Experiment on MIMO two-way relaying using transmit beamforming

MIMO 2-way relay network is known as a solution to realize high data rate relay networks. 2-way relaying is possible provided that interference cancellation techniques, e.g. MIMO beamforming or network coding are properly introduced. Many theoretical works on relaying using beamforming exist, but no implementation on real hardware has been reported. These works try to maximize the throughput and the relay node is not allowed to be a data source. Such relaying schemes are not suitable for our targeting networks, e.g. smart utility networks, sensor networks, etc. We implement a simple beamforming scheme that allows the relay node to be a data source. Moreover, most theoretical works assume perfect CSIT without consideration on implementation. We employ RF calibration to obtain CSIT. We evaluate the accuracy of the calibration using the channels measured in real environment, and the result confirms the validity of the method. We also present a demonstration system to show the flexibility of the implemented scheme.