Now showing 1 - 6 of 6
  • Publication
    Design and Implementation of an Indoor Ultrasonic Communication System
    (The Institution of Engineering and Technology, 2011-06-22) ; ;
    In this paper, an indoor communication system using ultrasonic signals is described. The system uses differential binary phase-shift keying (DBPSK) for transmitting binary data as a part of an indoor positioning system. A synchronization and decoding approach is proposed that exploits the correlation properties of the DBPSK waveforms. All of the detection and decoding/demodulation processes are performed digitally - no analogue circuits are involved. Experiments that were carried out using off-the-shelf components confirmed the feasibility of the proposed system.
  • Publication
    High accuracy Location Estimation of a Mobile Tag using One-way UWB Signalling
    This paper presents a novel algorithm for determining the 3D location of a Mobile Tag (MT) using wireless Base Stations (BSs) and Ultra Wide Band (UWB) one-way signaling. The algorithm is designed for low power, rapid deployment applications in which the BSs are independent, wireless UWB transceivers located at known positions and the tags are receiveonly or transmit-only UWB mobile units. The algorithm utilizes multi-BS time synchronization and hybrid Time Difference of Arrival-Time of Flight (TDoA-ToF) localization to achieve high accuracy tag localization. The algorithm consists of two concurrent tasks. In task I, the BSs exploit periodic inter-BS transmissions to obtain high accuracy multi-BS time synchronization. In task II, a hybrid TDOA-TOF algorithm is used to determine the location of the MT. The algorithm is based on timestamping, or control, of packet Time of Emission (ToE) and estimation of the packet Time of Arrival (ToA). As such, the method is appropriate for use with, but not limited to, IEEE 802.15.4a UWB. In simulations assuming a typical 2 cm standard deviation in ToA estimation error the proposed algorithm was found to provide a RMS error of 2.1 ps and 4.8 ∗ 10−6 ppm for time offset and crystal clock offset between BSs respectively; and a RMS error in MT location estimation of 2.2 cm; which is 36% better accuracy than the conventional TDoA method.
      679Scopus© Citations 14
  • Publication
    Robust High Accuracy Ultrasonic Range Measurement System
    This paper presents a novel method for ultrasonic range estimation. The method uses a wideband frequency-hop spread spectrum ultrasonic signal to increase robustness to noise and reverberation. The method applies cross-correlation with earliest peak search and a novel minimum variance search technique to correct the error in the cross-correlation time-of-flight estimate to within one wavelength of the carrier before applying a phase-shift technique for subwavelength range refinement. The method can be implemented digitally in software and only requires low-cost hardware for signal transmission and acquisition. Experimental results show an accuracy of better than 0.5 mm in a typical office environment.
      2153Scopus© Citations 76
  • Publication
    High Accuracy Reference-free Ultrasonic Location Estimation
    This paper presents a novel reference-free ultrasonic indoor location system. Unlike most previous proposals, the mobile device (MD) determines its own position based only on ultrasonic signals received at a compact sensor array and sent by a fixed independent beacon. No radio frequency or wired timing reference signal is used. Furthermore, the system is privacy aware and one way in that the receive-only MD determines its own position based on ultrasonic signals received from fixed transmit-only beacons. The MD uses a novel hybrid angle of arrival (AoA)¿time of flight (ToF) with timing lock algorithm to determine its location relative to the beacons with high accuracy. The algorithm utilizes an AoA-based location method to obtain an initial estimate of its own location. Based on this, it estimates the timing offsets (TOs) between the MD clock and the beacon transmissions. The average TO and the known periodicities of the beacon signals are then used to obtain a second more accurate MD location estimate via a ToF method. The system utilizes wideband spread spectrum ultrasonic signaling in order to achieve a high update rate and robustness to noise and reverberation. A prototype system was constructed, and the algorithm was implemented in software. The experimental results show that the method provides 3-D accuracy better than 9.5 cm in 99% of cases, an 80% accuracy improvement over the conventional AoA-only method.
      5485Scopus© Citations 100
  • Publication
    High Resolution Time Of Arrival Estimation for OFDM-Based Transceivers
    (Institute of Engineering and Technology (IET), 2014-10) ; ; ; ;
    This letter presents a novel algorithm for Time Of Arrival (TOA) estimation for Orthogonal Frequency Division Multiplexing (OFDM) based transceivers. The algorithm processes the sampled baseband signal to obtain a high resolution estimate of the TOA of the OFDM symbol. In the first step, the algorithm obtains a sample resolution estimate of the TOA by finding the peak of the absolute value of the cross-correlation of the in-phase and quadrature received signals with the known transmitted symbol. In the second step, the algorithm refines this estimate to sub-sample resolution by estimating the phase delay of the received signal based on the gradient of a linear fit to the phase difference between the transmitted and received sub-carriers (in the frequency domain). The algorithm was applied to the Long Training Sequence (LTS) symbol of the IEEE Wireless Local Area Network (WLAN) 802.11g preamble. In real-world experiments, the algorithm was found to achieve a mean TOA estimation error of 49 cm in a low multi-path Line Of Sight (LOS) environment for ranges of 1-7 m.
      1009Scopus© Citations 27
  • Publication
    Survey of WiFi Positioning using Time-Based Techniques
    Estimating the position of mobile devices with high accuracy in indoor environments is of interest across a wide range of applications. Many methods and technologies have been proposed to solve the problem but, to date, there is no 'silver bullet'. This paper surveys research conducted on indoor positioning using time-based approaches in conjunction with the IEEE 802.11 wireless local area network standard (WiFi). Location solutions using this approach are particularly attractive due to the wide deployment of WiFi and because prior mapping is not needed. This paper provides an overview of the IEEE 802.11 standards and summarizes the key research challenges in 802.11 time-based positioning. The paper categorizes and describes the many proposals published to date, evaluating their implementation complexity and positioning accuracy. Finally, the paper summarizes the state-of-the-art and makes suggestions for future research directions.
      1577Scopus© Citations 64