Error Bounds for Terahertz MIMO Positioning of Swarm UAVs for Distributed Sensing

Distributed sensing, where multiple observations from spatially separated antennas are combined, offers many advantages over conventional sensing techniques. The recent advances in the field of unmanned aerial vehicles give rise to an entirely new field of application of distributed sensing. We consider a swarm of unmanned aerial vehicles, where each node of the swarm is equipped with one or multiple antennas, and the swarm senses a target signal collaboratively. With such a swarm, the most compelling feature is that the virtual aperture formed by all the nodes of the swarm is mobile and can be reconfigured. It is well known from the field of distributed sensing that the position of every antenna of the virtual aperture needs to be known precisely to coherently combine the sensed signal. Hence the position of every unmanned aerial vehicle must be determined up to fractions of the sensing wavelength. In order to achieve such a high position accuracy, we consider multiple input multiple output links between nodes, which use orthogonal frequency division multiplexing signals in the terahertz band. We analyze the position and orientation estimation capabilities of such links with respect to the bandwidth, array size, and transmitter-receiver separation. We provide numerical results which reveal the conditions required for millimeter- level positioning accuracy.