RU2428714C2 - Universal high-performance navigation system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: navigation is performed using low earth orbit (LEO) satellite signals, as well as signals from two sources of ranging signals for determining associated calibration information, where a position is calculated using a navigation signal, a first and a second ranging signal and calibration information. Also possible is providing a plurality of transmission channels on a plurality of transmission time intervals using pseudorandom noise (PRN) and merging communication channels and navigation channels into a LEO signal. The method also involves broadcasting a LEO signal from a LEO satellite. Also disclosed is a LEO satellite data uplink. The invention also discloses various approaches to localised jamming of navigation signals.

EFFECT: high efficiency and ensuring navigation with high level of integration and security.

14 cl, 34 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates generally to navigation and, more specifically, to satellite navigation methods.

BACKGROUND OF THE INVENTION

The effectiveness of the navigation system can be determined by the distribution of errors in the navigation measurements (for example, accuracy) performed by the system. The effectiveness of the system may also depend on its ability to promptly alert users when it should not be used (for example, reliability). Efficiency can also be measured by the amount of time that the navigation system requires for the first position determination after a cold start (for example, the time before the first position determination). In addition, the effectiveness of the system may depend on the length of time or certain circumstances in which the specified performance parameters are within the specified limits (for example, availability).

Unfortunately, communication navigation signals provided by various existing navigation systems often do not provide satisfactory system performance. In particular, signal strength, bandwidth, and geometric factors for such navigation signals are generally insufficient to meet the needs of many demanding applications.

Existing navigation approaches based, for example, on signals from the Global Positioning System (GPS), often provide insufficient signal strength or have insufficient geometry to easily penetrate buildings or into the space between urban houses. Such signals may also be subject to intentional interference in hostile environments and may interfere with their use in emergency situations. Other navigation approaches based, for example, on a cell phone or television signals, usually lack vertical navigation information.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, a navigation method includes receiving a low Earth orbit (LEO) signal from a LEO satellite; decoding a navigation signal from a LEO signal; receiving the first and second ranging signals, respectively, from the first and second sources of ranging signals; determination of calibration information associated with the first and second sources of ranging signals; and calculating the position using the navigation signal, the first and second ranging signals and calibration information.

According to another embodiment of the invention, the navigation device includes an antenna configured to receive the LEO signal from the LEO satellite and receive the first and second ranging signals from the first and second ranging signals sources, respectively; a receiver processor configured to down-convert the LEO signal for further processing; and a navigation processor, configured to decode the navigation signal from the LEO signal and configured to calculate the position of the navigation device using the navigation signal, the first and second ranging signals and calibration information associated with the first and second sources of ranging signals.

According to another embodiment of the invention, the navigation device includes means for receiving a LEO signal from a LEO satellite; means for decoding the navigation signal from the LEO signal; means for receiving the first and second ranging signals, respectively, from the first and second sources of ranging signals; means for determining calibration information associated with the first and second sources of ranging signals; and means for calculating the position using the navigation signal, the first and second ranging signals and calibration information.

According to another embodiment of the invention, a method for supplying a LEO signal from a LEO satellite includes providing multiple transmission channels at a plurality of transmission time intervals, the transmission channels including a set of communication channels and a set of navigation channels; generating a first rangefinder overlapping signal based on pseudo-random interference (PRN) corresponding to the navigation signal; applying the first PRN-based ranging ranging signal to the first set of navigation channels; combining communication and navigation channels into a LEO signal; and LEO broadband from the LEO satellite.

According to yet another embodiment of the invention, the LEO satellite comprises an antenna configured to transmit the LEO signal from the LEO satellite; and a processor configured to provide a plurality of transmission channels for a plurality of transmission time intervals, the transmission channels including a set of communication channels and a set of navigation channels, generating a first rangefinder overlapping signal based on a PRN corresponding to the navigation signal, applying a first rangefinding overlapping signal based PRN to the first set of navigation channels and combining communication channels and navigation channels into a LEO signal.

According to another embodiment of the invention, the LEO satellite comprises means for providing multiple transmission channels over a plurality of transmission time intervals, the transmission channels including a set of communication channels and a set of navigation channels; means for generating a first ranging ranging overlapping signal based on the PRN corresponding to the navigation signal; means for applying the first rangefinder overlapping signal based on PRN to the first set of navigation channels; means for combining communication channels and navigation channels into a LEO signal; and means for transmitting the LEO signal from the LEO satellite.

According to another embodiment of the invention, a method for providing uplink data to a LEO satellite includes determining position information by using a LEO signal received from a LEO satellite, wherein the first ranging signal is received from a first ranging signal source and a second ranging a signal is received from a second ranging signal source; determination of the lead parameter by reference to the local clock and reference to the LEO satellite clock; preparing an uplink data signal including data for uplink transmission to be transmitted to the LEO satellite; uplink data signal synchronization with the LEO satellite using the lead parameter; and transmitting the uplink data signal to the LEO satellite.

In accordance with yet another embodiment of the invention, an uplink data transmission device includes an antenna configured to receive a LEO signal from a LEO satellite, receive first and second ranging signals from first and second ranging sources, and broadcast a data signal uplink to the LEO satellite; and a processor configured to determine position information using a LEO signal, a first ranging signal and a second ranging signal, determining a lead parameter by referencing the local clock and binding to the LEO satellite clock, preparing an uplink data signal including yourself data for uplink transmission to be transmitted to the LEO satellite and synchronization of the uplink data signal with the LEO satellite using the leading parameter Nia.

According to another embodiment of the invention, the uplink data transmission device includes means for determining position information using a LEO signal received from a LEO satellite, a first ranging signal received from a first sounding signal source, and a second ranging signal received from a second source rangefinder signal; means for determining the lead parameter by binding to the local clock and binding to the LEO satellite clock; means for preparing the uplink data signal to be transmitted to the LEO satellite; means for synchronizing the uplink data signal with the LEO satellite using the lead parameter; and means for broadcasting the uplink data signal to the LEO satellite.

According to yet another embodiment of the invention, the navigation signal comprises at least a portion of the LEO signal provided by the LEO satellite, a method for generating localized intentional interference to the navigation signal includes filtering the noise source into a plurality of frequency ranges to obtain a plurality of filtered noise signals in these frequency ranges moreover, the navigation signal is distributed across multiple channels of the LEO signal, while the channels are distributed over frequency ranges and multiple time intervals; creating a PRN sequence corresponding to the modulation sequence used by the LEO satellite to distribute the navigation signal over the channels; modulating filtered noise signals using a PRN sequence to obtain a plurality of modulated noise signals; and broadcasting modulated noise signals over the coverage area to provide multiple bursts of intentional interference corresponding to the navigation signal, wherein bursts of intentional interference are configured to substantially mask the navigation signal in the coverage area.

According to another embodiment of the invention, the navigation signal comprises at least a portion of the LEO signal provided by the LEO satellite, an intentional interference device configured to generate localized intentional interference to the navigation signal, includes a noise source configured to provide a noise signal; a plurality of filters configured to filter the noise signal into a plurality of frequency ranges to create a plurality of filtered noise signals in these frequency ranges, the navigation signal being distributed across multiple channels of the LEO signal, wherein the channels are distributed across frequency ranges and across multiple time intervals; a PRN sequence generator configured to provide a modulation sequence used by the LEO satellite to distribute the navigation signal over the channels; a plurality of oscillation generators configured to modulate the filtered noise signals using a PRN sequence to provide a plurality of modulated noise signals; and an antenna configured to broadcast modulated noise signals over the coverage area to provide multiple bursts of intentional interference corresponding to the navigation signal, wherein bursts of intentional interference are configured to substantially mask the navigation signal in the coverage area.

According to another embodiment of the invention, the navigation signal comprises at least a portion of the LEO signal supplied by the LEO satellite, the intentional interference device configured to create localized interference for the navigation signal includes means for filtering the noise source into a plurality of frequency ranges to provide a plurality of filtered noise signals in these frequency ranges, the navigation signal being distributed over a plurality of LEO signal channels, with the channels being distributed elen over frequency ranges and for many time intervals; means for creating a PRN sequence corresponding to the modulation sequence used by the LEO satellite to distribute the navigation signal over the channels; means for modulating filtered noise signals using the generated PRN sequences to provide multiple modulated noise signals; and means for broadcasting modulated noise signals over the coverage area to provide multiple bursts of intentional interference corresponding to the navigation signal, wherein bursts of intentional interference are configured to substantially mask the navigation signal in the coverage area.

The scope of the invention is defined by the claims, which are incorporated into this section by reference. A more complete understanding of the embodiments of the present invention, as well as the disclosure of its other advantages will be provided to specialists in this field of technology in the form of the following detailed description of one or more embodiments. In this case, links are given to the attached sheets of drawings, before which a brief description is given.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 contains a General view of an integrated highly efficient navigation and communication system in accordance with an embodiment of the invention.

FIG. 2 also contains a general view of the system of FIG. 1 in accordance with an embodiment of the invention.

Figure 3 illustrates the general scheme of the system of figure 1 in accordance with an embodiment of the invention.

Figure 4 illustrates an approach to realizing low Earth orbit signals in accordance with an embodiment of the invention.

FIG. 5 illustrates an autocorrelation function associated with low Earth orbit signals in accordance with an embodiment of the invention.

6 illustrates a decoding process of a military navigation signal component from a low Earth orbit in accordance with an embodiment of the invention.

7 illustrates a block diagram of a correlator of a navigation device in accordance with an embodiment of the invention.

Fig. 8 illustrates a decoding process of a commercial navigation component of a low Earth orbit signal in accordance with an embodiment of the invention.

9 illustrates an alternative decoding process for a commercial navigation component of a low Earth orbit signal in accordance with an embodiment of the invention.

10 illustrates a decoding process of a civil navigation signal component from a low Earth orbit in accordance with an embodiment of the invention.

11 illustrates a comparison between the navigation components of a low Earth orbit signal and GPS codes in accordance with an embodiment of the invention.

12 illustrates a block diagram of a device for intentional interference, which can be used to create localized intentional interference for navigation signals, in accordance with an embodiment of the invention.

Fig.13 contains a representation in the frequency and time domain of the device for intentional interference in Fig.12 in accordance with an embodiment of the invention.

Fig. 14 illustrates a pseudo-random interference generating process in accordance with an embodiment of the invention.

FIG. 15 illustrates a process for constructing uniformly distributed integers of a range of modules from a plurality of channel selection in accordance with an embodiment of the invention.

16 illustrates a process for converting a channel selection pool to a list of random non-overlapping channels in accordance with an embodiment of the invention.

FIG. 17 illustrates a frequency hopping circuit generated by the process of FIG. 16, in accordance with an embodiment of the invention.

Fig. 18 illustrates a block diagram of a receiver processor configured to receive and sample navigation signals for down-conversion in accordance with an embodiment of the invention.

Fig. 19 illustrates a block diagram of a navigation processor configured to process a ranging signal in accordance with an embodiment of the invention.

FIG. 20 illustrates the determination of various state parameters used by the navigation processor of FIG. 19, in accordance with an embodiment of the invention.

21 illustrates a block diagram of a tracking module configured to monitor a signal in accordance with an embodiment of the invention.

22 to 29 illustrate various examples of the use of a navigation system for performing navigation in various environments in accordance with various embodiments of the invention.

30 illustrates the universal frame structure of an uplink satellite in low Earth orbit in accordance with an embodiment of the invention.

FIG. 31 illustrates a ground infrastructure for uplink synchronization of data transmission for a satellite in low Earth orbit in accordance with an embodiment of the invention.

32 illustrates an implementation of a signal for transmitting low level data on an uplink in accordance with an embodiment of the invention.

33 illustrates a block diagram of a transmitter for supporting uplink data communications for a satellite in low Earth orbit in accordance with an embodiment of the invention.

Fig. 34 illustrates a block diagram of various uplink data components for a satellite in low Earth orbit in accordance with an embodiment of the invention.

For an understanding of the embodiments of the present invention and their advantages, it is best to refer to the following detailed description. It should be understood that similar item numbers are used to indicate similar elements shown in one or more of the drawings.

DETAILED DESCRIPTION

According to various embodiments, a system can be used that uses low Earth orbit satellites (LEO) to implement various navigation signals to provide navigation with a high level of integration. Passive rangefinder signals from LEO satellites and other non-LEO transmitters can be integrated into the system.

The reference network of observation stations can evaluate the clock deviation, signal structure and transmitter location, or the ephemeris of various platforms from which passive rangefinder signals are transmitted. This evaluation information (also called calibration information) can be transmitted to various navigation devices via a data line for communication with LEO satellites or other data lines.

To implement high-precision navigation, navigation devices can be configured to mix broadcast information and several different types of signals. The LEO broadcast signal can be implemented in the form of military, commercial and civilian navigation signals to ensure the separation of consumers between different navigation signals and to ensure the distribution of infrastructure costs. An integrated broadband uplink with a low probability of interception and detection (LPI / D) may also be proposed.

Turning now to the drawings, the images of which are solely for the purpose of illustrating embodiments of the present invention and not for the purpose of limiting it, FIG. 1 is a perspective view of an integrated highly efficient navigation and communication system 100 (also called iGPS) an embodiment of the invention. System 100 may include a navigation device 102 (also called user equipment, a user device, and / or a user navigation device) implemented using appropriate hardware and / or software for receiving and decoding signals from various space and ground ranging signal sources for navigation. Such signals may include, for example, satellite broadcast signals from GPS, LEO (e.g. Indium or Globalstar), wide-area amplification system (WAAS), European geostationary supplementary navigation system (EGNOS), multi-function satellite amplification system (MSAS), Galileo system, quasi-zenith satellite system (QZSS), and / or satellites of mobile satellite enterprises (MSV). Such signals may also include terrestrial broadcast signals from cellular towers, television towers, WiFi, WiMAX, national vehicle infrastructure integration nodes (VII) and other relevant sources.

In the example of FIG. 1, the navigation device 102 may be configured to receive signals from a global positioning system (GPS) 106 (for example, protected and / or insecure GPS signals) from conventional navigation satellites. In addition, the navigation device 102 may also receive signals 104 from various satellites 108 in low Earth orbit (LEO). In this regard, each of the LEO signals 104 (also called iGPS signals) may be a composite signal including a communication signal 104A, a military navigation signal 104B, a commercial navigation signal 104C, and a civil navigation signal 104D. This implementation allows 108 LEO satellites to simultaneously serve military, commercial, and civilian users, and allows such users to share the costs of operating the system 100.

In one example, LEO satellites 108 can be satellites of an existing communications system (e.g., Iridium or Globalstar) that have been modified and / or modified to support the system 100 described herein. As also shown in FIG. 1, LEO satellites 108 may be configured to support inter-satellite link signals 110 between various LEO satellites 108.

Using GPS signals 106 and / or LEO signals 104, the navigation device 102 can accurately determine its position (and, accordingly, the position of the user associated with it). The calculated position data thus determined (and other data that may be required) can then be transmitted via the uplink to the LEO satellites 108 using the spread spectrum uplink described herein.

In addition, the navigation device 102 may be configured to receive and perform navigation using broadcast signals from other satellite and ground-based ranging signals, which may be required in certain embodiments. In addition, the navigation device 102 may be provided with an inertial measuring unit (IMU), for example a device with a microelectromechanical system (MEMS), to provide protection against intentional interference described herein.

The navigation device 102 may be implemented in any desired configuration, which may correspond to specific applications. For example, in various embodiments, the navigation device 102 may be implemented as a portable navigation device, a navigation device on a vehicle, a navigation device on an aircraft, or other type of device.

Figure 2 shows another General view of the system 100 in accordance with an embodiment of the invention. In particular, FIG. 2 shows LEO satellites 108 and GPS satellites 202 in orbit around the Earth. In addition, FIG. 2 further shows various aspects of the infrastructure subsystems of system 100. For example, system 100 may include a core network 204 configured to receive LEO signals or other ranging signals, GPS terrestrial infrastructure 206, and LEO ground infrastructure 208. It should be clear that in various embodiments of the system 100 may have other space and (or) ground components.

Figure 3 shows the General scheme of the system 100 in accordance with an embodiment of the invention. It should be understood that although many subsystems are shown in FIG. 3, not all such subsystems must necessarily be contained in all embodiments of the system 100.

As shown in FIG. 3, LEO satellites 108 travel at a high angular velocity relative to navigation devices 102 and the various ground subsystems shown. This rapid angular movement can contribute to the resolution by ground subsystems of the ambiguities associated with cyclicity. In addition, LEO signals 104 can be implemented with higher power than conventional navigation signals 106. In addition, LEO signals 104 can also allow penetration through obstacles or buildings.

LEO signals 104 may include a communication link for ranging and information signals to various ground terminals. As shown in FIG. 3, such terminals may include a geographically distributed core network 204 and navigation devices 102 (shown in this example as a cell phone, MEMS device, and car).

Various satellites are also shown, including GPS satellites 202, Galileo satellites 306, WAAS satellites 302, and QZSS / MSV satellites 304, each of which can be configured to broadcast ranging and information signals in a downlink to a reference networks 204 and navigation devices 102 in accordance with various embodiments.

It should be borne in mind that for clarity, some rangefinder signals are not shown in FIG. 3. For example, in one embodiment, all of the satellites depicted may be configured to broadcast to all navigation devices 102 and to a core network 204.

As also shown in FIG. 3, various ranging signals 318 from a plurality of ranging signals 310 can be monitored by the reference network 204 and navigation devices 102. The reference network 204 may be configured to characterize each source 310 of ranging signals to provide calibration information associated with each source of ranging signals. Such information may be transmitted to the LEO satellite 108 via a corresponding uplink data line 320, encoded by the LEO satellite 108 into one or more military, commercial or navigation signals 104B / 104C / 104D of the LEO signal 104, and transmitted by broadcast to the navigation devices 102 as component of the 104 LEO signal. Thereafter, the navigation devices 102 can use the calibration information to process the ranging signals 318 to perform navigation in combination with the ranging measurements made using the LEO signals 104.

In general, various transmitters can transmit temporal (and therefore rangefinder) characteristics. In this regard, for a universal source of ranging signals, the associated ranging signal can be received by the reference network 204 and navigation devices 102. The reference network 204 can determine the calibration information associated with the ranging signal and telemetry such calibration information to the navigation devices 102 via the uplink information line with 108 LEO satellites and / or land lines.

For example, FIG. 3 shows GPS signals 106 received by one of the ranging signal sources 310 implemented as a WiFi node. If the ability to measure the time characteristics (which is equivalent to the rangefinding characteristics, if multiplied by the speed of light) of the specified attributes of the WiFi signal is implemented in the GPS receiver, then this receiver can simultaneously measure the reception time of WiFi and GPS signals. You can calculate the difference between these values, make a reference to the time and transmit the core network 204 to provide calibration information associated with the WiFi node. In response to receiving a GPS signal 106 and other type of ranging signals 318, additional calibration information can be determined by the reference network 204. In each case, the reference network 204 can telemetry in real time the calibration information associated with the WiFi node, the navigation devices 102 via the LEO satellite 104 on the uplink 320 and using the LEO signal 104 (for example, over space lines). Calibration information can also be provided to land-based navigation devices 102. Moreover, each source 310 of ranging signals does not need to be within the visibility of all nodes of the reference network 204, if there is a network 316 (for example, the Internet) between different ground nodes.

As stated above, LEO satellites 108 may be implemented as communications satellites (eg, Indium or Globalstar satellites) that have been modified and / or altered as described herein to support the navigation characteristics of system 100. Table 1 below and 2 contain various characteristics of Indium communications satellites and Globalstar communications satellites that can be used as 108 LEO satellites in accordance with various embodiments:

Table 1 Based on GSM cell phone architecture Both FDMA and TDMA Channel Separation 41.667 kHz 10.5 MHz downlink frequency band 40% quadrature phase modulation according to the law of the root of the raised cosine at 25000 r / s 90 ms frame Time intervals: (1) downstream simplex, (4) 8.28 ms upstream duplex; (4) 8.28 ms downstream duplex

table 2 Based on CDMA IS-95 Cell Phone Architecture Both FDMA and CDMA Channel Separation 1.25 MHz 16.5 MHz downlink frequency band Straight Hole Repeater

In one example where Indium communications satellites are used to implement 108 LEO satellites, Indium communications satellite flight computers can be reprogrammed with appropriate software to facilitate navigation signal processing. In another example of the implementation of 108 LEO satellites, Globastar communication satellites are used, the direct-hole satellite architecture allows ground equipment to be upgraded to provide many new signal formats.

In embodiments where the LEO satellites 108 are implemented using communications satellites, communications satellites may be configured to support communications signals as well as navigation signals. In this sense, such navigation signals can be implemented to take into account various factors, such as suppression of multipath propagation, accuracy of ranging, cross-correlation, immunity to intentional and random interference, and security, including selective access, measures to counter radar traps and a low probability of interception.

Figure 4 shows an approach to the implementation of 104 LEO signals in accordance with an embodiment of the invention. In particular, blocks 410, 420, and 430 of FIG. 4 illustrate the structure of signals transmitted and received by LEO satellites 108 to provide support for communications and navigation signals, wherein LEO satellites 108 are implemented using existing Indium communications satellites. In blocks 410, 420, and 430, the frequency is plotted along the horizontal axis, time flows in the direction deep into the page, and the power spectral density is plotted along the vertical axis.

In one embodiment, the LEO satellite 108 can be configured to support multiple channels implemented as multiple transmission intervals 402 and multiple reception intervals 404 formed by time division multiple access (TDMA) on a 90 ms wide frame and then formed on frequency division multiple access (FDMA) type on a 10 MHz band. It should be understood that each channel can correspond to a certain transmission or reception interval in a frame represented in a certain frequency range. For example, in one embodiment, LEO satellite 108 can be implemented to support the transmission of approximately 960 channels with 240 frequency bands providing 4 time slots per frame (e.g., 240 frequency bands × 4 time slots = 960 channels).

As shown in block 410, some of the transmission intervals 402 and reception intervals 404 may relate to existing communication systems (for example, in FIG. 4 this is shown as telephone calls 440). The transmission intervals 402 used may correspond to the data provided by the communication signal 104A of the LEO signal 104 transmitted by the LEO satellite 108.

It should be borne in mind that in the embodiment shown in block 410, many transmission intervals 402 remain unused. In accordance with various embodiments of the invention, unused bandwidth of unused transmission intervals 402 can be used to support navigation signals in accordance with what is described herein.

As shown in block 420, a rangefinder pseudo-random interference (PRN) signal 422 may be introduced into each of the remaining unused transmission intervals 402. The rangefinder overlap signal 422 can be controlled at low average power on a per-channel basis, but the aggregate rangefinder overlap signal 422 has high power to overcome intentional interference. In contrast, at block 430, a rangefinder overlapping signal 422 is implemented using a narrow beam of maximum power generated by LEO satellite 108.

In one embodiment, the rangefinder overlapping signal 422 may be implemented using a combination of frequency hopping and forward PRN. For the frequency hopping component, a subset of frequencies on a pseudo-random basis for each burst can be selected. Then, in each burst, data bits are also selected on a pseudo-random basis.

In one embodiment, telephone calls 440 may be given priority over a transmission interval 402 over a rangefinder overlapping signal, with the rangefinding overlapping signal 422 being almost unaffected by rare missed or distorted bursts. In another embodiment, rangefinder overlapping signal 422 may be given priority in the interval 402 over telephone calls 440, while rare missed or distorted bursts are also almost unaffected by telephone calls 440.

In one embodiment, the rangefinder overlapping signal 422 may be implemented with the widest possible bandwidth that only frequency range allocation rules allow. In this case, all available channels can be used, and various frequency, time, or code division multiple access (CDMA) methods can be used to create a downlink signal that looks like flat white noise if the user does not know the code. Such uniformity produces a signal that is well suited to ensure accuracy, immunity to intentional interference and suppression of multipath propagation. Cross-correlation can be minimized using the appropriate encryption algorithm, the implementation of which provides fast processing of the digital signal in the navigation device 102.

In one embodiment, the LEO signal 104 may be implemented as a complex signal s (t) versus time t, as shown in the following equation:

In the above equation, A is the signal amplitude, n is the symbol index, p is the direct sequence pseudo-random noise value, which can be ± 1, h is the symbol impulse response, m is the channel frequency index, f ₀ is the spread spectrum broadcast range, and N is the number of channel frequencies forming the spread spectrum broadcast range.

In another embodiment, in which the LEO satellites 108 are implemented as Globalstar system satellites, a low-power direct sequence code that is orthogonal to telephone traffic can be provided on each of the 1.25 MHz channels.

5 shows an autocorrelation function 502 that can be implemented by a navigation device 102 for connecting to a LEO signal 104 in accordance with an embodiment of the invention. In Fig. 5, τ is the autocorrelation argument, R is the autocorrelation function of the main impulse response of the symbol according to the law of 40% of the root of the raised cosine, N is the number of channels allowed by the range allocated to the 108 LEO satellite (for example, a maximum of 240 in one embodiment), f ₀ is the permissible frequency band (equal to the number N times the distance between the channels, which gives f ₀ = [41.667 kHz] N in one embodiment), and φ _m is the satellite phase shift for each channel.

In addition, FIG. 5 shows graphs 504 and 510 of the autocorrelation function 502 at various scales. Graph 504 shows the envelope 506 of the autocorrelation function 502 formed by the effective correlation length of the direct sequence data at 25 kilo-counts per second. In this embodiment, autocorrelation is formed by a combination of broadband channels divided by 41.667 kHz. For example, for broadcast transmission with a width of 10 MHz, the effective length of the direct sequence chip may be the length of the Y code, namely 30 m. For comparison, the rough code / detection code (C / A) 512 GPS and military (M) are also shown on graph 510 Code 514 GPS. As shown in graph 510, the side lobes of the autocorrelation function 502 are as easy to control as the lobes of the GPS M code 514. In this sense, the side lobes of the autocorrelation function 502 are either greatly attenuated or clearly distinguishable.

As described above, the LEO signal 104 may include various navigation signals, including a military navigation signal 104B, a commercial navigation signal 104C, and a civil navigation signal 104D. In addition, navigation devices 102 may be configured to decode one or more of these signals for navigation.

For example, FIG. 6 shows a decoding process of a military navigation signal 104B from a LEO signal 104 in accordance with an embodiment of the invention. It should be borne in mind that the process of FIG. 6 may be performed by the navigation device 102 in response to receiving the LEO signal 104.

In various applications, it is desirable to implement a military navigation signal 104B in the form of a powerful signal to overcome possible deliberate interference. Accordingly, as shown in step 1 in FIG. 6, the LEO signal 104 may include several parallel channels 602 (12 channels shown in FIG. 6) configured to carry the military navigation signal 104B. In one embodiment, a pseudo-random process can be used to determine the specific channels 602 involved for each burst of broadcast transmission from LEO satellites 108. In addition, in the step of FIG. 6, for each parallel burst on channels 602, a quadrature phase modulation (QPSK) character string 604 is shown, with the time axis passing through the page. The quadrature phase modulation symbols 604 are modulated by coding for a direct PRN sequence and also exhibit bias and rotation based on their frequency shift in the LEO signal 104.

In step 2 of FIG. 6, PRN coding is de-expanded by rotating each burst into the main frequency band, subtracting the interchannel offset, and removing the direct PRN sequence circuit to create a series of bursts carrying data associated with the military navigation signal 104B, which is represented by modified QPSK characters 606.

In step 3 of FIG. 6, data with a low transmission rate is demodulated in accordance with the set M of possible orthogonal macro symbols 608. If quarter-cycle ambiguities occur from QPSK modulation, then the ambiguities and macro symbols together may not be exactly orthogonal. After evaluating the data by means of a hard decision algorithm, the estimated data is deleted, after which only the unmodulated carrier 610 remains.

In step 4 of FIG. 6, the carrier is averaged over the entire burst and then over each channel. As a result, an in-phase quadrature measurement 612 of the instantaneous tracking error can be obtained. The phase-locked loop (PLL) system of the navigation device 102 is then used to track the satellite carrier.

FIG. 7 is a block diagram of a correlator of a navigation device 102 that can be used to perform the process of FIG. 6 in accordance with an embodiment of the invention. The numerically controlled oscillator 702 generates a carrier that downconverts the incoming LEO signal 104 (for example, received through the antenna of the navigation device 102) to a modulating signal 714. The modulating signal 714 goes to the upper path 704, which performs dot-code carrier tracking. The modulating signal 714 also arrives at the lower path 706, which provides differential detection.

On the lower path 706, a bank of synthesizers 708 and PRN generators 710 repeats each channel of the LEO signal 104. On the upper path 704, the repeated signals 712 are mixed with a modulating signal 714 to remove any code and phase rotation separately for each channel. Hypothesis generator 716 calculates a signal associated with each of the possible macro-symbols 608 and quarter-cycle ambiguities, if any. The processor 718 uses the maximum a posteriori MAP algorithm to obtain an estimate of 720 data indicating which of the macro symbol hypotheses is the most plausible. As shown in the drawing, an estimate of 720 data is supplied to the lower path 706 for use in differential detection. To perform point detection in the upper path 704, the processor 718 deletes this data and provides the resulting bursts to an adder 722, which integrates the aggregate bursts over time to obtain a common-mode-quadrature tracking error 724.

On the lower path 706, the repeated signals 712 are further modulated by a differential block 726 and a data generator block 728 (using an estimate of 720 data received from the upper path 704). As shown in the drawing, the resulting modulated signals are added together to form a composite copy of the differential signal 730, which is mixed with the modulating signal 714 and to the summing unit 732 for time averaging in order to obtain a differential discriminator 734. Accordingly, provided that the carrier is fixed and the averaging interval is sufficient, the differential discriminator 734 provides a criterion for instant tracking error.

FIG. 8 illustrates a decoding process of a commercial navigation signal 104C in a LEO signal 104 in accordance with an embodiment of the invention. It should be borne in mind that the process of FIG. 8 may be performed by the navigation device 102 in response to receiving the LEO signal 104.

As shown in the drawing, the process of FIG. 8 is similar to the process of FIG. 6, and steps 1-4 of FIG. 8 generally correspond to steps 1-4 of FIG. 6. However, it must be taken into account that in the process of FIG. 8, fewer 802 channels are used (for example, 2 channels in the illustrated embodiment) compared to channels 602 in FIG. 6. Due to the smaller number of channels 802 used, the commercial navigation signal 104C in the LEO signal 104 can be implemented with less power and less bandwidth than the military navigation signal 104B.

FIG. 9 shows an alternative decoding process of a commercial navigation signal 104C in a LEO signal 104 in accordance with an embodiment of the invention. As shown in the drawing, the process in FIG. 9 is similar to the process in FIG. 8, and steps 1-2 in FIG. 9 generally correspond to steps 1-2 in FIG. 8. However, in step 3 of FIG. 9, it is assumed that downlink data (e.g., calibration information) may be received by the navigation device 102 other than the LEO signal 104 (e.g., via a communications link with core network 204 or with one or more nodes 310 shown in Fig.3). Then, in steps 4 and 5 in FIG. 9, further processing can be performed, respectively, similarly to steps 3 and 4 in FIG. 8. The inclusion of step 3 in the process of FIG. 9 allows for a higher sensitivity when in the room. In this sense, the navigation device 102 can obtain a reliable presentation of the downlink data from one or more reference stations of the core network 204 without requiring the navigation device 102 to perform the deletion operation of the downlink and / or quarter cycle, which reduces the amount of processing required from the navigation device 102, and processing gain.

Figure 10 shows the decoding process of the civil navigation signal 104D in the signal 104 LEO in accordance with an embodiment of the invention. In various embodiments, the use of civilian navigation signal 104D may generally be focused on carrier-only navigation. As a result, the civilian navigation signal 104D may be implemented with a relatively narrow bandwidth (e.g., approximately 1 MHz) and may be publicly available. Moreover, the channels 1002 used for the civil navigation signal 104D can be implemented without significant spreading of the spectrum. In this sense, it should be borne in mind that the channels 1002 shown in step 1 in FIG. 10 are grouped close to each other compared to the channels 602 and 802 shown in step 1 in each of FIGS. 6, 8 and 9. It should be noted mind that the action of steps 1-4 in FIG. 10 can be understood based on the actions of steps 1-4 in FIG. 6 previously discussed.

Based on the foregoing discussion, it should be understood that in some embodiments, military, commercial, and civilian navigation signals 104B, 104C, and 104D in the LEO signal 104 can be implemented with the following parameters shown in Table 3:

Table 3 Signal Power Bandwidth Military Maximum Maximum Commercial Moderate Big Civil Moderate Moderate

In another embodiment of the invention, the system 100 can be implemented in such a way as to allow the military use of a military navigation signal 104B and at the same time prevent the use of commercial and (or) civil navigation signals 104C and 104D for opponents in a certain area of operation, without violating the use of commercial and civil navigation signals 104C and 104D out of range.

For example, in one embodiment, decoding of a commercial navigation signal 104C may be subject to the use of a distributed encryption key, which may be allowed to lose effect in the area of operations. In another embodiment, the broadcast of the commercial navigation signal 104C by the LEO satellites 108 may be selectively interrupted in the coverage area (for example, individual narrow beams from the LEO satellites 108 can be independently disabled).

In another embodiment, the commercial navigation signal 104C and / or the civilian navigation signal 104D may be locally suppressed in the coverage area. In this sense, FIG. 11 shows a comparison between the military navigation signal 104B, the civilian navigation signal 104D and the GPS C / A code 512 and the GPS M code 514.

As shown in FIG. 11, GPS GPS C / A code 512 can be drowned for military purposes by drowning the C / A code frequency range. As also shown in FIG. 11, the civilian navigation signal 104D can be considered as a subset of the military navigation signal 104B in both power spectral density and bandwidth. If the rangefinder overlapping signal 422 is implemented using FDMA and TDMA, then it can be seen that the civilian navigation signal 104D manifests itself in bursts with frequency hopping, as shown in FIG. 11.

12 is a block diagram of an intentional interference device 1200 that can be used to perform localized jamming of civil and commercial navigation signals 104C and 104D in accordance with an embodiment of the invention. As shown in FIG. 12, a white noise source 1202 (eg, created by Brownian motion) is processed by a filter 1204 to produce a noise signal 1206 with a bandwidth corresponding approximately to the transmission channel of the LEO satellite 108.

The military receiving device 1208, the generator 1210, and the oscillation generators 1212/1214 are configured to provide a plurality of channels 1216 corresponding to the currently available frequency of the civilian navigation signal 104D determined by a given, publicly accessible civilian PRN sequence. Channels 1216 are used to modulate the noise signal 1206, which is then upconverted using additional reduced components to emit bursts of intentional interference at precisely those times, of such duration and frequency, that correspond to the civilian navigation signal 104D received from 108 LEO satellites as part of the 104 LEO signal. It should be borne in mind that the above approach can also be used to interfere with the commercial navigation signal 104C, which may be required in certain implementations.

FIG. 13 is a representation in the frequency and time domains of operation of the intentional interference device of FIG. 12 in accordance with an embodiment of the invention. As shown in FIG. 13, the individual noise bursts 1302 generated by the intentional interference device 1200 are concentrated in a narrow frequency range 1304 corresponding to the civilian navigation signal 104D. At the same time, the components of the military navigation signal 104B (represented by dark rectangles 1306) actually remained unchanged and are completely available for military operations.

The generation of a rangefinder overlapping signal 422 in the LEO satellite 108 is described below with reference to FIGS. 14-17. Here, the various processes described in relation to FIGS. 14-17 can be performed by respective processors of the LEO satellite 108. In addition, the LEO satellite 108 may, by means of appropriate software and hardware, be capable of modulating and broadcasting communication signals (eg, bursts of telephone signals) in QPSK format.

On Fig shows the approach to the generation of pseudo-random interference in accordance with an embodiment of the invention. In the embodiment of FIG. 14, a counter based pseudo random number generator 1400 is used. In this sense, counter value 1402 is combined with a 128-bit encryption session key 1404 to provide a 128-bit cipher. By associating the counter value 1402 with the cipher 1406, various PRN elements of the ranging overlapping signal 422 can be constructed. In one embodiment, both the input value 1402 and the cipher 1406 can be implemented as 128-bit words using the Advanced Encryption Standard (AES) process.

As shown in FIG. 14, each counter value 1402 may include a type flag 1412 that defines each counter value 1402 as indicating either a channel selection (eg, if type flag 1412 is set to “1”) or direct sequence chips (eg if type flag 1412 is set to "0"). If the type flag 1412 is set to channel selection, then the other bits of the counter value 1402 may indicate the channels from the channel selection constellation 1408 for transmitting burst chips of broadcast data. If the type flag 1412 is set to a straight sequence, then the other bits of the counter value 1402 may correspond to the chip block index 1414 (for example, indicating a specific chip from the direct sequence chips 1410 to be transmitted) and burst counting 1416 (for example, indicating the frame number of a specific chip 1410 direct sequence to be transmitted).

In one embodiment, cipher 1406 can be used to select a value from a collection of 1408 random numbers to select a channel that is controlled by frequency hopping. In another embodiment, cipher 1406 may be used to select direct sequence chips 1410 that fill the QPSK data bits.

On Fig shows the process of building uniformly distributed from a range of modules from the totality 1408 channel selection in accordance with an embodiment of the invention. It should be borne in mind that the process of FIG. 15 can be applied in conjunction with the channel selection constellation 1408 described above with respect to FIG.

FIG. 16 shows a process for converting a channel selection constellation 1408 to a list of random non-overlapping channels in accordance with an embodiment of the invention. The process of FIG. 16 can be used for military navigation signal 104B, commercial navigation signal 104C and civil navigation signal 104D by selecting various parameters for M and N (shown in FIG. 16) in accordance with the values given in the following table 4:

Table 4 Signal Power (N) Bandwidth (M) Military Big 240 Commercial 1 or 2 > 100 Civil 1 or 2 8-32

On Fig shows a diagram of a frequency hopping generated by the process of Fig in accordance with an embodiment of the invention. As shown in FIG. 16, for successive bursts of transmission, various random channel selection (associated with respective transmission frequencies) is provided. It should be borne in mind that each frequency and chip are generated in a pseudo-random manner using a common key (for example, a 128-bit key) known in advance to the LEO satellite 108 and the navigation device 102.

FIGS. 18-21 show various aspects of a navigation device 102, which may be implemented in accordance with various embodiments of the invention. For example, FIG. 18 is a block diagram of a receiver processor 1800 of a navigation device 102 configured to receive and sample signals for down-conversion in accordance with an embodiment of the invention. As shown in FIG. 18, the navigation signals received by the antenna 1802 are filtered by multi-band filters 1804 (to preselect the desired frequency ranges), amplified by an amplifier 1806, and sampled by a sampling and latching circuit 1808 to provide raw digital high-frequency samples 1816.

The processor 1800 of the receiver also includes an oscillator 1810 and a synthesizer 1812, which can be used to synchronize the sample and the latching circuit 1808. In various embodiments, the sample rate of the sampling and latching circuits 1808 can be selected so as to prevent overlapping between the pseudonyms selected frequency ranges.

The processor 1800 of the receiver also includes an inertial measuring unit (IMU) 1814, implemented as a three-axis gyroscope and accelerometer MEMS, whose timestamps are synchronized with the general clock of the receiver, and can be used to provide unprocessed digital samples 1818 movement. It should be borne in mind that you can alternatively use other embodiments of the receiver to facilitate a single or multi-stage conversion with lower frequencies.

FIG. 19 is a flowchart of a navigation processor 1900 of a navigation device 102 configured to process rangefinder signals in accordance with an embodiment of the invention. As shown in FIG. 19, the Hilbert transform block 1902 converts the raw digital radio frequency samples 1816 to complex samples 1904. There are many tracking modules 1906. Each tracking module 1906 is associated with its own signal contained in complex samples 1904 and can be used to track or monitor satellite or ground-based sources of ranging signals.

The navigation processor 1900 provides commands 1908 to the tracking modules 1906 based on raw digital motion reports 1818 processed by the inertia processor 1916 and the generalized Kalman filter 1914. The auxiliary information 1908 biases the tracking modules 1906 by a small fraction of the wavelength. Raw measurements of the code and carrier phase 1910 from the tracking modules 1906 are read into the navigation pre-processor 1912, processed by a generalized Kalman filter 1914, and combined to provide a location notch 1918.

FIG. 20 shows various definitions of state variables used by the generalized Kalman filter 1914 of the navigation processor 1900 in accordance with an embodiment of the invention.

20, equation 2002 is a model of an integration and reset correlator. The output tracking error Δy is modeled by averaging over time T the difference between the actual phase and the phase predicted by the filter. Equation 2004 is a model of continuous updating over time of a complete navigation system, including an inertial unit, a clock, and all sources of synchronizing and rangefinding signals, both terrestrial and space. Variables of the state vector of the estimation operator are the accumulated phase of the correlator, the user's location, speed, angular orientation, the offset of the accelerometer, the offset of the gyroscope, the offset of the range, the offset speed of the range, the clock offset, the speed of the clock. Equation 2006 is a model of observations of the carrier phase, which shows the advance of the transfer of time to the user from the reference location, taking into account the geometry and atmospheric error.

FIG. 21 is a block diagram of one of the tracking modules 1906 in accordance with an embodiment of the invention. Tracking module 1906 receives the lead command 1908 to set the code phase and carrier for a specific rangefinder signal tracking by tracking module 1906. In the first processing step, the down converter 1950 rotates the carrier represented in complex samples 1904 to the main frequency band. Then, the down-converted signal 1952 is split and transmitted to the matched differential filter 1954 and to the matched point filter 1956.

The waveform for each rangefinder signal in view is either pre-stored in user memory or, as an option, is updated over the communication line with the 108 LEO satellite or with a network node (for example, with a cellular node, WiFi, WiMAX or VII). An update over the communication line allows you to expand the architecture and use it with almost any transmitted signal. This impulse response (similar to the PRN code for a GPS satellite) forms the basis for processing with a matched filter. The impulse response of a terrestrial signal, such as a cellular signal, WiFi, WiMAX, VII or a television signal, can be adjusted by storing the deterministic part of the reference signal. Any part of the signal that contains non-deterministic characteristics, such as unknown data, is excluded from the reference signal. Then, an impulse response of the structure of the reference signal is applied to each of these matched filters for implementation in a matched filter / correlator. As a result, filters 1954 and 1956 provide in-phase and quadrature representations of differential tracking errors 1958 and spot tracking errors 1960, respectively.

Various data structures may be used to encode ranging signal sources in accordance with various embodiments of the invention. For example, in one embodiment, the ranging signal may be represented by the following code:

struct ranging_signal {/ * generalized parameters of the source of ranging signals * / impulse_response broadcast_signal; / * signal structure from a source of ranging signals * /

double broadcast_frequency; / * source frequency of ranging ranging signals * / position broadcast_location; / * phase center of the source of ranging signals * / time broadcast_clock; / * clock offset of the source of ranging signals * /

};

In the above code, the shape of the reference signal is encoded as a parameter of the impulse response, the beginning of the reference time of which is tied to the broadcast clock. The broadcast frequency is the carrier frequency of the ranging signal source. The broadcast location is encoded as accurate ephemeris for spacecraft and as a Cartesian static coordinate for terrestrial ranging signal sources. The clock correction calibrates the source of the ranging signals with respect to system time based on UTC (for example, provided by the United States Naval Observatory (USNO)).

In various embodiments, the corresponding ground stations can be configured to decrypt the codes of the new ranging signals used by LEO satellites 108 in near real-time. In this regard, such ground stations can transmit decrypted codes to the navigation devices 102, thereby allowing the navigation devices 102 to navigate using virtually any signal, whether or not coordinated.

FIGS. 22-29 show various applications of the system 100 for navigating various services operating in different environments, in accordance with various embodiments of the invention. For example, FIG. 22 shows an application of a system 100 for providing indoor location determination in accordance with an embodiment of the invention. In this sense, it should be borne in mind that in FIG. 22, the navigation device 102 may be located inside a building or other structure.

As shown in FIG. 22, a navigation device 102 (eg, a portable user navigation device) can receive a LEO signal 104 directly from a LEO satellite 108 and additional ranging signals 318 from nodes 310. It is also shown that reference stations of a reference network 204 can also receive ranging signals 318. As indicated above, the reference network 204 may be provided with appropriate hardware or software for determining calibration information associated with each source 310 of ranging signals, before Vai on LEO satellite 108 uplink connection 320, encoded in the LEO satellite 108 signal 104 and transmitted through the LEO broadcast on the navigation device 102 as part of signal 104 LEO. Calibration information can then be used by the navigation devices 102 to process the ranging signals 318 to perform navigation in combination with a range measurement performed using the LEO signal 104. As a result, the navigation device 102 can use the LEO signal 104 and the ranging signals 318 to navigate.

The military navigation signal 104B (for example, provided by the LEO satellite 108 as part of the LEO signal 104) can, as well as the ranging signals 318 (for example, provided by the ranging signals sources 310, such as cellular or television signals) can be implemented as signals high power, able to penetrate building materials and reach the indoor navigation device 102. Accordingly, when using such high power signals in the approach shown in FIG. 22, the navigation device 102 can perform indoor navigation and quickly capture information after a cold start.

23 illustrates the application of a system 100 for providing indoor location determination in accordance with another embodiment of the invention. It should be borne in mind that the embodiment shown in FIG. 23 generally corresponds to the embodiment described above in FIG. 22. However, in the embodiment of FIG. 23, the navigation device 102 may also further communicate with the core network 204 or with nodes 312 or 314 via the network 316.

In addition, system 100 may be configured to utilize commercial signal processing with reference, as described with reference to FIG. 8. In this case, the commercial navigation signal 104C with lower power can be used to obtain a greater processing gain by transmitting a copy of the navigation data encoded in the commercial navigation signal 104C over the ranging signals 318. Since the navigation data is deleted in the process of FIG. 8, the width Tracking bandwidth can be significantly reduced.

In one embodiment, the navigation device 102 can determine the final notch of its position by generating a pseudorange vector for each source of ranging signals, k, followed by linearization with respect to the initial approximation for the user's position, x, and the user’s clock offset τ.

To refine the assessment of the user's position, the least squares method is used:

In another embodiment, system 100 may be implemented to provide highly accurate, highly reliable navigation. In this regard, FIG. 24 illustrates the use of the system 100 for navigating using GPS signals 106 and dual band LEO signals 104 and 104 'in accordance with an embodiment of the invention. In particular, FIG. 24 shows how a single frequency GPS L1 signal can be used with two different LEO signals 104 and 104 '(for example, with different LEO signals in different frequency ranges from different satellites 108 and 108' LEO) to ensure high quality navigation . In the embodiment of FIG. 24, enough carrier GPS signals 106 and LEO signals 104 and 104 'are not needed — the phases of the code from the signals need not be used. However, in another embodiment, both the code and the carrier are used to obtain maximum information from the available observable values.

24, the stations of the core network 204 can monitor GPS signals 106 and LEO signals 104 and 104 ′ and collect continuous phase information of the carrier to determine the exact orbit of GPS satellites 202 and LEO satellites 108. By using various 104 and 104 'LEO signals, the influence of the ionosphere can be eliminated and a carrier phase signal in which there is no influence of the ionosphere can be output. You can evaluate the cyclic ambiguities of all GPS satellites 202 and the LEO satellites 104 and 104 '(for example, depicted by ellipsoids 2402) using the high angular velocity of the 104 and 104' LEO satellites.

The position of the navigation device 102 (e.g., an airplane in this embodiment) can be determined in FIG. 24 in the same manner as described in detail above with reference to FIGS. 22-23. In particular, the entry below gives the k-th pseudorange measurement to determine the position of user x in the time interval m and with tropospheric zenith delay DZ, together with all the satellite ranging determinations, modeled as a continuous variable b.

Again, the least squares method is used to solve a system of equations for adjusting position, time offsets, and distance vector offsets. Despite the fact that measurements using 106 GPS signals are single-frequency and are subject to ionospheric bias, there is no ionospheric dependence in the resulting solution. Since measurements using 104 and 104 'LEO signals are devoid of ionospheric dependence, and since the 104 and 104' LEO satellites have a high angular velocity (compared to the practically zero angular velocity of GPS satellites 202), the geometry matrix is a full-rank matrix with the exception of the common mode between the clock and range offsets. This means that the offset estimates for GPS satellites 202 take values that correctly determine the user's position based on measurements devoid of ionospheric dependence using 104 and 104 'LEO.

25 illustrates the use of the system 100 for navigating using GPS signals 106 and one LEO signal 104 in accordance with an embodiment of the present invention. The orbit geometry of the only 108 LEO satellite within sight seeks to place the 108 LEO satellite on a trajectory that combines the position uncertainty ellipsoid 2502 with the local horizontal. In addition to the LEO signal 104 and GPS signals 106 by the navigation device 102 (for example, an airplane in this embodiment), a third signal 2504 (for example, from a Galileo satellite 306 or from another satellite) can also be used to determine its position.

The reliability of the navigation system can be measured by the ability of the system to alert users in a timely manner when it should not be used. In this sense, the risk of uncertainty can be described as the probability of an undetected dangerous anomaly of the navigation system. In one embodiment, system 100 can be implemented to provide high reliability using Autonomous Receiver Reliability Check (RAIM). In RAIM implementations, the navigation device 102 may be configured to control the self-consistency of measurements to detect navigation errors associated with failures of a different nature. The rapid movement of the 108 LEO satellites can facilitate such measurements.

Using RAIM, the least squares approximation error is used to test the chi-square hypothesis of system failure. In this case, you can use the following formula:

соответствует оценке положения. После определения каждой засечки положения навигационное устройство 102 может быть выполнено с возможностью вычисления измерения погрешности R. Если R меньше порогового значения, то считается, что система 100 работает надлежащим образом. Если R больше или равно пороговому значению, навигационное устройство 102 может выдать предупреждение о нарушении достоверности.In the above formula, φ corresponds to rangefinding measurements, H corresponds to the satellite geometry matrix, and

corresponds to the assessment of the situation. After determining each position notch, the navigation device 102 may be configured to calculate an error measurement R. If R is less than a threshold value, then the system 100 is considered to be operating properly. If R is greater than or equal to the threshold value, the navigation device 102 may issue a confidence violation warning.

FIG. 26 shows the effect of a ranging error on a position determination decision in accordance with an embodiment of the invention. Typically, rangefinder measurements are self-consistent. However, if one or more measurements are distorted or biased, this error can lead to a resultant solution from the truth. RAIM is able to detect an error because the inconsistency between the measurements is strongly correlated with the actual position error.

On Fig shows how the accuracy of the phase of the carrier system balances the geometry, which is characterized by dimming and reduced accuracy (DOP). In the two-dimensional case, the least squares approximation eliminates the vertical component of the position error. In one embodiment, the system 100 may preferably be implemented with centimeter accuracy of the carrier phase to ensure reliable navigation during dimming. As shown in the drawing, in the process of FIG. 27, a pre-prepared height map can also be used.

FIG. 28 illustrates the use of the system 100 for navigating using signals received directly from LEO satellite 108 and GPS satellites 202 in accordance with an embodiment. In Fig.29 shows a similar embodiment as in Fig.28, but with the addition of a network 316 and rangefinder signals 318, so that short interruptions of the LEO signals 104 and GPS signals 106 do not affect the continuity of service.

As described above, system 100 may be configured to support an uplink 320 for transmitting data from reference stations of a core network 204 to facilitate navigation by navigation devices 102 using signals 104B / 104C / 104D. The uplink 320 may also be supported by properly configured navigation devices 102. In this case, the uplink 320 may also be used to transmit any desired data from the core network 204 and / or navigation devices 102 to the LEO satellite 108 for subsequent broadcast as part of the communication signal 104A in the LEO signal 104.

Since GPS and UTC time are available from the exact time function of systems 100, it is possible to establish a one-way uplink protocol that provides an uplink 320 for data transmission without direct two-way synchronization. The time and frequency phasing of the uplink 320 data can be pre-set so as to arrive at the LEO satellite 108 in exact accordance with the instantaneous phase of the carrier and the frame structure on a symbol-by-symbol basis. With a suitable multiple use protocol, it is possible to share the uplink channel with many navigation devices 102. Such a multiple use protocol can be implemented by time, frequency, code, or any combination of the above. In one embodiment, the uplink 320 data may be in the form of an uplink with a spread spectrum with resistance to intentional interference and a low probability of interception and detection (LPI / D). In another embodiment, low power signals on the uplink 320 data may be summed over many symbols to extract the combined macro symbol from noise and provide an uplink with LPI / D.

FIG. 30 shows a generalized loop structure for bursts 3002 of data on uplink 320 to LEO satellite 108 in accordance with an embodiment of the invention. In one embodiment, the uplink 320 data may be configured to support bursts of data on the uplink for approximately 240 channels at 414 bits per burst. In order to properly match the uplink data line 320 on a symbolic basis in one embodiment, the frame structure of the LEO satellite 108 can be pre-placed at rest (for example, in the absence of a time offset and a frequency offset from the main clock of the LEO satellite 108). In another embodiment, the reference station of the core network 204 may be configured to generate a corresponding clock signal for the uplink 320 for transmitting data to the LEO satellite 108. The meaning of this synchronizing signal is to pre-combine the frame structure for the data symbols in a burst relative to the UTC benchmark and GPS time.

On Fig shows the ground infrastructure for synchronization of the uplink 320 data transmission in accordance with an embodiment of the invention. In particular, the ground infrastructure in FIG. 31 includes a reference station of a core network 204 that can be used to combine the payload field 3104 of each data burst 3002. In one embodiment, the reference station may be configured to not broadcast during the portion of the burst allocated to payload 3104 (this time is reserved for navigation devices 102). In one embodiment, each of the navigation devices 102 may be authorized to transmit uplink one symbol in a specific time and frequency interval. Thus, each symbol (or each orthogonal bit in the frame structure on the QPSK uplink) is individually addressed by the navigation device 102, which knows its position and UTC / GPS time. Navigation devices 102 may be implemented using any suitable multiple use protocol, according to which bits in specific fields are allocated to navigation devices 102. For example, according to the CDMA protocol, multiple navigation devices 102 may even share the same bits.

In various embodiments, the uplink 320 data may be implemented with low-power signals. For example, in one embodiment, the uplink 320 may be implemented using a milliwatt level broadcast to transmit several data bits per second to the LEO satellite 108. If this power is distributed, for example, over a 10 MHz bandwidth, then the spectral density of the resulting power stream is acceptable for LPI / D applications. Such an implementation of the spread spectrum uplink 320 may also provide protection against intentional interference.

FIG. 32 shows an embodiment of a low level signal used for an uplink 320 data transmission in accordance with an embodiment of the invention. In one embodiment, the LEO satellite 108 may be configured to receive each bit in QPSK modulation along with background noise. Since QPSK can be synthesized from two orthogonal streams of binary phase shift keying (BPSK), Fig. 32 shows a simplified probability distribution of BPSK (a pair of biased Gaussian distributions). Typically, the detector in the demodulator of satellite 108 LEO makes a decision of "1" or "0" (indicated in this case as -1) based on the threshold value at zero, and the probability of error in the symbol is calculated by integrating the area under the Gaussian depending on the signal-to-noise ratio .

In one embodiment, the demodulator is considered as a hard amplitude limiter. When the signal-to-noise ratio is much less than unity, the central Gaussian curve shown in FIG. 32 is representative. The presence of a signal (i.e., a data bit) only slightly shifts the curve from one side to the other, but in general, the output signal is clogged with noise. However, by averaging many discrete samples, the LEO satellite 108 can detect the occurrence of a signal. Calculations known to those skilled in the art set the hard limiter loss to about 2 dB. In other words, with the exception of the effective loss of converting an analog signal to digital at a level of 2 dB, the input signal is completely preserved, even if the 108 LEO satellite was originally implemented as a communication satellite. The above approach is not limited to the specific implementation of the satellite 108 LEO.

In various embodiments, the processing of data bits may be performed by a core network 104, a navigation device 102, or on a LEO satellite 108. In another embodiment, specially designed demodulators with a multi-bit high-frequency block can be used to eliminate 2 dB of hard limiter losses in 108 LEO satellites implemented with analog straight hole configurations.

33 is a block diagram of a transmitter 3300 configured to support an uplink 320 data transmission in accordance with an embodiment of the invention. In this regard, it should be borne in mind that the transmitter 3300 may be an integral part of the reference station of the core network 204 or an integral part of one or more navigation devices 102. For example, in one embodiment, the transmitter 330 may be part of a Pocket Defense Advanced GPS Receiver ( DAGR), cell phone or any other compact, cheap device. Such navigation devices 102 may preferably be configured to enable the sending of text messages and status messages with a short delay time from anywhere in the world on the uplink 320 for further broadcasting on the communication signal 104A.

As shown in FIG. 33, the position and clock of the navigation device 102 (e.g., provided in accordance with the navigation solution 3302) and the position and offset of the clock of the LEO satellite 108 (e.g., provided by the navigation pre-processor 1912) are subtracted from each other to obtain an a priori advance parameter τ ₀ used, as shown in the drawing, block 3308 calculation of the lead. In this case, τ ₀ corresponds to the lead time by which a separate data bit d _nm must be transmitted for arrival at the LEO satellite 108 at exactly the right time and with exact phasing.

The lead parameter then controls the synthesis of the signal in the baseband processor. The data to be transmitted on the uplink is encoded and encrypted at block 3304 in accordance with the preferences of the user. Block 3306 data modulator generates pulses of 40% of the root of the raised cosine, which are modulated by the corresponding data bit, PRN-code of the direct sequence and the frequency offset of the channel generated by block 3310 PRN-generator and block 3312 synthesizer. Any required number of channels can be processed in parallel. The signals are summed, converted with increasing frequency (in this case, up to 100 MHz), converted to real form, converted from digital to analog and converted with increasing to high frequency for broadcast transmission, as shown by blocks 3316-3324 in Fig. 33.

For compact and low-power operation, the component of the main frequency band can be implemented in such a way as to be in a modified real section of the main range in the DAGR or cell phone. In one embodiment, antenna 3324 may also be used for GPS signals in a DAGR or in a cell phone. In one embodiment, the power consumption and dimensions of the uplink broadcast equipment may be implemented to be suitable for a telephone or for a compact device. For example, in one embodiment, such transmitting equipment can be implemented based on the RF2638 chip supplied by RF Micro Devices, which provides a high-frequency output power of 10 dB with respect to 1 mW and requires 25 mA at a voltage of 3 V.

FIG. 34 is a block diagram of various components 3400 of a LEO satellite 108 configured to support an uplink 320 data transmission in accordance with an embodiment of the invention. In one embodiment, the LEO satellite 108 may be configured to receive pulses with data bits through an antenna 3402 and a receiver unit 3404 and populate the internal frame structure with the resulting solution, namely +1 or -1. The PRN generator block 3406 instructs the frequency hopping on the uplink according to a pattern previously known to both the navigation device 102 and the LEO satellite 108. The PRN generator block 3408 also applies a direct sequence PRN code to the incoming bits. The waveforms associated with the various macro-symbol hypotheses (provided by the hypothesis generator block 3410) are mixed with the incoming signal and then processed by a processor 3412 (for example, as described above with respect to processor 718) to provide a resulting data message 3414. As in the case of the LEO signal 104, also described herein, orthogonal coding provides an excellent energy-to-noise spectral density (Eb / N0) value for the data uplink 320.

The uplink 320 also contains an integrated ranging signal due to modulation with PRN coding. Additionally, an automatic delay delay adjustment (DLL) system may be provided in the LEO satellite 109 to estimate the distance from the navigation device 102 to the LEO satellite 108. As a result, it is possible to perform reverse triangulation and use a plurality of LEO satellites 108 to passively triangulate the position of the navigation device 102.

System 100 can advantageously be used to provide the required performance in various applications. For example, in one embodiment, system 100 may be implemented to provide fast, directional key exchange. Using public-private key infrastructure techniques in system 100, navigation devices 102 can be authenticated using a two-way data line before transmitting encrypted exchange keys over a wireless line. In this way, reliable control over a specific user, receiver, location and time of key change can be maintained.

In another embodiment, the system 100 can be implemented to obtain information about the situation with the combined forces of the enemy. In this case, the navigation devices 102 can share position information with other nearby friendly forces, and information about dangerous areas and the enemy’s location can be exchanged in real time.

In yet another embodiment, system 100 may be implemented for navigational communications and air traffic control. In this case, the navigation devices 102 can be performed on an aircraft (for example, instead of an antenna and a GPS board in a multi-mode receiver (MMR) of an aircraft) to provide a landing of category III, an integrated communication line, integrated automatic dependent monitoring and integrated air traffic control based on space data.

In yet another embodiment, system 100 may be implemented to support search and rescue operations. In this case, the navigation device 102 may be configured to provide global E911 performance for both military and civilian purposes. The LPI / D characteristics of the military version of the uplink 320 data transfer allow you to adapt the modified DAGR device for use in hostile conditions.

In another embodiment, system 100 may be implemented to support route redirection. In this case, controlled weapons can be given commands and they can be retargeted in real time using commands given by the modified DAGR device.

In yet another embodiment, system 100 may be implemented to support damage assessment of military equipment. In this case, information collected from people or from sensors can be quickly combined through an uplink 320 data transmission. In another embodiment, system 100 may be implemented to support the ability to combine weather correlated location information.

In yet another embodiment, system 100 can be implemented to provide a combination of measurements by the network of navigation devices 102 of intentional interference power, or good time, or frequency features in an intentional interference device to determine their exact location by triangulation.

In yet another embodiment, system 100 may be implemented to support narrow beam control. In this case, the scope of authority to control the power of the narrow beam can be delegated to the navigation devices 102. For example, if there is intentional interference, the navigation devices 102 may be configured to request a real-time increase in the broadcast power of the LEO signal 104. Such an implementation option can be made available to military and civilian users engaged in rescue operations, and the scope of authority is determined by state policy.

In yet another embodiment, system 100 may be implemented to support global text messaging in a cellular communication system. For example, in the navigation device 102 (for example, in a modified DAGR device or in a mobile phone), it may be possible to establish an uplink 320 for transmitting text messages to and from any place around the world.

The embodiments described above illustrate but do not limit the invention. It should be understood that numerous modifications and alterations are possible in accordance with the principles of the present invention. Accordingly, the scope of the invention is defined only by the following claims.

Claims (14)

1. A method of navigating, comprising the following steps:
receiving a signal from low Earth orbit (LEO) from the LEO satellite;
decoding the navigation signal from the LEO signal;
receive the first and second ranging signals, respectively, from the first and second sources of ranging signals;
determining calibration information associated with the first and second rangefinding sources;
calculate the position using the navigation signal, the first and second ranging signals and calibration information, and
receive a copy of the navigation signal over the cellular network; and
calculate the position using a copy of the navigation signal, the first and second ranging signals and calibration information. 2. The method according to claim 1, characterized in that the LEO signal comprises a communication signal and a navigation signal, wherein the LEO satellite is a communication satellite configured to provide a LEO signal. 3. The method according to claim 2, characterized in that the LEO satellite is selected from the group consisting of a satellite of the Iridium system and a satellite of the Globalstar system. 4. A method according to any one of the preceding paragraphs, characterized in that the navigation signal comprises a pseudo-random interference (PRN) signal encoded in multiple channels of the LEO signal. 5. The method according to any one of the preceding paragraphs, characterized in that the navigation signal is selected from the group consisting of a military navigation signal, a commercial navigation signal and a civil navigation signal. 6. The method according to any one of the preceding paragraphs, characterized in that at least one of the ranging signals is selected from the group consisting of a mobile telephone signal, a television signal and a global positioning system (GPS) signal. 7. The method according to any one of the preceding paragraphs, characterized in that the calibration information comprises a code timing, a carrier phase, data bits and a symbol phase. 8. The method according to any one of the preceding paragraphs, characterized in that the method is carried out by a device selected from the group consisting of a portable navigation device, a navigation device based on a vehicle and a navigation device based on an aircraft. 9. The method according to any one of the preceding paragraphs, characterized in that the implementation of the method is due to the presence of the encryption key of the navigation device. 10. A navigation device comprising
means for receiving a signal from a low Earth orbit (LEO) from a LEO satellite;
means for decoding the navigation signal from the LEO signal;
means for receiving the first and second ranging signals, respectively, from the first and second sources of ranging signals;
means for determining calibration information associated with the first and second sources of ranging signals;
means for calculating the position using the navigation signal, the first and second ranging signals and calibration information;
means for receiving a copy of the navigation signal over the cellular network; and
means for calculating the position using a copy of the navigation signal, the first and second ranging signals and calibration information. 11. The navigation device of claim 10, further comprising means for assessing the influence of the ionosphere using a single frequency signal L1 of the global positioning system (GPS). 12. The navigation device of claim 10 or 11, further comprising means for providing three-dimensional guidance of the automatic landing for the aircraft using the navigation signal and the first signal, the source of the first ranging signal being a satellite. 13. The navigation device according to any one of paragraphs.10-12, further comprising means for providing vertical guidance of the automatic landing using the navigation signal. 14. The navigation device according to any one of claims 10 to 13, further comprising means for performing autonomous receiver confidence control (RAIM).

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