# On the Performance of X-Duplex Relaying

## TL;DR

This paper analyzes an X-duplex relay system that adaptively switches between half-duplex and full-duplex modes using shared antennas and RF chains, improving communication performance by reducing interference effects.

## Contribution

It introduces an adaptive X-duplex relay model with shared antennas and RF chains, providing analytical expressions for performance metrics and demonstrating performance gains over traditional schemes.

## Key findings

- X-duplex relay outperforms pure FD and HD schemes in SER, outage probability, and sum rate.
- Flexible RF configurations eliminate performance floors caused by residual self-interference.
- Analytical bounds for outage probability are derived and validated.

## Abstract

In this paper, we study a X-duplex relay system with one source, one amplify-and-forward (AF) relay and one destination, where the relay is equipped with a shared antenna and two radio frequency (RF) chains used for transmission or reception. X-duplex relay can adaptively configure the connection between its RF chains and antenna to operate in either HD or FD mode, according to the instantaneous channel conditions. We first derive the distribution of the signal to interference plus noise ratio (SINR), based on which we then analyze the outage probability, average symbol error rate (SER), and average sum rate. We also investigate the X-duplex relay with power allocation and derive the lower bound and upper bound of the corresponding outage probability. Both analytical and simulated results show that the X-duplex relay achieves a better performance over pure FD and HD schemes in terms of SER, outage probability and average sum rate, and the performance floor caused by the residual self interference can be eliminated using flexible RF chain configurations.