Communication Solutions for Scaling Number of Collaborative Agents in Swarm of Unmanned Aerial Systems Using Frequency Based Hierarchy

Abstract

Swarms of unmanned aerial systems (UASs) usage is becoming more prevalent in the world. Many private companies and government agencies are actively developing analytical and technological solutions for multi-agent cooperative swarm of UASs. However, the majority of existing research focuses on developing guidance, navigation, and control (GNC) algorithms for a swarm of UASs and proof of stability and robustness of those algorithms. In addition to profound challenges in control of a swarm of UASs, a reliable and fast intercommunication between UASs is one of the vital conditions for success of any swarm. Many modern UASs have high inertia and fly at high speeds which means if latency or throughput are too low in swarms, there is a higher risk for catastrophic failure due to inter-collision within the swarm. This work presents solutions for scaling the number of collaborative agents in swarm of UASs using a frequency-based hierarchy. This work identifies shortcomings and discusses traditional swarm communication systems and how they rely on a single frequency that will handle distribution of information to all or some parts of a swarm. These systems typically use an ad-hoc network to transfer data locally, on the single frequency, between agents without the need of existing communication infrastructure. While this does allow agents the flexibility of movement without concern for disconnecting from the network and managing only neighboring communications, it does not necessarily scale to larger swarms. In those large swarms, for example, information from the outer agents will be routed to the inner agents. This will cause inner agents, critical to the stability of a swarm, to spend more time routing information than transmitting their state information. This will lead to instability as the inner agents’ states are not known to the rest of the swarm. Even if an ad-hoc network is not used (e.g. an Everyone-to-Everyone network), the frequency itself has an upper limit to the amount of data that it can send reliably before bandwidth constraints or general interference causes information to arrive too late or not at all.This work proposes that by using two frequencies and creating a hierarchy where each layer is a separate frequency, a large swarm can be grouped into manageable local swarms. The intra-swarm communication (inside the local swarm) will be handled on a separate frequency while the inter-swarm communication will have its own. A normal mesh network was tested in both hardware in the loop (HiTL) scenarios and a collision avoidance flight test scenario. Those results were compared against dual-frequency HiTL simulations. The dual-frequency simulations showed overall improvement in the latency and throughput comparatively to both the simulated and flight-tested mesh network.