Ionospheric grid history and compression for GNSS positioning

Abstract

Methods, systems and devices for correcting ionospheric errors are described. In some aspects, a mobile device equipped with a global navigation satellite system (GNSS) receiver is configured to determine a positioning measurement of a GNSS signal. The mobile device is further configured to receive amplification data from an amplification system. When the amplification data for the current measurement cycle is not available, the mobile device can obtain amplification data associated with a total electron content (TEC) value (e.g., a vertical TEC value) during one or more previous measurement cycles. Based on the amplification data associated with the TEC value during one or more previous measurement cycles and the penetration point of the received GNSS signal, the ionospheric error in the positioning measurement of the GNSS signal can be determined and corrected.

Description

Background Art Technical Field

[0001] The present invention relates generally to the field of satellite based positioning and, more particularly, to error correction of Global Navigation Satellite System (GNSS) measurements based on information about ionospheric delays to achieve more accurate position determination.

[0002] 2. Description of related technologies

[0003] GNSS-based positioning involves estimating the position of a mobile receiver based on measurements obtained using reference signals from satellites, such as satellites of the Global Positioning System (GPS). GNSS-based positioning can estimate the position with high accuracy (e.g., several centimeters), but there are still errors due to signal delays, attenuation, multipath errors and other error sources. When errors are present, the accuracy may be significantly reduced (e.g., to several meters). An important source of error is the effect of the ionosphere on the propagation time of the reference signal. A mobile receiver may experience a significant delay in the GNSS signal as the GNSS signal travels through the layers of the ionosphere. The delay is caused by refraction and diffraction and is a function of the electron density in the ionosphere. The electron density can be expressed in terms of total electron count (TEC) values, more specifically, in TEC units (TECU). The electron density in the ionosphere above a given geographic area will vary over time and be affected by solar activity. Summary of the invention

[0004] Correction of errors in positioning measurements of GNSS signals, including errors due to ionospheric delays, is sometimes performed using information from an augmentation system. An augmentation system may be a satellite-based augmentation system (SBAS). Some augmentation systems are ground-based augmentation systems (GBAS). In an SBAS, one or more base stations on the ground (sometimes referred to as reference stations) perform measurements of signals from satellites in a positioning system (e.g., GNSS satellites). These measurements are used to calculate correction values ​​for broadcast to end-user devices (e.g., user equipment or UE), which are sometimes referred to as rovers. Broadcasting is typically performed via satellites of an augmentation system. In a GBAS, a reference receiver on the ground performs measurements related to calculating correction values ​​as differential GPS corrections, where the correction values ​​are broadcast using ground-based radio transmitters.

[0005] Augmentation data may be provided to a GNSS receiver (e.g., UE / rover) from a ground-based entity such as a base station. In some cases, such as for SBAS, a GNSS receiver may receive augmentation data directly from a satellite. Augmentation data may include correction information related to satellite orbits, clock errors, ionospheric delays, and / or other error sources. Augmentation data related to ionospheric delays may be generated based on a model of the ionosphere. Some ionospheric models reduce the layers of the ionosphere to a single layer at a certain altitude above the earth. Augmentation data may be in the form of an ionospheric grid product containing TEC values ​​for different points in a grid representing a geographic area. In some cases, the grid covers the entire earth. In other cases, the grid covers only a local area (e.g., a portion of a continent). Grid points are typically expressed as longitude and latitude coordinates. The accuracy of ionospheric models varies. For example, augmentation data from the Klobuchar ionospheric model (a set of parameters broadcast as ephemeris data) is not as accurate as the information in the SBAS grid product or the International GNSS Service (IGS) Global Ionospheric Map (GIM) grid product.

[0006] The availability of the augmented data generated using the ionospheric model is also different. Depending on the complexity of the ionospheric model, the amount of time used to calculate the ionospheric delay value or the value indicating it (e.g., TECU) and / or the amount of time for the GNSS receiver to receive and decode such values ​​may be large. Therefore, the latest ionospheric information related to the current position of the GNSS receiver may not always be available, and the GNSS receiver may have to wait until the next broadcast to receive updated, more relevant information. In addition, the GNSS receiver may not always be in an environment that is conducive to successfully decoding the ionospheric information. For example, if the UE is in an urban environment or other environment where the satellite signal is weak or blocked, only part of the ionospheric grid data can be successfully decoded. Using ground-based entities such as reference stations or base stations to replay ionospheric information is helpful to a certain extent because the UE no longer has to rely solely on satellite transmissions. However, replay is affected by bandwidth constraints and the availability of the communication network through which the ionospheric information is transmitted to the UE.

[0007] In order to improve the accuracy of the positioning estimate determined based on the correction of the ionospheric error, certain aspects of the present disclosure relate to a technique for estimating the ionospheric delay using historical ionospheric delay information in combination with current ionospheric delay information. The historical ionospheric delay information may be in the form of TEC values ​​from a previous measurement period, for example. The previous TEC values ​​may be related to the current measurement period because the electron density of a given geographic area tends to be similar at the same local time within a relatively short time span. For example, the TEC value at 3:00 a.m. yesterday may be the same or similar (e.g., within ten TECUs thereof) to the TEC value at 3:00 a.m. today. In addition, since TEC values ​​tend to change in a similar manner over consecutive or short intervals of several days, historical TEC values ​​may be used to identify trends and extrapolate current TEC values. Therefore, if the TEC value for the current measurement period is unavailable for some reason (e.g., the UE cannot receive or decode signals from the augmentation system satellites, or there are no base stations nearby that rebroadcast the ionospheric information), the UE may use the historical information to extrapolate the TEC value for the current measurement period. In this way, the accuracy of the resulting positioning estimate may be improved compared to using non-historical information alone.

[0008] Certain aspects of the present disclosure relate to reducing the amount of ionospheric information transmitted to and / or stored by a GNSS receiver such as a UE. The amount of ionospheric information can be reduced by generating a compressed representation of the ionospheric grid product. In some implementations, the compressed representation includes coefficients of spherical harmonics. If the compressed representation is transmitted to the UE, the UE is more likely to be able to receive and successfully decode the compressed representation because less time is spent in transmitting the compressed representation, thereby enabling the UE to access relevant ionospheric information faster and / or more frequently while reducing the risk of receiving incomplete ionospheric information (e.g., due to interruptions in signal reception). In addition, compression prior to transmission to the UE reduces data traffic between the UE and an entity providing the compressed representation (e.g., a server of an augmentation system).

[0009] In certain aspects, compression of ionospheric information is performed by the UE based on ionospheric information received by the UE (e.g., grid products from SBAS satellites). The compressed ionospheric information may be stored as historical information in a local memory of the UE for use in extrapolating TEC values. Because the historical information is compressed, it may be stored more efficiently using less memory. In this way, the UE may generate its own historical information for later use by saving "current" ionospheric information, and is not dependent on historical information that may be subsequently obtained from an external source (such as an augmentation system satellite or base station). Alternatively, the historical ionospheric information may be transmitted to the UE in a compressed form, which has similar benefits as transmitting a compressed representation of non-historical ionospheric information.

[0010] In certain aspects, a method performed at a mobile device for correcting ionospheric errors involves determining a positioning measurement of a GNSS signal. The method also involves obtaining amplification data associated with TEC values ​​during one or more previous measurement cycles. The method also involves obtaining a penetration point of the GNSS signal and determining an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0011] In certain aspects, a mobile device includes: a GNSS receiver configured to receive GNSS signals from navigation satellites. The mobile device also includes: a wireless communication interface configured to communicate with an amplification system. The mobile device also includes: a memory; and one or more processing units communicatively coupled to the GNSS receiver, the wireless communication interface, and the memory. The one or more processing units are configured to determine a positioning measurement of the GNSS signal and obtain amplification data associated with a total electron content (TEC) value during one or more previous measurement cycles. The one or more processing units are further configured to obtain a penetration point of the GNSS signal and determine an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0012] In certain aspects, a non-transitory computer-readable medium has instructions stored thereon that, when executed by one or more processing units of a mobile device, cause the one or more processing units to perform the following operations: determine a positioning measurement of a GNSS signal; obtain amplification data associated with a total electron content (TEC) value during one or more previous measurement cycles; obtain a penetration point of the GNSS signal; and determine an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0013] In certain aspects, a system includes: a GNSS receiver configured to receive GNSS signals from navigation satellites. The system also includes: a wireless communication interface configured to communicate with an amplification system. The system also includes: one or more processing units configured to determine a positioning measurement of the GNSS signal. The system also includes: means for obtaining amplification data associated with a total electron content (TEC) value during one or more previous measurement cycles; means for obtaining a penetration point of the GNSS signal; and means for determining an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a diagram of a positioning system in combination with an amplification system, according to an embodiment.

[0015] Figure 2 A signal from a GNSS satellite is shown propagating through the ionosphere and arriving at a GNSS receiver.

[0016] Figure 3 is a simplified block diagram of a system according to an embodiment.

[0017] Figure 4A and Figure 4B is a timing diagram illustrating different techniques for extrapolating the current TEC value according to some embodiments.

[0018] Figure 5 is a flow chart of a method for determining ionospheric errors in positioning measurements of GNSS signals according to an embodiment.

[0019] Figure 6 is a flow chart of a method for compressing augmentation data based on spherical harmonics according to an embodiment.

[0020] Figure 7 The mathematical expressions of spherical harmonics are shown.

[0021] Figure 8 and Fig. 9 Vectors that can be used to represent spherical harmonics are shown.

[0022] Fig. 10A is a graphical representation of exemplary TEC values ​​for geographic regions.

[0023] Fig. 10B Is compression from Fig. 10A Graphical representation of exemplary results of TEC values.

[0024] Fig.11 An embodiment of a UE is shown that may be utilized in the embodiments described herein.

[0025] Similar reference numerals in the various drawings indicate similar elements according to certain example implementations. In addition, multiple instances of the element can be indicated by adding a letter or hyphen and a second numeral after the first numeral of the element. For example, multiple instances of element 110 can be indicated as 110-1, 110-2, 110-3, etc. or as 110a, 110b, 110c, etc. When only the first numeral is used to refer to such an element, any instance of the element (for example, the element 110 in the previous example will refer to elements 110-1, 110-2 and 110-3 or to elements 110a, 110b and 110c) should be understood. DETAILED DESCRIPTION

[0026] Several illustrative embodiments will now be described with reference to the accompanying drawings which form a part hereof.While some embodiments are described below that may implement one or more aspects of the present disclosure, other embodiments may be used and various modifications may be made without departing from the scope of the present disclosure.

[0027] As used herein, an "RF signal" includes electromagnetic waves that transmit information through the space between a transmitter (or transmitting device) and a receiver (or receiving device). As used herein, a transmitter may send a single "RF signal" or multiple "RF signals" to a receiver. However, due to the propagation characteristics of RF signals through multipath channels, a receiver may receive multiple "RF signals" corresponding to each transmitted RF signal. The same transmitted RF signal on different paths between a transmitter and a receiver may be referred to as a "multipath" RF signal. RF signals transmitted from a Global Navigation Satellite System (GNSS) satellite are sometimes referred to herein as "GNSS signals".

[0028] The embodiments described herein may be implemented using any positioning system in which a UE is communicatively coupled to one or more sources of augmentation data including information that can be used to correct measurement errors caused by signal propagation through the ionosphere. Figure 1 An example of a positioning system suitable for implementing one or more embodiments is shown in FIG. Figure 1 The positioning system in the embodiment described herein is provided only as an example and is provided to illustrate how different entities can interact with the UE with respect to determining the location of the UE. In practice, the positioning system implemented according to the embodiments described herein may include a positioning system as compared to Figure 1 More or fewer components as depicted in .

[0029] Figure 1 1 is a simplified illustration of a positioning system 100 according to an embodiment, in which a UE 105, a location server (LS) 160, and / or other components of the positioning system 100 may use the techniques provided herein for determining an estimated position of the UE 105. The techniques described herein may be implemented by one or more components of the positioning system 100. The positioning system 100 may include a UE 105, one or more satellites 110 (also referred to as space vehicles (SVs)) for a GNSS such as a global positioning system (GPS), a base station 120, an access point (AP) 130, a LS 160, a network 170, and an external client 180. In general, the positioning system 100 may estimate the position of the UE 105 based on RF signals received by and / or transmitted from the UE 105 and the known positions of other components (e.g., GNSS satellites 110, base stations 120, APs 130) that transmit and / or receive RF signals.

[0030] It should be noted that Figure 1Only a generalized illustration of various components is provided, any or all of which may be utilized as appropriate, and each component may be repeated as needed. Specifically, although only one UE 105 is illustrated, it should be understood that many UEs (e.g., hundreds, thousands, millions, etc.) may utilize the positioning system 100. Similarly, the positioning system 100 may include more than one UE 105. Figure 1 100. The illustrated connections connecting the various components in the positioning system 100 include data and signaling connections, which may include additional (intermediate) components, direct or indirect physical and / or wireless connections, and / or additional networks. In addition, the components can be rearranged, combined, separated, replaced and / or omitted according to the desired functionality. In some embodiments, for example, the external client 180 can be directly connected to the LS 160. Those of ordinary skill in the art will recognize many modifications to the illustrated components.

[0031] Depending on the desired functionality, network 170 may include any one of a variety of wireless and / or wired networks. Network 170 may, for example, include any combination of public and / or private networks, local area networks and / or wide area networks, etc. In addition, network 170 may utilize one or more wired and / or wireless communication technologies. In some embodiments, network 170 may include, for example, cellular or other mobile networks, wireless local area networks (WLANs), wireless wide area networks (WWANs), and / or the Internet. Examples of network 170 include long-term evolution (LTE) wireless networks, fifth-generation (5G) wireless networks (also referred to as new air interface (NR) wireless networks or 5GNR wireless networks), Wi-Fi WLANs, and the Internet. LTE, 5G, and NR are wireless technologies defined or being defined by the Third Generation Partnership Project (3GPP). Network 170 may also include more than one network and / or more than one type of network.

[0032] The base station 120 and the access point (AP) 130 are communicatively coupled to the network 170. In some embodiments, the base station 120 may be owned, maintained and / or operated by a cellular network provider and may employ any of a variety of wireless technologies, as described herein below. Depending on the technology of the network 170, the base station 120 may include a Node B, an evolved Node B (eNodeB or eNB), a transceiver base station (BTS), a radio base station (RBS), an NR Node B (gNB), a next generation eNB (ng-eNB), etc. In the case where the network 170 is a 5G network, the base station 120 as a gNB or ng-eNB may be part of a next generation radio access network (NG-RAN) that may be connected to a 5G core network (5GC). The AP 130 may include, for example, a Wi-Fi AP or Thus, UE 105 can send and receive information with network-connected devices (such as LS 160) by accessing network 170 via base station 120 using first communication link 133. Additionally or alternatively, because AP 130 can also be communicatively coupled with network 170, UE 105 can use second communication link 135 to communicate with Internet-connected devices (including LS 160).

[0033] As used herein, the term "base station" may generally refer to a single physical transmission point or multiple co-located physical transmission points that may be located at the base station 120. The physical transmission point may include an antenna array of the base station (e.g., as in a multiple-input multiple-output (MIMO) system and / or where the base station employs beamforming). The term "base station" may additionally refer to multiple non-co-located physical transmission points, which may be a distributed antenna system (DAS) (a network of spatially separated antennas connected to a common source via a transmission medium) or a remote radio head (RRH) (a remote base station connected to a serving base station). Alternatively, the non-co-located physical transmission point may be a serving base station that receives measurement reports from the UE 105 and a neighboring base station whose reference RF signal the UE 105 is measuring.

[0034] As used herein, the term "cell" may generally refer to a logical communication entity for communicating with base station 120, and may be associated with an identifier (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) for distinguishing adjacent cells operating via the same or different carriers. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine type communication (MTC), narrowband Internet of Things (NB-IoT), enhanced mobile broadband (eMBB), or other protocols) that may provide access to different types of devices. In some cases, the term "cell" may refer to a portion of a geographic coverage area (e.g., a sector) over which a logical entity operates.

[0035] LS160 may include a server and / or other computing device configured to determine an estimated location of UE 105 and / or provide data (e.g., “assistance data”) to UE 105 to facilitate location determination. According to some embodiments, LS160 may include a Home Secure User Plane Location (SUPL) Location Platform (H-SLP), which may support a SUPL User Plane (UP) location solution defined by the Open Mobile Alliance (OMA), and may support location services for UE 105 based on subscription information about UE 105 stored in LS160. In some embodiments, LS160 may include a Discovery SLP (D-SLP) or an Emergency SLP (E-SLP). LS 160 may also include an Enhanced Serving Mobile Location Center (E-SMLC), which supports positioning of UE 105 using a Control Plane (CP) location solution for LTE radio access of UE 105. LS 160 may also include a location management function (LMF) that supports positioning of UE 105 using a control plane (CP) positioning solution for NR radio access of UE 105. In a CP positioning solution, from the perspective of network 170, signaling for controlling and managing the positioning of UE 105 may use existing network interfaces and protocols and be exchanged as signaling between elements of network 170 and with UE 105. In a UP positioning solution, from the perspective of network 170, signaling for controlling and managing the positioning of UE 105 may be exchanged between LS 160 and UE 105 as data (e.g., data transmitted using Internet Protocol (IP) and / or Transmission Control Protocol (TCP)).

[0036] As previously mentioned, the estimated position of UE 105 may be based on measurements of RF signals transmitted from and / or received by UE 105. In particular, these measurements may provide information about the relative distances and / or angles of UE 105 and one or more components in positioning system 100 (e.g., GNSS satellites 110, APs 130, base stations 120). The estimated position of UE 105 may be estimated geometrically (e.g., using multi-angle measurements and / or multilateration) based on the distance and / or angle measurements along with the known positions of the one or more components.

[0037] Although the ground components (such as AP 130 and base station 120) can be fixed, the embodiments are not limited thereto. Mobile components can be used. In addition, in some embodiments, based at least in part on the UE 105 and one or more other UEs ( Figure 1The position of UE 105 is estimated by measuring the RF signals transmitted between the UEs (not shown) (the one or more other UEs may be mobile). Direct communication between UEs in this manner may include sidelink and / or similar device-to-device (D2D) communication technologies. The sidelink defined by 3GPP is a form of D2D communication based on cellular LTE and NR standards.

[0038] The estimated position of the UE 105 may be used in various applications, such as to assist a user of the UE 105 in direction finding or navigation or to assist another user (e.g., associated with an external client 180) in locating the UE 105. "Position" is also referred to herein as a "position estimate," "estimated position," "position," "position estimate," "position fix," "estimated position," "position fix," or "fix." The position of the UE 105 may include an absolute position of the UE 105 (e.g., latitude and longitude and possibly altitude) or a relative position of the UE 105 (e.g., a position expressed as a distance north or south, east or west, and possibly above or below some other known fixed position or some other location (such as the location of the UE 105 at some known previous time)). The position may also be specified as a geodetic location (such as latitude and longitude) or a civic location (e.g., in the form of a street address or using other location-related names and labels). The location may further include uncertainty or error indications, such as the horizontal and possibly vertical distances over which the location is expected to be in error or an indication of an area or volume (eg, a circle or ellipse) within which the UE 105 is expected to be located with some confidence level (eg, 95% confidence).

[0039] The external client 180 may be a web server or remote application that may have some association with the UE 105 (e.g., may be accessed by a user of the UE 105), or may be a server, application, or computer system that provides location services to one or more other users, which may include obtaining and providing the location of the UE 105 (e.g., to enable services such as friend or relative finding, asset tracking, or child or pet location). Additionally or alternatively, the external client 180 may obtain the location of the UE 105 and provide it to emergency service providers, government agencies, etc.

[0040] UE 105 may include and / or be referred to as a device, a mobile device, a wireless device, a mobile terminal, a terminal, a mobile station (MS), a terminal (SET) enabled with secure user plane location (SUPL), or some other name. In addition, UE 105 may correspond to a cellular phone, a smart phone, a laptop, a tablet computer, a personal data assistant (PDA), an Internet of Things (IoT) device, or some other portable or mobile device. Typically, although not necessarily, UE 105 may use one or more radio access technologies (RATs) such as Global System for Mobile Communications (GSM), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Long Term Evolution (LTE), High Rate Packet Data (HRPD), IEEE 802.11 Bluetooth, Worldwide Interoperability for Microwave Access (WiMAX TM ), 5G NR, etc. to support wireless communications. UE 105 may also support wireless communications to connect to other networks such as the Internet.

[0041] UE 105 may include a single entity or may include multiple entities, such as in a personal area network in which a user may employ audio, video, and / or data I / O devices, and / or body sensors and separate wired or wireless modems. The estimate of the location of UE 105 may be referred to as location, location estimate, location fix, fix, position, position estimate, or position fix, and may be geodetic, providing location coordinates (e.g., latitude and longitude) about UE 105, which may or may not include an altitude component (e.g., altitude; height above or depth below ground level, floor level, or basement level). Alternatively, the location of UE 105 may be expressed as a municipal location (e.g., expressed as a postal address or a designation of a point or smaller area in a building (such as a specific room or floor)). The location of UE 105 may also be expressed as an area or volume (geographically or municipally defined) within which UE 105 is expected to be located with a certain probability or confidence level (e.g., 67%, 95%, etc.). The location of the UE 105 may also be a relative location, including, for example, a distance and direction or relative X, Y (and Z) coordinates defined relative to some origin at a known location, which may be defined geodetically, in municipal form, or with reference to a point, area, or volume indicated on a map, floor plan, or building plan. In the description contained herein, the use of the term location may include any of these variations unless otherwise indicated. When calculating the location of the UE, local X, Y, and possibly Z coordinates are typically solved, and then the local coordinates are converted to absolute coordinates (e.g., with respect to latitude, longitude, and altitude above or below mean sea level) if necessary.

[0042] Using UE-assisted positioning methods, the UE 105 may obtain positioning measurements and send these measurements to a location server (e.g., LS 160) for use in calculating a position estimate for the UE 105. For example, the positioning measurements may include one or more of the following: received signal strength indication (RSSI), round trip signal propagation time (RTT), reference signal received power (RSRP), reference signal received quality (RSRQ), time of arrival (TOA), reference signal time difference (RSTD), AOA, differential AOA (DAOA), AOD, or timing advance (TA). The positioning measurements may additionally or alternatively include measurements of RAT-independent positioning methods, such as GNSS (e.g., GNSS pseudoranges with respect to GNSS satellites 110, GNSS code phase, and / or GNSS carrier phase), WLAN, etc.

[0043] Using UE-based positioning methods, UE 105 may obtain positioning measurements (e.g., which may be the same or similar to positioning measurements of UE-assisted positioning methods), and may further calculate the position of UE 105 (e.g., with the assistance data received from a location server such as LS 160). Additionally, in some cases, UE-based positioning methods may involve sidelink communications with another UE.

[0044] Using network-based positioning methods, one or more base stations, one or more APs, or some other entity connected to the network may obtain positioning measurements (e.g., measurements of RSSI, RTT, RSRP, RSRQ, AOA, or TOA) of signals transmitted by UE 105, and / or may receive measurements obtained by UE 105 and may send these measurements to a location server (e.g., LS160) to calculate a position estimate for UE 105.

[0045] like Figure 1As shown, the positioning system 100 may include one or more augmentation system satellites 115 (e.g., SBAS satellites). In some cases, the satellites 115 may be operated by an entity different from the entity operating the GNSS satellites 110. Therefore, the augmentation system to which the satellites 115 belong may be considered a separate system, or in some cases, a subsystem of the positioning system 100. In order to generate augmentation data, one or more reference stations (e.g., one or more base stations in the base stations 120) may receive signals from the GNSS satellites 110. The signals received by the reference stations may be the same signals as the signals received by the UE 105. The reference stations may perform measurements using the GNSS satellite signals to calculate one or more correction values, such as a value indicating ionospheric delay. The correction values ​​may be transmitted from the reference station (or a master station in communication with multiple reference stations) to the augmentation system satellites 115 for transmission (e.g., broadcast) to the UE 105. Alternatively or additionally, the correction values ​​may be transmitted to the UE 105 using a ground-based infrastructure. For example, a correction message including one or more correction values ​​may be sent to UE 105 from base station 120 via wireless link 133 or from AP 130 via wireless link 135 .

[0046] The correction values ​​sent to UE 105 include values ​​that can be used to correct for one or more types of errors (e.g., satellite clocks and orbits, ionospheric and tropospheric delays, phase wraparound, station displacements including solid Earth tides, ocean loading, and / or polar tides). In some cases, the correction values ​​are calculated as differential corrections made using observations from a highly accurate GNSS receiver at a reference location (e.g., base station 120) and assuming that these observations have virtually the same errors.

[0047] To be effective, correction values ​​should be supplied to the UE 105 relatively frequently (e.g., once every few minutes). However, with respect to ionospheric information, real-time correction values ​​may not always be available depending on various factors such as the complexity of the ionospheric model used to calculate the correction information and / or the amount of information to be transmitted. For example, because the ionospheric delay information is regional (a 5 degree by 5 degree longitude grid covering a latitude range of -55 degrees to 55 degrees), the WAAS-based ionospheric delay information may be transmitted to the UE 105 in substantially real-time (typically with a delay of approximately ten minutes). In contrast, the ionospheric delay information provided by the IGS GIM-based augmentation system has global coverage and is typically generated as a result of processing performed by hundreds or more reference stations, so generating a complete ionospheric grid product may take hours or even days.

[0048] Figure 22. Signal 201 is shown being transmitted from GNSS satellite 240 (e.g., one of GNSS satellites 110) to a GNSS receiver (e.g., to a UE at location 205 on Earth 210). Signal 201 propagates through ionosphere 220 before reaching GNSS receiver. Ionosphere 220 may be modeled as a thin layer (a "thin shell" model) located at a certain altitude (e.g., 350 kilometers) above the surface of Earth 210. Signal 201 intersects ionosphere 220 at penetration point 225. As shown in FIG. Figure 3 As shown, signal 201 arrives at ionosphere 220 at angle 232 relative to zenith direction 230, but arrives at the GNSS receiver at zenith angle 234 that is generally different from angle 232. Penetration point 225 may be calculated based on the location of the GNSS receiver (e.g., based on the latitude, longitude, elevation, and azimuth of the UE) and the location of the GNSS satellite transmitting the GNSS signal (e.g., GNSS satellite 240).

[0049] The ionospheric delay information (e.g., in the form of an ionospheric grid product) may include a set of TEC values ​​for different locations in the covered geographic area. In general, the ionospheric delay associated with the location of the GNSS receiver can be determined by looking up the TEC value at a specific grid location represented by a latitude-longitude pair. The grid location is not the location of the GNSS receiver itself (e.g., the location to be estimated), but the location of the penetration point 225. However, as discussed above, the penetration point can be easily calculated based on the location of the GNSS receiver. In the case of a UE, the approximate location of the UE (e.g., the last known or estimated location) may be sufficient to determine the corresponding penetration point. In some cases, the known location of a base station (e.g., base station 120) or other network entity near the UE may be used to determine the penetration point.

[0050] Figure 3 3 is a simplified block diagram of a system 300 according to an embodiment. The system 300 includes an augmentation system 310, a satellite 315 (eg, augmentation system satellite 115) that is part of the augmentation system 310, and a UE 320. Figure 3 The system 300 in FIG. 1 is provided only as an example and is used to illustrate how a GNSS receiver such as a UE 320 may receive ionospheric delay information from an augmentation system according to the techniques described herein. In practice, a system implemented according to the embodiments described herein may include a system that is different from the system described herein. Figure 3 More or fewer components as depicted in .

[0051] like Figure 3 As shown, the augmentation system 310 may include one or more base stations 312 and is configured to maintain ionospheric information 314. The base stations 312 may correspond to Figure 110 and is configured to generate ionospheric information 314 based on measurements of GNSS satellite signals (e.g., signals transmitted by GNSS satellites 110). Base station 312 may be configured to generate one or more sets of grid values ​​for inclusion in ionospheric information 314, each set of grid values ​​corresponding to a "snapshot" of the ionosphere over one or more geographic regions at a particular point in time. Grid values ​​are values ​​(e.g., TEC values ​​or values ​​derived from TEC values) indicative of ionospheric delay and may be calculated based on measurements of GNSS satellite signals as performed by at least one base station 312. TEC values ​​are typically provided as vertical TEC values, which are calculated by integration along a vertical path in the zenith direction of an observer (e.g., base station 312). Some implementations may use tilted TEC values ​​instead of vertical TEC. Tilt TEC values ​​are calculated by integration along a path of travel from a GNSS satellite to an observer. In practice, vertical TEC tends to be used more frequently because tilted TEC depends on azimuth and elevation, and therefore multiple tilted TEC values ​​are calculated for each penetration point. In most cases, correction for ionospheric delay can be adequately performed using vertical TEC since only a single value exists for each penetration point.

[0052] The ionospheric information 314 may include current ionospheric information, i.e., information about ionospheric delays for a current measurement period for the UE 320. In this regard, the current ionospheric information may correspond to the most recent grid product generated by the augmentation system 310. Additionally or alternatively, the ionospheric information 314 may include historical information about ionospheric delays for previous measurement periods. As discussed above, the frequency at which the ionospheric delay information becomes available may vary. For example, if the ionospheric information 314 includes an SBAS grid product, the SBAS grid product may be calculated using measurements performed by the base station 312 and transmitted to the UE 320 in substantially real time (e.g., every ten minutes) so as to be associated with the current measurement period. In some cases, the ionospheric information 314 may include an IGS GIM grid product calculated every few hours or days based on measurements performed by the base station 312. Thus, in some embodiments, multiple databases may be used to store the ionospheric information 314, each of which maintains ionospheric delay information derived from a separate source. For example, augmentation system 310 may include a first database for storing SBAS grid volumes and a second database for storing IGS GIM grid volumes.

[0053] UE 320 may include a wireless communication subsystem 322, a measurement engine 324, and a memory 330. Wireless communication subsystem 322 may include one or more wireless receivers configured to communicate with augmentation system 310. For example, wireless communication subsystem 322 may communicatively couple UE 320 to one or more base stations 312, a server (not shown) maintaining a database storing ionospheric information 314, and / or satellites 315. Additionally, the wireless communication subsystem may include one or more GNSS receivers configured to receive signals from GNSS satellites (e.g., GNSS satellites 110) and perform positioning operations using measurements of the signals from the GNSS satellites.

[0054] The measurement engine 324 may be implemented in hardware and / or software and configured to perform measurements of GNSS signals and positioning operations. Figure 1 As discussed, there are various positioning methods, including UE-based positioning methods, UE-assisted positioning methods, and network-based positioning methods. Depending on which of these types of positioning methods the UE has been configured to support, the measurement engine 324 may obtain one or more types of measurements for each GNSS signal transmitted by the GNSS satellite constellation. These measurements may be used to estimate the position of the UE 320 locally, or alternatively transmitted to an external entity for remote estimation of the UE's position.

[0055] Measurement engine 324 may be configured to use ionospheric information received by UE 320 (possibly along with other types of correction information received by UE 320 from augmentation system 310, such as clock bias correction information, orbit correction information for GNSS satellites, etc.) to correct the measurements it performs. Figure 3 As shown, ionospheric information received by the UE may be stored in a memory 330 and may include current ionospheric information 340 and historical ionospheric information 350 .

[0056] The memory 330 may include one or more types of memory devices, including volatile and / or non-volatile storage memory. With respect to the historical ionospheric information 350, the information may be stored in non-volatile memory so that the information 350 may be retrieved later even if the UE 320 is temporarily powered off. In some implementations, the current ionospheric information 340 may be maintained in a storage buffer (e.g., in working memory) and transferred to another portion of the memory 330 for storage as the historical ionospheric information 350. Additionally, in some implementations, at least some of the ionospheric information in the system 300 (e.g., the ionospheric information 314 and / or the ionospheric information in the memory 330 of the UE 320) may be stored in a compressed form. Exemplary compression techniques are described below in conjunction with Figures 6 to 9 to describe.

[0057] The current ionospheric information 340 may include any information indicating the degree of error in the measurement of the GNSS signal, wherein the error is the result of the GNSS signal propagating through the ionosphere. For example, as discussed above, information about ionospheric delay may be provided in the form of an ionospheric grid product, which includes TEC values ​​for different points in a grid representing a geographic area or, more specifically, the ionosphere above the geographic area. Therefore, the information 340 may be in the form of a lookup table containing TEC values ​​indexed according to longitude and latitude coordinates, wherein the longitude and latitude coordinates correspond to possible penetration points. The information 340 may be used to estimate the delay encountered by the GNSS signal due to propagation through the ionosphere. Alternatively or additionally, in some implementations, the information 340 may include a delay correction value derived from the TEC value. Such correction values ​​may be satellite-specific and / or frequency-specific. For example, if the position of the UE 320 is estimated based on the measurement of the GNSS signal transmitted on the L1 band in addition to the measurement of the GNSS signal transmitted on the L2 band, the information 340 may include a correction value for the L1 signal and a separate correction value for the L2 signal. In some implementations, ionospheric delay information stored as grid values ​​or as correction values ​​specific to a satellite and for a particular frequency band (e.g., L1) may also be used to correct measurements at a different frequency (e.g., L2) in appropriate proportions to account for the frequency difference.

[0058] The information 340 corresponds to a first subset of the ionospheric information 314 maintained by the augmentation system 310 and is current because it is associated with a measurement period covering the duration of time that the UE 320 receives and decodes a set of GNSS signals to obtain one or more types of measurements related to estimating the current position of the UE 320. Thus, the information 340 represents the delay experienced by the GNSS signals received during the current measurement period. The length of the measurement period may depend on the configuration of the UE, and different UEs may be configured with different measurement periods. The information 340 may be transmitted to the UE 320 via a satellite (e.g., satellite 315) and / or by a ground-based component of the augmentation system 310 (e.g., base station 312 or server that maintains the ionospheric information 314). In some implementations, the information 340 may correspond to an SBAS grid volume.

[0059] The historical ionospheric information 350 corresponds to a second subset of the ionospheric information 314 maintained by the augmentation system 310 and includes delay information associated with one or more measurement cycles prior to the current measurement cycle. The information 350 may be an older version of the information 340. For example, after receiving the information 340, the UE 320 may store the information 340 as the historical ionospheric information 350 for later use. Alternatively, the information 340 may be collected by the augmentation system (e.g., simultaneously with transmitting the information 340 to the UE) and stored in a database before being sent to the UE as historical information. For example, the augmentation system 310 may be configured to collect ionospheric information over multiple measurement cycles to transmit to the UE in a single batch as the historical ionospheric information 350. Therefore, the information 350 may eventually be updated to include the same values ​​as the information 340, but not necessarily the same values ​​as the current ionospheric information received by the UE. In some implementations, the information 350 may correspond to an IGS GIM grid product.

[0060] Figure 3 Information 350 is depicted as being transmitted from the augmentation system 310 to the UE 320 as historical information. In some cases (e.g., when the IGS GIM model is used), this may be due to the relatively slow rate at which the information 350 becomes available. However, as noted above, the UE 320 may generate its own historical information based on the current ionospheric information 340. For example, in some implementations, the historical information 350 may include historical GIM grid values ​​and historical SBAS grid values, where the historical GIM grid values ​​are transmitted to the UE by a server of the augmentation system 310, and the historical SBAS grid values ​​are locally generated copies of the SBAS grid values ​​received as the current ionospheric information 340.

[0061] Figure 4A and Figure 4B is a timing diagram showing different techniques for extrapolating the current TEC value. Figure 4A and Figure 4B The data points shown are TEC values, but the extrapolation technique can be applied to any information indicative of ionospheric delay (e.g., correction values ​​derived from TEC values). Figure 4A In the case where the UE receives (for example, as Figure 33) and successfully decodes the TEC value for each of times T0, T1, and T2. As shown, times T0 to T2 may correspond to an arbitrary sequence of time points, for example, three different times during a day. At some time between T2 and the next time point T3, the UE stops receiving TEC values ​​or fails to successfully decode the TEC value, so that the current TEC value from the most recent set of grid values ​​that may potentially be transmitted to the UE from the augmentation system becomes unavailable for T3. In order to determine the TEC value for T3 and / or the TEC value for any time between T2 and T3, the UE may perform an extrapolation operation using the TEC values ​​at T0 to T2. The extrapolation operation may involve, for example, fitting a line, a curve, a piecewise polynomial, or some other mathematical function through each of the TEC values ​​at T0, T1, and T2 and extending the line or curve to T3, such as Figure 4A shown.

[0062] Figure 4A The illustrated technique relates to the most recently obtained TEC value. In this regard, the TEC values ​​at T0 to T2 may be used to extrapolate the ionospheric delay for T3 in the current measurement cycle, even though the TEC values ​​at T0 to T2 are for a time point earlier than the TEC value at T3. Figure 4A and Figure 4B In the example of , the measurement period may span a period within a day (e.g., a ten minute window). Typically, T0 to T2 will be time points that are a few minutes apart from one time point to the next (e.g., two minutes apart), but the time intervals between data points may be longer or shorter. For example, T0 and T1 may be one hour apart. Thus, one method of extrapolating the missing TEC values ​​for the current measurement period is to use two or more TEC values ​​from the current measurement period or, in general, from any measurement period for which the most recent set of grid values ​​received from the amplification system was valid. Although Figure 4A The illustrated extrapolation technique is relatively simple to implement without historical information spanning a longer period of time (e.g., the previous day, past multiple days, or some other period covered by an older set of grid values), but the technique does not take into account expected periodic changes, such as changes over the course of a day as expected based on similar changes during another day. Figure 4A The technology does not always provide the best performance. Figure 4B A more accurate but also more complicated extrapolation technique is shown in .

[0063] Figure 4BAn example of using historical TEC values ​​to extrapolate TEC values ​​is shown. Given a trend of TEC values ​​repeating between consecutive or short-interval days, a trend in TEC values ​​for a current measurement period may be identified based on TEC values ​​from a previous measurement period (e.g., a measurement period corresponding to the previous day, or generally, any measurement period covered by an older set of grid values). In this regard, the historical ionospheric information may include TEC values ​​that are old enough to establish a trend that the TEC values ​​previously changed in the same or substantially similar manner as the TEC values ​​are currently changing. For example, TEC values ​​from yesterday, two days ago, or even a week ago may indicate how TEC values ​​are changing on a given day. As shown in FIG. Figure 4B As shown, the TEC value at T3 today (e.g., 3:00 a.m.) can be determined using the TEC value at T4 yesterday (e.g., 4:00 a.m.). Alternatively or additionally, the TEC value at T3 yesterday can be used. For example, instead of fitting a line or curve only through the data points at T0 to T2, the data points at T0 to T2 (or a subset thereof) can be used in combination with the data points at T3 yesterday and T4 yesterday (or a subset thereof) to perform the fit. Figure 4B The value obtained by extrapolating T3 using the technique can be expected to be better than Figure 4A The extrapolated value in is closer to the actual TEC value at T3 today.

[0064] In some implementations, the extrapolated value is a weighted sum of: (1) TEC values ​​observed during a previous measurement period or period covered by an older set of grid values ​​(e.g., yesterday T0 to T4) and / or (2) TEC values ​​observed during a current measurement period or period covered by a more recent set of grid values ​​(e.g., today T0 to T2). Figure 4B The example described uses both (1) and (2). In contrast, Figure 4A is an example of an extrapolation using only (2). Each of the TEC values ​​used to perform the extrapolation may have a corresponding weighting factor that scales the TEC value up or down, where the sum of all weighting factors is set to a certain value, such as a value of one. Thus, one method of extrapolating missing TEC values ​​for the current measurement cycle is to use one or more TEC values ​​from a previous measurement cycle in combination with one or more TEC values ​​from the current measurement cycle.

[0065] As Figure 4A and Figure 4BAn alternative to the illustrated extrapolation technique, a faster but potentially less accurate option for determining missing TEC values ​​for the current measurement cycle is to simply replace the missing TEC values ​​with TEC values ​​from a previous measurement cycle or a period covered by an older set of grid values. For example, it may be assumed that the TEC value at T3 yesterday is the same as the TEC value at T3 today. This alternative approach may be viewed as a special case of the weighted sum approach described above, in which full weight (e.g., a weighting factor of one) is applied to the TEC values ​​observed in the previous measurement cycle or a period covered by an older set of grid values. In summary, the extrapolation may be based on current values ​​(values ​​associated with the current measurement cycle or the most recent set of grid values), historical values ​​(values ​​associated with the previous measurement cycle or a period covered by an older set of grid values), or a combination of both current and historical values.

[0066] Figure 5 is a flow chart of a method 500 for determining ionospheric errors in positioning measurements of GNSS signals according to an embodiment. Figure 5 The illustrated functional means may be performed by hardware and / or software components of a mobile device equipped with a GNSS receiver (e.g., one or more processors of a UE). Fig.11 It is shown in FIG. 1 and will be described in more detail below.

[0067] At 502, positioning measurements of GNSS signals are determined. The GNSS signals for which positioning measurements are determined may be GNSS signals received by the UE during a current measurement period. In addition to the GNSS signals, the UE may be configured to receive augmentation data from an augmentation system, such as non-historical augmentation data associated with the current measurement period. In some cases, there is no available augmentation data associated with the current measurement period. This may occur, for example, when a server of the augmentation system is offline or there are no signals from satellites of the augmentation system or signals from satellites of the augmentation system are blocked outside the location of the UE. In other cases, the UE may receive a partial set of non-historical augmentation data. When non-historical augmentation data (e.g., augmentation data for the current measurement period) is not available, ionospheric errors may be determined based on historical augmentation data, for example, according to the functionality in blocks 504, 506, and 508 discussed below.

[0068] At 504, amplification data associated with TEC values ​​during one or more previous measurement cycles (e.g., TECU during the past day or days) is obtained. In some cases, obtaining amplification data at 504 may be in response to determining that amplification data for the current measurement cycle is not available (e.g., determining that the TEC value for T3 is not available, as described above in conjunction with Figure 4A and Figure 4BIn addition, the augmented data obtained in 504 may include TEC values ​​for different locations (e.g., different points in an ionospheric grid of a map representing the ionosphere over one or more geographic regions).

[0069] The augmentation data obtained in 504 may be generated by the UE itself or obtained from an augmentation system such as Figure 3 The augmentation system 310 in block 504 communicates to the UE. Thus, in some implementations, the functionality in block 504 involves retrieving historical TEC values ​​from a memory of the UE. In some implementations, the augmentation data obtained in block 504 is data obtained from one or more SBAS satellites (e.g., transmitted from one or more WAAS satellites during the current measurement cycle). In other implementations, the augmentation data obtained in 504 may come from one or more remote / network entities (e.g., a server of the augmentation system) and may correspond to data generated using an IGM GIM model of the ionosphere. Additionally, in some implementations, the augmentation data obtained in 504 may correspond to a compressed representation of the augmentation data (e.g., a compressed representation of an SBAS or IGM GIM grid). As described below in conjunction with Figure 6 An example of a method for compressing augmentation data for use as historical augmentation data is described.

[0070] As an alternative to obtaining TEC values, in some implementations, the augmentation data obtained in block 504 is data representing a computer-executable model, wherein the model is configured to calculate ionospheric delay and / or corresponding correction values ​​for a specific point in time and at a specific location (e.g., a time in a current measurement cycle, at a location corresponding to a penetration point of a GNSS signal). The model may be an algorithmic model or a machine learning (ML) model, and may be generated using historical augmentation data. For example, an ML model may be trained using historical augmentation data (e.g., historical TEC values) as training data to estimate ionospheric delay. Training of the ML model may, for example, involve adjusting weights of a neural network using back propagation based on the difference between actual ionospheric delay values ​​and ionospheric delay values ​​estimated by the neural network based on input time and input location, wherein the actual ionospheric delay values ​​are known values ​​for a given set of historical augmentation data. Thus, the augmentation data obtained in block 504 may include one or more parameters of an ML model (e.g., weights of a neural network), or, in general, any set of one or more parameters of a computer-executable model generated based on historical augmentation data. Such parameters may be communicated to the UE from a server or other component of the augmentation system. Alternatively, the UE may determine parameters for its own model based on historical augmentation data that the UE has received. Thus, TEC values ​​covering one or more previous measurement periods need not be used directly to determine the ionospheric delay. At 506, a penetration point of the GNSS signal is obtained. The penetration point in 506 corresponds to an ionospheric position that the GNSS signal passed through before the UE received the GNSS signal. As described above in conjunction with Figure 2 As described, the penetration point may be calculated based on the location of the UE or a nearby entity (e.g., a base station) communicating with the UE and the location of the GNSS satellite that transmits the GNSS signal. The penetration point may be determined by the UE, for example, based on knowledge of the UE's own approximate location and the locations of the GNSS satellites. Alternatively, the penetration point may be calculated by a remote or network entity (e.g., a base station or server of an augmentation system) and communicated from the remote / network entity to the UE.

[0071] At 508, the ionospheric error in the positioning measurement of the GNSS signal is determined based on the penetration point obtained in box 506 and the amplification data obtained in box 504. For example, the determination in box 508 may involve identifying the TEC value of the penetration point, or more specifically, identifying the TEC value of a set of grid points around the penetration point. For example, if the amplification data is stored in the form of a lookup table, the longitude and latitude coordinates of the four grid points corresponding to the corners of the grid cell around the penetration point (e.g., a square or rectangular box spanning a certain number of latitudes and longitudes) can be used to find the TEC value at each of those coordinates. The identified TEC value can be a value for a previous measurement cycle, which can be any measurement cycle before the current measurement cycle, or generally, any measurement cycle covered by amplification data older than the non-historical amplification data that should be available. For example, the historical TEC value can be a TEC value from yesterday, the day before yesterday, last week, etc.

[0072] As part of the functionality in block 508, a trend may be calculated for each of the four grid points surrounding the breakthrough point, for example, using historical values ​​at the four grid points to estimate a TEC value applicable to the breakthrough point in the current measurement cycle. These estimated TECs at the grid points may then be used to extrapolate TEC values ​​applicable to the same breakthrough point but at the current time. For example, a separate TEC value may be extrapolated for each of the four grid points (using any of the extrapolation methods described above), and the TEC value may be calculated for the breakthrough point as an average or weighted average of the four extrapolated values. In some cases, fewer than four grid points may be used to extrapolate the TEC value for the breakthrough point. For example, when the coordinates of the breakthrough point exactly match the coordinates of the grid point, a single grid point may be sufficient to determine the TEC value for the breakthrough point.

[0073] Using the TEC value for the penetration point, the ionospheric delay (and therefore the ionospheric error) may be determined. For example, the ionospheric delay may be calculated as the product of the TEC value for the penetration point and a scaling factor according to the carrier frequency of the GNSS signal. Alternatively, as described above, the ionospheric delay may be determined by inputting the penetration point and the current time into a computer model that has been generated using historical augmentation data, such that the ionospheric error is determined without directly using historical TEC values.

[0074] At 510, the ionospheric error in the positioning measurement of the GNSS signal is optionally corrected using the ionospheric error determined in block 508. The correction may involve adjusting the positioning measurement value in consideration of the ionospheric error. Thus, the UE may correct the ionospheric error even though the UE may not have received one or more TEC values ​​associated with the current measurement period. For example, the adjustment of the positioning measurement value may be performed by the UE itself before the corrected positioning measurement is sent to a location server that uses the corrected positioning measurement to calculate the position of the UE. Alternatively, the correction in 510 may involve transmitting the positioning measurement together with the TEC value identified in 508 and / or the TEC value extrapolated using the TEC value in 508 to a location server or other remote / network entity to enable the remote / network entity to calculate and apply the correction value.

[0075] Figure 6 is a flow chart of a method 600 for compressing amplification data, for example, for use as historical amplification data, according to an embodiment. Figure 6 The illustrated functional means may be performed by hardware and / or software components of a mobile device equipped with a GNSS receiver (e.g., one or more processors of a UE). Fig.11 It is shown in FIG. 1 and will be described in more detail below.

[0076] At 602, augmentation data is received from an augmentation system. The augmentation data received in block 602 includes TEC values ​​during one or more periods (e.g., TEC values ​​for a geographic region in which the UE is currently located and covering a current measurement period). For example, the augmentation data in 602 may include a set of TEC values ​​for different points in a grid representing an ionosphere over the one or more geographic regions, wherein the grid values ​​are generated according to a model of the ionosphere (e.g., an SBAS model) and transmitted via satellites of the augmentation system (e.g., Figure 3 The augmentation data in 602 may be transmitted from a satellite 315 in the amplification system and is expected to be valid for a certain duration covering the current measurement period (indicative of actual ionospheric delay). In some cases, the augmentation data in 602 may be received from a ground-based component of the augmentation system (e.g., a server or base station). The augmentation data may be received as part of a periodic broadcast of such data.

[0077] At 604, the degree (n) and order (m) of the spherical harmonics are determined for the grid. As noted above, the grid represents a snapshot of the ionosphere at a particular point in time. Multiple grids may be used to cover multiple time periods, geographic regions, and / or broadcasts from different augmentation systems. When compressing the grid, the degree n and order m may be determined separately for each snapshot to optimally represent the data. In some implementations, the TEC values ​​from the snapshots may be further divided into geographic regions to achieve higher compression in regions where the ionospheric activity is low (TEC variation across grid points is low) and to achieve higher accuracy in regions where the ionospheric activity is high (TEC variation between grid points is high). The general form of the spherical harmonics is:

[0078]

[0079] where θ is the co-latitude and has values ​​from 0 to π, is the longitude and has values ​​from 0 to 2π, and are the coefficients whose values ​​are to be determined and which determine the shape of the spherical function, and is the Legendre function (a function represented by an associated Legendre polynomial). The coefficients and The coefficients may be determined by the augmentation system and communicated to the UE. Alternatively, these coefficients may be determined by the UE based on grid values ​​received from the augmentation system (e.g., the augmentation data received in 602). Here, the function The value of is the TEC value. Therefore, the longitude and latitude coordinates of the penetration point can be used as a function The input is provided to determine the TEC value at the penetration point. In some implementations, the TEC value for each possible penetration point in one or more geographic areas is pre-calculated and stored in a memory, such as in a lookup table. Alternatively, the UE may be configured to use the coordinates of the penetration point as a function TEC value is calculated instantly based on the input.

[0080] The general form in equation 1 above can be expressed in terms of the degree n and order m of the spherical harmonics as follows:

[0081]

[0082] where min(n,m) is a function that determines the lowest value among several inputs (in this case, the smaller of n and m).

[0083] The order m is usually lower than the degree n, in which case Equation 2 can be expanded to Figure 7 The expression shown. In addition, Figure 7 The expression in simplifies to the product between two vectors:

[0084]

[0085] where X is the coefficient vector containing the coefficients whose values ​​are to be estimated, and C is the scale vector.

[0086] Figure 8 The general form of the coefficient vector X is shown. Fig. 9 The general form of the scale vector C is shown in Figure 8 As shown, the coefficient vector X includes a set of coefficients whose values ​​are independent of latitude and longitude. Fig. 9 As shown, the scale vector C includes a set of coefficients whose values ​​are functions of latitude and longitude. Therefore, in some embodiments, the vector product form of the spherical harmonic function in Equation 3 can be communicated to the UE by the augmentation system, for example, as a set of coefficients representing the coefficient vector X and a set of coefficients representing the scale vector C. Alternatively, the UE can select the parameters n and m, for example, in combination with performing Figure 6 The functionality in box 604 is used to generate the vector product form of the spherical harmonics.

[0087] Back to Figure 6 In block 604, as discussed above, the degree n and / or order m may be determined based on the change in TEC values ​​at each geographic region. Thus, n or m may be different between a first geographic region and a second geographic region. In practice, this results in spherical harmonic coefficients being region-specific. This technique of providing completely different processing for different regions may be applied to achieve different compression levels for TEC values ​​in different locations. Furthermore, the degree and / or order of the spherical harmonic functions representing a given geographic region may change over time in order to achieve different compression levels corresponding to changes in ionospheric activity at the region over time. Thus, the degree and / or order used to generate a compressed snapshot for a set of grid values ​​may be different from the degree and / or order used to compress another set of grid values ​​received later.

[0088] from Figure 8 and Fig. 9It can be seen that the size of vectors X and C depends on the values ​​of n and m. As n or m increases, the vector size also increases. Conversely, the vector size decreases as n or m decreases. For example, for n=12 and m=10, the size of each vector is 163 data elements. For n=16 and m=12, the size is 269 elements. By selecting n and m based on the change in the TEC level of the geographic region, a compression level suitable for accurate representation of the TEC value can be achieved. For example, during or in a relatively active time period or position of the ionosphere, the difference between the TEC values ​​at adjacent or neighboring grid points (e.g., any pair of grid points belonging to the same unit) tends to be higher, while when the ionosphere is quiet, the TEC values ​​of adjacent / adjacent grid points tend to be more uniform. Therefore, when there are large fluctuations in the TEC values ​​across grid points (or generally, geographic regions), a higher degree and / or order can be selected to more accurately capture the impact of the ionosphere. When larger n values ​​and / or m values ​​are selected, this produces less compression but more accurate representations, and therefore produces more accurate calculations of ionospheric delays. Similarly, smaller values ​​of n and / or m may be selected during times or geographic regions where the ionosphere is relatively quiet (e.g., the maximum difference in TEC values ​​across grid points or the average difference in TEC values ​​across grid points is below a certain threshold), thereby producing a more compressed but less accurate representation. With appropriate selections of n and m, the accuracy of the estimated UE's position will be relatively unaffected because the effects of ionospheric delays are smaller when the ionosphere is relatively quiet.

[0089] At 606, one or more vectors containing coefficients of spherical harmonics are generated. For example, the vector generated in 606 may be the coefficient vector X or the scale vector C described above. In some implementations, both vector X and vector C are generated by the amplification system and communicated to the UE for use as historical data. Alternatively, the amplification system may send vector X to the UE without sending vector C, and the UE may determine the value of vector C for itself, because the UE may be configured with information about the associated Legendre polynomials from which the value of vector C is derived. In such implementations, the functionality in box 604 may be performed by the amplification system rather than the UE. As yet another option, the UE may generate both vector X and vector C for its own use, for example, based on the TEC value received in 602. That is, instead of relying on the amplification system to deliver compressed amplification data, the UE may generate a compressed form of the amplification data it receives, and store the compressed amplification data for later use as historical data.

[0090] In addition, in some implementations, compressing amplification data may involve using a mixed data type to represent a compressed form of amplification data. Using different data types is another way to achieve different compression levels. For example, a higher precision data type may be used to represent the values ​​of coefficients in vector X and / or vector C to obtain a more accurate representation of ionospheric TEC values ​​for certain regions or time periods. A lower precision data type may be used to represent the values ​​of coefficients in vector X and / or vector C to achieve more compression when representing ionospheric TEC values ​​for certain regions and / or time periods. The selection of data types may also depend on the degree and order selected for spherical harmonics. As discussed above, when the ionosphere is relatively active, a higher degree and / or order may be used to reduce compression. Generally speaking, the size of the coefficient becomes smaller as the degree or order of the spherical harmonics increases, and in such cases, a less precise data type may be sufficient to represent a higher order coefficient. However, for any given combination of degree n and order m, the size of the coefficient will typically vary significantly, so a mixed data type may be useful for representing the coefficient, regardless of the degree and order selected. Thus, the compressed form of the augmentation data received in block 602 may include, for example, a mix of 16-bit unsigned integers and 64-bit double precision floating points.

[0091] At 608, one or more vectors from 606 are stored as compressed representations of the amplification data received in 602. The one or more vectors may be stored in a memory of the UE and retrieved for later use as part of an ionospheric error in a positioning measurement for correcting a GNSS signal. For example, as described above, when a TEC value for the current measurement cycle is unavailable, historical TEC values ​​from previous measurement cycles may be used to extrapolate TEC values ​​for the current measurement cycle. It should be noted that although the amplification data is compressed, it is not necessarily necessary to decompress it for use in correcting positioning measurements. Instead, as described above, TEC values ​​may be determined based on a simple lookup operation or by inputting the longitude and latitude coordinates of the relevant penetration point into a spherical harmonic function represented by one or more vectors. Therefore, the UE or other device performing the correction does not need to regenerate all values ​​received for the amplification data in 602.

[0092] Fig. 10A is a graphical representation of exemplary TEC values ​​for geographic regions. The horizontal axis represents longitude. The vertical axis represents latitude. Darker areas represent locations with lower TEC values, while lighter areas represent locations with higher TEC values, where TEC values ​​range from 0 TECU to 50 TECU. Fig. 10A The TEC values ​​in are obtained from the IGS GIM grid and therefore cover the entire Earth. The TEC values ​​from the IGS GIM grid are represented as unsigned integers with a total data size of 10,366 bytes.

[0093] Fig. 10B Is compression from Fig. 10A A graphical representation of exemplary results for the TEC values. The compression was produced using spherical harmonics of degree 16 and order 12 and double precision floating point, with a total data size of 2,152 bytes. Fig. 10A and Fig. 10B , it can be seen that Fig. 10B The compressed representation in is Fig. 10A is a reasonable approximation of the uncompressed representation of . Numerically, Fig. 10A and Fig. 10B The difference between TECU values ​​of corresponding points in the data is usually 1.5 TECU or less. In addition, based on the total data size, a compression ratio of about 21% is achieved despite the use of higher precision data types for compression.

[0094] Fig.11 1 shows an embodiment of a UE 1102 that can be utilized as described above. For example, the UE 1102 can execute Figure 5 or Figure 6 The UE 1102 may also implement one or more of the above-mentioned UEs (e.g., Figure 1 UE 105 or Figure 3 320 in FIG. 1 ). It should be noted that Fig.11 It is intended only to provide a generalized illustration of the various components, any or all of which may be utilized as appropriate. It may be noted that in some cases, Fig.11 The illustrated components may be located in a single physical device and / or distributed among various networked devices that may be located at different physical locations. In addition, as previously mentioned, the functionality of the UE discussed in the previously described embodiments may be provided by Fig.11 The invention may be executed by one or more of the hardware and / or software components illustrated in the specification.

[0095] UE 1102 is shown as including hardware elements that may be electrically coupled via bus 1105 (or may communicate in other ways as appropriate). The hardware elements may include a processing unit 1110, which may include, but is not limited to, one or more general-purpose processors, one or more special-purpose processors (such as digital signal processor (DSP) chips, graphics acceleration processors, application-specific integrated circuits (ASICs), etc.), and / or other processing structures or devices. Fig.11As shown, some embodiments may have a separate DSP 1120, depending on the desired functionality. Position determination and / or other determinations based on wireless communication may be provided in the processing unit 1110 and / or the wireless communication interface 1130 (discussed below). The UE 1102 may also include one or more input devices 1170, which may include but are not limited to one or more keyboards, touch screens, touch pads, microphones, buttons, dials, switches, etc.; and one or more output devices 1115, which may include but are not limited to one or more displays (e.g., touch screens), light emitting diodes (LEDs), speakers, etc.

[0096] UE 1102 may also include a wireless communication interface 1130 (eg, corresponding to Figure 3 The wireless communication subsystem 322 in the wireless communication interface may include but is not limited to a modem, a network card, an infrared communication device, a wireless communication device and / or a chipset (such as Device, IEEE 802.11 device, IEEE 802.15.4 device, Wi-Fi device, WiMAX device, WAN device and / or various cellular devices, etc.), etc., which can enable UE 1102 to communicate with other devices as described in the above embodiments. The wireless communication interface 1130 can allow communication (e.g., transmission and reception) of data and signaling with a network (e.g., via an access point, various base stations and / or other access node types, and / or other network components, computer systems, and / or other electronic devices described herein). Communication can be performed via one or more wireless communication antennas 1132 that send and / or receive wireless signals 1134. According to some embodiments, the wireless communication antenna 1132 may include multiple discrete antennas, antenna arrays, or any combination thereof.

[0097] Depending on the desired functionality, the wireless communication interface 1130 may include a separate receiver and transmitter, or any combination of transceivers, transmitters and / or receivers to communicate with base stations and other ground transceivers (such as wireless devices and access points). UE 1102 can communicate with different data networks that may include various network types. For example, a wireless wide area network (WWAN) may be a CDMA network, a time division multiple access (TDMA) network, a frequency division multiple access (FDMA) network, an orthogonal frequency division multiple access (OFDMA) network, a single carrier frequency division multiple access (SC-FDMA) network, a WiMAX (IEEE 802.16) network, and the like. A CDMA network may implement one or more RATs, such as CDMA2000, WCDMA, and the like. CDMA2000 includes IS-95, IS-2000, and / or IS-856 standards. A TDMA network may implement GSM, a digital advanced mobile phone system (D-AMPS), or some other RAT. An OFDMA network may use LTE, advanced LTE, 5G NR, and the like. 5G NR, LTE, Advanced LTE, GSM, and WCDMA are described in documents from the Third Generation Partnership Project (3GPP). CDMA2000 is described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). 3GPP and 3GPP2 documents are publicly available. A wireless local area network (WLAN) may also be an IEEE 802.11x network, while a wireless personal area network (WPAN) may be a Bluetooth network, IEEE 802.15x, or some other type of network. The techniques described herein may also be used for any combination of WWAN, WLAN, and / or WPAN.

[0098] UE 1102 may also include sensors 1140. Sensors 1140 may include, but are not limited to, one or more inertial sensors and / or other sensors (e.g., accelerometers, gyroscopes, cameras, magnetometers, altimeters, microphones, proximity sensors, light sensors, barometers, etc.), some of which may be used to obtain location-related measurements and / or other information.

[0099] Embodiments of UE 1102 may also include a global navigation satellite system (GNSS) receiver 1180 that is capable of receiving signals 1184 from one or more GNSS satellites using an antenna 1182 (which may be the same as antenna 1132). Positioning based on GNSS signal measurements may be used to supplement and / or incorporate the techniques described herein. GNSS receiver 1180 may extract the location of UE 1102 from GNSS satellites of GNSS systems such as the Global Positioning System (GPS), Galileo, GLONASS, Japan's Quasi-Zenith Satellite System (QZSS), India's Indian Regional Navigation Satellite System (IRNSS), China's BeiDou Navigation Satellite System (BDS), etc. using conventional techniques. In addition, the GNSS receiver 1180 may be used for various augmentation systems (e.g., satellite-based augmentation systems (SBAS)) that may be associated with or otherwise enabled for use with one or more global and / or regional navigation satellite systems, such as, for example, the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), the Multipurpose Satellite Augmentation System (MSAS), and the Geographic Augmented Navigation System (GAGAN), etc. In some embodiments, the UE 1102 may include a separate wireless receiver capable of receiving signals from one or more satellites of the augmentation system.

[0100] Note that although Fig.11 1180 is shown as a different component, but the embodiments are not limited thereto. As used herein, the term "GNSS receiver" may include hardware and / or software components configured to obtain GNSS measurements (measurements from GNSS satellites). Therefore, in some embodiments, the GNSS receiver may include a measurement engine executed by one or more processing units such as processing unit 1110, DSP 1120, and / or a processing unit (as software) within the wireless communication interface 1130 (e.g., in a modem). The GNSS receiver may also optionally include a positioning engine that can use the GNSS measurements from the measurement engine to determine the position of the GNSS receiver using an extended Kalman filter (EKF), a weighted least squares method (WLS), a hatch filter, a particle filter, etc. The positioning engine may also be executed by one or more processing units such as processing unit 1110 or DSP 1120.

[0101] UE 1102 may also include and / or communicate with memory 1160. Memory 1160 may include, but is not limited to, local and / or network accessible storage devices, disk drives, drive arrays, optical storage devices, solid-state storage devices (such as random access memory (RAM) and / or read-only memory (ROM)) that may be programmable, flash-updatable, etc. Such storage devices may be configured to implement any suitable data storage, including but not limited to various file systems, database structures, etc.

[0102] The memory 1160 of the UE 1102 may also include software elements ( Fig.11 1102 (and / or the processing unit 1110 or DSP 1120 within the UE 1102). In one aspect, such code and / or instructions may then be used to configure and / or adapt a general purpose computer (or other device) to perform one or more operations according to the described methods.

[0103] It will be apparent to those skilled in the art that substantial variations may be made depending on specific requirements. For example, customized hardware may also be used, and / or specific elements may be implemented in hardware, software (including portable software, such as applets, etc.), or both. In addition, connections to other computing devices such as network input / output devices may be employed.

[0104] With reference to the accompanying drawings, a component that may include a memory may include a non-transitory machine-readable medium. As used herein, the terms "machine-readable medium" and "computer-readable medium" refer to any storage medium that participates in providing data that enables a machine to operate in a particular manner. In the embodiments provided above, various machine-readable media may involve providing instructions / codes to a processing unit and / or other devices for execution. Additionally or alternatively, a machine-readable medium may be used to store and / or carry such instructions / codes. In many implementations, a computer-readable medium is a physical and / or tangible storage medium. Such media may take a variety of forms, including but not limited to non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example: magnetic and / or optical media, any other physical media with a hole pattern, RAM, programmable ROM (PROM), erasable PROM (EPROM), flash EPROM, any other memory chip or memory box, carrier described below, or any other medium from which a computer can read instructions and / or codes.

[0105] The methods, systems and devices discussed herein are examples. Various embodiments may appropriately omit, replace or add various processes or components. For example, features described with reference to certain embodiments may be combined in various other embodiments. Different aspects and elements of the embodiments may be combined in a similar manner. The various components of the accompanying drawings provided herein may be embodied in hardware and / or software. Moreover, technology may evolve, and therefore many elements are examples, which do not limit the scope of the present disclosure to those specific examples.

[0106] It has proven convenient at times, primarily for reasons of common usage, to refer to such signals as bits, information, values, elements, symbols, characters, variables, terms, numbers, digital symbols, and the like. It will be understood, however, that all of these or similar terms are to be associated with the appropriate physical quantities and are merely convenient labels. Unless specifically stated otherwise, as will be apparent from the above discussion, it will be understood that throughout this specification, discussions utilizing terms such as "processing," "computing," "calculating," "determining," "ascertaining," "identifying," "correlating," "measuring," "performing," and the like refer to the actions or processes of a specific apparatus, such as a special purpose computer or similar special purpose electronic computing device. Thus, in the context of this specification, a special purpose computer or similar special purpose electronic computing device is capable of manipulating or transforming signals, typically expressed as physical, electronic, electrical, or magnetic quantities in a memory, register, or other information storage device, transmission device, or display device of the special purpose computer or similar special purpose electronic computing device.

[0107] As used herein, the terms "and" and "or" may include various meanings that are also intended to depend at least in part on the context in which such terms are used. Generally, "or", if used in an associative list, such as A, B, or C, is intended to mean A, B, and C (inclusive meanings are used here) as well as A, B, or C (exclusive meanings are used here). In addition, the term "one or more" used herein may be used to describe any feature, structure, or characteristic in the singular, or may be used to describe a certain combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example, and the subject matter claimed is not limited to this example. In addition, the term "at least one of", if used in an associative list, such as A, B, or C, may be interpreted to mean any combination of A, B, and / or C, such as A, AB, AA, AAB, AABBCCC, etc.

[0108] Several embodiments have been described, and various modifications, alternative configurations, and equivalents may be used without departing from the spirit of the present disclosure. For example, the above elements may be components of a larger system, where other rules may take precedence over the application of the various embodiments or otherwise modify the application of the various embodiments. In addition, several steps may be taken before, during, or after considering the above elements. Accordingly, the above description does not limit the scope of the present disclosure.

[0109] In view of this description, various embodiments may include different combinations of features. Various implementation examples are described in the following numbered clauses:

[0110] Clause 1. A method performed at a mobile device for determining ionospheric error, the method comprising: determining a positioning measurement of a global navigation satellite system (GNSS) signal; obtaining amplification data associated with a total electron content (TEC) value during one or more previous measurement cycles; obtaining a penetration point of the GNSS signal; and determining an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0111] Clause 2. The method of clause 1, wherein the amplification data comprises one or more TEC values ​​during a previous day.

[0112] Clause 3. The method of clause 2, wherein the amplified data comprises a TEC value at the penetration point during a specific time in the previous day, the specific time being later than the time when the GNSS signal is received.

[0113] Clause 4. The method of any one of clauses 1 to 3, wherein obtaining the amplification data is performed in response to determining that one or more TEC values ​​during a current measurement cycle are not available.

[0114] Clause 5. The method according to any one of clauses 1 to 4, further comprising: using the augmented data to extrapolate a first TEC value for a current measurement period; and determining the ionospheric error in the positioning measurement based on the first TEC value.

[0115] Clause 6. The method of Clause 5, wherein extrapolating the first TEC value uses a second TEC value included in the amplification data in combination with at least one TEC value received for the current measurement cycle.

[0116] Clause 7. A method according to any one of clauses 1 to 6, wherein extrapolating the first TEC value includes determining the first TEC value as a weighted sum of a second TEC value included in the amplification data plus one or more additional TEC values, the one or more additional TEC values ​​including a third TEC value received for the current measurement cycle, a fourth TEC value included in the amplification data, or both.

[0117] Clause 8. The method according to any one of clauses 1 to 4 further comprises: determining the ionospheric error in the positioning measurement using a TEC value included in the amplified data as a substitute for a TEC value that should have been included in the amplified data for the current measurement cycle and that is unavailable.

[0118] Clause 9. The method according to any one of clauses 1 to 8, further comprising: receiving, by the mobile device, the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, wherein the compressed representation includes coefficients of spherical harmonics.

[0119] Clause 10. The method according to any one of clauses 1 to 8 further includes: generating, by the mobile device, the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, wherein generating the compressed representation includes determining coefficients of spherical harmonics.

[0120] Clause 11. The method of clause 10, wherein generating the compressed representation further comprises: determining the degree n and the order m of the spherical harmonics based on differences between TEC values ​​at different grid points.

[0121] Clause 12. A method according to clause 11, wherein determining the order n and the order m comprises selecting a larger order n or order m when the difference between the TEC values ​​at the different grid points indicates a higher amount of ionospheric activity than when the difference between the TEC values ​​at the different grid points indicates a lower amount of ionospheric activity.

[0122] Clause 13. The method of any one of clauses 10 to 12, wherein generating the compressed representation further comprises: representing the value of the coefficient using a combination of a higher precision data type and a lower precision data type.

[0123] Clause 14. A mobile device comprising: a global navigation satellite system (GNSS) receiver configured to receive GNSS signals from a navigation satellite; a wireless communication interface configured to communicate with an augmentation system; a memory; and one or more processing units communicatively coupled to the GNSS receiver, the wireless communication interface, and the memory, the one or more processing units configured to:

[0124] Determining a positioning measurement of the GNSS signal; obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles; obtaining a penetration point of the GNSS signal; and determining an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0125] Clause 15. The mobile device of clause 14, wherein the augmented data comprises one or more TEC values ​​during a previous day.

[0126] Clause 16. The mobile device of clause 15, wherein the augmented data comprises a TEC value at the penetration point during a specific time in the previous day, the specific time being later than a time when the GNSS signal is received by the GNSS receiver.

[0127] Clause 17. The mobile device of any of Clauses 14 to 16, wherein the one or more processing units are configured to obtain the amplification data in response to determining that one or more TEC values ​​during a current measurement cycle are not available.

[0128] Clause 18. A mobile device according to any one of clauses 14 to 17, wherein the one or more processing units are further configured to: use the amplified data to extrapolate a first TEC value for a current measurement period; and determine the ionospheric error in the positioning measurement based on the first TEC value.

[0129] Clause 19. The mobile device of Clause 18, wherein to extrapolate the first TEC value, the one or more processing units are configured to use a second TEC value included in the amplification data in combination with at least one TEC value received for the current measurement cycle.

[0130] Clause 20. A mobile device according to any one of clauses 14 to 19, wherein to extrapolate the first TEC value, the one or more processing units are configured to determine the first TEC value as a weighted sum of a second TEC value included in the amplification data plus one or more additional TEC values, the one or more additional TEC values ​​including a third TEC value received for the current measurement cycle, a fourth TEC value included in the amplification data, or both.

[0131] Clause 21. A mobile device according to any one of clauses 14 to 17, wherein the one or more processing units are configured to determine the ionospheric error in the positioning measurement using a TEC value included in the amplification data as a substitute for a TEC value that should have been included in the amplification data for the current measurement cycle when the amplification data for the current measurement cycle is not available.

[0132] Clause 22. A mobile device according to any one of clauses 14 to 21, wherein the mobile device is configured to receive the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and wherein the compressed representation includes coefficients of spherical harmonics.

[0133] Clause 23. A mobile device according to any one of clauses 14 to 21, wherein the one or more processing units are configured to generate the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and wherein in order to generate the compressed representation, the one or more processing units are configured to determine coefficients of spherical harmonics.

[0134] Clause 24. The mobile device of clause 23, wherein to generate the compressed representation, the one or more processing units are configured to determine the degree n and the order m of the spherical harmonics based on differences between TEC values ​​at different grid points.

[0135] Clause 25. A mobile device according to clause 24, wherein in order to determine the order n and the order m, the one or more processing units are configured to select a larger order n or order m when the difference between the TEC values ​​at the different grid points indicates a higher amount of ionospheric activity than when the difference between the TEC values ​​at the different grid points indicates a lower amount of ionospheric activity.

[0136] Clause 26. A mobile device according to any of clauses 23 to 25, wherein to generate the compressed representation, the one or more processing units are configured to represent the value of the coefficient using a combination of a higher precision data type and a lower precision data type.

[0137] Clause 27. A non-transitory computer-readable medium having instructions stored thereon, wherein the instructions, when executed by one or more processing units of a mobile device, cause the one or more processing units to perform the following operations: determine a positioning measurement of a global navigation satellite system (GNSS) signal; obtain amplification data associated with a total electron content (TEC) value during one or more previous measurement cycles; obtain a penetration point of the GNSS signal; and

[0138] An ionospheric error in the positioning measurement of the GNSS signal is determined based on the penetration point and the augmentation data.

[0139] Clause 28. The non-transitory computer-readable medium of Clause 27, wherein the amplification data comprises one or more TEC values ​​during a previous day.

[0140] Clause 29. A non-transitory computer-readable medium according to clause 27 or 28, wherein the instructions further cause the one or more processing units to generate the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and determine coefficients of spherical harmonics as part of generating the compressed representation.

[0141] Clause 30. A system comprising: a global navigation satellite system (GNSS) receiver configured to receive GNSS signals from navigation satellites; a wireless communication interface configured to communicate with an amplification system; one or more processing units configured to determine a positioning measurement of the GNSS signal; a device for obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles; a device for obtaining a penetration point of the GNSS signal; and a device for determining an ionospheric error in the positioning measurement of the GNSS signal based on the penetration point and the amplification data.

[0142] Clause 31. The system of clause 30 further comprises: a device for generating the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, wherein the device for generating the amplification data is configured to determine coefficients of spherical harmonics as part of generating the compressed representation.

Claims

1. A method performed at a mobile device for determining an ionospheric error, the method comprising: determining, by one or more processing units of the mobile device, positioning measurements using a Global Navigation Satellite System (GNSS) signal received by a GNSS receiver of the mobile device; obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles from an amplification system in wireless communication with the mobile device or from a memory of the mobile device, wherein obtaining the amplification data is performed in response to determining that the mobile device is unable to obtain newer amplification data currently stored at the amplification system; obtaining, by the mobile device, a penetration point of the GNSS signal, wherein obtaining the penetration point comprises calculating the penetration point using the one or more processing units or receiving the penetration point from a remote entity; as well as An ionospheric error in the positioning measurement of the GNSS signal is determined by the one or more processing units based on the penetration points and the augmentation data.

2. The method of claim 1, wherein the amplification data comprises one or more TEC values ​​during the previous day. 3 . The method of claim 2 , wherein the amplified data comprises a TEC value at the penetration point during a specific time in the previous day, the specific time being later than a time when the GNSS signal is received.

4. The method according to claim 1, further comprising: using the amplification data to extrapolate a first TEC value for a current measurement cycle; as well as The ionospheric error in the positioning measurement is determined based on the first TEC value. 5 . The method of claim 4 , wherein extrapolating the first TEC value uses a second TEC value included in the amplification data in combination with at least one TEC value received for the current measurement cycle.

6. The method of claim 4, wherein extrapolating the first TEC value comprises determining the first TEC value as a weighted sum of a second TEC value included in the amplification data plus one or more additional TEC values, the one or more additional TEC values ​​comprising a third TEC value received for the current measurement cycle, a fourth TEC value included in the amplification data, or both.

7. The method according to claim 1, further comprising: The ionospheric error in the positioning measurement is determined using the TEC value included in the augmentation data as a substitute for the TEC value that would have been included in the more recent augmentation data.

8. The method according to claim 1, further comprising: The amplification data is received by the mobile device as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, wherein the compressed representation includes coefficients of spherical harmonics.

9. The method according to claim 1, further comprising: The amplification data is generated, by the mobile device, as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, wherein generating the compressed representation includes determining coefficients of spherical harmonics.

10. The method of claim 9, wherein generating the compressed representation further comprises: The degree n and order m of the spherical harmonics are determined based on the difference between the TEC values ​​at different grid points.

11. The method of claim 10, wherein determining the degree n and the order m comprises: A larger degree n or order m is selected when the difference between the TEC values ​​at the different grid points indicates a higher amount of ionospheric activity than when the difference between the TEC values ​​at the different grid points indicates a lower amount of ionospheric activity.

12. The method of claim 9, wherein generating the compressed representation further comprises: A combination of higher precision data types and lower precision data types are used to represent the values ​​of the coefficients.

13. A mobile device, comprising: a global navigation satellite system (GNSS) receiver configured to receive GNSS signals from a navigation satellite; a wireless communication interface configured to communicate with an amplification system; Memory; and one or more processing units communicatively coupled to the GNSS receiver, the wireless communication interface, and the memory, the one or more processing units configured to: determining a positioning measurement of the GNSS signal; obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles, wherein the one or more processing units are configured to obtain the amplification data in response to determining that the mobile device is unable to obtain newer amplification data currently stored at the amplification system; Obtaining a penetration point of the GNSS signal; and An ionospheric error in the positioning measurement of the GNSS signal is determined based on the penetration point and the augmentation data.

14. The mobile device of claim 13, wherein the amplification data comprises one or more TEC values ​​during a previous day. 15 . The mobile device of claim 14 , wherein the amplification data comprises a TEC value at the penetration point during a specific time in the previous day, the specific time being later than a time when the GNSS signal was received by the GNSS receiver.

16. The mobile device of claim 13, wherein the one or more processing units are further configured to: using the amplification data to extrapolate a first TEC value for a current measurement cycle; and The ionospheric error in the positioning measurement is determined based on the first TEC value. 17 . The mobile device of claim 16 , wherein to extrapolate the first TEC value, the one or more processing units are configured to use a second TEC value included in the amplification data in combination with at least one TEC value received for the current measurement cycle.

18. The mobile device of claim 16, wherein to extrapolate the first TEC value, the one or more processing units are configured to determine the first TEC value as a weighted sum of a second TEC value included in the amplification data plus one or more additional TEC values, the one or more additional TEC values ​​comprising a third TEC value received for the current measurement cycle, a fourth TEC value included in the amplification data, or both.

19. The mobile device of claim 13, wherein the one or more processing units are configured to determine the ionospheric error in the positioning measurement using a TEC value included in the augmentation data as a substitute for a TEC value that should have been included in the more recent augmentation data.

20. The mobile device of claim 13, wherein the mobile device is configured to receive the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and wherein the compressed representation includes coefficients of spherical harmonics.

21. The mobile device of claim 13, wherein the one or more processing units are configured to generate the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and wherein to generate the compressed representation, the one or more processing units are configured to determine coefficients of spherical harmonics.

22. The mobile device of claim 21, wherein to generate the compressed representation, the one or more processing units are configured to determine the degree n and the order m of the spherical harmonics based on differences between TEC values ​​at different grid points.

23. The mobile device of claim 22, wherein to determine the order n and the magnitude m, the one or more processing units are configured to select a larger order n or magnitude m when the difference between the TEC values ​​at the different grid points indicates a higher amount of ionospheric activity than when the difference between the TEC values ​​at the different grid points indicates a lower amount of ionospheric activity.

24. The mobile device of claim 21, wherein to generate the compressed representation, the one or more processing units are configured to represent the values ​​of the coefficients using a combination of a higher precision data type and a lower precision data type.

25. A non-transitory computer-readable medium having stored thereon instructions, wherein the instructions, when executed by one or more processing units of a mobile device, cause the one or more processing units to: Determine positioning measurements from Global Navigation Satellite System (GNSS) signals; obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles from an amplification system in wireless communication with the mobile device or from a memory of the mobile device, wherein obtaining the amplification data is performed in response to determining that the mobile device is unable to obtain newer amplification data currently stored at the amplification system; Obtaining a penetration point of the GNSS signal; and An ionospheric error in the positioning measurement of the GNSS signal is determined based on the penetration point and the augmentation data.

26. The non-transitory computer readable medium of claim 25, wherein the amplification data comprises one or more TEC values ​​during a previous day.

27. The non-transitory computer readable medium of claim 25, wherein the instructions further cause the one or more processing units to generate the amplification data as a compressed representation of a grid containing the TEC values ​​during the one or more previous measurement cycles, and to determine coefficients of spherical harmonics as part of generating the compressed representation.

28. A computer system comprising: a global navigation satellite system (GNSS) receiver configured to receive GNSS signals from a navigation satellite; a wireless communication interface configured to communicate with an amplification system; one or more processing units configured to determine positioning measurements of the GNSS signals; means for obtaining amplification data associated with total electron content (TEC) values ​​during one or more previous measurement cycles, wherein the amplification data is obtained in response to determining that newer amplification data currently stored at the amplification system is unavailable to the computer system; means for obtaining a penetration point of said GNSS signal; as well as Means for determining ionospheric errors in the positioning measurements of the GNSS signals based on the penetration points and the augmentation data.

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