Using Meta-surfaces for Eliminating RF Cables in 5G/6G Connected Vehicles

Vehicles are increasingly getting connected with 5<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> Generation (SG) cellular connectivity, and are expected to be connected to 6<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> Generation (6G) in the future. One of the key challenges of enabling cellular connectivity in a vehicle is radio frequency (RF) cabling from the sharkfin antennas on the top of the vehicle to modem placed inside the vehicle. Such placement of antennas is needed to negate the impact of out-to-in (O2I) losses introduced by a car body. Cost of the cabling can particularly be a concern as cellular systems utilize higher bands. In this paper we study using optically transparent and transmissive meta-surface(s) on windows of a vehicle to eliminate/mitigate the O2I loss. This can eliminate need for RF cable. To do so, we determine the 3-dimensional O2I loss of a Volkswagen Atlas sports utility vehicle (SUV) through measurements in an anechoic chamber. Next, based on this measured O2I loss and the proposed theoretical link model for a transmissive meta-surface we perform link-level analysis of the in-car antenna system with meta-surfaces installed on various glass surfaces. We analyze actively controlled and fixed design meta-surfaces. Our results show that actively controlled meta-surfaces (controlled with full channel information) of desired dimension and placed on the driver and passenger side window can recover the O2I losses in almost all cases. We additionally show that an in-vehicle antenna with fixed design meta-surface (i.e., with fixed refraction angle) can negate the O2I loss to be within 3 dB 90% of the time.