CN111458680A

CN111458680A - Method and system for providing an estimate of a position of a user receiver device

Info

Publication number: CN111458680A
Application number: CN202010266201.1A
Authority: CN
Inventors: 格雷戈里·古特; 戴维·G·劳伦斯; 戴维·A·惠兰; 迈克尔·L·奥康纳
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 2013-03-08
Filing date: 2014-02-10
Publication date: 2020-07-28
Also published as: JP6444898B2; CA2896816A1; CA2896816C; SG11201505399UA; CN105026951A; EP2965112A1; JP2016515201A; WO2014137546A1

Abstract

Methods and systems for providing an estimate of a position of a user receiver device are disclosed. The method includes transmitting at least one spot beam on earth from at least one vehicle; and receiving at least one spot beam with the user receiver device. The method further includes calculating, with the user receiver device, an estimate of the location of the user receiver device from the location of the user receiver device within the at least one spot beam. Each spot beam includes at least one acquisition signal, which may include at least one ring channel. Each ring channel includes a frame count; space Vehicle Identification (SVID); spot beam Identification (ID); and/or X, Y, Z coordinates of the vehicle transmitting the spot beam relative to the terrestrial coordinate system. In one or more embodiments, at least one vehicle may be a satellite and/or a pseudolite.

Description

Method and system for providing an estimate of a position of a user receiver device

This application is a divisional application of chinese national phase application 201480013132.6 filed on date 2014/10, international application No. PCT/US2014/015599 entitled "obtaining a geographic location of a channel", having an entry date into the chinese national phase of 2015 9-8, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates to using spot beam overlap for geographic locations. And in particular to obtaining accurate positioning using spot beams that maintain a sufficiently high accuracy for time transformation. In particular, the spot beam utilizes at least one acquisition signal for facilitating a geographic location.

Background

Currently, the navigation and timing signals provided by various existing satellite navigation systems often do not provide satisfactory system performance. In particular, the signal power and bandwidth of such navigation and timing signals are often insufficient to meet the needs of many demanding use cases. For example, existing navigation and timing methods based on Global Positioning System (GPS) signals are generally not available to navigation users in many situations. During operation, to allow for three-dimensional (3D) positioning and accurate time translation, a GPS receiver must typically receive at least four simultaneous ranging sources. However, GPS signals often provide insufficient low signal power or geometry to penetrate urban canyons or walls of buildings. When this occurs, the GPS receiver will not be able to receive the signals it requires for accurate 3D positioning and time conversion. In another example, navigation methods based on cellular telephone or television signals also fail to provide satisfactory system performance. Because their signals typically lack the vertical navigation information desired for many navigation use cases.

Existing navigation systems have attempted to address the deficiencies of indoor navigation by utilizing various methods. Some of these various approaches include the use of inertial navigation systems, dedicated beacons, and high sensitivity GPS systems. It should be noted, however, that each of these approaches has their own unique disadvantages. Inertial navigation systems drift and can be expensive. Beacons, which require special fixed valuable equipment to be measured, can be expensive and are not standardized. As such, the established beacon has only special utility. Also, sensitive GPS systems often meet user expectations due to weak GPS signals in indoor environments. The disclosed systems and methods can provide a navigation system with improved performance when the user receiver device is located in attenuated environments, noisy environments, and/or enclosed environments (such as indoors).

Disclosure of Invention

The present disclosure relates to systems, devices, and methods for using spot beam overlap for geographic locations. In one or more embodiments, a method of using spot beam overlap for a geographic location includes providing an estimate of a location of a user receiver device. The method includes transmitting at least one spot beam on earth from at least one vehicle and receiving a signal from the at least one spot beam with a user receiver device. The method further includes calculating, with the user receiver device, an estimate of the location of the user receiver device from the location of the user receiver device within the at least one spot beam.

In one or more embodiments, the method further includes calculating a distance (range) from the at least one vehicle to the surface of the earth. In some embodiments, the method further comprises calculating a distance from the at least one vehicle to the user receiver device. In at least one embodiment, calculating the range from the at least one vehicle to the user receiver device includes measuring a doppler frequency shift (doppler frequency offset) of the at least one vehicle, calculating a doppler range estimate and/or a pseudorange measurement using a kalman filter, and calculating a running estimate of the range from the at least one vehicle to the user receiver device.

In some embodiments of the present disclosure, methods for using spot beam overlap for geographic locations provide improvements in the accuracy of geographic location algorithms. In one or more embodiments, the user receiver device is located in an attenuated environment, an interfering environment, and/or a closed environment. In at least one embodiment, the enclosed environment is indoors. In some embodiments, the method for using spot beam overlap for geographic location further comprises using signal-to-noise ratio (SNR) measurements from at least one vehicle to further refine (refine) the estimate of the location of the user receiver device.

In one or more embodiments, the at least one vehicle of the present disclosure is a satellite, a pseudolite, a space shuttle, an aircraft, a balloon, and/or a helicopter.

In some embodiments, the method includes at least one vehicle transmitting at least one spot beam using at least one Radio Frequency (RF) antenna. In at least one embodiment, at least one spot beam is radiated from at least one RF antenna as a fixed location beam. In other embodiments, at least one spot beam is radiated from at least one RF antenna as a scanned beam. In some embodiments, the user receiver device receives signals from at least one spot beam using at least one RF antenna.

In one or more embodiments, a user receiver device calculates, using a processor, an estimate of a location of the user receiver device. In some embodiments, when the user receiver device receives signals from only one spot beam, the user receiver device calculates an estimate of the position of the user receiver device that will be located in the center of the intersection of this spot beam. In at least one embodiment, when the user receiver device receives signals from at least two spot beams, the user receiver device calculates an estimate of the position of the user receiver device that will be located in the center of the intersection of the at least two spot beams. In other embodiments, when the user receiver device receives signals from at least two spot beams, the user receiver device calculates an estimate of the position of the user receiver device that will be located at the center of mass of the center of the at least two spot beams.

In some embodiments, the user receiver device of the present disclosure increases with time (t) from the spot beam_RISE) Time to spot beam fall (t)_SET) The spot beam position is recorded. In one or more embodiments, when the mask angle is uniform in various directions with respect to the user receiver device, it is assumed that time is ((t)_SET-t_RISE) /2), the user receiver device is located at the center of the spot beam in the tracking direction (in-track direction). Alternatively, when the shielding angle is not uniform in the spot beam rising direction and the spot beam falling direction, it is assumed that (Δ t) is equal to time_True) /2), wherein (Δ t)_True)/2＝(Δt_{RcverMeasured}+Δt_βBias) In/2, the user receiver device is located at the center of the spot beam in the tracking direction.

In one or more embodiments, the user receiver device calculates an estimate of the position of the user receiver device using the received amplitude of the at least one spot beam. In one or more embodiments, to further improve the estimate of the position of the user receiver device, the user receiver device will average two or more estimates of the position of the user receiver device calculated over time.

In some embodiments, the user receiver device uses a kalman filter to average two or more estimates of the position of the user receiver device. In an alternative embodiment, the user receiver device uses a matched filter to average two or more estimates of the position of the user receiver device. In one or more embodiments, an estimate of the location of the user receiver is used by a Global Positioning System (GPS) to assist in quickly obtaining GPS signals.

In one or more embodiments, a system for using spot beam overlap for geo-location balancing includes providing an estimate of a location of a receiver device of a user. The system includes at least one vehicle and a user receiver device. In some embodiments, at least one vehicle transmits at least one spot beam on earth. In at least one embodiment, a user receiver device includes at least one RF antenna and a processor. In one or more embodiments, at least one RF antenna receives at least one spot beam. In some embodiments, the processor calculates an estimate of the position of the user receiver device from the position of the user receiver device within the at least one spot beam.

In some embodiments, the user receiver device further comprises a local clock and a memory. The memory is adapted to store successive spot beam identification information recorded over time. Additionally, the processor of the user receiver device is capable of calculating a doppler shift of the at least one vehicle.

In other embodiments, the user receiver device receives track delta (△) correction information from the at least one vehicle and/or from a ground based network (earth based network) via the transmission.

In one or more embodiments, a method of providing an estimate of a location of a user receiver device includes transmitting at least one spot beam from at least one vehicle on earth. In at least one embodiment, at least one spot beam includes at least one acquisition signal. The method further includes receiving at least one spot beam with the user receiver device. Further, the method includes calculating, by the user receiver device, an estimate of the location of the user receiver device from the location of the user receiver device within the at least one spot beam.

In at least one embodiment, the at least one acquisition signal includes at least one ring channel. In some embodiments, the at least one ring channel includes a frame count; space Vehicle Identification (SVID); spot beam Identification (ID); and/or X, Y, Z coordinates of the at least one vehicle in relation to the terrestrial coordinate system.

In one or more embodiments, the method further comprises calculating, by the user receiver device, a time from a clock of the at least one vehicle by using the frame count. In some embodiments, the method further comprises calculating, by the user receiver device, a distance from the at least one vehicle to the user receiver device by using a difference between a time from the clock of the at least one vehicle and a time from the clock of the user receiver device. In at least one embodiment, the method further comprises refining, by the user receiver device, the estimate of the location of the user receiver device by using the distance and the X, Y, Z coordinates of the at least one vehicle.

In some embodiments, at least one satellite is a low earth orbit (L EO) satellite, a Medium Earth Orbit (MEO) satellite, and/or a Geosynchronous Earth Orbit (GEO) satellite.

In one or more embodiments, at least one spot beam is radiated as a fixed position beam. In at least one embodiment, at least one spot beam is radiated as a scanned beam. In some embodiments, the user receiver device calculates, using the processor, an estimate of the location of the user receiver device. In one or more embodiments, the user receiver device calculates an estimate of the position of the user receiver device using the amplitude of the at least one spot beam.

In at least one embodiment, a system for providing an estimate of a location of a user receiver device includes at least one vehicle, wherein the at least one vehicle transmits at least one spot beam on earth. In one or more embodiments, at least one spot beam includes at least one acquisition signal. The system further comprises a user receiver device. In at least one embodiment, the user receiver device includes at least one Radio Frequency (RF) antenna, wherein the at least one RF antenna receives at least one spot beam. In some embodiments, the user receiver device additionally comprises a processor, wherein the processor calculates an estimate of the position of the user receiver device from the position of the user receiver device within the at least one spot beam.

In one or more embodiments, the processor further calculates the time from the clock of the at least one vehicle by using the frame count. In some embodiments, the processor further calculates the distance from the at least one vehicle to the user receiver device by using a difference between a time from the clock of the at least one vehicle and a time from the clock of the user receiver device. In at least one embodiment, the processor further refines the estimate of the location of the user receiver device by using the distance and the X, Y, Z coordinates of the at least one vehicle.

In at least one embodiment, the processor calculates an estimate of the position of the user receiver device using the amplitude of at least one spot beam. In one or more embodiments, the user receiver device further comprises a local clock and a memory, wherein the memory is adapted to store successive spot beam identification information recorded over time.

The features, functions, and advantages can be achieved independently in various embodiments of the present inventions or may be combined in yet other embodiments.

Drawings

These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, appended claims, and accompanying drawings where:

fig. 1A illustrates using overlapping multiple spot beams of a single satellite to obtain an estimate of a location of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 1B illustrates the use of overlapping multiple spot beams of a single satellite with a cellular network to obtain an estimate of the location of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 2 depicts the use of overlapping multiple spot beams of a single satellite over time to obtain an estimate of the position of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 3 illustrates using overlapping spot beams of two satellites to obtain an estimate of a position of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 4 illustrates using overlapping multiple spot beams of a single satellite scanned over time to obtain an estimate of a location of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 5 depicts using signal amplitudes of a single satellite received by a user receiver device to obtain an estimate of a position of the user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 6 illustrates using signal amplitudes of two satellites received by a user receiver device to obtain an estimate of a position of the user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 7 illustrates using signal amplitudes of a single satellite scanned over time to obtain an estimate of a position of a user receiver device in accordance with at least one embodiment of the present disclosure.

Fig. 8 is a graphical representation of estimating a position of a user receiver device using a set time of a spot beam of a single satellite for a uniform shielding angle in accordance with at least one embodiment of the present disclosure.

Fig. 9A illustrates a diagram of estimating a position of a user receiver device using rise and fall times of a single spot beam for non-uniform shadowing angles in accordance with at least one embodiment of the present disclosure.

Fig. 9B illustrates a graphical representation of estimating a position of a user receiver device using rise and fall times of a single beam for non-uniform shadowing angles in accordance with at least one embodiment of the present disclosure.

Fig. 10 provides a flow chart illustrating a method of obtaining a continuous estimate of the distance between a user receiver device and a satellite according to at least one embodiment of the present disclosure.

Fig. 11 illustrates a flow diagram of another method of obtaining a continuous estimate of the distance between a user receiver device and a satellite in accordance with at least one embodiment of the present disclosure.

Fig. 12 illustrates a time interval including a single time slot (which supports an exemplary iridium ring channel) and other time slots in accordance with at least one embodiment of the present disclosure.

Fig. 13 provides a table of example frequency allocations for channels (e.g., a ring channel and a message channel) containing the single time slot of fig. 12, in accordance with at least one embodiment of the present disclosure.

Fig. 14 provides a flow chart of a method for a receiver to begin obtaining accurate absolute time from a satellite using the exemplary iridium ring channel of fig. 12 in accordance with at least one embodiment of the present disclosure.

Fig. 15 illustrates an exemplary ring message contained in the single slot of fig. 12 in accordance with at least one embodiment of the present disclosure.

Fig. 16 depicts a block diagram illustrating various exemplary components employed by the disclosed user receiver apparatus, in accordance with at least one embodiment of the present disclosure.

Detailed Description

The methods and apparatus disclosed herein provide an operating system for using spot beam overlap for geographic locations. In particular, the system relates to the use of spot beams to obtain accurate positioning that maintains sufficiently high accuracy for time transformation. In particular, in one or more embodiments, the spot beam utilizes at least one acquisition signal (e.g., an iridium ring channel) for facilitating geographic location.

The simplest approximation of the position of the user receiver device is to compute the projection of the center of the spot beam on the surface of the earth that remains statistically most likely to be the true position of the user receiver device.

The system of the present disclosure employs a method known as beam averaging, including various embodiments to estimate the position of the user receiver device and then refine the estimate with additional measurements. After the first order position estimate is unwrapped from a single spot beam, the estimate can be refined by monitoring successive spot beams that sweep across the user receiver device as time progresses. When there is a case where the user receiver device is located within the intersection of two or more spot beams, the location of the user receiver device can be estimated at the center of the intersection of the spot beams.

During a given duration, the user receiver device will likely be located within multiple overlapping spot beams from a single satellite or multiple satellites. The position of the user receiver device can be estimated at the centroid of the centers of the multiple overlapping spot beams. In addition, two or more consecutive user receiver device position estimates may be averaged over time to further reduce the position error of the user receiver device. Satellites transmitting more spot beams per unit area will provide more accurate estimates of the user receiver devices. By carefully recording which beams are overlapping and how the overlap changes with respect to time, the accuracy of the geolocation algorithm and the satellite range estimation can be significantly improved. In at least one embodiment, the rise and fall times of a single spot beam are tracked, and the position of the user receiver device is estimated at a location within the spot beam that corresponds to the middle between the spot beam rise and fall times determined by the user receiver device.

The particular type of unsynchronized vehicle that may be employed with the present disclosure is exemplified by the iridium satellite constellation, which is a 3-axis stable, earth-pointing satellite in low earth orbit (L EO) that transmits signals to the earth with a known deterministic antenna spot beam pattern₁The position and attitude of the earth-related satellite is known, and if the direction of the transmitted antenna spot beam related to the satellite is known, the time t can be calculated₁The intersection of the centers of the spot beams on the earth's surface. Further, if the characteristics of the antenna spot beam are known, the time t can be calculated₁A pattern of projections of the time antenna spot beam on the earth's surface. This is well known to those skilled in the art. As in the iridium satellite constellation example, the satellite may transmit the spot beam center position to user receiver devices in a defined coordinate system.

By utilizing knowledge of the uniquely identifiable spot beam geometry, a user receiver device detecting at least one spot beam signal is able to discern which set of satellites and spot beams the user receiver device is located in at a given time t 1. For example, portions of the received signal may identify a particular spot beam identification number. Once the spot beam within which the user receiver device is located is determined, the user receiver device may determine its location within the projection of the spot beam. Then, once the user receiver device calculates at time t₁Of time-of-flight spot beamsThe projected position, the user receiver device can calculate at time t₁An estimate of its own position. The accuracy of this measurement will depend on the size of the projection of a given spot beam on the earth's surface. Vehicles transmitting more spot beams per vehicle will provide a more accurate position estimate. As should be readily appreciated, the accuracy of such a system will depend on the size and number of spot beam projections on or near the surface of the sphere. As such, the accuracy of the system may be improved by increasing the number of spot beams and decreasing the radius of the spot beams on the surface of the earth (i.e., the focused spot beams).

Additionally, the types of satellites that may be used as the disclosed vehicles include, but are not limited to, low earth orbit (L EO) satellites, Medium Earth Orbit (MEO) satellites, and/or Geosynchronous Earth Orbit (GEO) satellites.

As previously noted, the present disclosure teaches methods and systems for providing an estimate of the position of a user receiver device. Specifically, in one or more embodiments, a specially designed signal is transmitted from at least one vehicle (e.g., a satellite) to the earth in at least one spot beam. A user receiver device located at or near the surface of the earth receives signals from at least one spot beam. The receiver device calculates an estimate of the position of the user receiver device from the position of the device within at least one spot beam or within the intersection of at least two spot beams. To improve the capabilities and stability of the disclosed methods and systems, it should be noted that in one or more embodiments, additional types of transmission, acquisition channels may be employed to provide signals that may be used to derive an estimate of the position of the user receiver device. Thus, for these embodiments, the acquisition channel is used as a signal of geographic location rather than a specially designed signal that is used to provide data for estimating the location of the user receiver device. The use of an acquisition channel of geographical locations allows for improved accuracy and speed of the resulting user receiver device location data.

In one or more embodiments, a user receiver device may utilize a known frequency, referred to as an acquisition channel, to obtain signals in space. The acquisition channel may use a known frequency that remains globally unchanged so that users around the world may have universal access to the channel. The acquisition channel may be a downlink channel providing an alert to the user receiver device. The alert types include, but are not limited to, a frequency for access by the user receiver device to properly initialize the user receiver device, a frequency for access by the user receiver device to enable channel acquisition, and a frequency for hand-off by the user receiver device.

In one or more embodiments, for example, a ring channel of an iridium satellite system may be used as an acquisition channel in an iridium satellite system, the acquisition channel (referred to as a ring channel or a ring alert channel) is one of twelve frequency access bands reserved for a single time slot, these channels are located in the globally allocated 500 kilohertz (kHz) between 1626.0 megahertz (MHz) and 1626.5 MHz.

When decoded, a typical ring message may contain information such as L band frame count (L BFC), Space Vehicle Identification (SVID), spot beam Identification (ID), and satellite X, Y, Z coordinates Iridium pulse sequence (Iridium burst sequence) occurs every 90 milliseconds in a L band frame, so the L BFC value is a valid clock with microsecond precision because the edge of the L band frame (and thus L BFC) is accurate on the microsecond level, the ring message acts as and can be used as a very accurate clock that rings every 90 milliseconds.

In the following description, numerous details are set forth in order to provide a more thorough description of the system. It will be apparent, however, to one skilled in the art that the disclosed system may be practiced without these specific details. In other instances, well-known features have not been described in detail so as not to unnecessarily obscure the present system.

Fig. 1A illustrates the use of overlapping multiple spot beams 110 of a single satellite 100 to obtain an estimate of the location of a user receiver device 120 in accordance with at least one embodiment of the present disclosure. Also, fig. 1B illustrates overlapping multiple spot beams 110 and cellular network 130 using a single satellite 100 to obtain an estimate of the location of the user receiver device 120 in accordance with at least one embodiment of the present disclosure. FIG. 1B is similar to FIG. 1A except that FIG. 1B employs the use of a cellular network 130. In both figures, it can be seen that a single satellite 100 transmits at least one spot beam 110 on earth. In one or more embodiments, the satellite 100 transmits at least one spot beam 110 using at least one Radio Frequency (RF) antenna. The user receiver device 120 receives signals from at least one projected spot beam 110. The user receiver device 120 then computes an estimate of its location on earth from its location within one of the projected spot beams 110.

In fig. 1A and 1B, the user receiver device 120 calculates the location of at least one spot beam within which the user receiver device 120 is located. To perform this calculation, the user receiver device 120 uses knowledge of the position of the satellite 100, knowledge of the attitude of the satellite 100 and/or knowledge of the direction and/or pattern of the spot beam 110. In some implementations, in order for the user receiver device 120 to obtain knowledge of the direction and/or pattern of the spot beam 110, the user receiver device 120 references a beam geometry database and/or an internal orbit pattern.

In fig. 1A, the position information (i.e., ephemeris) of the satellite 100 is transmitted from the satellite 100 itself to the user receiver device 120. In some embodiments, the user receiver device 120 receives orbit data information and/or orbit delta correction information from the satellite 100 via transmission. In one or more embodiments, the user receiver device 120 calculates the position of the satellite 100 by using data from its internal orbital mode and using orbital incremental corrections received from the satellite 100. In some embodiments, the computation of the direction and/or pattern of the spot beam 110 is done on the satellite 100. The direction and/or pattern information for the spot beam 110 may be transmitted from the satellite 100 to the user receiver device 120 as part of a message contained in the signal for the spot beam.

Alternatively, in fig. 1B, the location information (i.e., ephemeris) of the satellite 100 is transmitted to the user receiver device 120 over the cellular network 130. In other embodiments, the system of the present disclosure may employ various types of ground-based networks other than cellular networks to transmit the position information (i.e., ephemeris) of the satellites 100 to the user receiver devices 120. In some embodiments, user receiver device 120 receives orbit data information and/or orbit delta correction information via transmission from cellular network 130. In one or more embodiments, the user receiver device 120 calculates the position of the satellite 100 by using data from its internal orbit pattern and using orbital incremental corrections received from the cellular network 130.

In one or more embodiments, when the user receiver device 120 receives signals from only one spot beam 110, the user receiver device 120 computes an estimate of the location of the user receiver device 120 that will be in the center of the spot beam. Alternatively, when the user receiver device 120 receives signals from two or more spot beams 110, the user receiver device 120 computes an estimate of the location of the user receiver device 120 that will be located at the center of the intersection 150 of the spot beams 110 from which signals are received. In other implementations, when the user receiver device 120 receives signals from two or more spot beams 110, the user receiver device 120 computes an estimate of the location of the user receiver device 120 that will be located at the center of mass of the center of the spot beam 110 from which the signals are received. In at least one embodiment, the user receiver device 120 uses signal-to-noise ratio (SNR) measurements received from the satellites 100 to further refine the calculated estimate of its position. It should be noted that in some embodiments, the estimation of the position of the user receiver device 120 is used to provide an improvement in the accuracy of the currently used geolocation algorithm. Further, the estimate of the location of the user receiver device 120 may be used by a Global Positioning System (GPS) to assist in quickly obtaining GPS signals.

In some embodiments, the user receiver device 120 of fig. 1A and 1B includes at least one Radio Frequency (RF) antenna 140 for receiving signals from at least one spot beam projected by the satellite 100. The RF antenna may be manufactured either inside or outside the housing of the user receiver device 120. In some embodiments, the user receiver device 120 further comprises a processor that calculates an estimate of the location of the user receiver device 120 from the location of the user receiver device 120 within the at least one spot beam 110. In at least one embodiment, the user receiver device 120 further includes a local clock and memory adapted to store continuous spot beam identification information recorded over time. In one or more embodiments, the user receiver device 120 is mobile or stationary.

For these embodiments, the user receiver device 120 may obtain information from the iridium ring channel, spot beam 110ID number, X, Y, Z coordinates of the satellite 100 relative to the terrestrial coordinate system, and time of the satellite 100 clock through the use of L BFC.

Fig. 2 depicts the use of overlapping multiple spot beams of a single satellite 100 over time to obtain an estimate of the location of a user receiver device 120 in accordance with at least one embodiment of the present disclosure. In this figure, it is shown that at time t₀The user receiver device 120 is located within the intersection 210 of the spot beams 200 radiated by the SAT1 satellite 100. It should be noted that in this figure, the spot beam 200 radiated by the SAT1 satellite 100 is a fixed-direction beam and not a scanning beam. In one or more implementations, the processor of the user receiver device 120 computes a first estimate of the position of the user receiver device 120 that will be located at the center of the intersection 210 of the spot beam 200. The user receiver device 120 then stores the time t₀The position of the spot beam 200 and stores in its memory this first estimate of the position of the user receiver device 120.

Also as shown in this figure, at a later time t₀+ Δ t, the spot beam 200 radiated from the SAT1 satellite 100 sweeps across the surface of the earth. As such, the user receiver devices 120 are now located within different intersections 220 of the spot beams 200 on the surface of the earth. At this point, the processor of the user receiver device 120 computes a second estimate of the position of the user receiver device 120 that will be located at the center of the intersection 220 of the spot beam 200. The user receiver device 120 then stores the time t₀The location of the spot beam 200 at + Δ t, and a second estimate of the location of the user receiver device 120 is stored in its memory.

Once the user receiver device 120 obtains at least two estimates of the position of the user receiver device 120, the processor of the user receiver device 120 uses the estimates to calculate a further refined estimate of the position of the user receiver device 120. In this figure, it is shown that the processor of the user receiver device 120 calculates that the position of the user receiver device 120 will be in the center of the overlap area 230 of the intersection 210 area and the intersection 220 area.

In one or more embodiments, the user receiver device 120 uses a beam averaging technique in order to obtain a further refined estimate. With this technique, the processor of the user receiver device 120 calculates an average of the stored estimates of the positions of all the user receiver devices 120 to obtain a refined estimate. In some implementations, the processor of the user receiver device 120 uses a kalman filter to perform the beam averaging. In an alternative embodiment, the processor of the user receiver device 120 uses a matched filter to perform beam averaging.

Fig. 3 illustrates using overlapping multiple spot beams of two satellites to obtain an estimate of a position of a user receiver device in accordance with at least one embodiment of the present disclosure. In the figure, at time t is shown₀At this time, the user receiver device 120 is located within the intersection 320 of the spot beams 310 radiated by the SAT1 satellite 100 and the SAT 2 satellite 300. In this figure, the spot beam 310 radiated by the SAT1 satellite 100 and the SAT 2 satellite 300 is not a scanning beam but a beam of a fixed direction. In some embodiments, the processor of the user receiver device 120 computes a first estimate of the position of the user receiver device 120 to be located at the center of the intersection 320 of the intersection 330 of the spot beam radiated by the SAT1 satellite 100 and the intersection 340 of the spot beam radiated by the SAT 2 satellite 300. The user receiver device 120 then stores the time t in its memory₀The location of the spot beam 310 and stores this first estimate of the location of the user receiver device 120.

In at least one embodiment, at time t₀At + Δ t, the spot beams 310 radiated from the SAT1 satellite 100 and the SAT 2 satellite 300 have swept the surface of the earth. As such, the user receiver device 120 is now located within a different intersection of the spot beam radiated by the SAT1 satellite 100 and the intersection of the spot beam radiated by the SAT 2 satellite 300. At this point, the processor of the user receiver device 120 computes a second estimate of the position of the user receiver device 120 that will be located in the intersection of the spot beam radiated by the SAT1 satellite 100 and the intersection of the spot beam radiated by the SAT 2 satellite 300.

The user receiver device 120 then stores the time t₀Bit of the spot beam 310 at + Δ tAnd stores in its memory a second estimate of the location of the user receiver device 120. In some embodiments, the user receiver device 120 obtains a more refined estimate by using the beam average. For the beam average, the processor of the user receiver device 120 determines the refined estimate by calculating the average of the stored estimates of the positions of all the user receiver devices 120.

It should be noted that in an alternative embodiment, the processor of the user receiver device 120 calculates the position of the user receiver device 120 to be located at the center of mass of the spot beam radiated by the SAT1 satellite 100 and the center of the spot beam radiated by the SAT 2 satellite 300.

Fig. 4 illustrates using overlapping multiple spot beams of a single satellite scanned over time to obtain an estimate of a location of a user receiver device in accordance with at least one embodiment of the present disclosure. In the figure, at time t is shown₀The user receiver device 120 is located within the intersection 410 of the spot beams 400 radiated by the SAT1 satellite 100. It should be noted that the spot beam 400 radiated by the SAT1 satellite 100 is a scanned beam, rather than a fixed-direction beam. In this manner, scanning beam 400 sweeps across the earth's surface over time. The processor of the user receiver device 120 computes a first estimate of the position of the user receiver device 120 that will be located at the center of the intersection 410 of the spot beams 400 radiated by the SAT1 satellite 100. The user receiver device 120 then stores the time t in its memory₀The position of the spot beam 400 and stores this first estimate of the position of the user receiver device 120.

At time t₀+ Δ t, the scanning spot beam 400 radiated from the SAT1 satellite 100 has swept the surface of the earth. The user receiver devices 120 are now located within different intersections 420 of the spot beam 400 on the surface of the earth. At this point, the processor of the user receiver device 120 computes a second estimate of the position of the user receiver device 120 that will be located at the center of the intersection 420 of the spot beam 400. The user receiver device 120 then stores the time t in its memory₀The position of the spot beam 400 at + Δ t, and the user receiver is storedA second estimate of the location of the device 120.

After the user receiver device 120 obtains at least two estimates of the position of the user receiver device 120, the processor of the user receiver device 120 uses the estimates to calculate a refined estimate of the position of the user receiver device 120. The processor of the user receiver device 120 computes a refined estimate of the position of the user receiver device 120 that will be located at the center of the overlap area 430 of the intersection 410 area and the intersection 420 area.

In some embodiments, the user receiver device 120 uses the beam average to calculate a further refined estimate. For this technique, the processor of the user receiver device 120 calculates an average of the stored estimates of the positions of all the user receiver devices 120 to obtain a refined estimate.

Fig. 5, 6, and 7 illustrate various embodiments of using satellite signal amplitudes to obtain an estimate of a position of a user receiver device according to various embodiments of the present disclosure. In particular, fig. 5 depicts using signal amplitudes of a single satellite received by the user receiver device to obtain an estimate of the position of the user receiver device, fig. 6 depicts using signal amplitudes of two satellites received by the user receiver device to obtain an estimate of the position of the user receiver device, and fig. 7 depicts using signal amplitudes of a single satellite of a scanned spot beam over time to obtain an estimate of the position of the user receiver device.

In fig. 5, an SAT1 satellite 100 radiates a spot beam 110 on earth. In this figure, a spot beam 500 is shown having a main beam 510 and two-sided lobe beams 520. It should be noted that for this figure, the spot beam 500 is a fixed direction beam, rather than a scanned beam. In this figure, the user receiver device 120 is shown receiving a signal from a main beam 510 of radiation. The processor of user receiver device 120 uses the amplitude of the received signal to compute an estimate of its position on earth from its position within the signal amplitude profile (signal amplitude on route) 530 of the projected main beam 510. Once the user receiver device 120 obtains an estimate of its location, the user receiver device 120 stores in its memory the location of the spot beam 500 on the earth and stores an estimate of the location of the user receiver device 120.

In fig. 6, the SAT1 satellite 100 and the SAT 2 satellite 300 are each shown radiating a

spot beam

600, 610, respectively, on earth. In this figure, the user receiver device 120 is shown as being located within the intersection 630 of the spot beam 600 radiated by the SAT1 satellite 100 and the spot beam 610 radiated by the SAT 2 satellite 300. For this figure, spot beam 600 and spot beam 610 are fixed direction beams, rather than scanned beams. The processor of the user receiver device 120 uses the amplitude of its received signal to compute its estimate of its position within the intersection 630 from its position within the signal amplitude profile 640 of the projected

spot beam

600, 610. After the user receiver device 120 obtains an estimate of its position, the user receiver device 120 stores the spot beam 600 and spot beam 610 positions in its memory and stores an estimate of the user receiver device 120's position.

In FIG. 7, at time t₀The SAT1 satellite 100 is shown radiating a spot beam 700 on earth. At this point, the user receiver device 120 is located within the spot beam 700 radiated by the SAT1 satellite 100. It should be noted that the spot beam 700 radiated by the SAT1 satellite 100 is a scanned beam, rather than a fixed-direction beam. Thus, the spot beam 700, as scanned over time, sweeps across the earth's surface. The processor of the user receiver device 120 calculates its first estimate of its position within the spot beam 700 using the amplitude of the received signal in dependence on its position within the signal amplitude profile of the spot beam 700. The user receiver device 120 then stores the time t in its memory₀The location of the spot beam 700, and a first estimate of the location of the user receiver device 120 is stored.

Also in FIG. 7, at time t₀At + Δ t, the spot beam 700 radiated from the SAT1 satellite 100 is shown as having swept the surface of the earth (now shown as spot beam 710). The user receiver device 120 is now located within the spot beam 710. At this time, the processor of the user receiver device 120 calculates it using the amplitude of the received signal according to its position within the signal amplitude profile of the spot beam 710A second estimate of the location within the spot beam 710. The user receiver device 120 then stores the time t in its memory₀The location of the spot beam 710 at + Δ t, and a second estimate of the location of the user receiver device 120 is stored.

Once the user receiver device 120 obtains at least two estimates of the position of the user receiver device 120, the processor of the user receiver device 120 uses the estimates to compute a further refined estimate of the position of the user receiver device 120. The processor of the user receiver device 120 uses the beam averaging to calculate a further refined estimate of the position of the user receiver device 120 that will be within the overlap region 720 of the spot beam 700 and the spot beam 710. In addition, the processor obtains a further refined estimate of the position of the user receiver device 120 from its position within the

spot beam

700 and 710 signal amplitude profile 730 by using its received signal amplitude to calculate its position in the overlap region 720.

Fig. 8 is a graphical representation of estimating the position of a user receiver device 120 using the rise time and fall time of the spot beam of a single satellite 100 for uniform shielding angles in accordance with at least one embodiment of the present disclosure. In this figure, the rise time and fall time of the spot beam are used to obtain an estimate of the position of the user receiver device 120. For these embodiments, the time of rise from the spot beam (t) is recorded_RISE) Time to spot beam fall (t)_SET) Of all spot beams. Suppose that at time ((t)_SET-t_RISE) /2), the elevation mask angle is uniform in all directions relative to the user receiver device 120, assuming the user receiver device is located at the center of the spot beam in the tracking direction.

It should be noted that the tracking direction is defined as the direction of movement of the satellite through the user receiver device 120 in the air. For the tracking direction coordinate system, the origin is located at the position of the user receiver device 120, the x-axis is the direction of movement of the satellite through the user receiver device 120 in the air, the z-axis is the direction towards the geocentric, and the y-axis completes the right-hand Cartesian coordinate system.

Fig. 9A illustrates a schematic diagram of estimating a position of a user receiver device using rise and fall times of a single spot beam for uniform shielding angles, according to at least one embodiment of the present disclosure. And, fig. 9B illustrates a graphical representation of estimating a position of a user receiver device using rise and fall times of a spot beam of a single satellite for non-uniform shadowing angles according to at least one embodiment of the present disclosure. For these figures, since the beam patterns of the satellite constellation that pass through the user receiver devices are in known directions (e.g., north-south directions), only the shadowing angles in these directions (e.g., north-south directions) will become relevant, since the first direction (e.g., north) is the direction in which the satellite is rising and the second direction (e.g., south) is the direction in which the satellite is falling.

For these embodiments α denotes the constellation shading angle β₁Is the shadowing angle associated with a possible obstruction blocking the line of sight of the user receiver device to the satellite in the direction of satellite ascent, and β₂Is the shadowing angle associated with a possible obstruction blocking the user receiver device's line of sight to the satellite in the direction of satellite descent when one β angle or two β angles>α, when β₁＝β₂α or β₁＝β₂Not equal to α, a uniform shading angle as discussed in FIG. 8 occurs for these embodiments β angle is known or estimated FIG. 9A and 9B show that there is β₂Special case of an obstacle larger than the shielding angle α. when there is a small obstacle in the satellite up direction, β₁<α and, thus, the obstacle does not affect the line of sight of the user receiver device to the satellite>α, assuming non-uniformity in elevation in the direction of satellite ascent and in the direction of satellite descent, it can be assumed that, at time (Δ t)_True) /2, wherein (Δ t)_True)/2＝(Δt_{RcverMeasured}+Δt_β2Bias) In/2, the user receiver device is located at the center of the spot beam projection in the tracking direction.

Fig. 10 provides a flow chart 1000 illustrating a method of obtaining a running estimate of a range between a user receiver device and a satellite in accordance with at least one embodiment of the present disclosure, hi this figure, the user receiver device receives satellite ephemeris data 1010 from a low earth orbit (L EO) satellite, it is noted that in other various embodiments, the disclosed methods may employ a different type of satellite in addition to a L EO satellite.

After the user receiver device receives the ephemeris data, the processor of the user receiver device derives the instantaneous satellite position, velocity and acceleration 1020. After the user receiver device computes these inferences (derivitiations), the user receiver device receives the initial spot beam identifier 1030 of the radiated satellite spot beam from the satellite. After receiving the spot beam identifier from the satellite, the user receiver device records the spot beam identifier and the spot beam centers of the successive spot beams in the memory of the user receiver device 1040.

The processor of the user receiver device then uses the beam averaging technique to derive a running user receiver device position estimate 1050 using those recorded spot beam identifiers and spot beam centers. The processor of the user receiver device then derives an estimate 1060 of the operation of the user receiver device to the satellite unit vector. Next, the processor of the user receiver device measures the doppler shift 1070 of the satellite. The processor of the user receiver device then calculates a doppler range estimate 1080 using the doppler shift. In at least one embodiment, the user receiver device calculates the doppler range estimate using a kalman filter. The user receiver device maintains a continuous estimate 1090 of the computed user receiver device-to-satellite distance (range).

Fig. 11 illustrates a flow diagram 1100 of another method of obtaining a continuous estimate of the distance between a user receiver device and a satellite in accordance with at least one embodiment of the present disclosure. As shown therein, the method steps of fig. 11 are similar to those described in fig. 10. Unlike the method of fig. 10, however, the method disclosed in fig. 11 allows the various steps to be performed in varying orders.

As described above, in one or more embodiments, an acquisition channel may be employed to provide a signal for each spot beam.an acquisition channel may be used to derive an estimate of the position of a user receiver device.in some embodiments, a ring channel of an iridium satellite system may be used as an acquisition channel.FIG. 12 illustrates a time interval 1200 including a single time slot (which supports the exemplary iridium ring channel) and other time slots in accordance with at least one embodiment of the present disclosure. As shown in FIG. 12, the time interval 1200 is for about 90 milliseconds (ms) and includes a single time slot lasting about 20.32 milliseconds, four uplink time slots U L1-U L4, and four downlink time slots D L1-D L4, each lasting about 8.28 milliseconds.

The communication channel may be implemented in a communication or satellite system (e.g., an iridium satellite network) using a hybrid time division multiple access-frequency division multiple access (TDMA/FDMA) structure based on Time Division Duplexing (TDD) using 90 millisecond frames (e.g., time interval 1200). For example, a particular channel may be a particular FDMA frequency (e.g., carrier band) and TDMA time slot (e.g., one of the single, uplink or downlink, shown in fig. 12). For example, channels may be reused in different geographic locations by implementing acceptable co-channel interference limits or other channel de-collision methods (such as time division multiplexing). Thus, the channel allocation may include frequency carriers and time slots in the frame.

In one embodiment, a single time slot may include an acquisition channel that may use a known frequency that remains globally unchanged so that users around the world may access the acquisition channel. The acquisition channel may be a downlink channel formatted using TDMA and providing alerts for user devices, which may include an accessed frequency to complete a user call (e.g., for embodiments employing an iridium satellite network). The TDMA structure of the acquisition channel may allow multiple alerts to be sent in one frame, such as time interval 1200. In addition, other channels may support user receiver devices (e.g., mobile phones or other compact electronic devices), for example, by providing information required to enable channel acquisition and switching (hand-off).

To mitigate such a situation, a second transmission (subcontrarbytransmission) may be broadcast over one or more frequencies (e.g., there are four message channels available on an iridium satellite system). in principle, for example, the second transmission may be broadcast over the entire 10MHz of the iridium L band (i.e., 1616MHz to 1626.5 MHz).

Fig. 13 provides a table 1300 of example frequency allocations for channels (e.g., a ring channel and a message channel) including the single time slot of fig. 12, in accordance with at least one embodiment of the present disclosure. For this exemplary embodiment, twelve frequency access bands may be reserved for a single slot channel (i.e., an acquisition channel and a message channel). These channels may be located in 500kHz allocated globally between 1626.0MHz and 1626.5 MHz. These frequency accesses may be for downlink signals only, and may be only frequencies that may be transmitted during a single time slot. As shown in table 1300 for the iridium example, four message channels and one ring alert channel are available during a single time slot.

The four message channels in a single time slot, located on alternating frequencies with the ring channel (i.e., the ring alert channel), may be used for channel acquisition and transmit precise absolute time if the ring channel is unavailable for some reason (e.g., if the ring channel is disturbed). the message channels for iridium (as shown in table 1300) are

channels

3, 4, 10 and 11, which are four-level, three-level, two-level and primary message channels, respectively.

In some embodiments, the acquisition data may also be located in portions across multiple alternate message channels with different encryption, for example, in order to further reduce unauthorized accessibility of information, or in the event that one encryption or both encryption methods are at risk due to rogue users.

FIG. 14 provides a flow diagram of a method 1400 for starting to obtain accurate absolute time from a satellite using the exemplary iridium ring channel user receiver device of FIG. 12 in accordance with at least one embodiment of the present disclosure at the start 1405 of the method 1400, a user receiver device (e.g., any of the various user receiver devices described herein) may attempt to receive data from a satellite (e.g., a low earth orbit (L EO) satellite, such as an iridium satellite) over an acquisition channel at block 1410.

Fig. 15 illustrates an exemplary ring message 1500 contained in the single slot of fig. 12 as shown, when decoded, a typical ring message 1500 (or access message) may contain information such as L BFC 485215784, SVID 34, beam ID 6, X coordinate 127, Y coordinate-1140 and Z coordinate 1102.

In this regard, Space Vehicle Identification (SVID) may be used as information in understanding which satellite relay message 1500. The beam ID (or spot beam Identification (ID)) number can be used to identify which spot beam transmits a message for determining the geographic location of the user receiver device. X, Y and the Z coordinates are position coordinates of the satellites and may be used to correct the time of flight of signals from the space vehicles (i.e., satellites) to the receiver user devices. The X, Y, Z coordinates may also be used for the geographic location of the user receiver device.

With respect to L BFC values, the iridium pulse signal sequence occurs every 90 milliseconds in a so-called L band frame (see fig. 12). L BFC values have an effective clock with microsecond precision for example L BFC values may be a 32-bit number of values that count 90 millisecond frames from a known reference start time (e.g., also referred to as a "epoch").

Referring back to fig. 14, in block 1415, if an acquisition channel is available, then the user receiver device receives ring message data from the acquisition channel and the method continues to block 1430. Otherwise, the method continues to block 1420.

In this regard, relying on a known fixed frequency channel (e.g., acquisition channel) as the only predictable location to find the critical acquisition information described above may enable any significant resource to utilize iridium to support applications that are susceptible to interference. By placing the same critical acquisition information on the single slot message channels described above, as identified at block 1420, the user receiver device may attempt to receive (e.g., search in an alternative message channel) channel acquisition data (e.g., ring message data) from one of the message channels (e.g.,

channels

3, 4, 10, 11 described above). By placing the ring message data on a single time slot message channel, the satellite system can propagate the interference threat to multiple frequencies and can also increase the signal power by 9 decibels (dB), making the satellite system more robust to interference.

At block 1430, the user receiver device may receive encrypted ring message data on a message channel (e.g., or if available over an acquisition channel as determined in block 1415). In various embodiments, the encoding of the ring message data may be specially encrypted for a particular user (e.g., the U.S. military).

For example, one option may include more levels by additionally extending the invocation priority and priority levels, assigning levels, such as quality of service (QoS) or class of service (L oS), or adding a level queuing methodology to the system.

At block 1450, the user receiver device may use the decrypted torus information data to identify the satellites from which the torus message data was received, and may use the position coordinate information in the torus information data to correct the time of transmission of signals between the satellites and the user receiver device.

Time (Era + L BFC) ﹡ 90ms + time bias + (distance/C)

In the above equation, "Era" may be based on a known date/time as defined for the system (e.g., an iridium system) and the user receiver device may have a priori knowledge. For example, "time offset" (or slot offset) may represent any time offset in the system that can compensate for measurement errors in the satellite's clock and/or known slot variations in the transmission sequence. The time slots may be provided by the satellite or they may be measured by the reference station or they may be fixed or predictable as part of the service.

"range" means the distance between the satellite and the user receiver device and is calculated using a satellite orbit pattern that can be transmitted via a data link, a suitably accurate knowledge of the position of the user receiver device and an approximate time (as input to the satellite orbit pattern). In one embodiment, to obtain an accuracy within about 10 microseconds, the distance estimate must be accurate to about 3000 meters (m), which may be approximately equal to 20000m for planar accuracy on the ground. Such a level of positioning can be easily achieved via cellular network technology, for example. Furthermore, a simple beam coverage method may be employed to determine the location of the user receiver device based on knowledge of which satellite the user is currently located in and the recent beam time history. Many other methods of coarse positioning may also be suitably employed. In one embodiment, the satellite orbit information (e.g., ephemeris) of the satellite includes position information such as the satellites within a constellation of satellites at different points in time and other information that may be used by the user receiver device to accurately obtain clock values from the satellites. In this embodiment, the network can easily determine the location of the user receiver device (or user) within less than one kilometer. This distance can be accurate to about 3 km. The position of the satellites may be determined using the approximate time and orbit information of the user receiver device. After the range of the satellite is determined, it is then divided by the speed of light (also referred to as "C").

Repeating each L band frame every 90 milliseconds (e.g., L BFC increments of 2.5 add 1 to the count). L the edge of the band frame (e.g., the instant the user receiver device receives the signal) may allow the user receiver device to maintain the accuracy of the user receiver device's time (e.g., adjust the user receiver device's local clock at block 1460) to the level of microseconds.

Fig. 16 depicts a block diagram 1600 illustrating various exemplary components employed by the disclosed user receiver device 1600 in accordance with at least one embodiment of the present disclosure. In this regard, user receiver device 1600 may be used to implement any of the various user receiver devices described herein. For example, in one embodiment, the user receiver device 1600 may be used to implement a navigation device.

User receiver device 1600 may include an antenna 1610, a Radio Frequency (RF) front end and digitizer 1615, a processor 1620, a clock 1630, memory, and other components 1650.

The antenna 1610 may be implemented as one or more antennas for transmitting and/or receiving signals in accordance with various implementations described herein.

The RF front end and digital converter 1615 may include an amplifier, a radio frequency down converter, and an analog-to-digital (a/D) converter. The RF front end and digitizer 1615 may process the signal from the antenna 1610 and provide information from the signal to the processor 1620.

The processor 1620 may be implemented as one or more processors executing appropriate instructions (e.g., software) stored in one or more memories 1640 and one or more non-transitory machine (or computer) readable media 1690 (or both). Clock 1630 (e.g., the user receiver device clock) may be a clock that is adjusted or operated according to the various techniques described above.

Other components 1650 may be used to implement any other desired features of user receiver device 1600. It should be understood that one or more of the satellites described herein may be implemented using the same, similar, or complementary components to those shown in fig. 16, where appropriate.

The various embodiments provided by the present disclosure may be implemented using hardware, software, or a combination of hardware and software, where appropriate. Also where applicable, the various hardware components and/or software components set forth herein can be combined into composite components comprising software, hardware, and/or both without departing from the spirit of the present disclosure. Where applicable, the various hardware components and/or software components set forth herein may be divided into sub-components comprising software, hardware, and/or both without departing from the spirit of the present disclosure. Further, where applicable, it is contemplated that software components may be implemented as hardware components and vice versa.

Software in accordance with the present disclosure, such as program code and/or data, may be stored on one or more computer-readable media. It is contemplated that software identified herein may be implemented using one or more general purpose or special purpose computers and/or computer systems, networks, and/or otherwise. Where applicable, the order of various steps described herein can be changed, combined into composite steps, and/or divided into sub-steps to provide features described herein.

While certain exemplary embodiments and methods have been disclosed herein, it will be apparent to those skilled in the art from this disclosure that variations and modifications of these embodiments and methods may be made without departing from the true spirit and scope of the invention. There are numerous other examples of the disclosed technology, each differing from the others only in details. Accordingly, it is intended that the disclosed technology be limited only by the scope of the appended claims and the rules and principles of applicable law.

Claims

1. A method of providing an estimate of a position of a user receiver device, the method comprising:

transmitting at least one spot beam on earth from at least one vehicle,

wherein the at least one spot beam comprises at least one acquisition signal;

receiving the at least one spot beam with the user receiver device; and

calculating, by the user receiver device, an estimate of the location of the user receiver device from a location of the user receiver device within the at least one spot beam.

2. The method of claim 1, wherein the at least one acquisition signal comprises at least one ring channel.

3. The method of claim 2, wherein the at least one ring channel comprises a frame count; space Vehicle Identification (SVID); spot beam Identification (ID); and X, Y, Z coordinates of the at least one vehicle in relation to the terrestrial coordinate system.

4. The method of claim 3, wherein the method further comprises calculating, by the user receiver device, a time from a clock of the at least one vehicle by using the frame count.

5. The method of claim 4, wherein the method further comprises calculating, by the user receiver device, a distance from the at least one vehicle to the user receiver device by using a difference between a time from the clock of the at least one vehicle and a time from the clock of the user receiver device.

6. The method of claim 5, wherein the method further comprises refining, by the user receiver device, the estimate of the location of the user receiver device by using the distance and the X, Y, Z coordinates of the at least one vehicle.

7. The method of claim 1, wherein the at least one vehicle is at least one of a satellite, a pseudolite, a space shuttle, an aircraft, an airplane, an Unmanned Aerial Vehicle (UAV), a balloon, and a helicopter.

8. The method of claim 1, wherein the at least one spot beam is radiated as a fixed position beam.

9. The method of claim 1, wherein the at least one spot beam is radiated as a scanned beam.

10. The method of claim 1, wherein the user receiver device calculates an estimate of the location of the user receiver device using a processor.

11. The method of claim 1, wherein the user receiver device calculates an estimate of the location of the user receiver device using an amplitude of the at least one spot beam.

12. A system for providing an estimate of a location of a user receiver device, the system comprising:

at least one vehicle, wherein the at least one vehicle transmits at least one spot beam on earth, and wherein the at least one spot beam comprises at least one acquisition signal; and

the user receiver apparatus, wherein the user receiver apparatus comprises:

at least one Radio Frequency (RF) antenna, wherein the at least one RF antenna receives the at least one spot beam, an

A processor, wherein the processor calculates an estimate of a location of the user receiver device from the location of the user receiver device within the at least one spot beam.

13. The system of claim 12, wherein the at least one acquisition signal comprises at least one ring channel.

14. The system of claim 13, wherein the at least one ring channel comprises a frame count; space Vehicle Identification (SVID); spot beam Identification (ID); and X, Y, Z coordinates of the at least one vehicle in relation to the terrestrial coordinate system.

15. The system of claim 14, wherein the processor further calculates a time from a clock of the at least one vehicle by using the frame count.

16. The system of claim 15, wherein the processor further calculates a distance from the at least one vehicle to the user receiver device by using a difference between the time from a clock of the at least one vehicle and a time from a clock of the user receiver device.

17. The system of claim 16, wherein the processor further refines the estimate of the location of the user receiver device by using the distance and the X, Y, Z coordinates of the at least one vehicle.

18. The system of claim 12, wherein the at least one vehicle is at least one of a satellite, a pseudolite, a space shuttle, an aircraft, an airplane, an Unmanned Aerial Vehicle (UAV), a balloon, and a helicopter.

19. The system of claim 12, wherein the at least one spot beam is radiated as a fixed position beam.

20. The system of claim 12, wherein the at least one spot beam is radiated as a scanned beam.

21. The system of claim 12, wherein the processor calculates an estimate of the location of the user receiver device using an amplitude of the at least one spot beam.

22. The system of claim 12, wherein the user receiver device further comprises:

a local clock; and

a memory, wherein the memory is adapted to store successive spot beam identification information recorded over time.