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2022 Vol. 47, No. 5

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Research on integrated signal design for navigation, communication and detection

WANG Tengfei, YAO Zheng, LU Mingquan

2022, 47(5): 1-8. doi: 10.12265/j.gnss.2022112

[Abstract](391) [FullText HTML] (113) [PDF 2098KB](77)

Abstract:
As the modern society is changing from the information age to the intelligent age, the number and performance requirements of navigation, communication and detection signals have increased dramatically, and the demand for multi-functional integrated signals is becoming more and more urgent. In this field, it is a crucial issue to achieve efficient utilization of resources and dynamic adjustment of functions through flexible signal design. This paper first proposes a signal design framework based on the idea of “building blocks”. The designed signals are represented in the form of signal vectors and waveform basis functions. The corresponding signal design can be equivalently represented by reconstructing the signal vector with the coefficient combinations of the basis functions, thereby converting the signal optimization in the waveform space into the vector optimization in the signal space. Further, this paper analyzes the traditional signal evaluation methods, and derives the navigation, communication, and detection signal evaluation criteria under the integrated signal design framework. Finally, this paper proposes quantifiable optimization objectives for integrated signal design, and makes some discussion on design constraints, including energy constraints, spectrum constraints, peak-to-average ratio, etc.

Optimization design method for low earth orbit navigation constellation considering constellation stability and comprehensive cost

HE Bei, CAI Changsheng, PAN Lin, CAI Chenglin

2022, 47(5): 9-15. doi: 10.12265/j.gnss.2022092

[Abstract](404) [FullText HTML] (79) [PDF 5063KB](63)

Abstract:
The first step is to design a low earth orbit satellite (LEO) for navigation augmentation using low earth orbit satellites. When designing the constellation configuration, the stability and comprehensive cost of the constellation are two important factors to be considered. This paper presents an optimal design method for low earth orbit navigation constellation considering constellation stability and comprehensive cost. First, the Iridium constellation is optimized by genetic algorithm. Compared with Iridium constellation, the mean number of visible satellites increases from 2.3 to 2.9, the standard deviation of visible satellites decreases from 2.3 to 0.7, and the comprehensive cost factor decreases from 5.3 to 4.5, which proves the effectiveness of this method. Then, taking Walker constellation as the basic configuration, the low earth orbit hybrid constellation is optimized by genetic algorithm, considering the navigation performance and comprehensive cost on the basis of ensuring the stability of the hybrid constellation. The optimized low earth orbit hybrid constellation is combined with the BDS constellation. Compared with the BDS, the mean number of visible satellites increases from 6.9 to 9.3, and the standard deviation of visible satellites decreases from 1.1 to 0.4.

Equivalence analysis of two-domain combined adjustment solutions of pseudo-range single point positioning

HU Xiaohua, LIU Changjian, ZHANG Xi

2022, 47(5): 16-21. doi: 10.12265/j.gnss.2022083

[Abstract](308) [FullText HTML] (68) [PDF 1962KB](17)

Abstract:
The combined adjustment solutions of the linear observation model in the observation domain and in the adjustment range are completely equivalent. However, in practice, the observation models of the combined adjustment are mostly nonlinear, which always need to be linearized in parameter estimation, resulting in linearized model error. The influence of this error on the equivalence of the two-domain adjustment solutions remains to be discussed. Thus, taking pseudo-range single point positioning (SPP) as an example, the solution formulas of the combined adjustment in the adjustment range of the observation model are deduced in this paper, on which the reason why the two-domain combined adjustment cannot be completely equivalent under the SPP model is presented and a numerical analysis is carried out with the example data. Research shows, the two-domain adjustment solution of SPP cannot be equivalent because it is assumed that the initial value of each iteration solution of a single system is the same as that of the combined adjustment of the observation range. And under the same configuration, the two-domain adjustment position solutions of different Global Navigation Satellites System (GNSS) combined SPP are the same value on the order of millimeter, that is, for the application of SPP, the two-domain adjustment solutions can be considered the same. The content of this paper also has certain reference significance for some other GNSS applications.

BDS-3 dynamic data characteristics for new signals of B1C/B2a and PPP accuracy analysis

LIU Yongzheng, CAI Changsheng, CUI Xianqiang, ZHU Yongxing

2022, 47(5): 22-27. doi: 10.12265/j.gnss.2022064

[Abstract](461) [FullText HTML] (100) [PDF 2752KB](71)

Abstract:
The vehicle dynamic data characteristics for BDS-3 new signals of B1C/B2a are analyzed using four indices, i.e. carrier noise ratio (CNR), data integrity rate, observation noise and multipath. The kinematic precise point positioning (PPP) performance for BDS-3 new signals is also tested and compared with the other GNSS. The test results show that the average CNR of BDS-3 B2a new frequency is better than those of the other BDS frequencies, but slightly worse than that of GPS L5. The data integrity rate of BDS is relatively higher compared with the other GNSS. Further, the data integrity rate of the BDS-3 B2a new frequency is the highest. The noise of BDS-3 pseudorange observation at B2b frequency is the lowest, and the pseudorange observation noise at B1C and B2a frequencies is about three times of that of the B2b signal. However, the noise of phase observations at different frequencies is in the same level. For pseudorange multipath, the BDS-3 B1C/B2a signal is slightly smaller than the B2b signal, and overall, the GPS L5 signal has the strongest ability to suppress the multipath. In terms of kinematic PPP performance, the BDS-3 B1C/B2a dual-frequency combined kinematic PPP achieves the best positioning accuracy with a three-dimensional root mean square error of 0.439 m. Compared with the BDS B1I/B3I, GPS L1/L2, GLONASS G1/G2, and Galileo E1/E5a dual-frequency combined PPP, the accuracy improvement rates are 49%、56%、81% and 42% respectively.

GNSS/UWB based indoor and outdoor continuous positioning method

ZHOU Zhennan, ZOU Jingui, ZHAO Yinzhi, HU Hong, CAI Lixian, ZHOU Tao

2022, 47(5): 28-34. doi: 10.12265/j.gnss.2022087

[Abstract](474) [FullText HTML] (109) [PDF 4031KB](54)

Abstract:
To address the problems that Global Navigation Satellite System (GNSS) and ultra-wideband (UWB) positioning systems have limited range in complex indoor and outdoor environments, and that no single source can obtain continuous and reliable positioning results from outdoor to indoor. In this paper, we investigate the BeiDou Navigation Satellite System (BDS)+GPS/UWB loose combination positioning method, design dynamic indoor and outdoor positioning experiments and static positioning experiments in the transition area, use the extended Kalman filter to optimally estimate the positioning error state, and analyze and evaluate three positioning modes: BDS+GPS combination, UWB and loose combination. The experimental results show that the combination of BDS+GPS/UWB improves the positioning accuracy and extends the range of GNSS-real-time kinematic (GNSS-RTK) in the indoor-outdoor transition area, and the combination of BDS+GPS/UWB improves the continuity and usability of the system from outdoor to indoor positioning compared with each single source.

BDS-2/BDS-3/GPS/Galileo dual frequency precision single point positioning accuracy analysis and evaluation

LU Fukang, YU Xuexiang, XIAO Xingxing, HU Fujie

2022, 47(5): 35-44. doi: 10.12265/j.gnss.2022059

[Abstract](325) [FullText HTML] (183) [PDF 3057KB](35)

Abstract:
Since the BeiDou Navigation Satellite System (BDS) has been formally networked, it is necessary to evaluate and analyze the positioning performance of the BDS. This article mainly through 5 days observation data from 8 stations in MGEX (Multi-GNSS Experiment), give priority to with BeiDou-2/ BeiDou-3 (BDS-2/BDS-3) to analysis BDS-2/BDS-3, BDS-2/BDS-3/Galileo, BDS-2/BDS-3/GPS, BDS-2/BDS-3/GPS/Galileo four different combination of satellite system static precise point positioning (PPP) performance, the experimental results show that the positioning accuracy and convergence speed of BDS-2/BDS-3 static PPP in east (E), north (N) and up (U) directions are better than 2.49 cm, 2.27 cm, 4.04 cm and 34.6 min, 19.3 min and 28.1 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GALIEO static PPP in E, N and U directions are better than 1.81 cm, 1.65 cm, 2.94 cm and 20.4 min, 13.0 min, 18.6 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GPS static PPP in E, N and U directions are better than 1.67 cm, 1.62 cm, 2.82 cm and 18.3 min, 10.2 min, 16.1 min, respectively. The positioning accuracy and convergence speed of BDS-2/BDS-3/GPS/Galileo static PPP in E, N and U directions are better than 1.46 cm, 1.40 cm, 2.45 cm and 14.5 min, 9.3 min, 14.5 min, respectively.

Error analysis and parameter optimization of ionospheric autocorrelation prediction method

XIONG Wen, WANG Bowen, LIU Yiwen, ZHU Qinglin

2022, 47(5): 45-50. doi: 10.12265/j.gnss.2022097

[Abstract](227) [FullText HTML] (130) [PDF 2467KB](27)

Abstract:
Ionospheric delay is an important error source in GNSS high-precision navigation and positioning applications. Through the measurement and short-term prediction of total ionospheric electron content (TEC), the positioning accuracy of GNSS single frequency users can be effectively improved, and the ionospheric effect of other radio systems can also be effectively alleviated. In the past two decades, many effective short-term prediction methods have been proposed, but none of them is absolutely leading, and the prediction accuracy of all these methods needs to be improved. In this paper, using the TEC observation data of five grid points arbitrarily selected from the Madrigal database, the autocorrelation and autoregressive moving average (ARIMA) methods are compared, and then the influence of two parameters on the prediction error in the autocorrelation prediction method is studied. Finally, an optimized parameter setting scheme is put forward for the autocorrelation prediction method. The experimental results show that: 1) The prediction error of the autocorrelation method is slightly smaller than that of the ARIMA method, and the time taken by the autocorrelation method is obviously less than that of the ARIMA method. Therefore, the comprehensive performance of the autocorrelation method is better than ARIMA method; 2) For the autocorrelation method, compared with the traditional “4+12”scheme, “3+9” scheme has better prediction performance on the whole, indicating that the ionosphere current state may be mainly related to the state of the previous three days. The relevant results can be used as a useful reference scheme for the implementation of ionospheric short-term prediction engineering.“3+9” scheme has better prediction performance on the whole, indicating that the ionosphere current state may be mainly related to the state of the previous three days. The relevant results can be used as a useful reference scheme for the implementation of ionospheric short-term prediction engineering.

Indoor dynamic SLAM based on geometric constraints and target detection

GAO Yi, WANG Qing, YANG Gaochao, LIU Pengfei

2022, 47(5): 51-56. doi: 10.12265/j.gnss.2022099

[Abstract](258) [FullText HTML] (65) [PDF 3401KB](20)

Abstract:
Aiming at the problem of low localization accuracy and poor map effect of visual simultaneous localization and mapping (SLAM) in indoor dynamic environment, a indoor dynamic SLAM method is proposed based on geometric constraints and target detection. The target detection network is used to obtain semantic information and a method for missing detection of moving objects is proposed. Based on prior knowledge, an information determination method is proposed to accurately identify dynamic regions. Dynamic points are eliminated based on geometric constraints and deep learning. Static points are used to estimate camera pose. A closed-loop static map is builded based on the stored information. The experiment on TUM dataset shows that the localization accuracy is 97.5% higher than that of ORB-SLAM2 and the performance is better than other dynamic SLAM. The experiment in the indoor real environment shows that the static map is more accurate. The localization accuracy and the map effect of indoor dynamic SLAM are improved effectively.

Performance analysis of BDS/GNSS airborne kinematic PPP

ZHAO Long, GUO Jiang, LI Guangcai, LUO Feng

2022, 47(5): 57-64. doi: 10.12265/j.gnss.2022096

[Abstract](505) [FullText HTML] (91) [PDF 3481KB](61)

Abstract:
Based on the measured data in the airborne kinematic scene, this paper uses the open-source PRIDE PPP-AR software to construct a dual-frequency ionosphere-free combination (IF) using the pseudorange and carrier phase observations for kinematic precise point positioning (PPP) experiment, and it also compares the performance of a single BDS system and BDS/GNSS in airborne large kinematic positioning. The results show that the number of satellites, satellite geometry and position dilution of precision (PDOP) of the multi-system combination are superior. In a single system, the positioning accuracy in the plane (east (E), north (N) and up (U) )directions are improved by 10% and 12% respectively. In addition, this paper compares the solution results of the open-source software PRIDE PPP-AR with the commercial software WayPoint, the results show that the positioning accuracy of the former is improved by 46% and 36% in the E and U directions respectively, and the N direction is the most improved, nearly doubled. Therefore, PRIDE PPP-AR has higher solution accuracy and better solution performance.

Analysis of colored noise and environmental loading in northeast region of CMONOC coordinate time series

HUANG Yu, SUI Zhemin, JIN Zelin

2022, 47(5): 65-71, 80. doi: 10.12265/j.gnss.2021112202

[Abstract](245) [FullText HTML] (73) [PDF 3347KB](26)

Abstract:
The Hector software is used to calculate the time series observation data of 16 continuous stations of Crustal Movement Observation Network of China (CMONOC) in Northeast China in the past 10 years, obtain the time series data of the coordinate residuals of the continuous stations, and then determine the optimal noise model, and finally get the results based on colored noise and environmental load the corrected velocity field. The results show that white noise (WN), flicker noise (FN) and power-law noise (PL) are mainly present in CMONOC coordinate time series data in Northeast China; the optimal noise model in the north (N) and up (U) directions is WN+FN; the optimal noise model in the east (E) direction is WN+PL. Taking into account the influence of colored noise and environmental load, the average velocity of movement in the N direction of the northeast region’s CMONOC based on the ITRF14 framework is −13.003 mm/a, the average velocity of movement in the E direction is 27.020 mm/a, and the average speed of upward movement in the U direction is 0.528 mm/a, and the overall uplift trend.

Realization and application testing of real-time kinematic on smartphone

ZENG Shulin, KUANG Cuilin

2022, 47(5): 72-80. doi: 10.12265/j.gnss.2022054

[Abstract](557) [FullText HTML] (243) [PDF 5839KB](72)

Abstract:
With the development of chip technology, the smartphone has become the most widely used Global Navigation Satellite System (GNSS) device, and its ability to provide location services is gradually being demonstrated. To investigate the feasibility of using a smartphone as a professional GNSS device and to take advantage of the opportunity of opening GNSS raw measurements on an Android smart terminal, an real-time kinematic (RTK) positioning APP was designed and implemented, and a high-precision positioning application test was performed based on it. The results show that the APP's real-time positioning accuracy can achieve about 1 dm under static conditions, and can reach sub-meter levels in plane and 1 to 2 m in vertical under dynamic situations of pedestrians and automobiles. The RTK positioning accuracy is significantly higher than that of the built-in chip solution, but the stability is slightly worse. The results also show that when using a smartphone to imitate RTK point measurement, the plane accuracy can reach about 1 m, which is sufficient for sub-meter to meter-level low-precision professional applications such as geographic information collecting and survey.

Design of maritime transport monitoring system based on BDS

CAO Yu, LIU Xin, ZHAO Yongqi, SONG Yuze, TANG Xiaobo, ZHANG Xinyu

2022, 47(5): 81-87. doi: 10.12265/j.gnss.2022067

[Abstract](275) [FullText HTML] (75) [PDF 5204KB](17)

Abstract:
Maritime transport is often affected by high temperature, high salt and high humidity environment, especially for valuable and precision cargoes, which are prone to damage risk during transportation. Therefore, it is important to establish a cargo communication monitoring system for improving the quality of marine transportation. In this paper, a maritime transport monitoring system based on BeiDou Navigation Satellite System (BDS) was designed, which combined the internet of things technology and BDS to achieve the real-time monitoring, navigation, positioning and communication functions of cargo. Taking the transportation of multiphase flow meter as an example, the realization method of the system function was described in detail. The system can be used as an industrialized assistant tool to reduce the cost of cargo damage and improve the efficiency of transportation management.

Study of virtual balise information fusion method based on attenuation factor

CHEN Yonggang, HAN Sicheng, JIA Shuilan, XU Jiye

2022, 47(5): 88-93. doi: 10.12265/j.gnss.2022075

[Abstract](202) [FullText HTML] (69) [PDF 2519KB](11)

Abstract:
To address the problem that the Kalman filter was prone to filter divergence when using the virtual balise (VB) information fusion, an information fusion method based on the improved Sage-Husa adaptive filtering algorithm was proposed: firstly, the adaptive filtering was used to dynamically adjust the noise statistical characteristics parameters to suppress filter divergence, secondly, an attenuation factor was introduced into the prediction error variance matrix to reduce the influence of stale data and thus improve the filtering accuracy, and finally, simulation experiment was conducted to compare the proposed algorithm with the Kalman filter and Sage-Husa adaptive filter in terms of position and velocity error of the VB. The simulation outcome reveals that the algorithm has an obvious advantage in the positioning error of the VB with better stability in the same time.

The technology of quarantine based on GNSS location information in cellphone

LIU Shaolin, MA Baotian, JIN Ruimin, ZHEN Weimin

2022, 47(5): 94-99. doi: 10.12265/j.gnss.2022026

[Abstract](213) [FullText HTML] (49) [PDF 2858KB](20)

Abstract:
During the outbreak of COVID-19, early quarantine from high risk areas is an effective measure to curb the spread of the epidemic. To avoid people leaving the quarantine area without authorization, a large number of supervisors are required to conduct 24 hours supervision, which not only needs much of labor and money, but also have the problems of information leakage, non real-time information collection and the safety of supervisors. It is necessary to realize automatic real-time quarantine monitoring by using the existing infrastructure. This paper realized it by collecting and analyzing the position and carrier noise ratio (CNR) information of Global Navigation Satellite System (GNSS) chip receiver in cellphone. Through analysis of the actual detection data, the result shows that the method can accurately and effectively distinguish whether the people leave of the quarantine area.

Performance evaluation of atmospheric precipitable water vapor inversion of mutil-system GNSS at selected MGEX stations

ZHENG Zhiqing, ZHANG Kefei, LI Longjiang, SHI Jiaqi, ZHANG Minghao

2022, 47(5): 100-110. doi: 10.12265/j.gnss.2022119

[Abstract](438) [FullText HTML] (81) [PDF 11642KB](53)

Abstract:
In June 2020, the BeiDou Navigation Satellite System (BDS) completed its global coverage deployment. In order to analyze the accuracy of BDS derived water vapor information, the observed data of 15 MGEX stations in October and November 2021 were used to invert carry out water vapor. The well-known comprehensive GNSS data processing software package GAMIT was used to calculate the observation data of BDS, GPS, Galileo and GLONASS respectively, and the tropospheric zenith total delay (ZTD) was compared with the results provided by IGS, and the PWV was compared with the PWV derived from radiosonde and ERA5 data. Results show that when cutoff angle is set to 5°, the root mean square (RMS) of the ZTD estimated by four satellite systems are all less than 13 mm. Compared with RS-PWV, GPS-PWV, BDS-PWV, Galileo-PWV and GLONASS-PWV, the mean RMSs are 2.25 mm, 2.46 mm, 2.52 mm and 2.84 mm, respectively, all RMSs are less than 3 mm. Compared with ERA5-PWV, the mean RMSs are 1.63 mm, 1.86 mm, 1.76 mm and 1.99 mm, respectively, all RMSs are less than 2 mm. GPS has the highest water vapor determination accuracy, while BDS’s accuracy of water vapor detection is lower than that of GPS and Galileo, but higher than GLONASS, which can meet the requirements of meteorological applications.

Analysis of temporal and spatial variation characteristics of rainstorm based on BeiDou PWV

GUO Qiuying, ZHAO Yao, HUANG Shoukai, ZHANG Haiping, LI Guowei, SUN Yingjun

2022, 47(5): 111-117. doi: 10.12265/j.gnss.2022123

[Abstract](329) [FullText HTML] (70) [PDF 4877KB](29)

Abstract:
Using the BeiDou observation data of 49 continuously operating reference stations in Shandong Province (SDCORS) in 2020, the atmospheric water vapor inversion was carried out using GAMIT software, and the annual hourly precipitable water vapor (PWV) series were obtained. Comparing the PWV obtained by inversion with the PWV observed by radiosonde weather station, the average deviation is 2.4 mm, the root mean square error is 3.4 mm, and the correlation coefficient reaches 0.98, indicating that the accuracy of inversion results meets the needs of meteorological research. The changes of PWV in the rainstorm process were analyzed from a single CORS station and the whole province. It was found that PWV began to rise 5 hours to 12 hours before the rainstorm. At the time of the rainstorm, the maximum value of PWV generally reached more than 60 mm, and the average change rate reached 1 to 3 mm/h. The closer the rainstorm occurred, the greater the change range of PWV. After the precipitation ended, PWV will decline rapidly. The change of PWV is highly correlated with the occurrence of rainstorm, which can be used for rainstorm warning research.

The design and simulation of a small active Loran-C receiving antenna

LIU Yang, QI Jundong, CHEN Qidong, HUANG Xiao, XU Wenpu, LIU Rui

2022, 47(5): 118-126. doi: 10.12265/j.gnss.2022147

[Abstract](454) [FullText HTML] (161) [PDF 4728KB](80)

Abstract:
Aiming at the needs of Loran-C to receive radio navigation signals, a high-performance Loran-C small active receiving antenna is studied, which can greatly facilitate the use of Loran-C navigation receivers. It is of high practical significance to reduce the volume of the antenna to reduce the difficulty of installation. The main body of the antenna adopts a magnetic rod coil antenna to receive the Loran-C signal in the long-wave band. The front-end signal conditioning circuit including amplifier circuit, band-pass filter circuit, differential output circuit and power supply circuit is designed to increase signal sensitivity and signal-to-noise ratio; an integrated antenna structure is designed for engineering application. Simulations show that the antenna can efficiently receive Loran-C signals. It can amplify the weak Loran-C signal and filter out out-of-band noise, and the signal strength and signal-to-noise ratio meet the requirements. The antenna has the characteristics of small size, high sensitivity and convenient use, and can be used in Loran-C radio navigation, combined Navigation, additional secondary phase delay calculation and other scenarios.