Real-time Localization Based on MIMO Backscattering from Retro-Directive Antenna Arrays

Precise localization is essential for enabling advanced applications in dynamic environments, such as autonomous systems and mobile robotics. As automation technologies evolve, the requirements for higher accuracy, reliability, energy efficiency, rapid updates, and minimal latency in position estimation have intensified. In this paper, we propose the exploitation of backscattering from retro-directive antenna arrays (RAAs) to address these imperatives. Two RAA-based architectures are introduced and evaluated for a range of applications, including network localization and navigation. These architectures enable swift and simple angle-of-arrival estimation by using signals backscattered from RAAs. They also leverage multiple antennas to capitalize on multiple-input-multiple-output (MIMO) gains, thereby addressing the challenges posed by the inherent path loss in backscatter communication, particularly at high frequencies. This approach enables angle-based localization with remarkably low latency, making it suitable for vehicular applications. To achieve this, ad-hoc signaling and processing schemes are developed and their performance is analytically assessed. Numerical results highlight the potential of these schemes, delivering precise, ultra-low-latency localization with low-complexity, energy-efficient devices.