Relationship Between Capacity and Pathloss for Indoor MIMO Channels

MIMO transmission systems exploit scattering in the radio channel to achieve high capacity for a given SNR. A high pathloss is generally expected for channels with rich scattering, suggesting that a high SNR and rich multipath are competing goals. The current work investigates this issue based on measurements obtained with a 16 times 32 MIMO channel sounder for the 5.8 GHz band. The measurements were carried out in various indoor scenarios where different sizes of both the transmitter and receiver antenna arrays are investigated, 1 times 1 up to 16 times 32. A moderate correlation between pathloss and median capacity was found. However, the higher richness can not compensate for the decrease in capacity due to increased pathloss. Assuming a fixed Tx power, the median capacity was found to depend approximately linearly on the pathloss. The slope of the linear relation depends on the effective rank of the channel, which in turn was found to be approximately linearly dependent on the number of antennas, assuming a symmetric MIMO channel