Experimental Performance of Null-Space Expanded MIMO Reception Technique

This research focuses on multiple-input multiple-output signal separation in environments with changing channels, such as mobile communications. When separating linear signals by fixing combining weights to packets, the orthogonality between interfering signals and combining weights is broken due to the movement of the receiver, resulting in interference leakage. To suppress such degradation, we use the null-space expansion technique in the frequency-domain, assuming that there are extra antennas at the receiver side. This technique improves channel time-varying immunity by using extra receiving antennas to form a null space that suppresses interference between streams. Experiments evaluated the performance of the fluctuation tolerance when combining weights were applied to the entire packet.