A New Method for Single-Epoch Ambiguity Resolution with Indoor Pseudolite Positioning

Featured Application: This work is potentially applied to indoor high-precision engineering/ industrial measurement, such as parts installation, tunnel engineering, dynamic rail inspection, path planning, etc. Especially in case of pseudolite faulty, the reliability and availability of positioning can be guaranteed. Abstract:The integrity monitoring algorithm based on pseudorange observations has been widely used outdoors and plays an important role in ensuring the reliability of positioning. However, pseudorange observations are greatly affected by the error sources such as multipath, clock drift, and noise in indoor pseudolite system, thus the pseudorange observations cannot be applied to high-precision indoor positioning. In general, double differenced (DD) carrier phase observations are used to obtain a high-precision indoor positioning result. What's more, the carrier phase-based integrity monitoring (CRAIM) algorithm is applied to identify and exclude potential faults of the pseudolites. In this article, a holistic method is proposed to ensure the accuracy and reliability of positioning results. Firstly, if the reference pseudolite operates normally, extended Kalman filter is used for parameter estimation on the premise that the number of common pseudolites meets positioning requirements. Secondly, the innovation sequence in the Kalman filter is applied to construct test statistics and the corresponding threshold is determined from the Chi distribution with a given probability of false alert. The pseudolitehorizontal protection level (HPL) is calculated by the threshold and a prior probability of missed detection. Finally, compared the test statistics with the threshold to exclude the faultypseudolite for the reliability of positioning. The experiment results show that the proposed method improves the accuracy and stability of the results through faults detection and exclusion. This method ensures accuracies at the centimeter level for dynamic experiments and millimeter levels for static ones.

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“…where P represents covariance matrix in expression (4). According to (16) and (17), HPL can be expressed as,…”

Section: Hpl and The Availability Of Plraimmentioning

confidence: 99%

A Holistic Approach to Guarantee the Reliability of Positioning Based on Carrier Phase for Indoor Pseudolite

et al. 2020

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“…Zhang et al used carrier interferometry to conduct analyses on indoor pseudolite positioning [ 7 ]. Li et al used the improved particle swarm algorithm to improve the search efficiency of AFM to achieve high precision positioning of a single epoch and the precision can reach the centimeter level [ 8 ]. Fujii et al introduced a novel use of pseudolites to cope with pseudolites’ conventional problems.…”

Section: Introductionmentioning

confidence: 99%

“…The most popular method is LAMBDA [ 16 , 17 , 18 ]. This method is reliable and accurate, but a higher accuracy of initial values is needed in indoor pseudolite positioning [ 8 ]. On the acquisition of the initial values, due to the fixed constellation of the pseudolites, the static observations are almost the same.…”

Section: Introductionmentioning

confidence: 99%

A New Method of High-Precision Positioning for an Indoor Pseudolite without Using the Known Point Initialization

Zhao

Zhang

Guo

et al. 2018

Sensors

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Due to the great influence of multipath effect, noise, clock and error on pseudorange, the carrier phase double difference equation is widely used in high-precision indoor pseudolite positioning. The initial position is determined mostly by the known point initialization (KPI) method, and then the ambiguities can be fixed with the LAMBDA method. In this paper, a new method without using the KPI to achieve high-precision indoor pseudolite positioning is proposed. The initial coordinates can be quickly obtained to meet the accuracy requirement of the indoor LAMBDA method. The detailed processes of the method follows: Aiming at the low-cost single-frequency pseudolite system, the static differential pseudolite system (DPL) method is used to obtain the low-accuracy positioning coordinates of the rover station quickly. Then, the ambiguity function method (AFM) is used to search for the coordinates in the corresponding epoch. The real coordinates obtained by AFM can meet the initial accuracy requirement of the LAMBDA method, so that the double difference carrier phase ambiguities can be correctly fixed. Following the above steps, high-precision indoor pseudolite positioning can be realized. Several experiments, including static and dynamic tests, are conducted to verify the feasibility of the new method. According to the results of the experiments, the initial coordinates with the accuracy of decimeter level through the DPL can be obtained. For the AFM part, both a one-meter search scope and two-centimeter or four-centimeter search steps are used to ensure the precision at the centimeter level and high search efficiency. After dealing with the problem of multiple peaks caused by the ambiguity cosine function, the coordinate information of the maximum ambiguity function value (AFV) is taken as the initial value of the LAMBDA, and the ambiguities can be fixed quickly. The new method provides accuracies at the centimeter level for dynamic experiments and at the millimeter level for static ones.

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“…Global Navigation Satellite System (GNSS) positioning accuracy degrades significantly in indoor and urban canyon environments due to severe signal attenuations and multipath effects, which has been motivating researchers to explore alternative technologies for location-based service (LBS) in recent years [ 1 , 2 , 3 , 4 ]. GNSS-like positioning technologies, for example, pseudolite positioning systems (PLs) and GNSS repeater systems, have been extensively investigated for indoor and urban applications [ 5 , 6 , 7 ]. A pseudolite system employs signals the same as or similar to GPS signals for ranging [ 8 , 9 ].…”

Section: Introductionmentioning

confidence: 99%

A Low-Ambiguity Signal Waveform for Pseudolite Positioning Systems Based on Chirp

Liu

Huang

Kou

et al. 2018

Sensors

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Signal modulation is an essential design factor of a positioning system, which directly impacts the system’s potential performance. Chirp compressions have been widely applied in the fields of communication, radar, and indoor positioning owing to their high compression gain and good resistance to narrowband interferences and multipath fading. Based on linear chirp, we present a modulation method named chirped pseudo-noise (ChPN). The mathematical model of the ChPN signal is provided with its auto-correlation function (ACF) and the power spectrum density (PSD) derived. The ChPN with orthogonal chirps is also discussed, which has better resistance to near-far effect. Then the generation and detection methods as well as the performances of ChPN are discussed by theoretical analysis and simulation. The results show that, for ChPN signals with the same main-lobe bandwidth (MLB), generally, the signal with a larger sweep bandwidth has better tracking precision and multipath resistance. ChPN yields slighter ACF peaks ambiguity due to its lower ACF side-peaks, although its tracking precision is a little worse than that of a binary offset carrier (BOC) with the same MLB. Moreover, ChPN provides better overall anti-multipath performance than BOC. For the ChPN signals with the same code rate, a signal with a larger sweep bandwidth has better performance in most aspects. In engineering practice, a ChPN receiver can be implemented by minor modifications of a BOC receiver. Thus, ChPN modulation shows promise for future positioning applications.

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A New Method for Single-Epoch Ambiguity Resolution with Indoor Pseudolite Positioning

Cited by 28 publications

References 41 publications

A Holistic Approach to Guarantee the Reliability of Positioning Based on Carrier Phase for Indoor Pseudolite

A Holistic Approach to Guarantee the Reliability of Positioning Based on Carrier Phase for Indoor Pseudolite

A New Method of High-Precision Positioning for an Indoor Pseudolite without Using the Known Point Initialization

A Low-Ambiguity Signal Waveform for Pseudolite Positioning Systems Based on Chirp

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