# X-duplex Relaying: Adaptive Antenna Configuration

## TL;DR

This paper introduces X-duplex, an adaptive relay scheme that dynamically switches antenna configurations and transmission modes to enhance diversity, reduce error rates, and improve overall relay system performance.

## Contribution

It proposes a novel adaptive antenna and mode selection scheme for relay networks, combining full-duplex and half-duplex modes based on SER minimization.

## Key findings

- Achieves additional spatial diversity.
- Reduces high-SNR performance floor.
- Improves relay system performance.

## Abstract

In this letter, we propose a joint transmission mode and transmit/receive (Tx/Rx) antenna configuration scheme referred to as X-duplex in the relay network with one source, one amplify-and-forward (AF) relay and one destination. The relay is equipped with two antennas, each of which is capable of reception and transmission. In the proposed scheme, the relay adaptively selects its Tx and Rx antenna, operating in either full-duplex (FD) or half-duplex (HD) mode. The proposed scheme is based on minimizing the symbol error rate (SER) of the relay system. The asymptotic expressions of the cumulative distribution function (CDF) for the end-to-end signal to interference plus noise ratio (SINR), average SER and diversity order are derived and validated by simulations. Results show that the X-duplex scheme achieves additional spatial diversity, significantly reduces the performance floor at high SNR and improves the system performance.