Abstract
The future 5G networks are expected to use millimeter wave (mmWave) frequency bands to take advantage of the large unused spectrum. However, due to the high path loss at mmWave frequencies, coverage of mmWave signals can get severely reduced, especially for non-line-of-sight (NLOS) scenarios as mmWave signals are severely attenuated when going through obstructions. In this work, we study the use of passive metallic reflectors of different shapes/sizes to improve 28 GHz mmWave signal coverage for both indoor and outdoor NLOS scenarios. We quantify the gains that can be achieved in the link quality with metallic reflectors using measurements, analytical expressions, and ray tracing simulations. In particular, we provide an analytical model for the end-to-end received power in an NLOS scenario using reflectors of different shapes and sizes. For a given size of the flat metallic sheet reflector approaching to the size of the incident beam, we show that the reflected received power for the NLOS link is the same as line-of-sight (LOS) free space received power of the same link distance. Extensive results are provided to study the impact of environmental features and reflector characteristics on NLOS link quality.
Highlights
T HE USE of smart communication devices and the higher data rate applications supported by them have seen a surge in the recent decade
A parabolic passive reflector is used for outdoor coverage enhancement at mmWave frequencies in [10], that reflects incoming signal power from the base station to users in the building shadowed zones
The reflected power from a metallic reflector was taken as a secondary source of transmission that can be further extended to other reflectors
Summary
T HE USE of smart communication devices and the higher data rate applications supported by them have seen a surge in the recent decade. A parabolic passive reflector is used for outdoor coverage enhancement at mmWave frequencies in [10], that reflects incoming signal power from the base station to users in the building shadowed zones. If the size of the flat reflector is smaller than the size of the incident beam, interference fringes are expected to occur These interference fringes arising due to wavelets generated by the edges and reflected beam from the center results in overall reduction of the received power. The metallic reflectors (either installed separately or already present metallic structures) can be placed/oriented indoors in the propagation path of routers, access points, or pico base stations, which do not have a direct LOS with the mmWave transmitter This can help in extending the coverage to NLOS areas. For outdoors, signboards and advertisement boards (if properly oriented) can act as reflectors for cellular network’s coverage enhancement
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