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Pseudolite positioning system can enhance GNSS (Global Navigation Satellite System) by improving satellite geometry and providing services independently in the GNSS unavailable environment. Many error items of pseudolite positioning system, e.g., tropospheric delay error, need to be corrected by an accurate model. While several tropospheric delay models suitable for pseudolite positioning systems have been proposed, the key parameters indicating the upper boundaries for tropospheric refraction are fixed to an experimental value in these models. In this paper, we studied the spatiotemporal characteristics of the upper boundary heights for hydrostatic and wet tropospheric delay based on the ERA5 global meteorological reanalysis data. With the refined height boundary term, we refine four existing tropospheric delay models for pseudolite positioning systems, including RTCA, MRTCA, Bouska and Hopfield models. To evaluate the performance of the refined models, we selected 12 airports distributed globally as experimental areas and analyzed the error characteristics of the four refined tropospheric models and the LTC model (independent of height). The experimental results show that when the slant distance between the pseudolite base station and the receiver is constant at 5 km, the MRTCA model has the best performance, with an RMSE (root mean square error) of about 0.15 m. When the elevation angle between the pseudolite base station and the receiver is constant, the RMSE of the LTC model is the smallest at the low elevation angle, and the RMSE of the MRTCA model is the smallest at the high elevation. The RMSE of pseudolite tropospheric delay models show seasonal variation. [ABSTRACT FROM AUTHOR]

The location service is an important part of the smart city. A unified location service for outdoor and indoor/overground and underground activity will assist the construction of smart cities. However, with different coordinate systems and data formats, it is difficult to unify various positioning technologies on the same basis. Global navigation satellite system (GNSS)-based positioning is the only way to provide absolute location under the Earth-centered, Earth-fixed coordinate system (ECEF). Increasing indoor and underground human activity places significant demand on location-based services but no GNSS signals are available there. Fortunately, a type of satellite that is indoors, known as pseudolite, can transmit GNSS-like ranging signals. Users can obtain their position by receiving ranging signals and their resection without adding or switching other sensors when they go from outdoors to indoors. To complete the outreach of the GNSS indoors and underground to support the smart city, how to adapt the pseudolite design and unify coordinate frames for linking to the GNSS remain to be determined. In this regard, we provide an overview of the history of the research and application of pseudolites, the research progress from both the system side and the user side, and the plans for pseudolite-based location services in smart cities.

Among many indoor positioning technologies, pseudolite positioning technology has become an important supplement to GNSS. In indoor open environments, pseudolite positioning technology can usually perform high-precision positioning. However, in a complex environment, the pseudolite receiver is seriously interfered by multipath and other interference signals, which will lead to a serious decline in the observation accuracy, signal lock loss or even no positioning results. Therefore, this work proposes a pseudolite indoor anti-multipath receiver based on reference multipath estimating delay lock loop (Ref-MEDLL). It adds the Ref-MEDLL multipath estimator module and the multipath mitigation module to the traditional receiver signal processing architecture. In the multipath mitigation module, the multipath estimation adaptive mitigation of vector tracking (MEAM-VT) method and the multipath estimation direct mitigation (MEDM) method for multipath mitigation is proposed. Experimental results show that the Ref-MEDLL multipath estimation method has good adaptability to multipath signals that have different time delays and different amplitudes; both the MEDM receiver and the MEAM-VT receiver have good multipath mitigation performance. The MEAM-VT method performs better than the MEDM method in multipath mitigation and tracking, but the stability of the pseudorange observations of the MEAM-VT method is not as good as that of the MEDM method. The positioning accuracy of the MEDM receiver and the MEAM-VT receiver has been improved to different degrees in static positioning experiments and dynamic positioning experiments. [ABSTRACT FROM AUTHOR]

Copyright of Systems Engineering & Electronics is the property of Journal of Systems Engineering & Electronics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Precise drilling and excavation in future Lunar mining sites as well as in building habitats areas will be supported by robotized instrumentation. To ensure accurate positioning of facilities or structures, customized surveying instruments will be used to perform measurements needed for calculating locations of surveyed objects. Precise positioning in unexplored areas is difficult, even on the Earth, with all available support. This issue becomes even more complex on the Moon's surface, considering environmental conditions and the absence of Earth logistics. This paper solves a problem of centimeter-precision positioning on the Moon's surface. The solution is called Lunar Regional Navigation Transceiver System (LRNTS). It is based on a network of transceiver facilities, holding onboard both navigation transmitters and receivers. Transmitting modules of LRNTS act in the same way as the Global Navigation Satellite Systems (GNSS) space segment, sending navigation messages to the receivers. Receiving modules are needed for self-calibration of LRNTS to calculate their coordinates. In this paper, 12 different LRNTS-simulated configuration setups within Shackleton Crater are tested against positioning accuracy and visibility along the crater. The results show that LRNTS of nine transceivers can achieve sub-centimeter horizontal and better than 2 cm vertical accuracy, with consistent visibility of six and more transceivers throughout the Shackleton Crater. [ABSTRACT FROM AUTHOR]

Ground-based positioning systems (GBPSs) can serve as a supplement and backup to global navigation satellite systems. GBPSs are known for their low cost and high flexibility, but most of them have difficulty in achieving rapid deployment and operation, since the coordinates of transmitters rely on external precise measurements. Several existing self-calibration methods based on carrier phase measurements require known points of GBPS transmitters or receivers, which implies dependence on external measurements. This paper proposes an autonomous coordinate establishment (ACE) method without using known reference points for GBPSs. ACE utilizes a kinematic receiver to collect carrier phase measurements and employs a three-step procedure to establish a regional coordinate system. In the first step, ACE uses the properties of matrix structures to decouple generalized ambiguities and coordinates. Then, ACE obtains the rough estimation of the transmitter coordinates via multi-dimensional scaling in the second step. In the third step, ACE refines the estimate by solving a least squares problem which would be difficult to solve without the previous two steps. Numerical simulations and a real-world experiment show that the coordinate estimation of ACE can achieve decimeter to centimeter-level accuracy. The proposed method enables rapid deployment and operation for GBPSs. [ABSTRACT FROM AUTHOR]

Global navigation satellite systems (GNSS) precise point positioning (PPP) allows a user to perform high-accuracy absolute positioning using a stand-alone receiver. However, a long convergence time for GNSS PPP is a critical obstacle to its wide application. Since pseudolites (PLs) are relatively close to receivers, moving receivers can produce rapid spatial geometry changes, which facilitates the fast convergence of parameters. Based on this advantage of the pseudolite system (PLS), we investigate the PLS-augmented GNSS real-time kinematic PPP. Single-frequency PLS raw observations are combined with dual-frequency GNSS raw observations by an undifferenced and uncombined PPP model to augment the GNSS PPP. A real-world experiment demonstrated that the convergence time was dramatically shortened by 99.5% from about 900 s to nearly 4 s using PLS augmentation. In the 900-s sessions, the average success rate of GNSS ambiguity resolution can reach approximately 90% using PLS augmentation. Furthermore, PLS-augmented GNSS PPP showed a better positioning accuracy compared with GNSS-only PPP. The contributions of the PLS are still remarkable even with a short-time PLS augmentation. For example, after position parameters converged, if PLS can provide another 8-s augmentation, GNSS ambiguity parameters will also converge, then GNSS PPP can work independently and provide continuous high-precision positioning. In addition, longer augmentation times can promote higher success rates of GNSS ambiguity resolution. In summary, the positioning accuracy, convergence speed, and success rate of GNSS ambiguity resolution of GNSS PPP are significantly improved using PLS augmentation. [ABSTRACT FROM AUTHOR]

Among many indoor positioning technologies, pseudolite positioning technology has become an important supplement to GNSS. In indoor open environments, pseudolite positioning technology can usually perform high-precision positioning. However, in a complex environment, the pseudolite receiver is seriously interfered by multipath and other interference signals, which will lead to a serious decline in the observation accuracy, signal lock loss or even no positioning results. Therefore, this work proposes a pseudolite indoor anti-multipath receiver based on reference multipath estimating delay lock loop (Ref-MEDLL). It adds the Ref-MEDLL multipath estimator module and the multipath mitigation module to the traditional receiver signal processing architecture. In the multipath mitigation module, the multipath estimation adaptive mitigation of vector tracking (MEAM-VT) method and the multipath estimation direct mitigation (MEDM) method for multipath mitigation is proposed. Experimental results show that the Ref-MEDLL multipath estimation method has good adaptability to multipath signals that have different time delays and different amplitudes; both the MEDM receiver and the MEAM-VT receiver have good multipath mitigation performance. The MEAM-VT method performs better than the MEDM method in multipath mitigation and tracking, but the stability of the pseudorange observations of the MEAM-VT method is not as good as that of the MEDM method. The positioning accuracy of the MEDM receiver and the MEAM-VT receiver has been improved to different degrees in static positioning experiments and dynamic positioning experiments.

At present, the interaction mechanism between the complex indoor environment and pseudolite signals has not been fundamentally resolved, and the stability, continuity, and accuracy of indoor positioning are still technical bottlenecks. In view of the shortcomings of the existing indoor fingerprint positioning methods, this paper proposes a hybrid CSI fingerprint method for indoor pseudolite positioning based on Ray Tracing and artificial neural network (RT-ANN), which combines the advantages of actual acquisition, deterministic simulation, and artificial neural network, and adds the simulation CSI feature parameters generated by modeling and simulation to the input of the neural network, extending the sample features of the neural network input dataset. Taking an airport environment as an example, it is proved that the hybrid method can improve the positioning accuracy in the area where the fingerprints have been collected, the positioning error is reduced by 54.7% compared with the traditional fingerprint positioning method. It is also proved that preliminary positioning can be completed in the area without fingerprint collection. [ABSTRACT FROM AUTHOR]

Advantages of Global Navigation Satellite System (GNSS) in precise and reliable localization can be exploited to enable low-cost and train-centric railway train control systems by reducing track-side facilities like Balises and track circuits. However, constrained observability of satellite signals in specific railway station areas leads to a great challenge to the continuity and availability of GNSS-based train positioning. The pseudolite (PL) technology has a great potential for seamless localization under GNSS-challenged or even signal-denied environments. In this paper, we consider the optimized solution of pseudolite constellation design for seamless train positioning in railway station environments. An integrated train positioning architecture is presented based on a combined GNSS/PL measurement model. Using the trackmap, the proposed solution firstly establishes a feature point set covering all tracks in the station by extracting key Points-of-interest (POIs) from track database. Based on that, a K-means-enhanced generalized center-guided firefly algorithm (KGFA) is proposed to improve the standard firefly algorithm (FA) for deriving an optimized pseudolite constellation solution. The performance indicator for each candidate pseudolite layout scheme is defined according to the scenario-based GNSS/PL constellation configuration. The capability of the KGFA-enabled solution is validated by comparisons with similar FA methods. Through a case study, performance of the optimized pseudolite constellation and its influence to GNSS/PL-based seamless train positioning have been demonstrated over the involved reference pseudolite layout strategies. It is noteworthy that the proposed solution enables the enhanced inherent capability of the local pseudolite network to achieve seamless train positioning over the conventional GNSS-alone train positioning mode. [ABSTRACT FROM AUTHOR]

The article explores the problem of alternative navigation support for high-precision weapons that use guidance based on signals from global navigation systems. It proposes the use of an autonomous navigation system replacing satellite navigation in the case where major Global Positioning System-like systems are unavailable. It suggests the idea and the model of a moving navigation field that can move along the weapon trajectory. The model of accuracy for the pseudolite navigation system uses the least squares method as its basis. The study looks into the accuracy parameters of the moving navigation field. The results of the study show the advantages of a moving field when compared with a stationary navigation field in case of autonomous use. This research also shows the possibility of using an autonomous system for Special Forces, search and rescue operations, and robotic and unmanned aerial, ground, and sea-based vehicles. [ABSTRACT FROM AUTHOR]

Precise drilling and excavation in future Lunar mining sites as well as in building habitats areas will be supported by robotized instrumentation. To ensure accurate positioning of facilities or structures, customized surveying instruments will be used to perform measurements needed for calculating locations of surveyed objects. Precise positioning in unexplored areas is difficult, even on the Earth, with all available support. This issue becomes even more complex on the Moon’s surface, considering environmental conditions and the absence of Earth logistics. This paper solves a problem of centimeter-precision positioning on the Moon’s surface. The solution is called Lunar Regional Navigation Transceiver System (LRNTS). It is based on a network of transceiver facilities, holding onboard both navigation transmitters and receivers. Transmitting modules of LRNTS act in the same way as the Global Navigation Satellite Systems (GNSS) space segment, sending navigation messages to the receivers. Receiving modules are needed for self-calibration of LRNTS to calculate their coordinates. In this paper, 12 different LRNTS-simulated configuration setups within Shackleton Crater are tested against positioning accuracy and visibility along the crater. The results show that LRNTS of nine transceivers can achieve sub-centimeter horizontal and better than 2 cm vertical accuracy, with consistent visibility of six and more transceivers throughout the Shackleton Crater.

For indoor high-accuracy positioning based on pseudolites (PLs), it is difficult to eliminate the effect of carrier phase advances or delays caused by the antenna through the use of differencing techniques because the line-of-sight between different transmitter–receiver pairs in a small area differs greatly. Therefore, antenna calibration is necessary. We propose a portable anechoic chamber-type calibration method based on the use of a transceiver unit that can calibrate both receiver and transmitter antennas. We also propose a method to monitor the variations in hardware delay that are likely due to the temperature variations. Because our method does not use an expensive anechoic chamber, a multipath error is a serious problem that cannot be ignored. In order to randomize the multipath errors, multiple calibrations can be performed at different sites to improve the accuracy of calibrations. The experiment we conducted showed that the antenna phase pattern accuracy of the proposed calibration method could reach millimeter level. In the indoor positioning experiment, the results, with phase center corrections, showed much better positioning accuracy of 6.9, 4.0 and 10.8 mm in X, Y and Z directions, respectively, compared with 9.1, 6.5 and 23.1 mm in X,Y and Z directions, respectively, without phase center correction. [ABSTRACT FROM AUTHOR]

In order to solve the limitation of traditional Kalman filter in dealing with nonlinear system and the problem of divergence and poor accuracy of extended Kalman filter (EKF) in dealing with strong nonlinear system, a dynamic tracking and positioning algorithm based on square root UKF was proposed based on the unscented Kalman filter (UKF) algorithm in combination with the problem of target tracking and positioning in dynamic navigation system. In the process of recursive operation, the square root of covariance matrix was used to replace the covariance matrix in the calculation process of covariance algorithm. The MATLAB simulation results show that the accuracy of the square root UKF algorithm is 54.7% higher than that of the EKF algorithm, and 14.8% higher than that of the UKF algorithm. The proposed algorithm solves the limitation of Kalman processing nonlinear system and the problem of the low accuracy of traditional EKF and UKF algorithms, and provides a strong support for the high-precision positioning of pseudolite system.

Global navigation satellite systems (GNSS) can provide high-accuracy positioning services in the open environment, while they have poor performance in shadowed regions. Pseudolite (PL) systems, with flexible deployment, can carry on the role of GNSS to provide high-accuracy positioning services in the case of GNSS failure. Ground-based precise point positioning (gPPP) for pseudolite systems allows a user to use a stand-alone receiver to achieve centimeter-level positioning, but without integer ambiguity resolution (IAR). The purpose of this work is to transfer the GNSS precise point positioning-real-time kinematic (PPP-RTK) technology to a ground-based pseudolite system, referred to as gPPP-RTK, for faster convergence and higher accuracy compared to gPPP by achieving IAR. However, the estimation of transmitter phase biases (TPBs) is the core for gPPP-RTK. Therefore, based on our independently developed pseudolite system, we propose a method to estimate the TPBs and analyze their characteristics. In this study, it is shown that the TPBs are rather stable in time unless the PL system is restarted. As a result, the TPBs do not need to be broadcast to users frequently. A real-world gPPP-RTK experiment demonstrated that the convergence time dramatically shortened the horizontal and vertical components by 42% and 59%, respectively, compared with gPPP. Furthermore, gPPP-RTK showed a better positioning accuracy of 1.86 and 4.06 cm in the horizontal and vertical components, respectively, compared with that of 2.00 and 10.00 cm for gPPP. The performances of convergence time and positioning accuracy in the vertical component are significantly better than that in the horizontal component. [ABSTRACT FROM AUTHOR]

A single-transmitter-based positioning system using an antenna array has been designed and developed to minimize the number of transmitters needed for environments where satellite-based navigation systems are unavailable. One of its suitable applications is for indoor navigation. The user receives the signals from the antenna array and calculates the position using the carrier-phase measurements. A key feature of the system is that the number of cycle ambiguity candidates is geometrically bounded. If the length of the antenna baseline is smaller than half the wavelength, the ambiguity resolution process is unnecessary. To improve the positioning performance for practical use, the antenna baseline must be enlarged. Even in this case, the cycle ambiguity resolution issue can be resolved fast and accurately. For instance, there are only nine candidates according to the setting of the study. To investigate the performance of the system, experiments for a dynamic rover using multiple “pseudolites,” pseudo-satellite transmitters, were conducted. In addition, low-cost inertial measurement unit (IMU) sensors were combined to investigate the improved positioning accuracy. Experimental results showed that positioning root-mean-square errors were 18 cm and 25 cm with IMU and without IMU, respectively, at the scale of a conventional meeting room. All integer-cycle ambiguities were solved accurately during the experiments, and more than 93% were resolved within 5 s.

This article presents an indoor infant monitoring system based on Android system which employs a low-cost Bluetooth Low Energy (BLE) pseudolite to accurately locate the infants in the activity indoors and timely remind the parents. It can achieve a positioning accuracy better than 2 m and effectively reduce the risk of injury to infants and young children. The performance of the proposed system, using false negative rate, false alarm rate, and alarm response time as indicators, is compared with that of the system using Quuppa as a positioning source. The experiment results show that both BLE pseudolite and Quuppa as a positioning source can basically meet the positioning accuracy for the infant monitoring system, but the BLE-pseudolite-based system provides a more cost-efficient solution.

At present, the interaction mechanism between the complex indoor environment and pseudolite signals has not been fundamentally resolved, and the stability, continuity, and accuracy of indoor positioning are still technical bottlenecks. In view of the shortcomings of the existing indoor fingerprint positioning methods, this paper proposes a hybrid CSI fingerprint method for indoor pseudolite positioning based on Ray Tracing and artificial neural network (RT-ANN), which combines the advantages of actual acquisition, deterministic simulation, and artificial neural network, and adds the simulation CSI feature parameters generated by modeling and simulation to the input of the neural network, extending the sample features of the neural network input dataset. Taking an airport environment as an example, it is proved that the hybrid method can improve the positioning accuracy in the area where the fingerprints have been collected, the positioning error is reduced by 54.7% compared with the traditional fingerprint positioning method. It is also proved that preliminary positioning can be completed in the area without fingerprint collection.

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to achieve high precision of the time and frequency synchronization of pseudolite automatic network，a pseudolite time and frequency synchronization system using the structure of Self-Calibrating Pseudolite Array(SCPA) is designed. The system takes FPGA+DSP as the core processor, and integrates high-speed A/D, D/A conversion circuit and up and down converter circuit. The design and implementation of pseudolite two-way pseudo distance measurement technology and the time and frequency synchronization scheme are introduced in detail. The test results show that the phase synchronization error of carrier phase is less than 0.1 Hz and the time synchronization accuracy is better than 2 ns, which provids a significant guarantee for the positioning and timing accuracy of the pseudolite automatic system.

Clock synchronization is critical for synchronous pseudolite systems. Wireless synchronization methods are desirable for their flexibility in system deployment, and most of them build a tree topology of time information flow based on master‐slave synchronization between pseudolites. A slave pseudolite can receive signals broadcast by multiple pseudolites; however, existing methods usually utilize one signal and ignore others in which the time information could improve synchronization precision and reliability. We present a mesh topology based clock synchronization (MTCS) technique by utilizing all received signals. MTCS builds a mesh topology of time information flow, which can keep synchronization in case of link interruption or pseudolite failure. The coupling relationship of slave clocks is derived, and the influence of measurement biases is analyzed. As shown by both analysis and simulations, MTCS has better clock synchronization precision. When link interruption or pseudolite failures occur, MTCS is more robust than tree topology based methods. [ABSTRACT FROM AUTHOR]

When the ground-based pseudolite positioning system is independent networking, distribution of base station is a multi-objective optimization problem to improve the system signal coverage and optimize the geometric layout of the base stations, thereby reduces the number of base stations and ensures positioning accuracy. This paper proposed the pseudolite base station distribution method based on the non-dominated sorting genetic algorithm ( NSGA- II ) with elite strategy. The method used the visual domain analysis technology to calculate the system signal coverage and evaluate the geometric layout of the base stations by a weighted geometric precision factor of multi-matrix multiplication. Finally, the NSGA- II algorithm searched the non-dominated optimal solution set of two optimization targets. The simulation of a mountainous area in Zhangjiajie shows only 28 base stations can ensure the system signal coverage reach 90%. At the same time, base station geometry is also good, the performance is better than the traditional genetic algorithm, it has certain guiding significance in practical engineering applications. [ABSTRACT FROM AUTHOR]

This article presents an indoor infant monitoring system based on Android system which employs a low-cost Bluetooth Low Energy (BLE) pseudolite to accurately locate the infants in the activity indoors and timely remind the parents. It can achieve a positioning accuracy better than 2 m and effectively reduce the risk of injury to infants and young children. The performance of the proposed system, using false negative rate, false alarm rate, and alarm response time as indicators, is compared with that of the system using Quuppa as a positioning source. The experiment results show that both BLE pseudolite and Quuppa as a positioning source can basically meet the positioning accuracy for the infant monitoring system, but the BLE-pseudolite-based system provides a more cost-efficient solution. [ABSTRACT FROM AUTHOR]

Pseudolite deployment is the premise of ground-based pseudolite system networking, which affects the coverage and positioning accuracy of ground-based pseudolite systems. Optimal deployment algorithms can help to achieve a higher signal coverage and lower mean horizontal precision factor (HDOP) with a limited number of pseudolites. In this paper, we proposed a multi-objective particle swarm optimization (MOPSO) algorithm for the deployment of a ground-based pseudolite system. The new algorithm combines Digital Elevation Model (DEM) data and uses the mean HDOP of the DEM grid to measure the geometry of the pseudolite system. The signal coverage of the pseudolite system was calculated based on the visual area analysis with respect to reference planes, which effectively avoids the repeated calculation of the intersection and improves the calculation efficiency. A selected area covering 10 km×10 km in the Jiuzhaigou area of China was used to verify the new algorithm. The results showed that both the coverage and HDOP achieved were optimal using the new algorithm, where the coverage area can be up to approximately 50% and 30% more than using the existing particle swarm optimization (PSO) and convex polyhedron volume optimization (CPVO) algorithms, respectively.

Global navigation satellite systems are widely used across the world because of their continuous/all-weather, global coverage, and high precision positioning. But, three-dimensional positioning accuracy, especially in the vertical direction, remains insufficient because of the geometric distribution of satellites. This is especially true for air-borne objects such as unmanned aerial vehicles, civil aviation devices, and missiles. To solve this problem, we adopt a satellite-ground joint positioning system based on a pseudo-satellite (pseudolite). The introduction of ground pseudolites can significantly reduce the vertical dilution of precision and improve positioning accuracy. This method has been proposed in the 1980s. However, we have to ask a question, as long as we add a pseudolite, can the positioning accuracy be improved? The answer is no. Pseudolites can cause time synchronization problems with satellites, and the resulting timing errors of the pseudolite are converted into pseudorange errors, reducing accuracy. Here, we seek to evaluate the impact of the reduced vertical dilution of precision and the increased range errors associated with the introduction of a pseudolite on the ground. We derive a mathematical formula to explain this relationship. We conclude that when the satellite range error and the change in the position dilution of precision associated with a pseudolite are known, we can calculate an approximate limit for the pseudolite timing accuracy to ensure that the use of the pseudolite improves the positioning accuracy. This work should be of great value in guiding engineering practice. [ABSTRACT FROM AUTHOR]

Abstract In positioning technology, indoor positioning is known as the "last kilometer" problem because the global navigation satellite system (GNSS) cannot work indoors. A wide range of indoor positioning technologies have been developed, notably Bluetooth and Wi-Fi, and others using LED and ultra-wideband light sources. Although these technologies have had good success indoors, the indoor use of GNSS is still being pursued, and an indoor and outdoor joint location system remains a development aim. In this paper, we propose a new indoor positioning scheme that adopts pseudo-satellite (pseudolite) technology combined with a navigation signal simulator. Positioning is achieved by indoor pseudolite antennas that transmit the 'actual' satellite signals in space handled by the navigation signal simulator to an indoor user. However, the 'actual' satellite ephemeris stored in the pseudolites will bring false pseudoranges, which makes it necessary to adopt map matching technology to determine the real position. The results of our computer simulation showed that when the measurement error mainly multipath error in the room was within 1 m, the positioning results were better than 2 m in about 94% of instances. The proposed method provides a feasible solution for indoor and outdoor joint positioning. The advantages of this system include a better dilution-of-precision (DOP) than an independent pseudolite system indoors, no singular matrix, and initial point selection without limitation in the positioning equation. In addition, the introduction of a navigation signal simulator makes the system more flexible. [ABSTRACT FROM AUTHOR]

GNSS receiver could not be used in indoor environments. This paper proposes a novel pseudolite positioning approach utilizing carrier phase difference measurements, which can achieve sub-meter accuracy without the support of a base station, and without the need of synchronization between pseudolites. In addition, in the proposed approach, the integer ambiguity resolution is unnecessary as well. This research builds up system model for pseudolite positioning and proposes basic principle for this positioning method utilizing carrier phase difference measurements. First, two sets of carrier phase measurements output from a dual-antenna receiver are differentiated in order to cancel out the common errors. Then a non-linear least square adjustment method is used to solve spatial coordinates of center point of the dual-antenna iteratively. Simulation results and experiment outputs from a dual-antenna software receiver verified the feasibility of this approach. This pseudolite positioning approach can be regarded as an effective complement of existing indoor positioning techniques. [ABSTRACT FROM AUTHOR]

The Ground-based Radio Navigation System (GRNS) is an alternative/backup navigation system based on time synchronized pseudolites. It has been studied for some years due to the potential vulnerability issue of satellite navigation systems (e.g., GPS or Galileo). In the framework of our study, a periodic pulsed sequence was used instead of the randomized pulse sequence recommended as the RTCM (radio technical commission for maritime services) SC (special committee)-104 pseudolite signal, as a randomized pulse sequence with a long dwell time is not suitable for applications requiring high dynamics. This paper introduces a mathematical model of the post-correlation output in a navigation sensor, showing that the aliasing caused by the additional frequency term of a periodic pulsed signal leads to a false lock (i.e., Doppler frequency bias) during the signal acquisition process or in the carrier tracking loop of the navigation sensor. We suggest algorithms to resolve the frequency false lock issue in this paper, relying on the use of a multi-correlator. A flight test with an unmanned helicopter was conducted to verify the implemented navigation sensor. The results of this analysis show that there were no false locks during the flight test and that outliers stem from bad dilution of precision (DOP) or fluctuations in the received signal quality.

This paper presents an evaluation of real-time kinematic (RTK)/Pseudolite/landmarks assistance heuristic drift elimination (LAHDE)/inertial measurement unit-based personal dead reckoning systems (IMU-PDR) integrated pedestrian navigation system for urban and indoor environments. Real-time kinematic (RTK) technique is widely used for high-precision positioning and can provide periodic correction to inertial measurement unit (IMU)-based personal dead reckoning systems (PDR) outdoors. However, indoors, where global positioning system (GPS) signals are not available, RTK fails to achieve high-precision positioning. Pseudolite can provide satellite-like navigation signals for user receivers to achieve positioning in indoor environments. However, there are some problems in pseudolite positioning field, such as complex multipath effect in indoor environments and integer ambiguity of carrier phase. In order to avoid the limitation of these factors, a local search method based on carrier phase difference with the assistance of IMU-PDR is proposed in this paper, which can achieve higher positioning accuracy. Besides, heuristic drift elimination algorithm with the assistance of manmade landmarks (LAHDE) is introduced to eliminate the accumulated error in headings derived by IMU-PDR in indoor corridors. An algorithm verification system was developed to carry out real experiments in a cooperation scene. Results show that, although the proposed pedestrian navigation system has to use human behavior to switch the positioning algorithm according to different scenarios, it is still effective in controlling the IMU-PDR drift error in multiscenarios including outdoor, indoor corridor, and indoor room for different people.