JP5697391B2 - Satellite positioning system and positioning signal receiver - Google Patents

Description

  The present invention relates to a position determination technique based on a positioning signal transmitted from a satellite positioning system typified by a global positioning system (GPS), and more specifically, from starting a positioning signal receiver to determining a position. The present invention relates to a technique for shortening time.

  Conventionally, in positioning using a satellite positioning system, radio waves transmitted from positioning satellites are received by a ground receiver, and the distance between the satellite and the receiver is measured based on the radio wave propagation time from the satellite to the receiver. To do.

  On the radio wave transmitted from the positioning satellite, orbit information indicating the position of the positioning satellite itself called ephemeris and clock information indicating a time lag of the satellite itself are superimposed as navigation data. The navigation data includes rough values for all satellites called almanac. These are transmitted at 50 bps and require at least 30 seconds to demodulate the trajectory and clock from the ephemeris.

  On the other hand, there is a quasi-zenith satellite system (QZSS) as a satellite positioning system developed in Japan. QZSS has a reinforcing signal called a L1-SAIF signal of 250 bps in addition to the above-described positioning signal of 50 bps. The specification of the L1-SAIF signal is defined in IS-QZSS (Non-Patent Document 1), and the format conforms to the SBAS system. In L1-SAIF and SBAS, information for mainly improving the positioning accuracy is transmitted.

  Since the ephemeris is necessary for the position determination by the receiver in the satellite positioning system, the time from the start of operation of the receiver until the first position determination, that is, the initial position calculation time (TTFF: Time To First) Fix) requires at least 30 seconds which is the transmission time of the ephemeris. Since TTFF is directly linked to the convenience of the user, it is potentially required to be shortened.

  As an example of a technique for shortening such TTFF, a satellite position and a satellite clock calculated based on the ephemeris and the almanac are obtained for a receiver holding a reference almanac as shown in Patent Document 1. There is a method in which the receiver can perform positioning without using the ephemeris by transmitting the difference information (hereinafter referred to as “difference method”).

  And about the implementation of the technique shown in patent document 1, the examination at the time of using the message format of SBAS or L1-SAIF is performed (nonpatent literature 2).

  According to the study in Non-Patent Document 2, by using the bit allocation disclosed in the same document, it is possible to transmit information specialized for shortening TTFF for five satellites in one message. As a result, the degree of degradation of the satellite position is within about 10 m for about 10 to 15 seconds with respect to the positioning using the ephemeris. Note that the bandwidth utilization rate when transmitting difference information for 10 satellites once every 10 seconds is 20.0%.

  In order to use this difference method, it is also necessary to transmit an almanac (hereinafter referred to as reference information) as a reference for the difference. The receiver stores reference information in a non-volatile memory before positioning, and uses this information when receiving difference information. Since the reference information has a property that the difference value of the difference information becomes larger with the passage of time, it is necessary to update the reference information at regular intervals before the difference information can be expressed. Further, since the transmission system cannot know when the receiver receives this data, it must be transmitted regularly.

  Further, the bandwidth utilization rate when transmitting the reference information for the GPS 32 satellites in 8 minutes is 6.7%.

  Note that the satellite targeted in Non-Patent Document 2 is a GPS satellite, and when trying to correspond to a quasi-zenith satellite, there is no free space for transmitting difference information, so it is necessary to reduce the number of satellites or the accuracy.

  On the other hand, when assist information can be given from outside at a frequency of about once a month, it is possible to estimate satellite orbit information for a long period of time at the receiver, so that only clock information is transmitted. (Hereinafter referred to as a clock system) is also conceivable. As an example of a message format in the clock system, the format shown in FIG. 7 is conceivable. In this case, information for 10 satellites can be placed on GPS satellites and quasi-zenith satellites in one message, and 10 satellites once every 10 seconds. The bandwidth utilization rate when transmitting the difference information of the minute is 10.0%.

  The difference between the above-described differential method and clock method is its function. In short, the differential method is effective for a receiver that does not obtain assist information from the outside, and the clock method is effective for a receiver that may obtain assist information from the outside. As a transmission system, it is desirable to support a wide range of receiver layers, but the bandwidth utilization rate when data is transmitted to these two types of receivers under the above-described conditions is 20.0%. + 6.7% + 10.0% = 36.7%.

JP 2008-145363 A

Japan Aerospace Exploration Agency: “Quasi-Zenith Satellite System User Interface Specification (IS-QZSS) 1.1 Version”, July 31, 2009, Internet <URL: http://qzss.jaxa.jp/is-qzss /> Takeyasu Sakai "Transmission method of orbit information for shortening GPS initial position calculation time (TTFF)" IEICE Transactions B Vol. J83-A No. 4 pp. 479-486 April 2008

  However, for the L1-SAIF signal, information transmission for improving the positioning accuracy is also necessary, and in order to maintain this performance, it is desirable to increase the frequency of information transmission for improving the positioning accuracy as much as possible.

  It is also desirable to provide an initial position calculation time shortening means that is effective for both positioning signal receivers having satellite orbit information and positioning signal receivers having no satellite orbit information.

  Therefore, the present invention provides a satellite positioning system and positioning signal reception that overcome the above-described problems in a system that determines a position based on a positioning signal transmitted from a satellite positioning system typified by the global positioning system (GPS). Provide machines.

  The present invention relates to a global positioning system, a positioning signal receiving device having satellite orbit information, a positioning signal receiving device having no satellite orbit information, an initial position calculation support information generating device for providing initial position calculation support information, and The satellite positioning system comprising the QZS for transmitting the initial position calculation support information, wherein the initial position calculation support information generating device superimposes clock information and satellite orbit information on the L1-SAIF signal of the QZS. It is transmitted to the positioning signal receiving apparatus having the satellite orbit information and the positioning signal receiving apparatus not having the satellite orbit information.

  According to the present invention, in the positioning signal receiving device having the satellite orbit information, a distance measurement value between the global positioning system / QZS and the positioning signal receiving device having the satellite orbit information, and a positioning having the satellite orbit information. The position of the positioning signal receiving device having the satellite orbit information is determined using the satellite orbit information possessed by the signal receiving device and the clock information. In the positioning signal receiving device not having the satellite orbit information, Positioning value of positioning signal receiver not having satellite orbit information by using distance measurement value between positioning system GPS / QZS and positioning signal receiver not having satellite orbit information, received clock information, and satellite orbit information It is characterized by determining.

  According to the present invention, in a system that determines a position based on a positioning signal transmitted from a satellite positioning system typified by the global positioning system (GPS), the transmission frequency of information for improving positioning accuracy is as high as possible. In addition, the time from activation to position determination can be significantly shortened for both positioning signal receivers having satellite orbit information and positioning signal receivers having no satellite orbit information. .

It is explanatory drawing explaining the system configuration example in one Embodiment of the satellite positioning system concerning this invention. It is explanatory drawing explaining the specific example of the bit assignment format of the satellite orbit information in one Embodiment of the satellite positioning system concerning this invention. It is a figure which shows the example of the GPS indicator and QZS indicator in one Embodiment of the satellite positioning system concerning this invention. It is explanatory drawing explaining the difference in the transmission pattern of one Embodiment of the conventional system and the satellite positioning system concerning this invention. 3 is a flowchart showing a flow of accumulation of reference information of a receiver that requires a differential method in an embodiment of a satellite positioning system according to the present invention. It is explanatory drawing explaining the system configuration example in other embodiment of the satellite positioning system concerning this invention. It is a message format example of a clock system assumed by the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for implementing a satellite positioning system and a positioning signal receiver according to the present invention will be described in detail.

  FIG. 1 shows a system configuration example in an embodiment of a satellite positioning system according to the present invention.

  The satellite positioning system 100 provides a global positioning system (GPS) 101, a positioning signal receiving device 102 having satellite orbit information, a positioning signal receiving device 103 not having satellite orbit information, and initial position calculation support information. The apparatus 104 and the QZS 105 that transmits initial position calculation support information.

  From the initial position calculation support information generation device 104, the positioning signal receiving device 102 having the satellite orbit information by superimposing the clock information and the satellite orbit information on the L1-SAIF signal of QZS having a data rate of 250 bps, and the satellite orbit It is transmitted to the positioning signal receiving apparatus 103 having no information. The positioning signal receiving device 102 having the satellite orbit information determines its own position using the distance measurement value between the GPS / QZS and the positioning signal receiving device, the satellite orbit information possessed by itself, and the received clock information. The positioning signal receiving apparatus 103 that does not have satellite orbit information determines its own position using the distance measurement value between the GPS / QZS and the positioning signal receiving apparatus, the received clock information, and the satellite orbit information.

  FIG. 2 shows a specific bit assignment format of the satellite orbit information of the present invention. This format handles 250 bits as one message. As one embodiment, each message includes an 8-bit preamble, a 6-bit message type ID, 212-bit data, and a 24-bit CRC parity.

  The 212-bit data includes a 2-bit issue number, a 1-bit PRN mask flag, 140-bit difference information, 64-bit reference information, and a 5-bit spare area.

  The issue number is the same number in synchronization with the issue number of the clock information transmitted immediately before this orbit information is transmitted. When the values of the GPS indicator and the QZSS indicator indicated by the clock information are changed, the count is incremented by one. Note that the next of 11 (Bin) is 00 (Bin).

The PRN mask flag is used to identify whether the difference information is information about the 1st to 5th or 10th to 10th information among the 10 satellites of the clock information. For example, as shown in FIG. 3, the 2nd, 5th, 10th, 15th, 19th, 20th, 23rd, 24th and 29th bits from the most significant bit of the GPS indicator, and the 2nd bit from the most significant bit of the QZSS indicator In the case of “1”, if the PRN mask flag is 0, it means that the difference information includes the satellites 2, 5, 10, 15, 19 of GPS. If the PRN mask flag is 1, the difference information This means that the information includes GPS satellites 20, 23, 24, and 29, and QZSS satellite 2. By referring to the clock information as the satellite information in this way, for example, PRN _i −1 and ΔPRN _i −1 that are information for satellite identification can be removed from the difference information of Non-Patent Document 2. In addition, there is no problem in dealing with the quasi-zenith satellite.

As an example, the 140-bit difference information includes 28 satellites of Δx _i , Δy _i , and Δz _i stipulated in the difference information of Non-Patent Document 2, and describes 5 satellites. With respect to the clock, clock information is referred to, and ΔB _i which is a clock difference can be removed.

The 64-bit reference information is data using GPS and QZSS almanac data, and consists of 8-bit t _0a , 6-bit satellite number, 2-bit sequence number, and 48-bit divided almanac.
Here, t _0a is GPS, a t _0a Almanac data corresponding to the satellite number as used in QZSS. This value will change when the transmission system updates the reference information. For example, since the IODA defined in Non-Patent Document 2 can be substituted with t _0a in this way, it can be removed.

  The satellite number means GPS when the most significant bit is 0, and the value obtained by adding 1 to the lower 5 bits is the GPS PRN number. Further, when the most significant bit is 1, it means QZSS, and the value obtained by adding 193 to the lower 5 bits is the QZS PRN number.

、８ビットの平均近点角Ｍ₀の上位1/3が、２フレーム目に１６ビットの軌道傾斜角の基準値との差δ_i、２４ビットの昇交点赤径Ω₀、８ビットの平均近点角Ｍ₀の中間1/3が、３フレーム目に１６ビットの昇交点赤径の変化率

、２４ビットの近地点引数ω、８ビットの平均近点角Ｍ₀の下位1/3が定義される。ａ_f0、及びａ_f1は、は、クロック補正に関するパラメータなので、基準情報から取り除くことができる。 The divided almanac is composed of three frames 1 to 3, and the frame is identified by a sequence number. When the sequence number is 0, the first frame is transmitted with the definition of the first frame, when it is 1, the second frame is transmitted with the definition of the third frame. The split almanac has a 16-bit eccentricity e and a square root of a 24-bit orbital radius in the first frame.

, The upper 1/3 of the 8-bit average near-point angle M ₀ is the difference δ _{i from} the reference value of the 16-bit orbit inclination angle in the second frame, the 24-bit ascending point red diameter Ω ₀ , the 8-bit average The middle 1/3 of the near point angle M _{0 is} the rate of change in the red diameter of the 16-bit rising intersection in the third frame

, A 24-bit near-point argument ω, and a lower 1/3 of the 8-bit average near-point angle M ₀ are defined. Since a _f0 and a _f1 are parameters relating to clock correction, they can be removed from the reference information.

If there is a satellite that exceeds the representation range of the satellite position due to the difference, it is necessary to indicate that the difference information is invalid. A negative maximum value of 800 (HEX) is set for Δx _{i of} such a satellite, and 80 (HEX) is set for Δy _i and Δz _i .

  FIG. 4 shows the difference in transmission pattern between the conventional method and the present invention. Since the clock information stores information for 10 satellites, while the difference information is for 5 satellites, the clock information 1 message corresponds to the difference information 2 message. According to the present invention, it is not necessary to separately transmit the reference information, and the amount of data to be transmitted can be reduced.

A receiver that requires a clock system receives clock information. Among the satellites included here, the initial position can be calculated when positioning signals for four satellites can be received.
A receiver that requires a differential method first receives and holds clock information. Subsequently, the satellite positions for the five satellites can be calculated from the difference information of the satellite orbit information having the same issue number. At this time, positioning can be performed if reference information is already possessed for four of the five satellites and a positioning signal by L1 C / A is received. Subsequently, by receiving satellite orbit information for the remaining five satellites, the number of usable satellites becomes ten.

FIG. 5 is a flowchart showing a flow of storing reference information in a receiver that requires a differential method. The receiver that has received the satellite orbit information whose processing has been started in S501 proceeds to S502, and confirms the satellite number and t _{0a in} order to know whether or not the reference information has been updated. If the t _0a of the satellite already in possession (Yes in S504), if it differs from the t _0a received with t _0a that its possession (No in S505), performing the updating of the transmission system standard information This means that the receiver needs to discard the reference information of all the satellites it possesses (S506).

  Subsequently, the reference information is stored in the received satellite orbit information (S507). At this time, if the divided almanac is prepared for three frames (Yes in S508), then the reference information of the satellite can be used for positioning. (S509). Note that this processing may be omitted if the received reference information is already possessed by the satellite frame, although not described in the flow.

  The reference information is composed of 111 types of data of (GPS 32 satellites + QZS 5 satellites) × 3 frames at the maximum, but the receiver does not mean that positioning cannot be performed unless all these data are accumulated. Positioning becomes possible from the time when a minimum of 4 satellites × 3 frames are available, and the number of satellites that can be targeted increases by further accumulation. Therefore, there is no restriction that the receiver must continuously receive the reference information.

  FIG. 6 shows a system configuration example in another embodiment of the satellite positioning system according to the present invention. The satellite positioning system 600 provides a global positioning system (GPS) 101 / QZS, a positioning signal receiving device 102 having satellite orbit information, a positioning signal receiving device 103 not having satellite orbit information, and initial position calculation support information. And a ground radio apparatus 605 for transmitting initial position calculation support information.

  As the terrestrial wireless device 605 for transmitting the initial position calculation support information according to the present invention, a wireless device that transmits TV radio waves, FM radio waves, or the like can be used.

  In connection with the present invention, all articles and documents filed prior to the filing of this specification and publicly available will be identified, the contents of such articles and documents being incorporated herein by reference. It is.

  All of the features disclosed in this specification (including the appended claims, abstracts, and drawings) and / or all the steps of every method or process so disclosed, such features and / or steps. Can be combined in any combination except combinations where at least some of are mutually exclusive.

  Each feature disclosed in this specification (including the appended claims, abstract, and drawings), unless expressly stated otherwise, for the same purpose, equivalent purpose, or similar purpose. Can be replaced by alternative features that work. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

  The present invention is not limited to any detail of the above-described embodiments. The present invention is directed to novel features disclosed herein (including the appended claims, abstracts, and drawings) or novel combinations thereof, or all methods or processing steps so disclosed or novel features thereof. Extended to combinations.

100 Satellite positioning system 101 GPS
102 Positioning signal receiver 103 having satellite orbit information 103 Positioning signal receiver 104 having no satellite orbit information Initial position calculation support information generator 105 QZS
605 Terrestrial radio equipment

Claims (6)

Global positioning system, positioning signal receiving device having satellite orbit information, positioning signal receiving device not having satellite orbit information, initial position calculation support information generating device for providing initial position calculation support information, and the initial position A satellite positioning system comprising at least a positioning satellite for transmitting calculation support information,
Initial position from the calculated support information generating device, the global positioning system and a clock information indicating the time lag of the positioning satellites, the global positioning system and the global calculated based on the ephemeris and almanac of the positioning satellites The positioning signal and the positioning signal receiving apparatus having the satellite orbit information and at least the satellite orbit information including at least the position difference information of the positioning satellite and the satellite orbit information including information on the almanac are superimposed on the L1-SAIF signal of the positioning satellite. Transmitted to the positioning signal receiver having no satellite orbit information via the positioning satellite,
The clock information and the satellite orbit information are superimposed on the L1-SAIF signal at a ratio of two messages of the satellite orbit information to one message of the clock information. In the positioning signal receiving device not having the satellite orbit information, a first distance measurement value between the positioning satellite and the positioning signal receiving device not having the satellite orbit information, the global positioning system, and the satellite orbit information Determining the position of the positioning signal receiving device not having the satellite orbit information by using the second distance measurement value with the positioning signal receiving device not having the position and the received clock information and satellite orbit information. The system according to claim 1.   3. The system according to claim 1, wherein the initial position calculation support information is transmitted to the positioning signal receiving device by satellite radio. 4.   The positioning satellite is a terrestrial radio device, and the initial position calculation support information is transmitted to the positioning signal receiver by terrestrial radio of the terrestrial radio device. The system described in.   5. The clock information according to claim 1, wherein a bit assignment format handled as one message is 250 bits, and information associated with the clock information is included in the clock information. system. In the positioning signal receiving device having the satellite orbit information, a first distance measurement value between the positioning satellite and the positioning signal receiving device having the satellite orbit information, the global positioning system, and a positioning signal having the satellite orbit information The position of the positioning signal receiving device having the satellite orbit information is determined using the second distance measurement value with the receiving device, the satellite orbit information of the positioning signal receiving device having the satellite orbit information, and the clock information. The system according to claim 1, wherein:

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