Implementation of adaptive channel inversion in a real-time MIMO system

The implementation of adaptive channel inversion into a real-time single carrier MIMO test-bed is reported for the first time. Since no joint detection is possible at the distributed users, all signal preprocessing is performed at the transmitter which adapts the transmission links to all the mobile terminals depending on the actual channel situation. This means that the number of reliably supportable users is controlled as well as the modulation, ensuring BER targets for all users. The implemented algorithms are described and measurement results have shown the stable sum rate throughput of several 10 Mbit/s for a MIMO base station with 4 transmit antennas which supports up to 4 mobile terminals simultaneously. Since the transmission is based on optimum feedback of the channel knowledge to the transmitter, the results given here can be understood as a kind of an upper practical performance bound for the application of linear channel pre-distortion.