Portable Terminal, Base Station, and Method of Specifying Position of Portable Terminal

• US 20100222075A1
• Filed: 09/26/2008
• Published: 09/02/2010
• Est. Priority Date: 09/26/2007
• Status: Active Grant

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Corporation
• Inventors: Miura, Takanori
• Granted Patent: US 8,326,363 B2
• Time in Patent Office: Days
• US Class Current: 455/456.100
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

A portable terminal is provided, which includes a communication unit that transmits/receives a signal modulated by a predetermined modulation method to/from three or more base stations; a storage unit which stores in advance a plurality of propagation models indicating propagation environments of the signal for respective combinations of the base stations and stores in advance position information of the base stations; and a control unit that controls the communication unit and the storage unit; wherein the control unit specifies a propagation model that corresponds to a combination of the base stations among the plurality of propagation models stored in the storage unit based on the signal and calculates communicable distances of the signal based on the corresponding propagation model, calculates circles having the corresponding communicable distances as their radii and having positions of the base stations as their centers, respectively, obtains an overlapping area where the circles overlap one another, and specifies the center position of the overlapping area as the position of the portable terminal.

Claims

1. A portable terminal comprising:

a communication unit that transmits/receives a signal modulated by a predetermined modulation method to/from three or more base stations;

a storage unit which stores in advance a plurality of propagation models indicating propagation environments of the signal for respective combinations of the base stations and stores in advance position information of the base stations; and

a control unit that controls the communication unit and the storage unit;

wherein the control unit specifies a propagation model that corresponds to a combination of the base stations among the plurality of propagation models stored in the storage unit based on the signal and calculates communicable distances of the signal based on the corresponding propagation model, calculates circles having the corresponding communicable distances as their radii and having positions of the base stations as their centers, respectively, obtains an overlapping area where the circles overlap one another, and specifies the center position of the overlapping area as the position of the portable terminal.

2. The portable terminal according to claim 1, wherein if the overlapping area does not exist, the control unit changes the specified propagation model to another propagation model among the plurality of propagation models stored in the storage unit, obtains the overlapping area based on the corresponding propagation model, and stores the corresponding propagation model in the storage unit.

3. The portable terminal according to claim 1, wherein the communication unit transmits/receives the signal of which the modulation method is changed according to the communication state to/from the base stations;

and

the control unit calculates a concentric circle which is smaller than the circles and has a communicable distance based on the modulation method having a communicable range that is narrower than that of the modulation method of the signal as its radius, and limits the overlapping area by the concentric circle.

4. The portable terminal according to claim 1, wherein the communication unit performs transmission/reception of the signal with one of the base stations through a communication channel, and performs transmission/reception of the signal with other base stations through a control channel.

5. A portable terminal comprising:

a communication unit that transmits/receives a first signal of which the modulation method is changed according to a communication state to/from a first base station and transmits/receives a second signal of which the modulation method is fixed to/from a plurality of second base stations that are different from the first base station; and

a control unit that specifies its own position based on the first and second signals;

wherein the control unit calculates a first communicable distance that is the current communicable distance of the first signal, and calculates a first circle which has the corresponding first communicable distance as its radius and has the first base station as its center;

calculates a second communicable distance from the modulation method having a communicable distance that is shorter than that of the current modulation method of the first signal, and calculates a second circle which has the corresponding second communicable distance as its radius and has the first base station as its center;

calculates a third circle which has a third communicable distance between the first communicable distance and the second communicable distance as its radius and has the first base station as its center;

calculates a fourth communicable distance that is the communicable distance of the second signal, and calculates a plurality of fourth circles which have the corresponding fourth communicable distance as their radii and have the second base station as their centers, respectively; and

changes the communicable distance of the first signal from the first communicable distance to the third communicable distance by a process of changing the communicable distance, and if the communication unit is able to transmit/receive the first signal of which the communicable distance has become the third communicable distance, specifies the center of an overlapping area between an area surrounded by the second circle and the third circle and the fourth circle as its position, while if the communication unit is unable to transmit/receive the first signal of which the communicable distance has become the third communicable distance, specifies the center of an overlapping area between an area surrounded by the first circle and the third circle and the fourth circle as its position.

6. The portable terminal according to claim 5, wherein the control unit changes the bandwidth of the first signal or changes the bandwidth and a modulation method of the first signal by the process of changing the communicable distance.

7. The portable terminal according to claim 5, wherein the communication unit has an adaptive array antenna composed of a plurality of antenna elements;

and

the control unit reduces the number of antenna elements of the communication unit that is used in transmission/reception of the first signal, or reduces the number of antenna elements of the communication unit that is used in transmission/reception of the first signal and changes the modulation method of the first signal as the communicable distance change processing.

8. The portable terminal according to claim 5, wherein the first signal is a signal that is transmitted/received through the communication channel, and the second signal is a signal that is transmitted/received through the control channel.

9. A base station that transmits/receives a signal modulated by a predetermined modulation method to/from a portable terminal communicating with three or more base stations, the base station comprising:

a communication unit that transmits/receives the signal to/from the portable terminal;

a storage unit which stores in advance a plurality of propagation models indicating propagation environments of the signal that the portable terminal transmits/receives for respective combinations of the base stations with which the portable terminal communicates, and stores in advance position information of the base stations; and

a control unit that controls the communication unit and the storage unit;

wherein the control unit acquires communication information about the base stations with which the portable terminal communicates through the communication unit and a modulation method of the signal in the communication from the portable terminal, specifies a propagation model which corresponds to a combination of the base stations with which the portable terminal communicates and is stored in the storage unit based on the corresponding communication information and the signal that the communication unit transmits to or receives from the portable terminal and calculates communicable distances of the signal that the portable terminal transmits to or receives from the respective base stations based on the corresponding propagation model, calculates circles having the corresponding communicable distances as their radii and having positions of the base stations as their centers, respectively, obtains an overlapping area where the circles overlap one another, and specifies the center position of the overlapping area as the position of the portable terminal.

10. The base station according to claim 9, wherein if the overlapping area does not exist, the control unit changes the specified propagation model to another propagation model, obtains the overlapping area based on the corresponding propagation model, and stores the corresponding propagation model in the storage unit.

11. The base station according to claim 9, wherein the communication unit transmits/receives the signal of which the modulation method is changed according to the communication state to/from the portable terminal;

and

the control unit calculates a concentric circle which is smaller than the circles and has the communicable distance based on the modulation method having a communicable range that is narrower than that of the modulation method of the signal as its radius, and limits the overlapping area by the concentric circle.

12. A first base station that transmits/receives a first signal to/from a portable terminal which transmits/receives the first signal of which the modulation method is changed according to a communication state to/from the first base station and transmits/receives a second signal of which the modulation method is fixed to/from other second base stations that are different from the first base station, the first base station comprising:

a communication unit that transmits/receives the first signal to/from the portable terminal; and

a control unit that specifies a position of the portable terminal based on the first signals;

wherein the control unit acquires communication information about communication of the portable terminal with the second base stations from the first signal that the communication unit receives from the portable terminal;

calculates a first communicable distance that is the current communicable distance of the first signal, and calculates a first circle which has the corresponding first communicable distance as its radius and has the first base station as its center;

calculates a second communicable distance from the modulation method having a communicable distance that is shorter than that of the current modulation method of the first signal, and calculates a second circle which has the corresponding second communicable distance as its radius and has the first base station as its center;

calculates a third circle which has a third communicable distance between the first communicable distance and the second communicable distance as its radius and has the first base station as its center;

calculates a fourth communicable distance that is the communicable distance of the second signal based on the communication information, and calculates a plurality of fourth circles which have the corresponding fourth communicable distance as their radii and have the second base station as their centers, respectively; and

changes the communicable distance of the first signal from the first communicable distance to the third communicable distance by a process of changing the communicable distance, and if the first signal of which the communicable distance has become the third communicable distance is able to be transmitted to or received from the portable terminal, specifies the center of an overlapping area between an area surrounded by the second circle and the third circle and the fourth circle as the position of the portable terminal, while if the first signal of which the communicable distance has become the third communicable distance is unable to be transmitted to or received from the portable terminal, specifies the center of an overlapping area between an area surrounded by the first circle and the third circle and the fourth circle as the position of the portable terminal.

13. The base station according to claim 12, wherein the control unit changes the bandwidth of the first signal or changes the bandwidth and a modulation method of the first signal by the process of changing the communicable distance.

14. The base station according to claim 12, wherein the communication unit has an adaptive array antenna composed of a plurality of antenna elements;

and

the control unit reduces the number of antenna elements of the communication unit that is used in transmission/reception of the first signal, or reduces the number of antenna elements of the communication unit that is used in transmission/reception of the first signal and changes the modulation method of the first signal.

15. A method of specifying the position of a portable terminal that transmits/receives a signal in which a predetermined modulation method is used to/from three or more base stations, the method comprising:

based on the signal that the portable terminal transmits to or receives from the base stations, calculating communicable distances based on a propagation model and the modulation method;

calculating a plurality of circles having the corresponding communicable distances as their radii and having the positions of the base stations as their centers, respectively;

obtaining an overlapping area where the circles overlap one another; and

specifying the center position of the overlapping area as the position of the portable terminal.

16. A method of specifying the position of a portable terminal that transmits/receives a first signal of which the modulation method is changed according to a communication state to/from a first base station and transmits/receives a second signal of which the modulation method is fixed to/from a plurality of second base stations that are different from the first base station, the method comprising:

calculating a first communicable distance that is the current communicable distance of the first signal, and calculating a first circle which has the corresponding first communicable distance as its radius and has the first base station as its center;

calculating a second communicable distance from the modulation method having a communicable distance that is shorter than that of the current modulation method of the first signal, and calculating a second circle which has the corresponding second communicable distance as its radius and has the first base station as its center;

calculating a third circle which has a third communicable distance between the first communicable distance and the second communicable distance as its radius and has the first base station as its center;

calculating a fourth communicable distance that is the communicable distance of the second signal, and calculating a plurality of fourth circles which have the corresponding fourth communicable distance as their radii and have the second base station as their centers, respectively; and

changing the communicable distance of the first signal from the first communicable distance to the third communicable distance by a process of changing the communicable distance, and if the portable terminal is able to transmit/receive the first signal of which the communicable distance has become the third communicable distance, specifying the center of an overlapping area between an area surrounded by the second circle and the third circle and the fourth circle as the position of the portable terminal, while if the portable terminal is unable to transmit/receive the first signal of which the communicable distance has become the third communicable distance, specifying the center of an overlapping area between an area surrounded by the first circle and the third circle and the fourth circle as the position of the portable terminal.