  The future 5G networks are expected to use millimeter wave (mmWave) frequency
bands, mainly due to the availability of large unused spectrum. However, due to
high path loss at mmWave frequencies, coverage of mmWave signals can get
severely reduced, especially for non-line-of-sight (NLOS) scenarios. In this
work, we study the use of passive metallic reflectors of different shapes/sizes
to improve mmWave signal coverage for indoor NLOS scenarios. Software defined
radio based mmWave transceiver platforms operating at 28 GHz are used for
indoor measurements. Subsequently, ray tracing (RT) simulations are carried out
in a similar environment using Remcom Wireless InSite software. The cumulative
distribution functions of the received signal strength for the RT simulations
in the area of interest are observed to be reasonably close with those obtained
from the measurements. Our measurements and RT simulations both show that there
is significant (on the order of 20 dB) power gain obtained with square metallic
reflectors, when compared to no reflector scenario for an indoor corridor. We
also observe that overall mmWave signal coverage can be improved utilizing
reflectors of different shapes and orientations.
