In this work, we investigate the spectral efficiency (SE) and energy efficiency (EE) for a massive multiple-input multiple-output multi-pair two-way amplify-and-forward relaying system, where multi-pair users exchange information via a relay station equipped with large scale antennas. We assume that imperfect channel state information is available and maximum-ratio combining/maximum-ratio transmission beamforming is adopted at the relay station. Considering constant or scaled transmit power of pilot sequences, we quantify the asymptotic SE and EE under general power scaling schemes, in which the transmit power at each user and relay station can both be scaled down, as the number of relay antennas tends to infinity. In addition, a closed-form expression of the SE has been obtained approximately. Our results show that by using massive relay antennas, the transmit power at each user and the relay station can be scaled down, with a non-vanishing signal to interference and noise ratio (SINR). Finally, simulation results confirm the validity of our analysis.
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