Abstract
We consider non-regenerative multi-group multi-way (MGMW) relaying. A half-duplex non-regenerative multi-antenna relay station (RS) assists multiple communication groups. In each group, multiple half-duplex nodes exchange messages. In our proposal, the required number of communication phases is equal to the maximum number of nodes among the groups. In the first phase, all nodes transmit simultaneously to the RS. Assuming perfect channel state information is available at the RS, in the following broadcast (BC) phases the RS applies transceive beamforming to its received signal and transmits simultaneously to all nodes. We propose three BC strategies for the BC phases: unicasting, multicasting and hybrid uni/multicasting. For the multicasting strategy, network coding is applied to maintain the same number of communication phases as for the other strategies. We address transceive beamforming maximising the sum rate of non-regenerative MGMW relaying. Due to the high complexity of finding the optimum transceive beamforming maximising the sum rate, we design generalised low complexity transceive beamforming algorithms for all BC strategies: matched filter, zero forcing, minimisation of mean square error and BC-strategy-aware transceive beamforming. It is shown that the sum rate performance of non-regenerative MGMW relaying depends both on the chosen BC strategies and the applied transceive beamforming at the RS.
Highlights
Two-way relaying is a spectrally efficient protocol to establish bidirectional communication between two halfduplex nodes via a half-duplex relay station (RS) [1,2,3]
A multi-antenna RS assists L communication groups, where Nl nodes in each group communicate to
We address the optimum transceive beamforming maximising the sum rate of non-regenerative multi-group multi-way (MGMW) relaying
Summary
Two-way relaying is a spectrally efficient protocol to establish bidirectional communication between two halfduplex nodes via a half-duplex relay station (RS) [1,2,3]. In [16], block-diagonalisation-singular-valuedecomposition (BD-SVD) transceive beamforming is designed for separating the two-way pairs by extending BD-SVD transmit beamforming proposed in [17] In applications such as video conference and multiplayer gaming, multiple nodes exchange messages. Multi-way relaying protocols for one communication group, where a half-duplex multi-antenna RS assists N half-duplex nodes to exchange messages, is proposed by the authors of this paper in [20] for a non-regenerative RS and in [21] for a regenerative RS. The proposed strategies are designed in such a way that the number of communication phases remains P = maxl Nl. We derive the sum rate expression for non-regenerative MGMW relaying with the proposed BC strategies for asymmetric and symmetric traffic.
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