RIS-aided Trajectory Optimization in Layered Urban Air Mobility

TL;DR

This work tackles the challenge of safe aviation and reliable air-ground communication in layered Urban Air Mobility by introducing a RIS-aided trajectory optimization framework. It combines a dual-plane RIS communication scheme with a dual-time-scale horizontal trajectory optimization and a layer-switching inter-layer strategy, underpinned by a composite potential field for safety. The key contributions include a low-latency dual-plane RIS protocol that yields the smallest delay upper bound and highest resilience to traffic loads, a large-time-scale PSO-based positioning for maximizing communication rate, and a small-time-scale CPF-based safety control with a back-off-inspired layer-switching method, resulting in substantial improvements such as a 40% increase in communication load handling and a 66% reduction in safe-separation restoration time. This work demonstrates the practical viability of 6G RIS-enabled trajectory optimization in structured layered airspace, and points to future extensions to more complex 3D airspace layouts.

Abstract

Urban Air Mobility (UAM) relies on developing aerospace industries, where safe aviation and efficient communication are critical features of aircraft. However, it is challenging for aircraft to sustain efficient air-ground communication in urban circumstances. Without continuous air-ground communication, aircraft may experience course deviation and safety accidents. To address these problems, a reconfigurable intelligent surface(RIS)-aided trajectory optimization scheme is proposed enabling efficient air-ground communication and safe aviation in UAM with a layered airspace structure. This paper first devises a dual-plane RIS communication scheme for layered airspace. It fully engages the omnidirectional and directional signal attributes to reduce the transmission delay of the air-ground communication. Based on the dual-plane RIS configuration, we jointly develop the intra- and inter-layer trajectory scheme to optimize communication and safe aviation. In the intra-layer trajectory optimization, we propose a dual-time-scale flight scheme to improve communication capacity and horizontal flight safety. Meanwhile, we propose a safe layer-switching method to ensure collision avoidance during vertical flight in the inter-layer trajectory optimization. The communication load of the proposed scheme can be improved 40% and the time of safe separation restoration can be lessened 66% compared with the benchmarks in the layered airspace.

Figures (13)

• Figure 1: Demonstration of the layered UAM.
• Figure 2: Framework of RIS-aided trajectory and communication optimization.
• Figure 3: Dual-plane RIS communication.
• Figure 4: Sequence diagram of the Dual-plane RIS communication.
• Figure 5: Two-dimensional safety separations in layered UAM.