Analysis over Spectral Efficiency and Power Scaling in Massive MIMO Dual-Hop Systems with Multi-Pair Users

Baofeng JI
Yongming HUANG
Chunguo LI
Ying HU
Yewang QIAN

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E99-A    No.9    pp.1665-1673
Publication Date: 2016/09/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E99.A.1665
Type of Manuscript: PAPER
Category: Information Theory
massive MIMO,  dual-hop,  multi-pair users,  spectral efficiency,  power scaling,  

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This paper considers a massive multiple-input-multiple-output (MIMO) relaying system with multi-pair single-antenna users. The relay node adopts maximum-ratio combining/maximum-ratio transmission (MRC/MRT) stratagem for reception/transmission. We analyze the spectral efficiency (SE) and power scaling laws with respect to the number of relay antennas and other system parameters. First, by using the law of large numbers, we derive the closed-form expression of the SE, based on which, it is shown that the SE per user increases with the number of relay antennas but decreases with the number of user pairs, both logarithmically. It is further discovered that the transmit power at the source users and the relay can be continuously reduced as the number of relay antennas becomes large while the SE can maintains a constant value, which also means that the energy efficiency gain can be obtained simultaneously. Moreover, it is proved that the number of served user pairs can grow proportionally over the number of relay antennas with arbitrary SE requirement and no extra power cost. All the analytical results are verified through the numerical simulations.