KR100277036B1 - Apparatus and method for tracking a location of a mobile station in a mobile communication system using a code division multiple access scheme - Google Patents

Abstract

end. TECHNICAL FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a service method of a mobile communication system, and more particularly, to an apparatus and method for tracking a location of a mobile station.

I. Technical Problems to be Solved by the Invention

An apparatus and method for measuring the phase difference of tone signals transmitted from neighboring base stations from neighboring base stations on the basis of an absolute system time and calculating position information of the base station using the measured phase difference information and the position information of each base station Provided.

All. The point of the solution of the invention

The mobile station measures the phase difference of the tone signals transmitted from neighboring base stations at different time points on the basis of the absolute system time and calculates its own position information using the measured phase difference information and the position information of each base station

la. Important Uses of the Invention

Prevent unnecessary power consumption of mobile station and provide continuous location tracking service by mobile station's demand.

Description

Apparatus and method for tracking a location of a mobile station in a mobile communication system using a code division multiple access scheme

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a service method of a mobile communication system, and more particularly, to an apparatus and method for tracking a location of a mobile station.

The IS-95B (Interim Standard), a wireless access standard proposed as a Code Division Multiple Access (CDMA) system, provides a location tracking service for a mobile station. According to the PUF (Power Up Function) of the IS-95B, a plurality of base stations measure a propagation delay time of a signal transmitted from a mobile station and determine a position of the mobile station through mutual interoperation between base stations. Further, the propagation delay time can be measured through a chip delay analysis of a PN sequence transmitted from a mobile station via a wireless communication path.

Meanwhile, in a CDMA mobile communication system, a base station generates a base time reference (System Reference Time) using a GPS (Global Positioning System). Also, the mobile station matches the reference time of the base station with the reference time of the mobile station in order to synchronize with the base station. That is, when the mobile station is powered on, the mobile station receives a pilot channel and a synchronization channel transmitted from the base station and acquires an initial synchronization acquisition (hereinafter, referred to as " initial synchronization acquisition ") in which the PN sequence is matched with a pseudo- Acquisition) operation.

However, due to the characteristics of the mobile communication itself, the reference time of the mobile station and the reference time of the base station basically have a time difference equal to the propagation delay. That is, the reference time of the mobile station is slower than the reference time of the base station by the propagation delay time. This is because, when the PN sequence of the base station is transmitted to the mobile station through the wireless communication path, the mobile station synchronizes its PN sequence with the PN sequence of the base station already having undergone the propagation delay. The propagation delay time is caused by the distance between the mobile station and the base station, and is represented as a function of time due to changes in channel conditions such as mobile station movement.

Meanwhile, in the CDMA mobile communication system, the propagation delay time can be measured by analyzing a chip delay of a PN sequence received through a wireless communication path. Generally, the mobile station adjusts its reference time through analyzing the chip delay of the PN sequence transmitted from the base station (hereinafter, the amount of time the mobile station adjusts its reference time is referred to as " mobile station reference time adjustment amount "). This is to maintain the PN sequence synchronization between the mobile station and the base station by compensating the chip delay caused by the propagation delay.

However, the PN sequence of the mobile station itself is basically a delay of a predetermined number of chips as compared with the PN sequence of the base station. This is because the PN sequence of the initially synchronized mobile station and the PN sequence of the base station are basically different due to the propagation delay occurring in the initial synchronization acquisition operation as described above.

If the mobile station transmits a message including its own PN sequence to the base station and the base station measures the propagation delay time of the message and transmits the propagation delay time information to the mobile station again from the time when the message is transmitted, It is possible to obtain the reference time of the base station at the time when the propagation delay time information is received, that is, the current time, using the mobile station reference time adjustment amount up to the time when the delay time information is received. Herein, the obtained reference time of the base station is the reference time of the actual base station before the propagation delay as compared with the reference time of the mobile station. (Hereinafter, the reference time of the base station before the propagation delay is referred to as "absolute system time"

1 is a diagram illustrating a conventional location tracking service procedure.

The serving base station transmits a PUF message in a traffic channel control state to acquire location information of the mobile station. When the PUF message is received, the mobile station transmits the PUF pulse to the service base station while gradually increasing the transmission power level. The mobile station simultaneously transmits the PUF pulse to nearby base stations (not shown). At this time, since the distance between the mobile station and neighboring base stations is relatively long, the mobile station transmits a PUF pulse to the neighboring base stations at a power much higher than the transmission power level in communication with the serving base station. The serving base station and neighboring base stations measure the propagation delay time of the received PUF pulse and calculate the position information of the mobile station through the interlocking operation. When the calculation of the mobile station location information is completed, the serving base station transmits a PUF complete message to the mobile station. The PUF completion message includes latitude, longitude, and measurement time information of the mobile station. At this time, the mobile station stops the PUF pulse transmission operation. The serving base station transmits the mobile station position information to the mobile station.

However, as described above with reference to FIG. 1, in the conventional position tracking method, the position of a mobile station can be tracked only by a request of a base station in a call state. That is, since it is possible to track the location of a mobile station only during a call, continuous service is impossible. In response to the PUF message of the base station, the mobile station transmits a PUF pulse to neighboring base stations that are not currently connected. At this time, when the mobile station transmits the PUF pulse to neighboring base stations, the mobile station uses a power much higher than the transmission power level in communication with the serving base station. As a result, the interference of the reverse link increases, and the increase of the interference may cause a problem in the reverse link power control. This also reduces the talk capacity of the reverse link and causes power consumption of the mobile station.

As described above, the disadvantage of the conventional mobile station position tracking method is due to the increase of the interference of the reverse link according to the PUF pulse transmitted from the mobile station to neighboring base stations. If the mobile station can measure the phase difference according to the propagation delay of the tone signals transmitted from neighboring base stations, the mobile station can calculate its own location information using the location information of nearby base stations without transmitting the PUF pulse. At this time, the mobile station must know the absolute system time of the base station as a measurement reference in order to measure the propagation delay of the tone signals.

Accordingly, it is an object of the present invention to provide an apparatus and a method for calculating position information of a mobile station in accordance with a request from the mobile station.

It is another object of the present invention to provide an apparatus and method for a mobile station to calculate its own location information using phase delays of tone signals transmitted from nearby base stations and location information of nearby base stations.

It is still another object of the present invention to provide a mobile station which measures phase differences of tone signals transmitted from neighboring base stations at neighboring base stations on the basis of an absolute system time, And an apparatus and method for calculating information.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, an apparatus for tracking a location of a mobile station in a mobile communication system using a CDMA scheme includes an absolute system time acquisition and maintenance unit for acquiring and maintaining an absolute system time, A tone phase detector for measuring a phase difference according to a propagation delay of each of the transmitted tone signals on the basis of the absolute system time and a phase difference detector for detecting a phase difference between the measured tone signals and the position information of the plurality of base stations, And a mobile station position calculator for calculating position information of the mobile station.

A method for tracking a location of a mobile station in a mobile communication system using a code division multiple access scheme includes a first step of acquiring and maintaining an absolute system time and a second step of acquiring and maintaining a phase difference according to a propagation delay of each tone signal transmitted from a plurality of base stations And a third step of calculating positional information of the mobile station by using the phase difference of the measured tone signals and the positional information of the plurality of base stations, .

1 illustrates a conventional location tracking service procedure;

FIG. 2 is a time-axis diagram illustrating a process in which nearby base stations periodically transmit their tone signals to a mobile station at different points in time according to an embodiment of the present invention;

3 is a diagram illustrating a phase difference from an absolute system time generated by a propagation delay when adjacent base stations transmit their tone signals to a mobile station according to an embodiment of the present invention.

4 is a diagram illustrating a process of calculating the location information of a mobile station using phase difference information transmitted from neighboring base stations and location information of neighboring base stations according to an embodiment of the present invention.

FIG. 5 is a time axis view illustrating a concept that a mobile station acquires an absolute system time of a base station according to an embodiment of the present invention; FIG.

FIG. 6 is an internal configuration view of a mobile station and a base station for acquiring an absolute system time of a mobile station according to an embodiment of the present invention; FIG.

FIG. 7 is a flowchart illustrating a method of acquiring and maintaining an absolute system time of a mobile station according to an embodiment of the present invention; FIG.

8 is a diagram illustrating an internal structure of a mobile station and neighboring base stations for the mobile station to calculate its own location information according to an embodiment of the present invention.

9 is a flowchart illustrating a method of tracking a location of a mobile station according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In order to calculate the location information of the mobile station according to the present invention, the mobile station measures the phase delay of the tone signal transmitted from neighboring base stations and obtains the distance to each base station. At this time, neighboring base stations periodically transmit their tone signals with a predetermined time interval. Also, the neighboring base stations transmit their tone signals to the mobile stations at different points in time in order to prevent inter-modulation between the tone signals. Also, the tone signals may have the same frequency or different frequencies.

FIG. 2 is a diagram illustrating, on a time axis, a process in which adjacent base stations periodically transmit their tone signals to mobile stations at different points in time according to an embodiment of the present invention.

Here, the horizontal axis represents the elapsed time of the absolute system time. The first base station tone signal 210 to the N-th base station tone signal 2N0 are frequency- f ₁ Frequency f _N . The tone period 211 is a period of each of the tone signals and the total period 212 is a period which is a sum of the periods of the first base station tone signal 210 to the Nth base station tone signal 2N0.

FIG. 3 is a diagram illustrating a phase difference from an absolute system time generated by a propagation delay when adjacent base stations transmit their tone signals to a mobile station according to an embodiment of the present invention. Hereinafter, description will be given with reference to FIG.

Here, the horizontal axis represents elapsed time of the mobile station reference time. The first base station tone signal 210 to the N < th > base station tone signal 2N0 are transmitted to the mobile station. At this time, the respective tone signals undergo a propagation delay according to the distance between the corresponding base station and the mobile station (not shown). That is, the first base station tone signal 210 to the N-th base station tone signal 2N0 are, by the propagation delay, Γ ₁ / RTI > Γ _N .

4 is a diagram illustrating a process of calculating the location information of a mobile station using phase difference information transmitted from neighboring base stations and location information of neighboring base stations according to an embodiment of the present invention. Hereinafter, the present invention will be described with reference to FIGS.

The mobile station 200 receives the first base station tone signal 110 to the Nth base station tone signal 1N0 at different points in time. At this time, if the mobile station 200 can know the absolute system time at the time when each tone signal is received, the mobile station 200 can measure the phase difference of each tone signal. The phase difference is proportional to the distance between each base station and the mobile station 200. If the mobile station 200 knows the phase difference information between neighboring base stations and the neighboring base stations, the mobile station 200 can calculate its own location information.

However, as described above, the mobile station 200 according to the embodiment of the present invention must acquire and maintain the absolute system time in order to calculate its location information.

FIG. 5 is a time-axis diagram illustrating a concept that a mobile station acquires an absolute system time of a base station according to an embodiment of the present invention. Hereinafter, description will be made with reference to FIG. 2 to FIG.

The time axis at the top represents the elapsed time of the absolute system time of the base station and the time axis at the bottom represents the elapsed time of the reference time of the mobile station. First, the mobile station acquires the reference time of the mobile station through the initial synchronization acquisition operation. However, as shown in the figure, the reference time t 'of the mobile station due to the acquisition result is slower than the absolute system time t of the base station by the propagation delay time Γ (t). The propagation delay time is caused by the distance between the mobile station and the base station, and is represented as a function of time due to changes in channel conditions such as mobile station movement.

Equation (1) below represents the relationship between the reference time of the mobile station and the absolute system time of the base station.

T _ms (t) = T _bs (t) -? (T)

Equation (1) shows that the reference time Tms (t) of the mobile station is slower than the absolute system time Tbs (t) of the base station by the difference of the propagation delay time Γ (t).

In order to obtain absolute system time, the mobile station transmits a reference time difference request message to the base station. Here, the reference time difference means a difference between the reference time of the mobile station and the absolute system time of the base station.

At this time, the mobile station can transmit the reference time difference request message using an access procedure provided by the IS-95 system. The reference time difference request message is composed of actual data and a preamble. The transmission of the preamble is a process of transmitting a known message between a terminal and a base station before transmitting an actual message when there is a parameter to be matched between the base station and the mobile station or when it is desired to know the status of the other party. At this time, the mutually known messages may be all '0' or all '1', for example. The preamble includes information on the PN sequence of the mobile station.

Upon receiving the reference time difference request message, the base station detects a pseudo-noise (PN) sequence of the mobile station included in the preamble. The base station measures the delay time according to the propagation delay of the received PN sequence and measures the propagation delay time.

As shown in the figure, the mobile station transmits the reference time difference request message to the base station through the access channel while gradually increasing the power of the transmission signal. The reference time difference request message is indicated by a probe and is comprised of a preamble and data. If the reference time difference request message is accessed at time n, the base station measures the propagation delay time Γ (n) of the reference time difference request message at time n. Then, the base station transmits a reference time difference response message according to the propagation delay time Γ (n) of the reference time difference request message to the mobile station. The mobile station receives the reference time difference response message at time T Then, the mobile station calculates the absolute system time of the base station at the T-point.

The difference between the reference time of the mobile station and the absolute system time of the base station at time T can be expressed by Equation (2).

T _ms (T) = T _bs (T) - T (T)

Where T is the time at which the reference time difference response message is received by the mobile station and Γ (T) is the propagation delay time of the reference time difference response message.

However, the above-mentioned Γ (T) can also be expressed by the following Equation (3).

Γ (T) = Γ (n) -ΔΓ (T)

(T) is a mobile station reference time adjustment amount in which the mobile station adjusts its reference time from the time when the mobile station transmits the reference time difference request message to the base station until the time when the mobile station receives the reference time difference response message.

That is, the propagation delay time Γ (T) of the reference time difference response message is calculated by multiplying the propagation delay time Γ (n) of the reference time difference request message by the mobile station reference time adjustment amount ΔΓ (T) As shown in FIG.

Equation (3) can be substituted into Equation (2) and expressed as Equation (4) below.

T _ms (T) -ΔΓ (T) = T _bs (T) -Γ (n)

The left side of Equation (4) shows that the mobile station adjusts its own mobile station reference time to maintain the PN sequence synchronization with the base station. The propagation delay time Γ (n) of the reference time difference request message on the right side of Equation (4) is a value calculated from the base station. The above Equation (4) is rearranged,

T _bs (T) = T _ms (T) -ΔΓ (T) + Γ (n)

That is, it can be seen that the absolute system time Tbs (T) of the base station at time T is calculated by Equation (5).

6 illustrates an internal configuration of a mobile station and a base station for obtaining an absolute system time of a mobile station according to an embodiment of the present invention. Hereinafter, the present invention will be described with reference to FIGS. 2 to 5. FIG.

The message transmission / reception unit 613 of the mobile station 200 performs an operation of transmitting a message to the base station 410 or receiving a message transmitted from the base station 410. In particular, the message transmission / reception unit 613 transmits the reference time difference request message to the base station 410 under the control of the control unit 616. [ At this time, the message transmission / reception unit 613 transmits information about a time point of transmitting the reference time difference request message to the base station 410 (hereinafter referred to as "transmission time information") to the mobile station reference time acquisition and maintenance unit 614 Output. Upon receiving the reference time difference response message from the base station 410, the message transmission / reception unit 613 transmits information on the propagation delay time of the reference time difference request message included in the message to the absolute system time acquisition / (615). Here, the mobile station 200 may transmit the reference time difference request message using an access procedure provided by the IS-95 system.

When the reference time difference request message is received at the nth time point at the base station 410, the propagation delay time measurement unit 611 of the base station 410 detects the PN sequence included in the preamble of the message. The base station 410 checks the delay state according to the propagation delay of the received PN sequence and calculates a propagation delay time Γ (n (n)) of the reference time difference request message transmitted from the mobile station 200 to the base station 410, ). The propagation delay time measurer 611 outputs the propagation delay time Γ (n) of the reference time difference request message to the message transmitter 612. The message transmitter 612 transmits a reference time difference response message corresponding to the propagation delay time Γ (n) of the input reference time difference request message to the mobile station 200.

Meanwhile, the mobile station reference time acquisition and holding unit 614 acquires and maintains the mobile station reference time by the initial synchronization acquisition operation, generates the mobile station reference time adjustment amount, and maintains the PN sequence synchronization with the base station 410. In particular, the mobile station reference time acquiring and holding unit 614 initializes the mobile station reference time adjustment amount every time the transmission time information is input, and updates the mobile station reference time adjustment amount up to the T point when the reference time difference response message is received . When the reference time difference response message is received from the base station, the mobile station reference time acquisition and maintenance unit 614 acquires the reference time difference response message from the base station time difference request message, And outputs the time adjustment amount DELTAΓ (T) and the mobile station reference time Tms (T) to the absolute system time acquisition and holding unit 615. [

The absolute system time acquisition and storage unit 315 stores the propagation delay time Γ (n) of the reference time difference request message output from the message transmission / reception unit 613 and the propagation delay time Γ (n) of the mobile station reference time acquisition and storage unit 614, The absolute system time Tbs (T) of the base station is calculated at the T-point by inputting ?? (T) and Tms (T). At this time, the absolute system time acquisition and maintenance unit 615 acquires and maintains the absolute system time Tbs (T) using Equation (4).

The control unit 616 controls the operation of various components (not shown) included in the mobile station 200. In particular, the control unit 616 includes a message transmission / reception unit 613, a mobile station reference time acquisition and maintenance unit 614, and an absolute system time acquisition and maintenance unit 615 according to the execution of the absolute system acquisition operation of the mobile station 200 . When receiving the reference time difference response message, the control unit 616 informs the mobile station reference time acquisition and maintenance unit 614 of this fact.

7 is a flowchart illustrating a method for acquiring and maintaining an absolute system time of a mobile station according to an embodiment of the present invention. Hereinafter, the present invention will be described with reference to FIGS. 2 to 6. FIG.

In step 710, the mobile station 200 acquires and maintains the mobile station reference time through the initial synchronization acquisition operation. The message transmission / reception unit 613 transmits a reference time difference request message to the base station 410 under the control of the control unit 616 in step 720. At this time, the reference time difference request message includes a preamble including a PN sequence. Then, under control of the control unit 616, the message transmission / reception unit 613 outputs the transmission time point information to the mobile station reference time acquisition and holding unit 614. The mobile station reference time acquisition and holding unit 614 initializes and maintains the mobile station reference time adjustment amount each time the transmission time point information is input under the control of the control unit 616 in step 730. [ In step 740, the control unit 616 checks whether a reference time difference response message is received from the base station 410. [ If the reference time difference response message is not received, the control unit 616 performs the control operation in step 720 again. When the reference time difference response message is received, the control unit 616 controls the mobile station reference time acquisition and maintenance unit 614 to acquire the absolute reference system time and the mobile station reference time adjustment amount, And outputs it to the holding unit 615. Under the control of the control unit 616, the message transmission / reception unit 613 outputs the propagation delay time according to the reference time difference response message to the absolute system time acquisition and storage unit 615. The absolute system time acquisition and holding unit 615 acquires and maintains the absolute system time using the mobile station reference time adjustment amount, the mobile station reference time, and the propagation delay time under the control of the control unit 616 in step 760.

5 to 7, when the mobile station 200 receives the reference time difference request message from the mobile station 200 at the present time, i.e., when the reference time difference response message is received at the mobile station 200, Using the mobile station reference time adjustment amount ?? t and the mobile station reference time Tms (T) at the current time point from the time point of transmission of the reference time difference request message to? (N) T of the base station of the base station Tbs (T).

8 is a diagram illustrating an internal configuration of a mobile station and neighboring base stations for calculating a location information of the mobile station according to an embodiment of the present invention. Hereinafter, the present invention will be described with reference to FIGS. 2 to 7. FIG.

The first base station 410 to the N-th base station 4N0 periodically transmit the first base station tone signal 210 to the N-th base station tone signal 2N0 to the mobile station 200 at different points of time . At this time, the transmission strengths of the first base station tone signal 210 to the Nth base station tone signal 2N0 are adjusted so that only mobile stations corresponding to a jurisdiction of an adjacent base station can detect it.

The internal configuration of the first base station 410 for transmitting its tone signal includes a single tone generator 812 for generating a single tone, a carrier generator 811 for modulating the single tone, And an up-converter 814 (Up-Converter) for converting the output of the mixer 813 into a frequency band suitable for wireless transmission. The internal configuration of the second base station 420 to the Nth base station 4N0 is the same as that of the first base station 410. [

The down-converter 830 included in the mobile station 200 receives the first base station tone signal 210 to the Nth base station tone signal 2N0 and outputs the signals to the baseband ) Signal.

The single tone phase detector and remover 840 receives the control signal and measures a phase difference between the first base station tone signal 210 to the Nth base station tone signal 2N0 converted into the baseband signal. And the single tone phase detector and remover 840 may include a first phase difference Γ ₁ To N-th phase difference Γ _N (Hereinafter referred to as " phase difference information "). The control signal is composed of a single tone period signal and a measurement command signal (hereinafter, the single tone period signal and the measurement command signal are referred to as a " measurement control signal "), and the measurement control signal is transmitted to the controller 616 It can be generated by a request. When the measurement instruction signal is input, the single tone phase detector and remover 840 starts a phase difference measurement operation, and outputs the first base station tone signal 210 to the Nth base station tone signal 2N0 corresponding to the single tone period signal. Is measured. The single tone period signal corresponds to the tone period 211 of FIG. In this case, the phase difference measurement operation for each of the tone signals is an absolute system time measurement reference. That is, the single tone phase detector and eliminator 840 measures each phase difference based on an absolute system time (hereinafter referred to as " position measurement time ") at the time when each tone signal is received. And the absolute system time is provided from the absolute system time acquisition and holding unit 880. Also, the single tone phase detector and remover 840 receives frequency information of each tone signals (hereinafter referred to as " single tone frequency information ") and outputs the first base station tone signal 210 to the Nth base station Removes a single tone of the tone signal 2N0, and outputs a received signal. At this time, the single tone phase detector and remover 840 uses a single tone that is 180 degrees different from the frequency of each single tone.

Demodulator 870 performs an operation to demodulate the received signal. When the demodulated signal is composed of a single tone generation period of each base station, a base station identifier, position information of a base station, and information on a single tone frequency (hereinafter, a demodulated signal is composed of the above information Demodulator 870 outputs the single tone list message to the position tracking control unit 850. [ The single tone list message is transmitted from the service base station to which the mobile station 200 is currently connected. The single tone list message may be transmitted through a common control channel.

The location tracking control unit 850 receives and stores the single tone list message. The position tracking control unit 850 outputs the single tone frequency information and the operation control signal to the single tone phase detection and remover 840. The position tracking controller 850 outputs the phase difference information input from the single tone phase detector and remover 840 and the position information of each base station to the mobile station position calculator 860. Also, the position tracking control unit 850 stores the absolute system time at the time when the phase difference of each tone signal is measured, that is, the absolute system time at the time when each tone signal is received. In addition, the location tracking controller 850 receives mobile station location information and, when receiving a location information request message requesting location information of the mobile station 200 from the base station, transmits the mobile station location information and the location measurement time to a predetermined message, (Hereinafter, a message consisting of the mobile station position information and the position measuring time is referred to as a " mobile station position information message &

The mobile station position calculation unit 860 calculates the position information of the mobile station by inputting the phase difference information and the position information of each base station. The mobile station position calculation unit 860 outputs the mobile station position information to the position tracking control unit 850.

The absolute system time acquisition and maintenance unit 880 performs operations to acquire and maintain absolute system time. The absolute system time acquisition and maintenance unit 880 has the configuration shown in FIG. The absolute system time acquisition and maintenance unit 880 outputs the absolute system time to the position measurement time single tone phase detection and remover 840 and the position tracking control unit 850.

9 is a flowchart illustrating a method of tracking a location of a mobile station according to an embodiment of the present invention. Hereinafter, the present invention will be described with reference to FIGS. 2 to 8. FIG.

In step 910, the absolute system time acquisition and maintenance unit 880 acquires and maintains the absolute system time. In step 920, the location tracking controller 850 receives and stores a single tone list message. In step 930, the location tracking control unit 850 checks whether there is a request for the position tracking of the control unit 616. [ If there is no request for the position tracking, the position tracking control unit 850 does not output the measurement instruction signal in step 940. Thus, the single tone phase detector and remover 840 removes only a single tone of each base station tone signal without measuring the phase difference for the first base station tone signal 210 to the Nth base station tone signal 2N0. However, if there is a request for location tracking in step 930, the single tone phase detector and remover 840, by the control of the position tracking control unit 850 in step 950, And measures the phase difference of the signal 2N0 to output the phase difference information. At this time, the phase difference measurement operation for the tone signals is the absolute system time measurement reference. In step 960, the mobile station position calculation unit 860 calculates the mobile station position information by inputting the phase difference information and the base station position information included in the single tone list message, under the control of the position tracking control unit 850. The mobile station location information is stored in the location tracking control unit 850. In step 970, the location tracking control unit 850 checks whether a location information request message is received from the service base station. If the location information request message is not received, the location tracking controller 850 performs the control operation in step 930 again. When the location information request message is received, the location tracking control unit 850 transmits a mobile station location information message to the service base station.

In the description of FIG. 2 to FIG. 9, the mobile station measures the phase difference of the tone signals transmitted from the nearby base stations at different time points on the basis of the absolute system time, It can be seen that the mobile station calculates its own location information using the location information of the base stations.

As described above, the apparatus and method for tracking a location of a mobile station according to an embodiment of the present invention are advantageous in that a position tracking service can be continuously performed according to a request of the mobile station. Also, the apparatus and method can measure a distance between each base station and a mobile station by using a phase difference of a tone signal transmitted from neighboring base stations, so that there is no problem in power control for a reverse link, thereby reducing power consumption of the mobile station have.

Claims (33)

An apparatus for tracking a position of a mobile station in a mobile communication system using a code division multiple access scheme, An absolute system time acquisition and maintenance unit for acquiring and maintaining an absolute system time, A tone phase detector for measuring a phase difference according to a propagation delay of each of the tone signals transmitted from the plurality of base stations based on the absolute system time; And a mobile station position calculation unit for calculating position information of the mobile station by using the phase difference of each of the measured tone signals and each position information of the plurality of base stations. 2. The mobile station according to claim 1, A location tracking control unit for receiving location information of each of the plurality of base stations, information about each tone signal generation period, each base station identifier and frequency of each tone signal from a service base station, and transmitting location information of the mobile station to the service base station Wherein the mobile station further comprises: 3. The apparatus of claim 2, Wherein the mobile station inputs the tone signals from a down converter provided in the mobile station and performs the measurement operation in response to the tone signal generation period. 4. The mobile station according to claim 3, Further comprising a tone canceling unit for removing a tone of the received signal output from the tone phase sensing unit according to information on the frequency of each tone signal and outputting the tone to a demodulator provided in the mobile station. 5. The apparatus of claim 4, And the measurement operation is performed by a measurement instruction of the control unit of the mobile station. 6. The apparatus according to claim 5, Wherein the absolute system time is input and the information of the time point of the mobile station is transmitted to the service base station. 7. The apparatus of claim 6, wherein the absolute system time acquisition and maintenance unit comprises: A message transmission / reception unit for transmitting a message including a p-en sequence to the service base station and for receiving propagation delay time information from the service base station; A mobile station reference time acquisition and maintenance unit for initializing and maintaining a mobile station reference time adjustment amount when a message including the p-enque sequence is transmitted, And an absolute system time acquiring unit for acquiring the absolute system time using the propagation delay time information, the mobile station reference time adjustment amount, and the mobile station reference time. 8. The method of claim 7, And the time information of the propagation delay occurring when a message including the p-en-sequence transmitted from the mobile station is transmitted to the service base station. 9. The method of claim 8, wherein the message transmission / And a connection procedure of the IS-95 is used. 10. The apparatus of claim 9, (6). &Lt; / RTI > T _ms (T) -ΔΓ (T) = T _bs (T) -Γ (n) Where T is a time point at which the propagation delay time information is received at the mobile station and n is a time at which the service base station receives a message including the P-A sequence of the mobile station. Tms (T) is a mobile station reference time at the T point, DELTAΓ (T) T is the absolute system time at the T point, and Γ (n) is the mobile station reference time adjustment amount from the time point when the message of the mobile station is transmitted to the serving base station to the time point T, And the time information of the propagation delay of the message including the p-ene sequence of the mobile station received at the base station. The method of claim 10, wherein the Equation (6) (7) is substituted into Equation (8) to compute the following equation: < EMI ID = 8.0 > Γ (T) = Γ (n) -ΔΓ (T) Where T is a time point at which the propagation delay time information is received at the mobile station and n is a time at which the service base station receives a message including the P-A sequence of the mobile station. And Γ (T) (N) is time information of a propagation delay of a message of the mobile station received at the n-th time point, and? (N) is time information of a propagation delay of a message of the mobile station, DELTAΓ (T) Is the mobile station reference time adjustment amount from the time point when the message of the mobile station is transmitted to the service base station to the time point T. [ T _ms (T) = T _bs (T) - T (T) Where T is a time point at which the propagation delay time information is received at the mobile station and n is a time at which the service base station receives a message including the P-A sequence of the mobile station. Tms (T) is a mobile station reference time at the T point, Tbs (T) is an absolute system time at the T point, Γ (T) Is a propagation delay time that occurs when the propagation delay information is transmitted to the mobile station. 12. The method of claim 11, wherein the plurality of base stations, A tone generator for generating the tone signal, A carrier frequency generator for modulating the tone; A mixer for frequency-mixing the tone and the carrier frequency, And an up-converter for converting an output of the mixer into a frequency band suitable for wireless transmission. 14. The method of claim 12, wherein the plurality of base stations, And transmits the tone signal periodically to the mobile station at different points in time. 14. The method of claim 13, The same and different frequencies. 15. The method of claim 14, Wherein the transmission strength of the mobile stations is controlled so that only mobile stations corresponding to the jurisdictions of the plurality of base stations can detect. 16. The method of claim 15, wherein the location information of each of the plurality of base stations, the tone signal generation period, each base station identifier, Wherein the mobile station is transmitted through a common control channel. A method for tracking a location of a mobile station in a mobile communication system using a CDMA scheme, A first step of acquiring and maintaining an absolute system time, A second step of measuring a phase difference according to a propagation delay of each of the tone signals transmitted from the plurality of base stations based on the absolute system time; And a third step of calculating position information of the mobile station by using the phase difference of each measured tone signal and each position information of the plurality of base stations. 18. The method of claim 17, A fourth step of receiving location information of each of the plurality of base stations, information on each tone signal generation period, each base station identifier, and frequency of each tone signal from the service base station and transmitting the location information of the mobile station to the service base station, Wherein the mobile station further comprises: 19. The method of claim 18, Wherein the tone signals are input from a down converter provided in the mobile station and the measurement operation is performed corresponding to the tone signal generation period. 20. The method of claim 19, And a fifth step of removing a tone of a received signal output from the tone phase sensing unit according to information on the frequency of each tone signal and outputting the tone to a demodulator provided in the mobile station, . 21. The method of claim 20, Wherein the measurement operation is performed by a measurement instruction of the control unit of the mobile station. 22. The method of claim 21, And inputting the absolute system time to transmit information of a time point at which the mobile station is measured to the serving base station. 23. The method of claim 22, A first step of acquiring and maintaining a mobile station reference time, A second step of transmitting a message including the p-en sequence to the service base station and initializing and maintaining a mobile station reference time adjustment amount at that time, And a third step of obtaining and maintaining the absolute system time using the propagation delay time information transmitted from the service base station, the mobile station reference time, and the mobile station reference time adjustment amount held from the time of message transmission in the second step Mobile station location tracking method 24. The method of claim 23, wherein the propagation delay time information comprises: And the time information of the propagation delay for the message generated when the message transmitted by the mobile station of the second process is transmitted to the service base station. The method of claim 24, wherein if the propagation delay time information is not received from the serving base station in the mobile station within a predetermined time, the operation of the second step is repeatedly performed. 26. The method as claimed in claim 25, Lt; RTI ID = 0.0 &gt; IS-95. &Lt; / RTI &gt; 27. The method of claim 26, (9) < / RTI > is used. T _ms (T) -ΔΓ (T) = T _bs (T) -Γ (n) Where T is a time when the propagation delay time information is received at the mobile station and n is a time at which the message of the mobile station at the second stage is received at the serving base station. Tms (T) is a mobile station reference time at the T point, DELTAΓ (T) T is the absolute system time at the T point, and Γ (n) is the mobile station reference time adjustment amount from the time point when the message of the mobile station is transmitted to the serving base station to the time point T, And time information of a propagation delay of a message of the mobile station received at the base station. 28. The method of claim 27, wherein Equation (9) (10) is substituted into the following equation (11), and is summarized. Γ (T) = Γ (n) -ΔΓ (T) Where T is a time when the propagation delay time information is received at the mobile station and n is a time at which the message of the mobile station at the second stage is received at the serving base station. And Γ (T) (N) is time information of a propagation delay of a message of the mobile station, which is received at the service base station at the n-th time point, and is the propagation delay time when the propagation delay information is transmitted to the mobile station, DELTAΓ (T) Is the mobile station reference time adjustment amount from the time point when the message of the mobile station is transmitted to the service base station to the time point T. [ T _ms (T) = T _bs (T) - T (T) Where T is a time when the propagation delay time information is received at the mobile station and n is a time at which the message of the mobile station at the second stage is received at the serving base station. Tms (T) is a mobile station reference time at the T point, Tbs (T) is an absolute system time at the T point, Γ (T) Is a propagation delay time that occurs when the propagation delay information is transmitted to the mobile station. 29. The base station of claim 28, wherein a plurality of base stations, A tone generator for generating the tone signal, A carrier frequency generator for modulating the tone; A mixer for frequency-mixing the tone and the carrier frequency, And an up-converter for converting the output of the mixer into a frequency band suitable for wireless transmission. 30. The method of claim 29, wherein the plurality of base stations, And transmitting the tone signal periodically to the mobile station at different points in time. 31. The method of claim 30, Wherein the first and second frequencies are the same and different frequencies. 32. The method of claim 31, Wherein the transmission strength is controlled so that only mobile stations corresponding to the jurisdictions of the plurality of base stations can detect. 33. The base station of claim 32, wherein information about each location information of each of the plurality of base stations, each tone signal generation period, each base station identifier, and frequency of each tone signal received from the service base station, And transmitting the same through a common control channel.