KR20020092718A - GPS Receiver and Method for Determining Position of a Wireless Terminal - Google Patents

Abstract

PURPOSE: A method for measuring positions of a GPS(Global Positioning System) terminal and a wireless communication terminal are provided to reduce a time for obtaining a measuring value and increase receiving sensitivity of a GPS signal by reducing a code search range. CONSTITUTION: A communication link is set up between a base station(2) and a modem of a terminal(100). A position measuring command is transmitted to the terminal(102). The terminal receives a GPS signal and stores an IF sampling signal into a snap shot memory(104). The base station(2) prepares auxiliary information for measuring a position of the terminal(106). The base station(2) transmits the auxiliary information to the modem of the terminal and a microprocessor of a GPS receiver by using a serial communication method(108). The GPS receiver processes IF sampling signals to calculate pseudo distances of satellites(110). The microprocessor calculates the position of the terminal and transmits the calculated result to the base station(112,114).

Description

GPS Receiver and Method for Determining Position of a Wireless Terminal

The present invention relates to a positioning system and method, and more particularly, to a GPS receiver and a positioning method for positioning using a GPS signal in support of a wireless communication network.

The use of positioning systems to measure the position of antibodies is increasing in various fields. Representative of such a positioning system may be called a global positioning system (GPS). In GPS, the source signals for positioning are provided by satellites floating about 20,200 km from the earth, and each receiver receives signals from four or more satellites within the gaze range of the satellites and calculates its position. Done. The GPS receiver calculates the time delay and Doppler shift of the signal received from each satellite to calculate the distance and rate of change of distance between the satellite and the receiver, and obtains the satellite position and speed from the navigation data obtained by demodulating the received signal. In this way, information about four or more satellites can be used to determine the position and velocity of the receiver.

The GPS signal has a form in which 50 Hz navigation data is spread by a satellite-specific pseudo noise code and then modulated by a BPSK method to a carrier signal of about 1.5 GHz. Therefore, in order to acquire GPS signals and demodulate data in a receiver, codes and carriers need to be removed. To remove the carrier, it is necessary to find Doppler information on the magnitude and direction of the Doppler shift. In general, the Doppler shift generates a maximum of 5 kHz due to the movement of the satellite when the receiver is in a stationary state. Such Doppler information is generally calculated using a method of searching for a signal at regular intervals. Meanwhile, codes mixed with GPS signals are divided into C / A codes that can be received by civilians and P (Precision) codes, which are military signals, and different codes are multiplied by satellites. The process of removing the code is performed simultaneously with the Doppler search by generating the same code in the receiver and convolutional.

After both the code and the carrier are removed, data extraction is possible. In GPS data, five subframes form one frame and 25 frames form a superframe. Since subframes 1, 2, and 3 of the data have values related to the time and position of the satellite being transmitted, each satellite has different values. Subframes 4 and 5 have information about all satellites, and each satellite has the same values. have. Through the above process, three to four or more satellite data are demodulated to acquire satellite positions and measurements, and then positioning is possible.

Meanwhile, the demand for a positioning system for measuring the position of wireless communication terminals using a wireless communication network is increasing day by day. The urgent need for wireless communication network based positioning system is emergency rescue service. In this regard, the Federal Communications Commission (FCC), in a regulation adopted on 12 June 1996, requires all carriers of wireless telecommunications service systems, including cellular systems and PCS, to verify credit for emergency rescue requests from wireless terminals. Immediately send a call to the Public Safety Answering Point (PSAP) without performing the certification process, and by 2001, with the accuracy of about 50m for 67% of all emergency rescue calls and 150m for 95%. It was required to provide the location information of the terminal. Since the announcement of the regulations, the research on the wireless network-based positioning system has attracted great attention.

The positioning system using the wireless communication network uses the following three methods, the positioning method using only the network system, the positioning method using only the GPS, and the hybrid method using both the GPS and the network system to determine the position of the wireless terminal. .

A method using only a network system is a geolocation method for positioning by a triangulation method using a plurality of base stations, and may be divided into a remote positioning method and a self positioning method. In the remote positioning method, a signal transmitted from a terminal is received at various base stations to finally obtain a location at a central site. This method has the advantage that it can be implemented without greatly changing the structure of the terminal, but there is a disadvantage that the structure of the network equipment must be changed and the terminal does not know its location. In the self positioning method, each terminal performs positioning based on signals from various base stations. This method can be implemented by reinforcing only the terminal without significantly changing the existing network equipment, and has the advantage of wide application range by knowing its position in the terminal, whereas audibility among neighboring base stations If there are not many high base stations, positioning is impossible and there is a high possibility of providing a large position solution due to non line of sight (NLOS) errors.

On the other hand, according to the method of positioning using only GPS, the wireless terminal transmits the data measured by the GPS receiver circuit or the device to the central control station through the wireless communication network to the engine. This method has the advantage that it can be implemented without significantly changing the existing network system, while the two systems are mixed in the terminal, which consumes a lot of power and has disadvantages such as interference between the two frequencies. There is a problem that it is impossible to measure the position of the terminal. In addition, the initial position acquisition time is about 1 minute in the receiver that performs positioning using only GPS. This initial position acquisition time is not a problem in general navigation system applications, but it is too long in an emergency situation such as an emergency rescue request. It is a problem.

Hybrid method compensates for each other's shortcomings by mixing positioning method using only network system and positioning method using GPS only. The method of positioning by GPS. However, this method still has the problem of complicated terminal structure and high power consumption.

In order to solve these problems, in recent years, attention has been focused on network-assisted GPS (GPS) positioning techniques, which perform positioning based on GPS signals, but under the assistance of a communication network, that is, a base station and a terminal share a role. have. According to the network-assisted GPS positioning technique, the base station transmits auxiliary information necessary for improving the GPS positioning speed to the terminal through the wireless communication network, and the terminal uses the assistance information to obtain the pseudo distance for each satellite. The auxiliary information provided to the terminal by the base station may include satellite position and Doppler information at a positioning time. The terminal performs direct positioning using the pseudoranges calculated for each satellite and then transmits the positioning data to the central control station, or provides the pseudoranges to the base station so that the base station, the switching center or the central control station can perform the positioning. According to the network-assisted GPS positioning technique, not only can the positioning time be shortened, but also the positioning can be performed indoors with low signal sensitivity, and the positioning accuracy can be improved compared to the positioning system using only the network system.

There are three major researches on the Network Assisted GPS positioning technique. The first is to reduce the signal acquisition and positioning time in the GPS receiver included in the terminal by providing appropriate auxiliary information from the base station to the terminal using a wireless communication network, and the second is the reception of the GPS signal so that the positioning can be performed indoors. The third is to increase sensitivity, and the third is to reduce power consumption of the system.

In order to reduce the time to first fix (TTFF), satellite position and Doppler information must be known, which can be calculated from satellite Ephemeris data and GPS time, and Doppler information can be obtained from satellite and terminal speeds and receivers. Knowing the local oscillator clock drift can be done. Therefore, in the conventional Network Assisted GPS positioning technique, the base station provides time information, frequency information, and Doppler information to the terminal as auxiliary information.

The time information is to synchronize the positioning reference time between the base station and the terminal. The time information is a basic auxiliary information in the network-assisted GPS positioning technique. The terminal modem obtains the satellite position by providing the terminal time information synchronized with the base station in the GPS receiver. It can be used to reduce the search range to find the code offset. If the base station provides precise carrier frequency information, it can compensate for the clock drift of the GPS receiver local oscillator. It is described. On the other hand, an example in which the base station provides Doppler information on the visible satellite is described in US Patent No. 5,663, 734 and US Patent No. 5,781, 156 granted to SnapTrack, Inc.

Meanwhile, in order to enable indoor positioning using a GPS receiver, reception sensitivity should be increased. In order to increase the reception sensitivity of the GPS signal, as described above, the base station provides frequency information and the like with the terminal, and the terminal performs a plurality of convolutional operations or fast Fourier transform operations in tracking and demodulating the signal. It has been suggested. For example, US Pat. Nos. 5,663,734 and 5,781,156, and US Pat. No. 5,884,214, assigned to SnapTrack, describe a process of tracking and demodulating a signal by performing multiple convolution or fast Fourier transform operations. In addition, one of the typical methods for increasing reception sensitivity is to increase the signal integration time as described in US Patent No. 5,884,214. However, since the GPS signal contains 50Hz of data, it is impossible to integrate more than 20msec when the data information is not known, and the integration time limit is further increased when there is an error in the estimated Doppler. There are two main technologies to solve this problem. First, the receiver clock drift is compensated for by using a precise carrier signal of the base station 2. Secondly, in order to prevent signal attenuation due to Doppler error, the signal is integrated by dividing it several times in short periods and then re-integrated only magnitude, or estimated by searching for Doppler error.

As a method for reducing power consumption of a terminal having a Network Assisted GPS positioning function, for example, U.S. Patent Nos. 5,663,734 and 5,781,156 provide power to the RF signal input terminal and the snapshot memory only during GPS signal reception, and process IF data. The circuit is described so that power is supplied to the digital signal processor (DSP) only in the process, and power is not supplied to these members when positioning is unnecessary or at other stages of the positioning process.

The present invention is to provide a positioning method that can further reduce the measurement acquisition time, and can substantially increase the GPS signal reception sensitivity of the terminal.

1 is a view showing a preferred embodiment of a GPS terminal according to the present invention.

FIG. 2 is a flowchart showing a self positioning process in the GPS terminal of FIG. 1. FIG.

3 is a flowchart showing a remote positioning process in the GPS terminal of FIG.

4 is a flowchart illustrating a process of processing an IF sampling signal illustrated in FIG. 2 in more detail.

5 is a waveform diagram showing a configuration of a general GPS signal.

6 is a waveform diagram showing a process of removing carrier and navigation data from a GPS signal.

7 conceptually illustrates a process of coherent integration of a received C / A code.

8 conceptually illustrates reducing the code search range based on the estimation of the time delay threshold in the present invention.

9 is a view for explaining a process of interpolating correlation values for viewpoints between each sampling viewpoint to determine a viewpoint having the highest correlation value.

10 is a view for explaining the positioning assistance information provided by the base station and its use in the positioning method of the present invention.

11 is a view illustrating a search range calculation method for calculating a pseudo distance between a satellite and a terminal.

12 is a diagram illustrating a search method when pseudo range information is provided from a base station.

13 is a diagram illustrating an example of RTD statistics collected at a base station.

FIG. 14 is a diagram illustrating a search range for obtaining a second satellite signal in a positioning method using a pseudorange calculated first with respect to another satellite.

FIG. 15 is a diagram illustrating a search range for acquiring a third satellite signal in the positioning method using the pseudorange calculated first with respect to another satellite.

Fig. 16 is a diagram showing a search range in the embodiment utilizing sector information.

17 is a diagram illustrating a state in which a terminal can receive signals from two base stations.

18 is a view showing a position error range when using two or more base stations.

In the positioning method of the present invention for achieving the above technical problem, navigation data is provided along with pseudo distance and time information for the base station to the auxiliary information provided to the terminal through the wireless communication network. Accordingly, the terminal does not need to consider the bit phase change by the navigation data when extracting the C / A code from the GPS signal, and can increase the integration time to the frequency of the navigation data, that is, 20 msec or more, and process the same size data. This saves time by reducing the number of processing times. In addition, in the positioning method of the present invention, the information on the cell coverage of the base station communicating with the receiver is included in the auxiliary information. In this case, a Round Trip Delay (RTD) and / or sector information and repeater information between the base station and the terminal may be included. The base station can reduce the amount of computation by reducing the code search range during the positioning process to shorten the measurement acquisition time and increase the reception sensitivity.

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

1 shows a preferred embodiment of a GPS terminal for implementing a positioning method according to the present invention. The GPS terminal 10 of FIG. 1 includes a radio signal transmission / reception modem 12, an antenna for radio signal transmission and reception 14, and a GPS receiver 20, which is abbreviated as “base station”. And receive and receive GPS signals from GPS satellites.

In the preferred embodiment, the base station 2, as part of the CDMA communication network, provides communication services for terminals located within the cell coverage. In particular, in the present invention, the base station transceiver subsystem (BTS) of the base station 2 includes a GPS receiver, and generates positioning assistance information to be provided to the terminal 10 while performing continuous navigation solutions. Save and update continuously. When transmitting a positioning start request command to the terminal 10 or receiving a positioning start request from the terminal 10, the base station 2 provides the positioning assistance information to the terminal 10 so that the terminal 10 receives the assistance information. It allows for quick positioning and easy positioning. Positioning assistance information used in the present invention will be described later.

In Fig. 1, a radio signal transmission / reception modem 12 (hereinafter, abbreviated as " modem ") modulates an uplink communication signal into a CDMA signal, transmits it to the base station 2, and demodulates the CDMA signal from the base station. The modem 12 and the GPS receiver 20 are connected via serial I / O. When receiving the positioning command from the base station or when the positioning command is applied by the user or by the operation of a program loaded in the terminal, the GPS receiver 20 receives the positioning assistance information provided by the base station 2 through the modem 12. It accepts the GPS signal from the GPS satellites and uses the positioning assistance information and the GPS signal to determine the position of the terminal.

In a preferred embodiment, the GPS terminal 10 is manufactured in such a manner that the GPS receiver 20 and the modem 12 are integrated in one housing. However, in another embodiment of the present invention, the GPS receiver 20 may be manufactured separately and connected to the modem 12 in the wireless communication terminal through the serial interface port of the wireless communication terminal. The wireless communication terminal may be, for example, a cellular telephone or a PDA.

In the embodiment of FIG. 1, the GPS receiver 20 includes a microprocessor 22, a power controller 24, a frequency synthesizer 26, an antenna 28, a down converter 30, and an analog / digital converter. 32, a snapshot memory 34, and a digital signal processor 36.

The microprocessor 22 performs data transmission and reception with the modem 12 and performs a power control function for each part within the GPS receiver 20. That is, the microprocessor 22 controls the power control unit 24, and in the normal state, the microprocessor 22 controls the down converter 30, the analog / digital converter 32, the snapshot memory 34, and the digital signal processor 36. Ensure that no power is supplied or only minimal standby power is supplied and that full power is supplied to them only at some stage of the positioning process.

While the positioning is not performed, the down converter 30, analog / digital converter 32, snapshot memory 34, and digital signal processor 36 are in a low power standby state. In this state, when the positioning is started, complete power is first supplied to the down converter 30, the analog / digital converter 32, and the snapshot memory 34. FIG. The down conversion unit 30 receives the GPS signal of the RF band received through the antenna 28 and down converts the frequency band of the GPS signal into the IF band using the local oscillation signal from the frequency synthesizer 26. The analog / digital converter 32 samples and quantizes the IF signal from the downconverter 30 using a sampling clock from the frequency synthesizer 26 (hereinafter, referred to as "IF sampling signal"). "," Is stored in the snapshot memory 34. In this manner, only the standby power is supplied to the digital signal processor 36 in the process of the GPS signal being sampled and stored in the snapshot memory 34.

On the other hand, when the storage of the IF sampling signal in the snapshot memory 34 is completed, the down-converter 30 and the analog-to-digital converter 32 is switched to a low power standby state, the digital together with the snapshot memory 34 The signal processor 36 begins to be supplied with complete power for operation. The digital signal processor 36 calculates a pseudo distance for each of the visible satellites using the IF sampling signal stored in the snapshot memory 34 and the auxiliary information received from the base station 2 via the microcontroller 22. do. To this end, the digital signal processor 36 is programmed to obtain a pseudo distance.

After completing the pseudorange calculation for each of the visible satellites, the digital signal processor 36 provides the pseudorange information to the microprocessor 22. Upon receiving the pseudorange information, the microprocessor 22 again controls the power controller 24 to cause the snapshot memory 34 and the digital signal processor 36 to enter a low power standby state. The microprocessor 22 then processes the pseudorange information in accordance with the mode of operation. That is, in the self-positioning mode in which the terminal directly determines its own position, the microprocessor 22 determines the terminal position using pseudo range information, and then displays the terminal position data on the display of the terminal or on the base station 2. send. On the other hand, in the remote positioning mode in which a separate central control station determines the terminal position, the microprocessor 22 transmits pseudorange information to the central control station via the base station 2 so that the central control station finally obtains the terminal position. Done.

The hardware structure of the GPS terminal shown in FIG. 1 can be said to be similar to that shown in US Pat. Nos. 5,663,734 and 5,781,156. However, in contrast to US Pat. Nos. 5,663,734 and 5,781,156, the types of positioning assistance information received from the base station 2 are different in the GPS terminal of FIG. 1, and in particular, the base station acquires the information as described above. Navigation data and data such as the cell coverage range of the base station, that is, the effective range and / or the path reciprocal delay time (RTD) between the base station and the terminal are added. Accordingly, as described in detail below, the positioning method performed by the GPS terminal is different from the above-described US patents.

FIG. 2 schematically illustrates a positioning method in the GPS terminal of FIG. 1.

First, for positioning, a communication link must be established between the base station 2 and the modem 12 of the terminal 10 (step 100). After the communication link is established, the terminal 10 corrects the time error using a signal transmitted from the base station 2 according to a predetermined protocol in the communication network. In addition, the frequency synthesizer 26 of the GPS receiver 20 in the communication link is established to share the clock with the terminal modem 12, thereby minimizing the clock drift error and thereby the Doppler shift.

In this state, when the communication link is established, the base station 2 may transmit a positioning start command to the terminal 10 when it is desired to know the location of the terminal 10 (step 102). The positioning start command may designate a specific time so that positioning may be performed at the designated time, or may be performed immediately. Upon receiving the positioning start command, the terminal 10 transmits a confirmation signal to the base station 2. In addition, when a specific time is specified in the positioning start command, the terminal 10 transmits a positioning start notification signal to the base station 2 at that time. Meanwhile, the terminal 10 may request the base station 2 to start positioning. In this case, the base station 2 receiving the request transmits a positioning start notification signal to the base station 2 to the terminal 10.

Subsequently, the terminal 10 receives the GPS signal and stores the IF sampling signal in the snapshot memory 34 (step 104). At the same time, the base station 2 prepares positioning assistance information for the terminal 10 (step 106). The auxiliary information provided by the base station 2 is transmitted to the modem 12 of the terminal 10, and then transmitted to the microprocessor 22 of the GPS receiver 20 by serial communication (step 108). In a preferred embodiment, the auxiliary information used by the GPS receiver 20 of the terminal 10 for positioning includes those provided by the base station 2 and those calculated in advance, and the types of the auxiliary information are shown in Table 1 below. It is arranged.

Auxiliary Information Type Usage Provided by the base station Satellite code (SV_ID) Select a satellite to handle the signal Distance between satellite and base station (?? _BS ) Initial value of terminal pseudorange for the satellite Satellite Trajectory (Ephemeris) Doppler shift calculation for that satellite Navigation data Remove navigation data from signals collected from the terminal Time information Satellite positioning time setting Positioning time setting Terminal pseudo distance calculation reference time setting Base Station Effective Range (R _BS ) Calculate code search scope Route Round Trip Latency (RTD) Reduced code search range Time Error Correction According to Distance between Base Station and Terminal Knowing in advance Terminal Clock Error Calculate code search scope Base Station Clock Error Calculate code search scope

Meanwhile, in order to reduce the code search range, cell coverage, that is, base station effective range ( Instead of or in conjunction with the repeater coverage ( ) Data may be provided. In addition, sector information may be included in the positioning assistance information. In addition, the location assistance information may include information on the location of the base station (or repeater) communicating with the terminal and whether the communication counterpart is a base station or a repeater. In particular, the effective range R of the base station when the information on the repeater is not known or the repeater is not used is the base station effective range ( It can have a different value from).

After the IF sampling signals are collected in steps 106 and 108 and the positioning assistance information is received from the base station 2, the GPS receiver 20 of the terminal processes the IF sampling signals to inquire about all or some of the visible satellites. The distance is calculated (step 110). When the pseudorange calculation is completed, the microprocessor 22 calculates the position of the terminal from the pseudoranges and the satellite Ephemeris data for the plurality of visible satellites and transmits the position of the terminal to the base station 2 (steps 112 and 114). ). On the other hand, Figure 2 illustrates the case of self-positioning, in the case of remote positioning, the calculated central distance information is transmitted to the central control station via the base station 2, the central control station finally calculates the position of the terminal Will be done. This remote positioning process is shown in FIG. 3.

4 illustrates the IF sampling signal processing process illustrated in FIG. 2, that is, step 110 in more detail. Referring to the process illustrated in FIG. 4 schematically, first, a C / A code for one visible satellite is generated (step 150). In general, a C / A code is a Pseudo Noise (PN) code with a frequency of 1 megahertz (MHz) and repeated every 1 millisecond (msec), that is, every 1023 bits. In step 150, such a C / A code is generated by a PN code generator in the digital signal processor 36. However, in another embodiment in which the present embodiment is modified, C / A code may be read and used from a lookup table loaded into memory. After the C / A code is generated, the C / A code (hereinafter referred to as "received C / A code") included in the received GPS signal is recovered from the IF sampling signal stored in the snapshot memory 34. Integrate to coherent (step 154). In addition, by matching the timing between the generated C / A code and the integrated C / A code with reference to the time-tag attached to the navigation data bits received from the base station 2, the pseudo delay is calculated by calculating the code delay time between the two codes. The distance is determined (steps 156 to 168).

Steps 154 to 168 will be described in detail.

In general, the GPS signal includes a navigation data, a C / A code, and a carrier as shown in FIG. 5, and has a waveform in which the phase of the carrier is inverted when the navigation data or the C / A code transitions to a logic state. The basic principle of calculating the pseudorange using the GPS signal is to calculate the delay time of the C / A code included in the GPS signal, and the carrier must be removed first. In general, when removing a carrier, it is necessary to take into account the bit phase change caused by the navigation data. That is, when navigation data having a frequency of 50 Hz remains, in the coherent integration process of step 154, the integration time cannot be extended to 20 ms or more, thereby increasing the reception sensitivity through integration.

However, in the terminal of Fig. 1, since the digital signal processing unit 36 receives the navigation data from the base station 2 via the modem 12 and the microprocessor 22, the GPS signal, i. Along with the carrier, navigation data is also removed from the IF sampling signal. After the navigation data is removed in this way, it can be easily confirmed from FIG. 6 that the C / A codes are all in the same phase. Accordingly, it is not necessary to consider the bit phase change due to the navigation data, and the integration time can be increased to 20 msec or more, and the processing frequency can be reduced when processing the same size data, thereby saving time. For example, when processing 1 second data, 100 blocks are generated when dividing by 10 msec unit, and 10 blocks are generated when dividing by 100 msec unit. Therefore, the calculation time is 1/10 when dividing by 100 msec, compared to dividing by 10 msec unit. Decreases. Meanwhile, in removing the carrier, the Doppler shift is also removed. A method of removing the Doppler shift can be easily implemented by those skilled in the art to which the present invention pertains, and thus a detailed description thereof will be omitted.

Removing the navigation data and the carrier from the GPS signal leaves only the received C / A code. Therefore, the code delay time can be calculated by identifying the correlation with the C / A code generated by the convolution. Here, instead of directly convolving the received C / A code to increase reception sensitivity, the correlation between the integrated received C / A code and the generated C / A code is obtained by coherently integrating the received C / A code. Figure out. 7 conceptually illustrates a process of coherent integration of a received C / A code. As shown, in the preferred embodiment of the present invention, the received C / A code is divided into units of one cycle and then added thereto. If the GPS memory of one second is stored in the snapshot memory 34, 1000 cycles of C / A code may be added during the coherent integration process, so that the C / A code has an amplitude 1000 times greater than before integration. (Step 154). The reception sensitivity is substantially improved because convolution is performed using the signal having such a large size. It should be noted that one pulse in the C / A code shown in FIGS. 5 to 7 is a simplified representation of one cycle of the C / A code.

Referring back to FIG. 4, in step 156, a timing is calculated and a search range is determined to obtain a correlation value by using the integrated C / A code and the generated C / A code. The technique finds the correlation peak while searching the C / A code, and noncoherently integrates the correlation values (steps 158 and 160). Steps 152 to 160 are repeated until the search is completed for the search area (step 162).

In this case, if a general convolution technique is used, the entire range of C / A codes should be searched. However, in the present invention, a time delay search is performed by using a pseudo distance provided by the base station 2 (or RTD information or sector information together). The range can be greatly reduced, and thus time delay can be calculated quickly. For example, if the time delay limit value can be estimated based on the positioning assistance information as shown in FIG. 8, the actual expected time delay will be within the limit value range, and the code search will be sufficient within this range. In the present invention, the time delay limit is calculated based on the RTD, the sector information of the corresponding cell, the base station pseudo-distance, and the like, and the search range is reduced based on this. A detailed method thereof will be described below.

On the other hand, if it is determined in step 162 that the search has been completed for the entire search area, the pseudo range is determined. In this case, since the resolution is determined according to the sample frequency, the calculated time delay value causes a large positioning error due to the resolution. In order to solve this problem, as shown in FIG. 9, the correlation values are interpolated with respect to the time points between each sampling time point to determine the time point having the highest correlation value, and the pseudo distance corresponding thereto is determined. (Steps 164 and 166). On the other hand, steps 150 to 166 are sequentially performed for each of the all visible satellites to be used for positioning (step 168).

Generation and transmission of navigation data at base station

The key to providing navigation data in the base station 2 and using this data as positioning assistance information in the terminal 10 is time synchronization. That is, when the time synchronization is not correct when applying the navigation data obtained by the base station 2 to the IF signal collected by the terminal 10, signal loss is caused. Therefore, the time when the terminal 10 collects the IF data and the time when the base station 2 collects the navigation data must match. In order to match the data collection time as described above, in the present invention, the navigation data bits collected by the base station 2 are time-tagged and transmitted to the terminal 10, and the terminal 10 refers to the time-tag and the IF signal. The timing is matched with the collected time.

Generally, there is a phase difference in the navigation data bits received from each satellite at the same time. This is because the distance from the GPS receiver to each satellite is different. Therefore, when the terminal 10 uses the navigation data, the terminal 10 first calculates the bit phase at the start of navigation data collection. The base station 2 has the time at which the navigation data bits are collected and the pseudorange information for each satellite. The pseudorange for each satellite is the difference between the time at which the signal is received and the time sent by the satellite. The time when the satellite sends the satellite signal can be obtained as in Equation 1 below.

In Equation 1 Is the time when the i-th satellite sent the satellite signal, Signal reception time, Denotes the pseudo distance between the i-th satellite and the base station, respectively. On the other hand, since the satellite signal is transmitted in synchronization with GPS time, it is possible to detect the bit phase from the sent time, the bit phase is as follows.

In equation (2) Is an error occurring between the base station 2 clock and the GPS time.

The bit phase calculated by Equation 2 is calculated based on the base station 2, and includes the time synchronization error generated by the distance difference when used in the terminal 10 as it is. Accordingly, in the present invention, the error can be reduced by using the RTD information. Accordingly, the bit phase information applicable to the terminal 10 is as follows.

In equation (3) Denotes MS and BS clock error.

Code Search Range with RTD

In order to find the position of the terminal, the distance between each satellite and the terminal must be obtained. In order to obtain the distance between the satellite and the terminal, carrier and code acquisition and tracking of the satellite signal must be preceded. As described above, the principle of obtaining a code in GPS is to convolve the signal from the satellite and the signal generated by the receiver during the code period. If no separate information is provided from the base station, the entire range of the signal corresponding to 1 msec, which is the C / A code period of the GPS signal, needs to be searched. In this case, one cycle consists of m samples to calculate a correlation value. Suppose that we need to add and multiply 2m ² . However, in the present invention, the auxiliary information including the RTD is provided at the base station when the terminal acquires the signal, thereby greatly reducing the code search time.

10 is a view for explaining the positioning assistance information provided by the base station and its use in the positioning method of the present invention. In the figure, SV1 to SV3 represent satellites, BS represents a base station, Repeater1 to Repeater3 represent a repeater, and MS1 to MS4 represent terminals. Meanwhile, Is the pseudorange between the satellite and the base station, Is the pseudorange between the satellite and the terminal, Is the effective range of the base station, Is the effective range of the repeater, R is the effective range of the base station when the information on the repeater is not known, Represents the distance corresponding to RTD, respectively.

Pseudorange calculated from the base station ( Use of):

When the pseudorange calculated at the base station is provided to the terminal, it is not necessary to search the entire cycle of the C / A code. That is, the terminal is adjacent to the base station with which communication Wow Does not make a big difference. Therefore, without searching from the beginning of the C / A code You only need to search for a part based on. At this time, the search range is determined by the distance difference between the terminal and the base station and the time synchronization difference between the two systems. 11 is A diagram for describing a search range calculation method for calculation. In the drawing, Denotes the elevation angle of the satellite with respect to the base station. Here, the maximum pseudo-range error caused by the distance difference between the base station and the terminal is the effective range of the base station ( ) Is orthogonal to the vector direction from the base station to the satellite, Becomes In this case, the search reference point It is calculated from the C / A code phase can be calculated by the following equation (1).

here Is a function that calculates values below the decimal point, Is the wavelength of the C / A code and C is the luminous flux. Search range is Can be calculated from the time synchronization error generated between the two systems, and the C / A code phase at the terminal 10 Has the following range:

here, Represents the time synchronization error occurring between the two systems. 12 illustrates a search method when pseudo range information is provided from a base station. In the code search as shown, the search reference point ( ), The integrated C / A code and the generated C / A code are convolved within the range shown in Equation 5 above.

On the other hand, if a repeater is installed in the cell coverage of the base station 2 and the terminal does not know through which repeater the signal is received, the effective range of the base station 2 is determined. It is preferable to use R shown in FIG. 10 instead. In this case, R As it is larger, the search range is increased.

Use of distance information corresponding to RTD:

RTD is information reflecting the distance between the base station and the terminal can be obtained or easily obtained from the base station. When the terminal receives the RTD or the distance information corresponding to the RTD, the search range is further reduced. That is, instead of searching the entire base station effective range of FIG. Since only the inside needs to be searched, the search range at this time is as shown in Equation 6.

On the other hand, the signal passing through the repeater has a larger RTD value than the signal not passing through the repeater. Here, when a plurality of repeaters are installed in the cell coverage, it is possible to know which repeater the link is passing through using the RTD statistics. 13 shows an example of statistics of RTD information collected by a base station. In the case of the signal passing through the repeater, pseudorange information based on the repeater position ( ) And elevation information ( ) And repeater coverage ( ) Value, the search base point ( ) Should be calculated. The search reference point and the search range of the signal passing through the repeater may be represented by Equations 7 and 8 below.

Where repeater coverage ( ) Is the time delay between the RTD information and the fiber ) Can be simply approximated as follows.

Use of pseudoranges calculated first for other satellites:

When calculating the pseudoranges of the first satellite and then calculating the pseudoranges of the second and subsequent satellites, the search range can be further reduced in the satellite signal acquisition process by using the pseudorange information calculated first for the other satellites. In such an embodiment, if the pseudorange for the first satellite is obtained, the base station pseudorange ( ) And terminal pseudoranges ( ) To determine whether the terminal is far or near to the base station and limit the search range based on the determination result.

FIG. 14 shows a search range for second satellite signal acquisition in the positioning method using the pseudorange calculated first with respect to another satellite. In FIG. 14, the first satellite SV1 and the second satellite SV2 are projected and displayed in a two-dimensional plane centered on a base station. In the drawings, Is the i-th point, Is the azimuth of the i-th point, Is the pseudorange between the j-th satellite and the base station, Is the orthographic point of the j-th satellite, Is the azimuth of the i-th satellite, Represents the elevation angle of the j-th satellite, respectively.

In Figure 14 this Assuming smaller, the terminal is in the semicircle (the shaded area) closer to the first satellite SV1 of the base station effective range, and thus the shaded semicircle portion when acquiring the second satellite (SV2) signal. You only need to search. In this case, the search range varies depending on the position of the second satellite SV2, but the maximum and minimum values of the pseudoranges can be obtained separately in the semicircle. The maximum and minimum values are a straight line that divides the circle into two semicircles and two points where the circle intersects ( , ), The intersection of the line of sight and the circle of the second satellite (SV2) ( ), And the base station location as the center point ( ) Therefore, four points from SV2 ( To After calculating the distance to), you can find the maximum and minimum values by comparing the sizes. The distance from the satellite position to each point can be obtained by Equation 10.

The search range is the maximum value of the distances obtained by ) And minimum value ( It is determined by), and can be represented by the following equation (11).

In this way, after finding the pseudorange of the second satellite, we only need to search for the reduced part when acquiring the third satellite signal. The search range for the third satellite signal acquisition is shown in FIG. 15. In the example of Fig. 15, four points (from SV3) To The maximum and minimum values of the search range can be obtained by calculating the distances to) and comparing the magnitudes. When searching for the fourth satellite signal continuously, the search range can be further reduced in the same manner. Using this approach to reduce the search range not only reduces the computational complexity, but also reduces the likelihood of incorrectly estimating the C / A code phase due to noise.

Use of sector information:

Sector information is another information that can be utilized as positioning assistance information in the base station. In general, three sectors exist in one base station. In the present embodiment, the search range is further reduced by utilizing sector information. The method of defining the search range using the sector information according to the present embodiment is similar to the method using the previously calculated pseudo distance described above, and the search range in this case is shown in FIG.

If sector information is used, the search range can be reduced from the first satellite signal search. In the example of FIG. 16, where the terminal solution may be, the inside of the gray fan shape. The maximum and minimum values are the intersections of two straight lines and circles ( , ), The intersection point of the satellite's line of sight and the circle ( ) And the base station location (the center point) ), So that the maximum and minimum values of the search range can be obtained by comparing the magnitudes of the distances from the satellite to four points. In this case, when the sector information is used, a signal can be obtained more effectively by searching for the intersecting range from the second satellite, taking into account the pseudo distance calculated first with respect to the other satellite.

Reduction of correlation value search range using two or more base stations

In the above description, the case where the terminal communicates with one base station is used to reduce the search range by using the RTD. By the way, it can be seen that, the larger the RTD value was confirmed that the search range increases. In this case, when the terminal 10 is far from the base station in communication, the distance from the other base station may be close, so the possibility of communication with the other base station is increased, and thus the extra measurement value may be obtained and used. That is, when the signal can be received from two or more base stations as shown in FIG. 17, the C / A code search range can be further reduced. However, the position obtained in such a case may include errors due to non line-of-sight (NLOS) path propagation or multipath effect, and provide a solution represented by a rectangle in FIG. 17 as another solution. do.

If you have two base stations:

In FIG. 17, assuming that the terminal MS belongs to the base station 1 BS1 and knows the RTD between the base station 1 BS1 and the terminal MS, between the base station 1 BS1 and the terminal MS. Street( ) And the distance between BS2 and MS ) Are as follows.

Here, C denotes a luminous flux, t _PNoffseti denotes a PN code offset set differently for each base station, and ?? denotes a correlation delay time between the base station 1 (BS1) and the base station 1 (BS2).

If the position of the terminal is (x, y, z), the position of the base station 1 (BS1) is (x ₁ , y ₁ , z ₁ ), and the position of the base station 2 (BS2) is (x ₂ , y ₂ , z ₂ ) The measurement equation for the distance is as follows.

here, It consists of measurement noise and NLOS error. The error of the second measurement is included in the error of the first measurement. Since there are only two equations, you cannot obtain a three-dimensional position, but assuming you know the altitude, you can add

From here, Is the square of the altitude error. In Equation 14, it is assumed that the altitude is known. Includes the error. Equation 13 may be modified as follows.

here, Represents the distance from the center of the earth to the i-th base station BSi, and does not include an error since the location of each base station is accurately known.

Now, x and y can be expressed as a function of z using Equation 15 as follows.

In order to simplify the expression (16), a coefficient is defined as in Equation 17, and Equation 16 is expressed as in Equation 18.

here And Includes measurement error and altitude error, and can be expressed as follows in consideration of these errors.

Now, z is obtained by substituting Equation 18 into Equation 14.

Substituting z obtained in Equation 20 into Equation 18, two positions can be finally obtained.

If you have more than two base stations:

When three or more base stations are used, the distance measurement equation may be set as follows.

Where the subscript is the base station identifier. Reassembling Equation 21 can be expressed as follows.

Equation 22 is expressed as equation 23 for n satellites.

Where X is the position to calculate, H, And Are as follows.

X from Equation 23 can be determined as follows.

But the unknown Since it is not possible to find the position directly in Equation 23, Gives you a quadratic equation for After calculating the equation, two navigation solutions are obtained by substituting Eq.

As such, even if there are two or more base stations, the terminal position can be obtained. However, two terminals are always obtained and the position error range is also determined by the magnitude of the measurement error. Even so, when using two or more base stations, the code search range is further reduced since only the gray part of FIG. 18 needs to be searched.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

As described above, according to the present invention, since the base station includes the navigation data in the auxiliary information provided to the terminal, the calculation amount is reduced and the reception sensitivity is increased during the positioning process. Therefore, the positioning can be performed even in a room where GPS signal power is weak. In addition, by including information on the cell coverage of the base station in the auxiliary information, the code search range is reduced and the amount of calculation is reduced in the positioning process. The GPS receiver and the positioning method according to the present invention can be used not only for emergency rescue services but also for intelligent transportation systems, criminal tracking, cellular system design, and location-based billing according to call location. It can be widely used.

Claims (8)

A satellite positioning system (GPS) receiver for receiving auxiliary information through a wireless communication network including at least one base station and measuring pseudo ranges for each of a plurality of satellites using the auxiliary information. Receiving an GPS signal including a carrier wave, navigation data, and a first pseudo noise code from each of the plurality of satellites, downconverting to an intermediate frequency (IF) band, and sampling and generating an IF sampling signal; Accepting the assistance information including time-tagged navigation data from the base station and generating a second pseudonoise code required to be identical to the first pseudonoise code; Recovering the first pseudonoise code by removing the navigation data using the time-tagged navigation data from the IF sampling signal; And Determining a pseudo distance by calculating a delay time of the first pseudo noise code based on a calculation of a correlation value with the second pseudo noise code; Positioning method comprising a. A satellite positioning system (GPS) receiver for receiving auxiliary information through a wireless communication network including at least one signal transmission and reception system and measuring pseudo ranges for each of a plurality of satellites using the auxiliary information. (a) receiving a GPS signal including a carrier wave, navigation data, and a first pseudo noise code from each of the plurality of satellites, downconverting to an intermediate frequency (IF) band, and sampling to generate an IF sampling signal, and generating the IF sampling signal; Recovering a first pseudonoise code from the second pseudonoise code, and generating a second pseudonoise code required to be identical to the first pseudonoise code; (b) receiving pseudorange information about the signal transmission and reception system and valid range information indicating a distance range between the signal transmission and reception system and the receiver; And (c) determining the pseudo distance by calculating a delay time of the first pseudo noise code based on a calculation of a correlation value with the second pseudo noise code; Including; In step (c), a positioning method of reducing the search range for the correlation value calculation using the pseudorange information of the signal transmission and reception system and the effective range data and performing the correlation value calculation on the reduced search range only. . The method of claim 2, wherein step (c) (c1) setting a search reference point using pseudorange information of the signal transmission / reception system; And (c2) determining a search range based on the search reference point using the effective range data; Positioning method comprising a. The method of claim 3, wherein step (c2) (c2a) setting a search reference point using pseudorange information of the signal transmission / reception system; And (c2b) determining a search range based on the search reference point using the effective range data; Positioning method comprising a. A satellite positioning system (GPS) receiver for receiving auxiliary information through a wireless communication network including at least one signal transmission and reception system and measuring pseudo ranges for each of a plurality of satellites using the auxiliary information. A down converter for receiving a GPS signal in an RF band and downconverting a frequency band of the GPS signal to an IF band using a predetermined local oscillation signal; An analog / digital converter configured to output an IF sampling signal by sampling the IF signal from the down converter using a predetermined sampling clock; A snapshot memory for storing the IF sampling signal; Time-tagged navigation data to remove navigation data included in the IF sampling signal to recover a first pseudonoise code included in the IF sampling signal and to be identical to the first pseudonoise code. A digital signal processor for generating a pseudo-noise code and calculating a pseudo-distance for each of the plurality of satellites by calculating a delay time of the first pseudo-noise code based on calculation of a correlation value with the second pseudo-noise code; A power control unit controlling power supply to the down conversion unit, the analog / digital conversion unit, the snapshot memory, and the digital signal processing unit; And Control means for receiving the time-tagged navigation data through a predetermined modem and providing the time-tagged navigation data to the digital signal processor; GPS receiver comprising a. The method of claim 5, A frequency synthesizer configured to generate the local oscillation signal and the sampling clock using a predetermined reference clock; The GPS receiver further comprises, wherein the frequency synthesizer shares the reference clock with the control means. A satellite positioning system (GPS) receiver for receiving auxiliary information through a wireless communication network including at least one signal transmission and reception system and measuring pseudo ranges for each of a plurality of satellites using the auxiliary information. A down converter for receiving a GPS signal in an RF band and downconverting a frequency band of the GPS signal to an IF band using a predetermined local oscillation signal; An analog / digital converter configured to output an IF sampling signal by sampling the IF signal from the down converter using a predetermined sampling clock; A snapshot memory for storing the IF sampling signal; Recovering a first pseudo noise code included in the IF sampling signal, generating a second pseudo noise code required to be the same as the first pseudo noise code, and calculating a correlation value with the second pseudo noise code; A digital signal processing unit calculating a pseudo distance for each of the plurality of satellites by calculating a delay time of the first pseudo noise code; A power control unit controlling power supply to the down conversion unit, the analog / digital conversion unit, the snapshot memory, and the digital signal processing unit; And The digital signal processor receives pseudo range information of the signal transmission / reception system and valid range information indicating a distance range between the signal transmission / reception system and the receiver through a predetermined modem from the signal transmission / reception system. Control means for providing and controlling the power control unit; The digital signal processing unit may reduce the search range for the correlation value calculation using the pseudo distance information of the signal transmission and reception system and the effective range data, and perform the correlation value calculation only on the reduced search range. GPS receiver. The method of claim 7, wherein A frequency synthesizer configured to generate the local oscillation signal and the sampling clock using a predetermined reference clock; The GPS receiver further comprises, wherein the frequency synthesizer shares the reference clock with the control means.