Channel Rank Improvement in Urban Drone Corridors Using Passive Intelligent Reflectors

Abstract

Multiple-input multiple-output (MIMO) techniques can help in scaling the achievable air-to-ground (A2G) channel capacity while communicating with drones. However, spatial multiplexing with drones suffers from rank deficient channels due to the unobstructed line-of-sight (LoS), especially in millimeterwave (mmWave) frequencies that use narrow beams. One possible solution is utilizing low-cost and lowcomplexity metamaterial-based intelligent reflecting surfaces (IRS) to enrich the multipath environment, taking into account that the drones are restricted to fly only within well-defined drone corridors. A hurdle with this solution is placing the IRSs optimally. In this study, we propose an approach for IRS placement with a goal to improve the spatial multiplexing gains, and hence to maximize the average channel capacity in a predefined drone corridor. Our results at 6 GHz, 28 GHz and 60 GHz show that the proposed approach increases the average rates for all frequency bands for a given drone corridor, when compared with the environment where there are no IRSs present, and IRS-aided channels perform close to each other at sub-6 and mmWave bands.

Reconfigurable Intelligent Surfaces: Channel Characterization and Modeling

“…To solve the problem of rank deficiency due to the unobstructed LOS in UAV communications, RIS was utilized to enrich the channel in [79]. An RIS placement approach was proposed to improve the spatial multiplexing gains and maximize the average channel capacity in a predefined drone corridor.…”

National Radio Dynamic Zone Concept with Autonomous Aerial and Ground Spectrum Sensors

“…to capture variations due to foliage, new construction, weather effects, among others. At mmWave and THz frequencies, the use of absorbers, passive/active meta-surfaces [20], and metallic reflectors [21] can help contain/steer the signals of interest within the NRDZ environment. In addition, mobile aerial and ground platforms that may carry such reflectors can be used to actively contain the signals inside the NRDZ by a dynamic aerial trajectories.…”