Single-Antenna AoA Estimation with UWB Radios

Abstract

Ultra-wideband (UWB) is becoming a major localization technology enabler for the indoor environment. Traditional localization systems rely on time-of-arrival (ToA)-based methods such as two-way ranging (TWR) and time difference of arrival (TDoA). Such solutions cannot scale due to interference from multiple devices sharing the same part of the wireless spectrum. One solution is to use concurrent transmissions for a more efficient use of air time. Concurrency-based localization systems that utilize ToA cannot satisfy the accuracy requirements of many applications due to hardware time scheduling limitations. Angle of Arrival (AoA) is a promising solution that can provide scalability and accuracy when used in a concurrent transmission scheme. UWB radio platforms like Decawave DWM1002 with dual-UWB-chip design have made it possible to accurately measure AoA by calculating the phase difference of arrival (PDoA). State-of-the-art AoA estimation has then been extended to build self-localization systems with an unlimited number of tags and to handle multiple sources at the same time. These methods require tags with dual-chip design which adds cost and complexity. In this paper, we investigate the idea of estimating AoA on single-chip (single-antenna) tags receiving concurrent UWB signals from dual-chip anchors (intra-anchor concurrency). We call our system Single-Antenna AoA Estimation (SA-AoA). As opposed to inter-anchor concurrency, intra-anchor concurrency consists of receiving two concurrent packets from two different chips of the same anchor. By estimating AoA on single-chip tags, SA-AoA reduces the design complexity and the cost of tags by at least 50%. Our results suggest that the single-antenna AoA can achieve performance similar to dual-antenna AoA estimation.