Now showing 1 - 7 of 7
  • Publication
    DOA Estimation for a Multi-Frequency Signal Using widely-spaced Sensors
    The estimation of sub-sample time-delay from the phase of the cross-power spectrum (CPS) of signals received by widely-spaced receivers requires unwrapped phase. Conventional phase unwrapping methods require a continuous CPS that starts at zero frequency or at a frequency with a known unwrapped phase. A novel phase unwrapping method is proposed herein that is capable of carrying out the task without these requirements. The proposed method is applied to direction-of-arrival (DOA) estimation for a bandpass signal—a case that conventional methods are unable to handle. Analytical performance and experimental results confirm the effectiveness of the proposed method.
  • 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
    Phase-Difference Ambiguity Resolution for a Single-Frequency Signal in the Near-Field Using a Receiver Triplet
    The problem of ambiguity in the phase-difference of a signal received by widely-spaced receivers is considered. It is shown that a collinear receiver triplet with a specific configuration combined with a proposed algorithm can be utilized for phase-difference disambiguation. The identifiability condition is that the difference of the two smaller inter-receiver spacings is not greater than a half-wavelength of the impinging signal and is greater than zero. The effect of the emitter location relative to the receiver array and the effect of noise are studied. Analytic formulae for the MSE (mean squared error) under Gaussian white noise are obtained and are used to directly determine performance versus SNR (signal-to-noise ratio) given the emitter location and the receiver configuration. Performance is found to exhibit an SNR threshold effect that depends on the emitter location and the sensor configuration. The analytic performance predictions are found to be close to the performance obtained in simulation.
      329Scopus© Citations 18
  • Publication
    Phase-Difference Ambiguity Resolution for a Single-Frequency Signal
    In this letter, we propose a novel method to disambiguate the phase-difference of a single-frequency signal observed between a pair of spatially separated sensors, with inter-sensor spacing exceeding half the wavelength of the signal, lambda over two. We mathematically prove that, in a noiseless case, the true phase-difference can unambiguously be estimated utilizing a third collinear sensor, provided that the absolute difference between the two smaller inter-sensor spacings does not exceed lambda over two. The performance of the method is characterized by estimating the probability of failure in noisy cases.
      337Scopus© Citations 31
  • 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.
      5346Scopus© Citations 93
  • Publication
    3D Location and Orientation Estimation using Angle of Arrival
    This paper discusses the problem of joint location and orientation estimation of a receiver using only angle of arrival (AOA) information. Conventional formulations of the problem consist of a number of nonlinear equations where the number of unknowns exceeds the number of equations. However, formulations presented in this paper simplifies the problem in a way that leads of efficient solutions. Two solutions are presented and their performance is compared via simulations using an indoor application as an example. Results emphasize the effectiveness of the the proposed methods.
      344Scopus© Citations 5
  • Publication
    GNSS Instantaneous Ambiguity Resolution and Attitude Determination Exploiting the Receiver Antenna Configuration
    A novel instantaneous method for GNSS attitude determination utilising a new phase-difference ambiguity resolution approach is presented. A tripleantenna receiver configuration with baseline constraints is exploited for ambiguity resolution. It is shown that the ambiguity resolution and attitude determination problems can be solved using simple closed and semi-closed form solutions, without using GNSS codes. Simulation results demonstrate high success rates (> 90%) in most cases, even when the number of visible satellite vehicles is small.
      471Scopus© Citations 17