Ultrasonic Beacon-based Local Position System using Broadband PN (Pseudo Noise) - Chirp Codes

Y. Lu and A. Finger (Germany)


Ultrasonic LPS, PN-chirp codes, Polled-Privacy-Orientedsystem, flexibility, high accuracy, low power.


This work presents the development of a Local Positioning System (LPS), based on the transmission of ultrasonic signals, which have been previously encoded by PN (Pseudo Noise) - chirp codes. The LPS consists of several ultrasonic emitters located at known positions in the deployment environment, and of a portable receiver that computes its position by measuring the Time-of-Flight (TOF) or the Time Difference-of-Arrival (TDOA) between each reference emitter and receiver depending on applications. In this paper the Gold-chirp codes and LS (Loosely Syn chronous) -chirp codes as examples will be presented. This exhibits flexible system accuracy and update rate by scaling the chirp duration. Furthermore, the channel model be tween emitters and receivers is very different in terms of different indoor environments. The problems, which are caused by Inter-Symbol-Interference (ISI) and Multiple Access-Interference (MAI), can also be improved by using PN-chirp codes with scalable sequence length. Finally the system with PN-chirp codes could be working with lower power in comparison with the system by only using PN codes with rectangular pulses for the same coverage.

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