Multipair Two-way Half-Duplex Relaying with Massive Arrays and Imperfect CSI

Abstract

We consider a two-way half-duplex relaying system where multiple pairs of single antenna users exchange information assisted by a multi-antenna relay. Taking into account the practical constraint of imperfect channel estimation, we study the achievable sum spectral efficiency of the amplify-and-forward (AF) and decode-and-forward (DF) protocols, assuming that the relay employs simple maximum ratio processing. We derive an exact closed-form expression for the sum spectral efficiency of the AF protocol and a large-scale approximation for the sum spectral efficiency of the DF protocol when the number of relay antennas, $M$, becomes sufficiently large. In addition, we study how the transmit power scales with $M$ to maintain a desired quality-of-service. In particular, our results show that by using a large number of relay antennas, the transmit powers of the user, relay, and pilot symbol can be scaled down proportionally to $1/M^{\alpha }$, $1/M^{\beta }$, and $1/M^{\gamma }$ for certain $\alpha$, $\beta$, and $\gamma$, respectively. This elegant power scaling law reveals a fundamental tradeoff between the transmit powers of the user/relay and pilot symbol. Finally, capitalizing on the new expressions for the sum spectral efficiency, novel power allocation schemes are designed to further improve the sum spectral efficiency.

arXiv comment64 pages, 19 figures, Submitted to IEEE Transactions on Information Theory, July 2016

References in corpus (4)

• Massive MIMO for Next Generation Wireless Systems
• Multi-Pair Amplify-and-Forward Relaying with Very Large Antenna Arrays
• Sum-Rate Maximization with Minimum Power Consumption for MIMO DF Two-Way Relaying: Part II - Network Optimization
• Performance Analysis and Scaling Law of MRC/MRT Relaying with CSI Error in Massive MIMO Systems

Cited by in corpus (1)

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