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2023 Vol. 48, No. 4

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Special Column on “Comprehensive PNT New Technology”
Theory and Discussion
Technical Report and Application

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2023, 48(4)

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2023, 48(4): 2-2.

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Special Column on “Comprehensive PNT New Technology”

2023, 48(4): 1-1.

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Integrated PNT application service system: conceptual framework, technical route and application prospects

YU Baoguo, DENG Zhixin, ZHANG Jingkui, HUANG Lu, JIA Haonan

2023, 48(4): 3-11. doi: 10.12265/j.gnss.2023089

[Abstract](913) [FullText HTML] (135) [PDF 2869KB](142)

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The integrated positioning, navigation and timing (PNT) service system is an important support for the operation and development of China’s digital economy and society. The comprehensive PNT application service with BDS-3 as the core is the development focus of China’s future spatiotemporal information technology and industry. Firstly, the concept of “on-demand elastic and scalable integrated PNT application service system” was defined, and an application service framework of “integrated white box (software defined node)+unified network (elastic and scalable system)+network signaling field diagram (intelligent operation and management services)+intelligent game (complex task decision-making)” was proposed. A comprehensive PNT application service technology route of “fixed base, strong network, and efficiency enhancement” was designed, The comprehensive PNT application service mode of “public network+private network+mobile network” was given, and the application prospect was prospected. In the future, a comprehensive spatiotemporal application service system with the core of “BeiDou+LEO+5G+pseudosatellite+location big data” will provide BeiDou indoor and outdoor ubiquitous spatial cloud and terminal collaborative precise location services for multi-level and multi-disciplinary users, and assist in the digital transformation of the entire society.

Research and application progress of BeiDou+5G fusion positioning technology

JIN Yao, ZHOU Youmei, ZHANG He, ZHANG Zining, ZHANG Chenfang, ZHAO Liang, WEI Buzheng

2023, 48(4): 12-18. doi: 10.12265/j.gnss.2023091

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BeiDou Navigation Satellite System (BDS) provides high-precision positioning services globally, but faces challenges in urban canyons and indoor environments. However, with the widespread commercial adoption of 5G and advancements in sub-meter level positioning accuracy, integrating BeiDou with 5G can enable ubiquitous and seamless indoor and outdoor integrated positioning solutions, which holds significant implications for China’s implementation of its positioning, navigation and timing (PNT) strategy. This article summarizes the key principles and characteristics of wireless positioning technology, traces the evolution of mobile communication network positioning technology, and highlights the latest 5G positioning methods. It further categorizes BeiDou+5G fusion positioning into two levels: enhanced positioning and fusion positioning. Fusion positioning is further divided into weighted fusion positioning and signal fusion positioning based on the degree of coupling in the positioning process. Additionally, strategies for BeiDou+5G fusion positioning in different scenarios are presented. Finally, the article discusses the current development status and potential applications of BeiDou+5G fusion positioning, aiming to provide a valuable reference for further research and practical implementation of BeiDou+5G fusion positioning.

Analyzing the current situation of quantum navigation technology system

MAO Yue, SUN Zhongmiao, JIA Xiaolin, SONG Xiaoyong, JIANG Qingxian

2023, 48(4): 19-23. doi: 10.12265/j.gnss.2023034

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With the continuous development of quantum information science and technology, quantum navigation equipment has attracted extensive attention at home and abroad due to its higher measurement accuracy, smaller equipm ent volume and wider application areas. It has gradually become an emerging technology to improve the core capability of the next generation of position and navigation equipment and may be put into use before 2030, and become an core realm to lead the following development of position and navigation. This paper combs the technical system, key development directions and research status in the field of quantum navigation, and gives follow-up development suggestions, which plays a promoting role in the development of quantum navigation technology.

Overview of characteristics and development of shadowed space positioning and navigation technology

BAO Yachuan, YANG Menghuan, LI Jianjia, LI Jun

2023, 48(4): 24-29, 43. doi: 10.12265/j.gnss.2023074

[Abstract](378) [FullText HTML] (97) [PDF 3149KB](75)

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The long and narrow closed physical structures and complex channel characteristics of sheltered spaces, such as underground pipe corridors and building interiors, pose a significant challenge to high-precision positioning and navigation. This article combs and analyzes the adaptability of typical scenarios and technical means in sheltered space, and quantifies the challenges faced by high-precision navigation and positioning in sheltered space. The future development of sheltered space positioning systems is prospected, and a high-precision positioning and navigation system architecture suitable for complex environments in sheltered space is designed. The network diagram is integrated. A hybrid positioning network is built based on multimode systems such as ultra wide band (UWB), BeiDou pseudo-satellite, and near-ultrasonic positioning to achieve full scene coverage in sheltered space. Compared with currently commonly used radio positioning systems, it has achieved significant improvements in positioning accuracy, coverage performance, and other aspects.

Research on ultra wideband signal’s high sensitivity receive technology

XU Guanghui, YU Baoguo, ZHAO Jun, BAO Yachuan, YANG Menghuan, YU Xuegang

2023, 48(4): 30-36. doi: 10.12265/j.gnss.2023036

[Abstract](276) [FullText HTML] (90) [PDF 3702KB](50)

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The power spectral density of UWB signal stipulated by the Federal Communications Commission (FCC) is not greater than –41.3 dBm/MHz, which limits the transmitting power of ultra wide band (UWB) signal. In order to improve the receiving sensitivity of UWB signal receiver under the condition of limited power and the ranging distance of UWB signal. A long-coherent integration algorithm is designed to improve the signal processing gain, and the simulation of the long-coherent integration algorithm is carried out on two UWB signal systems according to the IEEE 802.15.4 protocol, namely HRP UWB and LRP UWB. The simulation results show that, improving the integration length has an obvious effect on HRP UWB signal, while the gain to LRP UWB signal is limited. The simulation results provide a reference and design direction for the design of UWB signal structure, which will play an important role for the application of communication and navigation integration.

Laser odometry algorithm based on point cloud segmentation

LI Yifan, DU Shitong, LI Shuang, HUANG Lu, YANG Zihan, CHEN Chong

2023, 48(4): 37-43. doi: 10.12265/j.gnss.2023066

[Abstract](189) [FullText HTML] (62) [PDF 3753KB](19)

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In this paper, we propose a feature extraction and matching method based on point cloud segmentation to address the problems of information redundancy and interference of discrete points in laser odometry algorithms. By utilizing the horizontal rotation scanning characteristics of mechanical LiDAR, the point cloud data is segmented and clustered by scan lines, and edge points are extracted as line features and surface points are extracted as surface features. Compared to traditional feature extraction methods, our algorithm can effectively extract feature points with less distinctiveness and eliminate discrete points. The algorithm not only reduces the computational complexity but also improves the accuracy and robustness of positioning, which has great application prospects in robot navigation tasks. The performance of the algorithm is validated through computer simulation and achieved good experimental results.

Research on UAVs cloud-end collaborative navigation control algorithm

XIONG Huajie, YU Baoguo, YI Qingwu, HE Chenglong

2023, 48(4): 44-48, 56. doi: 10.12265/j.gnss.2023050

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Conduct research on unmanned aerial vehicles (UAVs) navigation planning algorithms and strategies, based on the analysis of traditional path planning methods and classical particle swarm optimization (PSO), a UAVs cloud collaborative navigation control algorithm is proposed. The PSO in the UAV onboard part is improved, and the hybrid swarm intelligent algorithm in the cloud background part is designed and optimized. Simulation and actual test results show that the method is correct and feasible, and can improve the quality of UAVs navigation planning solution. Compared with other navigation planning methods, this method has obvious advantages in UAVs navigation.

Research on joint TOA estimation algorithm based on baseband mode S signal

DIWU Yaoguang, GONG Fengxun

2023, 48(4): 49-56. doi: 10.12265/j.gnss.2023072

[Abstract](205) [FullText HTML] (86) [PDF 3125KB](24)

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Aiming at the problem of inaccurate time of arrival (TOA) extraction caused by low signal-to-noise ratio (SNR) of received signals in wide area multilateration system, a joint TOA estimation algorithm combining matched filter and non-coherent integration is proposed, which can effectively reduce the root mean square error (RMSE) of the matched filter TOA estimation method under low SNR. The joint algorithm does the non-coherent integration of the matched filter output of the received reply signals within the dwell time of the secondary surveillance radar, marks a time stamp at the maximum point for TOA estimation, and uses the principle of energy accumulation to improve the SNR, so as to improve the estimation accuracy. The simulation results show that the algorithm can achieve a TOA estimation accuracy of 24.302 ns at −15 dB SNR, 53 MHz sampling frequency and 9 accumulated signals. The proposed joint TOA estimation algorithm has the characteristics of high accuracy and high robustness, and can improve the estimation accuracy to less than 25 ns at the SNR of −15 dB to 0 dB. It provides an effective method for extracting the TOA of mode S signals with low SNR and improving the positioning accuracy of wide area multilateration.

RTK/B2b-PPP fusion switching positioning technology based on BDS-3/GPS

HUANG Hong, GAO Wang, MIAO Weiwei, TENG Ling, DONG Fangyun, PAN Shuguo

2023, 48(4): 57-62. doi: 10.12265/j.gnss.2023065

[Abstract](352) [FullText HTML] (112) [PDF 2389KB](61)

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In order to solve the problem that network real-time kinematic (RTK) communication signals are easy to be interrupted in the remote sea and desert, a switching technology of RTK/B2b-PPP fusion based on BeiDou-3 Navigation Satellite System (BDS-3)/GPS is proposed, which makes full use of the characteristics of fast convergence and high positioning accuracy of network RTK and wide coverage,single station positioning of B2b-PPP. The high-precision position coordinates obtained by network RTK are used as priori information and integrated with B2b-PPP to assist B2b-PPP converge fast. The results show that the positioning accuracy of RTK fixed solution and B2b-PPP fusion is 2.57 cm, 0.90 cm and 2.83 cm in the east (E), north (N) and up (U) directions, respectively, which is much higher than that of independent B2b-PPP positioning. In addition, after the fusion of RTK fixed solution and B2b-PPP for 1 s, it can help the instantaneous convergence of B2b-PPP. After the interruption of RTK, the initial accuracy reaches the level of cm, and gradually transitions to the independent positioning accuracy level of B2b-PPP after 0.5 h, indicating that B2b-PPP can be used as an effective means to supplement the network RTK. Can effectively maintain high precision positioning level.

Space observation data preliminary analysis of XPNAV-1 satellite

ZHOU Qingyong, ZHANG Jiankang, JIA Xiaolin, YAN Linli, FAN Shaojuan

2023, 48(4): 63-68. doi: 10.12265/j.gnss.2023063

[Abstract](257) [FullText HTML] (92) [PDF 2865KB](27)

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The X-ray pulsar-based navigation-1 (XPNAV-1) is China’s first space experimental platform dedicated to exploring X-ray pulsar navigation technology. It has been in orbit for over seven years, accumulating a large amount of observational data. This work collects nearly four years of space observation data from the satellite and conducts valuable technical research explorations. Firstly, the satellite’s observation data on the Crab pulsar is processed and analyzed. The pulse profiles of the Crab pulsar per orbit, per day, and the total pulse profile are obtained. The results indicate that the pulse profile is stable in the temporal dimension, showing good consistency with domestic and international observational results. Different energy range pulse profiles of the Crab pulsar are obtained, and the characteristics of pulse profile variation with energy are analyzed. In the energy dimension, the energy spectra of the Crab pulsar in different pulse phase intervals are obtained. It is found that the energy spectrum is proportional to the pulse intensity in the phase interval, indicating that the domestically developed focusing X-ray detector is in good technical condition and has achieved the experimental goal of accurately “seeing” the pulsar from the satellite. Finally, using three days of observation data from the XPNAV-1 satellite, pulsar navigation test solutions based on the least squares algorithm are achieved. The satellite’s orbit determination accuracy is approximately 56.93 km. Analysis reveals that the current navigation solution accuracy is severely affected by observation errors of XPNAV-1 towards the Crab pulsar and initial orbit errors.

Generalized damped LAMBDA method and the application in long baseline real-time positioning

CAO Shilong, YU Baoguo, WU Cailun, JIA Haonan

2023, 48(4): 69-74. doi: 10.12265/j.gnss.2023043

[Abstract](203) [FullText HTML] (74) [PDF 2392KB](29)

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In long baseline real-time positioning, strong correlation between adjacent observations resulting in ill-conditioned normal equation which is adverse to fast integer solution of carrier phase ambiguity. In this contribution, a generalized damped least-squares ambiguity decorrelation adjustment (LAMBDA) method was be proposed based on traditional LAMBDA method and the solution expression for carrier phase ambiguity in single epoch also be derived. This method uses the prior information of coordinates and carrier phase ambiguity to improve the ill-condition of the normal equation and the solution accuracy of floating ambiguity, which is helpful for the fast integer ambiguity solution. Two long baselines (266 km and 456 km) measured data were used to verify. Compared with the traditional method, the ambiguity fixed rate of the improved method was increased by 28.8%. When the amplification factor c=0, the generalized damped LAMBDA method was equivalent to the traditional damped LAMBDA method. Four long baseline real-time data streams from the Australian continuous operation reference system (CORS) network were selected for testing. The experimental results show that multi-system real-time positioning accuracy was better than 2 cm in the horizontal direction and 4 cm in the elevation direction with a baseline length of less than 1 000 km. The generalized damped LAMBDA method has certain application reference value for long baseline real-time positioning.

Research on signal phase measurement technology of very low frequency communication station for navigation and positioning

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

2023, 48(4): 75-80. doi: 10.12265/j.gnss.2023143

[Abstract](223) [FullText HTML] (93) [PDF 2415KB](35)

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In order to provide backup navigation and positioning means when the GNSS cannot locate, it is an important direction to carry out research on non cooperative navigation and positioning related technologies based on very low frequency communication station signals. This paper proposes and verifies a phase measurement technology for very low frequency communication station signals, realizes phase measurement for very low frequency communication station signals, and uses two different measurement points, verified the accuracy of phase measurement. This method uses the characteristics of minimum shift keying (MSK) signal itself to calculate the relative phase of the receiving point, keep two test point at a certain distance, calculate the phase of the two receiving points, compare the distance difference calculated by the phase difference of the two test point with the distance difference between the two test point and the transmitting point, and verify the accuracy of this algorithm. By verifying that the method proposed in this article can accurately measure the phase difference between two receiving and transmitting points. This phase difference can reflect the distance difference, and navigation and positioning can be achieved by calculating the distance difference between multiple stations.

Path planning of unmanned vehicles in narrow and long space based on improved RRT algorithm

ZHANG Junhao, PAN Shuguo, GAO Wang, GUO Peng, WANG Ping, HU Peng

2023, 48(4): 81-90. doi: 10.12265/j.gnss.2023090

[Abstract](257) [FullText HTML] (93) [PDF 3535KB](30)

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A path planning algorithm based on improved rapidly-exploring random trees (RRT) is proposed for the path planning system of unmanned vehicles in narrow and long space, which solves the problems of large randomness and lack of safety of the traditional RRT algorithm. The algorithm improves the traditional RRT algorithm by adding adaptive target probability sampling strategy and dynamic step size strategy. At the same time, considering the dynamics constraints of driverless vehicles in the actual situation, the algorithm adds vehicle collision constraints and path angle constraints, and proposes a random turning strategy within the restricted area to solve the problem that the angle constraints will lead to the multiplication of iterations, and a path with higher safety is finally obtained. The performance of the proposed algorithm is compared with existing algorithms by computer simulation. Compared with the traditional RRT algorithm guided by artificial potential field in narrow and long space, the iteration times, planning time and path length of the proposed algorithm are reduced by 33.09%, 6.44% and 0.06%, and the planning ability of the proposed algorithm is improved in both simple environment and dense obstacle environment. The proposed algorithm has higher planning efficiency and fewer iteration .

Theory and Discussion

Countermeasure of UAV GPS spoofing jamming attcck

CHEN Lijun, PAN Zhengjun, CHEN Xiaoru

2023, 48(4): 91-98. doi: 10.12265/j.gnss.2023026

[Abstract](550) [FullText HTML] (724) [PDF 2558KB](97)

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In recent times, autonomous and semi-autonomous unmanned aerial vehicles (UAVs) fleets have begun to generate a lot of research interest and demand from a variety of civilian applications. However, in order to successfully perform a variety of missions, fleets of UAVs require GPS signals, which unfortunately are unencrypted and uncertified. This facilitates the implementation of GPS spoofing attacks, in which an adversary mimics a real GPS signal and broadcasts it to a target drone in order to change its course and force it to land or crash. In this study, a GPS Spoofing detection mechanism is proposed to detect both single and multi-transmitter GPS spoofing attacks to prevent them from changing course or crashing. GPS Spoofing detection mechanism is based on comparing the distance calculated from their GPS coordinates between every two hive members and the distance obtained from pulsed radio UWB ranging between the same hive members. If the difference in distance is greater than a selected threshold, a GPS spoofing attack is declared detected. Finally, the case proves that GPS Spoofing detection mechanism is superior to the existing detection technology. It can detect GPS spoofs without modifying the original antenna or installing additional hardware. Moreover, it does not need complex calculation and communication overhead, thus reducing false positives and making the detection mechanism more reliable.

Performance analysis of undifferenced PPP ambiguity resolution with LEO enhanced GPS, Galileo, BDS-3

FANG Jing, TU Rui, WANG Peiyuan, TAO Linlin, ZUO Hang

2023, 48(4): 99-107. doi: 10.12265/j.gnss.2023044

[Abstract](223) [FullText HTML] (126) [PDF 2719KB](53)

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This paper focused on the stability of uncalibrated phase delays (UPD) of GPS, Galileo, BDS-3, and the low earth orbit (LEO) augmented undifferenced precise point positioning (PPP) ambiguity resolution. Based on the observation data of 126 global distributed MGEX stations of 7 days from 001 to 007 in 2022 were employed for UPDs estimation of GPS, Galileo, BDS-3. Wide-lane UPDs were estimated as a set of constants every day and narrow-lane UPDs were estimated as a set of constants every 15 minutes. The results showed that the wide-lane UPSs had good stability within one week, and the average standard deviation was less than 0.05 cycles. The narrow-lane UPDs had good stability within 1 day, and the average standard deviation was less than 0.06 cycles. Using the estimated UPDs products for PPP AR and analyzing their performance, the average convergence time of GPS, Galileo and BDS-3 was shortened from 20.75 min, 23.78 min, 30.60 min to 10.69 min, 18.27 min, 24.80 min, respectively, and the average ambiguity fix rates were 90.41%, 77.22% and 67.21%, respectively. The average value of root-mean square error (RMSE) in the east, north and up components decreased from (1.59 cm, 0.91 cm, 3.30 cm), (1.58 cm, 0.93 cm, 3.24 cm), (1.61 cm, 0.98 cm, 3.39 cm) to (0.90 cm, 0.89 cm, 2.98 cm), (1.33 cm, 0.85 cm, 2.90 cm) and (1.47 cm, 1.18 cm, 2.94 cm), respectively. Using the simulated LEO constellation observation data, the enhancement effect of different number of LEO satellites was studied, and the enhancement effect became more significant when the number of LEO visible satellites is more. When the number of LEO visible satellites was 10, the average convergence time of GPS, Galileo and BDS-3 were improved from 10.69 min, 18.27 min, 24.80 min to 1.53 min, 1.71 min, 1.94 min, and average ambiguity fixing rates were improved from 90.41%, 77.22%, 67.51% to 93.43%, 79.99%, 72.00%, respectively.

Technical Report and Application

Research on GNSS non-stationary interference technology for countering interference antennas

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

2023, 48(4): 108-114. doi: 10.12265/j.gnss.2023152

[Abstract](289) [FullText HTML] (86) [PDF 3648KB](43)

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A signal system design based on non-stationary interference signals is proposed for GNSS anti-interference antenna arrays to improve the interference effect on GNSS signals. Simulate non-stationary interference signals from different systems by constructing interference scenarios targeting GNSS anti-interference antenna arrays. For anti-interference antennas using space frequency anti-interference algorithms, the interference effect of GNSS signals is improved by more than 10 dB compared to traditional broadband spread spectrum interference by using non-stationary interference signals. The designed interference system, with its non-stationary characteristics, breaks the premise of designing antenna array anti-interference algorithms (the interference signal is generally stable), and has a significant impact on the performance of such anti-interference algorithms.