Urban Air Mobility (UAM) is evolving into a cornerstone of modern transportation, promising a future where air taxis and ride-sharing services soar above congested city streets. As we stand on the brink of this aerial revolution, it’s crucial to delve into the communication systems that will underpin its safety and efficiency.
In the initial phase of UAM, expected within the next decade, urban air vehicles will navigate through various airspaces, sharing the skies with conventional and unmanned aircraft. The Federal Aviation Administration (FAA) in the United States envisions operation in urban air corridors under Community-Based Rules, even if operating under Visual Flight Rules (VFR).
Communication in these corridors, however, grapples with constraints such as frequency availability, range, quality of service, and management of these communications.
At around 1,000 feet above ground level, UAM vehicles will encounter unique challenges posed by the urban landscape. High-rise buildings, bridges, and other structures disrupt communication signals intended for airborne vehicles, including Global Navigation Satellite System (GNSS) signals and traditional radar surveillance. Very High Frequency (VHF) voice communications and Automatic Dependent Surveillance-Broadcast (ADS-B) systems are already stretched thin at high-density airports, and the addition of numerous UAM vehicles could overwhelm these systems.
An interesting concept in managing UAM traffic involves designated corridors and linear routes. Linear routes, tested in Google Wing and BNSF Pathfinder UAS flights, follow roads or railroads, simplifying routing and reducing obstacles. Corridors, similar to VFR corridors in Class B airspace, offer strategic separation from conventional traffic, although they currently fall short in accommodating the projected volume of UAM traffic.
Looking towards future communication systems, the development of a robust and efficient system like Drone-to-Drone (D2D) communication is crucial. The proposed DroneCAST system is tailored to urban airspace requirements, focusing on collision avoidance. However, unmanned aircraft currently lack a redundant, higher-level safety net for traffic coordination and monitoring, a staple in civil aviation.
Challenges in urban airspace communication are multifaceted. The high density of drones, rapid changes in topology, and the physical environment of cities create complex signal propagation conditions. Electromagnetic signals in urban settings are reflected, scattered, and diffracted, requiring careful consideration during reception to reconstruct transmitted signals and mitigate interference.
In response to these challenges, a multi-link approach, combining different data link technologies, is being pursued. This approach increases redundancy and system performance. Essential elements include cooperative collision avoidance via ad hoc communication, redundant monitoring and tracking of aircraft, and backup datalinks for critical applications beyond collision avoidance.
Recent advancements in the UAV market have been bolstered by developments in electric batteries and drone technology. Personal Aerial Vehicles (PAVs) are expected to be fully autonomous and coexist with human-driven vehicles, unlike the current integration challenges of autonomous ground vehicles. Japanese company NEC, for instance, anticipates using PAVs for goods delivery by 2023 and passenger transport by 2030. These PAVs will require robust communication with control centers for efficient and safe operation.
The envisaged 6G mobile network is expected to employ Artificial Intelligence (AI) to dynamically manage its resources. AI will be crucial in adapting to rapid changes in channel and environmental conditions, an essential feature for airborne networks serving high-speed ground and aerial vehicles. Future urban AVs, primarily operating in low-altitude airspace, will necessitate innovative radio planning. Traditional radar systems and radio communications are inadequate for tracking and controlling low-flying aircraft in dense urban areas.
NASA, alongside companies like Amazon and Google, is working towards developing a private airspace system for controlling low-altitude airspace. This effort calls for a system that establishes dynamic airway corridors for UAVs and PAVs.
In summary, the journey of UAM from a futuristic vision to a near-term reality hinges on the development and integration of sophisticated communication systems. From overcoming urban landscape challenges to implementing AI in managing airspace, the evolution of communication technologies is as dynamic and multifaceted as the concept of UAM itself. The success of this aerial revolution will not only redefine urban transportation but also mark a significant leap in the application of advanced communication technologies in aviation.