On signal strength and multipath richness in multi-input multi-output systems

A common practice when analyzing systems using multiple antennas at both ends is to focus on the multipath properties and normalize the SNR out of the channel matrix. This paper studies the relationship between the signal strength and multipath richness using indoor measurements taken at the Brigham Young University campus. It is found that the SNR and the multipath richness can be strongly correlated. Hence, some caution is needed when normalizing out the SNR in system performance studies. Furthermore, for an unnormalized channel, the channel capacity usually rises when moving from NLOS into LOS since the loss in multipath is more than compensated for by an increase in SNR. A theoretical study also reveals that for moderate sized systems, the required SNR increase for a LOS channel to yield the same channel capacity as a NLOS channel is not very large.