Accuracy of Spread Spectrum Techniques for Ultrasonic Indoor Location

Ultrasonic Orientation-Location Algorithm Based on ToA and AoA Measurements

“…From previous studies [9] indoor ultrasonic environments are characterized mainly by a significant multipath interference. Spread Spectrum (SS) modulations are one of the most successful tools to mitigate these problems.…”

“…Use of Spread Spectrum modulation for improving the robustness of ToA based systems was investigated in [9]. It was found that Frequency-Hopped Spread Spectrum (FH-SS) modulation outperforms Direct Sequence Spread Spectrum (DS-SS) in terms of accuracy under conditions of noise and reverberation.…”

“…From a previous study, presented in [9], the performance advantages of FH over DS were shown. It was demonstrated than for smaller bandwidth, FH modulation provides greater mitigation of multipath interference, one of the most important sources of error in indoor environments.…”

High-Accuracy Reference-Free Ultrasonic Location Estimation

“…Both Direct Sequence Spread Spectrum modulation [25], [26], [27] and Frequency Hop Spread Spectrum (FHSS) modulation [24] have been investigated for use in ultrasonic location estimation. In [28], it was shown that FHSS provides better accuracy than both conventional narrowband pulses and DSSS modulation in terms of noise and multi-path interference immunity. The use of an ultrasonic receiver array for determination of AoA was described previously in [29], [24].…”

Robust High-Accuracy Ultrasonic Range Measurement System

“…Narrowband systems are not robust to in-band noise and are highly affected by multi-path caused by reflections from walls and surrounding obstacles [28,29]. Hazas and Ward [29] proposed the use of wideband ultrasonic signalling with Direct Sequence Spread Spectrum (DSSS) modulation to improve performance under conditions of noise and reverberations.…”