# A Performance-Based Airspace Model for Unmanned Aircraft Systems Traffic Management
###### Abstract
The progression of the project is characterized by increasing scenario complexity and required specific autonomous capabilities [6; 11]. Each new TCL extends the capabilities of the previous TCL, with each sequential phase supporting a larger range of UAS from remotely piloted vehicles to fully autonomous UAS. Each capability is targeted to specific types of applications, geographical areas, and use cases that represent certain risk levels. TCL4 is characterized by complex operations in densely populated urban areas and Urban Air Mobility (UAM). The benefits of UAS and manned/unmanned operations within these dense built-up areas are being captured by the NASA Advanced Air Mobility (AAM) working groups, which have already identified numerous public and commercial use-cases [12]. However, several challenges must be addressed to fully realise these benefits. These include Beyond Line-Of-Sight (BLOS) operations, large-scale contingency management, in-flight deconfliction and trajectory conformance monitoring. These new challenges and the safety-critical nature of urban operations will necessarily impose stringent requirements on the infrastructure supporting UTM operations. Some of the open gaps include airspace design, navigation/surveillance infrastructure, communication networks and traffic control/management [13]. In particular, the co-design of coherent airspace structures and efficient sectorisation strategies remains an open research question, with no standardized criteria forming the basis for partitioning the future urban/suburban airspace into functioning operational structures. Airspace sectorisation is a key factor in managing air traffic complexity, human operator workload, and demand-capacity balance [14]. In terms of capacity modelling, demand prediction and demand-capacity balance, a large body of research is available pertaining manned aircraft and conventional Air Traffic Management (ATM) [14; 15; 16; 17; 18; 19]. Recent developments include the dynamic morphing of airspace sectors to mitigate the disruptions associated with capacity saturation [20]. However, owing to the difference in operational complexity, traffic volumes, fleet mixes, and supporting infrastructure, it is readily apparent that airspace design and sectorisation strategies for conventional air traffic are inapplicable in their current form to the UAS/UAM traffic management problem. While various sectorisation concepts and models have been proposed in the literature, as of today, none has been standardized or even agreed upon to cover the whole spectrum of UTM operations. The doctrine applied in this paper is that the required separation of UTM traffic and subsequently, the airspace management strategy should be a direct consequence of the infrastructure supporting the operation, as originally argued in [14]. These include the hardware and software systems operating in the air (avionics systems) and on the ground (traffic management systems) as well as the personnel exercising oversight and control over the operations. This leverages the opportunity to adopt some of the existing frameworks that have been applied or recommended for conventional air traffic In particular, the concept of Performance-Based Operations (PBO), and more specifically Performance Based Navigation (PBN), proves suitable in safely accommodating the highly dynamic nature of operations as envisaged under the UTM framework. The key contribution of this paper is a novel UTM airspace model for urban areas designed to enhance the safety and efficiency of traffic spacing and to maximise exploitation of the airspace resources (capacity). The urban airspace model proposed here is specifically conceived to accommodate a high diversity in performance and operational characteristics of different UAM/UAS platforms. The airspace design and sectorization strategies are centred on the discretization of the airspace into elementary three-dimensional (3D) cells. The dimension of each cell is a function of the performance of the infrastructure supporting a given airspace region.