KR20050005201A - Down link typed location estimating system of terminal system and method therefor - Google Patents

Abstract

The present invention relates to a downlink type location tracking system of a location tracking terminal for tracking the location of a location tracking terminal using a wireless network independently constructed for location tracking, and a method thereof. A time synchronization device having a reference clock oscillator and synchronizing the time between base stations, an information storage unit for storing information to be transmitted as a position tracking signal, and information synchronized in time with the GPS time based on the clock of the time synchronization unit. A base station comprising a base station and a terminal station including means for modulating the position tracking signal of the storage unit into a transmission signal and an RF transmitter for radio transmission of the modulated signal through an antenna, and a position tracking signal transmitted by the base stations. After receiving and measuring the difference of arrival time of each received signal based on its own clock, this side It consists of a terminal that calculates its own location by using a value. It can reduce the power consumption of the terminal and can reduce the size of the battery. Therefore, the terminal can be miniaturized and can be stored in an existing mobile phone. In order to solve this difficulty, the invention has the advantage of providing the terminal location stably in emergency call such as 119 phone.

Description

DOWN LINK TYPED LOCATION ESTIMATING SYSTEM OF TERMINAL SYSTEM AND METHOD THEREFOR}

The present invention relates to a system and method for tracking the location of a location tracking terminal (hereinafter referred to as a 'terminal') using a wireless network independently constructed for location tracking, and more particularly, an ultra-precise GPS visual synchronization device. When the base station having a built-in and the terminal station synchronized with the base station signal transmits a location tracking signal, the terminal determines the location of the location tracking terminal using the difference in the reception time of the signal. Type) Location tracking system and method.

Conventionally, the location tracking method, which is commercialized in the related art, transmits a radio wave containing information for location tracking in the terminal 10 and receives the uplink (received) from the main station 1, which is synchronized with a high precision time around. The main station 1 receiving the signal of the terminal 10 measures the radio wave transmitted by the terminal 10 and transmits it to the position calculating device 5 and the position calculating device 5. ) Calculates the location of the terminal 10 by collecting the information collected by each base station 1 and transmits the calculation result to the terminal 10 and the user on the network.

However, since the conventional location tracking system is configured in the uplink method, the terminal 10 must transmit a signal with a large power of a certain output or more, and thus the transmission part or the battery of the terminal 10 cannot be miniaturized. Note that the communication network is necessary because the signal must be transmitted to the position calculating device 5, and the main station 1 cannot be placed too far because the terminal 10 must capture the signal transmitted. There was a problem that the density of the base station 1 is relatively high.

The present invention has been invented to improve the above problems, and exists at a precisely measured position, and means GPS coincidence (time: coincidence of expression information at a fixed point in time: for example, A clock at any point in time). If the time point indicated by and clock B is 1 minute, this 1 minute is the time difference value) and the time (time: flow coincidence: for example, the exact difference between A and B clocks is 1 second after 1 hour. If there is a 1 second / 1 hour is a time error value, the main station and the terminal station that generate a signal synchronized with the terminal transmits the signal and configures it by the downlink method that the terminal receives. It is possible to reduce the construction cost of the base station by lowering the density of the base station that transmits the signal for transmitting the signal. Also, the terminal can be changed to the form of receiving only so that the size can be made extremely small. As to provide a downlink-type positioning systems and their methods of enemy terminal it is an object.

1 is a block diagram of a conventional uplink location tracking network,

2 is a configuration diagram of a location tracking system according to the present invention;

3 is a block diagram of a terminal according to the present invention;

4 is a block diagram of a main base station according to the present invention;

5 is a block diagram of a seed station according to the present invention,

6 is a block diagram of main information according to the present invention;

7 is a configuration diagram of auxiliary information according to the present invention;

8 is an IPDL diagram according to the present invention.

* Description of the symbols for the main parts of the drawings *

10-terminal, 11-RF receiver,

12-PN code demodulation unit, 13-Arrival time measurement unit,

14-processor, 20-GPS satellites,

22-main station, 22A-visual synchronization unit,

22B-data storage, 24-boil station,

41, 51-GPS receiver, 42, 52-cesium oscillator,

43, 53-comparators, 44, 54-main information storage,

45, 55-auxiliary information storage, 46, 56-information processor,

47, 57-code generator, 48, 58-RF transmitter,

49, 59-antenna.

A downlink type positioning system of a positioning device according to the present invention for realizing the above object comprises a main station having a visual synchronization device for maintaining a measurement error of 10 nsec or less using a GPS receiver and a cesium oscillator, After receiving the base station signal and receiving the base station of the type synchronizing the Rubidium-embedded visual synchronization device and the location tracking signal transmitted by the base stations, and measuring the difference in the arrival time of each signal based on its internal clock It has a structure that consists of a terminal that calculates its position using the measured values.

The location tracking signal transmitted by the main station and the terminal station is composed of main information consisting of time delay information, time value, base station health information, base station group number, base station location information, and PN of neighboring base station. It consists of auxiliary information consisting of code information and location information of neighboring base stations.

In addition, in the above, the main station has a GPS receiver which generates time information synchronized with GPS time and a clock of 1 [pulse / second], a cesium oscillator which generates its own precision signal of 10 ^-13 or more, a GPS signal and a cesium oscillator. Comparator to remove the error by adjusting cesium oscillator to measure the difference in time and to measure the difference in time, and the main information of the base station stored in the GPS receiver's visual information and main information storage and auxiliary information storage. And an information processor for outputting auxiliary information, a code generator for coding and outputting the output signal of the information processor, and an RF transmitter for wireless transmission of the code signal of the code generator.

In addition, in the above, the terminal station is the main station signal receiver which generates time information and reference clock synchronized with the main station signal, the rubidium (or crystal oscillator) which generates its own precise signal, the time of the main station signal and the rubidium oscillation period. When the difference is measured and the error occurs more than the reference value, the comparator is used to eliminate the error by adjusting the rubidium oscillator (or crystal oscillator), and it is stored in the visual information of the main station signal receiver, the main information storage unit and the auxiliary information storage unit. It comprises an information processor for outputting the main information and auxiliary information of the base station, a code generator for encoding and outputting the output signal of the information processor and an RF transmitter for wireless transmission of the code signal of the code generator.

The downlink type location tracking method of the location tracking terminal according to the present invention comprises the steps of: transmitting a location tracking signal synchronized with the GPS time at the periodic base station and synchronized with the periodic station signal at the terminal station; Obtaining the position center point of the receiving base station by receiving, obtaining a new position value of each base station by performing the coordinate transformation of the center point as the origin, the north pole as the Y axis, and the direction away from the origin as the Z axis, the transformation In the new position value, all Z values are assumed to be “0”, and the TDOA calculation is performed using the value of XY only, and then converted to the original coordinate system to calculate the position of the terminal.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 shows a configuration diagram of a location tracking system according to the present invention.

GPS satellites (20: 20a, 20b, 20c, 20d…) were developed by the US Department of Defense and used for military purposes, but are rapidly expanding into civilian use due to economic and usefulness, and are now being used as the most common navigation system. 4 satellites on 6 circular orbits with a 55 ° tilt angle are located 26567.5 km from the center of the earth and have a period of about 12 hours, which is a GPS satellite positioning of the user It is specially designed so that at least four satellites are always visible across the globe to calculate the error. Satellite data transmitted from each GPS satellite is transmitted to the user by Code Division Multiple Access (CDMA) including PRN code (Pseudo Random Noise code) specially designed for each satellite number. The navigation data corresponding to each satellite can be clearly received.

As shown in FIG. 4, the main base station 22 includes a visual synchronization unit 22A, a main information storage unit 44, and auxiliary information including a GPS receiver 41, a cesium oscillator 42, and a comparator 43. A data storage unit 22B for storing various position tracking information in the storage unit 45 and periodically outputting the code generator 47 for generating a code for transmitting the position tracking data of the data storage unit 22B; And an RF transmitter 48 for transmitting the position tracking data as an RF signal.

The GPS receiver 41 uses a general GPS receiver and is provided with pulse information of 1 pulse per second (PPS) synchronized with GPS time, and the 1 PPS pulse is visual information generated by the cesium oscillator 42. To measure the error of The visual information itself is an auxiliary function that sends the terminal 10 as auxiliary information so that the terminal 10 can also be used as a watch.

The cesium oscillator 42 is preferably used in the form of adjustable frequency and 1 PPS. GPS is good enough to have a long-term stability of "0", but short-term stability (in the case of GPS receivers, it is not enough to indicate stability and jitter or jump is appropriate) is 1 usec. Since it cannot be used as a circle, the cesium output, which is excellent in short-term stability and long-term stability, is used as a visual source, and the lack of long-term stability of cesium itself is compensated by GPS. The cesium is calibrated at the point of time when the visual error is about 100 nsec. The cesium oscillator 42 has a calibration cycle within several hours at the beginning of operation, but the calibration cycle becomes longer as the operation period becomes longer, so that the calibration of the cesium oscillator 42 takes about one month in a normal situation (about 2-3 months later). desirable.

The comparator 43 continuously compares the 1 PPS output of the cesium oscillator 42 and the 1 PPS output of the GPS receiver 41 by the least square method to calculate a frequency component and a visual error component. The visual error component has many error components at first due to the characteristic of least square method, so it is not applied within the first three hours, but reflects the previous error value and applies the calculated value afterwards.

The data storage unit 22B is a main information storage unit 44 and a main storage unit which store main information including time delay information, time value, and health information of the base station on a base station-specific PN Code to be transmitted by the base station as a location tracking signal. And an auxiliary information storage unit 45 for storing auxiliary information consisting of a base station group number, location information of a base station, PN code information of neighboring base stations, and location information of neighboring base stations, and reading the main information and auxiliary information. It consists of an information processor 46 for outputting, and the information processor 46 is configured to input visual information output from the GPS receiver 41. Hereinafter, the main information and the auxiliary information will be described in more detail.

The time delay value on the PN Code stored in the main information storage unit 44 is nsec. The RF transmitter 48 connected to the output terminal, the linear power amplifier (LPA) and the cable (not shown), and the antenna 49 are connected. It is a value including delay of sending by.

The time information is also stored in the main information storage section 44. For example, it consists of 4 bytes, and is a time value of a second in which 0: 0: 0 second is "0" on January 1, 2000, and the period is about 136 years. Has This time information is not a time value consistent with GPS but a time value consistent with UTC.

In addition, the base station health information is also stored in the main information storage unit 44, the terminal determines the availability of the base station information is also important information for facility maintenance for the operator operating the base station. The maintainer is the information provided to enable the maintenance by installing the terminal in the nearest and grasping the health information of the base station without having to turn off the wire to the actual base station. The main contents are information on air conditioner, heater, cesium / rubidium, GPS receiver / period signal receiver, main processor, code generator and RF transmitter.

On the other hand, the main station group number stored in the auxiliary information storage unit 45 is a part for differentiation from the neighboring main station group, which means that the neighboring base station or its base station information among the base station information held by the base station under the corresponding main station. Since the time delay value applied to the subordinate base station is not known, the receiver does not blindly determine the time delay value of the neighboring main base station group from the base station information obtained from the single base station. can do.

The PN (Pseudo Noise) code number is also stored in the auxiliary information storage unit 45. The PN (Pseudo Noise) code number is the base station PN number that is actually allocated regardless of the main station group number or each base station number. A PN number and a higher PN number of 512 to 1023 are allocated so that one base station has two PN numbers while the number difference between the two PN numbers is 512. The lower PN number is used to transmit the main information, the higher PN number is used to transmit the auxiliary information signal, the lower PN data uses the maximum transmission power, and the higher PN data uses the lower power PN data. 4/10 of the power is sent out. The code carrying the supplementary information is not used for measurement but only for receiving data and the rest of the information can be known by receiving any one, whereas the PN containing the main information is used for the arrival time measurement and the data itself is used for the measurement. Therefore, the main information signal is sent out loud. The top of the PN code is all filled with "0", which is also the reference position when the terminal demodulates QPSK.

Base station location information is also stored in the auxiliary information storage unit 45, and only one geocentered earth fixed (ECEF) rectangular coordinate system based on the World Geodetic System (WGS-84) is provided. This is because these types are common and can be freely deformed in any coordinate system. The terminal calculates a plane equation passing through the received coordinate points, and then calculates a position on the plane and converts it into a desired coordinate system.

The information processor 46 acts to convert the information data output from the main information storage unit 44 and the auxiliary information storage unit 45 into a serial signal and output the serial signal. The information processor 46 has a first information processor 46a. ) And two second information processors 46b. The first information processor 46a processes main information and the second information processor 467b processes and outputs auxiliary information.

The code generator 47 is identical to the code generation portion of conventional CDMA. In the preferred embodiment of the present invention, the number of codes that can be allocated is limited to 1000. In this case, since the length of the PN code is 131072 bits and has a period of 100 msec, 10 codes are transmitted per second. Therefore, the terminal that performs the location tracking in the code frame unit can identify the distance within a distance of 100 msec [code frame length] X 3E8 [m: luminous flux] = 30000 km. Like the information processor 46, the code generator 47 is composed of two sets of the first code generator 47a and the second code generator 47b, and the first code generator 47a has main information and a second code generator ( In 47b), auxiliary information is loaded and output.

The RF (Radio Frequency) transmitter 48 modulates and transmits code information generated by the code generator 47 by Quadrature Phase Shift Keying (QPSK). The transmission output is manually adjustable and compared with the main information code. The auxiliary information holds, for example, 1/8 transmit power. The antenna 49 is a vertical antenna and has a non-directional direction in the ground direction. Also, in order to prevent the terminal located near the base station from receiving the signal from the far base station due to the large power transmission of the latest far base station, the output period may be lowered for a predetermined time to receive the weak signal of the far base station. IPDL section is synchronized to the frame clock and has a length of 195.3125usec, and within the section, the transmission power is reduced to 1/10 to 1/100 depending on the size of the transmission power. This low power transmission interval occurs at a level of once every 0.1 seconds, so it occurs 10 times per second. The low power transmission section within 100 msec performs low power transmission by 195.3125usec in the order of PN, and the reference is the standard time of every second (see Fig. 8).

Next, the structure of the transmission data transmitted for the location tracking from the base station will be described.

Although the transmission data transmitted from the first RF transmitter 48a and the second RF transmitter 48b of the RF transmitter 48 are different as the main information and the auxiliary information, the data structure has essentially the same structure.

The main information consists of information about the base station. In the embodiment of the present invention, for example, as shown in FIG. 6, the preamble 5 bytes, the group number 1 byte, the PN number 2 bytes, the time delay value 2 bytes, and the location information 12 bytes. It consists of a total of 32 bytes, such as 4 bytes of time value, 4 bytes of base station health information, 2 bytes of CRC, and is modulated at 2560 bps to be transmitted 10 times per second.

The auxiliary information consists of information on the location of the base station. In the embodiment of the present invention, unlike the main information, as shown in FIG. 7, for example, 33 pieces of 13 bytes of preambles and 15 bytes of length per neighboring base station are used instead of time information. Information and finally 32 CRC codes of 4 bytes, 13 bytes + 15 × 33 + 4 = 512 bytes 4096 bits, sent in 12.8 second cycles, this information is sent at 1 / 8th the power of the main information.

Next, the seed station 24 will be described.

At the seed station 24 for time synchronization, the main station 22 receives the GPS signal and synchronizes it with cesium, whereas the main station 22 receives the signal from the main station 22 and receives rubidium or Oven-Controlled Crystal Oscillators (OCXO). The main station signal receiver 51 is provided so as to synchronize (hereinafter referred to as a rubidium oscillator).

This type is possible because the signal source of the main base station 22 is so accurate and the main station 22 and the terminal station 24 do not move, so there is little reason to cause an error. The output of the rubidium oscillator 52 should be controlled by the output time in consideration of the delay time due to the distance from the main station 22 to the terminal station 24, and should be synchronized with the sending time of the main station 22 as much as possible. do. Tolerance shall be kept within 10nsec.

Like the main station 22, the terminal station 24 compares the 1 MHz output of the main station signal receiver 51 with the 1 MHz output of the rubidium oscillator 52 in the comparator 53, and compares the frequency and time of the rubidium oscillator 52 with each other. Match with main station signal. In addition, the main information stored in the main information storage unit 54 and the auxiliary information stored in the auxiliary information storage unit 55 in the same form as the main base station 22, the first information processor 56a and the second of the information processor 56. The information processor 56b divides and outputs the data in a row, and then the main information and the auxiliary information are first code generator 57a, second code generator 57b, first RF transmitter 58a, and second RF transmitter 58b, respectively. Is sent through).

At this time, since the delay time of the terminal station 24 itself is adjusted to " 0 " However, since it is reflected as much as the delay time of the main station 22, the information of the main station 22 is analyzed and the delay period value of the main station is applied as its own delay time value.

Next, the terminal 10 will be described with reference to FIG. 3.

The terminal 10 includes an RF receiver 11, a PN code demodulator 12, an arrival time measuring unit 13, and a processor 14 as shown in the accompanying drawings.

The RF receiver 10 has a function of demodulating QPSK by receiving an RF signal transmitted from a base station.

The PN code demodulator 12 includes 128 correlators. The reason why 128 correlators are required is to shorten the initial signal reception time and to sufficiently demodulate even if the reception strength is small during initial synchronization.

Each correlator attempts to capture signals with slightly different time differences. When different correlators pick up the same signal, the signal that arrives first is determined first, and the other correlators also induce the first signal to arrive. The terminal 10 distributes evenly so as to capture all the information of the neighbor base station list recorded in the auxiliary information which has received each correlator. Except for the signal that is received stably because the signal is strong, the base station with low signal strength will induce more stable correlators to be distributed later.

When the arrival time measurement unit 13 demodulates by the correlator to confirm the signal, the arrival time measurement unit 13 measures the arrival time by using a time measuring device provided thereon. The measurement standard is, for example, an internal clock of 200 msec. In the embodiment of the present invention, the visual measuring device must have a total of 20 or more and perform measurement on up to 20 received signals, and measure by 1 nsec unit to count up to 100 msec. Gin counters are used.

The processor 14 performs a procedure of calculating the position of the terminal 10 by mixing the measured arrival time information, the received delay time information, and the base station location information. The location calculation procedure first includes the location information of each base station. Since is an ECEF rectangular coordinate system, obtain the approximate plane equation closest to the base station received by the two-dimensional least squares method. Since most base stations do not coincide with the approximate plane, they are first projected on the approximate plane, and the X, Y second order of the approximate plane is used. Comprising an equation, first calculating my position first, using the approximate location information of my location, changing the measured length before projecting the base station to the approximate plane to the straight line after the projection, and performing position calculation once again And correct the information farthest from the mean of the measurement error to the mean of the measurement error. Compute phase.

Hereinafter, the method for calculating the position with the present invention will be described in more detail.

The base station location is represented by the Earth Centered Earth Fixed (ECEF) Cartesian coordinate system based on WGS-84 because it can be used without being limited to any one region.

However, when using this coordinate system, the altitude information part perpendicular to the base station arrangement is very error due to the base station arrangement characteristic located on the plane, so a method for excluding altitude information is needed. In order to eliminate the error as described above, it is necessary to assume a plane having a uniform altitude value of each base station, obtain the position of the terminal on the plane, and then convert the obtained terminal position back to the WGS84 rectangular coordinate system.

Position calculation is performed as follows.

1. Find the location emphasis of the receiving base stations.

When the center position = (X _oo , Y _oo , Z _oo )

2. Coordinate transformation is carried out with the midpoint as the origin, the north pole as the Y axis, and the far away from the origin as the Z axis.

Distance from the center of gravity to the new center

Distance when the upper straight line is projected on the X-Y plane

Angle from X axis to Y axis

Angle from Z axis to XY plane

New location value for each base station

The new coordinates obtained above are (X _oo , Y _oo , Z _oo ) as origins and are tangent to the earth's surface, with values in the coordinate system of the Y-axis and Z-axis in the north direction. (There is a difference between the Elipsoid ellipsoid and the perfect sphere, but it is not considered because it is a slight angle difference.) In this situation, since the base station is on the earth's surface, there is little difference in Z value and the calculation position of the terminal to be obtained Altitude value calculation is impossible, so all Z values are assumed to be "0" and TDOA calculation is performed with only XY value.

The location of the terminal determined by TDOA calculation

(X _po , Y _po , 0)

Will be converted to the original coordinate system.

As described above, the present invention can reduce the construction cost of each base station itself by constructing a location tracking signal transmission system by separating the main base station with a precise time synchronization device and the auxiliary base station system synchronized thereto. By making it possible to receive more remotely, the density of the base station can be reduced, and the base station maintenance-related information is also included in the transmission code, thereby eliminating the need for a communication line to the base station.

In addition, by adopting a terminal exclusively for reception, it is possible to prepare an instrument that reduces the size of the terminal to an extreme position, and has the advantage that it is not only effective as an independent positioning terminal but also easily solves a problem of location tracking during an emergency call.

Claims (9)

A time synchronization device having its own reference clock oscillator and synchronizing the time between base stations, an information storage unit for storing information to be transmitted as a position tracking signal, and accurately synchronizing the GPS time with the clock of the time synchronization unit. A base station consisting of a main station and a terminal station including means for modulating the position tracking signal of the information storage unit into a transmission signal and an RF transmitter for wirelessly transmitting the modulated signal through an antenna, and a position tracking signal transmitted by the base stations A downlink location tracking system of a location tracking terminal consisting of a terminal receiving a signal and measuring a difference in arrival time of each received signal based on its own clock and calculating its location using the measured value. According to claim 1, wherein the time synchronization unit of the main station GPS receiver for generating time information synchronized to the GPS time and a clock unit of 1 [pulse / second], cesium oscillator for generating a precise signal of 10 ^-13 or more by itself Downlink location tracking system of a location tracking terminal, comprising a comparator for measuring the time difference between the GPS signal and the cesium oscillation period and adjusting the cesium oscillator to remove the error when an error of 100 nsec or more occurs. . According to claim 1 or claim 2, wherein the time synchronization unit of the terminal station, the main station signal receiver for generating time information and reference clock synchronized with the main station signal, the rubidium oscillator for generating a precise signal itself, the periodic station signal A downlink type location tracking system of a location tracking terminal, comprising a comparator for measuring a time difference between a receiver and a rubidium oscillation period and adjusting a rubidium oscillator to remove an error when an error exceeding a reference value occurs. According to claim 1, wherein the location tracking signal transmitted from the base station and the terminal station is the time delay information on the base station specific PN code, the main information consisting of the time value and the main station group number, the location information of the base station, the base station A downlink type location tracking system of a location tracking terminal, comprising auxiliary information including PN code information and location information of neighboring base stations. 5. The PN code number according to claim 4, wherein the PN code numbers are assigned with lower PN numbers from 0 to 511 and higher PN numbers from 512 to 1023 per base station group, and each base station is assigned from a lower PN number and a higher PN number. Two PN numbers, each with a 512 number difference between PNs, are assigned to each other, while the lower PN number is used for transmitting main information and the higher PN number is used for transmitting auxiliary information. Downlink location tracking system of a location tracking terminal. [5] The system of claim 4, wherein the main information further includes base station health information indicating a health state of the base station so that a separate management line can be removed. The method of claim 1, wherein the means for modulating the position tracking signal into a transmission signal is performed by a CDMA method, and the PN (Pseudo Noise) code frame is synchronized with the clock of the cesium oscillator in the case of the main station, and the terminal station. A downlink location tracking system of a location tracking terminal, wherein the clock error of the cesium oscillator and the rubidium oscillation period is synchronized with the clock of the rubidium oscillator and included in the PN code to provide information. 2. The terminal of claim 1, wherein the terminal includes a PN code demodulation unit having 128 correlators so as to sufficiently demodulate even if the initial signal reception time is shortened and the initial reception strength is small. Downlink location tracking system of the terminal. Transmitting the position tracking signal synchronized with the GPS time at the main station and the terminal station at the terminal station, and receiving the position tracking signal at the terminal to obtain the position center points of the receiving base stations; Obtaining a new position value of each base station by performing a coordinate transformation using the Y-axis direction and the Z-axis direction away from the origin, assuming that all Z values are "0" in the converted new position value, only XY values And calculating the location of the terminal by converting it to the original coordinate system after performing the TDOA calculation to the terminal location calculation method of the downlink location tracking system of the location tracking terminal.