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Low Earth Orbit (LEO) is of great benefit for the positioning performance of Global Navigation Satellite System (GNSS). To realize the system of LEO-augmented GNSS, three methods to integrate communication and navigation signal for LEO communication system with the least influence on the communication performance are analyzed. The analysis adopts t...
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Resilient navigation in Global Navigation Satellite System (GNSS)-degraded and -denied environments is becoming more and more required for many applications. It can typically be based on multi-sensor data fusion that relies on alternative technologies to GNSS. In this work, we studied the potential of a low earth orbit (LEO) satellite communication...
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... In this regard, most of the current simulations have focused on fragmented topics of the fullchain LEO-PNT solution [9]. They have focused on how to define new orbit models embedded to the broadcast messages [13], [14], [15], orbit determination [16], [17], [18], signal structure designs [19], [20], [21], atmospheric models [22], [23], [24], constellation optimization strategies to improve the GNSS convergence time [6], [25], satellite clocks [26], [27], user performance estimation [28], [29], [30], [31], [32], [33], [34], and integration with distinct sensors [35]. To expand the simulations, there is still a gap in the process of implementing an end-to-end LEO-PNT system, binding all segments in a unified model. ...
Low Earth orbit (LEO) satellites provide the potential to overcome the current limitations in global navigation satellite systems (GNSS) due to the increased satellite velocity and signal reception power. As the whole LEO segment grows, preliminary studies and simulations have been conducted in the most recent years to identify how to develop a LEO-PNT system and add value to GNSS. To promote the development of LEO-PNT, this work presents the simulation of several key components of a dedicated LEO-PNT system. Our investigation analyzes features of the satellite constellation, orbits, on-board instruments, signal propagation effects, user measurements, and map the accuracy of the service on the ground. The analysis considers the signal propagation from both LEO and medium Earth orbit (MEO) satellites and provides the expected accuracy of a ground user when certain system parameters and instruments are defined in the space mission design. All parameters and statistical distributions, which can serve to future LEO-PNT simulations and developments, are presented. For validation and demonstration, a comparison is presented to analyze the expected positioning errors for LEO satellites, and how they differ from the classic GNSS. Our investigation enables a valuable quantitative analysis of the dedicated LEO-PNT systems and provides analysis for LEO-PNT systems design optimization.
... It is worth highlighting the work carried out by Wang et al. [26]. They simulated several methods to integrate the navigation messages in the communication signals of the LEO satellites. ...
As the whole space segment of satellites in low Earth orbits (LEO) grows, simulations of positioning, navigation, and timing (PNT) through LEO satellites are needed to understand the possible gains that the upcoming satellite missions can offer to global navigation satellite systems (GNSS). The simulations do not only help to forecast the optimal GNSS future advancements, but also guide us on how to implement the most optimized PNT missions. In the most recent years, several simulation tools have focused on broadcast orbit models, precise orbit determination of LEO satellites, signal structure designs, atmospheric models, constellation optimization strategies, satellite clock implementations, and positioning integration with distinct sensors. In this work, we overview most of the latest developments found in the literature to define the status and challenges of LEO- PNT system simulations.
... Perov et al. sought to utilize the principle of phase interferometer, using multiple receiving antennas [11]. Wang et al. sought to integrate communications navigation with global positioning system sensors [12]. Christian proposed autonomous augmentation using optical navigation by relativistic perturbation of starlight [13]. ...
Classical and optimal control architectures for motion mechanics in the presence of noisy sensors use different algorithms and calculations to perform and control any number of physical demands, to varying degrees of accuracy and precision in regards to the system meeting the desired end state. To circumvent the deleterious effects of noisy sensors, a variety of control architectures are suggested, and their performances are tested for the purpose of comparison through the means of a Monte Carlo simulation that simulates how different parameters might vary under noise, representing real-world imperfect sensors. We find that improvements in one figure of merit often come at a cost in the performance in the others, especially depending on the presence of noise in the system sensors. If sensor noise is negligible, open-loop optimal control performs the best. However, in the overpowering presence of sensor noise, using a control law inversion patching filter performs as the best replacement, but has significant computational strain. The control law inversion filter produces state mean accuracy matching mathematically optimal results while reducing deviation by 36%. Meanwhile, rate sensor issues were more strongly ameliorated with 500% improved mean and 30% improved deviation. Inverting the patching filter is innovative but consequently understudied and lacks well-known equations to use for tuning gains. Therefore, such a patching filter has the additional drawback of having to be tuned through trial and error.
... In recent years, the integration and development of LEO navigation augmentation systems and satellite communication constellations have greatly promoted the integration of communication and navigation (Deng et al. 2021;Qu et al. 2017;Reid et al. 2018;Wang et al. 2018aWang et al. , 2019b. The integration of communication and navigation is important for continuously improving Positioning, Navigation, and Timing (PNT) services and is a popular research topic around the world (Benzerrouk et al. 2019;Leyva-Mayorga et al. 2020). ...
Driven by improvements in satellite internet and Low Earth Orbit (LEO) navigation augmentation, the integration of communication and navigation has become increasingly common, and further improving navigation capabilities based on communication constellations has become a significant challenge. In the context of the existing Orthogonal Frequency Division Multiplexing (OFDM) communication systems, this paper proposes a new ranging signal design method based on an LEO satellite communication constellation. The LEO Satellite Communication Constellation Block-type Pilot (LSCC-BPR) signal is superimposed on the communication signal in a block-type form and occupies some of the subcarriers of the OFDM signal for transmission, thus ensuring the continuity of the ranging pilot signal in the time and frequency domains. Joint estimation in the time and frequency domains is performed to obtain the relevant distance value, and the ranging accuracy and communication resource utilization rate are determined. To characterize the ranging performance, the Root Mean Square Error (RMSE) is selected as an evaluation criterion. Simulations show that when the number of pilots is 2048 and the Signal-to-Noise Ratio (SNR) is 0 dB, the ranging accuracy can reach 0.8 m, and the pilot occupies only 50% of the communication subcarriers, thus improving the utilization of communication resources and meeting the public demand for communication and location services.
... Wang, et al. sought to integrate communications navigation with global positioning system sensors. [11] Christian proposed autonomous augmentation using optical navigation by relativistic perturbation of starlight [12]. Fan, et al. investigated a plume noise suppression algorithm based on star point shape and the angular distance between stars [13]. ...
Classical and optimal control architectures for motion mechanics with fusion of noisy sensors use different algorithms and calculations to perform and control any number of physical demands, to varying degrees of accuracy, precision, and cost. Their performances are tested for the purpose of comparison through the means of a Monte Carlo simulation that simulates how different parameters might vary under noise, representing real-world imperfect sensors. We find that improvements in one figure of merit often come at a cost in the performance in the others, especially depending on the presence of noise in the system sensors. If sensor noise is negligible, open-loop optimal control performs the best. However, in the overpowering presence of sensor noise, using a control law inversion patching filter performs as the best replacement, but has significant computational strain.
... Recent years have witnessed the great development of lowearth-orbit (LEO) satellite systems. Due to the low orbital altitude, low signal path attenuation and high signal landing power, LEO satellite systems can provide a navigation enhancement, which can well improve the performance of the existing Global Navigation Satellite Systems (GNSSs) (Ajibesin et al. 2009;Wang et al. 2019). Specifically, on the one hand, LEO satellite systems can be an extension of GNSS. ...
It is an important development direction to take advantage of low-earth-orbit (LEO) satellites by establishing a LEO satellite navigation system as a supplement to Global Navigation Satellite Systems in the future. On account of the fast motion of LEO satellites, there is a significant and fast change in the Doppler frequency of LEO navigation signals. Since a LEO navigation system usually consists of a large number of satellites, the search range of carrier frequencies and satellite numbers is correspondingly large in the signal acquisition process. Adopting the traditional code division multiple access (CDMA) technique will bring extremely high computational complexity to the acquisition process of LEO navigation signals, which leads to a much longer acquisition time. Considering the characteristics of LEO navigation signals, we proposed a Doppler Frequency-Code Phase Division Multiple Access (DFCP-DMA) technique in order to achieve a fast acquisition of LEO navigation signals. Because the motion of LEO satellites is fast, Doppler frequencies and code phases of LEO navigation signals arriving at the receiver differ significantly. Thus, receivers can distinguish LEO navigation signals by multiple combinations of different Doppler frequencies and code phases acquired. To decrease the acquisition complexity, all LEO satellites broadcast spread-spectrum navigation signals modulated by the same spreading code in DFCP-DMA, and receivers can acquire all navigation signals using only this spreading code. Theoretical analysis and simulation results show that, compared with CDMA, DFCP-DMA can significantly reduce the acquisition complexity without any loss in the acquisition sensitivity, which can shorten the acquisition time to 1/M, where M is the number of satellites. There is a high application prospect for DFCP-DMA in future LEO navigation systems.
... Three types of measurements can be used for positioning purposes: Doppler, pseudorange, and carrier phase. If the carrier phase is used, the signal must be continuous [48]. For this reason, multiple access methodologies such as time division multiple access (TDMA) are not applicable for satellite positioning because transmissions are split into different time slots and the transmissions are not continuous. ...
More and more satellites are populating the sky nowadays in the Low Earth orbits (LEO). Most of the targeted applications are related to broadband and narrowband communications, Earth observation, synthetic aperture radar, and internet-of-Things (IoT) connectivity. In addition to these targeted applications, there is yet-to-be-harnessed potential for LEO and positioning, navigation, and timing (PNT) systems, or what is nowadays referred to as LEO-PNT. No commercial LEO-PNT solutions currently exist and there is no unified research on LEO-PNT concepts. Our survey aims to fill the gaps in knowledge regarding what a LEO-PNT system entails, its technical design steps and challenges, what physical
layer parameters are viable solutions, what tools can be used for a LEO-PNT design (e.g., optimisation steps, hardware and software simulators, etc.), the existing models of wireless channels for satellite-toground
and ground-to-satellite propagation, and the commercial prospects of a future LEO-PNT system. A comprehensive and multidisciplinary survey is provided by a team of authors with complementary expertise in wireless communications, signal processing, navigation and tracking, physics, machine learning, Earth observation, remote sensing, digital economy, and business models.
... In recent years, along with the continuous development of the high-resolution Earth observations, remote sensing, communication and navigation based on low Earth orbit (LEO) satellites, real-time, precise and reliable orbits of LEO platforms are crucial for many space applications, such as altimetry, gravimetry, synthetic aperture radar (SAR) interferometry, atmospheric sounding or navigation signal augmentation [1][2][3]. Precise onboard real-time orbit determination (RTOD) using the space-borne data of a global navigation satellite system (GNSS) is recognized as the mainstream navigation technology for LEO satellites, due to its global coverage, abundant observations and low cost. The onboard RTOD, as the name implies, is the process of real-time orbit determination completed in the embedded system onboard satellites. ...
The advancements of Earth observations, remote sensing, communications and navigation augmentation based on low Earth orbit (LEO) platforms present strong requirements for accurate, real-time and autonomous navigation of LEO satellites. Precise onboard real-time orbit determination (RTOD) using the space-borne data of multiple global navigation satellite systems (multi-GNSS) becomes practicable along with the availability of multi-GNSS. We study the onboard RTOD algorithm and experiments by using America’s Global Positioning System (GPS) and China’s regional BeiDou Navigation Satellite System (BDS-2) space-borne data of the FengYun-3C satellite. A new pseudo-ambiguity parameter, which combines the constant phase ambiguity, the orbit and clock offset error of the GPS/BDS broadcast ephemeris in the line-of-sight (LOS), is defined and estimated in order to reduce the negative effect of the LOS error on onboard RTOD. The analyses on the variation of the LOS error in the GPS/BDS broadcast ephemeris indicate that the pseudo-ambiguity parameter could be modeled as a random walk, and the setting of the power spectral density in the random walk model decides whether the pseudo-ambiguity can be estimated reasonably and the LOS error could be reduced or not. For different types of GPS/BDS satellites, the LOS errors show different variation characteristics, so the power spectral density should be set separately and differently. A numerical search approach is presented in this paper to find the optimal setting of the power spectral density for each type of GPS/BDS satellite by a series of tests. Based on the optimal stochastic model, a 3-dimensional (3D) real-time orbit accuracy of 0.7–2.0 m for position and 0.7–1.7 mm/s for velocity could be achieved only with dual-frequency BDS measurements and the broadcast ephemeris, while a notably superior orbit accuracy of 0.3–0.5 m for position and 0.3–0.5 mm/s for velocity is achievable using dual-frequency GPS/BDS measurements, due to the absorption effect of the estimated pseudo-ambiguity on the LOS error of the GPS/BDS broadcast ephemeris. Compared to using GPS-alone data, the GPS/BDS fusion only marginally improves the onboard RTOD orbit accuracy by about 1–3 cm, but the inclusion of BDS satellites increases the number of the tracked GNSS satellites and thus speeds up the convergence of the filter. Furthermore, the GPS/BDS fusion could help suppress the local orbit errors, ensure the orbit accuracy and improve the reliability and availability of the onboard RTOD when fewer GPS satellites are tracked in some anomalous arcs.
With the rapid development of LEO communication constellations, the performance enhancement of existing medium and high orbit constellations has been realized by making full use of the characteristics of LEO communication satellites, such as high transmission rate, low orbit height and large constellation scale, which has attracted extensive attention and become a research hotspot. Based on the systematic analysis of the available resources of the LEO communication constellation, this paper presents a system architecture of navigation augmentation based on the LEO communication constellation. It analyzes the available constellation and frequency resources. The performance of improving the reception sensitivity of BeiDou user terminals and providing emergency backup positioning based on the LEO communication constellation is quantitatively evaluated through theoretical calculation and simulation analysis. The research results can provide a reference for designing and constructing an integrated positioning, navigation, and timing service system.
As the number of wireless applications and devices grows, higher standards for the quality of service and navigation performance of mobile networks are required. Numerous critical applications, including unmanned aerial vehicles, internet of things, digital twin, and military systems, require reliable communication and accurate navigation services. To meet these requirements, the development of the sixth generation (6G) network is necessary. 6G networks provide seamless 3-dimensional coverage in space–air–ground–sea area, as well as deep coupling of communication, sensing, and computation. 6G networks will be combined with low Earth orbit (LEO) satellites to construct a universal and intelligent integrated system of communication, sensing, and computing by utilizing the benefits of LEO satellites, such as miniaturization, modularity, large bandwidth, low latency, and wide area coverage. One of the critical construction tasks in this system is the integration of communication and navigation (ICAN), which can break the limitations of the global navigation satellite system, provide high-precision, robust navigation capability, and enable high-quality communication services. In this article, a comprehensive survey is presented for ICAN technologies toward LEO-enabled 6G networks (LEO-ICAN), including the framework design, system implementation, and key technologies. We also highlight the challenges and opportunities ahead faced by the LEO-ICAN system. Finally, the prospect development and future research trends are discussed, and a few ideas for practical and effective LEO-ICAN solutions are provided. This survey provides a reference for the theoretical design, technological innovation, and system implementation of LEO-ICAN, which is capable of coping with the demand of massive access and global seamless coverage in the upcoming 6G network era.
