JP2011242191A - Position and/or time information distribution device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost position and/or time information distribution device which supplies a signal for a GNSS compatible receiver unit indoors or underground to acquire position and/or time information.SOLUTION: The position/time information distribution device is provided with means for retaining time information, means for retaining information to show a device provision position which is a position for a receiver to acquire, means for retaining orbit information in connection with one or more satellites, means for obtaining speed of the satellites relative to the device provision position and a distance between the device provision position and the satellites on the basis of the time information and the orbit information, and means for generating a signal which time-division multiplexes a false signal from each of the satellites on the basis of the speed and the distance. The false signal is given a propagation delay corresponding to a distance between the relevant satellite and the device provision position and Doppler shift generated by a speed of the relevant satellite relative to the device provision position.

Description

  The present invention simulates signals for positioning and / or time synchronization transmitted by a satellite in a global navigation satellite system (GNSS) typified by a global positioning system (GPS: Global Positioning System). The present invention relates to a device for generating automatically.

  Currently, GPS receivers that acquire position information from signals transmitted by GPS satellites are widely used. In GPS, it is also possible to obtain highly accurate time information, and a radio base station in a mobile communication network obtains time information synchronized with microsecond precision with respect to Coordinated Universal Time (UTC) by a GPS receiver. Yes.

  However, a signal from an artificial satellite cannot often be received indoors or underground, and a system for causing a GPS receiver located indoors or underground to acquire position information and / or time information is required.

  As a method for this, it is conceivable to retransmit a GPS signal received by an antenna installed outdoors from an antenna installed indoors / underground, but the position obtained as a result of positioning by the GPS receiver is an outdoor GPS antenna. There is a problem that the actual position of the GPS receiver and the position to be measured greatly deviate from each other. In addition, there are cases where a great deal of cost is required for laying the cable between the outdoor antenna and the indoor / underground antenna, or the laying is physically difficult.

  It is also conceivable to use an apparatus described in Patent Documents 1 to 4 that generates a signal transmitted by a GPS satellite. However, since the devices described in Patent Documents 1 to 4 are intended to faithfully reproduce actual GPS signals, the configuration of the device is complicated and the cost is increased. In addition, in actual GPS, there are about 10 GPS satellites in the sky, but the number of GPS satellites that can be simulated at the same time may be limited due to the manufacturing cost of the device. In some cases, sufficient positioning and time synchronization accuracy may not be obtained.

  Furthermore, the use of pseudolites (Pseudolites) described in Patent Documents 5 to 9 and Non-Patent Documents 1 and 2 and IMES (Indoor Messaging System) devised for indoor positioning applications can be considered. However, it is not compatible with widely used GPS receivers, and a dedicated receiver is required. Furthermore, IMES cannot obtain time information synchronized with UTC, and cannot be used when highly accurate time information is required, for example, like a radio base station.

Japanese Patent Laid-Open No. 11-304900 JP 2004-286494 A JP 2006-20151 A JP 2008-128934 A Japanese Patent Laid-Open No. 07-113860 JP 07-159508 A JP 2007-278756 A JP 2008-96452 A JP 2009-05928 A

“Pseudolite: Ground-based Transmitter for GPS-Design and Implementation”, Proceedings of the 2003 SBMO / IEEE International Microwave and Optoelectronics. 2, p. 825-830 “Quasi-Zenith Satellite System User Interface Specification”, IS-QZSS 1.2 draft, Japan Aerospace Exploration Agency “Navstar GPS Space Segment / Navigation User Interfaces”, IS-GPS-200D, Navstar GPS Joint Program Office

  Accordingly, an object of the present invention is to provide an inexpensive position and / or time information distribution apparatus that provides a signal for causing a GNSS-compatible receiving apparatus such as GPS to acquire position and / or time information indoors or underground. And

According to the position and / or time information distribution device of the present invention,
Based on the time information, the orbit information, the means for holding the time information, the means for holding the information indicating the device providing position that is the position to be acquired by the receiving device, the means for holding the orbit information of one or more satellites, Means for determining the speed of the satellite as viewed from the device providing position and the distance between the device providing position and the satellite, and means for generating a signal obtained by time-division multiplexing the pseudo signals of each satellite based on the speed and the distance. The satellite pseudo signal is provided with a propagation delay corresponding to the distance between the satellite and the device providing position and a Doppler shift caused by the speed of the satellite viewed from the device providing position. .

According to another embodiment of the position and / or time information distribution device in the present invention,
The one or more satellites preferably include satellites other than those actually used in the global satellite navigation system.

Further, according to another embodiment of the position and / or time information distribution device in the present invention,
Means for holding a code for code division multiplexing assigned to each of the one or more satellites, wherein the means for generating the signal has a cumulative value of the change in the propagation delay of the satellites having a predetermined threshold value; It is also preferable to determine whether or not it exceeds the code by a repetition period of the code, and when the predetermined threshold is exceeded, it is also preferable to adjust the code length of the satellite.

Furthermore, according to another embodiment of the position and / or time information distribution device of the present invention,
It is also preferable that the trajectory correction term of the trajectory information and the parameter for correcting the influence of the ionosphere are zero.

  High-precision positioning and / or time synchronization is possible indoors and underground. In addition, the pseudo-signals of the satellites are not generated in parallel but are processed in a time-sharing manner, so that the device configuration can be simplified and a position and / or time information distribution device can be realized at low cost. Also, by using a fictitious satellite, it is possible to realize a satellite arrangement that can suppress deterioration in time synchronization and positioning accuracy, reduce the number of pseudo signals to be generated, and By omitting the parameters for correcting the trajectory correction term and the influence of the ionosphere, the amount of calculation related to the propagation delay time can be reduced.

1 is a schematic configuration diagram of a position and / or time information distribution apparatus according to the present invention. It is a schematic block diagram of a pseudo signal generation part. It is a figure explaining adjustment of a PRN code length. It is a figure which shows one form of a Doppler control part and a modulation | alteration part. It is a figure which shows the orbit in an imaginary satellite arrangement | positioning. It is a figure which shows the time change of the receiving satellite number in the satellite arrangement | positioning of FIG. It is a figure which shows the time change of the positioning precision degradation index in the satellite arrangement | positioning of FIG. It is a figure which shows the orbit for the predetermined period of an actual GPS satellite. It is a figure which shows the time change of the number of receiving satellites in the satellite arrangement | positioning of FIG. It is a figure which shows the time change of the positioning accuracy degradation index in the satellite arrangement | positioning of FIG. It is a figure which shows the positioning error of the latitude and longitude direction in the satellite arrangement | positioning of FIG. It is a figure which shows the time change of the altitude direction positioning error in the satellite arrangement | positioning of FIG. It is a figure which shows the orbit in an imaginary satellite arrangement | positioning. It is a figure which shows the time change of the number of receiving satellites in the satellite arrangement | positioning of FIG. It is a figure which shows the time change of the positioning accuracy degradation index in the satellite arrangement | positioning of FIG. It is a figure which shows the positioning error of the latitude and longitude direction in the satellite arrangement | positioning of FIG. It is a figure which shows the time change of the altitude direction positioning error in the satellite arrangement | positioning of FIG.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated in detail below using drawing. In the following description, a pseudo signal of a signal transmitted from a GPS satellite (Navstar) is generated and distributed to a GPS receiver, but the present invention is used for generating a pseudo signal of another GNSS satellite. Is also applicable.

  The position and / or time information distribution apparatus according to the present invention generates a pseudo signal of a plurality of GPS satellites, but transmits only a pseudo signal of one GPS satellite at a certain moment. That is, based on a certain rule, the pseudo signal of each GPS satellite is transmitted in a time division manner. In addition, as this rule, there are a method of switching at a constant period and a method of controlling by some kind of pseudo-noise code.

  FIG. 1 is a schematic configuration diagram of a position and / or time information distribution apparatus according to the present invention. As shown in FIG. 1, the position and / or time information distribution apparatus includes a satellite simulation unit 1, a pseudo signal generation unit 2, a modulation unit 3, a synchronization processing unit 4, and a satellite information holding unit 5. Yes.

  The satellite information holding unit 5 holds information on each satellite to be simulated, specifically, orbit information for specifying the orbit of the satellite and information on the PRN code assigned to the satellite for code division multiplexing. Yes. Details of the trajectory information are described in Non-Patent Document 3. The synchronization processing unit 4 outputs time information synchronized with a reference time such as UTC to the satellite simulation unit 1 and the pseudo signal generation unit 2, and generates a carrier wave synchronized with the clock obtained from the time information to generate the modulation unit 3. Output to. The synchronization processing unit 4 uses time synchronization protocols such as NTP (Network Timing Protocol) and PTP (Precision Time Protocol) defined by IEEE 1588, for example, via a network (not shown) that synchronizes time information with high accuracy to the reference time. Get in.

  The satellite simulation unit 1 holds information indicating a position to be acquired by the GPS receiver. Here, the position to be acquired by the GPS receiver is, for example, the position where the position and / or time information distribution device is installed, or the floor where the position and / or time information distribution device is installed indoors or underground. And a predetermined position on the same floor. Hereinafter, a position to be acquired by the GPS receiving device is referred to as a device providing position. The satellite simulation unit 1 calculates the distance between the satellite and the device provision position and the speed of the satellite viewed from the device provision position in the pseudo signal transmission period of each satellite, and identifies the satellite being simulated. The information, the calculated distance to the satellite, and the speed of the satellite are output to the pseudo signal generation unit 2, and the pseudo signal generation unit 2 determines the satellite based on the satellite information of the satellite, the speed, and the distance from the device providing position. A pseudo signal is generated.

  Note that since GPS satellites orbit around the earth, there are GPS satellites that are not visible from the device providing position and do not receive signals in a certain time zone. Also in this embodiment, for each simulation target GPS satellite, in the time zone that is not visible from the device providing position, transmission of the GPS satellite pseudo signal is omitted, and only the GPS satellite pseudo signal visible from the device providing position is transmitted. It shall be transmitted in divisions. Whether or not it can be seen from the device providing position is determined by, for example, the satellite simulation unit 1 from the time information, the orbit information of each simulation target GPS satellite, and the device providing position. In this case, the satellite simulation unit 1 outputs only the distance and speed of the GPS satellite that can be seen from the device providing position to the pseudo signal generation unit 2. However, regardless of whether it can be seen from the device providing position, a form in which pseudo signals of all the simulation target GPS satellites are always transmitted in time division may be used.

  FIG. 2 is a schematic configuration diagram of the pseudo signal generation unit 2. As shown in FIG. 2, the pseudo signal generation unit 2 includes a PRN code generation unit 21, a navigation message generation unit 22, an exclusive OR operation (EXOR) unit 23, a delay control unit 24, and a Doppler control unit 25. And.

  The PRN code generation unit 21 generates the PRN code of the simulation target satellite based on the satellite information at a timing determined by GPS, and the navigation message generation unit 22 generates the navigation message of the simulation target satellite based on the satellite information. To do. As is well known, the PRN code is for code division multiplexing, and the GPS receiver acquires the transmission timing of the PRN code from the satellite based on the PRN code, and uses the navigation message to The satellite position information and the transmission time of the PRN code are acquired, and for example, time information synchronized with UTC and current position information are acquired by receiving signals from four or more satellites. The EXOR unit 23 outputs an exclusive OR value of the PRN code generated by the PRN code generation unit 21 and the satellite navigation message generated by the navigation message generation unit 22, that is, a C / A code.

  Here, it is necessary to give a propagation delay corresponding to the distance between the device providing position and each simulation target satellite to the simulation signal of each simulation target satellite. Therefore, the delay control unit 24 obtains the propagation delay amount of each simulation target satellite based on the speed and position information of each simulation target satellite, and outputs them to the PRN code generation unit 21 and the navigation message generation unit 22, respectively. The PRN code generation unit 21 and the navigation message generation unit 22 determine the phase of the PRN code and navigation message that are generated based on the propagation delay amount.

  Further, since the distance between the simulation target satellite and the device providing position changes with time, the propagation delay amount also changes with time, which is recognized by the GPS receiver as a change in the length of the PRN code. That is, in order to accurately simulate the signal transmitted by the GPS satellite, it is necessary to adjust the width of each chip of the PRN code in accordance with the change in the distance to the GPS satellite. However, in the present invention, rather than adjusting the width of each chip of the PRN code, does the accumulated value of the change in the propagation delay amount exceed a predetermined threshold value every 1 millisecond, which is the PRN code repetition period? If it exceeds, the PRN code length corresponding to the change in the propagation delay amount is adjusted in the period or the next period.

  For example, the PRN code used in GPS repeats 1023 chips at a cycle of 1 millisecond, but in FIG. 3, t1 millisecond, which is the cumulative value of the change in PRN code length, is used as the last chip. Are adjusted together. As an example, if the PRN code length is adjusted in units of about 9.775 nanoseconds (1 / 102.3 MHz), the maximum value of the change in propagation delay in one PRN code period is about 3.1 nanoseconds. The interval for adjusting the PRN code length is the shortest and is once every three PRN code periods. In this way, instead of adjusting the amount of change in propagation delay for each chip, it is possible to perform simulation without increasing the time resolution of the apparatus by adjusting collectively after exceeding the threshold value. It should be noted that the amount of change can be adjusted by other than the last chip. When the time length of the PRN code is adjusted, the time length of the navigation message generated by the navigation message generating unit 22 is also adjusted so as to be synchronized with the PRN code.

  The Doppler control unit 25 obtains the amount of frequency change caused by the Doppler effect based on the speed of the satellite to be simulated, and changes the frequency of the delay-adjusted C / A code output from the EXOR unit 23 by this amount of change. . That is, the Doppler shift generated by the speed of the simulation target satellite as viewed from the device providing position is given to the simulation signal of the simulation target satellite.

  Returning to FIG. 1, the modulation unit 3 modulates the carrier wave with the output signal of the pseudo signal generation unit 2 and then transmits it as a radio signal from an antenna (not shown), or is built in a radio base station or the like via a coaxial cable. Input directly to the GPS receiver.

FIG. 4 is a diagram illustrating one form of the Doppler control unit 25 and the modulation unit 3. Note that the phase amount to be shifted in both phase shift portions in FIG. 4 is 90 °. As shown in FIG. 4, the modulation unit 3 performs quadrature modulation at the carrier frequency f _c (= 1575.42 MHz), and the Doppler control unit 25 converts the output signal of the EXOR unit 23 into the in-phase component (I). after distributing the quadrature component (Q), for each component, giving a variation f _d of the frequency due to the Doppler effect. Instead of continuously changing the f _d in this embodiment, between the PRN code one period is the same value, it is assumed to change its value at a timing one period is over, other times It may be a form that is changed in the above or a form that is continuously changed. In addition, the C / A code as well as the carrier wave of the GPS signal varies due to the Doppler effect. This has already been adjusted by adjusting the change in the propagation delay amount for the PRN code and the navigation message described above. In the signal transmitted from an actual GPS satellite, the phase relationship between the C / A code and the carrier wave is maintained. However, in a single positioning method receiver used in a navigation system or a radio base station, Since the phase relationship does not affect the GPS reception process, the modulation unit 3 does not consider this phase relationship in the present invention.

  The satellite simulation unit 1 and the pseudo signal generation unit 2 shown in FIG. 1 can be realized by a DSP and / or FPGA, and the apparatus can be reduced in size and cost. In the above embodiment, the pseudo signal generation unit 2 is used in a time-sharing manner, that is, one pseudo signal generation unit 2 sequentially generates the pseudo signals of the satellites. However, the pseudo signal generation unit 2 corresponding to the satellite to be simulated is provided, and the pseudo signal of each satellite generated by each pseudo signal generation unit 2 is selected in order, so that the pseudo signal of each satellite is time-division multiplexed. A method of generating a signal may be used.

  As described above, the GPS receiving device that has received the radio signal from the position and / or time information distribution device according to the present invention obtains the position information corresponding to the device providing position set in the position and / or time information distribution device and the time information. Will get. Therefore, by installing the position and / or time information distribution device according to the present invention indoors, the GPS reception device can acquire position information and / or time information even indoors.

  The satellite information holding unit 5 sets the orbit information of the actual GPS satellites, thereby setting the orbit of the fictitious satellite as well as the mode of transmitting the pseudo signal of each satellite in time division. A mode may be used in which only the pseudo signals of the satellites are transmitted in a time division manner, or the pseudo signals of an imaginary satellite and an actual satellite are transmitted in a time division manner. By using an imaginary satellite, for example, a satellite arrangement that can suppress deterioration in time synchronization and positioning accuracy can be realized. In addition, if parameters that compensate for satellite perturbations (orbit correction terms) and ionosphere effects are not used, that is, they are simulated as zero, radio wave propagation time control between the satellite and receiver can be simplified. , Device cost can be reduced. In addition, since the information regarding the orbit of each satellite is included in the navigation message, the operation of the GPS receiver is not affected even if an imaginary satellite is used.

  FIG. 5 is a diagram showing the orbits of 24 fictitious GPS satellites. FIG. 5 is a view from a point where the latitude and longitude are 0 degrees and the altitude is 0 meters. The dotted line and the solid line are each one orbit, and 12 satellites orbit around each orbit. ing. The parameters of each satellite in the orbit shown in FIG. 5 are shown in the following table.

  Note that the orbit correction term, satellite average motion correction, elliptical orbit eccentricity, near-point argument, rate of change in red diameter at the ascending intersection at the first time of the orbit, and rate of change in orbit tilt angle are zero for all satellites. The square root of the radius is 5153.804420 for all satellites and the ephemeris data epoch is the first time of the week for all satellites. Also, the parameter values related to satellite time correction, ionosphere correction, and UTC correction are all zero.

  The position and / or time information distribution device is set on the equator with the above-mentioned fictitious satellite and the device providing position at latitude and longitude of 0 degrees and altitude of 0 meters, and the elevation mask of the GPS receiver is 10 degrees. FIG. 6 shows the time variation of the number of received satellites when the all-in-view method is used, and FIG. 7 shows the time variation of a general positioning accuracy degradation index (PDOP) as a positioning accuracy index. Note that the position and / or time information distribution device used in each of the following measurements is provided with a pseudo signal generation unit 2 corresponding to each simulation target satellite, and by selecting a signal from each pseudo signal generation unit 2 in order. In this configuration, the division multiplexed signal is generated, and the selection cycle of each pseudo signal is about 4.9 microseconds. Further, the elapsed time in the figure is the elapsed time from the first time of the week. From the figure, it can be confirmed that the signal from 5 or 6 satellites can be received at all times, and that the PDOP is always in the range of 1.8 to 2.6 and the fluctuation range is small. In actual GPS, the number of satellites that appear in the sky is usually around 10, and it can be seen that stable time synchronization and positioning can be achieved with about half of the number of satellites in the sky.

  The position and / or time information distribution device is set to 7 GPS satellites, and the device provided position is set on the equator with latitude and longitude 0 degrees and altitude 0 meters, and a commercially available 12-channel all-in-view GPS The results of positioning by the receiving device are shown in FIGS. FIG. 8 is a view of the orbits of the seven satellites as seen from a point where the latitude and longitude are 0 degrees and the altitude is 0 meters, and the solid line portion is the measurement period. The following table shows the parameters of each satellite in the orbit shown in FIG.

  Note that the orbit correction term, satellite average motion correction, elliptical orbit eccentricity, near-point argument, rate of change in red diameter at the ascending intersection at the first time of the orbit, and rate of change in orbit tilt angle are zero for all satellites. The square root of the radius is 5153.881067887503 for all satellites and the ephemeris data epoch is the first time of the week for all satellites. Also, the parameter values related to satellite time correction, ionosphere correction, and UTC correction are all zero.

  Note that this orbit is based on the actual GPS satellite orbit at week number 492 (the week starting on January 25, 2009, 0:00 GMT), and the eccentricity of the orbit and the perturbation of the satellite. It is a simplification that ignores.

  The step of controlling the frequency change by the Doppler effect was 0.0238 Hz, and the period of time division multiplexing of the satellite was 4.90 microseconds. 9 shows the time change of the number of received satellites, FIG. 10 shows the time change of PDOP, FIG. 11 shows the positioning error in the latitude and longitude directions, and FIG. 12 shows the time change of the altitude direction positioning error. From the figure, it can be confirmed that the PDOP is 2.4 to 2.7, and the positioning accuracy is 3 meters in the latitude / longitude direction and 22 meters in the height direction. The time synchronization accuracy was confirmed to be within 130 nanoseconds.

  Further, the position and / or time information distribution apparatus is set with seven imaginary GPS satellites shown in FIG. 13 and the apparatus providing position on the equator with latitude and longitude of 0 degrees and altitude of 0 meters. The results of positioning with the channel all-in-view type GPS receiver are shown in FIGS. FIG. 13 is a view as seen from a point where the latitude and longitude are 0 degrees and the altitude is 0 meters. Each orbit has one satellite, and the solid line portion is the measurement period. FIG. 13 shows a fictitious satellite as a geostationary satellite and a satellite that exists in a fictitious orbit at the quasi-zenith satellite altitude. The parameters of each satellite in the orbit shown in FIG. 13 are shown in the following table.

  Note that the orbit correction term, satellite average motion correction, elliptical orbit eccentricity, near-point argument, rate of change in red diameter at the ascending intersection at the first time of the orbit, and rate of change in orbit tilt angle are zero for all satellites. The square root of the radius is 6493.39456147553 for all satellites, and the ephemeris data epoch is the first time of the week for all satellites. Also, the parameter values related to satellite time correction, ionosphere correction, and UTC correction are all zero.

  The frequency change control step by the Doppler effect was 0.0238 Hz, and the time division multiplexing period of the satellite was 4.90 microseconds. 14 shows the time change of the number of received satellites, FIG. 15 shows the time change of PDOP, FIG. 16 shows the positioning error in the latitude and longitude directions, and FIG. 17 shows the time change of the altitude direction positioning error. From the figure, it can be confirmed that PDOP is 2.4, and the positioning accuracy is 2 meters in the latitude / longitude direction and 14 meters in the height direction. The time synchronization accuracy was confirmed to be within 140 nanoseconds.

  As described above, by using the position and / or time information distribution device according to the present invention, highly accurate positioning and time synchronization can be performed indoors and underground. In addition, the position and / or time information distribution device can be obtained by processing the pseudo signals of each satellite in a time-sharing manner and further omitting parameters for correcting the influence of the orbit correction term and ionosphere among the parameters related to the orbit of the satellite. It can be realized at low cost. In the above-described embodiment, the position and / or time information distribution device simulates a plurality of satellites. However, like a radio base station in a mobile communication network, when the installation position is known and fixed and only time information is required, it is only necessary to receive a pseudo signal from one satellite. Therefore, in such a case, when transmitting a pseudo signal of a satellite that cannot be seen from the device providing position, for example, only one satellite on a geostationary orbit can be simulated.

DESCRIPTION OF SYMBOLS 1 Satellite simulation part 2 Pseudo signal generation part 3 Modulation part 4 Synchronization processing part 5 Satellite information holding part 21 PRN code generation part 22 Navigation message generation part 23 Exclusive OR operation part 24 Delay control part 25 Doppler control part

Claims (4)

Means for holding time information;
Means for holding information indicating a device providing position that is a position to be acquired by the receiving device;
Means for maintaining orbital information for one or more satellites;
Means for determining the speed of the satellite viewed from the device providing position and the distance between the device providing position and the satellite based on the time information and the orbit information;
Means for generating a time-division multiplexed signal of each satellite based on the speed and the distance;
With
The pseudo signal of the satellite is given a propagation delay corresponding to the distance between the satellite and the device providing position, and a Doppler shift caused by the speed of the satellite viewed from the device providing position.
Location information distribution device. The one or more satellites include satellites other than those actually used in a global satellite navigation system;
The position information distribution device according to claim 1. Means for holding a code for code division multiplexing assigned to each of the one or more satellites;
The means for generating the signal determines whether or not the cumulative value of the change in the propagation delay of the satellite exceeds a predetermined threshold value when the code repeat period unit is exceeded, and when the predetermined threshold value is exceeded. Adjusts the code length of the satellite,
The position information distribution device according to claim 1 or 2. Parameters for correcting the trajectory correction term of the trajectory information and the influence of the ionosphere are zero.
The position information distribution device according to any one of claims 1 to 3.

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