Spectral Efficiency of the Cellular Two-Way Relaying with Large Antenna Arrays

TL;DR

This paper analyzes the spectral efficiency of multiuser cellular two-way relay networks with large antenna arrays, showing that amplify-and-forward relaying can approach optimal bounds and maintain performance with power scaling.

Contribution

It derives asymptotic spectral efficiency expressions for large antenna arrays and demonstrates the effectiveness of AF relaying with power scaling in cTWRNs.

Findings

AF relaying can approach the cut-set bound under certain conditions.

Noise propagation is significantly suppressed with large antenna arrays.

Power of BS and users can be scaled inversely with relay antennas while maintaining QoS.

Abstract

This paper considers a multiuser cellular two-way relay network (cTWRN) where multiple users exchange information with a base station (BS) via a relay station (RS). Each user is equipped with a single antenna, while both the BS and the RS are equipped with a very large antenna array. We investigate the performance of the cTWRN with amplify-and-forward (AF) based physical-layer network coding, and derive closed-form expression for the asymptotic spectral efficiency when both the number of antennas at the BS and the RS grow large. It is shown that the noise propagation of the non-regenerative relaying protocol can be greatly suppressed, and the AF relaying scheme can approach the cut-set bound under certain conditions. We also investigate the performance of the AF relaying scheme under two power-scaling cases, and show that the transmit power of the BS and each user can be made inversely proportional to the number of relay antennas while maintaining a given quality-of-service. Numerical results are presented to verify the analytical results.