JP2004297817A - Distance detection method and location detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a distance to and a location of a mobile station in a base station arrangement for the purpose of efficiently utilizing radio resources for information communications in spread spectrum cellular mobile communications. <P>SOLUTION: While paying attention to an information quantity that is generally required for a range finding signal but is sufficiently reduced in comparison with an information quantity required for information communications, a sufficiently long symbol cycle, namely, spreading code cycle is taken for the range finding signal to obtain a sufficiently great spreading code bit length, namely, spreading code gain, thereby extending a communicable distance of the range finding signal compatibly with reducing an interference quantity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a distance detection method and a position detection method suitable for detecting a relative distance between a mobile station and a base station and a position of the mobile station, and is particularly applicable to a mobile communication system of a spread spectrum communication system. The present invention relates to a distance detection method and a position detection method.

  2. Description of the Related Art Conventionally, as a method for detecting the position of a mobile station in a cellular mobile communication system, for example, there is a method described in Patent Document 1 below.

The relative distance between the mobile station and the plurality of base stations in the cellular mobile communication system is obtained from the one-way propagation time of the communication between the mobile station and the base station. The position of the mobile station can be obtained based on the triangulation principle based on the position information of the base station.
Japanese Patent Publication No. 10-505723

  However, the conventional cellular mobile communication system has the following problems.

  That is, in a cellular mobile communication system in which an information communication service has been implemented, when a service for newly detecting the position of a mobile station is started, in order to obtain a relative distance between the mobile station and each of the plurality of base stations. It is assumed that communication is possible between the mobile station and each of the plurality of base stations. For that purpose, the coverage area of the base station, that is, the cell, needs to cover another adjacent base station. However, the fact that the cell covers another adjacent base station means that the interference between the base stations increases and the base station arrangement of the cellular mobile communication system is inappropriate. . That is, a request for base station arrangement for detecting the position of a mobile station is opposite to a request for base station arrangement for efficient use of radio resources in information communication. It is difficult to efficiently perform both the communication service and the mobile station location service.

  The present invention has been made in view of such a point, and in a base station arrangement for efficient use of radio resources for information communication in spread spectrum cellular mobile communication, position detection of a mobile station is performed. It is an object to provide a distance detection method and a position detection method that can be performed.

  The distance detection method of the present invention provides a base station with a broadcast channel, transmits a signal having periodicity based on a reference timing generated by a reference timer of the base station from the broadcast channel, The mobile station receives a signal having the characteristic and detects the reception timing by a reference timer of the mobile station to obtain a phase difference, and detects the relative distance between the mobile station and the base station based on the obtained phase difference.

  With this method, if the base timers of the base station and the mobile station have been adjusted, the relative distance between the base station and the mobile station can be obtained by multiplying the obtained phase difference by the speed of light.

  In the distance detection method of the present invention, a signal is transmitted between a mobile station and a base station, and the mobile station receives a signal from the base station and detects a reception timing with a reference timer of the mobile station. The base station receives the signal from the mobile station, detects the reception timing with the reference timer of the base station, calculates the phase difference, and further calculates the phase difference and the phase difference calculated by the mobile station. , A deviation of the reference timing between the mobile station and the base station is detected, and the reference timer of the mobile station is adjusted to the reference timer of the base station based on the detected deviation of the reference timing.

With this method, the reference timer of the mobile station can be adjusted to the reference timer of the base station. In this case, the deviation of the reference timer of the mobile station with respect to the reference timer of the base station is expressed by the following equation:
Deviation of reference timer of mobile station = (base station detected phase difference−mobile station detected phase difference) / 2
Can be determined based on

  Further, the position detection method of the present invention detects a distance between the mobile station and each of at least three base stations using the distance detection method, and detects a position of the mobile station based on the detected distance. I made it.

  With this method, the distance between the mobile station and each of the at least three base stations can be detected, so that the position of the mobile station can be detected using the principle of triangulation.

  In addition, the position detection method of the present invention includes a plurality of base stations for communicating a ranging signal with a mobile station, a main base station whose position is registered by the mobile station, and at least two base stations adjacent to the main base station. As a station, a relative distance between the mobile station and the main base station is detected, and the detected relative distance is determined between the main base station and each of the at least two base stations adjacent to the main base station. And the initial value of the communication parameter of the ranging signal between the mobile station and each of the at least two base stations, based on the value of the communication parameter of the ranging signal between the mobile station and the main base station. I decided to decide.

  By this method, the relative distance between the mobile station and the main base station with which the mobile station has registered its position, and the distance between the main base station and at least two base stations adjacent to the main base station are determined by the radiated power. By substituting into a function of attenuation according to distance, a condition of a communication parameter for mutually receiving a ranging signal between each of at least two base stations adjacent to the main base station and the mobile station is obtained. Can be.

  By reflecting the condition of this communication parameter on the initial value of the communication parameter of at least two base stations adjacent to the mobile station and the main base station, each of the mobile station and at least two base stations adjacent to the main base station The communication of the ranging signal can be reliably started between the two. Then, since the distance between the mobile station and each of the main base station and at least two base stations adjacent to the main base station can be detected, the position of the mobile station can be detected using the principle of triangulation. Can be.

  Further, the position detection method of the present invention, the transmission power of the ranging signal transmitted by each of at least two base stations adjacent to the main base station and the initial value of the spreading code gain, the mobile station and the main base station between The relative distance between the main base station and the distance between each of the at least two base stations adjacent to the main base station, the transmission power of the ranging signal transmitted by the main base station, and the spreading code gain. It was decided based on.

  By this method, the relative distance between the mobile station and the main base station, and the distance between the main base station and at least two adjacent base stations are substituted into a function of attenuation according to the distance of the radiated power. By making the effective transmission power of the ranging signal from each of the at least two base stations adjacent to the main base station to the mobile station multiple times the effective transmission power of the ranging signal of the main base station, Can be calculated. If the above conditions are reflected in the initial values of the transmission power and the spreading code gain, the mobile station can reliably receive the ranging signal from at least two base stations adjacent to the main base station.

  Further, in the position detection method according to the present invention, in the position detection method, the transmission power and spread of the ranging signal transmitted to at least two base stations adjacent to the main base station registered by the mobile station are registered. The initial value of the code gain is determined by the distance between the mobile station and the main base station, the maximum value of the distance between the main base station and the base station adjacent to the main base station, The determination is made based on the transmission power of the ranging signal transmitted to the station and the spreading code gain.

  By this method, the relative distance between the mobile station and the main base station and the maximum value of the distance between the main base station and the adjacent base station are substituted into the attenuation function according to the distance of the radiated power. By setting the effective transmission power of the ranging signal from the mobile station to at least two base stations adjacent to the main base station to be multiple of the effective transmission power of the ranging signal to the main base station, It is possible to calculate whether or not at least two base stations that can perform reception can receive. If the above conditions are reflected in the initial values of the transmission power and the spreading code gain of the ranging signal transmitted to at least two base stations adjacent to the main base station, at least two base stations adjacent to the main base station Can reliably receive the ranging signal from the mobile station.

  Further, the position detecting device of the present invention employs a configuration including storage means for storing a program for realizing the above-described position detecting method, and communication means for transmitting and receiving a signal subjected to spread spectrum modulation.

  With this configuration, the position detection method can be realized in a communication device using a spread spectrum modulation method.

  Further, the distance detection method of the present invention, when the communication stations communicate a distance measurement signal to detect a distance based on the propagation time of the distance measurement signal, the tolerance of the distance measurement, the distance resolution of the distance measurement, The communication cycle of the ranging signal is determined based on the relative speed information between the communication stations.

  According to this method, the minimum necessary frequency of the distance detection (1 / communication cycle) can be obtained according to the relative speed between the communication stations, and unnecessary distance detection is not required.

  Further, in the distance detection method of the present invention, in the distance detection method, the mobile station determines a communication cycle and notifies the base station of the communication cycle.

  By this method, the network including the base station can know the communication cycle of the ranging signal that can be received by the mobile station.

  Further, in the distance detection method of the present invention, in the above distance detection method, a symbol rate of the distance measurement signal is determined based on a communication cycle of the distance measurement signal and an amount of information necessary for the distance measurement. The intermittent time of the ranging signal is obtained based on the communication cycle and the information amount, and the transmission power is turned off during the intermittent time for each communication of the ranging signal.

  According to this method, the minimum frequency (1 / communication cycle) and the symbol rate required for the distance detection can be obtained in accordance with the relative speed between the communication stations. No need to radiate.

  When the symbol rate becomes equal to a value obtained by dividing the amount of information necessary for distance measurement by the communication cycle of the distance measurement signal, the intermittent time of the distance measurement signal becomes zero.

  Determining the symbol rate when the spreading chip rate is a fixed value is equivalent to determining the spreading code gain.

  Adopting a smaller amount of information is equivalent to adopting a longer symbol period, a larger spreading code gain is obtained, and transmission power required for a ranging signal can be reduced.

  In the distance detection method according to the present invention, in the distance detection method, the mobile station determines a communication cycle and a symbol rate and notifies the base station of the determined communication cycle and symbol rate.

  By this method, the network including the base station can know the communication cycle and symbol rate of the ranging signal that can be received by the mobile station.

  A position detecting device according to the present invention includes a storage unit storing a program including a procedure for realizing the distance detecting method and a procedure for realizing the position detecting method, and a communication unit for transmitting and receiving a signal subjected to spread spectrum modulation. Are adopted.

  With this configuration, the position detection method and the distance detection method can be realized in a spread spectrum modulation communication device.

  Further, the speed detection method of the present invention uses the above-described position detection method to detect the position of the mobile station whose position is to be detected by shifting the time, and moves the mobile station based on the amount of change in distance converted from the change in position per unit time. The speed of the station was detected.

  With this method, the speed of the mobile station whose position is to be detected can be detected.

  Further, the spread spectrum communication apparatus of the present invention employs a configuration including storage means for storing a program for realizing the above spread spectrum communication method.

  With this configuration, it is possible to realize a spread spectrum communication apparatus that realizes the above spread spectrum communication method.

  The position detection device of the present invention employs a configuration including the above-described spread spectrum device. Thus, position detection can be performed in the above spread spectrum communication method.

  Further, the distance detecting apparatus of the present invention employs a configuration including a storage unit storing a program for realizing the above distance detecting method, and a spread spectrum communication unit.

  With this configuration, it is possible to realize a distance detection device that realizes the above-described distance detection method.

  Further, an in-vehicle device of the present invention employs a configuration including the above-described distance detecting device.

  With this configuration, it is possible to realize a vehicle-mounted distance detection device that realizes the above-described distance detection method.

  An in-vehicle device according to the present invention employs a configuration including the position detecting device. Thus, the above-described position detection method can be realized in the vehicle-mounted device.

  In the apparatus of the present invention, the storage means is selected from the group consisting of a semiconductor memory, a magnetic storage medium, an optical storage medium, and a magneto-optical recording medium. Thus, a program for the position detection method and the distance detection method can be stored.

  Further, a mobile communication system of the present invention employs a configuration including a mobile station having the above device and a base station having the above device.

  With this configuration, when the spread code length of the ranging signal is determined and updated, the effect of the above-described spread spectrum communication method and the effect of each of the above-described distance detection methods can be obtained.

  As described above, according to the present invention, paying attention to the fact that the amount of information required for a ranging signal is generally sufficiently smaller than the amount of information required for information communication, the necessary minimum symbol Since the rate is obtained and a sufficiently long symbol period (spreading code period) is taken for the ranging signal to obtain a sufficiently large spreading code bit length (spreading code gain), the communicable distance of the ranging signal is extended. In addition, it is possible to reduce the amount of interference. This makes it possible to detect the position of the mobile unit on the base station arrangement for efficient use of radio resources for information communication in cellular mobile communication.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a functional block diagram of a base station and a mobile station capable of performing CDMA wireless communication as one of the spread spectrum communication systems according to Embodiment 1 of the present invention.

  In the figure, a base station 10 generates a base station-side control unit 11 having an arithmetic function for communication control and distance measurement, and a clock having a sample rate fs (sample cycle Ts) and a chip rate fc (cycle Tc). It includes a timer 12, a spreading circuit 13 for spreading transmission data, an antenna 14 for transmitting a spread signal and receiving a radio wave, and a sliding correlator 15 for demodulating a received signal. The base station-side control unit 11 includes a CPU, a DSP, a memory, and the like, and has a phase difference detection function described later in addition to the original base station function. The sliding correlator 15 outputs a despread code generator 16 that shifts the spread code to generate a despread code in order to obtain a correlation with the received signal, and outputs a correlation value obtained by multiplying the received signal by the despread code. And a despreading circuit 17.

  On the other hand, the mobile station 20 has the same functional block diagram as the base station 10 for spread spectrum communication. That is, it includes a mobile station-side control unit 21, a timer 22, a spreading circuit 23, an antenna 24, and a sliding correlator 25. The mobile station control unit 21 includes a CPU, a DSP, a memory, and the like, and has a phase difference detection function and a calculation function of detecting a relative distance from the base station 10 in addition to the original mobile station function. Sliding correlator 25 outputs a despreading code generator 26 that shifts a spreading code to generate a despreading code in order to obtain a correlation with a received signal, and a correlation value obtained by multiplying the received signal by the despreading code. And a despreading circuit 27.

  The operation of the base station and the mobile station configured as described above will be described with reference to the timing charts of FIGS.

  FIG. 2 shows a state where the base stations 10 and the mobile station 20 are mutually performing spread spectrum communication based on the reference timings provided by the timers 12 and 22.

  In the base station 10, when the transmission data is input from the base station side control unit 11 to the spreading circuit 13, the transmission data is spread at the transmission timing given by the timer 12 in the spreading circuit 13 at the predetermined chip rate fc using the spreading code C 1. The signal is transmitted wirelessly from the antenna 14. Here, the timers 12 and 22 have the same cycle.

  At this time, the spreading circuit spreads the spectrum by multiplying the transmission data by the spreading code C1 with the clock fc of the chip rate generated by the timer 12. The reference timing of the timer 12 gives the timing at which the head of the spreading code C1 for spreading the transmission data spectrum is generated. Specifically, when the count value of the clock fc of the timer 12 is 0, the spread code C1 is generated so that the head of the spread code C1 is multiplied by the transmission data. When the count value is the maximum value, the end of the spread code C1 is multiplied by the transmission data, the count value is reset at the next clock, the count value becomes 0 again, and the beginning of the spread code C1 appears. ing.

  In this way, a signal having a periodicity (spread spectrum signal) generated based on the reference timing periodically provided by the timer 12 built in the base station 10 is wirelessly transmitted to the mobile station 20. A signal wirelessly transmitted from the base station 10 reaches the mobile station 20 after a propagation time Td proportional to the distance between the mobile station 20 and the base station 10.

  On the other hand, in the mobile station 20, similarly to the base station 10, the transmission data provided from the mobile station side control unit 21 to the spreading circuit 23 is spread spectrum by the spreading code C 2 based on the reference timing provided by the timer 22 of the own station, and 24.

  As described above, a signal (spread spectrum signal) having periodicity generated from the mobile station 20 to the base station 10 based on the reference timing periodically provided by the timer 22 built in the mobile station 20 is also transmitted from the base station 10. Wirelessly transmitted to The time required for a signal transmitted from the mobile station 20 to reach the base station 10 is the same as the transmission time from the transmission from the base station 10 to the mobile station 20 if the time lapse is small. Become.

  In the mobile station 20, the received signal received by the antenna 24 is input to the despreading circuit 27, and the despreading code C1 'generated by the despreading code generator 26 is input to the despreading circuit 27. The despreading code C1 'is generated by sequentially shifting the same spreading code C1 as the spreading code used for spectrum spreading on the transmitting side in the despreading code generator 26. That is, as shown in FIG. 2, the head of the spreading code C1 is adjusted to the timing when the count value of the timer 22 of the own station is 0 (reference timing), and the sampling value is set to the maximum value at the sampling period Ts until the count value is reset. Shift sequentially. At this time, the correlation output CR between the data sequence of the received signal and the despreading code C <b> 1 ′ is output from the despreading circuit 27 to the mobile station side control unit 21. The mobile station-side controller 21 detects the time when the largest correlation output CR is obtained. This correlation processing is called diffusion pattern matching of despreading.

  The time until the maximum value of the correlation output CR is obtained by the spreading pattern matching of the despreading in the mobile station 20 is based on the reference timing of the timer 12 of the base station 10 on the transmitting side and the timer of the mobile station 20 on the receiving side. The timer delay time from the reference timing of No. 22 and the propagation delay Td described above. The time until the maximum value of the correlation output CR is obtained with reference to the reference timing provided by the timer 22 of the mobile station 20 is defined as a phase difference T2 as a phase difference detected by the own station.

With the sampling rate fs set to N times the chip rate fc (N ≧ 1 integer), the phase difference T2 is obtained from the following equation from the number of shifts n until the maximum correlation output is detected.
Phase difference T2 = n × Ts (1)

  The base station 10 also performs despreading pattern matching on the signal received from the mobile station 20 based on the reference timing provided by the timer 12 of the base station 10 so that the reference timing provided by the timer 12 of the base station 10 can be obtained. The time until the maximum value of the correlation output CR is obtained based on the reference can be detected as the phase difference T1.

FIG. 3 shows the phase differences T1, T2 detected by the base station 10 and the mobile station 20, the timer shifts T01, T02, which are the time differences between the propagation delay Td and the reference timing. As shown in the figure, when synchronization is not established between communication stations (base stations and mobile stations), the phase difference Tn is expressed by the following equation, where T0n is the timer deviation of the transmission side with respect to the reception side. .
Phase difference Tn = transmission side synchronization deviation T0n viewed from the reception side + propagation time Td (2)

The deviation of the timer 12 of the base station 10 with respect to the mobile station 20 is represented by T02.
The deviation of the timer 22 of the mobile station 20 with respect to the base station 10 is represented by T01.
The phase difference when the base station 10 is on the transmitting side and the mobile station 20 is on the receiving side is a phase difference T2.
The phase difference when the mobile station 20 is on the transmitting side and the base station 10 is on the receiving side is a phase difference T1.
Then, there is the following relationship.
T02 + propagation time Td = phase difference T2 (3)
T01 + propagation time Td = phase difference T1 (4)

  When the timer 22 of the mobile station 20 is advanced by T01 with respect to the base station 10, the timer 12 of the base station 10 is delayed by T02 with respect to the mobile station 20.

Therefore, there is a relationship of T01 = −T02, and when Equations (3) and (4) are added, the timer deviation on the left side cancels out, and only the propagation time Td remains on the left side, and the base station 10 and the mobile station 20 Can be calculated.
Propagation time Td = (phase difference T1 + phase difference T2) / 2 (5)
Distance r = light speed × (phase difference T1 + phase difference T2) / 2 (6)

Further, if the equations (3) and (4) are subtracted, the propagation times Td on the left side cancel each other, and only the timer shift remains on the left side, so that the sync shift can be calculated.
T01 = (phase difference T1-phase difference T2) / 2 (7)
T02 = (phase difference T2-phase difference T1) / 2 (8)

The distance r can be obtained by the following equation by correcting the calculated timer deviation.
Distance r = light speed × (phase difference T1-timer shift T01) (9)
Distance r = light speed × (phase difference T2-timer shift T02) (10)

  When the mobile station 20 measures the distance to the base station 10, the base station 10 that has received the signal from the mobile station 20 uses the phase difference T01 detected based on the reference timing of its own timer 12 as transmission data as the base station. 10 to the mobile station 20.

  The mobile station 20 demodulates the received data relating to the phase difference T01 received from the base station 10 and acquires the phase difference T01 detected by the base station 10. On the other hand, the phase difference T2 based on the reference timing of the timer 22 of the own station is detected by the spread pattern matching of the despreading with the received data related to the phase difference T01.

  The mobile station side control unit 21 calculates the distance r from the mobile station 20 to the base station 10 based on the above equation (6). Alternatively, the timer deviation T02 of the base station 10 with respect to the mobile station 20 or the timer deviation T01 of the mobile station 20 with respect to the base station 10 is detected by the above equations (7) and (8). Alternatively, the relative distance r may be calculated by correcting the timer deviation based on Expression (10).

  Further, the timers 22 and 12 of the mobile station 20 and the base station 10 are adjusted using the timer shift T01 or T02 calculated by the equation (7) or (8). For example, in the base station 10, the base station-side control unit 11 adjusts the timer 12 by the timer deviation T02 with respect to the timer 22 of the mobile station 20. A similar matching operation may be performed in the mobile station 20.

  However, in a cellular system, since one base station communicates with many mobile stations, it is more convenient for system operation to adjust the timer of the mobile station to the timer of the base station.

After eliminating the timer deviation, the relative distance r may be calculated by the following equation.
Distance r = c × phase difference (11)
Where: c is a constant corresponding to the speed of light

(Embodiment 2)
By the way, in the spread spectrum method, normally, a spread code signal having the same cycle as the sample rate fs (symbol cycle Ts) is superimposed on all channels using the same value chip rate fc (cycle Tc). I have. In general, the amount of information Isr required for distance measurement is sufficiently smaller than the amount of information Isi transmitted in user information communication. Therefore, the bit length Nr (= spread code gain Gr) of the spreading code Cr to be superimposed on the ranging signal R is represented by The bit length Ni (= spread code gain Gi) of the spread code Ci to be superimposed on the signal I of the user information communication can be made sufficiently large.

  The product GP of the spreading code gain G and the transmission power P is defined as the effective transmission power PE. It is clear that the upper limit value of the effective transmission power PEr (= Gr · Pr) of the ranging signal R can be made sufficiently larger than the upper limit value PEimax = (Gi · Pimax) of the effective transmission power of the signal I of the user information communication. This means that the communicable radius Rrmax of the base station 10 and the mobile station 20 with respect to the distance measurement signal R is sufficiently longer than the communicable radius Rimax of the user information communication signal I as shown in FIG. Thus, by adjusting the transmission power Pr so as to cover the mobile station 20 to be measured (ranged), the mobile station 20 can communicate with the plurality of base stations 10. At this time, when comparing the effective transmission power PEr and PEimax, PEr> PEimax, but when comparing the spreading gain Gr and Gi, since Gr >> Gi, Pr << Pimax, and there is substantially no interference between the base stations 10. May be considered. Therefore, by implementing the above-described embodiment, the conventional problems described above under “Problems to be Solved by the Invention” can be solved. The above is the main principle of the present invention.

  In the second embodiment, an information communication service has already been put into practical use in a CDMA cellular mobile communication system, and a location detection service has been added thereto.

  As a method of the existing position detection service, a GPS system and an AOA (Angle of Arival) method have been put to practical use. However, adopting the GPS system introduces a system different from the cellular mobile communication system, and adds hardware for receiving a GPS signal and a position calculating device to the mobile station 20, and the The hardware configuration of the station 20 becomes complicated and the cost increases. Also, when the AOA method is adopted, the antenna of the base station 10 cannot be realized only by a non-directional stationary antenna, and a directional rotating antenna must be added, and the hardware configuration of the base station 10 becomes complicated. Increases costs.

  In this regard, if a positioning method based on the principle of triangulation is adopted, there is no need to introduce a system different from the cellular mobile communication system, and the current hardware configuration can be used as it is. However, when the positioning method based on the conventional principle of triangulation is employed, the above-described problem is involved, and it is necessary to solve this problem.

  Normally, the mobile station 20 performs its own location registration with respect to the nearest base station 10, so that the base station 10 that detects the relative distance from the mobile station 20 is the base station 10-0 that performs the location registration. And the base 10-i (i = 1 to 6) adjacent to the base station 10-0. The base station 10-0 with which the mobile station 20 performs position registration is defined as a main base station, and the base station 10-i adjacent to the main base station 10-0 is defined as a sub base station.

  FIG. 5 shows how the position of the mobile station 20 is detected by a total of three base stations, the main base station 10-0 and the two sub base stations 10-1 and 10-2.

  In the above description of the principle, the interference amount of the ranging signal R can be approximately ignored, but strictly speaking, the interference of the ranging signal R between the base stations is not zero. Although the interference of the distance measurement signal R can be approximately ignored, it is desirable to reduce the interference. To this end, the spreading code gain Gr (the bit length Nr of the spreading code Cr to be superimposed on the ranging signal R) may be increased, but the load on the hardware of the system increases. That is, the two have a trade-off relationship. Therefore, a method of determining the spreading code gain Gr will be described.

  Here, it is assumed that the base station 10 provides a ranging channel R for each mobile station 20 and detects the distance.

  For the sake of simplicity, in the practical cellular mobile communication system described above, communication obstacles are ignored and only direct wave communication is performed, and the base station 10 is arranged ideally. It is assumed that That is, the area is filled with regular hexagonal hexagonal communication cells, and the base station 10 is located in the center of the hexagon. The distance D between the base stations is constant.

P: transmission power of the desired wave radiated by the transmitter P (r): transmission power of the desired wave at a distance r from the transmitter G (= N): spreading code gain (= bit length of spreading code)
PE (= GP): Desired effective transmission power radiated from the transmitter r: Distance Ps (r): Received power after despreading of the desired wave at a distance r from the transmitter Pn: Despreading of interference wave Subsequent received power fd (r) = P (r) / P: function representing the state of attenuation of signal transmission power with distance r as a variable D: distance between adjacent base stations r0: main base station and mobile station Relative distance of

  The communication quality Q is defined as a ratio Ps / Pn (so-called S / N ratio) between the received power Ps of the desired wave after despreading and the received power Pn of the interference wave after despreading. There are many types of the communication quality Q depending on the definition, but the essence does not change since the communication quality Q is monotonically increasing with the S / N ratio.

The relationship between Ps and the arrival distance r of the desired wave is expressed by the following equation (12).
Ps (r) = GPPfd (r) (12)

Here, the product GP of the spreading code gain G and the transmission power P is defined as the effective transmission power PE.
Ps (r) = PE · fd (r) (13)

Conditions for receiving a desired wave at a distance r or more from the communication station with a predetermined communication quality Q1 or more can be expressed by the following equations (14) and (15).
Ps (r) / Pn ≧ Q1 (14)
PE ≧ Q1 · Pn / fd (r) (15)

When a desired wave transmitted at the effective transmission power PE1 from a point away from the distance r1 can be received with the quality Q1, the condition for receiving the desired wave transmitted from the point away from the distance r2 with the quality Q1 is expressed by the following equation (19). Can be represented by
PE1 = Q1 · Pn / fd (r1) (16)
PE2 ≧ Q1 · Pn / fd (r2) (17)
PE2 / PE1 ≧ fd (r1) / fd (r2) (18)
PE2 ≧ PE1 · fd (r1) / fd (r2) (19)

Since the main base station 10-0 is a base station whose location is registered by the mobile station 20, it is in a state where it can communicate with the mobile station 20. Therefore, the relative distance r0 between the main base station 10-0 and the mobile station 20 can be obtained. At this time, the effective transmission powers PEr0 and PEr0 'of the ranging signal R transmitted from the main base station 10-0 and the mobile station 20 to the partner station are also known. At least two of the six sub base stations 10-i (i = 1 to 6) adjacent to the main base station 10-0 are located between the base station 10-0 and the base station 10-i around the mobile station 20. It exists in a circle whose radius is the distance D. Accordingly, the sub base station 10-i transmits the ranging signal R with the effective transmission power PE obtained by the following equation (20), so that the mobile station 20 can receive the ranging signal R from at least two or more base stations 10-i. R can be received.
PE = PE0 · fd (R0) / fd (D) (20)

  The effective transmission power of the ranging signal R transmitted from the mobile station 20 to the sub base station 10-i can be obtained in a similar manner. In an ideal cellular mobile communication system, the distance Di between base stations is constant, but is not actually constant. However, the longest distance Dmax among the distances Di between the main base station 10-0 and the six adjacent sub base stations 10-i (i = 1 to 6) may be used.

  The mobile station 20 may move away from the base station 10 due to the movement, and the receiving side may not be able to receive the signal with the predetermined communication quality Q1 or more, even though the transmitting side is transmitting at the transmission power upper limit Pmax. . In this case, the spreading code gain G (= spreading code length N) may be increased to be equal to or higher than the communication quality Q1.

The spreading code gain G, the chip rate fc, and the symbol rate fs have a relationship represented by the following equation (21).
G = fc / fs (21)

  To increase the spreading code gain G, the chip rate fc may be increased or the symbol rate fs may be decreased. In a current cellular mobile communication system, there is a system in which a plurality of different symbol rates fs are mixed and fixed at a fixed chip rate fc. Therefore, it is easier to realize by fixing the chip rate fc and reducing the symbol rate fs. is there. In the current cellular mobile communication system, once the symbol rate fs is determined for each communication, the communication is continued at the same symbol rate thereafter. Further, the symbol rate fs is not changed just because the transmission at the upper limit of the transmission power cannot satisfy the predetermined communication quality.

The information rate Is expressed by the symbol rate fs, the signal communication cycle Tf, and the number of symbols of the signal has a relationship represented by the following equation (22).
fs ≧ Is / Tf (22)

  To reduce the symbol rate fs, the information amount Is may be reduced, or the communication cycle Tf may be increased.

  It is more reasonable to communicate from the beginning with the minimum amount of information Is and to increase the communication cycle Tf as necessary.

(Embodiment 3)
Embodiment 2 assumes that the base station 10 provides an individual ranging channel R for each individual mobile station 20 to detect the distance. However, when the number of positioning target mobile stations 20 is large. In this case, the number of ranging channels R increases and the radio resources to be used and the processing capability of the base station 10 increase. Therefore, it is assumed that the base station 10 transmits a ranging signal R to a plurality of mobile stations 20 in the form of a broadcast channel.

  The broadcast channel is a common channel for the base station 10 to broadcast common information to all the mobile stations 20 existing in its own cell. In the current cellular mobile phone system, a broadcast channel called a perch channel (Pearch Channel) for broadcasting information for location registration of a mobile phone is implemented. Note that position registration is different from position detection.

  If the base timers of the base station 10 and the mobile station 20 have been set to match, the mobile station 20 measures the reception timing of the ranging signal R and sets it as the phase difference Tm based on the above equation (11). The relative distance r between 10 and the own station can be obtained. Note that the timer adjustment can be performed based on the above equations (7) and (8).

  By the way, the ranging signal R must be receivable by the mobile station 20 existing in the immediate vicinity of the adjacent base station 10, and is not guaranteed by the perch channel P described above. Thus, the ranging broadcast channel R is set as a different channel R from the perch channel P, and the effective transmission power PEr of this channel R is made larger than the effective transmission power PEp of the perch channel P.

The base station of the cellular mobile telephone system is located at the center of a hexagonal hexagon, and it is guaranteed that the signal P of the perch channel P can be received within the circumcircle (radius D ') of the hexagon. The relationship between D and D 'is clearly the relationship of Expression (25) from FIG.
D '= length of one side of equilateral triangle ... (23)
D = length of a perpendicular drawn from the vertex of the equilateral triangle to the base × 2 (24)
D = √3 · D ′ (25)

Since the electric power of the radio wave attenuates in proportion to the power of −2 to the distance, the received power P (D) of the point at the distance D before despreading of the desired wave is the received power of the point at the distance D ′ before despreading. It is 1/3 of P (D '). Therefore, if the product of the spreading code gain Gr of the ranging signal R and the transmission power Pr, that is, the effective transmission power PEr is set to be 9 times or more the effective transmission power PEp of the signal P, the reverse of the point of the distance D of the ranging signal R is obtained. The spread received power Gr · Pr (D) is equal to or greater than the despread received power Gp · Pp (D ′) at the point of the distance D ′ of the signal P of the perch channel P, and the mobile station 20 measures the distance. It is guaranteed that the signal R can be received.
Gr · Pr ≧ 3 · Gp · Pp (26)
When Pr = Pp,
Gr ≧ 3 · Gp (27)

(Embodiment 4)
Next, a description will be given of the error of the distance measurement, which is the premise of the position measurement, and whether the present invention can be realized with the current wireless specification.

An electromagnetic wave is exchanged between the measuring device and the object to be measured, and a one-way propagation time T of the electromagnetic wave is measured, and the propagation speed of the electromagnetic wave (light speed c = 3.0 × 10 ⁸ m) is measured at the propagation time T. If multiplied, the distance can be calculated. At this time, the distance dx calculated by multiplying the time resolution dT of the measurement of the propagation time T by the speed of light is the distance resolution of the distance measurement. Conversely, dT calculated by dividing the speed of light from the allowable distance error dx is the allowable value of the time resolution.

  As an embodiment, a position detection system such as a locator and a navigator in a cellular mobile communication system can be realized. For example, it can be applied to emergency services 110 and 119 and search for lost children. In the United States, mobile phone operators are obliged to detect the location of a subscriber's mobile station with a certain degree of accuracy and probability.

  Assuming that the accuracy required for detecting the position (distance) of the cellular mobile phone is of the order of 60 m, the distance resolution of 60 m is converted to a time resolution of 200 nsec. Assuming that the mobile station 20 to be measured is mounted on a car and is moving at a speed of about 100 km / h, the time required for the car to travel 60 m is about 2.2 seconds. This value is about 10 million times the required time resolution of 200 nsec, and can be regarded as stationary.

  In the spread spectrum communication system, the time resolution for measuring the propagation time of a signal is a sample period when the chip is synchronized, and the above-mentioned 200 nsec is converted to a chip frequency of 5 MHz. IS95 has been put into practical use as a current cellular mobile communication system, and its chip rate is about 1.2 MHz. Therefore, the time resolution can be realized on an order by taking four times oversampling. That is, it is possible to simultaneously perform the call and the distance measurement with wireless specifications on the same order as the current spread spectrum communication method of IS95.

  For example, doubling the chip rate is easily achievable with current technology. In this case, the conversion time-time resolution of the allowable error of the distance measurement is 100 nsec. The distance conversion of 100 nsec is 30 m, and it takes about 1.1 seconds for a vehicle traveling at 100 km / h to travel 30 m. Therefore, as shown in FIG. 7, if the communication of the ranging signal R is performed at a period of about 1.1 seconds or more, the car 30 equipped with the mobile station 20 to be positioned may run out of the allowable error range. There is. Conversely, if the communication of the ranging signal R is performed at a cycle of 1.1 seconds or less, it is guaranteed that the vehicle 30 equipped with the mobile station 20 to be located will remain within the allowable error ΔR.

  Thus, it is reasonable to determine the communication cycle of the ranging signal R according to the speed V of the mobile station 20. Of course, instead of the speed V itself, the speed may be replaced with the assumed maximum speed Vmax of the mobile station 20 or Vmax ′ obtained by adding a predetermined margin to Vmax. Further, the mobile station 20 may be provided with a speed V detecting device, or the speed V may be notified to the mobile station 20 from a speed detecting device provided in the automobile 30. In addition, even if the mobile station 20 is not equipped with a speed detection device, a maximum speed selection button (for example, “walking”, “car”, “train”) is provided, and the user of the mobile station 20 presses the button to determine the speed. An upper limit expected value or an approximate value may be selected.

  The mobile station 20 obtains the upper limit value of the communication cycle of the ranging signal R based on the speed information V of the mobile station 20, determines a communication cycle Tfr convenient for the mobile station within the range, and notifies the network. If only reduction of the interference of the ranging signal R is considered, it is desirable that the communication cycle Tfr be longer. For simplicity of description, the communication cycle Tfr is set to 1 second here.

  In general, the amount of information necessary for distance measurement is sufficiently smaller than that of ordinary information communication. In particular, after adjusting the reference timers in the above equations (7) and (8), there is no information necessary for the distance measurement itself, and only the identification information of the mobile station 20 needs to be transmitted. Furthermore, in the spread spectrum communication system, the fact that the correlation output can be detected by performing despreading with a specific spreading code is equivalent to transmitting the identification information of the mobile station 20, and thus even the identification information is not necessary. Even if the identification information is sent for confirmation, the transmission rate of the ranging signal R is about 0.1 kbps, assuming that the information amount is about 100 bits in consideration of the redundancy. On the other hand, the transmission speed of the information communication signal of IS95 is about 14 kbps. The spread code gain Gr of the distance measurement signal R is calculated so as to obtain about 140 times the spread gain of the current IS95. This value is sufficiently larger than three times calculated by the above equation (27). Therefore, the present invention can be sufficiently realized with a wireless specification on the same order as the wireless specification of the cellular mobile communication system currently in practical use.

The mobile station 20 has the following formula:
fsr ≧ Isr / Tfr (28)
Where: fsr is the symbol rate of the ranging signal R
Isr determines a symbol rate fsr that is convenient for its own station within a range that satisfies the information amount condition represented by the number of symbols of the ranging signal R, and notifies the network via the base station 10.

The spreading code gain Gr and the symbol rate fsr are given by the following equations:
Gr = fc / fsr (29)
Thus, determining the symbol rate fsr is equivalent to determining the spreading gain Gr.

  If only consideration is given to reducing the amount of interference of the ranging signal R, the larger the spreading code gain Gr (proportional to the symbol period Tsr), the higher the spreading code gain is obtained and the lower the transmission power. Desirable. However, the spreading code length Nr cannot be longer than the bit length of the spreading code that can be realized by the transmitting / receiving means of the communication device. "Convenient for own station" means this.

When the symbol rate fsr is determined to be a value larger than Isr / Tfr, the Troff time of the following equation (31) is left. If the distance measurement signal R is turned off during this extra period, the amount of interference can be reduced and the power consumption can be reduced.
Tsr = 1 / fsr (30)
Troff = Tfr−Isr · Tsr (31)

  When the symbol rate fsr is Isr / Tfr, Troff becomes 0. In this case, the distance measurement signal R is always transmitted.

(Embodiment 5)
By writing a program for realizing the communication method described in the second embodiment and the distance measuring method described in the fourth embodiment into the memories of the control units 11 and 21 of the base station 10 and the mobile station 20, the above-described distance can be obtained. A distance detection device that executes the measurement method can be realized. That is, a distance detection device can be realized without changing the hardware configuration of an existing spread spectrum communication device. Examples of the memory include a semiconductor memory, a magnetic storage medium, an optical storage medium, and a magneto-optical recording medium.

  Also, by mounting this distance detecting device on a mobile station or a base station of a position detecting system, a position detecting device can be realized.

  If this distance detecting device is mounted on a car, a car navigator and a car locator can be realized.

(Embodiment 6)
In the sixth embodiment, position detection based on the above-described position detection method is performed a plurality of times between a vehicle equipped with an in-vehicle device having the distance measuring device and a network including a plurality of base stations 10. This is a speed detection device that detects the speed of the vehicle from a moving distance converted from a difference in position and a time difference between timings of position detection.

Velocity ^{V 2 = {(x2-x1} ) 2 + (y2-y1) 2 + (z2-z1) 2} / (t2-t1) 2 ... (32)
Here, (x1, y1, z1) is the position coordinate detected at time t1, and (x2, y2, z2) is the position coordinate detected at time t2.

  According to the sixth embodiment, the speed can be detected using the detected position.

  The present invention is not limited to the above embodiments, but encompasses all alterations, modifications, and variations. For example, in the embodiment of the present invention, the arrangement of base stations in an existing user information communication system is assumed to be ideal for the sake of simplicity, but of course, it is not ideal in reality. Therefore, it is necessary to give a predetermined margin to the mathematical expressions and numerical values described in the embodiment of the present invention. Formulas and numerical values corrected by adding and subtracting the power of the safety coefficient and the offset are naturally included in the present invention.

Functional block diagram of base station and mobile station capable of CDMA wireless communication according to Embodiment 1 of the present invention Timing chart of spectrum communication between base station and mobile station in FIG. FIG. 1 is a timing chart for explaining a phase difference detected between the base station and the mobile station. FIG. 7 is a diagram showing a state of a ranging signal for describing Embodiment 2 of the present invention. FIG. 7 is a diagram showing a state of a ranging signal for describing Embodiment 2 of the present invention. FIG. 10 is a diagram illustrating a state of a ranging signal for describing Embodiment 3 of the present invention. FIG. 9 is a diagram illustrating a relationship between the speed of a mobile station and a communication cycle of a ranging signal for describing Embodiment 4 of the present invention.

Explanation of reference numerals

10-0, 10-1, 10-2 Base station 11 Base station side control unit 12, 22 Timer 13, 23 Spreading circuit 15, 25 Sliding correlator 20 Mobile station 30 Vehicle

Claims (2)

The base station has a broadcast channel, and transmits a signal having periodicity based on a reference timing generated by a reference timer of the base station from the broadcast channel,
The mobile station receives a signal having the periodicity, detects the reception timing with a reference timer of the mobile station, and obtains a phase difference,
The base station receives a signal from the mobile station, detects a reception timing with a reference timer of the base station to determine a phase difference,
Further, a difference in reference timing between the mobile station and the base station is detected based on the phase difference obtained by the base station and the phase difference obtained by the mobile station, and the movement is performed based on the detected reference timing difference. A distance detection method comprising: adjusting a reference timer of a station to a reference timer of a base station; and detecting a relative distance from the counterpart station based on a phase difference of a signal received from the counterpart station.   Using the distance detection method according to claim 1, detecting a distance between the mobile station and each of the at least three base stations, and detecting a position of the mobile station based on the detected distance. Position detection method.

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