scholarly journals A Fast Acquisition Algorithm Overcoming Fuzz Problems for TDDM Spread Spectrum Signal

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Fang Liu ◽  
Yongxin Feng
Keyword(s):  
Spread Spectrum ◽  
Phase Error ◽  
Satellite System ◽  
Position Estimation ◽  
Frequency Error ◽  
Next Generation ◽  
Error Message ◽  
Fast Acquisition ◽  
Global Navigation Satellite ◽  
Time Division

TDDM (time division data modulation) technique will be used in the next generation GNSS (global navigation satellite system) to improve processing performance and to reduce inter-GNSS interference; however, the emergence of TDDM signal causes the estimation frequency and message reversal fuzz problems in the acquisition process of a GNSS receiver. At present, the traditional acquisition methods have some limitations and shortcomings. Therefore, aiming at the unique characteristics of TDDM signal, a fast acquisition algorithm is proposed to overcome these fuzz problems in this paper. In the proposed algorithm, three stages are obtained by some key technologies, which are theI-Qfrequency compensation, superposition processing, subsection processing, and reversion position estimation. Besides, the algorithm is simulated from carrier frequency error, code phase error, message inversion error, and processing speed. Theoretical and simulation results show that the new algorithm can quickly overcome the fuzz problems, and the new algorithm is better than the existing algorithm in the speed and accuracy, which demonstrates that this new algorithm is an effective search scheme for the next generation GNSS signals.

scholarly journals Many Ways Lead to the Goal—Possibilities of Autonomous and Infrastructure-Based Indoor Positioning

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 397
Author(s):  
Hossein Shoushtari ◽  
Thomas Willemsen ◽  
Harald Sternberg
Keyword(s):  
Mobile Networks ◽  
Dead Reckoning ◽  
Simulated Data ◽  
Minimum Cost ◽  
Cost Effective ◽  
Satellite System ◽  
Position Estimation ◽  
Robust Solution ◽  
Position Data ◽  
Global Navigation Satellite

There are many ways to navigate in Global Navigation Satellite System-(GNSS) shaded areas. Reliable indoor pedestrian navigation has been a central aim of technology researchers in recent years; however, there still exist open challenges requiring re-examination and evaluation. In this paper, a novel dataset is used to evaluate common approaches for autonomous and infrastructure-based positioning methods. The autonomous variant is the most cost-effective realization; however, realizations using the real test data demonstrate that the use of only autonomous solutions cannot always provide a robust solution. Therefore, correction through the use of infrastructure-based position estimation based on smartphone technology is discussed. This approach invokes the minimum cost when using existing infrastructure, whereby Pedestrian Dead Reckoning (PDR) forms the basis of the autonomous position estimation. Realizations with Particle Filters (PF) and a topological approach are presented and discussed. Floor plans and routing graphs are used, in this case, to support PDR positioning. The results show that the positioning model loses stability after a given period of time. Fifth Generation (5G) mobile networks can enable this feature, as well as a massive number of use-cases, which would benefit from user position data. Therefore, a fusion concept of PDR and 5G is presented, the benefit of which is demonstrated using the simulated data. Subsequently, the first implementation of PDR with 5G positioning using PF is carried out.

scholarly journals Investigation of Tightly Combined Single-Frequency and Single-Epoch Precise Positioning Using Multi-GNSS Data

2020 ◽  
Vol 12 (2) ◽  
pp. 285
Author(s):  
Chenlong Deng ◽  
Qian Liu ◽  
Xuan Zou ◽  
Weiming Tang ◽  
Jianhui Cui ◽  
...  
Keyword(s):  
Satellite System ◽  
Position Estimation ◽  
Single Frequency ◽  
Navigation Satellite ◽  
Typical Situation ◽  
Practical Algorithms ◽  
Ambiguity Fixing ◽  
Global Navigation ◽  
Global Navigation Satellite ◽  
Tc Model

The loose combination (LC) and the tight combination (TC) are two different models in the combined processing of four global navigation satellite systems (GNSSs). The former is easy to implement but may be unusable with few satellites, while the latter should cope with the inter-system bias (ISB) and is applicable for few tracked satellites. Furthermore, in both models, the inter-frequency bias (IFB) in the GLObal NAvigation Satellite System (GLONASS) system should also be removed. In this study, we aimed to investigate the performance difference of ambiguity resolution and position estimation between these two models simultaneously using the single-frequency data of all four systems (GPS + GLONASS + Galileo + BeiDou Navigation Satellite System (BDS)) in three different environments, i.e., in an open area, with surrounding high buildings, and under a block of high buildings. For this purpose, we first provide the definition of ISB and IFB from the perspective of the hardware delays, and then propose practical algorithms to estimate the IFB rate and ISB. Thereafter, a comprehensive performance comparison was made between the TC and LC models. Experiments were conducted to simulate the above three observation environments: the typical situation and situations suffering from signal obstruction with high elevation angles and limited azimuths, respectively. The results show that in a typical situation, the TC and LC models achieve a similar performance. However, when the satellite signals are severely obstructed and few satellites are tracked, the float solution and ambiguity fixing rates in the LC model are dramatically decreased, while in the TC model, there are only minor declines and the difference in the ambiguity fixing rates can be as large as 30%. The correctly fixed ambiguity rates in the TC model also had an improvement of around 10%. Once the ambiguity was fixed, both models achieved a similar positioning accuracy.

scholarly journals An Optimization Synchronization Algorithm for TDDM Signal

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Fang Liu ◽  
Yongxin Feng
Keyword(s):  
Spread Spectrum ◽  
Sequence Structure ◽  
Estimation Formula ◽  
Synchronization Algorithm ◽  
Local Sequence ◽  
Threshold Mechanism ◽  
Global Navigation Satellite ◽  
Time Division ◽  
Synchronization Accuracy ◽  
Better Than

The time division data modulation (TDDM) mechanism is recommended to improve the communications quality and enhance the antijamming capability of the spread spectrum communication system, which will be used in the next generation global navigation satellite (GNSS) systems. According to the principle and the characteristics of TDDM signal, an optimization synchronization algorithm is proposed. In the new algorithm, the synchronization accuracy and environmental adaptability have been improved with the special local sequence structure, the multicorrelation processing, and the proportion threshold mechanism. Thus, the inversion estimation formula was established. The simulation results demonstrate that the new algorithm can eliminate the illegibility threat in the synchronization process and can adapt to a lower SNR. In addition, this algorithm is better than the traditional algorithms in terms of synchronization accuracy and adaptability.

scholarly journals Satellite Availability and Service Performance Evaluation for Next-Generation GNSS, RNSS and LEO Augmentation Constellation

2021 ◽  
Vol 13 (18) ◽  
pp. 3698
Author(s):  
Haomeng Cui ◽  
Shoujian Zhang
Keyword(s):  
Satellite System ◽  
Low Earth Orbit ◽  
Global Navigation Satellite Systems ◽  
Navigation Satellite ◽  
Next Generation ◽  
Satellite Systems ◽  
Satellite Visibility ◽  
Under Construction ◽  
Global Navigation Satellite ◽  
Average Position

Positioning accuracy is affected by the combined effect of user range errors and the geometric distribution of satellites. Dilution of precision (DOP) is defined as the geometric strength of visible satellites. DOP is calculated based on the satellite broadcast or precise ephemerides. However, because the modernization program of next-generation navigation satellite systems is still under construction, there is a lack of real ephemerides to assess the performance of next-generation constellations. Without requiring real ephemerides, we describe a method to estimate satellite visibility and DOP. The improvement of four next-generation Global Navigation Satellite Systems (four-GNSS-NG), compared to the navigation constellations that are currently in operation (four-GNSS), is statistically analyzed. The augmentation of the full constellation the Quasi-Zenith Satellite System (7-QZSS) and the Navigation with Indian Constellation (11-NavIC) for regional users and the low Earth orbit (LEO) constellation enhancing four-GNSS performance are also analyzed based on this method. The results indicate that the average number visible satellites of the four-GNSS-NG will reach 44.86, and the average geometry DOP (GDOP) will be 1.19, which is an improvement of 17.3% and 7.8%, respectively. With the augmentation of the 120-satellite mixed-orbit LEO constellation, the multi-GNSS visible satellites will increase by 5 to 8 at all latitudes, while the GDOP will be reduced by 6.2% on average. Adding 7-QZSS and 11-NavIC to the four-GNSS-NG, 37.51 to 71.58 satellites are available on global scales. The average position DOP (PDOP), horizontal DOP (HDOP), vertical DOP (VDOP), and time DOP (TDOP) are reduced to 0.82, 0.46, 0.67 and 0.44, respectively.

scholarly journals Semantic VPS for Smartphone Localization in Challenging Urban Environments

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6137
Author(s):  
Max Jwo Lem Lee ◽  
Li-Ta Hsu ◽  
Hoi-Fung Ng
Keyword(s):  
Smart Cities ◽  
Satellite System ◽  
Urban Environments ◽  
Position Estimation ◽  
Information Modeling ◽  
Position Information ◽  
Precise Position ◽  
Segmented Images ◽  
Building Information ◽  
Global Navigation Satellite

Accurate smartphone-based outdoor localization systems in deep urban canyons are increasingly needed for various IoT applications. As smart cities have developed, building information modeling (BIM) has become widely available. This article, for the first time, presents a semantic Visual Positioning System (VPS) for accurate and robust position estimation in urban canyons where the global navigation satellite system (GNSS) tends to fail. In the offline stage, a material segmented BIM is used to generate segmented images. In the online stage, an image is taken with a smartphone camera that provides textual information about the surrounding environment. The approach utilizes computer vision algorithms to segment between the different types of material class identified in the smartphone image. A semantic VPS method is then used to match the segmented generated images with the segmented smartphone image. Each generated image contains position information in terms of latitude, longitude, altitude, yaw, pitch, and roll. The candidate with the maximum likelihood is regarded as the precise position of the user. The positioning result achieved an accuracy of 2.0 m among high-rise buildings on a street, 5.5 m in a dense foliage environment, and 15.7 m in an alleyway. This represents an improvement in positioning of 45% compared to the current state-of-the-art method. The estimation of yaw achieved accuracy of 2.3°, an eight-fold improvement compared to the smartphone IMU.

scholarly journals A Fine-Tuned Positioning Algorithm for Space-Borne GNSS Timing Receivers

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2327 ◽  
Author(s):  
Xi Chen ◽  
QiHui Wei ◽  
YaFeng Zhan ◽  
TianYi Ma
Keyword(s):  
High Performance ◽  
Algorithm Design ◽  
Satellite System ◽  
Frequency Error ◽  
Satellite Position ◽  
Cubature Kalman Filter ◽  
Rms Error ◽  
Adverse Influence ◽  
Global Navigation Satellite ◽  
Positioning Algorithm

To maximize the usage of limited transmission power and wireless spectrum, more communication satellites are adopting precise space–ground beam-forming, which poses a rigorous positioning and timing requirement of the satellite. To fulfill this requirement, a space-borne global navigation satellite system (GNSS) timing receiver with a disciplined high-performance clock is preferable. The space-borne GNSS timing receiver moves with the satellite, in contrast to its stationary counterpart on ground, making it tricky in its positioning algorithm design. Despite abundant existing positioning algorithms, there is a lack of dedicated work that systematically describes the delicate aspects of a space-borne GNSS timing receiver. Based on the experimental work of the LING QIAO (NORAD ID:40136) communication satellite’s GNSS receiver, we propose a fine-tuned positioning algorithm for space-borne GNSS timing receivers. Specifically, the proposed algorithm includes: (1) a filtering architecture that separates the estimation of satellite position and velocity from other unknowns, which allows for a first estimation of satellite position and velocity incorporating any variation of orbit dynamics; (2) a two-threshold robust cubature Kalman filter to counteract the adverse influence of measurement outliers on positioning quality; (3) Reynolds averaging inspired clock and frequency error estimation. Hardware emulation test results show that the proposed algorithm has a performance with a 3D positioning RMS error of 1.2 m, 3D velocity RMS error of 0.02 m/s and a pulse per second (PPS) RMS error of 11.8ns. Simulations with MATLAB show that it can effectively detect and dispose outliers, and further on outperforms other algorithms in comparison.

scholarly journals The Single-Shore-Station-Based Position Estimation Method of an Automatic Identification System

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1590 ◽  
Author(s):  
Yi Jiang ◽  
Kai Zheng
Keyword(s):  
Estimation Method ◽  
Satellite System ◽  
Position Estimation ◽  
Automatic Identification ◽  
Identification System ◽  
Automatic Identification System ◽  
Shore Station ◽  
Position Data ◽  
Positioning Method ◽  
Global Navigation Satellite

In order to overcome the vulnerability of the Global Navigation Satellite System (GNSS), the International Maritime Organization (IMO) initiated the ranging mode (R-Mode) of the automatic identification system (AIS) to provide resilient position data. As the existing AIS is a communication system, the number of shore stations as reference stations cannot satisfy positioning requirements. Especially in the area near a shore station, it is very common that a vessel can only receive signals from one shore station, where the traditional positioning method cannot be used. A novel position estimation method using multiple antennas on shipborne equipment is proposed here, which provides a vessel’s position even though the vessel can only receive signals from a single shore station. It is beneficial for solving positioning issues in proximity to the coast. Further, as the distances between different antennas to the shore station are not sufficiently independent, the positioning matrix can easily be near singularity or ill-conditioned; thus, an effective position solving method is derived. Furthermore, the proposed method is verified and evaluated in different scenarios by numerical simulation. We assessed the influencing factors of positioning performance, such as the vessel’s heading angle, the relative position, and the distances between the shore station and the vessel. The proposed method widely expands the application scope of the AIS R-Mode positioning system.

scholarly journals Optimal Particle Filter Weight for Bayesian Direct Position Estimation in a GNSS Receiver

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2736 ◽  
Author(s):  
Jürgen Dampf ◽  
Kathrin Frankl ◽  
Thomas Pany
Keyword(s):  
Numerical Evaluation ◽  
Probability Distributions ◽  
Satellite System ◽  
Position Estimation ◽  
Logarithmic Scale ◽  
Satellite Clock ◽  
Signal Model ◽  
Stochastic Signal ◽  
Global Navigation Satellite ◽  
Particle Weight

Direct Position Estimation (DPE) is a rather new Global Navigation Satellite System (GNSS) technique to estimate the user position, velocity and time (PVT) directly from correlation values of the received GNSS signal with receiver internal replica signals. If combined with Bayesian nonlinear filters—like particle filters—the method allows for coping with multi-modal probability distributions and avoids the linearization step to convert correlation values into pseudoranges. The measurement update equation (particle weight update) is derived from a standard GNSS signal model, but we show that it cannot be used directly in a receiver implementation. The numerical evaluation of the formulas needs to be carried out in a logarithmic scale including various normalizations. Furthermore, the residual user range errors (coming from orbit, satellite clock, multipath or ionospheric errors) need to be included from the very beginning in the stochastic signal model. With these modifications, sensible probability functions can be derived from the GNSS multi-correlator values. The occurrence of multipath yields a natural widening of the probability density function. The approach is demonstrated with simulated and real-world

Research on the High-Precision Phase Simulation of DSSS Signal

2013 ◽  
Vol 712-715 ◽  
pp. 1987-1994
Author(s):  
Shi Wen Li ◽  
Peng Xu
Keyword(s):  
High Precision ◽  
Spread Spectrum ◽  
Carrier Phase ◽  
Satellite System ◽  
Direct Sequence Spread Spectrum ◽  
Direct Sequence ◽  
Frequency Signal ◽  
Generating Method ◽  
Precision Phase ◽  
Global Navigation Satellite

In order to meet the developing requirements of the high-precision GNSS(Global Navigation Satellite System) receiver and spread-spectrum TT&C equipment, we researched high-precision simulating technology of DSSS (Direct Sequence Spread Spectrum) signal and proposed simulating technology of carrier phase and pseudo code phase based on correction technology online. This technology avoids sacrificing implement slice to improve phase precision and can simulate relative motion between receiver and object. In this paper, high-precision generating method of digital middle frequency signal is focused on. The effectiveness of this algorithm has been corroborated by theoretical analysis, simulation and applied to some spaceflight simulator successfully.

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