TDMA Slot Allocation for UAV Formations: Minimum Superframe Lengths for Two-Dimensional Equidistant Deployments

Abstract

This paper looks at the case of mitigating col-lisions between Unmanned Aerial Vehicles (UAVs) in a formation through the use of safety beacons to relay information about UAVs that are at risk of collision due to their geographic proximity to one another. The UAVs send these safety beacons using time division multiple access (TDMA). With TDMA, UAVs can achieve collision-free transmission, thereby reducing the uncertainty of the UAVs in the formation receiving the necessary safety information. In this paper, we provide a system model for a specific regular deployment and a spatial reuse scheme for allocating UAVs to a TDMA slot that operates as follows: the regular, two-dimensional UAV deployment is partitioned into a hexagonal tiling, where all UAVs in the same tile are allocated to different TDMA slots and all UAVs in the same position in their respective tiles are allocated to the same TDMA slot. Through spatial reuse of TDMA slots, theoretical results demonstrate that our scheme can support large formations with a bounded transmission period (i.e. a bounded superframe length). We also ascertain a safety margin factor for the transmit power that can be applied to moderate the effects of interference from multiple UAVs transmitting in the same time slot.