JP4228904B2 - Satellite selection method, mobile terminal, information server, and information transmission system - Google Patents

Description

  The present invention relates to a satellite selection method for selecting a positioning satellite for transmitting a positioning signal used for positioning of the current position from among a plurality of satellites, a mobile terminal for selecting a positioning satellite according to the satellite selection method, an information server, and information It relates to a transmission system.

There is a mobile terminal (for example, a GPS receiver disclosed in Japanese Patent Laid-Open No. 11-316270) that uses a GPS signal transmitted from a GPS (Global Positioning System) satellite to measure the current position. Conventionally known. This GPS receiver is configured to include a plurality of demodulation units and arithmetic processing units, and each demodulating unit individually demodulates each GPS signal transmitted from a plurality of GPS satellites, The current position is measured based on orbit information and propagation time included in the demodulated GPS signal. In this case, it is generally known that the larger the elevation angle of a GPS satellite is, the less noise is superimposed on the GPS signal due to the influence of the atmosphere and the ionosphere. For this reason, this GPS receiver employs a configuration that preferentially selects a GPS satellite having a large elevation angle and receives each GPS signal transmitted from the GPS satellite. Therefore, with this GPS receiver, it is possible to measure the current position with high accuracy.
JP-A-11-316270 (page 3-5)

  However, the conventional GPS receiver has the following problems. That is, in this GPS receiver, a GPS satellite having a large elevation angle is preferentially selected. In this case, it takes a relatively long time to acquire the trajectory information included in the GPS signal. For this reason, in this type of GPS receiver, generally, in order to shorten the positioning time, the acquired trajectory information is stored in a memory or the like, and the trajectory information is reused in the next positioning. Is adopted. However, a GPS satellite with a large elevation does not always stay in the field of view viewed from the current position for a long time. For example, when positioning is performed again after a predetermined time has elapsed, the GPS satellite moves out of the field of view. There is a possibility that the GPS signal cannot be received. In this case, it is necessary to reselect another GPS satellite and acquire the orbit information again. Therefore, this GPS receiver has a problem that it is difficult to shorten the positioning time by the frequency of reselecting the GPS satellite and acquiring the orbit information again.

  The present invention has been made in view of such problems, and a main object of the present invention is to provide a satellite selection method, a mobile terminal, an information server, and an information transmission system that can measure the current position in a short time.

  In order to achieve the above object, the satellite selection method according to the present invention includes N positioning satellites (N is a natural number of 2 or more) used for positioning of the current position among a plurality of positioning satellites that transmit positioning signals. A satellite selection method for selecting satellites, wherein M (M is a natural number less than N) positioning satellites are selected from the positioning satellites in descending order of elevation angle, and the M positioning satellites are excluded. From the other positioning satellites, the remaining positioning satellites are selected in descending order of the stay time after the current time in the field of view as viewed from the current position.

  According to this satellite selection method, M positioning satellites are selected from the positioning satellites in descending order of elevation angle, and the staying time is selected from the other positioning satellites excluding the M positioning satellites. By selecting the remaining positioning satellites in the longest order, for example, a mobile terminal that receives a positioning signal and measures the current position has a large elevation angle that can receive the positioning signal with little noise superposition. Both the positioning satellite and the positioning satellite having a long residence time capable of receiving the positioning signal for a long time can be used for positioning of the current position. Therefore, by using a positioning satellite having a large elevation angle, for example, the mobile terminal can be positioned with high accuracy. Further, by using a positioning satellite having a long staying time, for example, the mobile terminal can be positioned in a short time.

  The satellite selection method according to the present invention selects N positioning satellites (N is a natural number of 2 or more) for positioning at the current position from among a plurality of positioning satellites that transmit positioning signals. In the satellite selection method, M positioning satellites (M is a natural number less than N) are selected from the positioning satellites in the order of the length of stay after the current time in the field of view as viewed from the current position. The remaining positioning satellites are selected from the other positioning satellites other than the M positioning satellites in descending order of elevation angle.

  According to this satellite selection method, M positioning satellites are selected from the positioning satellites in the order of long residence time, and the elevation angle is selected from the other positioning satellites excluding the M positioning satellites. By selecting the remaining positioning satellites in descending order, for example, the mobile terminal can be positioned with high accuracy and in a short time in the same manner as in the satellite selection method described above.

  In addition, the mobile terminal according to the present invention selects N (N is a natural number of 2 or more) positioning satellites used for positioning of the current position from among a plurality of positioning satellites that transmit positioning signals. And a positioning unit that measures the current position based on the positioning signals respectively transmitted from the N positioning satellites, wherein the satellite selection unit includes the satellite selection unit described above. The N positioning satellites are selected according to a method.

  According to this mobile terminal, the satellite selection unit selects N positioning satellites according to the above-described satellite selection method, so that a positioning satellite having a large elevation angle capable of receiving a positioning signal in a state in which noise is superimposed is reduced. Because both positioning satellites that can receive positioning signals over a long period of time and positioning satellites with a long residence time can be used for positioning the current position, the current position can be determined with high accuracy and in a short time. .

  In addition, the information server according to the present invention is a satellite that selects N (N is a natural number of 2 or more) positioning satellites used for positioning of the current position from among a plurality of positioning satellites that transmit positioning signals. An information server that includes a selector, and provides orbit information about the N positioning satellites to a mobile terminal that receives the positioning signal and measures the current position, wherein the satellite selector includes: The N positioning satellites are selected according to the satellite selection method described above.

  According to this information server, the satellite selecting unit selects N positioning satellites according to the satellite selection method described above, so that orbit information that can be used for a long time can be provided to the mobile terminal. Therefore, the frequency with which the mobile terminal should receive the trajectory information can be reduced. As a result, the battery consumption and communication cost of the mobile terminal can be reduced accordingly. In addition, by providing orbit information, the mobile terminal can omit the acquisition of orbit information from the positioning satellite, so that the mobile terminal can determine the current position in a shorter time accordingly. Can do.

  An information transmission system according to the present invention includes an information server that generates each orbit information for a plurality of positioning satellites that transmit positioning signals, and a mobile terminal that receives the positioning signals and measures the current position. A radio base station that transmits each of the orbit information, wherein the radio base station determines a position of the current position from among the positioning satellites when transmitting the orbit information. A transmission control unit that selects N (N is a natural number equal to or greater than 2) positioning satellites used for, and extracts orbit information about the N positioning satellites from each of the orbit information to be transmitted. The transmission control unit selects the N positioning satellites according to the satellite selection method.

  According to this information transmission system, the transmission control unit of the radio base station selects N positioning satellites according to the satellite selection method described above. For example, even if there are many mobile terminals, the positioning satellites Can be distributed to a plurality of radio base stations, the processing load on the information server can be reduced by the amount of the distributed processing.

  The best mode of a satellite selection method, a mobile terminal, an information server, and an information transmission system according to the present invention will be described below with reference to the accompanying drawings. An information transmission system 10 shown in FIG. 1 is an example of an information transmission system according to the present invention, and includes a plurality of radio base stations 2, 2..., An information server 3 and a network N, and a plurality of mobile phones 1, 1. .. (assuming that only one mobile phone 1 is shown in the figure) assist data Da described later can be transmitted.

  The mobile phone 1 corresponds to a mobile terminal according to the present invention, and includes a wireless communication unit 11, a GPS processing unit 12, an operation unit 13, a storage unit 14, a control unit 15, and a display unit 16, as shown in FIG. . The radio communication unit 11 transmits / receives a transmission request signal S1, assist data Da, geographic data Dt, and the like to and from the radio base station 2 under the control of the control unit 15. The GPS processing unit 12 outputs each of the GPS satellites 9, 9,... (Corresponding to the positioning satellite in the present invention) shown in FIG. 1 using the assist data Da stored in the storage unit 14 as will be described later. The received GPS signal Sg (corresponding to the positioning signal in the present invention) is received, and the current position of the mobile phone 1 is measured based on the received GPS signal Sg to generate position data Dp. Further, the GPS processing unit 12 includes, for example, an 8-channel signal processing circuit (not shown), and is configured to be capable of simultaneously processing eight GPS signals Sg. Here, in the assist data Da described above, orbit information (for example, ephemeris data) defined for each GPS satellite 9 and necessary for accurate position calculation of the GPS satellite 9 and rough position calculation of the GPS satellite 9 are calculated. Various information such as necessary trajectory information (eg, almanac data) is included. In addition, since the positioning principle of the current position by the GPS processing unit 12 is known, the description thereof is omitted. The operation unit 13 is configured by arranging various operation buttons (not shown) such as a numeric button for inputting a telephone number and a positioning button for instructing positioning of the current position, and operations corresponding to these button operations. Output a signal. The storage unit 14 stores an operation program of the control unit 15 and assist data Da, geographic data Dt, and the like received via the wireless communication unit 11.

  The control unit 15 controls the wireless communication unit 11, the GPS processing unit 12, and the display unit 16 according to the operation signal output from the operation unit 13. Further, the control unit 15 causes the storage unit 14 to store the assist data Da and the geographic data Dt that are transmitted from the radio base station 2 and received by the radio communication unit 11. In addition, the control unit 15 includes a point image representing the current position of the mobile phone 1 in the map image based on the position data Dp generated by the GPS processing unit 12 and the geographic data Dt stored in the storage unit 14. Image data Dg to be displayed in a superimposed manner is generated. The display unit 16 includes a color liquid crystal display as an example, and displays an image based on the image data Dg generated by the control unit 15 in color. Note that the mobile phone 1 is actually provided with a microphone, a speaker, and the like for calling, but illustration and description thereof are omitted for easy understanding of the invention.

  The wireless base stations 2, 2,... Are facilities installed in the usable area of the information transmission system 10 and wirelessly communicated with the mobile phone 1, and as shown in FIG. A communication modem 22, a storage device 23, and a control device 24 are provided. The wireless communication unit 21 transmits and receives a transmission request signal S1, assist data Da, geographic data Dt, and the like to and from the mobile phone 1 under the control of the control device 24. The communication modem 22 transmits and receives a transmission request signal S2 and assist data Da to and from the information server 3 via the network N. The storage device 23 stores an operation program of the control device 24, geographic data Dt including at least a communicable area of the wireless communication unit 21, assist data Da, and the like. The control device 24 corresponds to the transmission control unit in the present invention, and controls the operations of the wireless communication unit 21 and the communication modem 22. In addition, the control device 24 causes the wireless communication unit 21 to transmit assist data Da to the mobile phone 1. In this case, the control device 24 uses the mobile phone 1 from a plurality of GPS satellites 9 (for example, GPS satellites 9a to 9k shown in FIGS. 5 and 6) corresponding to each orbit information included in the assist data Da. Eight (e.g., N in the present invention) GPS satellites 9 having the same number as the number of channels of the GPS processing unit 12 are selected, and orbit information corresponding to the other GPS satellites 9 is deleted from the assist data Da. That is, the control device 24 extracts and transmits the orbit information corresponding to the eight selected GPS satellites 9. Further, when selecting the eight GPS satellites 9, the control device 24 follows the satellite selection method according to the present invention and selects five GPS satellites 9 a to 9 k in descending order of elevation angle (an example of M in the present invention). ) GPS satellites 9 are selected, and the remaining 3 after the current time in the field of view as viewed from the radio base station 2 (current position of the mobile phone 1) among the other GPS satellites 9 except for the five satellites 9 A selection process for selecting one GPS satellite 9 (corresponding to the remaining positioning satellites in the present invention) is executed.

  As shown in FIG. 4, the information server 3 includes a communication modem 31, a storage device 32, a GPS processing unit 33, and a control device 34. The communication modem 31 transmits and receives a transmission request signal S2 and assist data Da to and from the wireless base station 2 via the network N. The storage device 32 stores an operation program of the control device 34 and assist data Da generated by the GPS processing unit 33. The GPS processing unit 33 receives GPS signals Sg transmitted from GPS satellites 9, 9... (For example, GPS satellites 9 a to 9 k shown in FIGS. 5 and 6) that can be supplemented within the usable area of the information transmission system 10. Then, generation processing for generating assist data Da including orbit information about the GPS satellite 9 such as ephemeris data and almanac data is executed. The control device 34 controls the operation of the communication modem 31 and the GPS processing unit 33. Further, the control device 34 stores the assist data Da generated by the GPS processing unit 33 in the storage device 32. Furthermore, when the transmission request signal S2 is output from the radio base station 2, the control device 34 causes the communication modem 31 to transmit the assist data Da stored in the storage device 32 to the radio base station 2.

  Next, the overall operation of the information transmission system 10 will be described with reference to the drawings. In the information transmission system 10, the GPS processing unit 33 of the information server 3 repeatedly performs a generation process for generating assist data Da to be transmitted to the mobile phone 1 at predetermined time intervals. In this generation process, for example, the GPS processing unit 33 targets all the GPS satellites 9 that can receive the GPS signal Sg within the usable area of the information transmission system 10, and the GPS signal Sg transmitted from each GPS satellite 9. And assist data Da including orbit information about each of these GPS satellites 9 is generated. At this time, the control device 34 overwrites and stores the assist data Da generated by the GPS processing unit 33 in the storage device 32 each time the data is generated.

  On the other hand, for example, when positioning the current position on the mobile phone 1, first, the positioning button of the operation unit 13 is operated. In response to this, the control unit 15 of the mobile phone 1 causes the wireless communication unit 11 to transmit a transmission request signal S1 for requesting transmission of the assist data Da. At this time, in the wireless base station 2 that manages the communication area in which the mobile phone 1 exists, the wireless communication unit 21 receives the transmission request signal S1 transmitted from the mobile phone 1. In response to this, the control device 24 of the radio base station 2 causes the information server 3 to transmit a transmission request signal S2 for requesting the communication modem 22 to transmit the assist data Da via the network N. Next, the communication modem 31 of the information server 3 receives the transmission request signal S2 and outputs it to the control device 34. Subsequently, the control device 34 reads the latest assist data Da from the storage device 32 according to the transmission request signal S2, and causes the communication modem 31 to transmit the assist data Da to the radio base station 2.

  Next, the communication modem 22 of the radio base station 2 receives the assist data Da, and the control device 24 stores the assist data Da in the storage device 23. Next, the control device 24, based on each orbit information included in the assist data Da, GPS satellites 9, 9,... Corresponding to each orbit information (for example, GPS satellites 9a to 9k shown in FIGS. 5 and 6). These elevation angles are also specified. Further, as shown in FIG. 5, the control device 24 specifies the stay time after the current time of each GPS satellite 9 in the field of view as viewed from the radio base station 2 based on each orbit information. In this case, in specifying the staying time, it is assumed that the field of view viewed from the radio base station 2 and the field of view viewed from the current position of the mobile phone 1 are substantially equal. Subsequently, the control device 24 executes a selection process for selecting eight GPS satellites 9 from the GPS satellites 9a to 9k according to the satellite selection method according to the present invention. In this selection process, as shown in the figure, the control device 24 first selects five GPS satellites 9k, 9d, 9i, 9b, and 9c in this order from the GPS satellites 9a to 9k in descending order of elevation angle. To do. Next, the control device 24 selects the three GPS satellites 9g in order from the longest staying time among other GPS satellites 9 (GPS satellites 9a, 9e to 9h, 9j) excluding these five GPS satellites 9. , 9j, 9a are selected in this order. Note that the orbit after the current time in the GPS satellites 9a, 9e to 9h, 9j is indicated by a broken line in FIG. 6 (in this case, the length of the broken line represents the approximate stay time after the current time). Next, the control device 24 deletes the orbit information corresponding to the other GPS satellites 9 excluding the selected total of eight GPS satellites 9 from the assist data Da, and also deletes the assist data after the deletion to the wireless communication unit 21. Da is transmitted to the mobile phone 1. That is, the control device 24 extracts orbit information corresponding to the eight selected GPS satellites 9 (in this example, the GPS satellites 9a to 9d, 9g, and 9i to 9k) as transmission targets and transmits them to the mobile phone 1. . Further, the control device 24 causes the radio communication unit 21 to transmit the geographic data Dt together with the assist data Da to the mobile phone 1.

  Subsequently, the wireless communication unit 11 of the mobile phone 1 receives the assist data Da and the geographic data Dt, and the control unit 15 stores both the data Da and Dt in the storage unit 14 and transfers the assist data Da to the GPS processing unit 12. To do. In response to this, the GPS processing unit 12 receives the GPS signals Sg output from the GPS satellites 9a to 9d, 9g, and 9i to 9k using the orbit information included in the assist data Da. Next, the GPS processing unit 12 measures the current position of the mobile phone 1 based on each received GPS signal Sg and outputs position data Dp. Next, the control unit 15 reads the geographic data Dt stored in the storage unit 14, generates image data Dg based on the position data Dp and the geographic data Dt, and outputs the image data Dg to the display unit 16. In response to this, the display unit 16 displays an image in which a point image representing the current position of the mobile phone 1 and a map image are superimposed based on the image data Dg.

  On the other hand, when the current position is measured again with respect to the mobile phone 1 after a predetermined time (for example, 1 hour) has elapsed, the positioning button of the operation unit 13 is operated. In this case, when the trajectory information (ephemeris data) in the assist data Da is valid (when the current time is within, for example, two hours from the generation of the assist data Da), the mobile phone 1 receives the assist data Da ( The same GPS satellite 9 (same assist data Da) can be used for positioning the current position over a long period of time without re-acquisition. Therefore, when valid assist data Da is already stored in the storage unit 14, the control unit 15 of the mobile phone 1 reads the assist data Da from the storage unit 14 without transmitting the transmission request signal S1, and the GPS processing unit. 12 is output. In response to this, the GPS processing unit 12 receives the GPS signal Sg and measures the current position. In this case, since all of the GPS satellites 9a to 9d, 9g, 9i to 9k are located (stayed) in the field of view as viewed from the radio base station 2 (current position of the mobile phone 1), the GPS processing unit 12 All of the GPS signals Sg transmitted from these GPS satellites 9 can be received.

  As described above, according to the satellite selection method and the information transmission system 10, the five GPS satellites 9 are selected from the GPS satellites 9a to 9k in descending order of elevation angle, and the five GPS satellites 9 are excluded. GPS satellites 9 having a large elevation angle that can receive GPS signal Sg with little noise superimposed on mobile phone 1 by selecting three GPS satellites 9 from the GPS satellites 9 in order of long residence time 9 and the GPS satellite 9 having a long residence time capable of receiving the GPS signal Sg for a long time can be used for positioning of the current position. Therefore, by using the positioning satellites 9b, 9c, 9d, 9i, 9k having a large elevation angle, the mobile phone 1 can be positioned with high accuracy. Further, by using the positioning satellites 9a, 9g, 9j having a long staying time, the mobile phone 1 can be positioned in a short time. Further, since the frequency of receiving the assist data Da can be reduced, the battery consumption and communication cost of the mobile phone 1 can be reduced accordingly. Further, the control unit 24 of the radio base station 2 executes the selection process of the GPS satellites 9 so that the selection process of the GPS satellites 9 is distributed to a plurality of radio base stations 2 even if there are many mobile phones 1. Therefore, the processing load on the information server 3 can be reduced by the amount of processing distributed.

  In addition, this invention is not limited to said structure. For example, although the satellite selection method for selecting the GPS satellite 9 with the higher elevation angle first has been described above, the satellite selection method for selecting the GPS satellite 9 with the long stay time first can also be employed. Specifically, when the control device 24 of the radio base station 2 selects eight GPS satellites 9, for example, as shown in FIG. 7, first, in the field of view viewed from the position of the radio base station 2. Five GPS satellites 9g, 9j, 9d, 9k, and 9c are selected from the GPS satellites 9a to 9k in this order in the order of the long stay time after the current time. Next, the control device 24 selects the three GPS satellites 9i, 9b, and 9h in this order from the other GPS satellites 9 excluding these five GPS satellites 9 in descending order of elevation angle. Also in this selection method, since both the GPS satellite 9 having a large elevation angle and the GPS satellite 9 having a long stay time can be used for positioning of the current position, the mobile phone 1 can be made similar to the above selection method. On the other hand, the current position can be measured with high accuracy and in a short time.

  Further, the cellular phone 1 that measures the current position using the assist data Da provided by the information server 3 has been described as an example. However, the trajectory information is acquired by itself without using the assist data Da, and the current position is acquired. The present invention can also be applied to a mobile phone 1A (see FIG. 2) that measures the position. As shown in the figure, the cellular phone 1A includes a wireless communication unit 11, a GPS processing unit 12A (in this case, the GPS processing unit 12A corresponds to the satellite selection unit and the positioning unit in the present invention), an operation unit 13, a storage 14A, 15 A of control parts, and the display part 16 are provided. Note that the same components as those of the mobile phone 1 are denoted by the same reference numerals, and redundant description is omitted. In this case, almanac data for each GPS satellite 9 is stored in the storage unit 14A. In the cellular phone 1A, when the positioning button of the operation unit 13 is operated, the control unit 15A reads the almanac data from the storage unit 14A and outputs it to the GPS processing unit 12A. In response to this, the GPS processing unit 12A specifies the elevation angle of each GPS satellite 9 and the stay time after the current time of each GPS satellite 9 in the field of view as viewed from the current position based on the almanac data.

  Next, in the same manner as the above selection process, the GPS processing unit 12A, as shown in FIG. 5, the five GPS satellites 9k, 9d, 9i, 9b, After selecting 9c in this order, the three GPS satellites 9g, 9j, and 9a are selected from the other GPS satellites 9 other than these five GPS satellites 9 in the order of the longer staying time. Next, the GPS processing unit 12A receives the respective GPS signals Sg output from the selected eight GPS satellites 9, acquires the ephemeris data for each GPS satellite 9, and uses the ephemeris data. The current position is measured and position data Dp is output. Thereafter, similarly to the cellular phone 1, the control unit 15A generates the image data Dg and outputs it to the display unit 16, and the display unit 16 displays an image based on the image data Dg. Also in this cellular phone 1A, since both the GPS satellite 9 having a large elevation angle and the GPS satellite 9 having a long stay time can be used for positioning the current position, the current position can be measured with high accuracy and in a short time. Can do.

  Moreover, although the example in which the radio base station 2 executes the selection process of the GPS satellite 9 has been described above, a configuration in which the information server 3 executes the selection process may be employed. In this configuration, the GPS processing unit 33 of the information server 3 (in this case, the GPS processing unit 33 corresponds to the satellite selection unit in the present invention) performs the assist data Da generation processing in the same manner as the selection processing described above. For example, eight GPS satellites 9 (GPS satellites 9a-9d, 9g, 9i-9k shown in the figure) are selected from among 11 GPS satellites 9 (GPS satellites 9a-9k shown in FIG. 5). . Next, the GPS processing unit 33 generates assist data Da including orbit information for the eight selected GPS satellites 9. On the other hand, when the transmission request signal S2 is transmitted from the wireless base station 2, the control device 34 of the information server 3 outputs assist data Da including orbit information about the eight GPS satellites 9, and the wireless base station 2 The station 2 transmits the assist data Da to the mobile phone 1 without executing the above extraction process. Also in this configuration, since both the GPS satellite 9 having a large elevation angle and the GPS satellite 9 having a long stay time can be used for positioning the current position, the current position can be accurately and shortly determined with respect to the mobile phone 1. It can be measured with.

Further, although an example in which eight GPS satellites 9 are selected from eleven GPS satellites 9 has been described above, it is needless to say that these numbers can be defined as arbitrary numbers. Further, the number of GPS satellites 9 to be selected in descending order of elevation angle and the number of GPS satellites 9 to be selected in order of long residence time are not limited to the above-mentioned 5 and 3 (or 3 and 5), Can be specified in numbers. In addition, the mobile phone 1 and the mobile phone 1A as mobile terminals have been described as examples. However, the mobile terminal in the present invention is not limited to this, but a pager (registered trademark) type mobile terminal or a PDA (Personal Digital) Various types of mobile terminals having positioning functions such as assistant type mobile terminals are included. For example, the present invention can be applied to a position monitoring system that monitors the position of the mobile phone 1 by transmitting the position data Dp to the mobile phone 1.

1 is a block diagram showing a configuration of an information transmission system 10. FIG. 1 is a block diagram showing a configuration of a mobile phone 1. FIG. 2 is a block diagram showing a configuration of a radio base station 2. FIG. 2 is a block diagram showing a configuration of an information server 3. FIG. It is a list figure which shows the elevation angle of GPS satellites 9a-9k, stay time, and selection order. It is explanatory drawing for demonstrating the positional relationship of the radio base station 2 and GPS satellites 9a-9k. It is a list figure which shows the selection order in the elevation angle of GPS satellites 9a-9k, stay time, and another satellite selection method.

Explanation of symbols

  1, 1A mobile phone, 2 radio base station, 3 information server, 9a to 9k GPS satellite, 10 information transmission system, 12A GPS processing unit, 24 control unit, 33 GPS processing unit, Da assist data, Sg GPS signal

Claims (5)

When a mobile terminal having N (N is a natural number greater than or equal to 5 ) channels of a signal processing circuit for positioning signals determines the current position, N terminals are used for positioning from among a plurality of positioning satellites that transmit the positioning signals. A satellite selection method for selecting a positioning satellite of
M positioning satellites (M is a natural number of 4 or more and less than N) are selected from the positioning satellites in descending order of elevation angle, and the positioning satellites other than the M positioning satellites are selected. The satellite selection method of selecting (NM) positioning satellites in descending order of the stay time after the current time in the field of view as viewed from the current position. When a mobile terminal having N (N is a natural number greater than or equal to 5 ) channels of a signal processing circuit for positioning signals determines the current position, N terminals are used for positioning from among a plurality of positioning satellites that transmit the positioning signals. A satellite selection method for selecting a positioning satellite of
M positioning satellites (M is a natural number of 4 or more and less than N) are selected from the positioning satellites in order of increasing residence time after the current time in the field of view as viewed from the current position, and the M number of positioning satellites are selected. A satellite selection method for selecting (NM) positioning satellites in descending order of elevation from the other positioning satellites other than the positioning satellites. A signal processing circuit for positioning signals for N (N is a natural number of 5 or more) channels, and N positioning satellites used for positioning of the current position among a plurality of positioning satellites that transmit the positioning signals. A mobile terminal comprising: a satellite selection unit to select; and a positioning unit that measures the current position based on the positioning signals respectively transmitted from the N positioning satellites,
3. The mobile terminal that selects the N positioning satellites according to the satellite selection method according to claim 1. A satellite selection unit that selects N positioning satellites (N is a natural number of 5 or more) used for positioning of the current position from among a plurality of positioning satellites that transmit positioning signals, and includes signals for positioning signals An information server that has N processing circuits and provides orbit information about the N positioning satellites to a mobile terminal that measures the current position by processing the positioning signals separately in each channel. There,
3. The information server for selecting the N positioning satellites according to the satellite selection method according to claim 1 or 2. An information server that generates each orbit information for a plurality of positioning satellites that transmit positioning signals and a signal processing circuit for positioning signals are provided in N (N is a natural number of 5 or more) channels, and each channel has a separate signal processing circuit. An information transmission system comprising: a radio base station that performs signal processing of a positioning signal and transmits the orbit information to a mobile terminal that measures the current position,
The radio base station selects N positioning satellites used for positioning of the current position from the positioning satellites at the time of transmission of the orbit information, and orbits for the N positioning satellites. A transmission control unit that extracts information from each orbit information and is a transmission target,
The information transmission system, wherein the transmission control unit selects the N positioning satellites according to the satellite selection method according to claim 1.

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