Frequency Selectivity of 60-GHz LOS and NLOS Indoor Radio Channels

This paper analyzes the frequency selectivity, which is caused by multipath effects, of indoor line-of-sight (LOS) and non-LOS (NLOS) channels based on channel measurements in the frequency band of 60 GHz. The coherence bandwidth is determined to characterize frequency selectivity figures of the channels employing the combination of omnidirectional, fan-beam and pencil-beam antennas at transmitter (TX) and receiver (RX) sides. The results quantitatively show how far directional configurations are more effective for combating multipath effect than the omnidirectional ones for LOS channels. The frequency selectivity of the fan-beam-to-fan-beam configuration is less sensitive to misaligned TX-RX beams than the fan-beam-to-pencil-beam one. In addition, when omnidirectional antennas are used at both TX and RX side, the frequency selectivity of a NLOS channel is less sensitive to the TX-RX height difference than that of a LOS channel. Moreover, coherence bandwidth is empirically related to root-mean-squared delay spread. Lastly, the results presented in this paper lead to some useful insights into antenna configurations and beamformer designs for a 60 GHz radio system