Experimental evaluation in short range MIMO communication with simple transmission scheme

In short range MIMO transmission, the distance between two array antennas that face each other is comparable to the size of the array antenna aperture. The channel capacity with the optimal antenna spacing exceeds the Ergodic capacity of the i.i.d. channel since the short range MIMO scheme is very similar to parallel data transmission. The paper focuses on an actual transmission method that is suitable for short range MIMO communications, because a complex transmission scheme such as Eigenmode beamforming (EM-BF) or Maximum Likelihood Detection (MLD) is actually required to obtain the ideal channel capacity. When the optimal element spacing is obtained, it clarifies that the channel capacity obtained through Zero Forcing (ZF) at the receiver without beamforming at the transmitter is almost same as that using the EM-BF. The effectiveness of short range MIMO transmission is also clarified using a 4x4 MIMO testbed with actual signals based on the IEEE802.11n standard. The paper shows that the optimal element spacing is a key parameter in short range MIMO communications based on simulation and measurements.