2 × 2 MIMO channel characteristics under received power imbalance through indoor propagation measurements

Multiple-Input Multiple-Output (MIMO) wireless systems are one of the most promising technologies for providing large transmission capacity without expanding the frequency band in cellular mobile systems. This paper discusses 2 × 2 MIMO channel characteristics with different antenna spacing for indoor line-of-site (LOS) environments through propagation measurements considering received power imbalance. The measurements were conducted for three different transmitter antenna spacing (one, two, and five wavelengths), which is set above 2.7 meters from the floor to a downward direction in the corridor. In this situation, the received power imbalance is caused by differences in the antenna pattern gain in the direction of a receiver point between two transmitter antennas. The received power imbalance increases as antenna spacing increases. Finally, we verified that channel capacity decreases when antenna spacing increases. Careful attention to the received power imbalance caused by transmitter antennas should be required when providing MIMO technologies in indoor environments using antennas with different positions in the ceiling.