JP5002966B2 - Mobile terminal location system - Google Patents

Description

  The present invention relates to a positioning mobile terminal, a mobile terminal location specifying method, a mobile terminal location specifying system, and a security system using the mobile terminal. Specifically, a positioning mobile terminal that specifies the position of a mobile terminal based on a beacon signal transmitted from an asynchronous base station for mobile terminals that is not accurately synchronized between base stations, a mobile terminal location specifying method, The present invention relates to a terminal position specifying system and a security system using a portable terminal.

  Conventionally, as a method of determining the position of a mobile terminal in a cellular communication network, enhanced-offset time in which the position of the mobile terminal is measured by measuring a time difference between radio wave propagation times of specific signals arriving from different base stations. A technique of differential (Enhanced Offset Differential: E-OTD) is known (see, for example, Patent Document 1).

JP 2003-204573 A (first page, FIG. 1)

In a wireless communication system in which synchronization adjustment is performed between base stations, the time difference between arrival times arriving from a plurality of base stations is calculated based on time information when a plurality of base stations receive specific signals transmitted at the same timing. By doing so, the position of the moving body can be calculated. For example, in a code division multiple access (CDMA) system, a base station constantly transmits a signal synchronized with high precision at the time of universal agreement (UTC). The mobile receiver receives this transmission signal and extracts the time information from the transmission signal, thereby obtaining the radio wave propagation time between the base station and the mobile body.
However, in an asynchronous wireless communication system in which gradual time synchronization is established between base stations but accurate time synchronization is not established, accurate time synchronization is not established between specific signals transmitted from the respective base stations. For this reason, there is a problem that the mobile object cannot accurately measure the position of the mobile object by a technique such as E-OTD because it cannot measure the exact time difference in the propagation time of the radio wave transmitted from each base station. It was.

  The present invention has been made to solve such a problem, and in a radio communication system including an asynchronous base station and a mobile terminal, the radio wave propagation time until a specific signal emitted by each asynchronous base station arrives at a mobile object is achieved. It is an object of the present invention to obtain a mobile terminal position specifying system that calculates a time difference between base stations and specifies a position of a mobile object based on the time difference.

The mobile terminal location specifying system according to the present invention includes a plurality of asynchronous base stations that do not synchronize time between base stations and transmit beacon signals at predetermined intervals at predetermined timings, and a mobile terminal. A position determination system for a mobile terminal that calculates a position, wherein the asynchronous base station includes a GPS reception processing unit, a communication unit, and a crystal resonator, and the GPS reception processing unit receives a GPS signal transmitted by a GPS satellite. The GPS time is repeatedly calculated based on the GPS signal, and the communication unit calculates the latest GPS calculated by the GPS reception processing unit when it is time to transmit the beacon signal based on the time information output by the crystal resonator. A time delay information between the time, the time until the beacon signal is transmitted with reference to the GPS time, and the position information of the asynchronous base station. The mobile terminal periodically transmits a communication signal, the mobile terminal receives the beacon signal from the asynchronous base station, a clock unit that outputs the reception time when the beacon signal is received, and the position of the mobile terminal An arithmetic processing unit for calculating, the arithmetic processing unit, the communication unit acquired based on the beacon signal received from each of the three or more asynchronous base stations, the latest GPS time and the time delay information, Using the position information of the asynchronous base station and the reception time, a difference between the asynchronous base station with respect to the distance from the asynchronous base station to the mobile terminal is calculated, and the difference and the position information of the asynchronous base station Is used to calculate the position of the mobile terminal.

According to the present invention, in a wireless communication system composed of an asynchronous base station and a mobile terminal, the GPS signal and a minimum information such as a time delay with respect to the GPS time are transmitted on the specific signal transmitted by the asynchronous base station. By doing so, the mobile terminal that has received the specific signal can measure its own position.
In addition, a mobile terminal location specifying system can be easily constructed by slightly modifying the existing wireless communication system.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a mobile terminal location specifying system according to Embodiment 1. Asynchronous mobile communication base stations (hereinafter referred to as “base stations”) 20a to 20d that do not have accurate time synchronization between base stations, but do not accurately time synchronize, receive a GPS (Global Positioning System) receiver 30. The GPS signal 110 including the GPS time is received from the GPS satellite 50. The GPS time is also referred to as UTC (Universal Coordinated Time = Universal Time Coordinated).

  The base station 20 periodically transmits a frame called a beacon signal 40. The beacon signal 40 is periodically transmitted, for example, at a rate of 10 times or more per second. The mobile terminal 10 confirms the presence of the base station 20 by the beacon signal 40, and the information in the frame transmitted by the beacon signal 40 is displayed. get. The beacon signal 40 transmitted periodically is a time delay between the most recent GPS time 101 transmitted by the GPS signal received from the GPS satellite 50 and the beacon signal transmitted from the most recent GPS time. The time delay information 102, the base station ID number of the own base station, and the accurate position information of the own base station measured in advance are transmitted in a frame. The time delay information 102 will be described later.

  Here, the base stations 20a to 20d according to Embodiment 1 are characterized in that no synchronization adjustment is performed between the base stations. That is, the mobile terminal location specifying system according to Embodiment 1 includes an asynchronous base station and mobile terminal. The timings of the beacon signals 40a to 40d transmitted from each base station are not synchronized with each other, and each base station 20 transmits the beacon signals 40a to 40d at a unique timing.

  FIG. 2 is a block diagram showing the configuration of the base station 20. The base station 20 includes a communication unit 21, a processing unit 22, a storage unit 23, a GPS receiving unit 24, and a clock 25. The GPS receiving unit 24 receives the GPS signal 110 from the GPS satellite 50 and outputs the received GPS signal 110 to the processing unit 22. The processing unit 22 demodulates the GPS signal 110 to acquire GPS time. On the other hand, the clock 25 includes a quartz oscillator and outputs time information 26 to the processing unit 22. Based on the time information 26, the processing unit 22 periodically transmits a beacon signal at a period of 10 Hz, for example. When it is time to transmit the beacon signal, the processing unit 22 extracts the base station ID number of the local station and the base station position information of the local station stored in advance in the storage unit 23, and transmits the base station ID number of the local station via the communication unit 21. The base station ID number, the base station position information of the own station, the latest GPS time, and the transmission time information of the beacon signal based on the latest GPS time until the beacon signal is transmitted from the latest GPS time. And send time delay information.

  FIG. 3 is a block diagram showing the configuration of the mobile phone 10. The mobile phone 10 includes a communication unit 11, an arithmetic processing unit 12, a clock 13, a storage unit 14, and a display unit 15. The communication unit 11 receives the beacon signal 40 from the base station 20. The arithmetic processing unit 12 stores the information of the beacon signal 40 and the reception time at which the beacon signal 40 is received at the time output by the clock 13 as a series of data in the storage unit 14. The arithmetic processing unit 12 calculates the position of its own mobile phone based on the data stored in the storage unit 14 and displays the calculation result on the display unit 15.

  Next, a method for calculating the position of the mobile phone will be described. FIG. 4 is a diagram showing an example of a time chart for transmitting and receiving the beacon signal 40 between the base station 20 and the mobile phone 10. In FIG. 4, the base station A transmits the beacon signal A with a delay of time ta with respect to the GPS time tg acquired from the GPS signal 110 from the GPS satellite 50. The time ta in FIG. 4 is referred to as time delay information. Similarly, the base station B transmits the beacon signal B with a delay of time tb with respect to the GPS time tg acquired from the GPS signal from the GPS satellite. The base station C transmits the beacon signal C with a delay of time tc with respect to the GPS time tg acquired from the GPS signal from the GPS satellite. tb and tc are both time delay information. As described above, the beacon signal 40 includes the base station ID number of the local station, the base station position information of the local station, the latest GPS time, and the transmission time of the beacon signal based on the latest GPS time. Time delay information 102 between information and the latest GPS time until the transmission of the beacon signal is carried and transmitted.

  In FIG. 4, the mobile phone 10 receives the beacon signal A from the base station A 20 a at time tra, which is the time output by the clock 10 that is the internal clock of the mobile phone 10. Then, the information transmitted by the beacon signal A and the reception time tra are associated with each other and stored in the storage unit 14. Similarly, the mobile phone 10 receives the beacon signal B from the base station B 20b at the reception time trb, and stores the information transmitted by the beacon signal B and the reception time trb in the storage unit 14 in association with each other. Further, the mobile phone 10 receives the beacon signal C from the base station B 20 c at the reception time trc, and stores the transmission information of the beacon signal C and the reception time trc in association with each other in the storage unit 14.

  FIG. 5 shows an example of information stored in the storage unit 14. The storage unit 14 stores a base station ID number, which is transmission information of the beacon signal 40, its own base station position information, GPS time tg, time delay information td, and reception time tr when the beacon signal 40 is received.

  FIG. 6 shows a flowchart in which the arithmetic processing unit 12 of the mobile phone 10 according to the first embodiment measures its own position. A mobile phone positioning method will be described with reference to FIG.

(1) The arithmetic processing unit 12 of the mobile phone 10 confirms that there is received data of beacon signals received from three or more different base stations (step S101; hereinafter referred to as S101).

(2) If there is no reception data of beacon signals from three or more base stations, reception of beacon signals is continued (S102).

(3) If the beacon signal 40 is received from three or more base stations 20, the arithmetic processing unit 12 calculates the base time from the GPS time tg, the time delay information td, and the reception time tr stored in the storage unit 14. The radio wave propagation time tt of the beacon signal from the station 20 to the mobile terminal 10 is calculated (S103).
Propagation time tta = tra- (tga + tda) + e (Formula 1)
Propagation time ttb = trb- (tgb + tdb) + e (Formula 2)
Propagation time ttc = trc-(tgc + tdc) + e (Equation 3)
Here, the propagation time tta is the propagation time of the beacon signal from the base station A to the mobile phone 10, and ttb and ttc are the propagation times of the radio waves from the base stations B and C to the mobile phone 10, respectively. E is a clock error of the clock 13 provided in the mobile phone 10.

  As described above, the base station 20 transmits the beacon signal 40 periodically transmitted with the GPS time and the time delay information 102 from the GPS time until the beacon signal 40 is transmitted. The mobile terminal 10 receives the beacon signal 40 and can calculate the propagation time tt of the beacon signal from the GPS time tg put on the beacon signal 40, the time delay information td, and the reception time tr.

(4) Next, the arithmetic processing unit 12 calculates the difference in propagation time from each base station between the base stations using the propagation time tt obtained in S103 (S104).
Δtab = (tra−trb) − (tga−tgb) − (tda−tdb) (Formula 4)
Δtac = (tra−trc) − (tga−tgc) − (tda−tdc) (Formula 5)
Δtbc = (trb−trc) − (tgb−tgc) − (tdb−tdc) (Formula 6)
Δtab is a difference between the propagation time of the beacon signal 40 from the base station A to the mobile terminal 10 and the propagation time of the beacon signal 40 from the base station B to the mobile terminal 10, and Δtac is the base station A and the base station C Δtbc is the difference in propagation time between the base station B and the base station C. By calculating the propagation time difference, the clock error e of the clock 13 is eliminated.

(5) Next, the arithmetic processing unit 12 multiplies the difference in propagation time calculated in S104 by the speed of light c, and calculates the difference Δd in the distance between each base station and the mobile terminal 10 between three or more base stations. calculate.
Δdab = c · Δtab
Δdac = c · Δtac
Δdbc = c · Δtbc
Δdab is the difference between the distance between the base station A and the mobile terminal and the distance between the base station B and the mobile terminal. Similarly, Δdac is the difference between the distance between the base station A and the mobile terminal and the distance between the base station C and the mobile terminal, and Δdbc is the distance between the base station B and the mobile terminal and the distance between the base station C and the mobile terminal. It is a difference.

  The arithmetic processing unit 12 calculates the difference between at least two distances among the calculated distance differences Δdab, Δdac, Δdbc between each base station and the mobile terminal 10 and the base station position information of each base station transmitted by the beacon signal. Are used to calculate the position of the mobile terminal 10 (S105). The calculation of the position can be performed, for example, by a method of creating a hyperbola from the difference in distance and the position information of the base station and obtaining the intersection of a plurality of hyperbola created at each base station (hyperbola positioning method).

  FIG. 7 shows a positioning conceptual diagram of the hyperbolic positioning method. In FIG. 7, a hyperbola 1 is a hyperbola in which the distance between the base station A 20a and the base station C 20c is a constant value (Δdac), and a hyperbola 2 is a distance in which the distance between the base station B 20b and the base station C 20c is a constant value (Δdbc). It is a hyperbola. By obtaining the intersection of the hyperbola 1 and the hyperbola 2, the position of the mobile terminal can be obtained. Here, the position is obtained from two hyperbola, but the position may be obtained from three hyperbola by adding a hyperbola in which the distance between the base station A 20a and the base station B 20b is a constant value (Δdab).

(6) The mobile terminal 10 displays the positioning result on the display unit 15 (S106).

  As described above, in the positioning system according to Embodiment 1, the base station includes the GPS receiver, and acquires the GPS time from the GPS signal from the GPS satellite. The base station periodically sends out a beacon signal. The beacon signal includes information on the acquired latest GPS time, a time delay from the most recent GPS time until the beacon signal is transmitted, the ID number of the base station, and its own base station position information. The mobile terminal that has received the beacon signal uses each of the reception time at which the beacon signal is received, the latest GPS time acquired from the beacon signal, and the time delay until the beacon signal is transmitted from the latest GPS time. The propagation time of the beacon signal from the base station is calculated. By subtracting the propagation time, the difference in propagation time from each base station is calculated. The position of the mobile terminal is calculated from the calculated difference in propagation time and the base station position information.

Thereby, in the positioning system according to the first embodiment, the portable terminal can measure its own position by transmitting the existing beacon signal with the minimum information such as GPS time and time delay. This makes it possible to easily construct a mobile terminal location specifying system by using the existing equipment and making the minimum equipment modification.
Further, in the positioning system according to Embodiment 1, synchronization between base stations is unnecessary, and the mobile terminal obtains GPS time and time delay information to calculate the difference in propagation time from each base station. The position of the mobile terminal can be accurately measured.

  The time delay information 102 from the latest GPS time may be the time output by the clock 13.

  Further, the base station 20 may include a pulse generator 27 that emits a periodic pulse signal, and the time delay information 102 may transmit the number of pulses from the pulse generator 26. The base station counts the number of pulses from the most recent GPS time until the beacon signal is transmitted, and transmits it to the mobile terminal. The mobile terminal calculates the radio wave propagation time of the beacon signal by converting the time from the number of pulses. You may do it.

  Further, the base station position information may be transmitted by the base station, or the mobile terminal 10 has a correspondence table between the base station ID number and the base station position information. From the base station ID number received from the base station, the mobile terminal 10 10 may acquire the position of the base station.

Embodiment 2
In the first embodiment, the arithmetic processing unit 12 of the mobile terminal 10 receives the beacon signal 40 from each base station 20 once, and performs the positioning calculation from the received information once. In Embodiment 2, the beacon signal 40 is received a plurality of times from the same base station, and the difference in the propagation time of the beacon signal is calculated from the beacon signal received a plurality of times.
FIG. 8 is a flowchart in which the arithmetic processing unit 12 of the mobile phone 10 according to the second embodiment measures its own position. The configuration of the mobile terminal location specifying system in the second embodiment is the same as that shown in FIG. Components having the same functions as those in Embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

The operation of the arithmetic processing unit 12 will be described with reference to FIG.
(1) In step S201 (hereinafter referred to as S201), the number N of beacon signal receptions is set. The number N of receptions may be automatically set in the arithmetic processing unit 12 in the mobile phone so as to obtain a desired S / N (Signal to Noise), or is set by key input from the outside. You may do it.
(2) Each time the communication unit 11 receives the beacon signal 40 from the base station 20, the arithmetic processing unit 12 calculates the propagation time from the base station to the mobile terminal 10 and the difference between the propagation times (S202 to S204). .
(3) In the propagation time difference, the arithmetic processing unit 12 calculates an average value of the propagation time difference for each base station that has calculated the propagation time difference (S205).
(4) When the beacon signal reception count reaches the reception count N set in S201 (S206), positioning calculation is performed based on the base station position information of each base station and the difference (average value) in propagation time (S207). ).

  As described above, in the second embodiment, paying attention to the fact that the base station 20 of the existing wireless communication system transmits the beacon signal 10 times or more per second, the beacon signal is received a plurality of times, and the result The position is calculated using. As a result, S / N is improved, and it is possible to construct a mobile terminal location specifying system that is simple and highly accurate without synchronization between base stations by using the existing equipment and making the minimum equipment modification. it can.

Embodiment 3
In the first and second embodiments, the mobile terminal has received the beacon signal transmitted from the base station and has positioned its own position. In the third embodiment, the mobile terminal includes a GPS receiver, receives a beacon signal transmitted from the base station and a GPS signal transmitted from a GPS satellite, and calculates its own position. In addition, the same number is attached | subjected to what has the same function as Embodiment 1, 2, and the description is abbreviate | omitted.

  FIG. 9 is a configuration diagram of the mobile terminal location specifying system according to the third embodiment. The difference from FIG. 1 is that the mobile terminal 10 includes a GPS receiver and directly receives the GPS signal 110 transmitted from the GPS satellite 50.

  The mobile terminal 10 receives the beacon signal transmitted from the base station 20 and the GPS signal 110 as in the first embodiment. The arithmetic processing unit 12 of the mobile terminal 10 associates the base station ID number, base station position information, GPS time, and time delay information 102 transmitted by the beacon signal with the reception time when the beacon signal is received, and stores the storage unit 14. To remember.

  The arithmetic processing unit 12 correlates the satellite number of the GPS satellite that demodulates the GPS signal 110 and transmits the GPS signal, the positional information of the GPS satellite, the GPS time, and the reception time when the GPS signal is received, and stores the storage unit 14. To remember. The satellite position information is obtained by demodulating a navigation message sent by a GPS signal.

  FIG. 10 shows an example of information stored in the storage unit 14. In the example of FIG. 10, the mobile terminal 10 receives beacon signals 40 from two base stations A and B, and receives GPS signals from two GPS satellites AA and BB. Thus, the portable terminal 10 once collects a beacon signal and a GPS signal that can be received regardless of the beacon signal and the GPS signal.

  Next, the arithmetic processing unit 12 of the mobile terminal extracts three signals at random from the collected beacon signals and GPS signals. Then, based on the three signals extracted at random, the difference of the radio wave propagation time from the base station or the GPS satellite is calculated as in the first embodiment, and the difference of the propagation time and the position information of the base station or the satellite are calculated. Are used to calculate the position of the mobile terminal.

  As described above, according to the third embodiment, the mobile terminal 10 includes the GPS receiver, collects receivable beacon signals and GPS signals regardless of the base station and the GPS satellite, and a total of 3 A set of two base stations and GPS satellites was extracted. Based on the difference in radio wave propagation time from the base station or GPS satellite and the position information of the base station or GPS satellite, the position of the mobile terminal is determined as in the first embodiment.

  Thereby, if the portable terminal 10 can receive signals from three or more base stations or GPS satellites in combination with the base station and the GPS satellites, the mobile terminal 10 can measure its own position. As described above, in the third embodiment, even if the reception of radio waves from the base station or GPS satellite is bad in the city or the like, if signals from three or more base stations or GPS satellites can be received, The mobile terminal 10 can measure its own position, and can reduce the area where positioning is impossible.

Embodiment 4
In the first to third embodiments, the mobile terminal 10 calculates its own position in the arithmetic processing unit 12. In Embodiment 4, the information of the beacon signal received from the base station is transmitted to the position management device that is the management center, the positioning operation is performed in the position management device, and the result is transmitted to the mobile terminal.

  FIG. 11 is a configuration diagram of the mobile terminal location specifying system in the fourth embodiment. In FIG. 11, components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  Similarly to the first embodiment, the mobile terminal 10 receives a beacon signal from the base station 20 and stores the information transmitted by the beacon signal and the reception time of the beacon signal in the storage unit 14. The mobile terminal 10 transmits information stored in the storage unit 14 to the mobile terminal location management device 90. The mobile terminal position management device 90 calculates the position of the mobile terminal 10 based on the received information, and transmits the positioning calculation result 111 to the mobile terminal 10. The mobile terminal 10 can acquire its own position by receiving information from the mobile terminal location management device 90.

  As described above, in the fourth embodiment, since the positioning calculation is performed by the portable terminal position management device, the calculation load on the portable terminal 10 is reduced, and the configuration of the portable telephone can be simplified.

Embodiment 5
In the fifth embodiment, an example of the position display of the mobile phone described in the first to fourth embodiments and an example of an application to which these mobile phones are applied will be shown.

  FIG. 12 is a diagram showing an example of the display of the position of the mobile phone specified by the management terminal 10. On the display device of the mobile phone or the display device of the management terminal that manages the location of the mobile phone, the locations of multiple mobile phones that are indoors as well as outdoors are displayed on the map, and which mobile phone is in which location However, it is possible to grasp without being conscious of outdoor or indoor.

  FIG. 13 is a diagram illustrating an example of an application that uses a mobile phone as a security terminal. The security guard who detects the anomaly takes a picture of the scene with a mobile phone camera. Thereafter, the photographed on-site photograph is transmitted to the security central terminal which is the management terminal. The security central terminal can share information by distributing the location of the occurrence of the anomaly and the on-site photo to each security terminal being guarded. Here, according to the present invention, the site of occurrence of an abnormality is not limited to the outdoors but may be indoors, and position information can be shared.

  FIG. 14 is an example of an application using a mobile phone as a disaster prevention terminal. When a disaster such as an earthquake or fire occurs in a factory or office, employees carrying a mobile phone send their location and the disaster situation taken with the mobile phone camera to the disaster prevention central terminal, which is the management terminal. To do. The disaster prevention central terminal can share the disaster situation by distributing the disaster situation and the call result. Here, according to this invention, since the disaster prevention central terminal can grasp | ascertain a position also about the employee who exists indoor, it is useful for disaster prevention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the position identification system of the portable terminal which concerns on Embodiment 1 of this invention. It is a block diagram showing the structure of the base station which concerns on Embodiment 1 of this invention. It is a block diagram showing the structure of the portable terminal which concerns on Embodiment 1 of this invention. It is an example of the figure which showed the time chart in which the base station which concerns on Embodiment 1 of this invention and a mobile telephone transmits and receives a beacon signal. An example of the information memorize | stored in the memory | storage part 14 which concerns on Embodiment 1 of this invention is shown. It is a flowchart figure in which the mobile telephone 10 which concerns on Embodiment 1 of this invention pinpoints a self-position. It is a figure which shows the conceptual diagram of the hyperbolic positioning system which concerns on Embodiment 1 of this invention. It is a flowchart figure in which the mobile telephone 10 which concerns on Embodiment 2 of this invention pinpoints a self-position. It is a block diagram of the position specific system of the portable terminal which concerns on Embodiment 3 of this invention. An example of the information memorized by storage part 14 concerning Embodiment 3 of this invention is shown. It is a block diagram of the position specific system of the portable terminal which concerns on Embodiment 4 of this invention. It is the figure which showed an example of the position display of the mobile telephone which the management terminal 10 which concerns on Embodiment 5 of this invention specified. It is the figure which showed an example of the application which used the mobile telephone which concerns on Embodiment 5 of this invention as a security terminal. It is the figure which showed an example of the application which used the mobile telephone which concerns on Embodiment 5 of this invention as a terminal for disaster prevention.

Explanation of symbols

10 mobile phones, 11 communication units, 12 arithmetic processing units, 13 clocks, 14 storage units, 15 display units, 20 base stations, 21 communication units, 22 processing units, 23 storage units, 24 GPS reception units, 25 clocks, 27 pulses Generator, 30 GPS receiver, 40 beacon signal, 50 GPS satellite, 90 portable terminal location management device, 101 GPS time, 102 time delay information, 110 GPS signal, 111 positioning calculation result.

Claims (1)

A mobile terminal location determination system that includes a plurality of asynchronous base stations that do not have time synchronization between base stations and transmit beacon signals at predetermined intervals at predetermined intervals, and a mobile terminal, and calculates the position of the mobile terminal. And
The asynchronous base station includes a GPS reception processing unit, a communication unit, and a crystal resonator,
The GPS reception processing unit receives a GPS signal transmitted by a GPS satellite and repeatedly calculates a GPS time based on the GPS signal,
The communication unit transmits the beacon signal based on the time information output from the crystal resonator, the latest GPS time calculated by the GPS reception processing unit, and the beacon signal based on the GPS time. Periodically sending a beacon signal consisting of time delay information until transmission and position information of the asynchronous base station,
The portable terminal includes a communication unit that receives the beacon signal from the asynchronous base station, a clock unit that outputs a reception time when the beacon signal is received, and an arithmetic processing unit that calculates the position of the portable terminal.
The arithmetic processing unit is configured to acquire the latest GPS time, the time delay information, and the position information of the asynchronous base station, which the communication unit acquires based on the beacon signal received from each of the three or more asynchronous base stations. The difference between the asynchronous base station with respect to the distance between the asynchronous base station and the portable terminal is calculated using the reception time, and the position of the portable terminal is calculated using the difference and the position information of the asynchronous base station. A position identifying system for a portable terminal, characterized in that:

Images