A novel low complexity beamforming scheme for special case of non-regenerative multi-group multi-way relaying

In this paper, we consider a special case of non-regenerative multi-group multi-way relaying channel where the number of half-duplex antennas at relay is less than the total number of nodes. The number of communication phase to complete the full data exchange equals to the maximum number of nodes among all groups. The first phase is multiple-access and the other phases are broadcast. In each broadcast phase, the relay station does not decode streaming data from all nodes and apply beamforming scheme to its received data before sending to all nodes. Because the degree-of-freedom condition is not satisfied, the popular beamforming schemes like Zero Forcing and Minimization of Mean Square Error are not applicable. We propose a new low complexity beamforming scheme for this scenario. The average sum rate and symbol error rate simulation results are provided to compare the performance of our scheme and Coherent Combining scheme.