Alternative systems and methods for global positioning, navigation, and timing
Patent Information
- Application Number
- KR1020257035364
- Authority / Receiving Office
- KR · KR
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-22
- Filing Date
- 2024-04-05
- Publication Date
- 2026-09-04
Smart Images
Figure PCT00014_ABST
Abstract
Description
Technology Field
[0001] Cross-reference regarding related applications
[0002] This application claims priority to U.S. application no. 18 / 613,775 filed on March 22, 2024, which is incorporated herein by reference in its entirety.
[0003] Field of invention
[0004] The disclosed invention relates to systems and methods for providing alternative global position, navigation, and timing information using opportunity satellite signals to update inertial guidance and clock systems. Background Technology
[0005] U.S. competitors and adversaries have spent the past several years developing capabilities to jam or spoof Global Positioning System (GPS) Position, Navigation, and Timing (PNT) signals. Consequently, military and civilian planners in the U.S. and elsewhere anticipate contingencies in which GNSS-provided PNT data becomes unavailable locally or globally for extended periods. Solutions exist that provide alternative or backup PNT capabilities for GNSS denials of lower severity, such as localized jamming or short-duration regional GNSS denials. However, existing solutions become increasingly ineffective when GNSS denials become widespread or persist for significant durations.
[0006] To address long-term regional or global denial of GNSS position and timing information, alternative solutions that do not rely on GNSS satellite constellations are required. The disclosed invention allows existing broadband communications satellites to be used as signal of opportunity (SoOP) to limit inertial and clock errors and to enable non-GNSS navigation devices, such as inertial guidance systems, to maintain accurate positioning and timing during extended periods of GNSS unavailability. The disclosed system provides a reliable and cost-effective global alternative to GNSS navigation.
[0007] Although systems providing alternative PNT solutions using opportunity signals are known in the technical field, the disclosed PNT as a service network offers several advantages. Because it is configured with an Internet of Things (IoT) architecture, the disclosed system functions as a mesh-type network that provides redundancy and resilience unavailable to conventional systems based on point-to-point architectures. Conventional systems using SoOPs have suffered from inadequate performance issues due to the low signal-to-noise ratio (SNR) of most commercial SATCOM signals. For example, conventional systems have attempted to use Iridium narrowband signals to bypass the low SNR of broadband SATCOM SoOPs. Conventional systems also use small omnidirectional antennas to collect SoOPs, which chronically fail to achieve an SNR sufficient to provide reliable PNT data. However, the disclosed system uses published SoOP snapshots collected by high-gain antennas, which provide a high SNR for better performance. The use of published high-fidelity SoOP snapshots also allows for the use of monitor stations that are not required to remain at a known location or time reference, and enables remote user stations to use computing resources with low size, weight, power, and cost. Finally, the disclosed network establishes a market for published alternative PNT information. Publishers to the market are encouraged to provide high-quality SoOP data from multiple sources across the globe. Thus, the market concept promotes resilient and accurate alternative PNT to replace rejected GNSS data.
[0008] These and other drawbacks of the prior art are resolved by one or more embodiments of the disclosed invention. Additional advantages and novel features of the invention will be described in part in the following description, and in part will be apparent to those skilled in the art upon review of the following specification or can be learned through the practice of the invention. The advantages of the invention can be realized and achieved particularly by the means, combinations, compositions, and methods indicated below. Brief explanation of the drawing
[0009] The features and objectives of the present invention and the manner of achieving them will become more apparent, and the present invention itself will be best understood by reference to the following description of one or more embodiments taken in conjunction with the accompanying drawings embedded in the text below and attached to this description. FIG. 1 is a table listing potential opportunity satellite signals for use with embodiments of the disclosed invention. FIG. 2 depicts a special computer system as used in an embodiment of the disclosed invention. FIG. 3 depicts a block diagram of a typical PNTaaS network as used in embodiments of the disclosed invention. FIG. 4 depicts a block diagram illustrating the temporal relationships between opportunity signals as used in embodiments of the disclosed invention. FIG. 5 depicts a block diagram of a receiver station as used in embodiments of the disclosed invention. FIG. 6 depicts a diagram of a Doppler determination of positional degrees of freedom as used in embodiments of the disclosed invention. The drawings depict embodiments of the invention for illustrative purposes only. Those skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods exemplified herein may be utilized without departing from the principles of the invention described herein. Specific details for implementing the invention
[0010] Definitions
[0011] PNT stands for Position, Navigation, and Timing information. Specifically, Position refers to an object's latitude, longitude, and altitude / height relative to the Earth's surface. Navigation refers to an object's ability to move from one known location to another known location. Timing refers to an object's ability to determine the current local time at its position.
[0012] A-PNT, or Assured PNT, refers to a system for determining PNT solutions for high resilience to achieve the required level of accuracy.
[0013] PNT as a Service (PNTaaS) refers to the provision of guaranteed PNT information through Internet of Things protocols, where PNT information is published for use by service subscribers.
[0014] The Internet of Things (IoT) architecture refers to a scalable, distributed computing network in which devices interact with the network through cloud-based software applications.
[0015] Global Navigation Satellite Systems (GNSS) refers to one of several global satellite-based systems that provide autonomous PNT information.
[0016] The Global Positioning System (GPS) is a type of GNSS deployed by the United States.
[0017] details
[0018] The disclosed invention relates to systems and methods for using opportunity satellite signals to provide a reliable alternative navigation system to replace GPS in the event of an extended driving suspension.
[0019] A PNT service configured using an Internet of Things architecture that publishes PNT information derived from opportunity satellite signals to subscribers over a network is disclosed herein. Monitor stations use high-gain antennas to capture high-quality signal snapshots and timing information from opportunity signals and publish them to the PNTaaS market. Distributed reference stations use the published PNT signals of opportunity information to calculate local time-of-arrival data for the relevant snapshots, and the reference stations then publish the data to the PNTaaS market. Subscribers use the published PNT and time-delay data to update onboard guaranteed PNT systems, including an inertial navigation system and a Software Defined Radio (SDR) equipped with a precision clock. By periodically updating and correcting the A-PNT systems with SoOP-derived PNT information, subscribers can maintain operations in an extended GNSS denial environment. GPS and other global navigation satellite systems operate at fixed frequencies within the L band (1-2 gigahertz (GHz)), and as a result, make them easy targets for jamming or spoofing. SDR allows signal observation from alternative SATCOM signal sources across a certain range of frequency bands for improved resilience.
[0020] Internet of Things (IoT)-based architectures, such as a Data Distribution Service (DDS) architecture, utilize a widely used and scalable framework capable of accommodating high-performance, global implementations of the PNT services of the disclosed invention. Furthermore, the DDS framework incorporates features that ensure the disclosed services are accessible only by authorized users and resist cybersecurity threats.
[0021] Among the deployed commercial communications satellites, there are sufficiently potential signaling opportunities for use according to the present invention. While dedicated navigation satellites have very limited allocated spectrum, satellite communications services generally have substantial frequency allocations in the 3-30 GHz range. As of early 2023, the U.S. FCC has listed nearly 200 approved geostationary (GEO) satellites and about 40 approved non-geostationary satellite orbit (NGSO) systems for broadcast, fixed, and mobile satellite services. Additionally, a surge in low Earth orbit (LEO) systems is available, including over 4,000 Starlink satellites, 700 OneWeb satellites, 120 Telesat satellites, 70 Iridium satellites, and 40 satellites from O3B, with over a thousand launches announced. Referring to Fig. 1, the spectrum of some potential SATCOM signals and their assigned bands is shown.
[0022] Now, the disclosed invention will be described in detail with reference to various embodiments as illustrated in the accompanying drawings. In the following description, specific details are described to provide a thorough understanding of the embodiments of the disclosed invention. However, it will be apparent to those skilled in the art that the embodiments may be practiced without some or all of these specific details. In other instances, widely known process steps and / or structures have not been described in detail so as not to unnecessarily obscure the invention. The features and advantages of the embodiments may be better understood with reference to the following drawings and discussions.
[0023] It should be apparent to those skilled in the art that the described embodiments of the invention disclosed herein are merely exemplary and not limiting, and are presented only as examples. All features disclosed in this description may be replaced by alternative features that perform the same or similar purposes, unless explicitly stated otherwise. Accordingly, many other embodiments of modifications are intended to fall within the scope of the disclosed invention and its equivalents as defined herein. Therefore, the use of absolute and / or sequential terms such as, for example, “always,” “will,” “will not,” “shall,” “shall not,” “must,” “must not,” “first,” “initially,” “next,” “subsequently,” “before,” “after,” “lastly,” and “finally” is not intended to limit the scope of the disclosed invention, because the embodiments disclosed herein are merely illustrative.
[0024] When an element is referred to as being "on" another element, "attached" to it, "connected" to it, "coupled" to it, "in contact" to it, "mounted" to it, etc., it will also be understood that it may be directly on the other element, may be attached to it, may be connected to it, may be coupled to it, or may be in contact with it, or that there may also be interposed elements. In contrast, when an element is referred to, for example, as being "directly on" another element, "directly attached" to it, "directly connected" to it, "directly coupled" to it, or "directly in contact" with it, no intermediate elements exist. It will also be recognized by those skilled in the art that references to structures or features placed "adjacently" to another feature may have parts that overlap or lie beneath the adjacent feature.
[0025] Spatially relative terms such as "under," "below," "lower," "over," "upper," and so on may be used to describe the relationship of one element or feature to other element(s) or feature(s) as exemplified in the drawings. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. For example, if the device in the drawings is inverted, then elements described as being "under" or "below" other elements or features will be oriented "above" other elements or features. Thus, the exemplary term "under" may encompass both orientations of "above" and "under." The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein may be interpreted accordingly. Similarly, terms “upward,” “downward,” “vertical,” “horizontal,” and others are used herein solely for illustrative purposes, unless otherwise specifically indicated.
[0026] Flowcharts illustrating examples of methodologies that can be used for AI guidance and conventional algorithmic processes are included in the description. Each block and combination of blocks described in the flowchart examples may be implemented by computer program instructions. These computer program instructions may be loaded onto a computer, a computer system based on special-purpose hardware, or another programmable device to create a machine that produces means for implementing the functions specified in the flowchart blocks or blocks. These computer program instructions may also be stored in computer-readable memory and may instruct the computer or other programmable device to function to produce articles that implement the functions specified in the flowchart blocks or blocks. The computer program instructions may also be loaded onto a computer or other programmable device to cause a series of operational steps to be performed so that the executed instructions provide steps for implementing the functions specified in the flowchart blocks or blocks.
[0027] Unless otherwise specifically stated, discussions herein using words such as “processing,” “computing,” “calculation,” “decision,” “presentation,” “display,” or etc. may refer to actions or processes of a machine (e.g., a computer) that manipulate or transform data expressed as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or combinations thereof), registers, or other machine components that receive, store, transmit, or display information.
[0028] Special computer systems
[0029] Parts of the disclosed invention may be implemented, at least partially, on a special computer system, for example, a software-defined radio. FIG. 2 is a general block diagram of a special-purpose computer system on which software implementation processes of the disclosed invention may be implemented. As illustrated, the system (200) may include one or more central processing units (CPUs) or processors (201) coupled to a random-access memory (RAM) (202), a read-only memory (ROM) (203), a fixed storage device (209) (e.g., a hard disk, a flash drive), a communication (COMM) port(s) or interface(s) (210), and a high-speed network interface card (NIC) (211), and may include a radio frequency (RF) processor (214). The system may be accessed by a networked computing device, such as an aviation terminal (205) having a user interface (207), for example, input buttons and knobs, or a keyboard and display (215) (for example, a screen, a touchscreen, or a monitor), or, in some embodiments, through a software interface, for example, a software application for controlling an unmanned aerial vehicle. Although not individually illustrated, a real-time system clock is included with the system (200) in a conventional manner.
[0030] The CPU (201) includes a suitable processor for implementing the disclosed invention. The CPU (201) communicates with other components of the system through a bidirectional system bus (212), any necessary input / output (I / O) controller (213) circuitry, and other "glue" logic. A bus including address lines for addressing system memory provides data transfer between various components. RAM (202) functions as working memory for the CPU (201). ROM (204) includes basic I / O system code (BIOS), which is a set of low-level routines within the ROM that application programs and operating systems can use to interact with the hardware, including reading characters from a keyboard, etc. Some embodiments include a graphics processing unit (GPU) (not shown) to add processing capabilities to the system.
[0031] Mass storage devices (209) provide permanent storage on fixed and removable media such as magnetic, optical, or magneto-optical storage systems, flash memory, or any other available mass storage technology. Mass storage may be shared over a network, for example, cloud storage, or it may be a dedicated mass storage device. As illustrated in FIG. 2, fixed storage (209) stores a body of data and program instructions to direct the operation of a computer system, including an operating system, user application programs, drivers, and other support files, as well as other data files of all kinds. Typically, fixed storage (209) functions as the main memory for the system.
[0032] In operation, program logic (including implementing the methodology of the disclosed invention described herein) is loaded from fixed storage (209) into main (RAM) memory (202) for execution by the CPU (201). During the operation of the program logic, the system (200) receives user input from other computing devices, keyboards, mice, input buttons (207), touchscreens (215), etc. The user interface (207) allows for the selection of application programs, input or data based on software applications, or selection of keyboard-based input, and the selection and manipulation of individual data objects represented by software applications or displayed on the screen or display (215). Likewise, the user interface (207), such as input buttons, a mouse, or, in the case of a touchscreen, a finger, allows for the selection and manipulation of objects on the display device. In this way, these input devices support automatic or manual user input for any process running on the system. In some embodiments, the computer system (200) displays text and / or graphic images and other data on a display device (215). A field programmable gate array (FPGA) (206) provides flexible logic resources for performing certain specialized complex functions.
[0033] The system itself communicates with other devices (e.g., other software-defined radios, servers, or computers) through a port on a NIC (211) connected to a network (e.g., cellular, WIFI, SATCOM, or Ethernet). The system may also communicate with local devices (e.g., serial cable-linked devices) that are occasionally connected through a COMM interface (210) which may include a serial port, a Universal Serial Bus (USB) interface, or the like. The SDR operates with a transceiver module that includes an RF processor (214) for receiving and processing RF signals collected using an omnidirectional antenna or other suitable antenna.
[0034] The system may be implemented through various networks and their associated communication devices. Such networks may include SDRs, servers, modems, or computers, such as gateway computers or application servers capable of accessing the cloud computing system. The gateway computer functions as an entry point into each network and may be coupled to other networks via communication links. The gateway may also be coupled directly or indirectly to one or more devices using communication links, or may be coupled to a storage device such as a data store or database.
[0035] PNTaaS Architecture
[0036] The disclosed alternative navigation system can be configured to provide PNT as a Service (PNTaaS) to subscribers. Participants on a PNTaaS network publish to and subscribe to the network using Internet of Things (IoT) protocols. The IoT protocols encrypt participant data and perform authentication to secure access to the network and protect the integrity of published information. Subscribing users can access the network, where they have visibility into available SoOPs, ephemeris or satellite positioning data, snapshot information, etc., and can subscribe to selected data from any monitor, reference, or other PNT information publishers. Each participant within the network publishes or subscribes individually. The network is a mesh-type network hosted on the individual processing and memory capacities of the participants or on cloud computing resources. Relays allow participants to view publishers and subscribers.
[0037] Referring to FIG. 3, an exemplary PNTaaS IoT network is depicted. One or more monitor stations (310) receive opportunity signals (321) broadcast by GEO, MEO, and / or LEO satellites (320). A monitor station may include one or more high-gain or steered array antennas (311) to observe SATCOM broadcasts, or the monitor station may access signal broadcasts received by external high-gain or steered array antennas. The monitor station also includes an SDR that records a snapshot of the satellite signal at a specified time mark. A snapshot captured by a monitor station is accompanied by a packet of data regarding the snapshot, including a SoOP satellite identifier, a time mark of the snapshot, the center frequency of the signal, a sample rate, the duration of the snapshot, and an interval at which new SoOP snapshots will be captured. The monitor station then publishes the snapshot and the accompanying data to the network. Other entities may also publish information to the network. For example, commercial satellite companies may publish highly accurate position information for their satellites, or publish their own signal snapshots and associated data for use on the network. Alternatively, a SATCOM terminal may function as a monitor station to provide snapshots, timing data, and ephemeral or position data directly to the network. The system does not require the monitor station to have a known position or time reference.
[0038] One or more reference stations (340) within the region of interest subscribe to and publish to a PNTaaS network to provide local timing information for multiple SoOPs. The reference station includes an SDR and one or more broadband omnidirectional antennas (341) to observe multiple locally available SoOPs. The reference station also includes direct or indirect access to a master clock, such as the US Naval Observatory master clock, and may include a high-precision internal clock. The internal timing reference of the reference station allows the reference station to establish a common time mark for a specific SoOP snapshot and publish it to the network. Due to inherent delays in snapshot timing, such as those captured by a monitor station, the reference station's local time mark for the snapshot is required. The delays caused by the use of a monitor station (310) with a high-gain dish or phase array antenna can be significant, and thus, any correlation with the snapshot may be biased to calculate the time of arrival (TOA). Therefore, these delays need to be calibrated, and reference units provide compensation for any offset of the snapshot timing collected by the monitor stations.
[0039] In operation, the reference station subscribes to a subset of published data from satellite signals visible to the reference station (340). Using the published SoOP data, the reference station captures its own snapshot from each subscribed SoOP at the time slots and intervals used by the publisher and calculates the reference time to arrive. The reference time to arrive is the time the snapshot is received at the reference station and is time-tagged precisely to the reference station's internal timing reference. The reference time to arrive is calculated by the cross-correlation between the published snapshot and the corresponding reference station snapshot. Such cross-correlation between the published snapshot timing and the reference snapshot timing is achieved in near real-time through the use of a Fast Fourier Transform algorithm running on the firmware of the reference station (SDR).
[0040] Next, the reference station publishes the reference TOA to the PNTaaS network (330) along with the exact location of the reference station. Remote users (350) can subscribe to one or more reference stations and use the reference TOAs to correct timing offsets in the published monitor station snapshots, thereby allowing the remote users to generate accurate local pseudo-range observations from the published SoOP snapshot data. Thus, the reference TOAs allow the remote users to use unsynchronized SoOPs because they do not require external timing references from a specific set of time-synchronized satellites.
[0041] Subscribers to the PNT service access snapshots and other data published by connecting their remote receiver (350) to the network (330). The remote station is an SDR having one or more broadband omnidirectional antennas (351) and a precision local clock. For static receivers, the known location of the SDR antenna is input, and as a result, the remote station can calibrate its local time reference and output a 1 pps (pulse per second) signal synchronized with the PNTaaS network master time reference, and optionally a 10 MHz signal. Such outputs allow the user to use the remote receiver as an externally calibrated clock reference. For mobile receivers, an inertial measurement unit is included to provide dead-reckoning navigation between SoOP updates, and SoOP observations can be used to update both the remote receiver's time reference and its inertial navigation solution.
[0042] Subscribers accessing the network are provided with a market for various types of PNT information, such as information from specific publishers, specific opportunity signals, information provided by commercial satellite companies, satellite orbit locations, etc. Subscribers may select which information to receive based on resources, SDR reception capabilities, antenna configuration, processing capabilities, known or persistent local signal interference, signal band preferences, location, areas of operation, vehicle type, etc. For example, a preferred subset of SoOPs may be selected based on the subscriber's navigation requirements or the threat environment facing the remote station. The flexibility of SoOPs and other PNT information used by remote receivers provides a high degree of resilience because subscriber units can adapt to threats by utilizing multiple different signals, operating on different frequency bands, using one or more broadband antennas, and with signal options continuously updated as new satellite systems come online. Furthermore, the use of a system of monitor stations equipped with high-gain antennas to capture SoOP snapshots allows remote receivers to be simpler, lower-performance devices, which improves system practicality.
[0043] Once a subscriber selects a set of PNT information for subscription, the subscriber configures its receiver to use the selected PNT information. For example, the subscriber may set up an internal snapshot capture sequence to use the subscribed set of SoOPs. The capture sequence may include setting their SDR to the SoOP frequency and adjusting the timing of the snapshot capture to correspond to the timing of the published snapshot. Then, the remote receiver observes the SoOP snapshot and calculates the receiver arrival time for the signal using the receiver's internal clock or time reference to cross-correlate with the corresponding SoOP snapshot published by the monitor station. The remote receiver also subscribes to published satellite positions and local reference TOAs from the network to correct local clock errors and allow correlation with the network master clock. Then, the remote receiver calculates a pseudo-range (PR) and uses the PR to update and correct the onboard inertial navigation and timing solutions.
[0044] Doctor scope calculation
[0045] The basic calculation required to update PNT data for remote receivers is the pseudo-range calculation, which is also a default value provided by GNSS systems. Monitor stations publish snapshot and timing sequence data for various SoOPs to the PNTaaS network, and reference stations publish reference TOA data for locally observable SoOPs, where each snapshot is associated with an accurate internal reference time. Subscribing remote receivers access the snapshot and timing data published over the network and capture their own snapshots at the published times for specific SoOPs. The remote receivers store their snapshots internally.
[0046] Referring to FIG. 4, a block diagram illustrating snapshot correlation is depicted. A reference station (410) subscribes to PNT data on various SoOPs, collects snapshots on a subset of published SoOPs (401, 402, 403, 404), and publishes reference TOAs for each signal via a PNTaaS network. Similarly, a remote receiver (420) subscribes to PNT data on a subset of SoOPs and collects its own snapshots (405, 406, 407, 408) for each signal. Then, the remote receiver determines the TOAs for each signal for its internal clock. Then, the remote receiver performs a difference analysis between its internal TOAs and the published reference TOAs for each signal. For example, the reference station publishes the reference TOA (411) for SoOP1 (401) and the reference TOA (412) for SoOP2, while the remote receiver calculates the remote TOA (421) for SoOP1 and the remote TOA (422) for SoOP2. Taking into account the shared snapshot duration, the remote receiver determines the TOA offset between the reference station and the remote receiver, expressed here as the difference between 412 and 421. Snapshot correlation between the monitors, references, and remote receivers can be performed only when there is an overlap of snapshot durations and interval timings that allows for the measurement of the TOA offset. Thus, snapshot capture is synchronized so that the monitor station publishes data captured in time slots that overlap between the monitors, reference stations, and remote receivers. In a representative embodiment, SoOP snapshots are published with a duration of 85 milliseconds (ms). This duration allows overlap between network participants, even if there are errors of a few milliseconds in timing synchronization between participants at startup.
[0047] Using the TOA offset and reference receiver position, the remote receiver uses the following mathematical formula to determine the pseudo-range (PR REM Calculate )
[0048] PR REM = (TOA REM - TOA REF ) + R REF = R REM + Bu (Mathematical Formula 1)
[0049] Here, R REF is the range from a broadband satellite source for opportunity signals to the location of a reference station calculated from satellite ephemeris published to the PNTaaS network. Here, R REM is the range from the satellite to the location of the remote receiver, calculated from the satellite location as published to the network. Here, Bu is the TOA offset of the remote receiver's local time, calculated using the reference station time reference.
[0050] Next, the pseudorange and published satellite position data calculated via Equation 1 are used to update the inertia and clock PNT solutions produced by the remote receiver. The software application executed by the remote receiver SDR includes data fusion algorithms that allow delayed pseudorange observations to update the real-time inertia and clock PNT solutions. Therefore, the PNTaaS system is not affected by network latency effects.
[0051] Signal-to-noise ratio and TOA accuracy
[0052] The TOA calculated using Equation 1 will have an accuracy value as a function of the signal-to-noise ratio (SNR), taking into account the observed SoOP signal power as received by the SDR, the sampled bandwidth, the length of the SoOP snapshot, and the SDR processing loss. The disclosed PNTaaS system is configured to achieve an SNR comparable to dedicated GPS and other GNSS, a bandwidth comparable to SoOP signal captures, and thus a comparable level of accuracy. Normally, receivers for broadband communications satellites must include high-gain dish antennas or steered antenna arrays to achieve the link margin required for proper data demodulation. It would be impractical to place such antennas at each remote receiver and reference station in the PNTaaS system. Therefore, only the monitor station is equipped with a high-gain antenna, or, in some embodiments, is provided with access to existing high-gain antenna data. Using these antennas, the monitor station captures SoOP snapshot data with a high SNR and publishes it to the PNTaaS network.
[0053] Consequently, when reference stations and remote receivers correlate published SoOP snapshots with their observed SoOP snapshots, the SNR is a function of the SoOP duration, the received signal / noise power in the SoOP bandwidth, and the processing loss in the receiver SDR. Assuming the reference stations and remote receivers use zero-gain omnidirectional antennas and SDRs with a processing loss of 5 decibels (dB), SoOP durations within the 85-millisecond range provide SNRs within the 22 dB range for TOA correlation, which is comparable to that of GPS. The use of a system of monitor stations to capture SoOP snapshots with high SNR allows system users to utilize simpler, lower-power remote receivers equipped with low-cost, low-gain omnidirectional antennas.
[0054] Software Defined Radio PNT Device
[0055] The disclosed PNTaaS system is configured to use specialized SDRs at reference stations and remote receiver locations. A typical mobile PNTaaS SDR couples a radio module capable of operating across multiple frequency bands with an inertial measurement unit and a clock module. Referring to FIG. 5, an exemplary PNTaaS SDR configuration (500) is depicted. The SDR (510) includes a computing module (511) and a transceiver module (512). The computing module may be a specialized computing system, for example, as depicted in FIG. 2. The computing module operates the transceiver module and executes a software application (513). The SDR is modular in design and configured to operate with interchangeable input components. In some embodiments, the SDR (510) also receives PNT data input from a GPS or GNSS unit (520), which also directly supplies range information to a fusion algorithm. An inertial measurement unit (IMU) (530) provides inertial measurement data to the computing module. Optionally, other A-PNT supporting sources, such as a speed sensor (540), provide vehicle speed data to the computing unit for use in the fusion algorithm. To provide a stable internal SDR clock for time-tagging SoOP data, a chip-scale atomic clock (CSAC) or an oven-controlled crystal oscillator (OCXO) (550) is used. An antenna array (560), or a single broadband omnidirectional antenna, provides broadband satellite data to the transceiver (512). The array includes antennas configured to receive signals from a wide range of frequencies, for example, L band, S band, C band, X band, Ku band, and / or Ka band satellite frequency bands.Each antenna within the array can be tuned to a subset of frequencies, and in some embodiments, the antennas within the array can be tuned to cover multiple frequency bands. For example, other navigation aids, including altimeters, ground-based waypoint updates, zero-velocity updates, a Selective Availability Anti-Spoofing Module (SAASM) based GPS module, an M-code GPS receiver, satellite imagery aiding, or other suitable PNT input sources, may also be integrated into the SDR via a fusion algorithm. The mobile PNTaaS SDR provides a tightly coupled inertial navigation solution and clock integration with accurate time synchronization, while the static PNTaaS SDR provides a tightly coupled clock integration with a known location, thereby providing accurate time synchronization and functioning as a timing reference.
[0056] The PNTaaS SDR (510) is configured to integrate inputs from multiple SoOP sources and other observation results into a single fused output for an A-PNT solution produced by the SDR. Such coordination requires that all SDR navigation inputs be coupled to a common SDR time reference. In particular, the use of SoOP snapshots taken at different times, on different frequencies, and from different sources must be coordinated to the same time reference to observe a common range and calculate an accurate TOA offset. Furthermore, all IMUs, rates, and other modular navigation inputs must also be time-tagged to a common SDR time reference. The SDR achieves such time coordination by deriving all hardware time synchronization function (HW TSF) values through an FPGA phase-locked loop (PLL) driven by an onboard, e.g., OCXO unit, or an external high-quality reference oscillator coupled to a master reference clock by software. Once adjusted, the software application (513) calculates a fused A-PNT solution (514) using the available navigation inputs.
[0057] The precise timing of the SDR allows different SoOP sources to sequentially update the A-PNT solution from a single SDR channel without loss of precision. The SDR is configured to directly capture signal snapshots from frequencies within the L, S, and C bands, and in some embodiments, uses a low-noise block downconverter to downconvert and capture snapshots from higher frequency signals, e.g., the X, Ku, and Ka bands. The SDR can rapidly sequentially process across these different frequencies and generate hundreds of snapshot observations derived from available opportunity signals from different satellites within tens of seconds. The SDR can then use the collected snapshot observations to update the inertia and clock PNT solution. To allow such rapid sequential processing, the computing module (511) is configured to command the transceiver (512) to rapidly re-tun to different frequency bands, to perform snapshot capture synchronized through multiple RF channels, to perform high-speed data transmission, and to perform high-speed buffering of snapshots to allow additional signal processing.
[0058] In relation to the transceiver's ability to rapidly re-tun, the SDR is also configured to rapidly switch between antennas within the array (560). Each SDR channel can correspondingly accommodate multiple different antennas for high-speed onboard RF switching. In addition to the antenna switching required by operation across multiple frequency bands, the SDR can also switch antennas due to the motion of remote receivers. When a remote receiver is mounted on an aircraft, a ship, or a vehicle such as a car, the vehicle's orientation can result in the satellite becoming obscured and its signals becoming unavailable. Therefore, the SDR is configured to perform rapid antenna switching to accommodate SoOP frequency selection and to adjust for when the SoOP becomes unavailable based on attitude information provided by the IMU (530).
[0059] Satellite geometry decisions
[0060] The disclosed PNTaaS system provides optimal A-PNT updates when using SoOP from a combination of satellites in geosynchronous (GEO) and non-geosynchronous (NGSO) orbits. GEO satellites are primarily useful for SoOP navigation support because they provide sufficient coverage over a large portion of the Earth's surface. For most latitudes, a large number of satellites come into view at any given moment, while coverage attenuates toward the polar regions. However, PNT solutions that rely solely on signals from GEO satellites suffer from the fact that not all GEO satellites are located in the same plane, namely the equatorial plane, and therefore cannot provide 4D geometry. Because they are in the same plane, signals from GEO satellites, aided by a calibrated clock, can observe at best only 3 degrees of freedom at high latitudes or 2 degrees of freedom at low latitudes.
[0061] At higher latitudes, relying solely on available GEO SoOP signals, the PNTaaS SDR can supplement the PNT solution with additional inputs from a tuned clock (550) or altimeter (not shown) to provide appropriate geometry. The closer to the equator, the geometry will still be insufficient, because altitude and clock observability are also coplane with the equator and GEO satellite orbits. A typical chip-scale atomic clock, for example, 1E every 1000 seconds -11 Random drifts in the meter can be represented, meaning that time errors can be expected to drift by only 3 millimeters (mm) per second. Therefore, if periodic clock calibrations are available and altitude support is available, GEO-specific solutions can provide appropriate updates to maintain guaranteed PNT.
[0062] The use of SoOPs from satellites in Low Earth Orbit (LEO) presents observation geometry different from that of GEO satellites. Because their orbits are substantially lower, LEO satellites have a smaller coverage footprint than GEO satellites. LEO satellites also move relative to the Earth's surface and are therefore observable by the SDR during a finite time window known as a pass or transit. As an LEO satellite passes through the SDR's observable window, the received SoOP can provide at most 2-degree-of-freedom updates to the PNT solution. Therefore, like GEO-only solutions, LEO-only solutions are insufficient to update the PNT solution.
[0063] However, the SDR can derive a 4D solution using Doppler shift observations from LEO satellites. Referring to FIG. 6, an exemplary geometry for using LEO Doppler shift to update the PNT solution is depicted. With the SDR located at 600, as the LEO satellite (610) passes through an observable window in the direction of the arrow (12), the SDR observes the Doppler shift of the satellite signal and uses the observed rate of change to determine the time of the closest approach between the SDR and the satellite (610), or the signal of the closest approach, as well as the ascent from orbit (620). In this way, two degrees of freedom are derived from the Doppler shift information. When the two degrees of freedom provided by the SoOP snapshot from the satellite during the satellite's passage window are added to the TOA calculation, the full 4D update can be produced. Typically, multiple satellites in LEO or medium Earth orbit (MEO) will be observable by SDR at any given moment or for a short duration, i.e., less than 10 minutes, and can be used to construct a complex PNT solution.
[0064] Additionally, some LEO satellite constellations provide additional navigation information that can also be used to support PNT solutions. This includes, for example, Iridium time and position signals, or TOA information provided via Xona Pulsar TOA signals. Starlink constellations broadcast pilot tones that can be used to provide Doppler-only updates. These TOA observations can also be collected at reference stations and published to a PNTaaS network along with known signal content to allow them to be used as SoOPs. For LEO satellite signals containing broadband pseudo-random data content, such as Starlink or OneWeb, an LEO SATCOM terminal can function as a monitor station. The satellite terminal includes a high-gain antenna used to increase the signal's SNR and provide sufficient link margin for the SATCOM data link to operate. By connecting the PNTaaS SDR to the intermediate frequency (IF) output from the high-gain antenna and down-converter unit of the SATCOM terminal, snapshots can be captured and published directly from the SATCOM terminal. Other reference or remote units in the same footprint of the LEO satellite beam can subscribe to the snapshot data published by the SATCOM terminal and use their signals to drive the PNT solution.
[0065] Although the SDR of the disclosed system can produce sufficient PNT updates using GEO or NGSO satellites, a solution using SoOPs from composite signals of GEO or NGSO satellites is the preferred mode of operation. Through GEO satellites providing continuous coverage and LEO or MEO satellites providing superior geometry for lower latitudes, the combined observations allow for 4-degrees-of-freedom solutions for A-PNT calibrations by the SDR. The PNTaaS network can accommodate an infinite number of satellite signals and does not rely on any single satellite constellation or satellite service provider. Such flexibility allows new signals to be added to the service when new satellites are launched. The network can also accommodate ground opportunity signals, provided that monitor or reference units are equipped to process such signals and positioned so that ground signals are visible. The IoT protocol provides subscribers with dynamic awareness of which SoOPs are available at any given time and allows filtering of SoOPs to select only those signals that are within the subscriber's receiver's line of sight and compatible with the subscriber's receiver.
[0066] When multiple SoOP sources are available, the SDR performs a selection process to determine which SoOPs will be included in the PNT update solution. In addition to performing real-time threat detection as described below, the SDR evaluates available signals according to the following exemplary process. First, the SDR filters published SoOP data based on published SoOP center frequencies, e.g., L-band, C-band, etc., or orbit types and locations, e.g., GEO, MEO, or LEO. Monitor stations publish SoOP data with unique identifiers for each SoOP. Accurate location data for satellites associated with a given SoOP is also periodically published to the network. SoOP location data services may be provided by third parties, such as satellite operators, or may be calculated using orbit determination software, such as NASA Jet Propulsion Laboratory's GIPSYx software, using reference TOAs from a network of reference stations. Using published satellite locations and remote receiver locations, altitudes are calculated for the satellites, and satellites having altitudes above selected mask angles are selected. The elevation angle is set to ensure appropriate geometry or other appropriate criteria to facilitate antenna reception. Next, the remaining satellites are classified based on their degree of separation from one another, and satellites providing the best geometry for the A-PNT solution with sufficient redundancy for guaranteed operation are selected. Satellites may also be selected based on frequency separation to prevent intentional or incidental spectral interference. Once a subset of satellites is selected for use, the remote receiver subscribes only to the selected SoOP, which reduces the data traffic required to configure the PNT update solutions.
[0067] Fast Fourier Transform
[0068] The signal processing requirements imposed on the PNTaaS SDR computing module (see Fig. 5, Item 511) by the A-PNT update process can be substantial. Such real-time processing requirements are facilitated by SDR firmware configured to perform simultaneous complex in-phase and orthogonal data capture, as well as real-time Fast Fourier Transforms (FFTs) on the sampled data. The use of FFT-based correlation for TOA observations is not only computationally efficient, but the FFT capability also allows for rapid Doppler search for the acquisition of LEO signals. FFT-based correlation and Doppler search are achieved through the following equations:
[0069]
[0070] Here, FT REM is the FFT of the remote receiver snapshot data. FFT MON is the FFT of the published monitor station snapshot data. And, Δf is a shift to search for integer Doppler intervals [-Fsearch:Fsearch]*T, where Fsearch is the peak Doppler frequency and T is the snapshot FFT length in seconds.
[0071] The SDR is also configured to use FFT spectrograms to perform real-time RF threat detection and mitigation. The SDR generates FFT spectrograms in real-time over observed SoOP snapshots and then compares the spectrograms to signal profiles included in the neural network. The neural network is trained using machine learning (ML) algorithms against validated signal profiles generated from previously collected signals. Based on the comparison with the validated signal profiles through the neural network, the A-PNT module selects or deselects new signals to include in the PNT update solution. Signals showing evidence of tampering, spoofing, or other alterations—that is, signals deviating from the neural network's validated signal profiles—are excluded from the A-PNT solution. The neural network can be generated and trained locally on the PNTaaS SDR, or the neural network can be published to the PNTaaS network for use by subscribers.
[0072] Some parts of this specification are presented in terms of symbolic representations or algorithms of operations on data stored as bits or binary digital signals within machine memory (e.g., computer memory). These algorithms or symbolic representations are examples of techniques used by those skilled in the art of data processing to convey the nature of their work to others skilled in the art. As used herein, "algorithm" is a self-contradictory sequence of operations or similar processing leading to a desired result. In this context, algorithms and operations involve the manipulation of information elements. Typically, but not necessarily, such elements may take the form of electrical, magnetic, or optical signals that can be stored, accessed, transmitted, combined, compared, or otherwise manipulated by a machine. Primarily for reasons of common usage, it is sometimes convenient to refer to such signals using words such as "data," "content," "bits," "values," "elements," "symbols," "characters," "terms," "numbers," "numerical values," "words," "materials," etc. However, these specific words are merely convenient labels and relate to the appropriate information elements.
[0073] Unless otherwise specifically stated, discussions herein using words such as “processing,” “computing,” “calculation,” “decision,” “presentation,” “display,” or etc. may refer to actions or processes of a machine (e.g., a computer) that manipulate or transform data expressed as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or combinations thereof), registers, or other machine components that receive, store, transmit, or display information.
[0074] Upon reading this disclosure, those skilled in the art will be well aware of additional and alternative structural and functional designs for systems and processes for providing operational network nodes enhanced through the principles disclosed herein. Accordingly, while specific embodiments and applications have been illustrated and described, it should be understood that the disclosed embodiments are not limited to the exact configurations and components disclosed herein. Various modifications, changes, and variations that will be apparent to those skilled in the art may be made to the arrangements, operations, and details of the methods and apparatus disclosed herein without departing from the spirit and scope of the invention.
[0075] It will also be understood by those familiar with the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the present invention. Likewise, specific naming and classification of modules, managers, functions, systems, engines, layers, features, attributes, methodologies, and other embodiments are not essential or important, and mechanisms embodying the present invention or its features may have different names, classifications, and / or formats. Furthermore, as will be apparent to those skilled in the art, the modules, managers, functions, systems, engines, layers, features, attributes, methodologies, and other embodiments of the present invention may be embodied in software, hardware, firmware, or any combination of these three. Of course, wherever the component of the present invention is implemented as software, the component may be implemented as a script, as a standalone program, as part of a larger program, as a plurality of separate scripts and / or programs, as a statically or dynamically linked library, as a kernel-loadable module, as a device driver, and / or in any and any other manner currently known or to be known in the future to those skilled in the art of computer programming. Additionally, the present invention is not in any way limited to an implementation of any particular programming language, or an implementation for any particular operating system or environment.
[0076] Although the principles of the present invention have been described above, it should be clearly understood that the foregoing description is made merely as an example and not as a limitation to the scope of the present invention. In particular, it is recognized that the teachings of the foregoing disclosure will suggest other modifications to those skilled in the art. Such modifications may involve other features that are already known in themselves and may be used in place of or in addition to the features already described herein. Although the claims in this application are made of specific combinations of features, it should be understood that the scope of the disclosure herein also includes any novel feature, any novel combination of features explicitly or implicitly disclosed, or any generalization or modification thereof that will be obvious to those skilled in the art, whether such relate to the same invention as currently claimed in any claim, and whether it alleviates any or all of the same technical problems faced by the present invention. The applicant thereby reserves the right to formulate new claims for such features and / or combinations of such features during the examination of this application or any additional application derived therefrom.
[0077] Although the present invention has been described in terms of various embodiments, there are variations, modifications, substitutions, and alternative equivalents that fall within the scope of the invention. Subsection headings are provided to aid in describing the invention, but these headings are merely illustrative and are not intended to limit the scope of the invention. Furthermore, where claim limitations are identified, for example, by numbers or letters, they are not intended to imply any specific sequence.
[0078] It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. Accordingly, the following appended claims are intended to be interpreted as including all such modifications, alterations, substitutions, and alternative equivalents that fall within the true spirit and scope of the present invention.
[0079] [1] A navigation system comprising the following is disclosed:
[0080] A network for communicating position, navigation, and timing (PNT) information to subscribers;
[0081] A monitor station accessing a high-gain antenna to receive signals broadcast from a satellite - the monitor station captures a snapshot from the signal and publishes the snapshot to the network - ;
[0082] A reference station including a first Software Defined Radio (SDR) - the reference station accesses the network, calculates the reference Time of Arrival (TOA) for a snapshot, and publishes the reference TOA to the network - ; and
[0083] Remote receiver including a second software-defined radio - the remote receiver accesses the network and uses snapshots and reference TOA to produce a PNT solution - .
[0084] [2] As a system of Clause [1], the remote receiver comprises a fusion algorithm that receives a set of inputs from one or more of an inertial measurement unit, a global navigation satellite system, a speed sensor, and a clock, and the remote receiver produces an updated PNT solution using the set of inputs and the PNT solution.
[0085] [3] As a system of Clause [1], the remote receiver includes one or more antennas for receiving one or more of the following bands of radio frequencies: L band, S band, C band, X band, Ku band, and Ka band.
[0086] [4] As a system of Clause [1], the remote receiver includes a transceiver configured to perform onboard frequency switching and synchronized snapshot capture across multiple bands of radio frequencies.
[0087] [5] As a system of Clause [1], the remote receiver includes a zero-gain omnidirectional antenna.
[0088] [6] A method for providing positioning, navigation, and timing as a service (PNTaaS), the method comprises the following:
[0089] Collecting snapshots of opportunity signals broadcast by satellites using a monitor station;
[0090] Associate a snapshot with a data packet including a satellite identifier, the time of collection, and the collection interval;
[0091] Publishing snapshots and data packets to the network;
[0092] Providing snapshots and data packets to a reference station that is a network subscriber - the reference station generates a reference snapshot from the signal, generates the reference Time of Arrival (TOA) of the snapshot, and publishes the reference TOA and reference station location to the network -; and
[0093] Providing snapshots, data packets, and reference TOA to remote receivers, which are network subscribers—the remote receivers generate remote snapshots from the signals, generate the remote Time of Arrival (TOA) of the snapshots, and yield PNT solutions.
[0094] [7] As a method for providing the PNTaaS of Clause [6], the monitor station accesses one or more high-gain antenna(s) or one or more steered array antenna(s) to capture snapshots.
[0095] [8] As a method for providing PNTaaS of Clause [6], the publishing step further includes publishing satellite position data, and the publishing step is performed by one of the following: a commercial satellite communications terminal, or a commercial satellite operator.
[0096] [9] As a method for providing PNTaaS of Clause [6], the opportunity signal may be one of the bands of the following radio frequencies: L band, S band, C band, X band, Ku band, and Ka band.
[0097]
[10] As a method for providing PNTaaS of Clause [6], the following are further included:
[0098] Setting the snapshot duration and snapshot interval to allow the remote receiver to measure the TOA offset for the signal.
[0099]
[11] As a method for providing PNTaaS of Clause [6]: further include publishing a master clock reference to the network, and a remote receiver generates a time reference signal that is synchronized with the master clock reference.
[0100]
[12] As a method for providing PNTaaS of Clause [6], the network is a mesh network with an Internet of Things architecture.
[0101]
[13] A method for calculating a position, navigation, and timing (PNT) solution at a remote receiver, including the following:
[0102] Accessing snapshots captured from signals broadcast by satellites - snapshots are published to the network - ;
[0103] Generating a remote snapshot from a signal that includes the Time of Arrival (TOA) for a remote time reference;
[0104] Receiving a reference station, the location of the reference station, the reference TOA of the signal, and a reference identifier indicating the reference range observed from the satellite to the reference station;
[0105] Determining the remote arrival time for a remote clock;
[0106] Generating a pseudo-range from the satellite to the remote receiver; and
[0107] Calculating the PNT solution at the remote receiver using the pseudo-range.
[0108]
[14] As a method for producing a PNT solution from a remote receiver in Clause
[13] , the pseudo-scope is as follows:
[0109] ,
[0110] Here, is the arrival time from the remote receiver, and is the standard TOA, and is the standard range, and is the remote range observed from the satellite to the remote receiver, and TOA is the TOA offset for the signal.
[0111]
[15] As a method for calculating the PNT solution at the remote receiver of Clause
[13] , the monitor station publishes the snapshot duration and snapshot interval to allow the remote receiver to measure the TOA offset.
[0112]
[16] As a method for calculating the PNT solution at the remote receiver of Clause
[13] , a set of location data regarding the satellite is posted to the network.
[0113]
[17] As a method for producing a PNT solution at a remote receiver of Clause
[13] , the following are further included:
[0114] Generating Doppler observation results for the satellite; and
[0115] Calculating the PNT solution at the remote receiver using Doppler observation results.
[0116]
[18] As a method for generating a PNT solution at a remote receiver of Clause
[13] , the access step further includes the following:
[0117] Generating a snapshot FFT spectrogram by performing a Fast Fourier Transform (FFT) on a snapshot; and
[0118] Comparing the snapshot FFT spectrogram to the signal profiles in the neural network to determine the suitability of the snapshot for pseudo-range calculation.
[0119]
[19] As a method for producing a PNT solution at a remote receiver of clause
[18] , a neural network uses a machine learning algorithm to generate a set of signal profiles from previously collected signals.
[0120]
[20] As a method for producing a PNT solution at a remote receiver of clause
[18] , a neural network is published to the network.
[0121] This was a description of the invention disclosed together with a preferred method for carrying out the invention.
Claims
Claim 1 A system for navigation, comprising: a network for communicating position, navigation, and timing (PNT) information to a subscriber; a monitor station accessing a high-gain antenna to receive a signal broadcast from a satellite - said monitor station captures a snapshot from said signal and publishes said snapshot to said network -; a reference station including a first software-defined radio (SDR) - said reference station accesses said network and develops a reference time of arrival (TOA) for said snapshot and publishes said reference TOA to said network -; and a remote receiver including a second software-defined radio - said remote receiver accesses said network and develops a PNT solution using said snapshot and said reference TOA - a system comprising Claim 2 In claim 1, the remote receiver comprises: a fusion algorithm that receives a set of inputs from one or more of an inertial measurement unit, a global navigation satellite system, a speed sensor, and a clock, and the remote receiver produces an updated PNT solution using the set of inputs and the PNT solution. Claim 3 In paragraph 1, the remote receiver comprises one or more antennas for receiving one or more of the following radio frequency bands: L band, S band, C band, X band, Ku band, and Ka band. Claim 4 A system according to claim 1, wherein the remote receiver comprises a transceiver configured to perform onboard frequency switching and synchronized snapshot capture across a plurality of bands of radio frequencies. Claim 5 In paragraph 1, the remote receiver comprises a zero-gain omnidirectional antenna, in a system. Claim 6 A method for providing positioning, navigation, and timing as a service (PNTaaS), comprising: using a monitor station to collect a snapshot of a chance signal broadcast by a satellite; associating the snapshot with a data packet including a satellite identifier, a time of collection, and a collection interval; publishing the snapshot and the data packet to a network; providing the snapshot and the data packet to a reference station that is a network subscriber, wherein the reference station generates a reference snapshot from the signal, generates a reference time of arrival (TOA) of the snapshot, and publishes the reference TOA and the reference station location to the network; and providing the snapshot, the data packet, and the reference TOA to a remote receiver that is a network subscriber, wherein the remote receiver generates a remote snapshot from the signal, generates a remote time of arrival (TOA) of the snapshot, and calculates a PNT solution. Claim 7 In claim 6, a method for providing PNTaaS, wherein the monitor station accesses one or more high-gain antenna(s) or one or more steered array antenna(s) to capture the snapshot. Claim 8 In paragraph 6, the above-mentioned posting step further comprises the step of posting satellite position data, and the above-mentioned posting step is: a method for providing PNTaaS performed by one of a commercial satellite communications terminal or a commercial satellite operator. Claim 9 A method for providing PNTaaS, wherein, in paragraph 6, the opportunity signal may be one of the following radio frequency bands: L band, S band, C band, X band, Ku band, and Ka band. Claim 10 A method for providing PNTaaS according to claim 6, further comprising the step of setting a snapshot duration and a snapshot interval to allow the remote receiver to measure a TOA offset for the signal. Claim 11 A method for providing PNTaaS according to claim 6, further comprising the step of posting a master clock reference to the network, wherein the remote receiver generates a time reference signal synchronized with the master clock reference. Claim 12 A method for providing PNTaaS in claim 6, wherein the network is a mesh network having an Internet of Things architecture. Claim 13 A method for calculating a position, navigation, and timing (PNT) solution at a remote receiver, comprising: accessing a snapshot captured from a signal broadcast by a satellite—the snapshot being published to a network—; generating a remote snapshot from the signal that includes a remote time arrival (TOA) for a remote time reference; receiving a reference identifier representing a reference station, the location of the reference station, the reference TOA of the signal, and a reference range observed from the satellite to the reference station; determining a remote time arrival for a remote clock; generating a pseudo-range from the satellite to the remote receiver; and calculating the PNT solution at the remote receiver using the pseudo-range. Claim 14 In Clause 13, the above scope of intent is Identical to, is the arrival time at the remote receiver, and is the above-mentioned standard TOA, and is the above standard range, and A method for calculating a PNT solution at a remote receiver, wherein is a remote range observed from the satellite to the remote receiver, and TOA is a TOA offset for the signal. Claim 15 In paragraph 13, a method for producing a PNT solution at a remote receiver, wherein the monitor station publishes a snapshot duration and a snapshot interval to allow the remote receiver to measure the TOA offset. Claim 16 In paragraph 13, a method for calculating a PNT solution at a remote receiver, wherein a set of location data regarding the said satellite is posted to the said network. Claim 17 A method for calculating a PNT solution at a remote receiver, further comprising: a step of generating Doppler observation results for the satellite in claim 13; and a step of calculating the PNT solution at the remote receiver using the Doppler observation results. Claim 18 In claim 13, the accessing step further comprises: a step of generating a snapshot FFT spectrogram by performing a Fast Fourier Transform (FFT) on the snapshot; and a step of comparing the snapshot FFT spectrogram to signal profiles in a neural network to determine the suitability of the snapshot for pseudorange calculation, a method for producing a PNT solution at a remote receiver. Claim 19 In paragraph 18, a method for producing a PNT solution at a remote receiver, wherein the neural network uses a machine learning algorithm to generate a set of signal profiles from previously collected signals. Claim 20 In paragraph 18, the neural network is a method for producing a PNT solution at a remote receiver, which is posted to the network.