Concatenated Coding for GNSS Signals in Urban Environments

This work investigated concatenated coding schemes for Global Navigation Satellite System (GNSS) signals in order to increase their error correction capability in urban environments. In particular, a serial concatenated code that combines an outer Reed–Solomon (RS) code with an inner low-density parity-check (LDPC) code was designed, and the performance was investigated over the land mobile satellite (LMS) channel for characterizing multipath and shadow fading in urban environments. The performance of the proposed concatenated coding scheme was compared to that of a B-CNAV1 message, in which two interleaved 64-ary LDPC codes were employed. The simulation results demonstrate that the proposed concatenated code can obtain a similar error correction performance to the two interleaved 64-ary LDPC codes in both the additive white Gaussian noise (AWGN) and LMS channels at a lower complexity level.

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Simulation of GNSS Availability in Urban Environments Using a Panoramic Image Dataset

International Journal of Navigation and Observation ◽

10.1155/2017/8047158 ◽

2017 ◽

Vol 2017 ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

Sakpod Tongleamnak ◽

Masahiko Nagai

Keyword(s):

Urban Areas ◽

Accuracy Assessment ◽

Satellite System ◽

Urban Environments ◽

Panoramic Image ◽

Image Processing Techniques ◽

Gnss Positioning ◽

Image Dataset ◽

Global Navigation Satellite ◽

Processing Techniques

Performance of Global Navigation Satellite System (GNSS) positioning in urban environments is hindered by poor satellite availability because there are many man-made and natural objects in urban environments that obstruct satellite signals. To evaluate the availability of GNSS in cities, this paper presents a software simulation of GNSS availability in urban areas using a panoramic image dataset from Google Street View. Photogrammetric image processing techniques are applied to reconstruct fisheye sky view images and detect signal obstacles. Two comparisons of the results from the simulation and real world observation in Bangkok and Tokyo are also presented and discussed for accuracy assessment.

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A Multi-Sensor Tight Fusion Method Designed for Vehicle Navigation

Sensors ◽

10.3390/s20092551 ◽

2020 ◽

Vol 20 (9) ◽

pp. 2551 ◽

Cited By ~ 1

Author(s):

Qifeng Lai ◽

Hong Yuan ◽

Dongyan Wei ◽

Ningbo Wang ◽

Zishen Li ◽

...

Keyword(s):

Navigation System ◽

Rapid Development ◽

Satellite System ◽

Urban Environments ◽

Sensor Technology ◽

Vehicle Navigation ◽

Noise Compensation ◽

Vehicle Navigation System ◽

Tightly Coupled ◽

Global Navigation Satellite

Using the Global Navigation Satellite System (GNSS), it is difficult to provide continuous and reliable position service for vehicle navigation in complex urban environments, due to the natural vulnerability of the GNSS signal. With the rapid development of the sensor technology and the reduction in their costs, the positioning performance of GNSS is expected to be significantly improved by fusing multi-sensors. In order to improve the continuity and reliability of the vehicle navigation system, we proposed a multi-sensor tight fusion (MTF) method by combining the inertial navigation system (INS), odometer, and barometric altimeter with the GNSS technique. Different fusion strategies were presented in the open-sky, insufficient satellite, and satellite outage environments to check the performance improvement of the proposed method. The simulation and real-device tests demonstrate that in the open-sky context, the error of sensors can be estimated correctly. This is useful for sensor noise compensation and position accuracy improvement, when GNSS is unavailable. In the insufficient satellite context (6 min), with the help of the barometric altimeter and a clock model, the accuracy of the method can be close to that in the open-sky context. In the satellite outage context, the error divergence of the MTF is obviously slower than the traditional GNSS/INS tightly coupled integration, as seen by odometer and barometric altimeter assisting.

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Feature-Aided RTK/LiDAR/INS Integrated Positioning System with Parallel Filters in the Ambiguity-Position-Joint Domain for Urban Environments

Remote Sensing ◽

10.3390/rs13102013 ◽

2021 ◽

Vol 13 (10) ◽

pp. 2013

Author(s):

Wenyi Li ◽

Gang Liu ◽

Xiaowei Cui ◽

Mingquan Lu

Keyword(s):

Satellite System ◽

Urban Environments ◽

Integrated System ◽

Integrated Systems ◽

Loose Coupling ◽

Positioning Precision ◽

Cycle Slips ◽

Global Positioning ◽

Coupling Mode ◽

Global Navigation Satellite

As the modern navigation business evolves, demands for high-precision positioning in GNSS-challenged environments increase, and the integrated system composed of Global Navigation Satellite System (GNSS)-based Real-Time Kinematic (RTK), inertial system (INS), Light Detection and Ranging (LiDAR), etc., is accepted as the most feasible solution to the issue. For prior-map-free situations, as the only sensor with a global frame, RTK determines and maintains the global positioning precision of the integrated system. However, RTK performance degrades greatly in GNSS-challenged environments, and most of the existing integrated systems adopt loose coupling mode, which does nothing to improve RTK and, thus, prevents integrated systems from further improvement. Aiming at improving RTK performance in the RTK/LiDAR/INS integrated system, we proposed an innovative integrated algorithm that utilizes RTK to register LiDAR features while integrating the pre-registered LiDAR features to RTK and adopts parallel filters in the ambiguity-position-joint domain to weaken the effects of low satellite availability, cycle slips, and multipath. By doing so, we can improve the RTK fix rate and stability in GNSS-challenged environments. The results of the theoretical analyses, simulation experiments, and a road test proved that the proposed method improved RTK performance in GNSS-challenged environments and, thus, guaranteed the global positioning precision of the whole system.

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Serially Concatenated Low-density Parity Check Codes as Compatible Pairs

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i4.15.23013 ◽

2018 ◽

Vol 7 (4.15) ◽

pp. 301

Author(s):

Amjad Ali Jassim ◽

Wael A. Hadi. ◽

Muhanned Ismael Ibrahim Al-Firas

Keyword(s):

Additive White Gaussian Noise ◽

Ldpc Codes ◽

Ldpc Code ◽

Error Correction Codes ◽

Low Density ◽

Performance Error ◽

Decoder Complexity ◽

And Performance ◽

Serially Concatenated ◽

Ber Performance

Low-density parity checks (LDPC) codes are considered good performance error correction codes. However, decoder complexity increases with increasing code length. In this study, we introduce short-length serially concatenated LDPC codes. The proposed technique uses pairs of compatible LDPC codes that act as outer and inner serially concatenated codes. In this code pair, the inner code takes input that is the same length as the outer LDPC encoder output. This study examined two cases of LDPC codes as compatible pairs with low numbers of iterations and compared bit error rate (BER) performance to a standalone LDPC code with an additive white Gaussian noise channel. We also considered the quadrature phase shift keying QPSK, 16-quadrature amplitude modulation (QAM), and 64-QAM system modulation schemes. Simulation results demonstrate that the proposed system has good BER performance compared to a standalone LDPC code, the results summarized in table and performance curves.

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Semantic VPS for Smartphone Localization in Challenging Urban Environments

Sensors ◽

10.3390/s21186137 ◽

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.

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Background and Recent Advances in the Locata Terrestrial Positioning and Timing Technology

Sensors ◽

10.3390/s19081821 ◽

2019 ◽

Vol 19 (8) ◽

pp. 1821 ◽

Cited By ~ 1

Author(s):

Chris Rizos ◽

Ling Yang

Keyword(s):

Literature Review ◽

Global Navigation Satellite System ◽

Satellite System ◽

High Accuracy ◽

Urban Environments ◽

Navigation Satellite ◽

Positioning Systems ◽

Comprehensive Literature Review ◽

The World ◽

Global Navigation Satellite

Global Navigation Satellite System (GNSS) is the most widely used Positioning, Navigation, and Timing (PNT) technology in the world today, but it suffers some major constraints. Locata is a terrestrial PNT technology that can be considered as a type of localised “constellation”, which is able to provide high-accuracy PNT coverage where GNSS cannot be used. This paper presents a comprehensive literature review of the Locata technology and its applications. It seeks to answer questions, such as: (1) What is Locata and how does it work? (2) What makes Locata unique compared with other terrestrial positioning systems? (3) How has Locata been used in different applications for accurate PNT? (4) What are the current challenging issues that may restrict its further adoption for custom-grade navigation in urban environments?

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ANALYSIS OF THE FLOATING CAR DATA OF TURIN PUBLIC TRANSPORTATION SYSTEM: FIRST RESULTS

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-4-515-2018 ◽

2018 ◽

Vol XLII-4 ◽

pp. 515-521

Author(s):

R. Ravanelli ◽

M. Crespi

Keyword(s):

Public Transportation ◽

Low Cost ◽

Temporal Analysis ◽

Satellite System ◽

Transportation System ◽

Urban Environments ◽

Floating Car Data ◽

Public Transportation System ◽

Spatio Temporal ◽

Global Navigation Satellite

<p><strong>Abstract.</strong> Global Navigation Satellite System (GNSS) sensors represent nowadays a mature technology, low-cost and efficient, to collect large spatio-temporal datasets (Geo Big Data) of vehicle movements in urban environments. Anyway, to extract the mobility information from such Floating Car Data (FCD), specific analysis methodologies are required. In this work, the first attempts to analyse the FCD of the Turin Public Transportation system are presented. Specifically, a preliminary methodology was implemented, in view of an automatic and possible real-time impedance map generation. The FCD acquired by all the vehicles of the Gruppo Torinese Trasporti (GTT) company in the month of April 2017 were thus processed to compute their velocities and a visualization approach based on Osmnx library was adopted. Furthermore, a preliminary temporal analysis was carried out, showing higher velocities in weekend days and not peak hours, as could be expected. Finally, a method to assign the velocities to the line network topology was developed and some tests carried out.</p>

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MIMO-Filtered OFDM System Improvement Using Modified Concatenated RS/LDPC Codes

10.21203/rs.3.rs-1022604/v1 ◽

2021 ◽

Author(s):

Ghasan Ali Hussain

Keyword(s):

Wireless Communication ◽

Communication Systems ◽

Ldpc Codes ◽

Ldpc Code ◽

Error Rates ◽

Wireless Communication Systems ◽

Ofdm System ◽

Rs Codes ◽

Concatenated Code ◽

Ber Performance

Abstract In mobile communication systems, there are errors that will be generated in the digital signal due to fading and interference. Consequently, different techniques are used to improve the system's reliability and enhance the signal's robustness. Channel coding techniques are used to enhance the system reliability of 5G wireless communication systems . In the upcoming wireless technologies, LDPC codes are still introduced as an alternative to turbo codes. However, the error floor phenomenon is one of the biggest demerits of using LDPC code in the different communication systems that need low error rates. This paper uses RS codes with LDPC codes in a concatenated code to solve this demerit of LDPC codes. Meanwhile, a modified concatenated RS/LDPC codes are created using outer RS codes with inner LDPC codes then appended by interleaver, unlike the conventional concatenated codes that use the interleaver between both codes. Thereafter, the modified concatenated RS/LDPC codes were suggested to enhance BER performance for the f-OFDM system. The results showed that using the proposed concatenated code outperformed using single and familiar concatenated RS/LDPC code in terms of improving BER performance. Meanwhile, the proposed system achieved lower OOBE values than the conventional OFDM system. Therefore, the resulted system can be introduced as a competitor candidate for 5G wireless communication systems due to these features

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Smartphone Shadow Matching for Better Cross-street GNSS Positioning in Urban Environments

Journal of Navigation ◽

10.1017/s0373463314000836 ◽

2014 ◽

Vol 68 (3) ◽

pp. 411-433 ◽

Cited By ~ 51

Author(s):

Lei Wang ◽

Paul D Groves ◽

Marek K Ziebart

Keyword(s):

Large Scale ◽

Signal To Noise Ratio ◽

Three Dimensional ◽

Satellite System ◽

Urban Environments ◽

Line Of Sight ◽

Measured Signal ◽

Gnss Positioning ◽

Global Navigation Satellite ◽

Dense Urban Environment

Global Navigation Satellite System (GNSS) shadow matching is a new positioning technique that determines position by comparing the measured signal availability and strength with predictions made using a three-dimensional (3D) city model. It complements conventional GNSS positioning and can significantly improve cross-street positioning accuracy in dense urban environments. This paper describes how shadow matching has been adapted to work on an Android smartphone and presents the first comprehensive performance assessment of smartphone GNSS shadow matching. Using GPS and GLONASS data recorded at 20 locations within central London, it is shown that shadow matching significantly outperforms conventional GNSS positioning in the cross-street direction. The success rate for obtaining a cross-street position accuracy within 5 m, enabling the correct side of a street to be determined, was 54·50% using shadow matching, compared to 24·77% for the conventional GNSS position. The likely performance of four-constellation shadow matching is predicted, the feasibility of a large-scale implementation of shadow matching is assessed, and some methods for improving performance are proposed. A further contribution is a signal-to-noise ratio analysis of the direct line-of-sight and non-line-of-sight signals received on a smartphone in a dense urban environment.

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