A system that transmits accurate geospatial location and time using radio transmission without using satellite signals.

Abstract

A system is provided for transmitting accurate geospatial position and time using radio transmission without the use of satellite signals. The positioning and timing system uses uncorrelated standard radio broadcast signals. These radio broadcast signals are transmitted from known locations defined by latitude and longitude at assigned frequencies, respectively, and transmit modulated or unmodulated carrier signals, respectively. A reference unit at a known fixed location receives the nearby standard broadcast signal, samples the frequency and content values ​​of the signal, broadcasts the measured frequency and content data approximately simultaneously with a time mark representing the measurement time, and further broadcasts its location in latitude and longitude. A mobile unit at an unknown location to be desired receives the nearby standard broadcast signal, measures the arrival time of the broadcast, and records the time of the measurement.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims the interests of U.S. Nonprovisional Application No. 17 / 973,758, filed on 26 October 2022, which is incorporated herein by reference in its entirety below.

[0002] (Technical field) The technology disclosed herein relates to geospatial systems, and more specifically to systems and methods for accurate geospatial positioning using radio transmission without the use of satellite signals. [Background technology]

[0003] Location acquisition using the Global Positioning System (GPS) relies on accurately measuring the propagation time of signals received from multiple satellites to determine the receiver's location. Accurate GPS positioning requires precise timing. The time from atomic clocks on each satellite is encoded into radio signals, and the receiver determines how much later it was received after the signal was transmitted. Since its introduction in the 1980s, the Global Positioning System (GPS) has become increasingly used to provide accurate location and to disseminate standard time to users worldwide.

[0004] In recent years, several vulnerabilities in GPS have come to light. Not only are they susceptible to jamming and / or "spoofing," but GPS satellites are also vulnerable to recently developed technologies that can be used to destroy or disable satellites in orbit. Jamming is the process by which an adversary interferes with a user's receiver's reception of GPS signals, preventing the user from receiving location and time information. Spoofing is a more sophisticated process in which an adversary mimics GPS signals, making the user's receiver believe it is in a location desired by the adversary rather than its actual location. Timekeeping can also be affected in a similar way. There is also the constant risk of solar radiation from solar eruptions.

[0005] Despite such vulnerabilities, GPS is still in use simply because there is no alternative. GPS-based timing is essential for the control of a country's power grid, the smooth flow of information on the Internet, and the legal time-stamping of financial transactions. It is also used in transportation and research, among other things.

[0006] In the event of a breakdown or endangerment of GPS, it is estimated that the Internet will stop within minutes to hours and the country's power grid will be lost within a day. These disruptions will continue as long as the GPS outage persists.

[0007] The US government recently issued an executive order obliging it to take measures to eliminate dependence on GPS and any satellite-based timing or positioning system and to develop a fully terrestrial system for positioning and time transmission. Previous attempts have required a large bandwidth backchannel, making the system bulky and ineffective. As another attempt to eliminate dependence on GPS, there have been proposals that require one or more transmitters with known positions and a base receiver with a clock that attempts to determine the distance to the transmitters and whose position is known. Such a system obtains a series of samples of the opportunistic signal and either attaches a time tag of the reception time to the series of samples, calculates the transmission time based on the calculated distance, or both. For this system to function properly, at least two locations with known positions are required.

[0008] Conventional systems that utilize satellites, such as GPS positioning, navigation, and timing systems, and ground-based systems like the now-discontinued LORAN system, employ special-purpose transmitters. These systems rely on synchronized transmitters, and the relative phase of the signals from these transmitters or the arrival times at the (to-be-determined) positions can be calculated within the service area independently of the receiving device. Synchronization is typically achieved by methods based on the frequency, phase, and position of the transmitters. Maintaining such synchronization requires costly infrastructure both for the initial acquisition of equipment and for daily operation. Conventionally, it has been necessary to resolve the "cycle ambiguity" in signal correlation. This term refers to the fact that the period of a sine-wave carrier appears ambiguous. The ambiguity can potentially interfere with the identification of the time and phase of the carrier beyond one wavelength.

[0009] There is a need for systems and methods that do not have some of the above-mentioned drawbacks and vulnerabilities of conventional systems and that provide accurate geospatial positioning using radio transmissions without using satellite signals. SUMMARY OF THE INVENTION

[0010] The techniques of the present disclosure can be used to overcome some or all of the above limitations and drawbacks of conventional GPS technology. The techniques of the present disclosure include systems and methods for accurate geospatial positioning using radio transmissions without using satellite signals. According to an exemplary embodiment of the techniques of the present disclosure, the signals used for positioning and timing may be uncorrelated, freely available opportunistic carrier signals over frequencies across the radio spectrum. The solution of the present disclosure does not utilize sine-wave carrier measurements and is not affected by cycle ambiguity.

[0011] These and other embodiments of the Disclosure are described below in the “Modes for Carrying Out the Invention” and the accompanying drawings. Other embodiments and features of the embodiments will become apparent to those skilled in the art by examining the following descriptions of specific embodiments together with the drawings. Features of the Disclosure may be described in relation to specific embodiments and drawings, but all embodiments of the Disclosure may include one or more of the features described herein. Furthermore, one or more embodiments may be described as having a particular advantageous feature, and one or more such features may also be used in conjunction with the various embodiments described herein. Similarly, embodiments may be described below as embodiments of devices, systems, or methods, and it should be understood that such embodiments may be implemented in the various devices, systems, and methods of the Disclosure. [Brief explanation of the drawing]

[0012] The following detailed description of specific embodiments of this disclosure will be better understood when read in conjunction with the accompanying drawings. Specific embodiments are shown in the drawings to illustrate this disclosure. However, it should be understood that this disclosure is not limited to the highly precise configurations and means of the embodiments shown in the drawings.

[0013] [Figure 1] Figure 1 shows an example of the technology described herein, illustrating a system for accurate geospatial location determination using radio transmission without using satellite signals.

[0014] [Figure 2] Figure 2 is a chart comparing the measured timing error with the actual timing error that occurred when using an actual off-air signal.

[0015] [Figure 3] Figure 3 is a chart showing the difference between the actual timing error and the measured timing error.

[0016] [Figure 4]Figure 4 is a chart comparing the measured timing error with the actual timing error that occurred.

[0017] [Figure 5] Figure 5 is a chart of the location plot.

[0018] [Figure 6] Figure 6 is a map of location results using improved filtering techniques to remove poor signal quality.

[0019] [Figure 7] Figure 7 is a block diagram of an illustrative computing device relating to a specific exemplary embodiment of the technology of this disclosure.

[0020] [Figure 8] Figure 8 shows a small area on the ground including several standard radio or television broadcasting transmission towers and mobile receiver units representing the technology of the present disclosure.

[0021] [Figure 9] Figure 9 is a block diagram of a mobile receiver unit according to an exemplary embodiment of the technology of this disclosure.

[0022] [Figure 10] Figure 10 is a detailed block diagram of a mobile receiver unit relating to an exemplary embodiment of the technology of the present disclosure.

[0023] [Figure 11] Figure 11 shows the position tracking of the mobile receiver unit from the initial estimated position to the final estimated position.

[0024] [Figure 12] Figure 12 shows a small area on the ground including several standard radio or television broadcasting transmission towers and mobile receiver units representing the technology of the present disclosure, showing that a reference unit is configured to broadcast information to a nearby tower.

[0025] [Figure 13] Figure 13 shows how sound waves propagate towards two objects.

[0026] [Figure 14] Figure 14 shows the shape related to the mobile receiver unit performing measurements from two stations simultaneously, and the related process for determining the radius of the desired circle.

[0027] [Figure 15] Figure 15 shows two candidate mirror circle methods that satisfy known parameters for connecting two stations as shown in Figure 14, relating to a specific exemplary embodiment of the technology of this disclosure.

[0028] [Figure 16] Figure 16 shows a system of circles connecting two stations, as shown in Figure 14, and an intersection that defines the position of a mobile / remote receiver unit, relating to a specific exemplary embodiment of the technology of the present disclosure.

[0029] [Figure 17] Figure 17 shows the yaw, roll, and pitch of an inertial measurement unit according to a specific exemplary embodiment of the technology of this disclosure.

[0030] [Figure 18] Figure 18 shows a schematic diagram of an advanced measurement device relating to a specific exemplary embodiment of the technology of this disclosure.

[0031] [Figure 19] Figure 19 shows a schematic diagram of a practical advanced measurement according to a specific exemplary embodiment of the technology of this disclosure. [Modes for carrying out the invention]

[0032] The technology of this disclosure includes positioning, navigation, and timing systems. The system allows a mobile / remote device at an unknown location to receive broadcast signals from multiple known locations and use such information to derive the current location of the remote receiver. Specific exemplary embodiments of the technology of this disclosure may utilize uncoordinated “opportunity signals” from various transmitters operating at different frequencies to enable positioning and timing. The technology of this disclosure overcomes the limitations of the prior art by providing a system for accurate geospatial positioning using radio transmission without satellite signals. The technology of this disclosure is a novel method using existing signals to determine the location of a user device and transmit time accurately and precisely from a master clock to the user device's clock. Specific exemplary embodiments of the technology of this disclosure utilize proprietary signal comparison techniques to improve accuracy.

[0033] According to a particular exemplary embodiment of the technology of the present disclosure, the positioning and timing system disclosed herein may use an uncorrelated standard radio broadcast signal. The radio broadcast signal may be transmitted from a known location defined by latitude and longitude at an assigned frequency, and transmit a modulated or unmodulated carrier signal, respectively. A reference unit at a known fixed location may receive a nearby standard broadcast signal and sample the frequency and content values ​​of the signal. The reference unit may then broadcast the measured frequency and content data, along with a time mark representing the time of measurement, almost simultaneously. The reference unit may further broadcast its location by latitude and longitude.

[0034] A mobile / remote unit at an unknown location (to be desired) may receive a standard broadcast signal (in the vicinity of the mobile / remote unit), measure the arrival time of the broadcast, and record the time of measurement. The mobile / remote unit may also receive broadcasts from a reference unit. In a particular exemplary embodiment, the mobile / remote unit may calculate its current position relative to the reference unit's position using an internal database of broadcast transmitter locations, data broadcast by the reference unit, and digital content values ​​measured by the mobile / remote unit that have been time-adjusted to match the measurement time by the reference unit. Position measurement relative to the reference unit's position may be performed entirely within the mobile / remote unit without the use of external processing means, and is referred to herein as “initial positioning.” Once the position is determined by initial positioning, the mobile unit enters “tracking mode,” which periodically measures the time delay of digital signals and calculates its current position and velocity by comparing the current signal sample with signal samples measured in previous measurements. During tracking mode, the initial positioning calculation is performed in the mobile unit as a background process. The results of tracking are compared with the results of the initial positioning calculation. When the accumulated tracking mode error exceeds a specified deviation from the initial positioning mode value, the tracking mode result is updated to the current initial positioning value. The reference device, including a rubidium clock, maintains accurate time over long periods and is periodically synchronized to a standard NIST clock. The remote device, including a low-cost oven-controlled clock, is continuously disciplined by the reference device to maintain accurate time synchronization. Furthermore, both the reference and remote devices analyze digital samples in increments of 100 ns or less, providing accurate time transmission from the reference device to the remote device.

[0035] According to a particular exemplary embodiment of the technology of this disclosure, reference signal data may be formatted in a proprietary manner to include all information relating to the transmitter and reference position. In a particular exemplary embodiment, the reference data may be transmitted by the AM transmitter itself. In a particular exemplary embodiment of the technology of this disclosure, hyperbolic navigation on a sphere or oblate sphere may be utilized. The technology of this disclosure can be used to relay time information without using the internet, satellite signals, or cellular networks.

[0036] The technology disclosed herein may offer technical improvements and / or advantages, such as providing a ground alternative to GPS for time transmission and positioning, leveraging existing infrastructure, and / or requiring minimal investment in key stations in each region.

[0037] The general objective of the technology of this disclosure is to provide improved techniques for positioning, navigation, and timing using radio broadcast signals. Disclosing improved positioning and timing techniques using radio signals received from multiple transmitters, each having uncorrelated broadcast data in frequency, phase, and time. The technology of this disclosure provides improved positioning and timing techniques using radio signals transmitted from uncorrelated transmitters. Specific exemplary embodiments of the technology of this disclosure may be used to provide positioning, navigation, and / or timing services in indoor or urban canyons where satellite-based systems are malfunctioning or not functioning at all. Specific exemplary embodiments of the technology of this disclosure may be used to provide the potential for global coverage to function as a potential backup for satellite-based systems, providing highly reliable services with minimal vulnerability to jamming, interference, and spoofing. Specific exemplary embodiments of the technology of this disclosure may be used to provide highly accurate time transmission based on ground signals to prevent disruption to the U.S. energy grid, communication networks, and financial systems.

[0038] The art of this disclosure includes a method for determining an unknown location using radio signals from multiple transmitters located at known locations and transmitting over a wide range of radio frequencies. The method may include comparing samples of radio signals that arrive simultaneously at a known reference location and calculating the distances to those transmission points to obtain a first comparison sample set. A second sample set may be obtained by measuring samples of radio signals that arrive simultaneously at the unknown location approximately simultaneously with their arrival at the known location. According to an exemplary embodiment of the art of this disclosure, the first and second sample sets may be compared and analyzed to determine the unknown location.

[0039] In a particular exemplary embodiment, radio signals may operate uncorrelatedly and independently, reaching known and unknown locations from multiple transmitters, each transmitting at a different carrier frequency. In a particular exemplary embodiment, “first dataset” refers to a first instance in which signals simultaneously reach known locations, and “second dataset” refers to a second instance in which signals simultaneously reach unknown locations. The time difference between the first and second instances can be minimized by synchronizing the first and second measurements using time marks available at both locations approximately simultaneously.

[0040] The technology of this disclosure can provide a robust level of security in any area using a wide range of signal options and can provide resistance to two recently discovered weaknesses of GPS: spoofing and jamming. In certain exemplary embodiments, the system of this disclosure can be started without prior knowledge of its location and without operator input. Certain exemplary embodiments of the technology of this disclosure can support the timing requirements of power grids and financial transactions completely independently of the internet, satellite signals, and cellular networks. In the event of a national emergency that causes or is caused by a disruption of GPS timing and positioning, the embodiments disclosed herein can provide a fully ground-based backup or alternative. Certain exemplary embodiments of the technology of this disclosure can function on mobile platforms as well as in fixed-location operation. Certain exemplary embodiments of the technology of this disclosure can be used to meet obligations and anticipated laws requiring critical infrastructure, such as power grids, to use GPS-independent systems for time transmission.

[0041] The technology disclosed herein utilizes the relationship between time and position. To illustrate this relationship, consider a scenario in which an observer witnesses lightning striking a radio tower. The flash of lightning is visible almost instantaneously, but the sound of thunder may not reach the observer for several seconds. Using the speed of sound, the distance from the observer to the radio tower can be calculated. For illustrative purposes, consider a scenario in which the radio tower is calculated to be 0.6 miles from the observer. Using a map of the area, draw a circle with a radius of 0.6 miles (no scale) centered on the radio tower, and the observer will be located somewhere on that circle. If the observer can see lightning striking another tower, the distance from the observer to the other tower can be calculated using a similar process, and corresponding circles of the corresponding radii can be drawn around the other towers. The observer's position corresponds to the point where all the circles intersect. This demonstrates a method for determining the observer's position using the speed of sound and the known positions of multiple radio towers.

[0042] As another example for explanation, consider a scenario where Person 1 is a short distance away from Person 2. Person 1 has a very accurate watch, while Person 2 has an inaccurate and slow watch. Both Person 1 and Person 2 can see lightning strike the radio tower at roughly the same time (ignoring the delay in the movement of light). Person 2 calls Person 1 and asks what time it was on their watch when the lightning struck, and receives the answer 1:45:10 p.m. However, Person 2 has recorded that the lightning flashed at 1:44:55 p.m. From this information, Person 2 can deduce that their wristwatch is 15 seconds slow. This is a simple explanation of time transmission.

[0043] The term “time transmission” as disclosed herein may refer to the process of determining the epoch error of a second clock based on a known epoch time in a reference clock. The second clock may then be corrected to have the same epoch time as the reference clock. This determination may take into account the distance between the two clocks and the fact that signals between the clocks cannot travel faster than the speed of light.

[0044] Specific exemplary embodiments of the technology of the present disclosure may utilize a form of time transmission to synchronize associated clocks. Specific exemplary embodiments of the technology of the present disclosure may utilize a form of relationship between time and position to determine the position of a mobile / remote device.

[0045] Next, methods and devices for carrying out embodiments of various features of the technology of this disclosure will be described with reference to the drawings. The drawings and related descriptions are provided to illustrate embodiments of the technology of this disclosure and do not limit the scope of the technology of this disclosure. References to “one embodiment” or “an embodiment” in this specification are intended to indicate that a particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the technology disclosed. The expressions “in one embodiment” or “an embodiment” appear in various places in this specification, but not all of them necessarily refer to the same embodiment.

[0046] Various embodiments provide systems for transmitting accurate geospatial location and time using radio transmission without the use of satellite signals. One embodiment of the technology of this disclosure provides a system for transmitting accurate geospatial location and time using radio transmission without the use of satellite signals. Another embodiment provides a method for using the system. This system and method are disclosed in detail.

[0047] Figure 1 shows a system 100 for accurate geospatial position and time transmission using radio transmission without satellite signals, according to one embodiment of the technology of the present disclosure. System 100 includes three or more AM transmitters 102 that can include high-definition (HD) channels. System 100 includes one or more reference stations 104, each having a stable clock 106. System includes one or more mobile / remote receivers 108, each having a stable clock. System may communicate with a national time (such as the U.S. National Institute of Standards and Technology) to receive accurate time.

[0048] According to a particular exemplary embodiment of the technology of this disclosure, each geographic area with a radius of approximately 150 miles may have a reference station 104 that receives AM spectrum from three or more AM transmitters 102 and can sample and store “snapshots,” for example, short records of the relevant signal waveforms. The snapshots may be formatted into data blocks and time-stamped based on the clock 106 of the reference station 104. The reference receiver may transmit this data block to a synchronous transmitter 114 via a dedicated link 112, such as microwave or optical. In a particular exemplary embodiment, the synchronous transmitter 114 may broadcast the data block on its HD channel.

[0049] According to a particular exemplary embodiment of the technology of the present disclosure, an unlimited number of mobile / remote receivers 108 may be configured to receive timestamped data blocks on an HD channel. Each mobile / remote receiver 108 may also take a corresponding snapshot of the AM spectrum around the same time that a reference station 104 took a spectral snapshot. Each mobile / remote receiver 108 may use the reference data block to compare the relative arrival times between signals from each of the same three or more transmitters 102. The reference data block may also include the exact positions of all AM transmitters 102 and the position of the reference station 104. Each mobile / remote receiver 108 may use this position information, along with the difference in arrival times determined by the signal comparison, to determine the position of the remote station 104 and the timing error of the remote station clock 106. The remote station 104 may correct or discipline its clock 106 and present its time and position to the mobile / remote receiver 108.

[0050] According to a particular exemplary embodiment of the technology of the present disclosure, the reference station 104 may also transmit time between itself and other stations in the same manner that time is transmitted from the reference station 104 to the mobile / remote receiver 108, thereby forming a network that covers a wide area (such as the entire continental United States) and can transmit time from, for example, a national standard clock 110.

[0051] According to a particular exemplary embodiment, system 100 may use signals transmitted 24 hours a day from transmitter 102. These signals can be continuously transmitted in all directions from the tower of transmitter 102 at the speed of light, which is known with great precision. However, the exact time when these signals are transmitted is unknown. In other words, the exact time when an announcer at a particular broadcasting station says a particular word during a traffic report is unknown. Similar to the lightning example above for illustrative purposes, we do not know when lightning will strike the radio tower, but the flashing of light provides information about when lightning struck the radio tower.

[0052] According to exemplary embodiments of the technology of this disclosure, a reference station 104 may be located at a highly precise known location. The reference station 104 may also have a highly precise clock 106. In exemplary embodiments, once per second, in seconds, the reference station 104 may take an electronic snapshot of all or part of the AM radio spectrum and record what each transmitter 102 is transmitting. The reference station 104 may format this information into a data block. The reference data has a timestamp indicating the date and highly precise time the snapshot was taken. This data block may be transmitted to one of the AM transmitters in an area contracted with the company that owns the reference station 104. The data block may be transmitted on a special channel, commonly called an HD channel, which utilizes bandwidth between channels.

[0053] In a typical scenario, if a user wants to know their current location, they might use the remote receiver 108 for this purpose. The remote receiver 108 may also contain a clock that attempts to set to an accurate time, though it may not be as precise as the other clocks 106 and 110. As mentioned above, the remote receiver 108 may also take snapshots of the AM spectrum once per second, in seconds. However, because the clock of the remote receiver 108 may be inaccurate, the snapshots may be slightly earlier or later than those taken by the reference station 104. The remote receiver 108 may be listening on an HD channel with a reference data block. Based on the information in the data block, the remote receiver 108 may determine approximately what time it is. The term "approximately" is used because it takes a certain amount of time for the signal to travel from the reference station 104 to the synchronous transmitter 114 and from the radio transmitter 102 to the remote receiver 108. To determine this time and the position of the remote receiver 108, the remote receiver 108 may compare two snapshots: one it has taken and one sent by the reference station 104. Based on a comparison of the two snapshots, the remote receiver 108 can determine its relative position to the transmitter 102 and the reference station 104, as will be further described below.

[0054] As will be described in detail below, certain embodiments of the technology of this disclosure may utilize overlapping circles to determine the position of the remote receiver 108. By knowing the position of the reference station 104 and the position of the transmitter 102, the remote receiver 108 may utilize a circle (or hyperbola) based on the associated delays. Such a curve represents a point where the time difference between the arrival information from the transmitter 102 is the same, and the remote receiver 108 lies somewhere on that line. According to a particular exemplary embodiment of the technology of this disclosure, the remote receiver 108 may calculate curves from different pairs of transmitters 102, and the point where they intersect is the (still potentially ambiguous) position of the remote receiver 108. The remote receiver 108 may determine the time at which individual signals arrived and how much time the clock of the remote receiver 108 is off from the clock 106 of the reference station 104.

[0055] The remote receiver 108 can know its current location and how far off its own clock is. According to a particular exemplary embodiment of the technology of the present disclosure, the remote receiver 108 can set its own clock to a high precision of less than one-tenth of a microsecond and present this time and location to the user.

[0056] According to a particular exemplary embodiment of the technology of this disclosure, the above calculation can be performed instantaneously, and the entire process can be repeated after one second. If the remote receiver 108 is moving, the remote receiver 108 can know its position and direction of movement. If the remote receiver 108 is mounted on a vehicle that has traveled a sufficiently long distance, it may move outside the circular area of ​​approximately 150 miles radius that the reference station 104 can cover. In this scenario, the remote receiver can automatically switch to the next reference station in the new area and continue navigation and timing.

[0057] System 100 has another advantage. Just as it transmits time from base station 104 to remote receiver 108, it can also transmit time from base station 104 to base station 105. In this way, time can be transmitted nationwide from the U.S. Atomic Clock Standards Station 110 in Boulder, Colorado. Even if the internet and cell phone networks go down, this system will continue to function and will be useful in bringing them back online in the event of a national emergency.

[0058] Figure 2 is a chart comparing the measured timing error with the actual timing error that occurred. This chart compares the measured timing error with the actual timing error that occurred in a test conducted in January 2020 using an actual off-air signal. The horizontal axis shows the error that occurred between the reference station and the remote station. The vertical axis shows the measured error. The upper and lower limits are ±1 μs, which are the upper and lower limits of the NIST timing requirements.

[0059] Figure 3 is a chart showing the difference between the actual timing error and the measured timing error for a collocation time transmission test using an actual off-air signal conducted in January 2020. The bias offset of the residual error is presumed to be due to an additional time offset between the sampling clocks of the reference SDR receiver and the remote SDR receiver. This offset may be corrected based on this measurement in the actual implementation of the system, or it may be eliminated by improving the synchronization between the master clock and the sampling clock in both the reference and remote receivers.

[0060] Figure 4 is a chart comparing the measured timing error with the actual timing error that occurred. This chart shows a comparison of the measured timing error with the actual timing error that occurred in a test conducted in January 2020 using an actual off-air signal, simulating a distance of 1 mile northwest between the remote unit and the reference unit.

[0061] Figure 5 is a chart of a location plot using the technology of this disclosure. The scatter plot of data point 502 corresponds to the rooftop of the building where the test antenna is installed at 34.21174, -118.528045. Data point 502 is the raw location solution, without averaging or denoising. These location data have an error of 17.6m with a 95% probability circle error (CEP) and an offset of 9.9m north-northeast (NNE). These errors can be significantly reduced by simple averaging of the locations and / or by denoising techniques applied to the received signal.

[0062] Figure 6 is a map of position 602 similar to that shown in Figure 5, but these results show a denser scatter plot due to the use of improved filtering techniques to remove poor signal quality.

[0063] Figure 7 shows a block diagram of a computing device 700 for illustrative purposes, relating to an exemplary embodiment. A particular aspect of Figure 7 may be embodied in a receiver. According to one exemplary embodiment, the term “computing device” as used herein may refer to a CPU, or a conceptualized form of a CPU (e.g., CPU 702 in Figure 7). In this exemplary embodiment, the computing device (CPU) may be coupled, connected, and / or communicate with one or more peripheral devices, such as a display. In a particular embodiment, the computing device 700 may be included in a mobile / remote unit and / or a reference receiver / transmitter. In another exemplary embodiment, the term “computing device” as used herein may refer to a processor and associated components in or related to a system of the disclosure.

[0064] In exemplary embodiments, the computing device may output content to its local display and may send and receive messages via the antenna interface 710, network connection interface 712, telephone subsystem 732, etc. In exemplary embodiments, the computing device may output content to an external display device such as a television or external computing system (for example, via Wi-Fi). It will be understood that the computing device 700 is provided for illustrative purposes only and does not limit the scope of various embodiments of the communication system and method.

[0065] The computing device 700 in Figure 7 includes a central processing unit (CPU) 702 on which computer instructions are processed. In a particular exemplary embodiment, a display interface 704 may be included, which functions as a communication interface and provides capabilities for drawing video, graphics, images, and text onto a display. In a particular exemplary embodiment of the technology of this disclosure, the display interface 704 may be directly connected to a local display, such as a touchscreen display associated with the mobile computing device. In another exemplary embodiment, the display interface 704 may be configured to provide content (e.g., data, images, and other information as described above) to an external / remote display that is not necessarily physically connected to the computing device 700. For example, a desktop monitor may be used to mirror graphics and other information to be presented on the mobile computing device. In a particular exemplary embodiment, the display interface 704 may wirelessly communicate to the external / remote display, for example, via a Wi-Fi channel or other available network connectivity interface 712.

[0066] In an exemplary embodiment, the network connection interface 712 may be configured as a communication interface and may provide functionality for drawing video, graphics, images, text, other information, or any combination thereof on a display. In one embodiment, the computing device 700 may include a communication interface which may include one or more of the following: a serial port, a parallel port, a general-purpose input / output (GPIO) port, a game port, a universal serial bus (USB), a micro USB port, a high-definition multimedia (HDMI) port, a video port, an audio port, a Bluetooth port, a near-field communication (NFC) port, another similar communication interface, or any combination thereof.

[0067] According to an exemplary embodiment of the technology of this disclosure, the computing device 700 may include a keyboard interface 706 that provides a communication interface to a keyboard. In one exemplary embodiment, the computing device 700 may include a pointing device interface 708 for connecting to a presence-intuitive input interface. According to a specific exemplary embodiment of the technology of this disclosure, the pointing device interface 708 may provide a communication interface to various devices such as a touchscreen or a depth camera.

[0068] The computing device 700 may be configured to allow a user to input information into the computing device 700 using an input device via one or more input / output interfaces (e.g., a keyboard interface 706, a display interface 704, a pointing device interface 708, an antenna interface 710, a network connection interface 712, a camera interface 714, a sound interface 716, etc.). Input devices may include a mouse, trackball, directional pad, trackpad, touch-sensitive trackpad, presence-aware trackpad, presence-aware display, scroll wheel, digital camera, digital video camera, webcam, microphone, sensor, smart card, etc. Furthermore, the input device may be integrated with the computing device 700 or be a separate device. For example, the input device may be an accelerometer, geomagnetometer, digital camera, microphone, or optical sensor.

[0069] A particular exemplary embodiment of the computing device 700 may include an antenna interface 710 for communicating with an antenna. A particular exemplary embodiment of the antenna interface 710 may include one or more of a receiver, an analog-to-digital converter, a sampler, a buffer, memory, and memory. A particular exemplary embodiment may include a network connection interface 712 that provides a communication interface to a network. In a particular embodiment, a camera interface 714 may function as a communication interface that provides functionality for capturing digital images from a camera. In a particular embodiment, a sound interface 716 is provided as a communication interface for converting sound into electrical signals using a microphone and converting electrical signals into sound using a speaker. According to an exemplary embodiment, a random access memory (RAM) 718 is provided for processing by the CPU 702, in which computer instructions and data can be stored in a volatile memory device.

[0070] According to an exemplary embodiment, the computing device 700 includes read-only memory (ROM) 720 in which immutable, low-level system code or data for basic system functions such as basic input / output (I / O), startup, or receiving keystrokes from a keyboard is stored in a non-volatile memory device. According to an exemplary embodiment, the computing device 700 includes a storage medium 722 or other suitable type of memory (e.g., RAM, ROM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk, optical disk, floppy disk, hard disk, removable cartridge, flash drive, etc.) in which files including an operating system 724, an application program 726, and content files 728 are stored. According to a particular exemplary embodiment of the technology of this disclosure, the application program 726 may include one or more programs such as correlation, accumulation, identification, expansion and multiplication, division, addition, and low-pass.

[0071] According to an exemplary embodiment, the computing device 700 includes a power supply 730 that provides appropriate alternating current (AC) or direct current (DC) to power its components. According to an exemplary embodiment, the computing device 700 may include a telephone subsystem 732 that enables the device 700 to send and receive sound over a telephone network. The component devices and the CPU 702 communicate with each other via a bus 734.

[0072] According to an exemplary embodiment, the CPU 702 has a structure suitable for being a computer processor. In one configuration, the computer CPU 702 may include multiple processing units. The RAM 718 interfaces with the computer bus 734 to provide the CPU 702 with rapid RAM storage during the execution of software programs such as operating system application programs and device drivers. More specifically, the CPU 702 loads computer-executable processing steps from the storage medium 722 or other medium into the fields of the RAM 718 in order to execute the software program. The content may be stored in the RAM 718, which the computer CPU 702 can access during execution. In an exemplary configuration, the device 700 includes at least 128 MB of RAM and 256 MB of flash memory.

[0073] The storage medium 722 itself may include a number of physical drive units such as a redundant array of independent disks (RAID), floppy disk drives, flash memory, USB flash drives, external hard disk drives, thumb drives, pen drives, key drives, high-density digital versatile disk (HD-DVD) optical disk drives, internal hard disk drives, Blu-ray optical disk drives, holographic digital data storage (HDDS) optical disk drives, external mini dual in-line memory modules (DIMMs) synchronous dynamic random access memory (SDRAM), or external microDIMM SDRAM. Such computer-readable storage media allow device 700 to access computer-executable processes or application programs stored on removable or non-removable storage media, offload data from device 700, or upload data to device 700. Computer program products, such as those utilizing communication systems, may be embodied in the storage medium 722, which may consist of machine-readable storage media.

[0074] In one exemplary embodiment, the term “computing device or mobile computing device” as used herein may be a central processing unit (CPU), controller, or processor, or a conceptualized representation of a CPU, controller, or processor (e.g., CPU processor 702 in Figure 7). In yet another example, the computing device may be a CPU, controller, or processor combined with one or more additional hardware components. In a particular exemplary embodiment, the computing device acting as a CPU, controller, or processor may be operably coupled with one or more peripheral devices such as a display, navigation system, stereo, entertainment center, or Wi-Fi access point. In another exemplary embodiment, the term “computing device” as used herein may refer to a mobile computing device such as a smartphone, mobile station (MS), terminal, cell phone, mobile terminal, personal digital assistant (PDA), wireless telephone, organizer, portable computer, desktop computer, notebook computer, tablet computer, set-top box, television, consumer electronics, game console, medical device, display device, satellite processor, or other similar device. In an exemplary embodiment, the computing device may output content to its local display or speaker. In another exemplary embodiment, the computing device may output content to an external computing system.

[0075] Figure 8 shows a small area on the ground including several standard radio or television broadcast transmitters 802 and remote receivers 808 relating to the technology of this disclosure. Transmitters 802 may correspond to transmitters 102 shown and described with reference to Figure 1. Similarly, mobile receivers 808 may correspond to remote receivers 108 shown and described with reference to Figure 1.

[0076] Transmitters 802 are located at various known fixed locations within the area. In a particular exemplary embodiment, a transmitting tower 802 may broadcast amplitude-modulated (AM) signals and may operate in the medium-wave broadcasting band with frequencies from approximately 530 kHz to approximately 1700 kHz. Each transmitter 802 may be assigned its own fixed-frequency carrier wave. The carrier wave may be present in the broadcast signal as a spectral component of a continuous wave. On either side of the carrier wave in the frequency domain are sidebands resulting from amplitude modulation. In the United States, carrier frequencies are assigned by the Federal Communications Commission (FCC) and are constrained to be integer multiples of 10 kHz. Sidebands are limited to approximately ±5 kHz relative to the carrier frequency. In some other countries, carrier frequencies are assigned at 9 kHz intervals, and the bandwidth occupied by sidebands may be narrower. Generally, transmitters within an area are assigned to non-overlapping frequencies to avoid interference. In some embodiments of the technology of this disclosure, frequency-modulated (FM) broadcasting transmitters operating in the ultra-high frequency band of 30 MHz to 300 MHz may be utilized.

[0077] According to a particular exemplary embodiment of the technology of this disclosure, transmitter 802 may drive an antenna perpendicular to the ground. The reception area of ​​its signal is typically within tens of kilometers from transmitter 802. Within this area, the signal propagates with vertical polarization, primarily in “terrestrial” mode. The “airborne” signal component reflected by the ionosphere may be negligible within this area. The terrestrial signal propagates horizontally radially outward from each antenna. The wavefront of the carrier component of each signal is essentially circular, centered on the transmitting antenna. The wavelength of the transmitted signal (or the horizontal distance between wavefronts with a phase difference of one period) is approximately equal to the speed of light in a vacuum, approximately 3 × 10⁸ m / s, divided by the respective carrier frequency (Hz). High-precision wavelengths depend on electromagnetic properties (primarily conductivity and dielectric constant) as well as the thickness of the subsurface layer. Formulas and procedures for calculating terrestrial wavelengths are readily available in technical literature on radio propagation.

[0078] For most practical purposes, using wavelengths in a vacuum is sufficient for relatively flat terrain over distances of a few kilometers. More accurate values ​​of ground wavelengths can be determined by traversing the area, simultaneously measuring the phase and position of ground waves, and independently determining the position. Such precise positional information may be used, especially in mountainous or hilly areas, where vertical displacement may be present in the broadcast signal path and needs to be distinguished from horizontal displacement for positional purposes.

[0079] The fixed reference station 804 may correspond to reference station 104 shown in and described with reference to Figure 1. In a particular exemplary embodiment, the location of the fixed reference station 804 is known. The location of the mobile receiver 808 is unknown and may be a location of interest. The mobile receiver 808 is shown as a vehicle, but may be mounted on an object or person whose location is to be known. As previously described, the location of the mobile receiver 808 may be determined by calculation of data from corrected arrival time measurements of broadcast signals from the fixed broadcast station 802 and reference station 804 disclosed herein.

[0080] According to an embodiment that exemplifies the technology of the present disclosure, a reference station 804 may receive broadcast signal components from a plurality of transmitters 802 and sample and digitize broadcast samples almost simultaneously. A database of the measured positions of the transmitters 802 and the reference station 804 may be used to calculate the distance to the relevant transmission point. This information may be transmitted to a mobile receiver 808. Simultaneously, the mobile receiver 808 may measure its own dataset from at least three of the transmitters 802. The time difference between a first set and a second set of observed broadcast samples may be minimized, for example, by synchronizing the first and second sets with time marks generated and broadcast by the reference station 804.

[0081] According to a particular exemplary embodiment of the technology of this disclosure, the reference data (distance from reference station 804 to transmitter 802) may be telemetred from reference station 804 to mobile receiver 808. In a particular exemplary embodiment, the data may also be transmitted via a data connection to a broadcast transmitter 804, where it may be multiplexed with a broadcast signal and received by mobile receiver 808. Methods for multiplexing data with a broadcast signal without causing perceptible interference to the primary modulation are well known to those skilled in the art with industry experience. If reference station 804 is close to transmitter 802, the data connection may be short. For longer data connections, data network infrastructure may be utilized. Other data telemetry transmission techniques are also possible, including, but not limited to, the use of cellular radio or other wireless data transmission techniques.

[0082] In a particular exemplary embodiment, the base station 804 may include a vertical antenna adapted to receive terrestrial signals from the transmitter 802. The mobile receiver 808 may also include a vertical antenna adapted to receive terrestrial signals from the transmitter 802, which may include any multiplexed data from the base station 804 applied to the broadcast signal as described above.

[0083] In a particular exemplary embodiment, transmitter 802 may be positioned in a wide range of directions relative to the mobile receiver 808. However, it is not important that the transmitters are uniformly spaced apart, uniformly radially spaced apart, or that their frequencies are distributed in a particular manner. Generally, if medium-wave broadcasting stations are distributed across the United States, this is sufficient for the purposes of the disclosed technology. Very high frequencies may be used primarily for outdoor use, as backup, or to increase the number of high-quality signals.

[0084] A further advantage of using the medium-wave broadcast signals described herein is that in many countries, including the United States, they are transmitted at high power levels of 50,000 watts or more.

[0085] According to a specific exemplary embodiment of the technology of this disclosure, the carrier component of the transmission from transmitter 802 may be picked up by a receiver with a very narrow bandwidth, and the received signal-to-noise density may be extremely high, thus benefiting the reception range. In addition, low broadcast signal frequencies may be relatively less susceptible to attenuation and reflections that often occur in urban areas.

[0086] AM broadcasting stations often have antennas consisting of two or more towers that act as components of a directional array antenna. That is, each tower of the array is excited at the same frequency but at different amplitudes and phases so as to form a radiated beam or not radiate in a particular direction. For the purposes of the art of this disclosure, when the receiving site is far away, these multiple towers may be represented as a single antenna at the phase center of the array.

[0087] Figure 9 is a block diagram of a mobile receiver unit 900 relating to an exemplary embodiment of the technology of the present disclosure. In a particular exemplary embodiment, components may be located in both a base station (such as base station 804 in Figure 8) and a mobile receiver (such as mobile receiver 808 in Figure 8). In a particular exemplary embodiment, the components of the mobile receiver unit 900 at these sites may be identical except for two items, as will be described later.

[0088] Antenna 2-1 can simultaneously receive analog broadcast signals in the range of approximately 530 kHz to 1700 kHz. As shown in the figure, the signal from the antenna can be transmitted to receiver 2-2. In some embodiments, receiver 2-2 may include an analog-to-digital converter (ADC). In such embodiments, the receiver may (a) digitize the analog input spectrum from the antenna, (b) further process the signal (such processing will be further described throughout this disclosure), and (c) route the processed signal to location processor 2-3. In some embodiments, the system may digitize the input signal with a 16-bit resolution. It will be understood that the resolution is selected considering speed versus accuracy. Furthermore, in some embodiments, the receiver may demultiplex data transmitted from a reference unit and carried over low-frequency or medium-frequency broadcast signals or alternative communication media such as mobile communications.

[0089] As further shown in the figure, the location processor 2-3 can receive the processed signals. The location processor 2-3 can then perform a position calculation based on the arrival times of multiple input signals and reference unit data (if applicable) and drive an optional user interface 2-4 that displays the determined position result. The user interface 2-4 may include a keyboard or similar data input device, which allows the user to input commands to the moving unit.

[0090] Figure 10 is a block diagram of a mobile receiver unit 1000 according to an exemplary embodiment of the technology of the present disclosure. In a particular exemplary embodiment, components may be located in both a base station (such as base station 804 in Figure 8) and a mobile receiver (such as mobile receiver 808 in Figure 8).

[0091] As shown in the figure, the antenna is connected to a dedicated chain of receiving components configured to process the received signal. For example, the antenna simultaneously receives broadcast signals from all of several broadcast transmitters (labeled transmitter 802 in Figure 8). As shown in the figure, the signal is then sent to the analog-to-digital converter 3-1. The analog-to-digital converter 3-1 samples the input analog spectrum and can output a digital signal that can be further processed by the system. For example, in some embodiments, the analog-to-digital converter 3-1 uses a 16-bit analog-to-digital converter to sample the input analog spectrum centered at a nominal 1.105 MHz and outputs composite sampled data at a rate of approximately 20 MS / s.

[0092] As further shown in the figure, the digital signal is then sent to downsampler 3-2. Downsampler 3-2 downsamples the above composite data and reformats it to a standard data format. For example, in one case, downsampler 3-2 can sample the data and reformatize it to a data rate of approximately 1.2 MS / s in IQ (In-Mode Quadrature) format. This rate will be understood to represent a medium wave spectrum centered at 1,105 kHz ± 600 kHz, including channelization center frequencies of 510 kHz, ..., 520 kHz, ..., 1700 kHz, in accordance with the bandwidth plan approved by the U.S. Federal Communications Commission.

[0093] While many of these subbands are occupied in any area of ​​the United States, it should be understood that only the largest metropolitan areas have all of them occupied. Because the US medium wave broadcast band is channeled around 10 kHz, it is possible that two broadcasts in any area could be received at 10 kHz or 20 kHz intervals and fall into the same subband. However, this rarely happens because the FCC's frequency allocation procedures take care to minimize adjacent channel interference. If interference occurs within a subband and degrades the signal, the interference can be detected and that subband can be automatically removed from service.

[0094] The channel selector module 3-3 demultiplexes the sampled signal into parallel data streams, enabling processing of multiple streams. For example, the channel selector module 3-3 demultiplexes a sampled signal exceeding a composite data stream of 1.2 MS / s into 60 parallel data stream outputs, each occupying a bandwidth of ±10 kHz. In some embodiments, the 60 parallel channels can represent medium-wave broadcast subbands of 505-525 kHz, ..., 525-545, ..., and 1685-1705 kHz.

[0095] In some embodiments, the channel selector module 3-3 can be configured to route any 24 of the 60 parallel data streams to any 24 individual output paths connected to the signal analysis loop module 3-4. For example, the output paths may be connected to 20 signal samples 3-4 and optionally 4 data demodulators (not shown) when the system receives multiplexed reference unit data. Furthermore, a system manager 3-5, shown as a software-defined receiver and capable of receiving instructions from an internal real-time microprocessor, can provide instructions for routing the data streams.

[0096] Each broadcast 3-4 allows for the recording of signal samples and the measurement of instantaneous broadcast timestamps. The ADC module 3-1 converts the broadcast signals to a digital format with 16-bit resolution, so the signals can be measured at the same resolution. Generally, in most areas of the United States, at least 20 medium-wave broadcast signals are in continuous operation. By selecting these and applying them individually in parallel to signal sampling 3-4, data can be compared simultaneously.

[0097] In some embodiments, a data demodulator can receive multiplexed data streams transmitted by the reference station 804 in Figure 8 via a reconfigurable selector 3-3. Some of the reference stations 804 may be located in overlapping broadcast coverage areas. In some embodiments, up to four data streams can be received simultaneously. In such embodiments, it will be understood that a mobile unit can move between coverage areas while maintaining uninterrupted reception of the reference unit signal.

[0098] The real-time microprocessor of System Manager 3-5 can be configured to operate in two modes: acquisition (i.e., initial location) mode and tracking mode. Each mode will be described later.

[0099] When powered on, modules 3-5 can be configured to "start up" and perform the initial "initial localization," or coarse positioning, by scanning the local broadcast band and comparing the active frequencies with the onboard almanac of published and surveyed broadcast towers. In some embodiments, if multiple signals are detected, the system can be configured to select the strongest signal. Once a signal is selected, the geographic coordinates of the registered broadcast tower's location are obtained by a database search. In some embodiments, the system can be configured to perform "initial localization" using alternative methods based on cellular data used. For example, the system can be configured to use a cellular radio to find the nearest cell tower, obtain its tower ID, and retrieve its location coordinates from the aforementioned onboard database.

[0100] Furthermore, in some embodiments, the system can be configured to transmit over a back channel in the AM band. In such embodiments, the receiver can be configured to scan the AM band for a specified channel. Once a channel is found, the receiver can be configured to receive position data.

[0101] Modules 3-5 can be configured to transition the acquisition mode to a background process and initialize the tracking mode as a foreground process once the coarse position determination process is complete. During the initialization of the tracking mode, the signal sampling loop 3-4 acquires the current signal of up to 20 broadcast signal samples and records them as initialization signals. Subsequently, incremental changes in the signal samples are measured at configurable time intervals, and the corresponding change in position at each interval is calculated. In some embodiments, the system can also be configured to determine the displacement between the current position and the previous position at selected time intervals, and to generate velocity and direction of travel.

[0102] The system can be further configured to monitor noise and signal intensity from each of the 3-4 signal samples to estimate signal quality during tracking mode. The determined signal-to-noise ratio can be used as a measure of the quality of the broadcast signal for signal sampling purposes. In some embodiments, modules 3-5 can be configured to roughly rank the broadcast signals selected by modules 3-3 based on such signal quality metrics. In such embodiments, the system can be further configured to perform signal sampling measurements only for broadcast signals that meet the minimum requirements for signal quality.

[0103] Modules 3-5 operate in much the same way for both the reference station 804 and the mobile unit 808. When operating as part of the reference unit 804, module 3-5 is the source of telemetry transmission data, which is optionally multiplexed into the broadcast signal and received by the mobile unit 1-2. As previously mentioned, the reference station's telemetry transmission data consists of the calculated arrival time of the signal sample at its transmission point, the measured signal travel distance, the time reference synchronization mark, and the position of the reference station itself. Furthermore, in some embodiments, the reference station data may include a snapshot of the captured spectrum, the time of the snapshot, a continuous almanac of the reference station's position, the transmitter's position, and their measured frequencies.

[0104] As further shown in the figure, modules 3-6 are optionally connected to a user display screen and a user input keyboard so that the user can configure the operation of the present invention as needed and view the calculation results of position, velocity, and bearing performed by module 3-5.

[0105] Figure 12 shows a small area on the ground including System 1200 as an example further described herein. As shown in the figure, the system includes a number of standard radio or television broadcast transmitters 1-1, a reference station / unit 1-2, and a remote receiver / unit 1-4, all relating to the art of this disclosure. Transmitter 1-1 may correspond to transmitters 102 and 804 shown and described with reference to Figures 1 and 8. Similarly, reference station 1-2 may correspond to reference stations 102 and 804 shown and described with reference to Figures 1 and 8, and mobile receiver 1-4 may correspond to remote receivers 108 and 808 shown and described with reference to Figures 1 and 8.

[0106] In some embodiments, a snapshot of the signal in the spectrum received by remote units 1-4 is compared with signal information provided by reference station 1-2 using one of the methods described herein. The entire sampled signal content from each station (e.g., 1-2) is used for the comparison, and the accuracy of the comparison may be improved by an interpolation algorithm. For example, a snapshot taken by remote unit 1-4 for station A (e.g., 1-1) differs from a snapshot taken by reference unit 1-2 by a time difference defined as follows: T Arr =T Arem -T Aref +T E (1)

[0107] The letters in the formula represent the following: T Arr =Measured difference in signal arrival time from Station A 1-1 to Remote Unit 1-4 and Reference Unit 1-2 T Arem=Propagation time of signals from Station A 1-1 to Remote Unit 1-4 T Aref =Propagation time of signals from Station A 1-1 to Reference Unit 1-2 T E =Timing error of the Remote Unit 1-4 clock

[0108] In some embodiments, all of the processing steps described below are performed at Remote Unit 1-4. It will be understood that some of the associated processing may be transferred to other units (e.g., Reference Unit 1-2) and the data may then be transmitted.

[0109] At initialization, System 1200 is configured to measure T Xrr (where X represents a station) of the stations (e.g., 1-1) available in the service area by comparing a snapshot of the signals acquired at Remote Unit 1-4 with the spectral information from Reference Unit 1-2. Remote Unit 1-4 can be configured to calculate the propagation time T Xref of each station 1-1 with respect to Reference Unit 1-2 based on the positions of Reference Unit 1-2 and each station 1-1 provided by the broadcast almanac of Reference Unit 1-2. It will be understood that the calculation of the propagation time uses a spherical earth model.

[0110] Upon initialization, System 1200 can be configured to initialize at the estimated position of Remote Unit 1-4. When Remote Unit 1-4 is activated, it can be initialized at any position within the service area. Subsequent positioning can be configured to utilize the last position determined by System 1200. Based on the estimated position, the azimuth to each station 1-1 can be calculated using a spherical earth model. For example, for each station 1-1, the azimuth unit vector, (ux X , uy X ) can be calculated (where in the vector, ux is the sine of the azimuth and uy is the cosine of the azimuth).

[0111] Based on the estimated position, a pair of stations 1-1 can be selected such that their bearing from the estimated position is as large as possible. For each pair of stations, the difference of the unit vector (ux XY ,uy XY ) can be calculated. This is the azimuthal unit vector corresponding to the direction in which the change in arrival time difference per unit distance between the pair of stations is maximized. Based on this estimated position, the estimated propagation time T to the remote units 1-4 can be calculated. Xremest This can be calculated for each station within a pair using a spherical Earth model.

[0112] Based on the values ​​calculated above, the estimated difference T in arrival times between the two stations is calculated. XY It is possible to calculate this. For example, in the case of station A and station D, it is as follows: T AD =T Aremest -T Dremest +T Aref -T Dref (2)

[0113] Measured arrival times T for two stations within a pair Xrr The difference between them is taken, and the clock error term T E Cancel and T XYmeas Obtain the result. Calculate the error between the measured arrival time and the estimated arrival time. T errXY =T XYmeas -T XY (3)

[0114] Based on all possible useful pairs of stations, we can generate a system of equations like the following: T errXY v p =ux XY Δx+uy XY Δy (4) In the formula, v p This is the propagation speed.

[0115] This station is usually overrated. The solution is calculated using an equation weighted based on signal strength. Other criteria may be used for weighting.

[0116] This solution generates a correction vector (Δx, Δy) to improve the estimated position of the remote units 1-4. This vector can be used to correct the current estimate of the position to a new estimate. This new estimate is then used to repeat the above process until the magnitude of the correction vector is less than a predetermined measure of precision (e.g., 1 meter). Thus, when the magnitude of the correction vector becomes smaller than the selected measure of precision, the position of the remote units 1-4 is determined. It will be observed that convergence in such embodiments is rapid and stable.

[0117] Based on the determined location, T for each station 1-1 Xrem This is calculated. Equation 1 can be manipulated as follows: T E =T Xrem -T Xref +T Xrr (5)

[0118] Each station 1-1 T E The values ​​are weighted and averaged to represent the timing error of the clocks of remote units 1-4. This value can be used to regulate the clocks of remote units 1-4 and transmit the time from the clock of reference unit 1-2.

[0119] The system determines the new positioning and timing error, T Xrr The system can be configured to measure a new value and repeat the aforementioned process.

[0120] Furthermore, as can be understood in light of the following description, the system 1200 can be configured to perform position determination based on calculations of arrival time and arrival time difference performed by one or more system components.

[0121] The following is a high-level description of the functions of the reference unit 1-2 and the remote unit 1-4. Reference Unit 1-2

[0122] Receive AM / FM signals from at least three nearby broadcasting towers. a. Convert analog signals to digital and process them. b. Create signal samples at defined time intervals. c. Send timing information and location information to the web server. Remote Unit 1-4 a. Receive AM / FM signals from at least three nearby broadcasting towers. b. Convert analog signals to digital and process them. d. Obtain signal samples from the reference unit from the web server (HTTP query). e. Compare remote digital signal samples with samples from a reference unit. f. Calculate geographical location (latitude, longitude, etc.) and timing correction.

[0123] Since the precise locations of reference device 1-2 and broadcast tower 1-1 are known, the unknown location of remote device 1-4 can be determined using time of arrival ("TOA") or time difference of arrival ("TDOA") calculations.

[0124] By knowing the time difference "tx" between the two towers "1" and "2" relative to the reference device "0", the distances "Δ1" and "Δ2" can be calculated by multiplying this by the speed of light "c". Δ n =r n *c In the formula, "n" is the tower number.

[0125] Source located at point (x,y) and (x n ,y n For the tower located at ), the TDOA calculation is as follows: r0 2 =(x-x0) 2 +(y-y0) 2 r1 2 =(x-x1) 2 +(y-y1) 2 r2 2 =(x-x²) 2 +(y-y2)2 "r1" and "r2" can be substituted into the above equation as follows: R1 = r0 + Δ1 R2 = r0 + Δ2 The above operation yields the following: (r0+Δ1) 2 =(x-x1) 2 +(y-y1) 2 (r0+Δ2) 2 =(x-x²) 2 +(y-y2) 2

[0126] Figure 13 shows, with annotations, how radio waves propagate towards two objects. It will be understood that the distance between the two stations can be determined by performing simultaneous measurements between the two stations using remote units 1-4. As further shown in Figure 14, such a calculated distance can be used to calculate the radius of the intersecting circle by the following calculation. TIFF2026516932000001.tif32146

[0127] In Figure 7, if the distance between stations is L, the central angle of the circle will be either 213 or 2(π-13), depending on whether the mobile receiver unit is in the larger part of the circle relative to L (13 ≤ π / 2) or the smaller part (13 ≥ π / 2). The radius r of the circle is a function of L and Φ, as shown below. TIFF2026516932000002.tif13146

[0128] Once the radius is determined, the system can identify a mirror circle that could be a solution (for example, one that includes all receivers and allows for the calculation of unknown positions). Figure 15 shows examples of two such candidate solutions. The centers (h,k) of these circles can be determined by the positions of two stations (x1,y1) and (x2,y2), along with the radius r and distance L. TIFF2026516932000003.tif33146

[0129] As shown in Figure 16, the equations of the two circles are (x u ,y u This can be represented by the position of the mobile receiver unit in the given circle. If there are more stations, the precise position of the mobile receiver unit can be determined by solving the intersection of these circles.

[0130] Since the reflection and relative receiving positions are unknown, each pair of stations contains eight possible circular solutions. In some embodiments, the system can be configured to perform the following methods to determine the final position. a. For each pair of circles from different stations, simultaneously solve the equation to find 0, 1, or 2 intersection points. b. For each pair of intersections, calculate the distance between the intersections. c. Arrange the pairs in order from shortest to longest distance. d. Filter the results to determine the closest point. You will see that the top points are very close together, while the rest are far apart. Then, average the remaining x and y coordinates to determine the final position.

[0131] Figures 17–19 illustrate various embodiments of the technology of this disclosure configured to add altitude determination to the position determination described above. Figure 17 shows an inertial measurement unit ("IMU"). In some embodiments, the systems described herein have a pitch angle α p It may include an IMU configured to provide real-time data indicating changes in the orientation of the assembly relative to the unit pitch. When the unit pitch is vertical, α p =π / 2 and cos(α p ) = 0. In this case, when the two antennas are pointed vertically, they measure the same distance from all directions, so the yaw angle α y No solution exists. TIFF2026516932000004.tif14146

[0132] Figures 18 and 19 show schematic diagrams of altitude measurement. The altitude of the mobile device can be determined by the built-in altimeter, as long as the built-in altimeter can calibrate itself based on verification of known locations. If the altimeter cannot be calibrated, the mobile device reverts to calculating the altitude based on the received signal. In addition to the IMU sensor, which can provide azimuth data simultaneously for all three axes, a third orthogonal antenna, as shown in Figures 18 and 19, can be used as needed to determine the altitude. Here, roll angle α r This becomes important. When two antenna assemblies are parallel to the ground, the relative angle between them, as measured by the station, will be 90° regardless of yaw. However, if the entire assembly is elevated, this relative angle changes. These angle relationships can be used to determine altitude given a position.

[0133] For example, assume that antennas 0 and 1 of assembly #1 are used to determine the yaw angle α1y(s) relative to the station for positioning. Antennas 0 and 2 of assembly #2 are used to determine the altitude A. The pitch angle αp and roll angle αr are obtained from the IMU. The position and altitude can be determined using the following procedure with the three antennas. a. For antenna assemblies #1 and #2, the yaw angle for each station s. TIFF2026516932000005.tif7146 and Calculate TIFF2026516932000006.tif7146 and remove the azimuth angles αp and αr, respectively. TIFF2026516932000007.tif15146b.Compare two yaw angles to π / 2 and elevation angle The file TIFF2026516932000008.tif7146 has been selected. TIFF2026516932000009.tif13146c.Yaw angle Recalculate TIFF2026516932000010.tif7146 and remove the pitch angle and elevation angle. TIFF2026516932000011.tif15146d. Repeat the above three steps for other stations to calculate the unit position (xu,yu). Determine the altitude A using the distance (xs,ys) to each station s and the tangent of the altitude angle. Add the height H(s) of the transmitting tower and average the altitudes of the N stations. TIFF2026516932000012.tif15146

[0134]

[0135] This paper describes a novel and improved system for accurate geospatial positioning using radio transmission without satellite signals, which overcomes the limitations and shortcomings inherent in related technologies.

[0136] While the technology of this disclosure has been described with a certain degree of detail, it should be understood that this disclosure is illustrative and other forms are possible. Various modifications can be made to the above description without departing from the scope of the technology of this disclosure; therefore, all matters included in the above description or shown in the accompanying drawings are illustrative and not intended to be used in an exclusive sense. The spirit and scope of the accompanying claims should not be limited to the description of preferred forms included in this disclosure.

[0137] All features disclosed herein, including the claims, abstract, and drawings, and all steps in any disclosed method or process, may be combined in any combination, except for any combination in which at least a portion of such features and / or steps are mutually exclusive. Each feature disclosed herein, including the claims, abstract, and drawings, may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each disclosed feature is merely an example of a general set of equivalent or similar features.

[0138] All dimensions specified in this disclosure are illustrative and not intended to limit. Furthermore, the proportions shown in these figures are not necessarily to scale. As will be understood by those skilled in the art based on this disclosure, the actual dimensions and proportions of any system, any apparatus, or any part of a system or apparatus disclosed herein are determined by its intended use.

[0139] Throughout the drawings, reference numbers are reused to indicate correspondences between the referenced components. Furthermore, the first digit of each reference number indicates the drawing in which that component first appears.

[0140] As used in this disclosure, unless the context requires otherwise, the term “equipped,” and its variations such as “equipped,” “to be equipped,” and “equipped,” are not intended to exclude other additions, components, numbers, or processes.

[0141] Specific details are disclosed to provide a complete understanding of the embodiments. However, those skilled in the art will understand that embodiments can be carried out without these specific details. Well-known circuits, structures, and techniques may not be shown in detail to avoid obscuring the embodiments. For example, circuits may be shown in block diagrams to avoid unnecessarily detailing and obscuring the embodiments.

[0142] Certain embodiments are described herein as processes shown as flowcharts, flow diagrams, structural diagrams, or block diagrams. Flowcharts and block diagrams in the figures can illustrate the architecture, functionality, and operation of possible embodiments of systems, methods, and computer programs according to various embodiments disclosed. In this regard, each block in a flowchart or block diagram can represent a module, segment, or portion of code that can constitute one or more executable instructions for implementing a given logical function. It should also be noted that in some alternative embodiments, the functions described in a block may occur out of the order shown in the figure. While flowcharts describe operations as sequential processes, many operations can be performed in parallel or concurrently. Furthermore, the order of operations can be rearranged. A process may terminate when its operations are completed. A process corresponds to a method, function, procedure, subroutine, subprogram, etc. If a process corresponds to a function, its termination corresponds to the function's return to the calling function or main function. Furthermore, each block in a block diagram and / or flowchart, as well as any combination of blocks in a block diagram and / or flowchart, can be implemented by a special-purpose hardware-based system that performs a specified function or action, or by a combination of special-purpose hardware and computer instructions.

[0143] Furthermore, storage can represent one or more devices for storing data, including read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and / or other non-transient machine-readable media for storing information. The term “machine-readable media” includes, but is not limited to, portable or stationary storage devices, optical storage devices, wireless channels, and various other non-transient media capable of storing, configuring, containing, executing, or transporting instructions and / or data.

[0144] Furthermore, embodiments may be implemented by hardware, software, firmware, middleware, microcode, or a combination thereof. When implemented by software, firmware, middleware, or microcode, program code or code segments for performing the required tasks may be stored in a machine-readable medium such as a storage medium or other memory device. One or more processors may perform the required tasks in serial, distributed, concurrently, or in parallel. Code segments can represent procedures, functions, subprograms, programs, routines, subroutines, modules, software packages, classes, or combinations of instructions, data structures, or program statements. Code segments can be coupled to other code segments or hardware circuits by passing information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc., may be passed, transmitted, or transmitted through appropriate means, including memory sharing, message sending, token transmission, network transmission, etc., which are also called interfaces and are points of interaction with software, computer hardware, or peripheral devices.

[0145] In this specification, certain terms are used to describe specific features of one or more embodiments of the disclosed technology. It should be understood that the embodiments and claims disclosed herein are not, in their application, limited to the structural and arrangement details of the components described herein and illustrated in the drawings. Rather, this specification and the drawings provide examples of conceivable embodiments. Further embodiments of the embodiments and claims disclosed herein are possible and can be practiced and implemented in various ways. It should also be understood that the expressions and terms used herein are for illustrative purposes only and should not be considered to limit the scope of the claims.

[0146] Therefore, those skilled in the art will understand that the ideas underlying this application and its claims can be readily used as the basis for the design of other structures, methods, and systems to carry out the embodiments and some of the objectives of the claims presented herein. It is therefore important that the claims be considered to include such equivalent configurations.

Claims

1. Multiple transmitters, each positioned in a different corresponding location, A reference receiver unit positioned at a reference position different from each of the corresponding positions of the plurality of transmitters, At least one processor that communicates with the aforementioned reference receiver unit, Inertial measurement unit, A database that communicates with at least one of the aforementioned processors, A positioning and timing system comprising a remote receiver unit located at an unknown location, Each of the aforementioned plurality of transmitters is It is configured to output a transmission signal that does not coordinate with signals transmitted by other transmitters among the aforementioned plurality of transmitters. Each of the aforementioned transmitted signals is characterized by a corresponding carrier frequency that is different from the frequency of the signal transmitted by the other transmitters among the plurality of transmitters. The aforementioned reference receiver unit is The transmitter signals transmitted by the plurality of transmitters are received, The aforementioned transmitter signal is sampled, Using the at least one of the aforementioned processors, a time reference for each of the received transmitter signals is generated. The measured positions of each of the aforementioned multiple transmitters are stored in the database. The system is configured to broadcast the sampled transmitter signal, the time reference, and the measured position. The remote receiver is The transmitter signals transmitted by the plurality of transmitters are received, The reference unit receives the broadcasted sampled transmitter signal, the time reference, and the corresponding measured position. A positioning and timing system configured to calculate the position of the remote receiver unit and the error of the remote receiver unit's clock relative to the clock of the reference unit, based on a comparison with the broadcasted sample corresponding to the time reference.

2. The positioning and timing system according to claim 1, wherein the multiple transmitters comprise multiple cell towers, and the remote receiver unit comprises a wireless cellular radio receiver capable of receiving signals from nearby cell towers.

3. The positioning and timing system according to claim 2, wherein the remote receiver unit is configured to select two or more of the strongest signals from nearby cell towers.

4. The positioning and timing system according to claim 3, further comprising an inertial measurement unit.

5. The positioning and timing system according to claim 4, wherein calculating the position of the remote receiver unit based on a comparison with the broadcasted sample corresponding to the time reference includes determining the latitude and longitude of the remote receiver unit.

6. The positioning and timing system according to claim 1, wherein the information and time base of the first receiver unit are broadcast by a data channel carried via one or more of the transmitter signals.

7. A positioning and timing system comprising a reference receiver unit located at a known reference position and a remote receiver unit located at an unknown position, The aforementioned reference receiver unit is It receives transmitter signals transmitted by multiple transmitters, each located in a fixed position. The aforementioned transmitter signal is sampled, Using the at least one of the aforementioned processors, a time reference for each of the received transmitter signals is generated. The measured positions of each of the aforementioned multiple transmitters are stored in the database. The system is configured to broadcast the sampled transmitter signal, the time reference, and the measured position. The remote receiver is The transmitter signals transmitted by the plurality of transmitters are received, The reference unit receives the broadcasted sampled transmitter signal, the time reference, and the corresponding measured position. A positioning and timing system configured to calculate the position of the remote receiver unit and the error of the remote receiver unit's clock relative to the clock of the reference unit, based on a comparison with the broadcasted sample corresponding to the time reference.

8. The positioning and timing system according to claim 7, wherein the multiple transmitters comprise multiple cell towers, and the remote receiver unit comprises a wireless cellular radio receiver capable of receiving signals from nearby cell towers.

9. The positioning and timing system according to claim 8, wherein the remote receiver unit is configured to select two or more of the strongest signals from nearby cell towers.

10. The positioning and timing system according to claim 9, further comprising an inertial measurement unit.

11. The positioning and timing system according to claim 10, wherein calculating the position of the remote receiver unit based on a comparison with the broadcasted sample corresponding to the time reference includes determining the latitude and longitude of the remote receiver unit.

12. The positioning and timing system according to claim 7, wherein the information and time base of the first receiver unit are broadcast by a data channel carried via one or more of the transmitter signals.

13. A positioning and timing device comprising a remote receiver unit located at an unknown location, The remote receiver is The transmitter signals transmitted by the plurality of transmitters located at each of the above positions are received. From a reference unit located at a known location, the system receives the transmitter signal sampled by the reference unit, a time reference, and the corresponding measured position. A positioning and timing device configured to calculate the position of a remote receiver unit based on a comparison with a transmitter signal sampled by the reference unit corresponding to the aforementioned time reference.

14. The positioning and timing device according to claim 13, wherein the multiple transmitters comprise multiple cell towers, and the remote receiver unit comprises a wireless cellular radio receiver capable of receiving signals from nearby cell towers.

15. The positioning and timing device according to claim 14, wherein the remote receiver unit is configured to select two or more of the strongest signals from nearby cell towers.

16. The positioning and timing device according to claim 15, further comprising an inertial measurement unit.

17. The positioning and timing device according to claim 16, wherein calculating the position of the remote receiver unit based on a comparison with the broadcasted sample corresponding to the time reference includes determining the latitude and longitude of the remote receiver unit.

18. The positioning and timing device according to claim 13, wherein the information and time base of the first receiver unit are broadcast by a data channel carried via one or more of the transmitter signals.

19. The positioning and timing device according to claim 13, wherein the transmitter signals transmitted by the plurality of transmitters include amplitude-modulated ("AM") radio signals.

20. The positioning and timing device according to claim 13, further comprising a cellular receiver configured to determine an initial position based on received cellular data.

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