M²-m² Beamforming for Virtual MIMO Broadcasting in Multi-Hop Relay Networks

The emerging demand for multi-hop relay networks requires significant improvement of the end-to-end throughput through the development of a more advanced transmission technology. Research on multiple-input multiple-output (MIMO) has been actively pursued for achieving channel throughput improvements for cellular networks. In a multi-hop ad-hoc network, it is difficult for each sensor node to have multiple transmit antennas, therefore, virtual MIMO has been introduced as an extended version of cellular MIMO. The conventional virtual MIMO scheme requires additional complexity in order to implement the same functionality used for cellular systems. Therefore, we propose a new framework for the broadcast virtual MIMO system (BVMS) by developing an innovative max-min/min-max (M²-m²) beamforming technology optimized for the multi-hop relay network. Compared to the conventional singular value decomposition (SVD)-based or random beamforming technologies, M²-m² beamforming significantly improves the end-to-end channel throughput up to the optimal bound for the BVMS over a multi-hop relay network.