Massive MIMO: Multi-way relaying has become one of the most promising technologies for next generation wireless systems (5G+), for its ability to reliably exchange information among many users and to achieve very high sum spectral efficiency. Many users located in separate geographic locations can exchange their data by using one or several sharing relay networks at the same time-frequency resource. The relay nodes are used to reduce the effect of path loss, and hence, many users can communicate with each other in large regions.
The combination between multi-way relay networks and massive MIMO technology, known as multi-way massive MIMO relaying, has attracted a significant amount of research interest very recently, since it offers substantial system performance gains in terms of spectral and energy efficiency, and transmit power reductions.
In this article, the Queen’s University Belfast researchers considered a multi-way relay system with DF relaying protocol. In addition, the relay station was equipped with many antennas. They proposed a novel transmission protocol which leverages the massive MIMO technology together with successive cancellation decoding. As a result, compared to a conventional scheme, their proposed transmission protocol improved significantly the system performance.
They also derived an analytical approximation of the sum spectral efficiency. This approximation is very tight, especially when the number of relay antennas is large. Based on this closed-formed expression, they proposed two power allocation algorithms that choose the transmit power at the users and the relay station, to maximize the sum spectral efficiency and the energy efficiency. With their proposed power allocation schemes, the system performance (in terms of sum spectral efficiency and energy efficiency) can be significantly improved.
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