Fundamental Limits of Integrated Localization and Sensing in the Near Field Using UWB Signals

Locating active user equipments (UEs) and sensing passive targets (TARs) can be integrated with the deployment of antenna arrays and high-bandwidth signals. Impulse radio ultra-wideband (IR-UWB) signals have become attractive in the integrated localization and sensing (ILAS) system due to their high time resolution and large bandwidth. In this paper, we design a single station ILAS system based on IR-UWB signals with UE and multi-targets. We derive the performance lower bound for the ILAS system under the near-field (NF) assumption using the spherical wavefront model. Furthermore, coming up with the complexity of parameter estimation caused by the coupling between UE and TARs, we propose a low-complexity ILAS solution based on time difference of arrival (TDOA) measurements, at the cost of sacrificing target position estimation performance. Finally, using the Cramer-Rao lower bound (CRLB) as a performance metric, numerical results are given to show that electromagnetic (EM) wave model mismatch under NF conditions leads to a degradation in localization, ranging, and bearing estimation performance. Additionally, the effectiveness of the proposed low-complexity ILAS solution strategy is validated.