Mind the Gap : UWB Fare Validation Under Apple Nearby Interaction Constraints

Sammanfattning

Hands-free fare validation in public transport promises shorter dwell times, better accessibility,and reduced friction compared with ticketing that requires active passenger interaction. Ultra-Wideband (UWB) ranging has emerged as a promising enabling technology, and prior gate-system work on Android devices has demonstrated centimeter-level accuracy and sub-secondtransactions. On iPhone, however, UWB is accessible only through Apple’s Nearby Interaction(NI) framework, a session-based, vendor-managed abstraction that hides the timing and schedul-ing primitives those Android systems relied on. This thesis evaluates whether UWB-based farevalidation remains technically viable under that constraint. A prototype ranging system was built using Qorvo UWB units as anchors and an iPhone, with anchor firmware implementing a FIFO admission controller designed around a structural incompatibility identified between NI’s pairwise session model and the shared multi-device ranging modes assumed by prior systems. Five experiments characterize ranging accuracy and reliability across distance, device placement, body blocking, multi-device handoff throughput, and dual-anchor configurations. Inside the gate zone the prototype matches the accuracy envelope reported for consumer UWB smartphones in lab conditions, with single-digit centimeter mean absolute error under controlled placement. The binding constraints lie elsewhere: device placement on the body and the geometry of blocking passengers determine usability, and a one-time Bluetooth association costdominates per-passenger cold-start latency. Sequential admission of pre-connected devices delivers handoff throughput well above realistic rush-hour boarding rates. A second anchor improves availability when the primary link degrades but introduces asymmetric per-anchor accuracy losses under shared-channel contention. The NI constraint does not invalidate UWB-basedfare validation on iPhone; it relocates the design problem from the radio layer to application-level admission, Bluetooth coverage of the approach corridor, and physical anchor topology.