Bistatic delay improves 3D location of moving targets with fewer Wi-Fi receivers
Bistatic Delay-Doppler Sensing for 3D Target Localization in Distributed Wi-Fi Systems
Information Theory
Summary
Tracking moving objects in 3D using Wi-Fi signals usually needs many receivers to get accurate locations. This paper shows that adding a type of timing information called bistatic delay reduces the number of receivers required. The authors compare two approaches—using just the speed of the signal’s Doppler shift versus using both speed and timing information—and find that combining delay and Doppler lets you locate targets with fewer receivers. They back this up with math and computer simulations that mimic Wi-Fi systems.
What this means in practice
- •For wireless system designers: Design distributed Wi-Fi sensing setups that accurately track moving targets using fewer receivers by exploiting bistatic delay information.
- •For indoor navigation developers: Improve 3D localization systems for moving objects indoors by combining delay and Doppler data from Wi-Fi signals, reducing hardware needs.
Authors
Kyungmin Hong, Moein Ahmadi, Thomas Stifter, Mounim A. El Yacoubi, Bhavani Shankar Mysore R
Abstract
This paper investigates how bistatic delay information improves the observability and localization performance of 3D moving targets in distributed Wi-Fi sensing. Motivated by emerging IEEE 802.11bf WLAN sensing, we consider one transmitter, multiple distributed receivers, and a single target with unknown position and velocity. We compare Doppler-only sensing with delay-Doppler sensing, in which delay-capable receivers provide additional bistatic path-length information for target localization. We derive the Fisher information matrix (FIM) and the position equivalent FIM (EFIM) for both sensing formulations. The resulting observability analysis shows that Doppler-only localization generically requires six receivers, whereas delay-Doppler localization can become locally identifiable with three receivers under non-degenerate geometry. We further study mixed receiver architectures in which only a subset of receivers provides delay estimates. Simulations with Wi-Fi-like bandwidths confirm the transition and quantify the roles of bandwidth, Doppler noise, receiver geometry, and delay-capable receiver availability.