JP2000050343A - Method for detecting position of mobile station and position detection system for base station and mobile station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to highly accurately measure the position of a mobile station by executing 2nd processing by using plural 1st processing results found out by respective base stations and detecting the position of the mobile station. SOLUTION: A common receiving signal is supplied from a synchronism acquisition part 18 to three synchronous follow-up parts 20 to 22 to supply propagation time data p1 to p3 indicating the generation timing of a spread code part sequence to respective synchronous follow-up parts 20 to 22. The follow-up part 20 finds out a correlation value between the receiving signal and the spread code part sequence of the generation timing while over-sampling data and obtains highly accurate propagation time data H1. the follow-up parts 21, 22 also similarly found out highly accurate propagation time data H2, H3. Respective up-down counters 23 to 25 obtain respective counter values CV1 to CV3 in accordance with these data H1 to H3. A shortest time detection circuit 26 simply compares these three counter values CV1 to CV3 and selects the shortest counter value. The selection means the selection of data providing the shortest propagation time out of the three data H1 to H3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for detecting the position of a mobile station, and is suitable for use in detecting the position of a mobile station with high accuracy, for example, in a CDMA (Code Division Multiple Access) system. .

The present invention also relates to a base station as a component of such a mobile station position detecting system.

Further, the present invention relates to a mobile station position detecting method used in such a mobile station position detecting system.

[0004]

2. Description of the Related Art In recent years, with the development of mobile communication technology, portable telephones and personal handyphone system (PHS) have been developed.
m), services using mobile stations such as pagers are also diversifying.

[0005] As one of such services, there is a location service that measures the position of a mobile station and teaches the user.

[0006] For example, in the PHS location locating service that is currently being carried out, the PHS terminal is located in a cell of which base station, that is, which base station is connected to the PHS terminal. The position can be estimated.

[0007]

However, in such a position locating method, even in the case of a PHS having a small cell radius, a positioning error can be up to several hundred meters, and in a system such as a cellular phone having a large cell radius, the error is small. Is too large to be practical.

[0008]

According to a first aspect of the present invention, there is provided a method for receiving a reference signal transmitted from a mobile station at a plurality of base stations and detecting a position of the mobile station. It is characterized by comprising the following processes.

That is, the first invention provides: (1) a reference transmitted by the mobile station in a state where the system including the plurality of base stations grasps the relationship between the operation timings of the respective base stations in the system. (2) Each base station that has received the reference signal performs the first process based on timing data including at least the earliest timing information at which the reference signal is received by each base station. By the first
And (3) performing the second processing using the plurality of first processing results obtained by each of the base stations to detect the position of the mobile station. .

Further, in the second invention, in order to detect the position of the mobile station, the base station receiving the reference signal transmitted by the mobile station is connected to another base station for detecting the position of the mobile station. And a first means for performing a first process based on timing data including at least the earliest timing information at which the reference signal is received by the base station. It is characterized by comprising processing means.

Further, in a mobile station position detecting system according to a third aspect of the present invention, a plurality of base stations according to any one of claims 4 to 6 are provided, and the plurality of base stations are connected to the plurality of base stations. The method further comprises a position detecting means for detecting the position of the mobile station by performing the second processing using the results of the plurality of first processings determined in step (1).

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (A) Embodiment A mobile station position detecting method, a base station and a mobile station position detecting system according to the present invention are applied to a CDMA mobile communication system as an example. An embodiment will be described.

In position measurement of a mobile station, it is ideal to measure the position using a direct wave in order to realize accurate positioning. However, in mobile communication, multipath fading generally exists, so that a direct wave is used. It is difficult to take out only. In other words, FDMA (Frequency Division Multiple Access) or TDM
In A (Time Division Multiple Access), it is difficult to separate multipath fading.

However, a CD using a spread spectrum signal
In the MA system, by using a rake receiver,
Multipath separation becomes possible. In particular, by using a digital rake receiver, multipath separation can be performed with an accuracy of a chip unit or N times as large as a chip, so that a more accurate radio wave propagation time and arrival time can be obtained.

[0015] The mobile communication system according to the present embodiment comprises:
It is configured paying attention to such a point.

(A-1) Configuration of the Embodiment FIG. 2 shows a CDMA mobile communication system 10 of the present embodiment. A plurality of base stations such as the base stations 11 to 13 receive radio signals such as the radio signals S1 to S3 transmitted simultaneously from one common mobile station 14 and propagated on different propagation paths. S1 to S3 are direct waves, and MP is a multipath component.

The multipath component MP propagates along a long propagation path different from the direct waves S1 to S3 due to reflection by an obstacle 16 such as a building, and is received by the base station 11, for example. Therefore, the multipath component MP has a longer propagation time (delay time) than the direct wave S1, and is received by the base station 11 with a phase delayed from the direct wave S1. A base station in an environment with many obstacles, such as an urban area, may receive only a plurality of multipath components and may not receive a direct wave. In this case, the path (propagation path) closer to the direct wave has a shorter propagation time.

In FIG. 2, each of the base stations 11 to 13 synchronized with each other has a shortest time detecting device for detecting a reception timing of a component closest to a direct wave from among a plurality of multipath components. It is installed. The shortest time detecting device in the base station 11 is denoted by reference numeral 15A, the shortest time detecting device in the base station 12 is denoted by reference numeral 15B, and the shortest time detecting device in the base station 13 is denoted by reference numeral 15C to distinguish them. .

It is assumed that all of the shortest time detection devices 15A to 15C have the same configuration.

In FIG. 1 showing the structure of the shortest time detection device 15A mounted on the base station 11, the synchronization acquisition unit 1
Numeral 8 has a built-in spreading code generator for generating the same spreading code subsequence as used by the mobile station 14 on the transmitting side for spreading in order to perform despreading.

Upon receiving the received signal, the synchronization acquiring section 18 obtains a correlation value between the spread code and the received signal, thereby separating a plurality of multipath components included in the received signal. This is a section having a function of preferentially selecting a multipath component showing a large correlation value and supplying data of each multipath component to the next three synchronization followers 20 to 22.

In general, it can be said that a multipath component having a larger correlation value has a shorter propagation time and is closer to a direct wave.

The multipath component data includes at least propagation time data (P1 to P3 described later) at which the correlation value shows a peak.

Each of the synchronization followers 20 to 22 is composed of a kind of DLL (Delay Locked Loop).
The loop structure includes an envelope detection circuit which is a part of the demodulation unit.

Each of the three synchronization followers 20 to 22 has a built-in spread code generator similarly to the synchronization acquisition unit 18, but this spread code generator determines the generation timing of a spread code partial sequence for performing despreading. It can be controlled and arbitrarily changed.

Each of the synchronization followers 20 to 22, which receive data of a different multipath component, generates the subsequence at the generation timing changed by the change amount corresponding to the data of the corresponding propagation time. A different multipath component is extracted from the same received signal supplied via the acquisition unit 18, and N (N
Is a positive integer) and has a function of tracking synchronization with much higher accuracy than the synchronization acquisition unit 18 and outputting high-precision propagation time data H1 to H3.

The up / down counter 23 connected to the output terminal of the synchronization follow-up unit 20 responds to the propagation time of the corresponding multipath component which has been detected by the synchronization acquisition unit 18 and further improved in accuracy by the synchronization follow-up unit 20. , A counter that counts up or counts down. The up / down counter 23 may be, for example, a 16-bit 65536 base up / down counter.

The up / down counters 24 and 25 connected to the output terminals of the synchronization followers 21 and 22 are the same counters as the up / down counter 23, and have the same relationship with the connected synchronization followers. .

The shortest time detection circuit 26 connected to the output terminals of these three counters 23 to 25 monitors the counter values CV1 to CV3 of the counters 23 to 25, and outputs the smallest counter value to the base station 11 concerned. Counter value LC corresponding to the shortest propagation time data T1
Select as 1 and output.

As shown in FIG. 2, the optical fiber cable 11A connected to the base station 11 transmits the minimum counter value LC1 to the arithmetic unit 17.

Similarly, the minimum counter values LC2 and LC3 corresponding to the shortest propagation time data T2 and T3 obtained by the shortest time detection devices 15B and 15C mounted on the other base stations 12 and 13 are also optical signals. Fiber cable 12A,
It is supplied to the arithmetic unit 17 via 13A.

The arithmetic unit 17 calculates the propagation time data T
TOA (Time of Arrival), TDO based on 1 to T3
This is a part for performing a geometric calculation by a method such as A (Time difference of Arrival).

Generally, in TOA positioning,
First, incoming waves from one measurement target are received at a plurality of observation points. Next, based on the propagation time of the arriving wave (reception time-transmission time), a circle having a radius equal to the distance from the observation point to the measurement target is drawn, and the position is obtained from the intersection. In this method, a time at which the observation target starts transmitting radio waves is required.

In the positioning by the general TDOA method, first, a difference between arrival times of two observation points is obtained, and a hyperbola is drawn. Then, another hyperbola is drawn by changing the combination of the two observation points, and the position is estimated from the intersection of these hyperbolas.

In TDOA, since the difference between the observation points is used, the time at which the observation target starts transmitting radio waves is not required.

Both the TOA and TDOA methods require that the time of each observation point be synchronized.

These TOA and TDOA systems are used in the mobile station 14.
In introducing the positioning, the observation target here corresponds to the mobile station 14 to be positioned, and the observation points correspond to the base stations 11 to 13.

Therefore, in a system in which all the base stations 11 to 13 are completely synchronized, TOA and TDOA can be applied by measuring the deviation from the reference time.

The system clock detection circuit 19 shown in FIG.
By resetting the counters 23 to 25 in synchronization with the system clock when the shortest time detection device 15A is powered on, each of the counters 23 to 25 corresponding to the high-accuracy propagation time data H1 to H3 supplied from the synchronization follow-up units 20 to 22 thereafter. The counter values CV1 to CV3 are obtained.

When the power is turned on, the system clock detecting circuit 19 resets the spread code generators built in the synchronization acquisition section 18 and the synchronization follow-up sections 20 to 22 to reset the generation timing of the partial sequence. It has a function to return to the initial state.

The system clock detection circuit 19 receives a radio signal from a satellite, thereby enabling the base station 11 to synchronize with the other base stations 12, 13, and the like. Note that the synchronization operation of each base station may be performed by a wired signal as needed.

The operation of this embodiment having the above configuration will be described below.

(A-2) Operation of the Embodiment When the shortest time detection device 15A is powered on and a received signal is supplied, the synchronization acquisition unit 18 converts the multipath component contained in the received signal into a signal shown in FIG. ) And (B) are separated in the propagation time direction. Note that FIG.
IS in (A) indicates a signal in which an interference wave and noise are mixed.

In the illustrated example, a path 1 for providing a propagation time value P1, a path 2 for providing a propagation time P2, and a path
Each multipath component of path 3 giving (P1 <P2 <P3) is detected. If the number of multipath components is four or more, three paths are preferentially selected as the correlation value increases, and the subsequent processing is performed only on the three paths.

For example, when the Serial Search Acquisition method is used, the multipath component is separated while the generation timing of the spread code sequence (subsequence) of the spread code generator built in the synchronization acquisition unit 18 is slightly shifted. This is performed by determining a correlation value, and the propagation time P1,
P2 and P3 each correspond to a certain generation timing of the spreading code subsequence.

The common reception signal is supplied from the synchronization acquisition unit 18 to the three synchronization follow-up units 20 to 22, and propagation time data P1, P2, and P3 indicating the generation timing of the spread code partial sequence are supplied. Is done.

For example, assuming that the propagation time data P1 is supplied to the synchronization follow-up unit 20, the synchronization follow-up unit 20
As shown in FIG. 3 (C), the correlation value between the received signal and the spread code subsequence of the generation timing is obtained while performing oversampling, so that the propagation time data P1 is fine-tuned to increase the accuracy, and Propagation time data H1 can be obtained.

This oversampling may be, for example, eight times oversampling. The higher the sampling frequency, the more accurately the peak position, that is, the propagation time of each path can be detected. For example, if the chip rate of the spreading code is 1 / 1.288 Mbps and the peak corresponding to pass 1 is oversampled by 8 times as shown in FIG.
5 = 1 / (1.2288 Mbps × 8)).

That is, the peak of the path can be detected with a resolution of 100 ns.

The synchronization follow-up units 21 and 22 that have received the propagation time data P2 and P3 and the received signal also
0 is performed, and high-precision propagation time data H2,
H3 is required.

Next, the up / down counter 23 obtains the counter value CV1 in accordance with the high-accuracy propagation time data H1.

Similarly, the up / down counter 24,
Also at 25, counter values CV2 and CV3 corresponding to the high-accuracy propagation time data H2 and H3, respectively, are obtained.

In this embodiment, 16 bits, that is, 65 bits
These three counters 23-2, which are 536-base counters
5, the change range of the counter values CV1 to CV3 is shown in FIG.
(A) is a common range CS above. The change range CS is, for example, a partial sequence 8192 (= 65536 /
8) Corresponds to chip.

Since the transmitting mobile station 14 actually spreads using this partial sequence, the peaks of the paths 1 to 3 and the like must always appear within this range CS. In addition,
Since the chip rate of the spreading code is constant, specifying the number of chips is synonymous with specifying the time width.

To widen the change range CS, it is sufficient to increase the 16 bits. To narrow it, the 16 bits may be reduced. However, the width of the range CS depends on the number of chips of the partial sequence. Is to be determined.

On the other hand, the counter value C of the counters 23 to 25
The shortest time detection circuit 26 monitoring V1 to CV3 is:
The three counter values are simply compared to select the smallest counter value. Choosing the smallest counter value is
This means that data that gives the shortest propagation time among the high-accuracy propagation time data H1 to H3 is selected with high accuracy.

In the example of FIG. 3, since it is clear that the propagation time of the path 1 is the shortest, the counter value CV of the counter 23 is obtained.
1 is selected as the minimum counter value LC1 in the base station 11, and this minimum counter value LC1 is supplied to the arithmetic unit 17 as the shortest propagation time data T1.

From the base stations 12, 13 and the like, the shortest propagation time data T2, T3 are used as the minimum counter values LC2, LC3.
The arithmetic unit 17 receiving the “3” receives the TOA or TD described above.
The position of the mobile station 14 is calculated by OA or the like.

On the other hand, when the propagation path of the multipath component changes due to the movement of the mobile station 14, etc., each of the paths 1 to 3 slides independently in the direction of the propagation time axis on FIG. The peak height of each pass also changes according to the slide.

Therefore, in order for the base station to reliably keep the path giving the shortest propagation time, a configuration having a plurality of synchronous followers is advantageous. If there is only one synchronous follower, the accuracy and reliability of the shortest propagation time data T1 to T3 may be reduced at the moment when the path giving the shortest propagation time is switched.

(A-3) Effects of the Embodiment As described above, according to the present embodiment, the positioning of the mobile station requires T
By using the OA method or the TDOA method, it is possible to measure the position of a mobile station with much higher accuracy than in the related art in which only the cell in which the mobile station is present is examined.

Further, the accuracy of the positioning is increased by separating the multipath components using the synchronization acquisition unit, and is further improved by fine adjustment in the synchronization tracking unit.

Further, in the present embodiment, the system clock detection circuit 19 and the synchronization acquisition
8. By skillfully utilizing the functions of the plurality of synchronization followers 20 and the like, an increase in the amount of hardware is suppressed to a small scale such as the up / down counters 23 to 25 and the shortest time detection circuit 26.

(B) Other Embodiments In the above description, the CDMA method has been described. However, the present invention is not limited to the CDMA method, but can be applied to the TDMA method and the FDMA method. T
In the DMA system and the FDMA system, since it is difficult to separate the multipath components, the positioning is performed based on the peaks shown by the broken lines in FIG.
A can be applied in exactly the same way as in CDMA, and much higher accuracy can be expected than in the past.

The number of multipath components sent from the synchronization acquisition unit to the synchronization follow-up unit may be more or less than the above three. For example, the number may be one.

The provision of the three synchronization follow-up units in one base station as described above is a configuration conventionally used to increase the S / N ratio in the demodulation unit and reliably follow the synchronization. Therefore, it is not an essential requirement for the present invention. Therefore, one base station may have only one synchronization follower.

Further, in the above embodiment, the Serial Search
Although the Acquisition method was used, the Matched Filtering method may be used.

As a geometric calculation method for positioning, a method other than the above-described TOA or TDOA may be used.

The base stations 11 to 13 of the above embodiment
The present invention can be applied to at least two stations,
It is possible to obtain higher accuracy than before.

Further, the mobile station to be located is not limited to a mobile telephone but may be a mobile station such as a pager.

In the above embodiment, the base stations are synchronized with each other. However, even if the operations of the base stations are not synchronized and the operation timings of the base stations are shifted from each other, each base station is not synchronized. If the deviation of the operation timing of the operation is completely grasped by the system, it is included in the scope of the present invention.

A part of the processing performed by the shortest time detecting device in each base station may be performed by the arithmetic unit 17. Alternatively, it may be performed inside a plurality of base stations.

That is, the present invention can be widely applied to a case where a reference signal transmitted from a mobile station is received by a plurality of base stations and the position of the mobile station is detected.

[0074]

As described above in detail, according to the present invention, it is possible to estimate the position of a mobile station with higher accuracy than before.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a minimum time detection device according to an embodiment.

FIG. 2 is a schematic diagram illustrating a configuration of a mobile communication system according to an embodiment.

FIG. 3 is a schematic diagram for explaining the operation of the minimum time detection device according to the embodiment.

[Explanation of symbols]

10 mobile communication system, 11-13 base station, 14
Mobile station, 15A to 15C: shortest time detection device, 18: synchronization acquisition unit, 19: system clock detection circuit, 20 to 2
2: Synchronous tracking unit, 23 to 25: Up / down counter,
26: shortest time detection circuit, T1 to T3: shortest delay time data, MP: multipath component.

Claims (8)

[Claims] 1. A method of receiving a reference signal transmitted by a mobile station at a plurality of base stations and detecting a position of the mobile station, wherein a system including the plurality of base stations is connected to each base station in the system. Receiving the reference signal transmitted by the mobile station in a state where the relationship of the operation timings is grasped, each base station receiving this reference signal is at least the earliest that the reference signal is received by each base station. A first processing result is obtained by performing a first processing based on timing data including timing information of the second processing, and a second processing is performed using a plurality of first processing results obtained by each of the base stations. A mobile station position detecting method for detecting the position of the mobile station. 2. The mobile station position detecting method according to claim 1, wherein communication between the mobile station and each base station is performed by a code division multiple access method, and at least the base station is used in the first processing. And a multipath component separation process for separating a multipath component based on a correlation value between a received signal and a predetermined spreading code by using a synchronization acquisition unit for code division multiple access mounted on the mobile terminal. Mobile station location detection method. 3. The position detection method for a mobile station according to claim 2, wherein the first processing includes, in addition to the multipath component separation processing, the multipath component separation processing with each of the separated multipath components and a predetermined spreading code. A multipath component selection process of comparing the magnitudes of the correlation values and preferentially selecting a predetermined number of multipath components as the correlation value is larger, and the same number as the predetermined number is mounted for each of the base stations. Distribution processing for supplying the data of the respective multipath components selected in the multipath component selection processing to the synchronization following means, and the predetermined processing for each of the synchronization tracking means receiving the supply of the data of the multipath component. A fine separation process for further finely separating the multipath component by obtaining a correlation value with the spread code of A reception timing setting process for changing the state of the storage element, and by examining the state of each storage element connected to the synchronization tracking means, corresponds to the earliest reception timing given by the multipath component received by each base station. And the earliest timing detection processing for detecting the corresponding timing data. The second processing performed after the first processing includes:
A position detection method for a mobile station, which is a geometric calculation performed based on the corresponding timing data obtained for each base station in the earliest timing detection processing. 4. A base station for receiving a reference signal transmitted by a mobile station in order to detect a position of the mobile station, and maintaining a predetermined operation timing relationship with another base station for detecting the position of the mobile station. And a first processing unit that performs a first process based on timing data including at least the earliest timing information at which the reference signal is received by the base station. Base station that features. 5. The base station according to claim 4, wherein communication between the mobile station and the base station is performed by a code division multiple access system, and at least the first processing is installed in the base station. A base station comprising a multipath component separation process for separating a multipath component based on a correlation value between a received signal and a predetermined spreading code by using a synchronization acquisition unit for code division multiple access. 6. The base station according to claim 5, wherein, in the first processing, in addition to the multipath component separation processing, a magnitude of a correlation value between each of the separated multipath components and a predetermined spreading code. And a multipath component selection process for selecting a predetermined number of multipath components in preference to a larger correlation value, and a synchronization tracking means mounted on each base station by the same number as the predetermined number. A distribution process of supplying data of each multipath component selected in the multipath component selection process; and the predetermined spreading code for each synchronization follower receiving the supply of the data of the multipath component. A fine separation process for further finely separating the multipath component by calculating the correlation value of the following. The state of the storage element connected to each of the synchronization follow-up means according to the result of the fine separation process A reception timing setting process for changing the synchronization timing, and checking the state of each storage element connected to the synchronization follow-up means to obtain the corresponding timing data corresponding to the earliest reception timing given by the multipath component received by each base station. And an earliest timing detection process for detecting the base station. 7. A plurality of base stations according to any one of claims 4 to 6, further comprising a plurality of base stations connected to the plurality of base stations, wherein a plurality of first processing results obtained by the respective base stations are used. A position detecting means for detecting the position of the mobile station by performing the second processing in step (b). 8. The mobile station position detection system according to claim 7, wherein the second processing is executed based on the timing data obtained for each base station in the earliest timing detection processing. A mobile station position detection system, which is a simple calculation.