JP2022119752A - Bit transition enhanced direct position estimation in global satellite system positioning - Google Patents

Abstract

To provide a method, a system, and a program product for bit transition improved direct position estimation (DPE) of a GNSS signal.SOLUTION: A method includes a step of receiving, in a GNSS receiver, signals from a plurality of different satellites in a plurality of satellite constellations. The method estimates a position, velocity, clock bias, and clock drift as GNSS receiver parameters, and optionally and if unknown, a receiver time. The method generates a model of received GNSS signals that is determined according to receiver parameters. As unique characteristics, the method includes synchronous processing of both a primary code and a secondary code in the model of the received GNSS signal, in addition to time delays, Doppler shifts, and other relevant parameters for positioning. Finally, when a secondary code of a specific signal is unknown, the method determines the combination of bit transitions that maximizes the optimization problem.SELECTED DRAWING: Figure 1

Description

The present invention relates to the field of Global Navigation Satellite System (GNSS) position determination in satellite-based global positioning systems.

Satellite-based positioning is the positioning of a GNSS receiver based on GNSS positioning data in signals such as data generated by the Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), Galileo, NaVIC, and BeiDou. , Velocity, and Time (PVT, Position, Velocity, Time) determination. A core signal for GNSS is a direct sequence spread spectrum signal synchronously transmitted by each satellite in the GNSS satellite constellation. A spread spectrum signal includes both a ranging code, also called a Pseudo Random Noise (PRN) spreading sequence, and a low speed data link that broadcasts the corresponding satellite ephemeris information.

Each GNSS receiver receives a GNSS signal and estimates the PVT from that signal. To this end, program logic working in concert with the GNSS receiver estimates ranging codes in the signal model to form a set of observables for each satellite from which the GNSS signal was received. The observables in the set are a set of ranges calculated from time delays in receipt of corresponding GNSS signals, called pseudoranges, and phase difference estimates, called carrier phase measurements between different GNSS signals. including. Calculating the PVT using the observables is a problem of solving a multilateration of multiple observables in the least-squares method.

Conventionally, calculating PVT is a two-step process. The first step in the process generates coarse estimates of synchronization parameters based on unreviewed received signal data. Additionally, this first step can include refinement of the coarse estimate using either a finer acquisition loop or a tracking loop. More precisely, in a first step an estimate of the time delay and Doppler shift is determined based on the spread spectrum signal received from the selected satellite. In the second step, called the "navigation solution", the GNSS observables are processed to estimate the PVT of the GNSS receiver.

In particular, modern GNSS signals include a secondary PRN code that complements the primary PRN code. The primary PRN code is a continuously repeating binary code with a high chipping rate, while the secondary PRN code is also a continuously repeating binary code, but with an order of magnitude relative to the chipping rate of the primary PRN code. With a difference it has a much lower chipping rate. Each chip of the secondary PRN code is multiplied by one period of the primary PRN code. The product of a primary PRN code and a secondary PRN code is commonly referred to as a multi-layer code. Although the secondary PRN code has several advantages and allows a significant improvement in GNSS receiver performance, the presence of the secondary PRN code complicates the acquisition step. The reason is that correct alignment of the secondary PRN code during the extended signal acquisition time requires additional processing resources in the GNSS receiver.

However, recent increases in computational power have eliminated the need for the two-step process determination of PVT and instead allow for a single-step Direct Positioning Estimation (DPE) from the received spread spectrum signal. It has become. In the DPE, program instructions running within the GNSS receiver integrate the code/carrier tracking loop and navigation solution into a single step. Importantly, DPE-implemented GNSS receivers have improved satellite acquisition and tracking and can deliver PVT under difficult conditions such as multipath propagation or weak signal and fading environments. In contrast to the traditional two-step process of position estimation, the DPE can extract and utilize useful information from weak GNSS signals while dealing with signal blockages. Therefore, the DPE can perform positioning even when the GNSS receiver is located where the satellite coverage is poor.

Embodiments of the present invention incorporate the aforementioned advantages of DPEs while incorporating two-step position estimation to provide novel and non-obvious methods, systems, and computer program products for bit transition-enhancing DPEs of GNSS signals. Addresses deficiencies in the techniques related to the concatenation of primary and secondary code in the process.

In one embodiment of the invention, a method for bit transition enhanced DPE of a GNSS receiver receives signals from a plurality of different satellites in a satellite constellation configured for use with GNSS at the GNSS receiver. Including. The method further includes synchronization with both primary and secondary codes from the received GNSS signals. Uniquely, the method further comprises identifying a plurality of bit transitions in each of said primary code and secondary code and aligning one of the bit transitions of each of said primary code and secondary code. including the determination of Finally, the method includes using the determined alignment of the bit transitions to correct the coarse positions determined for the primary code.

In one aspect of this embodiment, determining the alignment includes generating an extended cross ambiguity function for each signal's local code. Thus, a set of matrices of extended cross ambiguity functions correspond to a number of satellites within the coverage of the GNSS receiver. Also, each of the plurality of matrices of said extended cross ambiguity functions are then processed by a DPE utilizing the determined alignments at said bit transitions. As a result, each of the cross ambiguity function matrices is processed by the DPE considering not only position, velocity and time, but also secondary code alignment or possible bit transitions.

In another embodiment of the invention, a data processing system is configured for bit transition enhanced DPE of GNSS signals. The system includes a host computing platform having one or more computers each having memory and at least one processor. The system also includes a GNSS receiver coupled to the host computing platform. Finally, the system includes a DPE module containing computer program instructions. The computer program instructions, when executed on the host computing platform, receive at a GNSS receiver positioning signals from a plurality of different satellites in a satellite constellation configured for use with GNSS; extracting both a primary code and a secondary code from the positioning signal; identifying a plurality of bit transitions in each of the primary code and the secondary code; and identifying bit transitions in each of the primary code and the secondary code. determining an alignment of one of said bit transitions and using said determined alignment of said one of said bit transitions to correct a determined coarse position for said primary code.

Additional aspects of the invention will be set forth in part in, and in part will be obvious from, the description that follows,
or can be learned by practicing the present invention. Aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and illustrative only and are not limiting of the invention as claimed.
The present invention will now be described in detail with reference to the drawings.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. While the embodiments described herein are presently preferred, it should be understood that the invention is not limited to the precise arrangements and instrumentalities shown in the following drawings.

FIG. 1 is an illustration of a process for bit transition enhanced DPE of GNSS signals. FIG. 2 is a schematic diagram illustrating a host data processing system configured for bit transition enhancement DPE of GNSS signals. FIG. 3 is a flowchart illustrating a process for bit transition enhanced DPE of GNSS signals.

Embodiments of the present invention provide a bit transition enhanced DPE for GNSS signals. According to an embodiment of the invention both the primary code and the secondary code are extracted from the GNSS signal, and alignment of bit transitions is between said primary code bit transitions and said secondary code bit transitions. It is determined. A DPE function can then be calculated taking into account not only time, position and velocity, but also the alignment of the bit transitions determined for the primary code and the secondary code. Thus, improved accuracy can be achieved in the DPE for GNSS signals by considering the bit alignment of the secondary code with the primary code.

To further illustrate, FIG. 1 illustrates a process for bit transition enhanced DPE of GNSS signals. As shown in FIG. 1, GNSS signals 130 are received at GNSS receiver 120 from one of several different satellites 110 within a GNSS satellite constellation. As long as both primary code 140A and secondary code 140B are extracted from GNSS signal 130 and the bit transitions of secondary code 140B are orders of magnitude more frequent than the bit transitions of primary code 140A, the Alignment is detected. Similarly, coarse position 100A is determined based on amalgamation of primary code 140A with a local code (not shown) generated within GNSS receiver 120 .

A Cross-Ambiguity Function (CAF) 160 for one of several different satellites 110 is then determined based on the coarse position 100A in combination with the determined alignment 150 . The process is then repeated for additional GNSS signals 130 from different ones of the constellation's satellites 110 . Once a sufficient number of CAFs 160 have been calculated for each different satellite 110 , a sum 170 of CAFs 160 for each satellite can be calculated and DPE processed to produce a bit-aligned improved DPE 180 . The result of bit alignment refinement DPE 180 is position estimate 100B for GNSS receiver 120 .

The process described with respect to FIG. 1 may be performed within a data processing system configured to estimate position information in GNSS. In the following discussion, FIG. 2 schematically illustrates a host data processing system configured for bit transition enhancement DPE of GNSS signals. The system includes a host computing system having memory 230 and at least one processor 220 . The host computing system is communicatively coupled to GNSS receiver 210 via computer communications network 240 . For only some aspects of this embodiment, the host computing system is included as part of the GNSS receiver 210 .

GNSS receiver 210 receives GNSS signals from satellites in GNSS satellite constellation 200 and processes the GNSS signals according to the bit alignment refinement DPE performed by DPE module 300 . In this regard, DPE module 300 includes computer program instructions which, when executed in memory 230 by processor 220, are sent from particular satellites in satellite constellation 200 to GNSS receivers. locating common bit transitions between primary and secondary codes of a GNSS signal received in 210 and preprocessing the primary code with a local code generated in GNSS receiver 210; It is operable to generate a coarse position of the GNSS receiver 210 and then calculate the CAF of the GNSS signal taking into account said common bit transitions. The program instructions further determine the sum of the CAFs calculated for each GNSS signal received from different satellites in the constellation 200 to produce a fine position estimate for the GNSS receiver 210 by determining the Enabled to send the total value to the DPE.

In yet another illustration of the operation of the DPE module 300, FIG. 3 is a flowchart illustrating the process of bit transition enhancement DPE of GNSS signals. Beginning at block 310, a GNSS signal from a particular satellite within the satellite constellation is received at the GNSS receiver, and at block 320 a signal from the particular satellite is selected. Next, at block 330 replicas of both the primary and secondary local codes are generated, and at block 340 the CAF for the particular satellite signal is calculated. At block 350, initial coarse estimates of receiver position, velocity, and time are used to reduce the size of the computed CAF matrix by selecting only relevant regions.

Importantly, in block 360 the range of possible bit transition alignments between the primary code and the secondary code is determined, for example, by testing different alignment estimates for each of the codes, and determining the primary code and by selecting the most correlated estimate to align the secondary code. Next, at block 370, an extended CAF may be generated for the range of bit transition alignments identified as alignments between the primary code and the secondary code. In this regard, the extended CAF has a three-dimensional structure: time delays, Doppler shift values, and bit transitions. Therefore, the bit transitions of the extended CAF are preserved during position estimation for subsequent use. Next, at decision block 380 , if more GNSS signals are received from different satellites in the satellite constellation, the process returns to block 310 . However, if at decision block 380 no further GNSS signals need to be received to calculate the fine position of the GNSS receiver, then at block 400 the DPE is used to generate a fine position estimate for the GNSS receiver. is executed. Specifically, at block 400, the optimized CAF outputs for each satellite are combined, including bit alignment, to produce a loss or cost function, which in turn produces a position estimate. is optimized for position and velocity to

The present invention may be implemented as a system, method, computer program product, or any combination thereof. A computer program product includes a computer readable storage medium or medium having computer readable program instructions that cause a processor to perform features of the present invention. A computer-readable storage medium is a tangible device that retains and stores instructions for use by a device to execute the instructions. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, or any combination of the above media.

Computer-readable program instructions herein can be downloaded from a computer-readable storage medium to a separate computing/processing device or over a network to an external computer or storage device. The computer readable program instructions may be executed as a stand-alone software package, wholly on the user's computer, partly on the user's computer and partly on a remote computer, or wholly on a remote computer or server. executed on. Features of the present invention are described herein with reference to flowchart illustrations and/or block schematic diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. Each block in the flowchart illustrations and/or block schematic diagrams, and combinations of blocks in the flowchart illustrations and/or block schematic diagrams, are implemented by computer readable instructions.

When such computer readable instructions are provided to a processor of a general purpose computer, special purpose computer or other programmable data processing apparatus, the instructions executed by such computer or other programmable data processing apparatus processor are: Means are created to implement the functions/acts identified in the flowchart blocks and/or block schematic diagram blocks. Such computer readable instructions may also be stored in a computer readable storage medium that instructs a computer programmable data processor and/or other device functioning in some fashion. . Accordingly, a computer-readable storage medium having instructions stored thereon encompasses an article of manufacture that includes instructions that implement the functions/acts identified in the flowchart blocks and/or block schematic diagram blocks.

The computer readable instructions described above are loaded into and executed on a computer, other programmable data processing apparatus or other device, and executed by the computer. make a process. As a result, instructions executing on a computer, other programmable data processing apparatus, or other device perform the functions/acts identified in the flowchart blocks and/or block schematic diagram blocks.

The flowcharts and block schematic diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block schematic diagram represents a module, segment or portion containing one or more executable instructions for implementing a particular logic function. In alternative implementations, the functionality noted in the blocks results from the instructions presented in the accompanying drawings. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or all blocks may be executed in the reverse order, depending on the functionality required. Each block in the block schematic diagrams and/or flowchart illustrations, and combinations of blocks in the block schematic diagrams and/or flowchart illustrations, can be implemented by a dedicated purpose hardware-based system, which system may be implemented by a specific purpose hardware-based system. to implement the functions or acts of by executing a combination of special purpose hardware and computer instructions.

Finally, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include plural forms unless the context clearly dictates otherwise. When the terms "includes" and/or "including" are used herein, the presence of the stated features, integers, steps, steps, elements and/or parts does not exclude the presence or addition of one or more other features, integers, steps, steps, elements, components and/or combinations thereof.

The same structure, material and operation as the elements performing the function including all means or all steps in the following claims or equivalents thereof are claimed specifically recited in such claims. is intended to include structure, material or action to perform its function in combination with other elements within its scope. The detailed description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. It will be apparent to those skilled in the art that there are many variations and modifications that do not depart from the scope and spirit of the invention. In order to best explain the principles of the invention, this specification is further intended to enable those skilled in the art to understand the invention to correspond to various embodiments with various modifications suited to the particular uses contemplated. Embodiments of have been selected and described.

Having thus described the invention herein in detail and with reference to its embodiments, modifications may be made without departing from the scope of the invention as defined in the following claims. It is clear that variations and modifications are possible.

Claims (12)

A method for bit transition enhanced DPE (Direct Position Estimation) of GNSS (Global Navigation Satellite System) signals, comprising:
receiving, at a receiver, GNSS signals from a plurality of different satellites in a satellite constellation configured for use with GNSS;
extracting both primary and secondary codes from the GNSS signal;
identifying a plurality of bit transitions in each of the primary code and the secondary code;
determining the alignment of one of the bit transitions of each of the primary code and the secondary code;
using the determined alignment of the one of the bit transitions to correct the determined coarse position corresponding to the primary code. The step of determining the alignment comprises:
generating a set of extended cross ambiguity functions for each of the GNSS signals in correlation with the receiver's local code;
and processing each of said extended cross ambiguity functions by a DPE utilizing said one of said bit transitions determined to be in said alignment. the method of. Each of said extended cross ambiguity functions is processed by a DPE which determines said bit transitions to determine position, velocity and time and to allow extension of integration time. 3. The method of claim 2, wherein 3. The method of claim 2, wherein the set of extended cross ambiguity functions correspond to the number of satellites within coverage of the GNSS receiver. 1. A data processing system configured for bit transition enhanced DPE (Direct Position Estimation) of GNSS (Global Navigation Satellite System) signals, the data processing system comprising:
a host computing platform having one or more computers each comprising memory and at least one processor; and a DPE module executing on said host computing platform, said DPE module comprising: comprising computer program instructions that are made executable during execution, the computer program instructions
receiving, at a GNSS receiver, signals for position determination from a plurality of different satellites in a satellite constellation configured for use with GNSS;
extracting both a primary code and a secondary code from the signal;
identifying a plurality of bit transitions in each of the primary code and the secondary code;
determining the alignment of one of the bit transitions of each of the primary code and the secondary code;
and using the determined alignment of the one of the bit transitions to correct coarse positions determined corresponding to the primary code. The step of determining the alignment comprises:
generating a set of extended cross ambiguity functions for each of the signals by correlating with the local code of the GNSS receiver;
and processing each of said extended cross ambiguity functions by a DPE utilizing said one of said bit transitions determined to be in said alignment. system. Each of said extended cross ambiguity functions is processed by a DPE, said DPE calculating not only to determine position, velocity and time, but also to determine said one of said bit transitions. 7. The system of claim 6, wherein 7. The system of claim 6, wherein the set of extended cross ambiguity functions correspond to the number of satellites within coverage of the GNSS receiver. 1. A computer readable storage medium for bit transition enhancement DPE (Direct Position Estimation) of GNSS (Global Navigation Satellite System) signals, the computer readable storage medium comprising program instructions. , the program instructions are executable by a device to cause the device to perform a method, the method comprising:
receiving, at a GNSS receiver, signals for position determination from a plurality of different satellites in a satellite constellation configured for use with GNSS;
extracting both a primary code and a secondary code from the signal;
identifying a plurality of bit transitions in each of the primary code and the secondary code;
determining the alignment of one of the bit transitions of each of the primary code and the secondary code;
using the determined alignment of the one of the bit transitions to correct the determined coarse position corresponding to the primary code. The step of determining the alignment includes:
generating a set of extended cross ambiguity functions for each of the signals in correlation with the local code of the GNSS receiver;
and processing each of said extended cross ambiguity functions by a DPE utilizing said one of said bit transitions determined to be in said alignment. computer readable storage medium. Each of said extended cross ambiguity functions is processed by a DPE, said DPE calculating to determine position, velocity and time and to determine said one of said bit transitions. 11. The computer-readable storage medium of claim 10. 11. The computer-readable storage medium of claim 10, wherein the set of extended cross ambiguity functions correspond to the number of satellites within coverage of the GNSS receiver.

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