JP2001083231A - Position information system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately obtain position information of a portable terminal by a bi-directional terminal. SOLUTION: According to the position information system, a position of a portable terminal 1 such as a PHS, a portable phone or the like is located from a distance between the terminal 1 and a plurality of base stations 2 by measuring a wave propagation time between the terminal 1 and the base station 2 with the utilization of pulse code modulation used in a CDMA system of the terminal 1. Since the PHS or portable phone using pulse code modulation is employed as the portable terminal whose position information is to be obtained, the portable terminal can be used in a building or underground shopping center so long as the base station 2 is present in the neighborhood. Since the terminal 1 is bi-directional, position information of the terminal 1 can be obtained from a remote place with reduced position errors. Since both the terminal 1 and the base station 2 can utilize existing systems, the position information system can be constructed at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a PHS (Personal)
The present invention relates to a position information system that specifies a current position of a mobile terminal by using an interactive mobile terminal such as a handy phone system or a mobile phone.

[0002]

2. Description of the Related Art Conventional location information systems include GPS.
(Global Positioning System). The GPS system receives radio waves from multiple GPS satellites, measures the time the radio waves reach the mobile terminal receiving from each satellite, calculates the distance, and calculates the current position of the mobile terminal based on the principle of triangulation. It is.

Further, a position information system using a portable terminal such as a PHS or a portable telephone has already been used. These are systems that estimate the position of the mobile terminal from the position of the base station that has received the radio wave from the mobile terminal and use the information as position information, or a system that obtains the position information in combination with GPS. The problem of the location information system using mobile terminals is to make mobile terminals low cost. It can be used inside buildings and underground malls. Low position error. The location information of the mobile terminal can be obtained from a remote location. That is.

FIG. 4 is a diagram showing the configuration of a conventional location information system using GPS. In FIG.
A satellite, 6 is a portable terminal for receiving a radio wave from the satellite, and M is a radio wave. In the position information system using GPS, the mobile terminal 6 receives a radio wave M from the GPS satellite 5. The radio wave M includes an identification signal of the GPS satellite 5, a position of the satellite 5, and a signal capable of measuring a radio wave arrival time from the satellite 5. Accordingly, when the mobile terminal 6 receives the radio wave M from the GPS satellite 5, the distance between the GPS satellite 5 and the mobile terminal 6 can be calculated from the arrival time of the radio wave M. Therefore, if the radio waves M from three or more different GPS satellites 5 can be received, the position information of the portable terminal 6 can be obtained using the principle of triangulation. In this case, the owner of the portable terminal 6 can know his / her own position information, but cannot transmit the position information to another person who is away.

FIG. 5 is a diagram showing a configuration of a position information system using a conventional PHS for a portable terminal. In FIG. 5, reference numeral 1 denotes a portable terminal, and reference numeral 2 denotes a base station for transmitting and receiving radio waves P to and from the portable terminal. . The location information system using the PHS portable terminal 1 includes a "one-station system" that uses only the location information of the base station, location information by combining the location information of a plurality of base stations, and the electric field strength between the portable terminal and the base station. There is a “field strength method” that obtains Since the radio wave output of the PHS base station 2 is very small, 20 mW to 500 mW, one base station 2 and one portable terminal 1
The communicable range is about 100 to 500 m in radius. Therefore, in the PHS, position information can be obtained by setting the position of the communicating base station 2 to the position of the mobile terminal 1. This is the "one-station system".

However, since the position is not the position of the portable terminal but the position of the base station, the accuracy is about 500 m or less. The “field strength method” uses position information of a plurality of base stations in order to improve the position accuracy more than the one-station method. One base station 2 that has captured radio waves transmitted from the PHS mobile terminal 1 requests a plurality of peripheral base stations 2 to measure the radio field intensity of the same PHS mobile terminal 1. In this way, the radio wave intensities measured by the plurality of base stations 2 are weighted so as to be closer to the position of the base station 2 having a higher intensity, thereby improving the accuracy of the position information. The control of the base station 2, the base station 2
Is managed in the center 3. Information is provided to the monitor terminal 4 of the distant person via the center 3.

When the transmission power is as large as several tens of watts as in the case of the base station 2 of a portable telephone, the base station 2 is constructed in the same manner as the PHS.
The method of considering the position of the mobile terminal 1 as the position of the mobile terminal 1 cannot be established because the distance that one base station 2 can communicate with the mobile terminal 1 is as large as several km.

Therefore, in the position information system in which the portable telephone is the portable terminal 1, as shown in FIG. 6, the portable telephone incorporates the GPS receiving terminal 6, or the portable telephone 1 and the GPS receiving terminal 6 are connected to each other. Is measured by radio waves from the GPS satellite 5 to obtain position information. Information is provided to the remote person via the center 3 to the monitor terminal 4. As described above, when the PHS and the mobile phone are mobile terminals, the bidirectional communication function of the mobile terminal allows the location information of the mobile terminal to be transmitted to a remote person.

[0009]

In the conventional position information system using only the GPS receiving portable terminal 6, the position information cannot be transmitted to others. It cannot be used unless it can receive radio waves from multiple GPS satellites. GPS satellites are operated by the U.S. government, and the accuracy of distance measurement signals is being manipulated due to changes in the world situation, and does not guarantee a certain degree of accuracy. There was such a problem.

The position information system using the PHS as the portable terminal 1 basically has a problem that the position accuracy is poor because the position of the base station 2 is the position of the portable terminal 1.

In a position information system using a portable telephone as a portable terminal, the position of the base station cannot be taken as the position of the terminal, the position accuracy cannot be obtained, and the system is combined with a GPS receiving terminal or the like. . There was a problem that it had to receive radio waves from GPS satellites.

The present invention has been made in order to solve the above-described problems, and has focused on the fact that the CDMA (code division multiple access) system has begun to be used in PHS or portable telephones.
No need for GPS satellites due to code-modulated radio waves,
An object of the present invention is to provide a low-cost position information system because position information can be obtained with high accuracy, position information of a portable terminal can be sent to a remote place, and addition of a circuit to the portable terminal is almost unnecessary.

[0013]

A position information system according to a first aspect of the present invention measures a radio wave propagation time between a terminal and a base station by using code modulation used in a PHS or a CDMA system of a mobile phone. And from the distance between the terminal and multiple base stations,
This allows the position of the terminal to be specified.

In the position information system according to the second invention, a distance obtained from a base station having a high received signal strength is defined as a distance within a code length, and the distance obtained from a base station having a low received signal strength corresponds to the code length. The distance to be added is added to determine the position, and the base station receives the ambiguity of the distance that may occur when measuring the distance by using the code modulation method,
This is removed based on the electric field strength information.

A position information system according to a third aspect of the present invention is such that a base station having a function of measuring the angle of arrival of a signal from a terminal can specify the position of the terminal alone.

A position information system according to a fourth invention is the position information system according to the first to third inventions, wherein a signal delay is automatically transmitted to a base station in a terminal used for calculating a distance. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a configuration diagram of a position information system showing the first embodiment, and FIG. 2 is a diagram showing a distance measurement method. In the figure, 1 is a mobile terminal, 2
Is a base station, 3 is a center, and 4 is a monitor terminal.

1 and 2 show the operation in the first embodiment. As shown in FIG. 1, when communicating with another portable terminal 1, the portable terminal 1 communicates via a base station 2 and a center 3 which performs communication network / position information management. In addition, a monitor terminal 4 for monitoring the position information of the mobile terminal 1 is connected to the center 3 from a place remote from the mobile terminal 1.
These configurations use the conventional configuration as it is. However, in the present invention, the mobile terminal 1 and the base station 2
Focusing on the fact that code modulation has begun to be used for communication radio waves P with the mobile terminal 1 and a plurality of base stations 2
Is accurately measured to estimate the position information of the mobile terminal 1.

In the code modulation, the communication radio wave P is represented by a code as shown in FIG. 2 as an example (the illustrated code has a chip number of 21 for explanation of the principle, but the normal code length is Longer) to spread the spectrum. The codes are generated according to a certain rule, and different codes are assigned to the mobile terminals used in the service area of one base station. Therefore, when it is desired to obtain position information of a specific terminal, the base station 2 transmits a radio wave P to the terminal, demodulates a response signal from the mobile terminal 1, and detects how many codes have shifted, thereby obtaining a base station. The distance R between the station 2 and the portable terminal 1 can be measured with an error within the width of the chip length. A chip is a unit time when a digital code is used for modulation. Distance R between base station and mobile terminal
(m) is obtained as follows.

R = C / 2 * (t3 t1 T2) (1) C is the speed of light 300 (m / μs) t3 Time when radio waves are received by the base station (μs) t1 Time when radio waves are transmitted from the base station ( μs) T2 Delay time on mobile terminal (μs)

R = C / 2 * (T1 + T3 + T2-T2) (2) T1 = T3 Radio wave arrival time between terminal and base station

R = ts * N * 150 T2 * 150 (m) (3) ts (μs) The chip length N The number of codes shifted by ts is determined by the modulation, and T2 is the adjustment of the mobile terminal or
Since it is known by measurement, by measuring N, the distance between the terminal 1 and the base station 2 is measured.

Further, since the measurement accuracy depends on the chip length, the cost-effectiveness can be increased by appropriately selecting it according to the application. For example, if the chip length is 0.1 μs, the accuracy is about 15 m. Similarly, by measuring the distance from three or more base stations 2 to the same mobile terminal 1 and utilizing the principle of triangulation, the position of the mobile terminal 1 can be specified. The information can be known at the monitor terminal 4 via the center 3. Although the terminal has been described as a portable terminal, it is needless to say that the position of a fixed terminal can be similarly measured.

Further, assuming that the transmission and reception code codes are the same,
As described above, a different code may be used as long as the code of the partner is known and synchronization is achieved.

Embodiment 2 The operation of the second embodiment of the present invention will be described. The previous section shows that the distance between the mobile terminal 1 and the base station 2 is obtained. For example, when the chip length is 0.05 μs and the number of chips in the code frame length tf is 1023,
Distance measurement accuracy is improved to about 7.5m, but about 7.7km
The ambiguity of the distance measurement is generated from the radio wave of the mobile terminal 1 received over the distance, because the same code is used every 1023. However, the service area of the PHS or the mobile phone of the base station 2 is usually within a few km, and the power is controlled in order to prevent interference with others.
In all of the cases, a signal at a long distance is received, and there is no case where ambiguity occurs in all of the measurements.

Therefore, if an intersection cannot be obtained within a range in which a measurement error is considered according to the principle of triangulation in FIG. 3, the distance obtained from the base station having the strongest reception strength is set to the distance within the code length. By adding the distance corresponding to the code length to the distance obtained from the base station 2 having a weak reception strength, the position can be specified. Thus, the position can be specified without adding a circuit.

Embodiment 3 The current base station has terminal 1
It does not have a function to obtain the angle-of-arrival signal of a radio wave from, but when CDMA mobile terminals are used, terminals in the same service area use the same frequency simultaneously.
Therefore, in order to reduce interference, a plurality of antennas of the base station are used, and a beam is directed to a specific terminal 2. This is possible using a known technique such as DBF (Digital Beam Forming).

As described above, if the radio wave arrival angle of the terminal 1 can be measured, the position of the terminal can be specified by a single base station by using it together with the distance measurement of the first embodiment of the present invention.

Embodiment 4 In the first to third embodiments, in order to measure the distance between the terminal 1 and the base station 2, it is necessary to know the delay T2 inside the terminal 2. Although it is possible to adjust the terminal to a constant value, it is possible to measure the delay at the time of manufacture or the like, and to send the value to the base station 2 from the terminal in response to a request or periodically, thereby achieving high accuracy. Distance correction becomes possible.

[0030]

As described above, according to the present invention, a PHS or a mobile phone using code modulation is used as a mobile terminal for obtaining location information. It can be used in underground shopping malls, has small positional errors, and has bi-directional terminals, so you can obtain terminal location information even from distant locations.You can use existing systems for both terminals and base stations, so you can build at low cost There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a position information system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a distance measuring method according to the present invention.

FIG. 3 is a diagram showing a correction method for distance measurement according to the present invention.

FIG. 4 is a diagram showing a configuration diagram of a conventional position information system using GPS.

FIG. 5 is a diagram showing a configuration diagram of a conventional position information system using PHS.

FIG. 6 is a diagram showing a configuration diagram of a conventional location information system using a mobile phone.

[Explanation of symbols]

1 Mobile terminal, 2 base station, 3 center, 4 monitor terminal, 5 GPS satellite, 6 Mobile terminal for GPS.

Claims (4)

[Claims] An apparatus comprising: a bidirectional terminal using a CDMA (code division multiple access) system; and a plurality of base stations, wherein a base station and a terminal are determined based on a propagation time of a code-modulated radio wave between the terminal and the base station. A position information system characterized by measuring a distance between the terminals and specifying a position of the terminal. 2. A distance obtained from a base station having high received signal strength is defined as a distance within a code length, and a distance corresponding to the code length is added to a distance obtained from a base station having low received signal strength to determine a position. 2. The position information system according to claim 1, wherein the position information is specified. 3. The position information system according to claim 1, wherein a function of measuring an angle of arrival of a radio wave from the terminal is provided in the base station so that the position of the terminal can be specified by a single base station. 4. A position information system, wherein delay information of a signal in a terminal is sent to a base station to correct measurement distance accuracy.