Estimating reflection and transmission losses for link-obstructing objects at 70 GHz for 5G wireless backhauling

Wireless backhauling at 70 GHz maybe a viable option for 5G small cells densification. Whether indoors or outdoors, the millimeter-wave (mm-wave) backhaul links in an obstructed-line-of-sight (OLOS) or a non-LOS (NLOS) condition require a thorough investigation on reflection and transmission losses caused by various objects in the environment. In this paper, we evaluate the reflection and transmission loss due to link-obstructing objects at 70 GHz frequency band, ranging from human body to various building materials and vegetation. For this purpose, we employed a free-space wideband mm-wave channel sounding setup in the anechoic chamber and outdoors. The results indicate that building materials, human beings and trees cause significant attenuation of the 70 GHz radio signals, which is on average 45 − 50 dB. On the other hand, building materials such as, windows, and laminated or painted plywood, medium-density fiberboard and plasterboard are good reflectors. This extends an opportunity of establishing stable communication links through reflections from the materials in NLOS conditions using beamforming.