Global navigation satellite system receiver

Abstract

The invention relates to a Global Navigation Satellite System (GNSS) receiver (16) comprising: 1) a Radio Frequency (RF) front-end (1); and 2) a receiver unit (2). The GNSS receiver (16) is configured to determine a composite pseudorange between the GNSS receiver (16) and a composite subset of GNSS satellites transmitting at a composite reception time using at least determined pseudoranges corresponding to at least two snapshot time windows (14). The invention also relates to an assembly (6, 16, 17, 18) comprising a GNSS receiver (16), a gateway (17) and a computing unit (18). The invention also relates to a method for determining a position of a GNSS receiver (16).

Description

Technical Field

[0001] This invention relates to a Global Navigation Satellite System (GNSS) receiver, components, and a method for determining the location of a GNSS receiver. Background Technology

[0002] GNSS is an important part of modern technological infrastructure. Typically manifested as GPS, Galileo, BeiDou, or GLONASS, GNSS is used for location determination and timing applications, such as in mobile phone network base stations.

[0003] GNSS receivers can be used in low-power wide-area networks (LPWANs), such as LoRaWAN networks. In such networks, the GNSS receiver primarily transmits uplink data to the gateway and has limited downlink capacity. Many Internet of Things (IoT) applications can generally benefit from GNSS capabilities, such as IoT location applications. For a GNSS receiver to determine its location, it needs access to ephemeris information related to GNSS satellites: the receiver either needs to receive this ephemeris information from the LPWAN or demodulate it directly from the acquired GNSS signal. Obtaining ephemeris information from the network is generally impractical due to limited downlink capacity, and demodulating ephemeris information directly from the acquired GNSS signal consumes significant power. Furthermore, due to accuracy loss over time, the ephemeris information needs to be refreshed sufficiently frequently (e.g., every three hours).

[0004] In many IoT applications with GNSS capabilities, it is essential that the GNSS receiver can operate for several years without changing the battery powering it. Therefore, in existing technology solutions, the GNSS receiver in an LPWAN does not calculate its location; instead, it simply sends pseudorange and optionally Doppler information to the cloud, which then stores the GNSS receiver's location. To do this, the cloud can host a GNSS solver and have access to ephemeris information. In this existing technology solution, the GNSS receiver consumes energy only during GNSS signal acquisition and data transmission to the cloud. Snapshot processing is another GNSS technique known from existing technology that helps optimize battery life. In snapshot processing, the GNSS receiver scans the GNSS signal for only a few to hundreds of milliseconds to extract pseudorange and Doppler information. The scan time of a GNSS receiver operating as a snapshot receiver is primarily determined by the GNSS receiver's available memory and power budget. On the other hand, classic GNSS receivers require continuous acquisition of GNSS signals for several to tens of seconds.

[0005] Snapshot processing is known to be power efficient; however, due to the short GNSS signal acquisition time in snapshot processing, it may offer lower accuracy and sensitivity compared to classical GNSS receiving techniques. Furthermore, snapshot processing, as known from existing technologies, struggles to handle outliers from a single scan, and LPWAN networks cannot provide sufficient information to the GNSS receiver via the downlink to compensate for the aforementioned disadvantages.

[0006] The object of the present invention is to mitigate at least some of the disadvantages associated with GNSS receivers known in the prior art; in particular, the object of the present invention is to mitigate at least some of the disadvantages associated with GNSS receivers used in LPWANs. Summary of the Invention

[0007] According to a first aspect of the invention, a GNSS receiver is provided, relating to the features described in claim 1. Further optional features and embodiments of the GNSS receiver of the invention are described in the dependent claims.

[0008] This invention relates to a Global Navigation Satellite System (GNSS) receiver, comprising: 1) a radio frequency (RF) front end configured to acquire GNSS signals transmitted by a plurality of GNSS satellites in at least two snapshot time windows, wherein each transmitted GNSS signal includes a corresponding known spreading code identifying the transmitting GNSS satellite, and wherein the RF front end is configured to convert the acquired GNSS signal in each of the at least two snapshot time windows into a digital sequence; and 2) a receiver unit configured to determine, for each snapshot time window, a pseudorange from the GNSS receiver to at least a subset of the transmitting GNSS satellites, wherein the at least two subsets corresponding to the at least two snapshot time windows may be different from each other, and wherein the pseudorange is determined using (i) the known spreading code and (ii) at least two digital sequences. The GNSS receiver is configured to: use at least the determined pseudorange corresponding to the at least two snapshot time windows to determine a composite pseudorange between the GNSS receiver and the composite subset of the transmitting GNSS satellites at a composite reception time.

[0009] Important GNSS systems are GPS, Galileo, BeiDou, or GLONASS. The GNSS receiver of this invention can be deployed in a low-power wide-area network (LPWAN). The GNSS receiver of this invention can implement multi-constellation pseudorange determination, i.e., it can simultaneously (or intermittently) determine pseudoranges from different constellations (e.g., GPS and BeiDou) to GNSS satellites. The GNSS receiver of this invention scans incoming GNSS signals within a snapshot time window. The GNSS receiver of this invention differs from GNSS receivers known in the prior art in that composite pseudorange is determined as a replacement for pseudorange. The GNSS receiver of this invention can typically include an oscillator, such as a quartz-based oscillator, which can be used by the receiver unit to determine the pseudorange.

[0010] A GNSS receiver can transmit a composite pseudorange determined at a composite reception time to a gateway, and the location of the GNSS receiver can be determined in a computing unit connected to the gateway, which may include a GNSS solver. In this case, the GNSS receiver may send only the composite pseudorange, instead of the original pseudorange, to the gateway. The GNSS receiver can also determine its own location locally (e.g., using its own computing resources). In this case, the composite pseudorange may not need to be sent to the gateway. If only the composite pseudorange is sent to the gateway, the GNSS solver can calculate the GNSS receiver's location with respect to an unknown time. In any case, the composite reception time may or may not be explicitly known to the GNSS receiver. Since not all transmitted GNSS signals can reach the GNSS receiver with sufficiently high quality, the GNSS receiver can determine pseudoranges to only a subset of the GNSS satellites.

[0011] Determining composite pseudorange can lead to improved accuracy. Compared to pseudorange obtained based on GNSS signals acquired within a snapshot time window, the accuracy is significantly improved. N Individual pseudorange measurements (e.g., N Composite pseudoranges constructed (corresponding to the number of snapshot time windows) typically have a smaller standard deviation. In ideal scenarios where only thermal noise exists as an error source (i.e., where multipath, ionospheric, tropospheric, satellite clock errors, etc., are absent or have been compensated for), the standard deviation of the composite pseudorange measurement error will only be 1 / sqrt( ) of the standard deviation of the pseudorange measurement error determined based on individual snapshot time windows. N ).

[0012] Furthermore, transmitting composite pseudorange instead of pseudorange to the gateway can improve power consumption in the GNSS receiver. The transmission power is often similar to or even higher than the power required to acquire GNSS signals in an LPWAN. Since the GNSS receiver of this invention may transmit only composite pseudorange and may not transmit pseudorange corresponding to a single snapshot time window, the total amount of data transmitted to the gateway can be minimized, resulting in reduced transmit power required by the GNSS receiver and consequently improved battery life, for example, for the batteries powering GNSS receivers deployed in LPWANs.

[0013] GNSS satellites move through space at finite speeds. At different points in time... t 1 and t k First n The true distance between a GNSS satellite and a GNSS receiver can be approximated (ignoring higher-order terms) as follows: .

[0014] It is time t k The first n The relative velocities of the GNSS satellites with respect to the GNSS receiver, and That corresponds to acceleration. Relative velocity can be determined using Doppler measurements: .

[0015] c It's the speed of light. F C It is the carrier frequency of the GNSS signal; for example, for the L1 channel of GPS, it is 1575.42 MHz, and Corresponding to the snapshot reception time t k First n The Doppler frequency between a GNSS satellite and a GNSS receiver.

[0016] In an embodiment of the GNSS receiver according to the present invention, the GNSS receiver includes a communication transceiver for transmitting data to and receiving data from a gateway via a wireless channel, and the GNSS receiver is configured to transmit the composite pseudorange to the gateway via the communication transceiver.

[0017] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver includes a receiver local clock and a corresponding snapshot reception time measured using the receiver local clock in each of the at least two snapshot time windows, wherein the receiver unit is configured to determine the pseudorange at the at least two snapshot reception times, and wherein the GNSS receiver is configured to determine the composite reception time based on the at least two snapshot reception times. The receiver local clock may be embodied as, for example, a phase-locked loop clock, and the receiver local clock may be based on a quartz-based oscillator typically included in the GNSS receiver.

[0018] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to additionally transmit the composite reception time to the gateway via the transceiver. The composite pseudorange and the composite reception time can be transmitted together to the gateway in a single uplink. Therefore, transmitting both the composite pseudorange and the composite reception time may not require two separate uplinks.

[0019] Therefore, in addition to composite pseudorange, the GNSS receiver can also transmit composite reception time to the gateway. The composite reception time can be determined by the GNSS receiver based on at least two snapshot reception times, for example, by averaging the at least two snapshot reception times if they are sufficiently close in time. In this case, a remote GNSS solver can calculate the GNSS receiver's location with respect to a known time, which may correspond to the composite reception time.

[0020] In a further embodiment of the GNSS receiver according to the invention, the at least two subsets include a common subset element, which is a common GNSS satellite among the plurality of GNSS satellites whose transmitted GNSS signals are observable by the GNSS receiver in the at least two snapshot time windows. The composite subset of transmitting GNSS satellites includes the common subset element, and the GNSS receiver is configured to determine the composite pseudorange by averaging corresponding pseudoranges, wherein a correspondence is established across the at least two snapshot time windows in the pseudoranges between (i) the GNSS receiver and (ii) the common GNSS satellite. The composite reception time may include a composite reception time, also referred to as an average composite reception time, which is represented as the average value between the at least two snapshot reception times if the at least two snapshot reception times are sufficiently close in time.

[0021] If the arriving GNSS signal has sufficient power, it can be considered observable by the GNSS receiver, allowing it to be reliably detected. This may require, for example, that the arriving GNSS signal have a sufficiently high signal-to-noise ratio. If, for example, the GNSS receiver receives the signal in three snapshot times... t 1 , t 2 and t 3 If GNSS signals are acquired from six GNSS satellites, the determined pseudorange can be described using the following linear model: .

[0022] It is in the k The snapshot received time is up to the first n The pseudorange determined by each GNSS satellite, It is in the k The snapshot received time is up to the first n The true distance of each GNSS satellite It is in the k The common offset of six GNSS satellites at the snapshot reception time, and It is thermal noise that is often modeled as Gaussian random noise. The common offset is specifically modeled for the clock bias of the receiver's local clock, which is part of the GNSS receiver.

[0023] In this example, the composite pseudorange can be determined by averaging as follows: And a similar averaging operation can be used to calculate the composite reception time as follows: If the three snapshot reception times are not too far apart (i.e., all three measurements are completed within a short time interval), then this linear averaging can be used: in this case, the GNSS satellite trajectory can be assumed to be approximately linear. Therefore, in a composite reception time... T Six composite pseudoranges were determined at the location. R 1 to R 6. The GNSS receiver of this invention can transmit these six composite pseudoranges to the gateway instead of the original 18 pseudoranges. The GNSS receiver of this invention can also transmit composite reception time... TInstead of the original three snapshot reception times, the data is sent to the gateway. After averaging, all six composite pseudoranges can have the same common offset. The GNSS solver can determine the GNSS receiver's location based on the six composite pseudoranges with respect to an unknown time, or it can determine the GNSS receiver's location based on the six composite pseudoranges with respect to a known time, which is the composite reception time, for example, obtained by averaging.

[0024] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to subtract a determined pseudorange corresponding to a reference GNSS satellite from a determined pseudorange corresponding to the remaining GNSS satellites among the plurality of GNSS satellites, and wherein the GNSS receiver is configured to select the reference GNSS satellite based on the received signal strength in the at least two snapshot time windows, wherein the subtraction is performed between pseudoranges corresponding to the same snapshot reception window and provides a differential pseudorange relative to the reference GNSS satellite, and wherein the GNSS receiver is configured to determine the composite pseudorange by averaging corresponding differential pseudoranges, the composite pseudorange being a differential composite pseudorange, wherein a correspondence between differential pseudoranges is established across the at least two snapshot time windows, and wherein the GNSS receiver is configured to determine the composite reception time for each differential composite pseudorange, the composite reception time being a differential composite reception time. The GNSS receiver can determine the differential composite reception time by averaging over snapshot reception times corresponding to the differential pseudoranges, where snapshot reception times are used as part of the differential composite pseudorange determination. Averaging may be sufficient if the snapshot reception times used to determine the differential composite reception time are sufficiently close in time. The GNSS solver can determine the location of the GNSS receiver based on the differential composite pseudorange with respect to an unknown time, or, if the GNSS solver has access to the differential composite reception time, it can determine the location of the GNSS receiver based on the differential composite pseudorange at that differential composite reception time.

[0025] If, for example, a GNSS receiver receives data in three snapshot times t 1 , t 2 and t 3 If GNSS signals are acquired from six GNSS satellites, and some GNSS signals are weak and therefore cannot be accurately acquired, the determined pseudorange can be described using the following linear model: .

[0026] Each '0' in the aforementioned equation indicates the corresponding pseudorange (e.g., in time). t 1 The pseudorange to the fifth GNSS satellite is not determined. Without loss of generality, it is assumed that the first GNSS satellite provides the strongest signal with the highest received signal strength. Subtracting the pseudorange to the first GNSS satellite from the remaining pseudorange yields: .

[0027] It is in the k The snapshot received at the time of the first snapshot n Differential pseudorange from the first GNSS satellite to the first GNSS satellite, It is in the k The snapshot received at the time of the first snapshot n The differential true distance from each GNSS satellite to the first GNSS satellite, and This is the difference of the noise terms. Subtraction has removed the common offset.

[0028] The averaging provides the difference composite pseudorange, that is, , , , and . , , This example corresponds to composite (differential) reception time. T= ( t 1 +t 2 +t 3 ) / 3, Corresponding to composite (differential) reception time T 5 = ( t 2 +t 3 ) / 2, and Corresponding to composite (differential) reception time T 6 = ( t 1 +t 3 ) / 2. If the three snapshot reception times are not too far apart, this linear averaging can be used: in this case, the GNSS satellite trajectory can be assumed to be approximately linear. In this example, the GNSS receiver can transmit five determined differential composite pseudoranges to the gateway, and optionally three composite (differential) reception times to the gateway.

[0029] In a further embodiment of the GNSS receiver according to the invention, the receiver unit is configured to: determine the Doppler frequency between the GNSS receiver and a subset of transmitting GNSS satellites corresponding to the at least two snapshot time windows.

[0030] Doppler shift occurs during the transmission of GNSS signals by a GNSS satellite due to the relative movement between the transmitter (in this case, the GNSS satellite) and the receiver (in this case, the GNSS receiver). In GPS, for example, the Doppler frequency is typically in the range of ±4.2 kHz. This Doppler shift can also be determined by the GNSS receiver when determining the pseudorange. The Doppler frequency can be determined by the GNSS receiver to improve the accuracy of the determined pseudorange: the determined Doppler frequency can be used to shift the frequency of the receiver's local clock to align the replicated GNSS signal created by the GNSS receiver with the GNSS signal arriving at the GNSS receiver from the GNSS satellite.

[0031] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to determine the Doppler frequency between the GNSS receiver and a subset of transmitting GNSS satellites corresponding to the at least two snapshot time windows, based on almanac information received from at least one of the plurality of GNSS satellites.

[0032] The Doppler frequency can be determined solely based on ephemeris information, or it can be determined using signal processing methods based on both the ephemeris information estimated during pseudorange determination and the Doppler frequency. Alternatively, only this signal processing method can be used to determine the Doppler frequency.

[0033] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to determine a time-aligned differential composite pseudorange at a common composite reception time, wherein the GNSS receiver is configured to subtract a Doppler frequency corresponding to the reference GNSS satellite from a determined Doppler frequency corresponding to the remaining GNSS satellite, the subtraction providing a differential Doppler frequency, and wherein the GNSS receiver is configured to determine the time-aligned differential composite pseudorange based on: (i) the determined differential composite pseudorange; (ii) the differential Doppler frequency; (iii) the differential composite reception time; and (iv) the common composite reception time.

[0034] In the previous example regarding differential composite pseudorange, the differential composite pseudorange was determined at three different composite (differential) reception times. To determine the differential composite pseudorange at a common composite reception time, the determined Doppler frequency can be used. At the snapshot reception time... t 1 , t 2 and t 3 Given sufficient temporal proximity, the Doppler frequency corresponding to each GNSS satellite / GNSS receiver pair can be assumed to be constant over the three snapshot reception times; that is, there are six Doppler frequencies in this example. D 1 , D 2 , D 3 , D 4 , D 5 and D 6 As shown above, the first Doppler frequency can be subtracted from the remaining Doppler frequencies. D 1 This provides the differential Doppler frequencies between the reference GNSS satellite (in this example, the first GNSS satellite) and the remaining GNSS satellites: ΔD 2 , ΔD 3 , ΔD 4 , ΔD 5 and ΔD 6 Then the differential composite pseudorange for GNSS satellites 5 and 6 can be projected onto the composite reception time. T (In this example, it refers to the composite reception time of GNSS signals transmitted by GNSS satellites two through four): as well as .

[0035] In this example, it is assumed that the snapshot reception times are close enough to each other that the GNSS satellite trajectories can be modeled as linear. However, in cases where the GNSS satellite trajectories between snapshot reception times can no longer be modeled linearly, time-aligned differential composite pseudorange can still be determined: in this case, the projection mechanism described in this example can be modified to include differential acceleration. Using the projection mechanism described in this example, the differential composite pseudorange can be projected onto a freely chosen common composite reception time. Having a common composite reception time reduces the amount of data the GNSS receiver can send to the gateway, thereby improving, for example, the battery life of the battery powering the GNSS receiver: instead of the three composite reception times in the first part of this example where the Doppler frequency is not used, the common composite reception time may only need to be sent by the GNSS receiver to the gateway once. However, the GNSS receiver may also only send the differential composite pseudorange to the gateway.

[0036] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to determine the composite pseudorange based on a linear equation system that maps a composite vector, including an unknown composite pseudorange and an unknown offset, to a target vector, wherein the target vector includes entries for each determined pseudorange, each pseudorange being determined at its corresponding snapshot reception time, wherein each entry of the target vector is based on: (i) the corresponding determined pseudorange; (ii) the corresponding velocity between the GNSS receiver and the GNSS satellite at the corresponding snapshot reception time, corresponding to the corresponding determined pseudorange; (iii) the corresponding snapshot reception time; and (iv) a common composite reception time, wherein the composite reception time is embodied in the common composite reception time, and wherein the corresponding velocity between the GNSS receiver and the GNSS satellite is determined based on a determined corresponding Doppler frequency.

[0037] In a further embodiment of the GNSS receiver according to the invention, each entry of the target vector is additionally based on a corresponding acceleration between the GNSS receiver and the GNSS satellite at the corresponding snapshot reception time, corresponding to the corresponding determined pseudorange, wherein the GNSS receiver is configured to determine the acceleration based on (i) a time numerical difference of the determined Doppler frequency and / or (ii) almanac information received by the GNSS receiver.

[0038] The following assumes that it is possible to K At the time of each snapshot reception, the GNSS receiver is determined to be connected to up to [number missing]. N Pseudorange between GNSS satellites. Therefore, it is possible to achieve pseudorange at composite reception time. t Location determined N A composite pseudorange. (and)K The snapshot reception time corresponds to K A common offset can generally be unknown. It needs to be determined. N Each composite pseudorange has a new common offset: therefore K Any of the common offsets can be considered known or set to any value, such as '0'. For example, consider the first... K Common offset c K If it is set to '0', you may need to confirm. N+K-1 One unknown: The vector X It can be called a composite vector.

[0039] Target vector Y It can be constructed as follows: each determined pseudorange With corresponding speed and (if applicable, i.e., if) (Not small enough to ignore acceleration) corresponding to acceleration Together The entries are provided to the target vector Y in the form of .

[0040] It is possible to construct (linearly) composite vectors X Mapping to target vector Y matrix H : Y = H*X If, for example, in all K The snapshot received time determined all N The pseudorange of a GNSS satellite, then the matrix H It can be constructed as follows: In this case, H It is the size of ( N*K ) x ( N+K- 1) matrix; H Each row contains (the corresponding composite pseudorange and common offset) N+ K- 1) One zero and one or two 1s. In this example, H The first row equals [1, 0, 0, …, 0, 1, 0, …, 0], where the first element of the first row equals 1 (corresponding to the composite pseudorange to the first GNSS satellite). R 1), and the first row of which is ( N+ 1) Elements equal to 1 (corresponding to the common offset) c 1). In this example, H The second row equals [1, 0, 0, …, 0, 1, 0, ..., 0], where the first element of the second row equals 1 (corresponding to the composite pseudorange to the first GNSS satellite).R 1), and the (N+2)th element of the second row is equal to 1 (corresponding to the common offset). c 2). In this example, H The K The row is equal to [1, 0, …, 0, 0, 0, …, 0], where the first row is [1, 0, …, 0, 0, …, 0]. K Only the first element of the row is equal to 1 (corresponding to the composite pseudorange to the first GNSS satellite). R 1); No. K The common offset can be set to 0.

[0041] Through matrix manipulation, especially matrix inversion, it is possible to determine the target vector. Y Determine the composite vector X The entry. Y and H It can be constructed in the following way: considering all determined pseudoranges. In the construction... Y and H The pseudorange, which cannot be reliably determined (e.g., due to weak GNSS signals arriving at the GNSS receiver), can be ignored. This is used to construct the target vector. Y Composite reception time t It can be set arbitrarily, for example, set to t 1 to t K Between. t 1 to t K Centering t This can help minimize errors.

[0042] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to transmit the determined Doppler frequency and / or the determined differential Doppler frequency to the gateway via the communication transceiver.

[0043] Doppler frequencies and / or differential Doppler frequencies can be used to calculate a first coarse estimate of the GNSS receiver's position using Doppler positioning algorithms known in the art. The Doppler frequencies and / or differential Doppler frequencies can be transmitted to the gateway along with the composite pseudorange and optionally with the composite reception time in a single uplink, or they can be transmitted to the gateway in separate uplinks. Alternatively, the Doppler frequencies and / or differential Doppler frequencies can also be transmitted to the gateway along with the composite reception time in a single uplink.

[0044] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver is configured to perform outlier detection on the determined pseudorange before determining the composite pseudorange, wherein majority voting is used to detect and / or outliers are detected based on a GNSS satellite trajectory model, wherein the GNSS receiver is configured to determine the GNSS satellite trajectory model using received almanac information.

[0045] In a further embodiment of the GNSS receiver according to the invention, the receiver unit is embodied as an open-loop receiver unit, and wherein the open-loop receiver unit is configured to use batch processing to determine the pseudorange.

[0046] In a further embodiment of the GNSS receiver according to the invention, the receiver unit is configured to determine the pseudorange and Doppler frequency corresponding to a first snapshot time window within the at least two snapshot time windows based on a search within the full search space, and the receiver unit is configured to determine the pseudorange and Doppler frequency corresponding to a subsequent snapshot time window within the at least two snapshot time windows based on a search within a restricted search space, the subsequent snapshot time window being after the first snapshot time window, the restricted search space being based on the pseudorange and Doppler frequency determined for the first snapshot time window.

[0047] In a further embodiment of the GNSS receiver according to the present invention, the receiver unit is configured to determine the pseudorange and Doppler frequency corresponding to the first snapshot time window for a first snapshot time window within the at least two snapshot time windows based on a search within a first search space, and the receiver unit is configured to determine the pseudorange and Doppler frequency corresponding to a subsequent snapshot time window within the at least two snapshot time windows based on a search within a subsequent search space, the subsequent snapshot time window being after the first snapshot time window, the subsequent search space being based on the pseudorange and Doppler frequency determined for the first snapshot time window.

[0048] The first search space can be based on previously available knowledge that the GNSS receiver may possess. For example, the GNSS receiver may have a coarse estimate of the relative velocity of the GNSS satellites with respect to themselves, and thus constrain the search within the possible Doppler shift.

[0049] In a further embodiment of the GNSS receiver according to the invention, the GNSS receiver includes at least one antenna for receiving GNSS signals transmitted by a GNSS satellite, and the GNSS receiver is configured to select from the at least one antenna an antenna for receiving GNSS signals with optimal reception quality. The GNSS receiver may also be configured to dynamically adapt (i) the number of snapshot time windows, (ii) the acquisition time (from several ms to several hundred ms) of each snapshot time window, (iii) the receiving antenna, (iv) the receiving bandwidth, (v) the receiving sampling quantization, and (iv) the interval between each snapshot time window, based on signal reception conditions, power budget, available memory size on the GNSS receiver, etc.

[0050] According to a further aspect of the invention, a component is provided comprising: 1) a GNSS receiver according to the invention; 2) a gateway, particularly embodied as a low-power wide-area network (LPWAN) gateway; and 3) a computing unit connected to the gateway, wherein the computing unit is configured to determine the position of the GNSS receiver based on (i) a composite pseudorange provided to the computing unit by the GNSS receiver via the gateway and (ii) navigation messages transmitted by a plurality of GNSS satellites, wherein the navigation messages include information relating to ephemeris tables of the plurality of GNSS satellites, wherein the computing unit is configured to determine the position of the GNSS receiver using a GNSS solver.

[0051] The computing unit can also be located in the cloud. Therefore, the computing unit can be directly connected to the gateway, or indirectly connected, particularly via a network. The computing unit can also receive composite reception time from a GNSS receiver and use the received composite reception time to determine the location of the GNSS receiver at a known time. If the computing unit only receives composite pseudorange, it can determine the location of the GNSS receiver with respect to an unknown time.

[0052] According to a further aspect of the invention, a method for determining the location of a GNSS receiver is provided, comprising the steps of: 1) acquiring GNSS signals transmitted by a plurality of GNSS satellites in at least two snapshot time windows; 2) determining pseudorange from the GNSS receiver to the plurality of GNSS satellites in each of the at least two snapshot time windows based on the acquired GNSS signals; 3) using the pseudorange determined in the at least two snapshot time windows to determine a composite pseudorange at a composite reception time associated with (i) the GNSS receiver and (ii) at least a subset of the plurality of GNSS satellites; and 4) determining the location of the GNSS receiver using (i) at least the composite pseudorange and (ii) information relating to ephemeris tables of the GNSS satellites in at least the subset of the plurality of GNSS satellites. Where the GNSS receiver includes a local receiver clock, the pseudorange can be determined at at least two snapshot reception times within the at least two snapshot time windows.

[0053] In an embodiment of the method according to the invention, the method includes the steps of: transmitting the composite pseudorange to a computing unit via a gateway. The location of the GNSS receiver may be determined on the computing unit. A composite reception time may also be determined and optionally sent to the computing unit. When the composite reception time is sent to the computing unit via the gateway, the computing unit may use the composite pseudorange at the composite reception time to determine the location of the GNSS receiver; alternatively, the location of the GNSS receiver may be determined with respect to an unknown time. Attached Figure Description

[0054] Exemplary embodiments of the present invention are disclosed in the description and illustrated in the accompanying drawings, in which: Figure 1 A schematic depiction of a portion of a GNSS system according to the prior art is shown; Figure 2 A schematic depiction of prior art GNSS receiver processing steps for determining the location of a GNSS receiver is shown; Figure 3 A schematic depiction of the snapshot time window and the snapshot reception time within the snapshot time window is shown; Figure 4 A schematic depiction of the different times involved in the determination of pseudorange according to the prior art is shown; Figure 5 A schematic depiction of an embodiment of a GNSS receiver according to the present invention is shown; and Figure 6 A schematic depiction of components according to the invention, including a GNSS receiver, a gateway, and a computing unit, is shown. Detailed Implementation

[0055] Figure 1 A schematic depiction of a portion of a GNSS system according to the prior art is shown. Figure 1 A GNSS receiver 16 is shown on the Earth's surface. A GNSS satellite 11 orbits the Earth and transmits GNSS signals toward the Earth's surface. The GNSS receiver 16 detects and acquires these GNSS signals and uses them to determine its 3D location.

[0056] The basic principles of GNSS are explained below with reference to the Global Positioning System (GPS). Similar principles apply to other GNSS systems, such as Galileo, GLONASS, or BeiDou. GPS consists of four segments: 1) Space segment; 2) Control segment; 3) Ground segment; and 4) User segment. The space segment includes the constellation of GPS satellites; the control segment monitors the operation of the space segment and provides it with updates; the ground segment is typically used to improve GPS availability; and the user segment includes hardware and software for determining the position and / or velocity of GPS receivers, or hardware and software for timing applications.

[0057] The GPS space segment comprised 31 operational satellites in the summer of 2021. These satellites are positioned in orbit around the Earth in such a manner that at any given time and from any location on Earth, at least four GPS satellites are in view. Each satellite broadcasts precise information about its orbit in the form of an ephemeris. Less precise information about the orbits of all GPS satellites is provided in the form of an almanac. Both the ephemeris and the almanac are transmitted by each GPS satellite as part of the navigation message.

[0058] GPS uses code division multiple access (CDMA) to transmit information on designated frequency bands. Typical frequency bands used by GPS are the L1 and L2 channels, with the L1 channel centered at 1575.42 MHz and the L2 channel centered at 1227.60 MHz. Each GPS satellite is equipped with a precise atomic clock with a base frequency of 10.23 MHz. Therefore, the center frequency of the L1 channel is equal to the base frequency multiplied by '154', and the center frequency of the L2 channel is equal to the base frequency multiplied by '120'. GPS uses Gold codes to enable CDMA; Gold codes are an example of spreading codes. Gold codes are pseudo-random noise sequences with a period of 1023. Since the base frequency of each atomic clock on a GPS satellite is 10.23 MHz, each Gold code takes 1 ms to transmit. Goldberg codes are designed in such a way that they achieve an autocorrelation value close to 1 for small shifts between two identical Goldberg code sequences (for larger shifts, the autocorrelation value is close to 0), and the cross-correlation value between different Goldberg code sequences is always close to 0, regardless of the shift.

[0059] Each GPS satellite transmits its navigation message at 50 bits per second (bps). Because each GPS satellite is assigned a unique Gold code, it modulates its navigation message using that code and further modulates it using a carrier frequency (e.g., the center frequency of the L1 channel). The navigation message is a 1500-bit sequence that takes 30 seconds to transmit. This results in the GPS signal being transmitted towards Earth.

[0060] On Earth, GPS signals transmitted by GPS satellite 11 are acquired by an antenna connected to GPS receiver 16. This antenna may also be part of GPS receiver 16. GPS signal acquisition by GPS receiver 16 is performed using autocorrelation techniques: GPS receiver 16 generates a GPS copy signal and compares it with the actually measured GNSS signal (the acquired GPS signal is first processed by the radio frequency (RF) front-end of the GPS receiver before this comparison is performed); due to the aforementioned properties of Gold code, this comparison can be performed with high precision and provides an estimate of the elapsed time between the transmission of the GPS signal by the GPS satellite and the reception by the GPS receiver. The "elapsed time" is detected in the form of a shift that maximizes the aforementioned autocorrelation. Multiplying the estimated "elapsed time" by the speed of light provides the pseudorange between the GPS receiver and the GPS satellite. At any given time, GPS signals from multiple GPS satellites 11 arrive at GPS receiver 11. Due to the aforementioned properties of the Gold sequence, the GPS receiver can independently process GPS signals transmitted by different GPS satellites after the RF front end (therefore, the pseudorange of all GPS satellites 11 whose GPS signals are acquired by the GPS receiver 16 can be determined independently).

[0061] Due to biases in the GPS satellite clocks that drive the transmission of GPS signals from GPS satellites, biases in the GPS receiver clocks, propagation errors (ionospheric and tropospheric), and additional error sources (multipath, thermal noise in the GPS receiver, etc.), pseudorange does not correspond to true range. In principle, if pseudorange were equal to true range, three GPS satellites would be needed to determine the three degrees of freedom of the GPS receiver (triangulation). However, since there is an offset between pseudorange and true range, this offset also needs to be determined. Therefore, four GPS satellites must be visible to the GPS receiver so that the GPS receiver can use GPS signals received from at least four GPS satellites to determine its own position and offsets from both.

[0062] Figure 2A schematic depiction of prior art GNSS receiver processing steps for determining the location of a GNSS receiver is shown. The prior art GNSS receiver shown uses snapshot processing (open-loop receiver architecture). An incoming GNSS signal transmitted by a GNSS satellite is recorded by antenna 6. The recorded GNSS signal 5 is passed to RF front-end 1. GNSS signals are typically not transmitted by the GNSS satellite at baseband. Furthermore, GNSS satellites use digital modulation. GPS satellites, for example, can use binary phase shift keying (BPSK) as a digital modulation scheme. Therefore, RF front-end 1 can convert the incoming GNSS signal into a digital sequence, either directly to baseband or to intermediate frequency. RF front-end 1 typically includes a bandpass filter, an analog-to-digital converter, and a quantizer. The digital sequence provided by RF front-end 1 can then be processed by open-loop receiver architecture 2.

[0063] Due to the movement between the GNSS satellite and the GNSS receiver (this relative movement is typically largely caused by the high velocity of the GNSS satellite in space), a Doppler shift occurs in the GNSS signal. RF front-end 1 can be configured to acquire the GNSS signal within a snapshot time window. Open-loop receiver architecture 2 can determine the pseudorange by implementing numerous correlations in parallel. The GNSS replica signal, which varies in relation to the correlations, can be used in a three-dimensional space including possible GNSS satellites, possible Doppler shifts, and possible code delays of the spreading code. If the GNSS satellites are known (e.g., by utilizing almanac information), the three-dimensional search space can be reduced to a two-dimensional search space based on the possible Doppler shifts and possible code delays.

[0064] Therefore, the open-loop receiver architecture 2 provides pseudorange between the GNSS receiver and the GNSS satellites whose signals are acquired in the corresponding snapshot time window for each snapshot time window. Each set of pseudoranges is subsequently provided to a navigation module 3, which may include a known GNSS solver. The navigation module 3 can provide the GNSS receiver's 3D position and / or velocity as output 4 for each set of provided pseudoranges.

[0065] Figure 3 A schematic depiction of snapshot time window 14 and snapshot reception time 12 within snapshot time window 14 is shown. Snapshot time window 14 can be equally spaced in time (not shown), or snapshot time window 14 can be irregularly spaced in time, such as... Figure 3As shown in the diagram. Each snapshot time window can have a different time range, or all snapshot time windows can have the same time range, for example, 50 ms. Within a snapshot time window, the GNSS receiver is configured to acquire GNSS signals transmitted by a GNSS satellite. For each snapshot time window 14, the pseudorange can be determined with respect to the snapshot reception time 12 within the snapshot time window 14. The snapshot reception time 12 can be placed in different ways in time within different snapshot time windows, or the snapshot reception time 12 can be placed at the same relative position in time within the corresponding snapshot time windows. The snapshot reception time 12 can typically be set by the GNSS receiver. In conventional GNSS receivers, for example, the snapshot reception time 12 can be equidistant in time, for example, every 60 seconds. The snapshot reception time 12 can be measured using a receiver local clock that can be part of the GNSS receiver. Since the receiver local clock is typically biased, the snapshot reception time 12 measured using the receiver local clock typically does not correspond to the true reception time. This timing error will be discussed later regarding... Figure 4 The embodiments are discussed in more detail.

[0066] The pseudorange can be determined at the snapshot reception time 12 in multiple snapshot time windows 14. This pseudorange can be compressed into a composite pseudorange at a composite reception time, which can be derived based on the snapshot reception time 12.

[0067] Figure 4 A schematic depiction of the different times involved in the determination of pseudorange according to the prior art is shown. Figure 4 In this paper, only errors due to clock offset are considered, while propagation errors and other error sources such as multipath errors or relativistic errors are ignored for simplicity. The transmission of GNSS signals by a GNSS satellite is driven by a satellite clock 8 with a specific offset. The offset of the satellite clock 8 is typically sent to the GNSS receiver as part of the navigation message. The GNSS signal is transmitted to the antenna 6 of the GNSS receiver via radio waves 9. The RF front end converts the GNSS signal into a digital sequence 15. For simplicity, Figure 4 The scenario depicted corresponds to a single snapshot time window and a single GNSS signal transmitted by a GNSS satellite arriving at antenna 6.

[0068] A GNSS receiver may include a receiver local clock 7, with an offset typically much larger than that of the satellite clock 8. The receiver local clock 7 can be used to generate a GNSS replica signal. An oscillator (e.g., a quartz-based oscillator) may also be used to generate the GNSS replica signal, wherein the oscillator may be part of the GNSS receiver. Figure 4In the snapshot reception time 12, measured by the receiver's local clock 7, at time... T Place. T S This corresponds to the reading of satellite clock 8 when the GNSS signal is transmitted. The difference can be determined using autocorrelation techniques. T – T S Due to snapshot reception time T This can be considered as corresponding to the actual reception time. t Add receiver local clock 7 offset ,and T S This can be considered as the actual satellite launch time. t S and satellite clock 8 offset The addition, therefore the pseudorange is given as ,in This is the true distance from the GNSS receiver (at the actual reception time) to the satellite (at the actual satellite launch time). Actual satellite launch time t S It can be determined using, for example, an iterative algorithm known as the "optical-time equation". Therefore, the receiver local clock 7 offset can be primarily determined by solving the GNSS navigation equation.

[0069] Figure 5 A schematic depiction of an embodiment of a GNSS receiver 16 according to the present invention is shown. The GNSS receiver 16 receives GNSS signals from an antenna 6. The antenna 6 may also be part of the GNSS receiver 16. The GNSS receiver includes an RF front-end 1, a microprocessor 13, and a communication transceiver 10 with access to the antenna 6. The microprocessor may be used to implement snapshot processing 2 in software. The microprocessor 13 may also determine a composite pseudorange and a composite reception time based on the pseudorange determined at the snapshot reception time obtained using snapshot processing 2. The microprocessor 13 may also be shared with other functions. If the GNSS receiver 16 is, for example, part of a mobile phone, the microprocessor 13 may be a regular microprocessor already included in the mobile phone.

[0070] Figure 6A schematic depiction of components 6, 16, 17, 18 according to the invention, including a GNSS receiver 16, a gateway 17, and a computing unit 18, is shown. The antenna 6 for receiving GNSS signals may be part of the GNSS receiver 16, or the antenna 6 may be separate. The GNSS receiver may transmit composite pseudorange and optionally composite reception time to the computing unit 18 via the gateway 17. The GNSS receiver may be used in a low-power wide-area network (LPWAN). The GNSS solver on the computing unit 18 can then determine the position and / or velocity of the GNSS receiver at an unknown time (in the case where the composite reception time has not been transmitted) or at a known time (in the case where the composite reception time has been transmitted), based on the composite pseudorange, wherein the GNSS solver uses additional information, for example, obtained from GNSS navigation messages.

Claims

1. A Global Navigation Satellite System (GNSS) receiver (16), comprising: • A radio frequency (RF) front end (1) is configured to acquire GNSS signals transmitted by a plurality of GNSS satellites (11) in at least two snapshot time windows (14), wherein each transmitted GNSS signal includes a corresponding known spreading code identifying the transmitting GNSS satellite (11), and wherein the RF front end (1) is configured to convert the acquired GNSS signal in each of the at least two snapshot time windows (14) into a digital sequence (15). as well as • Receiver unit (2) is configured to determine pseudorange from the GNSS receiver (16) to the transmitting GNSS satellite (11) for each snapshot time window (14), wherein the at least two subsets corresponding to the at least two snapshot time windows (14) may be different from each other, and wherein the pseudorange is determined using (i) the known spreading code and (ii) at least two digital sequences (15); • A receiver local clock (7) for measuring the corresponding snapshot reception time (12) in each of the at least two snapshot time windows (14), wherein the receiver unit (2) is configured to determine the pseudorange at the at least two snapshot reception times (12); and • A communication transceiver (10) for sending data to and receiving data from the gateway (17) via a wireless channel. Its features The GNSS receiver (16) is configured to determine a composite pseudorange between the GNSS receiver (16) and a composite subset of transmitting GNSS satellites at a composite reception time by averaging the determined pseudorange corresponding to the at least two snapshot time windows (14) in time sufficiently close such that the GNSS satellite trajectory is assumed to be approximately linear, wherein the composite reception time is determined by averaging the at least two snapshot reception times (12), and wherein the GNSS receiver (16) is configured to transmit the composite pseudorange and the composite reception time to the gateway (17) via the communication transceiver (10), wherein the composite pseudorange replaces the pseudorange corresponding to the individual snapshot time windows (14) in order to reduce the amount of data transmitted.

2. The GNSS receiver (16) according to claim 1, wherein the at least two subsets include a common subset element, the common subset element being a common GNSS satellite (11) among the plurality of GNSS satellites (11), the corresponding GNSS signals emitted by which can be observed by the GNSS receiver (16) in the at least two snapshot time windows (14), wherein the composite subset of emitting GNSS satellites (11) includes the common subset element, and wherein the GNSS receiver (16) is configured to determine the composite pseudorange by averaging the corresponding pseudoranges, wherein a correspondence is established across the at least two snapshot time windows (14) in the pseudoranges between (i) the GNSS receiver (16) and (ii) the common GNSS satellite (11).

3. The GNSS receiver (16) according to claim 1, wherein the GNSS receiver is configured to subtract a determined pseudorange corresponding to a reference GNSS satellite among the plurality of GNSS satellites (11) from a determined pseudorange corresponding to the remaining GNSS satellite among the plurality of GNSS satellites (11), wherein the GNSS receiver (16) is configured to select the reference GNSS satellite based on the received signal strength in the at least two snapshot time windows (14), wherein the subtraction is performed between pseudoranges corresponding to the same snapshot time window (14) and provides a differential pseudorange relative to the reference GNSS satellite, and wherein the GNSS receiver (16) is configured to determine the composite pseudorange by averaging the corresponding differential pseudoranges, the composite pseudorange being a differential composite pseudorange, wherein a correspondence between differential pseudoranges is established across the at least two snapshot time windows (14), and wherein the GNSS receiver (16) is configured to determine the composite reception time for each differential composite pseudorange, the composite reception time being a differential composite reception time.

4. The GNSS receiver (16) according to claim 1, wherein the receiver unit (2) is configured to: determine the Doppler frequency between the GNSS receiver (16) and a subset of the transmitting GNSS satellites (11) corresponding to the at least two snapshot time windows (14), and / or wherein the GNSS receiver (16) is configured to: determine the Doppler frequency between the GNSS receiver and a subset of the transmitting GNSS satellites (11) corresponding to the at least two snapshot time windows (14) based on almanac information received from at least one of the plurality of GNSS satellites (11).

5. The GNSS receiver (16) of claim 3, wherein the GNSS receiver (16) is configured to determine a time-aligned differential composite pseudorange at a common composite reception time, wherein the GNSS receiver (16) is configured to subtract a Doppler frequency corresponding to the reference GNSS satellite from a determined Doppler frequency corresponding to the remaining GNSS satellite, the subtraction providing a differential Doppler frequency, and wherein the GNSS receiver (16) is configured to determine the time-aligned differential composite pseudorange based on: (i) the determined differential composite pseudorange; (ii) the differential Doppler frequency; (iii) the differential composite reception time; and (iv) the common composite reception time.

6. The GNSS receiver (16) of claim 1, wherein the GNSS receiver (16) is configured to determine the composite pseudorange based on a linear equation system that maps a composite vector comprising an unknown composite pseudorange and an unknown offset to a target vector, wherein the target vector comprises an entry for each determined pseudorange, each pseudorange being determined at its corresponding snapshot reception time (12), wherein each entry of the target vector is based on: (i) the corresponding determined pseudorange; (ii) the corresponding velocity between the GNSS receiver (16) and the GNSS satellite at the corresponding snapshot reception time (12) corresponding to the corresponding determined pseudorange; (iii) the corresponding snapshot reception time (12); and (iv) a common composite reception time, wherein the composite reception time is embodied in the common composite reception time, and wherein the corresponding velocity between the GNSS receiver (16) and the GNSS satellite is determined based on a determined corresponding Doppler frequency.

7. The GNSS receiver (16) according to claim 6, wherein each entry of the target vector is additionally based on a corresponding acceleration between the GNSS receiver (16) and the GNSS satellite at the corresponding snapshot reception time (12) corresponding to the corresponding determined pseudorange, wherein the GNSS receiver (16) is configured to determine the acceleration based on (i) the time numerical difference of the determined Doppler frequency and / or (ii) the almanac information received by the GNSS receiver (16).

8. The GNSS receiver (16) according to any one of claims 4 to 7, wherein the GNSS receiver (16) is configured to transmit the determined Doppler frequency and / or the determined differential Doppler frequency to the gateway (17) via the communication transceiver (10).

9. The GNSS receiver (16) according to claim 1, wherein the GNSS receiver (16) is configured to: perform outlier detection on the determined pseudorange before determining the composite pseudorange, wherein majority voting is used to detect and / or outliers are detected based on a GNSS satellite trajectory model, wherein the GNSS receiver (16) is configured to determine the GNSS satellite trajectory model using received almanac information.

10. The GNSS receiver (16) of claim 1, wherein the receiver unit (2) is configured to determine the pseudorange and Doppler frequency corresponding to the first snapshot time window for a first snapshot time window among the at least two snapshot time windows (14) based on a search in the full search space or a search in the first search space, and wherein the receiver unit (2) is configured to determine the pseudorange and Doppler frequency corresponding to the subsequent snapshot time window among the at least two snapshot time windows (14) based on a search in a restricted search space, the subsequent snapshot time window being after the first snapshot time window, the restricted search space being based on the pseudorange and Doppler frequency determined for the first snapshot time window according to the search in the full search space or the search in the first search space.

11. Components, including: GNSS receiver (16) according to any one of claims 1 to 10; Gateway (17), specifically a low-power wide area network (LPWAN) gateway; And a computing unit (18) connected to the gateway (17), wherein the computing unit (18) is configured to determine the position of the GNSS receiver (16) based on (i) a composite pseudorange provided to the computing unit (18) by the GNSS receiver (16) via the gateway (17) and (ii) navigation messages transmitted by a plurality of GNSS satellites (11), wherein the navigation messages include information relating to ephemeris tables of the plurality of GNSS satellites (11), wherein the computing unit (18) is configured to determine the position of the GNSS receiver (16) using a GNSS solver.

12. A method for determining the location of a GNSS receiver (16), comprising the following steps: 1) Acquire GNSS signals transmitted by multiple GNSS satellites (11) in at least two snapshot time windows (14); 2) Based on the acquired GNSS signals, determine the pseudorange associated with (i) the GNSS receiver (16) and (ii) the plurality of GNSS satellites (11) in each of the at least two snapshot time windows (14); 3) By averaging the pseudoranges determined in the at least two snapshot time windows (14) when they are sufficiently close in time such that the GNSS satellite trajectories are assumed to be approximately linear, determine at the composite reception time a composite pseudorange from the GNSS receiver (16) to the plurality of GNSS satellites (11) of at least a subset, wherein the composite reception... The reception time is determined by averaging the snapshot reception times measured using the receiver's local clock (7) in each of the at least two snapshot time windows (14); and 4) using (i) at least the composite pseudorange and (ii) information relating to the ephemeris of GNSS satellites in at least a subset of the plurality of GNSS satellites (11) to determine the location of the GNSS receiver (16); and 5) transmitting the composite pseudorange and the composite reception time to the computing unit (18) via a gateway (17), the composite pseudorange replacing the pseudorange corresponding to the individual snapshot time window (14) in order to reduce the amount of data transmitted.

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