Wall-E: dual-band metasurfaces for satellite networking

Realizing cost-effective network densification remains another major challenge, especially in remote and rural areas where deploying fixed infrastructures is not economically viable. Recently, there has been much interest in complementing existing cellular networks with Low Earth Orbit (LEO) satellite networks for coverage extension. LEO networks, however, introduce new challenges: the process of aligning the wireless beam directions between user and satellite is very complex as both the satellite and user moves. Additionally, the constellation of LEO satellites collectively moves over the earth, necessitating a handoff from one satellite to another to serve each user. Such hard handovers result in increased RTT and a significant drop in throughput.

Wall-E is an electronically tunable surface mounted on a window/skylight, either refracting the satellite link into the home directly or reflecting signals to support outdoor users. Owing to angular reciprocity, Wall-E can simultaneously steer the downlink and uplink beams at the same angle, speeding up the beam alignment process for the uplink via downlink, and vice-versa. Additionally, Wall-E supports soft handovers by allowing two (or multiple) satellites impinge on the surface at the same time, thus reducing network jitter during handovers. A key obstacle in designing the surface is the frequency duplex division (FDD) in LEO networks, which complicates operation due to the use of different frequency sub-bands in the uplink (upper Ku band) and downlink (lower Ku band) directions. Wall-E is the first of its kind to target dual channels in the Ku radio frequency band.