ULTRASONIC BEACON-BASED LOCAL POSITION SYSTEM USING BROADBAND PN (PSEUDO NOISE) - CHIRP CODES

摘要

This work presents the development of a Local Positioning System (LPS), based on the transmission of ultrasonic sig-nals, which have been previously encoded by PN (Pseudo Noise) - chirp codes. The LPS consists of several ultra-sonic emitters located at known positions in the deploy-ment environment, and of a portable receiver that com-putes 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 scal-ing 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.