Commercial Global Navigation Satellite Systems Research Articles

Enhancing USVs navigation based on minimum error entropy of GPS vector tracking

In recent years, unmanned surface Vessels (USVs) have increasingly been used for river monitoring and hydrological surveys. USVs rely on global navigation satellite systems (GNSS) for navigation. However, signal blocking can cause the traditional GNSS vector tracking (VT) loop to increase the code phase and carrier frequency errors, leading to higher positioning errors that do not meet USVs’ requirements. To address this problem, we propose a VT method based on the minimum error entropy (MEE) in the signal tracking module. The MEE Kalman filter is adopted as the loop filter to mitigate code phase and carrier frequency errors, reduce non-Gaussian noise and random errors generated by signal blocking, and enhance the positioning accuracy and robustness of USV navigation. The measurement noise covariance of the loop filter was adjusted adaptively using the signal carrier-to-noise ratio. A field experiment was conducted using a commercial GNSS receiver as reference. The results demonstrate a 19.3% improvement in positioning accuracy compared with the traditional method in an open environment. Moreover, the proposed method maintains stable operation and achieves a 79.4% improvement in positioning accuracy during signal blocking. This novel algorithm offers a new concept for USV navigation systems to cope with signal blocking.

On the Importance of Precise Positioning in Robotised Agriculture

The precision of agro-technical operations is one of the main hallmarks of a modern approach to agriculture. However, ensuring the precise application of plant protection products or the performance of mechanical field operations entails significant costs for sophisticated positioning systems. This paper explores the integration of precision positioning based on the global navigation satellite system (GNSS) in agriculture, particularly in fieldwork operations, seeking solutions of moderate cost with sufficient precision. This study examines the impact of GNSSs on automation and robotisation in agriculture, with a focus on intelligent agricultural guidance. It also discusses commercial devices that enable the automatic guidance of self-propelled machinery and the benefits that they provide. This paper investigates GNSS-based precision localisation devices under real field conditions. A comparison of commercial and low-cost GNSS solutions, along with the integration of satellite navigation with advanced visual odometry for improved positioning accuracy, is presented. The research demonstrates that affordable solutions based on the common differential GNSS infrastructure can be applied for accurate localisation under real field conditions. It also underscores the potential of GNSS-based automation and robotisation in transforming agriculture into a more efficient and sustainable industry.

Comparative Assessment of Spire and COSMIC-2 Radio Occultation Data Quality

In this study, we investigate the performances of a commercial Global Navigation Satellite System (GNSS) Radio Occultation (RO) mission and a new-generation RO constellation, i.e., Spire and Constellation Observing System for Meteorology, Ionosphere, and Climate 2 (COSMIC-2), respectively. In the statistical comparison between Spire and COSMIC-2, the results indicate that although the average signal-to-noise ratio (SNR) of Spire is far weaker than that of COSMIC-2, the penetration of Spire is comparable to, and occasionally even better than, that of COSMIC-2. In our analysis, we find that the penetration depth is contingent upon various factors including SNR, GNSS, RO modes, topography, and latitude. With the reanalysis of the European Centre for Medium-Range Weather Forecasts and Radiosonde as the reference data, the identical error characteristics of Spire and COSMIC-2 reveal that overall, the accuracy of Spire’s neutral-atmosphere data products was found to be comparable to that of COSMIC-2.

Using the Commercial GNSS RO Spire Data in the Neutral Atmosphere for Climate and Weather Prediction Studies

Recently, the NOAA has included GNSS (Global Navigation Satellite System) Radio Occultation (RO) data as one of the crucial long-term observables for weather and climate applications. To include more GNSS RO data in its numerical weather prediction systems, the NOAA Commercial Weather Data Pilot program (CWDP) started to explore the commercial RO data available on the market. After two rounds of pilot studies, the CWDP decided to award the first Indefinite Delivery Indefinite Quantity (IDIQ) contract to GeoOptics and Spire Incs. in 2020. This study examines the quality of Spire RO data products for weather and climate applications. Spire RO data collected from commercial CubeSats are carefully compared with data from Formosa Satellite Mission 7–Constellation Observing System for Meteorology, Ionosphere, and Climate-2 (COSMIC-2), the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis (ERA5), and high-quality radiosonde data. The results demonstrate that, despite their generally lower Signal-Noise-Ratio (SNR), Spire RO data show a pattern of lowest penetration height similar to that of COSMIC-2. The Spire and COSMIC-2 penetration heights are between 0.6 and 0.8 km altitude over tropical oceans. Although using different GNSS RO receivers, the precision of Spire STRATOS receivers is of the same quality as those of the COSMIC-2 TriG (Global Positioning System—GPS, GALILEO, and GLObal NAvigation Satellite System—GLONASS) RO Receiver System (TGRS) receivers. Furthermore, the Spire and COSMIC-2 retrieval accuracies are quite comparable. We validate the Spire temperature and water vapor profiles by comparing them with collocated radiosonde observation (RAOB) data. Generally, over the height region between 8 km and 16.5 km, the Spire temperature profiles match those from RS41 RAOB very well, with temperature biases of <0.02 K. Over the height range from 17.8 to 26.4 km, the temperature differences are ~−0.034 K, with RS41 RAOB being warmer. We also estimate the error covariance matrix for Spire, COSMIC-2, and KOMPSAT-5. The results show that the COSMIC-2 estimated error covariance values are slightly more significant than those from Spire over the oceans at the mid-latitudes (45°N–30°N and 30°S–45°S), which may be owing to COSMIC-2 SNR being relatively lower at those latitudinal zones.

Efficient collocation of global navigation satellite system radio occultation soundings with passive nadir microwave soundings

Abstract. Radio occultation (RO) using the global navigation satellite system (GNSS) can be used to infer atmospheric profiles of microwave refractivity in the Earth's atmosphere. GNSS RO data are now assimilated into numerical weather prediction models and used for climate monitoring. New remote sensing applications are being considered that fuse GNSS RO soundings and passive nadir-scanned radiance soundings. Collocating RO soundings and nadir-scanned radiance soundings, however, is computationally expensive, especially as new commercial GNSS RO constellations greatly increase the number of global daily RO soundings. This paper develops a new and efficient technique, called the “rotation–collocation method”, for collocating RO and nadir-scanned radiance soundings in which all soundings are rotated into the time-dependent reference frame in which the nadir sounder's scan pattern is stationary. Collocations with RO soundings are then found when the track of an RO sounding crosses the line corresponding to the nadir sounder's scan pattern. When applied to finding collocations between RO soundings from COSMIC-2, Metop-B-GRAS, and Metop-C-GRAS and the passive microwave (MW) soundings of the Advanced Technology Microwave Sounder (ATMS) on NOAA-20 and Suomi-NPP and the Advanced Microwave Sounding Unit (AMSU-A) on Metop-B and Metop-C for the month of January 2021, the rotation–collocation method proves to be 99.0 % accurate and is hundreds to thousands of times faster than traditional approaches to finding collocations.

A GNSS Spoofing Detection and Direction-Finding Method Based on Low-Cost Commercial Board Components

The Global Navigation Satellite System (GNSS) is vulnerable to deliberate spoofing signal attacks. Once the user wrongly locks on the spoofing signal, the wrong position, velocity, and time (PVT) information will be calculated, which will harm the user. GNSS spoofing signals are difficult to carry out spoofing attacks in the direction of arrival (DOA) of the real signal, so the spoofing detection method based on DOA is very effective. On the basis of identifying spoofing signals, accurate DOA information of the signal can be further used to locate the spoofer. At present, the existing DOA monitoring methods for spoofing signals are mainly based on dedicated antenna arrays and receivers, which are costly and difficult to upgrade and are not conducive to large-scale deployment, upgrade, and maintenance. This paper proposes a spoofing detection and direction-finding method based on a low-cost commercial GNSS board component (including an antenna). Based on the traditional principle of using a multi-antenna carrier phase to solve DOA, this paper innovatively solves the following problems: the poor direction-finding accuracy caused by the unstable phase center of low-cost commercial antennas, the low success rate of spoofing detection in a multipath environment, and the inconsistent sampling time among multiple low-cost commercial GNSS boards. Moreover, the corresponding prototype equipment for spoofing detection and direction-finding is developed. The measured results show that it can effectively detect spoofing signals in open environments. Under a certain false alarm rate, the detection success rate can reach 100%, and the typical direction-finding accuracy can reach 5°.

Precise Position Estimation Using Smartphone Raw GNSS Data Based on Two-Step Optimization.

This paper presents a high-precision positioning method using raw global navigation satellite system (GNSS) observations from smartphones in the Google smartphone decimeter challenge (GSDC). Compared to commercial GNSS receivers, smartphone GNSS observations are noisy owing to antenna limitations, making it difficult to apply conventional high-precision positioning methods. In addition, it is important to exclude outliers in GSDC because GSDC includes data in environments where GNSS is shielded, such as tunnels and elevated structures. Therefore, this study proposes a smartphone positioning method based on a two-step optimization method, using factor graph optimization (FGO). Here, the velocity and position optimization process are separated and the velocity is first estimated from Doppler observations. Then, the outliers of the velocity estimated by FGO are excluded, while the missing velocity is interpolated. In the next position-optimization step, the velocity estimated in the previous step is adopted as a loose state-to-state constraint and the position is estimated using the time-differenced carrier phase (TDCP), which is more accurate than Doppler, but less available. The final horizontal positioning accuracy was 1.229 m, which was the first place, thus demonstrating the effectiveness of the proposed method.

Trigger time acquisition system for ground based air shower experiments

For observations of cosmic gamma rays of several TeV or more, many experimental groups conduct ground-based air shower observation experiments. New projects such as Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) are also underway. In these experiments, an accurate trigger time measurement system is required when sudden cosmic phenomena are observed. To record such sudden astronomical phenomena, we have developed an event-trigger time recording system that accurately measures the arrival times of air showers. The system consists of a commercial global navigation satellite system module, a high-precision clock, a multi-hit type time-to-digital converter with a reset function for accurate time measurement, and a network-time-protocol server installed on a computer. It was confirmed that the time accuracy compared to UTC was approximately 1μs, and the time deviation was approximately 11.4 ns with one standard deviation. The developed system is versatile and can also be used for the ALPACA experiment. It is expected that the time accuracy of this system can be improved to approximately ±40 ns.

Sensor-based detection of parturition in beef cattle grazing in an extensive landscape: a case study using a commercial GNSS collar

Context Neonate management remains a key issue in extensive beef production systems where producers are faced with substantial environmental and management challenges that limit their ability to monitor and manage livestock in a timely manner. Parturition is a critical event and can affect the calf health and survival, particularly in the perinatal period (up to 48 h after birth). As such, monitoring parturition using precision livestock technologies may provide producers with additional tools to manage their cattle and mitigate the impacts of neonatal mortality in extensive beef systems. Aims The purpose of this study was to determine whether data from a global navigation satellite system (GNSS) collar could be used to detect parturition events in extensively grazed beef cattle. Methods Forty-eight Bos taurus cows (583.5 kg body weight ± 9.25 s.e.m.) were allocated to a 28 ha paddock between 8 January 2021 and 6 March 2021 during the calving season. Thirty of the animals were fitted with GNSS-equipped collars (Smart Paddock, Vic., Australia) that captured data at 10 min intervals. Parturition events were recorded daily by visual observation. Collected data were used to calculate key predictive features related to calving behaviour. Derived features were compared and assessed for changes in the period surrounding parturition. Key results Increases were observed in distance to nearest neighbour and to herd aggregate features, and decreases were observed in paddock utilisation and distance travelled features in the lead-up to calving (P < 0.05). Furthermore, the number of animals within a 20 m radius decreased significantly (P < 0.05) in the lead up to parturition, supporting known isolation behaviours. Conclusions With further development of predictive algorithms, on-animal sensors may be valuable in the prediction of calving events in extensive beef production systems. Implications Remote management and monitoring with on-animal sensor technologies, such as GNSS collars and tags, will provide producers with an additional means of monitoring their animals, while overcoming many of the management challenges associated with extensive grazing operations.

On Use of Low Cost, Compact GNSS Receiver Modules for Ionosphere Monitoring

AbstractGeodetic or special purpose Global Navigation Satellite System (GNSS) receivers are used for ionosphere monitoring and research. Dual frequency, compact, low‐cost commercial GNSS modules can provide raw GNSS data and are commonly used for positioning applications. This paper presents the applicability of these compact modules for monitoring ionospheric activities. A comparative study between Javad Triumph LS, a costly geodetic receiver, and an Ublox ZED‐F9P, a low‐cost, dual‐frequency, compact module is carried out to explore the potential of the low‐cost devices for ionosphere probing. Studies are carried out on signal strength values (C/N0) and vertical total electron content (VTEC) values. From the concurrently collected GPS data, a bias of 2.2–4.9 dBHz in signal strength values are observed between the two types of receivers depending on the signal frequency band. The VTEC values calculated from the Ublox module are in close agreement with the values obtained from the Triumph LS receiver. Therefore, the compact module shows the potential for use in ionosphere monitoring with clear advantages in cost, size, and power consumption. However, the signal strength values obtained from such compact modules need to be calibrated using standard GNSS receivers. A GNSS‐based Ionosphere Monitoring Unit (GIMU) is also proposed in this manuscript by the integration of a compact, low‐cost GNSS module with a single‐board computer and a wireless data communication module. Real‐time, cost‐effective, concurrent ionosphere monitoring over a geographically distributed network is possible using a network of such units.

A Comparative Study for Performance Analysis of Kinematic Multi-Constellation GNSS PPP in Dynamic Environment

This case study aims to investigate the effect of different Multi-GNSS EXperiment (MGEX) precise products provided by International GNSS Service (IGS) Analysis Centers (ACs) on post-processing kinematic Precise Point Positioning (PPP) accuracy performance with different satellite system combinations in a dynamic environment. Within this frame, a test was carried out in a lake and kinematic data were collected over 6 h at 1 Hz rate from the available Global Navigation Satellite System (GNSS) constellations with the geodetic-grade receiver fixed on a marine vehicle for bathymetric mapping. PPP-derived coordinates were determined by a commercial GNSS post-processing software with different processing approaches as GPS (Global Positioning System)-only, GPS+GLObal’naya NAvigatsionnaya Sputnikovaya Sistema (GLONASS), GPS+GLONASS+European Global Navigation Satellite System (Galileo), GPS+GLONASS+Chinese Global Navigation Satellite System (BeiDou), and GPS+GLONASS+Galileo+BeiDou. The PPP coordinates were then compared to the reference coordinates obtained from the post-processed carrier phase-based differential kinematic solutions. In general, the results showed that the kinematic multi-constellation GNSS PPP technique could provide positioning accuracy from cm to decimeter level as depending on the collected data constellations and used precise products in the processing. Among all solutions, the GPS+GLONASS+Galileo+BeiDou combination with German Research Centre for Geosciences (GFZ)’s precise products presented the best multi-GNSS PPP performance, rather than the other combinations and quad-constellation alternatives using different precise products. In this study, the test procedure and the obtained results are given in detail.

Experimental Evaluation of the Impact of Different Types of Jamming Signals on Commercial GNSS Receivers

The received global navigation satellite system (GNSS) signal has a very low power due to traveling a very long distance and to the nature of the signal’s propagation medium. Thus, GNSS signals are easily susceptible to signal interference. Signal interference can cause severe degradation or interruption in GNSS position, navigation, and timing (PNT) services which could be very critical, especially in safety-critical applications. The objective of this paper is to evaluate the impact of the presence of jamming signals on a high-end GNSS receiver and investigate the benefits of using a multi-constellation system under such circumstances. Several jamming signals are considered in this research, including narrowband and wideband signals that are located on GPS L1 or GLONASS L1 frequency bands. Quasi-real dynamic trajectories are generated using the Spirent™ GSS6700 GNSS signal simulator combined with an interference signal generator through a Spirent™ GSS8366 unit. The performance evaluation was carried out using several evaluation metrics, including signal power degradation, navigation solution availability, dilution of precision (DOP), and positioning accuracy. The multi-constellation system presented better performance over the global positioning system (GPS)-only constellation in most cases. Moreover, jamming the GPS band caused more critical effects than jamming the GLONASS band.

A smart city used low-latency seamless positioning system based on inverse global navigation satellite system technology

People have to move between indoor and outdoor frequently in city scenarios. The global navigation satellite system signal cannot provide reliable indoor positioning services. To solve the problem, this article proposes a seamless positioning system based on an inverse global navigation satellite system signal, which can extend the global navigation satellite system service into the indoor scenario. In this method, a signal source is arranged at a key position in the room, and the inverse global navigation satellite system signal is transmitted to the global navigation satellite system receiver to obtain a preset positioning result. The indoor positioning service is continued with the inertial navigation system after leaving the key position. The inverse global navigation satellite system seamless positioning system proposed in this article can unify indoor and outdoor positioning using the same receiver. The receiver does not need to re-receive navigation information when the scene changes, which avoids the switching process. Through the design of signal layer coverage, the receiver is in a warm start state, and the users can quickly fix the position when the scenario changes, realizing quick access in a true sense. This enables the ordinary commercial global navigation satellite system receiver to obtain indoor positioning capability without modification, and the algorithm can perform accurate positioning indoors and outdoors without switching.

Tracking Performance in Endurance Racing Sports: Evaluation of the Accuracy Offered by Three Commercial GNSS Receivers Aimed at the Sports Market.

Advances in global navigation satellite system (GNSS) technology have resulted in smaller and more accurate GNSS receivers, which have become increasingly suitable for calculating instantaneous performance parameters during sports competitions, for example by providing the difference in time between athletes at any location along a course. This study investigated the accuracy of three commercially available GNSS receivers directed at the sports market and evaluated their applicability for time analysis in endurance racing sports. The receivers evaluated were a 1 Hz wrist-worn standalone receiver (Garmin Forerunner 920XT, Gar-920XT), a 10 Hz standalone receiver (Catapult Optimeye S5, Cat-S5), and a 10 Hz differential receiver (ZXY-Go). They were validated against a geodetic, multi-frequency receiver providing differential position solutions (accuracy < 5 cm). Six volunteers skied four laps on a 3.05 km track prepared for cross-country skiing, with all four GNSS receivers measuring simultaneously. Deviations in position (horizontal plane, vertical, direction of travel) and speed (horizontal plane and direction of travel) were calculated. In addition, the positions of all receivers were mapped onto a mapping trajectory along the ski track, and a time analysis of all 276 possible pairs of laps was performed. Specifically, the time difference between any two skiers for each integer meter along the track was calculated. ZXY-Go, CAT-S5, and GAR-920XT had horizontal plane position errors of 2.09, 1.04, and 5.29 m (third quartile, Q3), and vertical precision 2.71, 3.89, and 13.35 m (interquartile range, IQR), respectively. The precision in the horizontal plane speed was 0.038, 0.072, and 0.66 m s-1 (IQR) and the time analysis precision was 0.30, 0.13, and 0.68 s (IQR) for ZXY-Go, Cat-S5, and Gar-920XT, respectively. However, the error was inversely related to skiing speed, implying that for the low speeds typically attained during uphill skiing, substantially larger errors can occur. Specifically, at 2.0 m s-1 the Q3 was 0.96, 0.36, and 1.90 s for ZXY-Go, Cat-S5, and Gar-920XT, respectively. In summary, the differential (ZXY-Go) and 10 Hz standalone (Cat-S5) receivers performed substantially better than the wrist-worn receiver (Gar-920XT) in terms of horizontal position and horizontal speed calculations. However, all receivers produced sub-second accuracy in the time analysis, except at very low skiing speeds.

Software-defined radio technology for GNSS scintillation analysis: bring Antarctica to the lab

Global navigation satellite systems (GNSSs) are widely used to support logistics, scientific operations, and to monitor the polar ionosphere indirectly, which is a region characterized by strong phase scintillation events that severely affect the quality and reliability of received signals. Professional commercial GNSS receivers are widely used for scintillation monitoring; on the contrary, custom-designed solutions based on data grabbers and software receivers constitute novelty. The latter enables a higher level of flexibility and configurability, which is important when working in remote and severe environments. We describe the scientific, technological, and logistical challenges of installing an ionospheric monitoring station in Antarctica, based on a multi-constellation and multi-frequency GNSS data grabber and a software-defined radio receiver. Having access to the full receiver chain and to intermediate signal processing stages allows a deep analysis of the impact of scintillation and, in turn, a better understanding of the physical phenomenon. The possibility to process high-resolution raw intermediate frequency samples of the signal enables not only the computation of scintillation indexes with the same quality as professional devices but also the design and test of innovative receiver architectures and algorithms. Furthermore, the record and replay approach offers the possibility to process in the lab the signals captured on site, with high fidelity level. It is like being in Antarctica again, but with an unlimited set of receivers and higher computational, storage, and bandwidth resources. The main advantages and disadvantages of this approach are analyzed. Examples of monitoring results are reported, confirming the monitoring capabilities, showing the good agreement with commercial receiver outputs and confirming the validity of post-processing and re-play operations.

Towards lane-level traffic monitoring in urban environment using precise probe vehicle data derived from three-dimensional map aided differential GNSS

Today's urban road transport systems experience increasing congestion that threatens the environment and transport efficiency. Global Navigation Satellite System (GNSS)-based vehicle probe technology has been proposed as an effective means for monitoring the traffic situation and can be used for future city development. More specifically, lane-level traffic analysis is expected to provide an effective solution for traffic control. However, GNSS positioning technologies suffer from multipath and Non-Line-Of-Sight (NLOS) propagations in urban environments. The multipath and NLOS propagations severely degrade the accuracy of probe vehicle data. Recently, a three-dimensional (3D) city map became available on the market. We propose to use the 3D building map and differential correction information to simulate the reflecting path of satellite signal transmission and improve the results of the commercial GNSS single-frequency receiver, technically named 3D map-aided Differential GNSS (3D-DGNSS). In this paper, the innovative 3D-DGNSS is employed for the acquisition of precise probe vehicle data. In addition, this paper also utilizes accelerometer-based lane change detection to improve the positioning accuracy of probe vehicle data. By benefitting from the proposed method, the lane-level position, vehicle speed, and stop state of vehicles were estimated. Finally, a series of experiments and evaluations were conducted on probe data collected in one of the most challenging urban cities, Tokyo. The experimental results show that the proposed method has a correct lane localization rate of 87% and achieves sub-meter accuracy with respect to the position and speed error means. The accurate positioning data provided by the 3D-DGNSS result in a correct detection rate of the stop state of vehicles of 92%.

Orbital Filter Aiding of a High Sensitivity GPS Receiver for Lunar Missions

Recent studies have shown that weak Global Navigation Satellite System (GNSS) signals could potentially be used to navigate from the Earth to the Moon. This would increase autonomy, robustness and flexibility of the navigation architectures for future lunar missions. However, the utilization of GNSS signals at very high altitudes close to the Moon can be significantly limited by the very low power levels seen at the receiver’s antenna. This can result in a strongly reduced visibility of the GNSS satellites, which can worsen the already poor relative geometry of the GNSS receiver to the GNSS satellites. Furthermore, during most of a Moon Transfer Orbit (MTO), the very weak GNSS signals are also affected by Doppler shifts and Doppler rates larger than the ones generally experienced on the Earth, due to the much higher relative dynamics between the receiver and the transmitters. As a consequence, commercial GNSS receivers for terrestrial use cannot successfully acquire and track such signals. More advanced architectures and specific implementations are thus required to use GNSS for lunar missions. In this paper we propose the use of an adaptive orbital filter to aid the GNSS acquisition and tracking modules and to strongly increase the achievable navigation accuracy. The paper describes the orbital filter architecture and tests results carried out by processing realistic radio frequency (RF) signals generated by our Spirent GSS 8000 full constellation simulator for a highly elliptical MTO.

Urban Pedestrian Navigation Using Smartphone-Based Dead Reckoning and 3-D Map-Aided GNSS

This paper focuses on the pedestrian navigation in highly urbanized area, where a current smartphone and a commercial global navigation satellite system (GNSS) receiver perform poorly because of the reflection and blockage of GNSS signal by buildings and foliage. A 3-D map-aided pedestrian positioning method is previously developed to mitigate and correct the multipath GNSS signal. However, it still suffers from the low availability due to the insufficient number of satellites. We develop a smartphone-based pedestrian dead reckoning (PDR) algorithm, which is carried in the pedestrian’s trousers. This PDR is capable of not only providing continues solutions but also indicating the pedestrian motions. A closed-loop Kalman filter with adaptive tuning is proposed to integrate the 3-D map-aided GNSS method with the smartphone-based PDR system. According to the experiment results, the proposed integration system can achieve $\sim 1.5$ - and 5.5-m of positioning errors in a middle-class and deep urban canyon, respectively.

The Design of a Small GNSS Receiver with Enhanced Interference Suppression Capability for High Mobility

The applications of Global Navigation Satellite System (GNSS) receivers are becoming wider in various commercial and military systems including even small weapon systems such as artillery shells. The precision-guided munitions such as Small Diameter Bomb (SDB) of United States can be used for pinpoint strike by acquiring and tracking GNSS signals in high mobility situation. In this paper, a small GNSS receiver with embedded interference suppression capability working under high dynamic stress is developed which is applicable to the various weapon systems and can be used in other several harsh environments. It applies a kind of matched filter and multiple correlator schemes for fast signal acquisition and tracking of even weak signals and frequency domain signal processing method to eliminate the narrowband interference. To evaluate the performance of the developed GNSS receiver, the test scenario of high mobility and interference environment with the GNSS simulator and signal generator is devised. Then, the signal acquisition time, navigation accuracy, sensitivity, and interference suppression performances under high dynamic operation are evaluated. And the comparison test with the commercial GNSS receiver which has high sensitivity is made under the same test condition.

An ultra-wide bandwidth-based range/GPS tight integration approach for relative positioning in vehicular ad hoc networks

Relative position awareness is a vital premise for the implementation of emerging intelligent transportation systems, such as collision warning. However, commercial global navigation satellite systems (GNSS) receivers do not satisfy the requirements of these applications. Fortunately, cooperative positioning (CP) techniques, through sharing the GNSS measurements between vehicles, can improve the performance of relative positioning in a vehicular ad hoc network (VANET). In this paper, while assuming there are no obstacles between vehicles, a new enhanced tightly coupled CP technique is presented by adding ultra-wide bandwidth (UWB)-based inter-vehicular range measurements. In the proposed CP method, each vehicle fuses the GPS measurements and the inter-vehicular range measurements. Based on analytical and experimental results, in the full GPS coverage environment, the new tight integration CP method outperforms the INS-aided tight CP method, tight CP method, and DGPS by 11%, 15%, and 24%, respectively; in the GPS outage scenario, the performance improvement achieves 60%, 65%, and 73%, respectively.