

- Significant power savings achieved through constructive interference exploitation.
- The MOOP approach enables flexible trade-offs between uplink and downlink power savings.
- Enhanced energy efficiency in full-duplex wireless systems demonstrated through simulations.

## Abstract

This paper considers a multiuser full-duplex (FD) wireless communication system, where a FD radio base station (BS) serves multiple single-antenna half-duplex (HD) uplink and downlink users simultaneously. Unlike conventional interference mitigation approaches, we propose to use the knowledge of the data symbols and the channel state information (CSI) at the FD radio BS to exploit the multi-user interference constructively rather than to suppress it. We propose a multi-objective optimisation problem (MOOP) via the weighted Tchebycheff method to study the trade-off between the two desirable system design objectives namely the total downlink transmit power minimisation and the total uplink transmit power minimisation problems at the same time ensuring the required quality-of-service (QoS) for all users. In the proposed MOOP, we adapt the QoS constraints for the downlink users to accommodate constructive interference (CI) for both generic phase shift keying (PSK) modulated signals as well as for quadrature amplitude modulated (QAM) signals. We also extended our work to a robust design to study the system with imperfect uplink, downlink and self-interference CSI. Simulation results and analysis show that, significant power savings can be obtained. More importantly, however, the MOOP approach here allows for the power saved to be traded off for both uplink and downlink power savings, leading to an overall energy efficiency improvement in the wireless link.