Performance Analysis for Training-Based Multipair Two-Way Full-Duplex Relaying With Massive Antennas

Abstract

Abstract-This paper considers a multi-pair two-way amplifyand-forward relaying system, where multiple pairs of full-duplex users are served via a full-duplex relay with massive antennas, and the relay adopts maximum-ratio combining/maximumratio transmission (MRC/MRT) processing. The orthogonal pilot scheme and the least square method are firstly exploited to estimate the channel state information (CSI). When the number of relay antennas is finite, we derive an approximate sum rate expression which is shown to be a good predictor of the ergodic sum rate, especially in large number of antennas. Then the corresponding achievable rate expression is obtained by adopting another pilot scheme which estimates the composite CSI for each user pair to reduce the pilot overhead of channel estimation. We analyze the achievable rates of the two pilot schemes and then show the relative merits of the two methods. Furthermore, power allocation strategies for users and the relay are proposed based on sum rate maximization and max-min fairness criterion, respectively. Finally, numerical results verify the accuracy of the analytical results and show the performance gains achieved by the proposed power allocation. IndexTerms-Massive multiple-input multiple-output (MIMO), full-duplex, two-way relay, pilot scheme, power control.

Multi-pair two way AF full-duplex massive MIMO relaying with ZFR/ZFT processing

“…We consider zero-forcing reception (ZFR)/zero-forcing transmission (ZFT) processing at the relay and minimum-meansquare-error (MMSE) relay channel estimation. We note that the bound obtained for MRC/MRT processing based on LS channel estimation in [9] cannot be trivially extended to the ZFR/ZFT processing with MMSE channel estimation, considered herein. This closed-form spectral-efficiency lower bound, with arbitrary number of relay antennas, to the best of our knowledge, have not yet been derived in the massive MIMO relaying literature.…”

“…Full-duplex two-way relaying [6], wherein two users exchange two data units in one channel use via a relay, further improves the spectral efficiency. Two-way full-duplex relaying is recently extended to multi-pair two -way full-duplex relaying [7]- [9] wherein multiple user pairs exchange data via a shared relay in a single channel use. A multi-pair two-way full-duplex relay system has following interference sources: i) co-channel (interpair) interference due to multiple users simultaneously accessing the channel; ii) loop interference at the relay and at the users; and iii) inter-user interference caused due to simultaneous transmission and reception by full-duplex nodes.…”

“…Massive multiple-input multiple-output (MIMO) systems have become popular as they cancel co-channel interference by using simple linear transmit processing schemes e.g., zero-forcing transmission (ZFT) and maximal-ratio transmission (MRT) [10], [11], and significantly improve the spectral efficiency. Massive MIMO technology is also being incorporated in multipair full-duplex relays to cancel the loop interference at the relay, and inter-pair co-channel interference [7]- [9], [12], [13]. Reference [7] derived the achievable rate and a power allocation scheme to maximize the ergodic sum-rate for one-way decode and forward full-duplex massive MIMO relaying.…”

“…Zhang et al in [8] proposed four power scaling schemes for two-way fullduplex massive MIMO relaying to improve its spectral and energy efficiency. Reference [9] developed a power allocation scheme to maximize the sum-rate for multi-pair two-way fullduplex massive MIMO amplify-and-forward (AF) relaying by using maximal-ratio combining (MRC)/MRT processing at the relay, and by using least squares (LS) channel estimation. Dai et al in [12] considered a half-duplex multi-pair two-way massive MIMO AF relay and derived closed-form achievable rate expressions and a power allocation scheme to maximize the sumrate with imperfect channel state information (CSI).…”

“…The authors in [9] have derived the spectral-efficiency lower bound for MRC/MRT relay processing with LS channel estimation. We extend the work done in [9], and next list the main contributions of this paper.…”