JP2009014691A - Positioning system by spectrum diffusion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positioning system performing synchronous time detection for precise positioning in the minimum hardware structure and power-saving. <P>SOLUTION: This positioning system comprises: while a moving station is transmitting a diffusion code in a predetermined cycle, a first detection means that detects a synchronism as a result of first detection by rough synchronization according to a signal received by a base station; and a second detection means that performs sampling of the signal received in a synchronism detection range determined based on the result of the first detection after the first detection and detects synchronism as a result of second detection by fine synchronization. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positioning system that performs precise positioning by synchronization acquisition using the characteristics of a spread code in wireless communication using a spread spectrum communication system. In particular, the present invention relates to a positioning system that performs power-saving and precise positioning by performing a first synchronization detection process based on coarse synchronization and a second synchronization detection process based on fine synchronization.

In a positioning system that estimates the position of a wireless communication terminal with high accuracy, it is essential to have precise positioning means. For example, GPS (Global Positioning System) measures the delay time of electromagnetic waves by detecting the phase of a spectrum spread signal, and performs positioning. In recent years, in GPS, as a means of performing precise positioning by spread spectrum, the incoming data sequence is sampled at a frequency not equal to an integer multiple or divisor of the data transfer rate (chip rate) of the incoming data sequence. There has been proposed a method of calculating a phase by storing a result as a digital data sequence and referring to a predetermined code sequence (see Patent Document 1).
JP-T-2001-510666

  In the positioning system disclosed in Patent Document 1, after sampling incoming data at a frequency slightly higher than the chip rate, the sampling result is sent to the shift register SR2, and the sampling result sampled at the chip rate is sent. The data is sent as a replica to the shift register SR1. When the correlation function is calculated for the shift registers SR1 and SR2 while shifting only the shift register SR2, the phase is calculated based on the significant increase in the correlation calculation result that occurs based on the difference in sampling frequency.

  Therefore, in the positioning system disclosed in Patent Document 1, in order to improve the positioning accuracy (phase detection accuracy), the difference between the chip rate and the incoming data sampling rate is set very small, and the setting state is maintained. The method of doing is mentioned. However, since it is difficult to continuously maintain the state where the difference between the chip rate and the sampling rate is set to be very small, the positioning accuracy in the positioning system has a technical limit.

  In addition, in order to perform precise positioning by spread spectrum, it is necessary to read the received signal with high resolution and detect the synchronization time. When this is realized with a digital circuit, it is necessary to sample the received signal at a high sampling rate and simultaneously perform synchronous detection in real time. Therefore, in order to perform precise positioning, hardware capability must be concentrated on the sampling process because high resolution is required. However, since synchronization calculation requires correlation calculation and calculation time, hardware capability cannot be concentrated on correlation calculation for synchronization detection, and it is difficult to continue synchronization detection with high resolution. is there.

  The present invention has been made in view of the above-described problems, and when the arrival time of a received signal necessary for synchronization detection can be grasped in advance, sampling processing is performed at a sampling rate that is higher by the time for performing synchronization detection. Focusing on the fact that precise synchronization time detection can be performed by performing synchronization detection (correlation calculation) over the sampled received signal over time, the first synchronization detection processing by coarse synchronization, An object of the present invention is to provide a positioning system that performs precise positioning by performing a second synchronization detection process based on fine synchronization at a higher sampling rate.

  Another object of the present invention is to provide a positioning system that performs precise synchronization time detection with a relatively simple configuration. Furthermore, since the present invention only performs the sampling process of the received signal at the high sampling frequency during the period limited to the second synchronization detection range, the sampling is always performed at the high sampling frequency in order to detect the synchronization time. It is an object of the present invention to provide a positioning system that can reduce the power consumption of a base station that performs synchronization time detection as compared with the case where it is performed.

  In order to achieve the above object, in the positioning system according to the present invention, a spreading code is transmitted from a mobile station at a predetermined period, and synchronization by coarse synchronization is detected as a first detection from a signal received by a base station. First detection means, and second detection means for sampling the signal received in the synchronization detection range determined based on the result of the first detection after the first detection, and detecting synchronization by fine synchronization as the second detection. In addition, the base station performs synchronization detection of the spreading code transmitted by the mobile station, detects the synchronization time, and performs precise positioning of the mobile station.

Specifically, the positioning system for performing the synchronization time detection according to the present invention,
A positioning system including a base station that receives a signal transmitted from a mobile station, and a positioning calculation unit connected to the base station through a network,
The mobile station
Signal transmission means for transmitting the spread code generated by the mobile station itself as the signal at a predetermined period;
The base station
Sampling means for receiving a signal from the mobile station and sampling the signal;
First detection means for detecting spreading code synchronization as a first detection from the first sampling result sampled by the sampling means;
Determining means for determining a synchronization detection range for the second detection based on the synchronization detection result information of the first detection means;
Second detection means for detecting synchronization of a spread code as the second detection from a second sampling result obtained by sampling a signal received from the mobile station in the synchronization detection range after the first detection;
The positioning calculation unit
Positioning calculation means for performing positioning based on synchronization detection result information obtained by the second detection means by at least three of the base stations,
The sampling frequency for the second detection is higher than the sampling frequency for the first detection.

  According to the above-described invention, the determination means for determining the synchronization detection range for the second detection based on the synchronization detection result information of the first detection means, and the synchronization detection of the signal received from the mobile station after the first detection The second detection means for detecting the synchronization of the spread code as the second detection from the second sampling result sampled in the range, so that the synchronization detection result of the first detection means can be used for precise positioning of the mobile station. Only the synchronization detection range determined for performing synchronization by the second detection means based on the information can be sampled. Therefore, the sampling period can be limited to a desired period.

  As a result, only the sampling for the second detection is sampled at a high sampling frequency, and the synchronization detection result information of the second detection unit is more accurately obtained based on the synchronization detection result information of the first detection unit. Therefore, precise positioning can be performed by the positioning calculation unit. In particular, in the sampling process for the second detection, since it is not always necessary to perform sampling at a high sampling frequency, the synchronization time detection in the base station can be performed with low power consumption, and positioning capable of positioning with low power consumption. A system can be realized.

  In order to detect the synchronization of the second detection means, it is difficult to detect the synchronization in real time by storing the second sampling result in the storage means and synchronizing the sampling result stored in the storage means. Even in this case, since synchronization can be detected, more precise positioning can be performed.

  As the positioning system according to the present invention, the determining means adds a new sampling start time and a sampling end time by adding an additional time to at least one of the sampling start time and the sampling end time obtained based on the synchronization detection result information. It is preferable to determine the synchronization detection range.

  According to the above-described invention, by sampling in the synchronization detection range, it is possible to reliably acquire the second sampling result that reliably includes the spreading code transmitted by the mobile station. Therefore, precise synchronization time detection can be performed and positioning can be performed.

  In the positioning system according to the present invention, it is preferable that the additional time is determined based on the clock pitch error and the sampling frequency of the first detection means and the second detection means.

  According to the above-described invention, since the synchronization detection range can be more accurately determined, the second sampling result reliably including the signal received from the mobile station in order to perform accurate synchronization time detection and positioning. Can be acquired reliably, and the synchronization time detection in the base station can be performed with less power consumption, and a positioning system capable of positioning with low power consumption can be realized. Here, the clock pitch error is a clock error caused by a difference in speed between the clocks provided in the mobile station and the base station. For example, when a clock provided in one station of the mobile station and the base station passes a unit time. In addition, it means a clock error caused by another station showing an elapsed time different from the unit time. Further, since the additional time is determined based on the sampling frequencies of the first detection means and the second detection means, a quantization error based on the difference between the sampling frequencies can be taken into consideration.

  As the positioning system according to the present invention, it is also preferable to perform wireless communication between a mobile station and a base station by a direct spread spectrum spread communication system or an ultra wideband wireless communication system. By using the direct spread spectrum spread communication system, it is possible not only to perform precise synchronization time detection and positioning, but also to ensure high communication quality and confidentiality.

  As a positioning system according to the present invention, the mobile station transmits a plurality of different consecutive PN codes as spreading codes in order to prevent a burst error which is a data error of a plurality of bits continuously present in the received signal. The first detection unit and the second detection unit preferably include a matched filter corresponding to each of the PN codes.

  According to the above-described invention, since the determination unit and the second detection unit are included, the synchronization by the second detection unit is performed based on the synchronization detection result information of the first detection unit in order to perform precise positioning of the mobile station. Only the synchronization detection range determined for performing the sampling can be sampled. Therefore, the sampling period can be limited to a desired period.

  As a result, only the sampling for the second detection is sampled at a high sampling frequency, and the synchronization detection result information of the second detection unit is more accurately obtained based on the synchronization detection result information of the first detection unit. Therefore, precise positioning can be performed by the positioning calculation unit. In particular, in the sampling process for the second detection, since it is not always necessary to perform sampling at a high sampling frequency, the synchronization time detection in the base station can be performed with low power consumption, and positioning capable of positioning with low power consumption. A system can be realized.

  The positioning system of the present invention performs synchronization time detection between a mobile station and at least three base stations to perform positioning of the mobile station. Specifically, the direct spread spectrum spread communication system is used as the wireless communication between the mobile station and the base station, and the base station receives the spreading code transmitted from the mobile station, thereby enabling precise synchronization time detection. And perform positioning. Therefore, it is necessary to sample a spread code to be transmitted at a high sampling frequency, perform quantization, detect synchronization, and calculate a more accurate synchronization time.

  Therefore, in the positioning system according to the embodiment of the present invention, the spreading code is transmitted from the mobile station at a constant cycle, and the first synchronization detection process based on the coarse synchronization and the second based on the fine synchronization based on the first synchronization detection result. A two-stage synchronization detection process called a synchronization detection process is performed, and precise synchronization time detection is performed. More specifically, the base station 30 determines a synchronization detection range defined from a sampling start time and a sampling end time for performing the second synchronization detection process based on the result of the first synchronization detection process. Then, synchronization time detection and positioning are performed based on the result of the second synchronization detection process. In the present embodiment, a PN code (Pseudo Noise code) is used as the spreading code. Below, the structure of the positioning system by embodiment of this invention is demonstrated.

<< Configuration >>
<Positioning system 10>
FIG. 1 is a schematic configuration diagram of a positioning system 10 according to the present invention. The positioning system according to the present invention includes a mobile station 20, a base station 30 (30A, 30B, 30C, 30D), and a positioning server 40. The In order to perform positioning of the mobile station 20, it is necessary to detect the synchronization time between the mobile station 20 and at least three base stations. The configuration of positioning system with two base stations is shown.

  Each base station obtains synchronization detection result information in each base station by detecting the synchronization of the spreading code transmitted as a signal by the mobile station 20 and measuring the synchronization time by the clock of each base station. Then, the synchronization detection result information obtained for each base station is transmitted to the positioning server 40 together with the base station number. The positioning server 40 performs positioning of the mobile station 20 based on the synchronization detection result information received from each base station and the position of the base station.

<Mobile station 20>
FIG. 2 is a schematic configuration diagram of the mobile station 20 that is a positioning target in the positioning system of the present embodiment. The mobile station 20 includes a clock 22, a controller 24, a spread code generator 26, and a transceiver circuit 28. The clock 22 generates time information from a clock signal generated by a clock generator (not shown) of the mobile station 20. The controller 24 monitors the time information generated by the clock 22 and transmits a clock signal used for generating a spreading code to the spreading code generator 26 at the spreading code generation time. The spread code generator 26 generates a spread code according to the clock signal received from the controller 24 and transmits it to the transceiver circuit 28. The transceiver circuit 28 is a circuit that modulates the spread code received from the spread code generator 26, and the modulated spread code is transmitted via an antenna.

  Therefore, in this embodiment, when positioning the mobile station 20, the base station information is not transmitted from the mobile station 20, and only the spreading code is transmitted. Then, as will be described later, the time at which the signal transmitted from the mobile station 20 arrives at the base station 30 is calculated based on the synchronization acquisition using the properties of the spreading code.

(Controller 24)
The controller 24 sets the start time (spread code generation start time) and end time (spread code generation end time) at which the spread code generator 26 generates a spread code by monitoring the time information generated by the clock 22. The clock signal output from the clock 22 is transmitted to the spread code generator 26 between the spread code start time and the spread code end time. As a result, the spread code generator 26 generates a spread code by taking a timing using the received clock signal from the spread code generation start time to the spread code generation end time.

(Spreading code generator 26)
In the spreading code generator of this embodiment, a PN code (Pseudo Noise code) is generated as a spreading code. It is known that a spread code generator for generating a PN code can be composed of a shift register and an adder (exclusive OR). Note that the spreading code is not limited to the PN code, and the autocorrelation value is large when the phase difference is zero, and the autocorrelation value is sufficiently small when the phase difference is other than zero, and the cross-correlation values between the codes are all in the phase difference. A sufficiently small code is sufficient. For example, a Gold code generated by the circuit of the spread code generator shown in FIG. 3 can also be used as the spread code.

  The shift register of the spread code generator 26 is composed of a plurality of flip-flops, and takes the timing using the input clock signal to shift the value of the internal flip-flop and generate a spread code. The configuration of the spread code generator is the same in the mobile station 20 and each base station 30. Further, the setting of the initial value is the same in the mobile station 20 and each base station 30. Therefore, the mobile station 20 and each base station 30 can generate the same spreading code.

Further, in the spread code generator 26 of the present embodiment, the end timing of the PN code generated as a spread code, that is, the end timing of the generated PN code for one period is set as the time of the clock 22 in the mobile station 20. It is set so that every P seconds, for example, P = 1 second, on an information basis. Therefore, the mobile station 20 can transmit the spreading code to the base station 30 every P seconds. 4, as a specific example, the code period T _S of the PN code 1m sec, in the case of setting the interval P of the generation end timing of the PN code in one second, and a spreading code generation end time spreading code generation start time Show.

(Clock signal transmission processing of controller 24)
The controller 24 transmits a clock signal to the spread code generator 26 from the spread code generation start time to the spread code generation end time so that the PN code shown in FIG. 4 is generated by the spread code generator 26. FIG. 5 is a flowchart for explaining processing in which the controller 24 transmits a clock signal to the spread code generator 26 from the spread code generation start time to the spread code generation end time in order to generate a PN code for one cycle. Indicates.

  First, it is determined whether or not the time information generated by the clock 22 is a spread code generation start time (step S10). If it is determined in step S10 that the time information is not the spread code generation start time (NO), the process of step S10 is repeated. Therefore, a clock signal transmission process described later is executed only when the time information reaches the spread code generation start time.

  If it is determined in step S10 that the time information is the spread code generation start time (YES), transmission of the clock signal to the spread code generator 26 is started (step S12), and the time information is the spread code generation end time. It is determined whether or not there is (step S14). If it is determined in step S14 that the time information is not the spread code generation end time (NO), the processes in steps S12 to S14 are repeated. Therefore, it is possible to continue transmission of the clock signal to the spread code generator 26 until the time information reaches the spread code generation end time.

  In step S14, when it is determined that the time information is the spread code generation end time (YES), the transmission of the clock signal to the spread code generator 26 is ended (step S16), and the reset for resetting the shift register is executed. The signal is transmitted to the spread code generator 26 (step S18). Thus, the clock signal is transmitted from the controller 24 to the spread code generator 26 from the spread code generation start time to the spread code generation end time, and the timing is determined using the clock signal received by the spread code generator 26. As a result, it is possible to generate a PN code for one period based on the set time.

(Time processing of controller 24)
The controller 24 must set a spread code generation start time and a spread code generation end time in order to generate a PN code for one period based on a predetermined time. FIG. 6 is a flowchart for explaining the setting process of the spread code generation start time and the spread code generation end time executed in the controller 24. The spread code generation start time and the spread code generation end time are in accordance with FIG. It is determined by the following procedure.

First, the controller 24 acquires the current time TIM from the time information (step S20). Then, a value obtained by multiplying the value obtained by rounding up the decimal point of TIM / P by _P is set as TIM _P (step S22). Here, P is a PN code generation interval. Next, “TIM _P− TIM” is compared with a constant T _m (step S24). Here, the constant T _m is a processing time required to actually transmit the spread code from the determination of the spread code generation start time and the spread code generation end time, and is a value determined in advance depending on the system configuration. is there. When it is determined in step S24 that “TIM _P− TIM” is equal to or less than the constant T _m (NO), the spread code generation end time TIM _P is determined based on the current time TIM, and the spread code generation end time is determined. Since the spread code cannot be transmitted, it is necessary to newly acquire the current time, so the process returns to step S20 to newly acquire the current time. On the other hand, if it is determined in step S24 that “TIM _P- TIM” is greater than the constant T _m (YES), the spreading code generation end is determined even if the spreading code generation end time TIM _P is determined based on the current time TIM. Since the problem that the spread code cannot be transmitted at the time does not occur, the process proceeds to step S26 and the spread code generation start time is set. In step S26, after setting the _"TIM P -T _S" as a spreading code generation start time is set to "TIM _P" as the spreading code generation end time (step S28). Here, “T _S ” refers to the time representing the period of the spreading code. Accordance with the above flowchart (FIG. 6), 1 m sec code period T _S of the PN code, if you set the interval P of the PN code generation end timing to 1 second, the spreading code generation start time and spreading code generation completion shown in FIG. 4 You can set the time.

<Base station 30>
FIG. 7 is a schematic configuration diagram of the base station 30 that detects the synchronization time of the spreading code transmitted by the mobile station 20. The base station 30 includes a transceiver circuit 32 and a synchronization time detection unit 34. The transceiver circuit 32 demodulates the signal received via the antenna and transmits the demodulated signal to the synchronization time detection unit 34. The synchronization time detection unit 34 performs a first synchronization detection process based on the coarse synchronization and a second synchronization detection process based on the fine synchronization based on the first synchronization detection result, that is, the result of the first synchronization detection process. A synchronization detection range defined by the sampling start time and the sampling end time for performing the second synchronization detection process is determined based on the result, the second synchronization detection process is performed, and the result of the second synchronization detection process is determined. Based on this, the synchronization time of the spreading code transmitted by the mobile station 20 is detected.

  A block diagram of the synchronization time detection unit 34 is shown in FIG. First, the signal demodulated in the transceiver circuit 32 after being transmitted from the mobile station 20 is sampled and quantized based on a sampling clock signal having a predetermined different sampling frequency. 34 quantizers 120 and 150 are transmitted. Then, the first synchronization detection process is performed to determine the synchronization detection range for performing the second synchronization detection process. Therefore, the signal quantized by the quantizer 120 is transmitted to the matched filter 122. Further, the signal quantized by the quantizer 150 is transmitted to the matched filter 154 in order to perform the second synchronization detection process based on the result of the first synchronization detection process.

  Then, an autocorrelation value between the signal quantized by the quantizer 120 and the signal obtained by quantizing the spread code generated by the spread code generator 110 by the quantizer 112 is calculated, and the first synchronization detection is performed. The processing is performed in the sample time calculation unit 130, and a synchronization detection range for performing the second synchronization detection process is determined.

  On the other hand, in order to perform the second synchronization detection process in the synchronization detection range determined by the sample time calculation unit 130, the signal quantized by the quantizer 150 and the spread code generated by the spread code generator 110 are quantized. The auto-correlation value with the signal quantized in the counter 114 is calculated, and the second synchronization detection process is performed in the synchronization time calculation unit 160. Below, each structure of the synchronous time detection part 34 is demonstrated.

(Clock generator 100)
The clock generator 100 generates a clock signal that serves as a reference for the synchronization time detection process performed in the synchronization time detection unit 34. Then, the generated clock signal is transmitted to the clock generators 102, 104, 106 and the clock 108. Therefore, as will be described later, the first sampling clock signal used for the first synchronization detection process generated in the clock generator 102 and the second sampling detection signal generated in the clock generator 104 are used. Since the sampling clock signal is generated based on the common clock signal, a synchronization shift based on the clock signal can be prevented between the first synchronization and the second synchronization.

(Clock generator 102)
The clock generator 102 based on a clock signal transmitted from the clock generator 100 generates a first sampling clock signal of the first sampling frequency cl ₁₀₂ used in the first synchronization detection processing. The first sampling clock signal is transmitted to the quantizer 120 for sampling and quantizing the signal demodulated in the transceiver circuit 32, and the spreading code generated by the spreading code generator 110 is sampled and quantized. Therefore, it is also transmitted to the quantizer 112.

(Clock generator 104)
Based on the clock signal transmitted from the clock generator 100, the clock generator ₁₀₄ generates a second sampling clock signal having the second sampling frequency cl ₁₀₄ used for the second synchronization detection process. The second sampling clock signal is transmitted to the quantizer 150 in order to sample and quantize the signal demodulated in the transceiver circuit 32, and the spreading code generated by the spreading code generator 110 is sampled and quantized. In order to do so, it also transmits to the quantizer 114. The second sampling frequency is set higher than the first sampling frequency.

(Clock generator 106)
Based on the clock signal transmitted from the clock generator 100, the clock generator 106 generates a clock signal of the clock frequency cl ₁₀₆ that determines the chip rate of the spreading code generated by the spreading code generator 110, and the spreading code generator 110. Here, the clock frequency cl ₁₀₆ is set so that the relational expression of cl ₁₀₆ = f _P is established in relation to the chip rate f _P of the spreading code generated in the mobile station 20.

(Clock 108)
The clock 108 generates time information indicating the time of the base station based on the clock signal transmitted from the clock generator 100. A sampling time calculator 130 for performing a first synchronization detection process and calculating a sampling start time and an end time for defining a synchronization detection range for the second synchronization detection process based on the synchronization detection result; In order to perform the synchronization process 2, time information is transmitted to the sampling control signal generator 140 that transmits the sampling start signal and the sampling end signal to the quantizer 150.

(Spreading code generator 110)
Since the spread code generator 110 and the spread code generator 26 of the mobile station 20 described above have the same configuration and initial value settings, the mobile station 20 and each base station 30 generate the same spread code. can do.

  The positioning system of the present embodiment includes at least a communication mode for communicating data and a positioning mode for measuring the position of the mobile station. The system mode is switched from the communication mode to the positioning mode and transmitted from the positioning server 40. When the spread code generation control signal is received, the spread code generator 110 generates a spread code. The spreading code generator 110 then samples the generated spreading code with the first sampling clock signal having the first sampling frequency and performs quantization on the quantizing unit 112 to further quantize the second sampling frequency. A sampled clock signal is sampled and transmitted to the quantizer 114 for quantization.

(Quantizer 112)
The quantizer 112 samples the spread code generated by the spread code generator 110 based on the first sampling clock signal, and performs quantization. The first sampling clock signal is a signal used for sampling and quantizing the demodulated reception signal by the quantizer 120 and also a signal used for sampling and quantizing the spreading code. . Therefore, an autocorrelation value between the signal quantized by the quantizer 120 and the spread code quantized by the quantizer 112 is calculated using a matched filter 122 described later, and the sample time calculation unit 130 calculates the autocorrelation value. 1 synchronization detection can be performed.

(Quantizer 114)
The quantizer 114 samples the spread code generated by the spread code generator 110 based on the second sampling clock signal, and performs quantization. The second sampling clock signal is a signal used for sampling and quantizing the demodulated received signal by the quantizer 150 and also a signal used for sampling and quantizing the spreading code. . Therefore, an autocorrelation value between the signal quantized by the quantizer 150 and the spread code quantized by the quantizer 114 is calculated using a matched filter 154 described later, and the synchronization time calculation unit 160 calculates the first correlation value. 2 synchronization detection can be performed, and synchronization time detection can be performed.

(Quantizer 120)
The quantizer 120 samples and quantizes the signal demodulated by the transceiver circuit 32 based on the first sampling clock signal generated by the clock generator 102. Specifically, the received signal of the chip rate f _P is first sampled at the first sampling frequency cl ₁₀₂ (= n ₁ · f _P ) Hz and quantized. The signal quantized by the quantizer 120 is input to the matched filter 122.

(Matched filter 122)
The matched filter 122 performs matched filter processing for calculating an autocorrelation value between the spread code quantized by the quantizer 112 and the signal output from the quantizer 120, and calculates the calculated autocorrelation value as a sample time. To the unit 130. FIG. 9 shows the configuration of the matched filter 122. Since the signal quantized by the quantizer 120 and the spread code quantized by the quantizer 112 are handled as digital information, the matched filter 122 can be easily configured using a shift register. Incidentally, r ₁ in FIG. 9 is a ratio of the chip rate in the first synchronization process, representing the resolution in the first synchronization detecting process.

(Sample time calculation unit 130)
The sample time calculation unit 130 detects the time when the autocorrelation value peaks from the autocorrelation value of the autocorrelation function output from the matched filter 122 and the time information output from the clock 108, and sets it as the synchronization time. A sampling start time and a sampling end time are calculated based on the calculated synchronization time. Then, the calculated sampling start time and sampling end time are output to the sampling control signal generator 140 and the synchronization time calculation unit 160.

(Sampling control signal generator 140)
The sampling control signal generator 140 is a start signal that causes the quantizer 150 to start quantization from the sampling start time and sampling end time calculated by the sample time calculation unit 130 and the time information transmitted from the clock 108. An end signal for terminating quantization is generated and transmitted to the quantizer 150.

(Quantizer 150)
The quantizer 150 samples and quantizes the signal demodulated in the transceiver circuit 32 based on the second sampling clock signal of the second sampling frequency generated in the clock generator 104. Specifically, the received signal of the chip rate f _P is second-sampled and quantized at the second sampling frequency cl ₁₀₄ (= n ₂ · f _P ) Hz. The synchronization detection range in which the received signal is quantized is defined based on the sampling start signal and the sampling end signal received from the sampling control signal generator 140. The signal quantized by the quantizer 150 is output to and stored in the memory or register 152.

(Memory or register 152)
The memory or register 152 stores the signal quantized by the quantizer 150. This is because the quantized signal is stored in the memory or the register 152 even when it is difficult to perform the correlation calculation for performing the second synchronization detection process in real time at high speed, and the stored signal is offline. This is for performing correlation calculation. As a result, the second sampling set high with respect to the first sampling frequency capable of real-time synchronization detection processing without storing the signal quantized by the quantizer 120 in the first synchronization detection processing in the memory. In terms of frequency, even if the amount of information of the signal quantized by the quantizer 150 becomes large and the second synchronization detection process in real time is difficult, the accurate synchronization detection process can be surely performed.

(Matched filter 154)
The matched filter 154 performs matched filter processing for calculating an autocorrelation value between the spread code quantized by the quantizer 114 and the signal quantized by the quantizer 150 and stored in the memory or the register 152. The obtained autocorrelation value is output to the synchronization time calculation unit 160. FIG. 10 shows the configuration of the matched filter 154. Since the signal quantized by the quantizer 150 and stored in the memory or register 152 and the spread code quantized by the quantizer 114 are handled as digital information, the matched filter 154 is similar to the matched filter 122 in that the matched filter 154 A simple configuration using a shift register is possible. Note that r _{2 in} FIG. 10 is a ratio to the chip rate in the second synchronization detection process, and represents the resolution of the second synchronization process. Further, r ₂ is set to a sufficiently large value as compared with r ₁ .

(Synchronization time calculation unit 160)
The synchronization time calculation unit 160 performs synchronization detection from the autocorrelation value of the autocorrelation function output from the matched filter 154, and calculates the synchronization time from the synchronization detection result and the sampling start time output from the sample time calculation unit 130. To do.

<Positioning server 40>
The positioning system of the present embodiment includes a positioning server 40 that performs positioning of the mobile station 20 based on the synchronization detection time calculated by at least three base stations and the position of each base station. In addition, the positioning system of the present embodiment includes at least a communication mode and a positioning mode. When the system mode is switched from the communication mode to the positioning mode and the spreading code generation control signal is transmitted from the positioning server 40 to the spreading code generator 110, the spreading code generator 110 that has received the spreading code generation control signal Generate a sign.

<< Positioning process >>
In the positioning system according to the present embodiment, direct spread spectrum spreading is possible in order to enable precise positioning as wireless communication between the mobile station 20 and the base station 30 and to ensure high communication quality and confidentiality. Use the communication method. Then, positioning of the mobile station 20 is performed based on the synchronization detection result information of at least three base stations that have received the spread code (PN code) transmitted from the mobile station at a fixed period. Therefore, the base station 30 needs to sample the received PN code at a high sampling frequency, perform quantization, perform synchronization detection, and calculate a more accurate synchronization time.

  Therefore, the synchronization time detection process of the positioning system of the present embodiment uses the nature of the spread code, performs the first synchronization detection process and the second synchronization detection process, and calculates an accurate synchronization time. . More specifically, in the first synchronization detection process, a sampling start time and a sampling end time that define synchronization detection ranges for performing synchronization (coarse synchronization) at a low sampling frequency and performing the second synchronization detection process, And the signal quantized by the quantizer 150 for the second synchronization detection process, the sampling start time, and the like are stored in the memory or register 152. Then, in the second synchronization detection process, synchronization (fine synchronization) is performed on the signal that is the sampling result stored in the memory or register 152, and accurate synchronization time is calculated based on the second synchronization detection process. Is to do.

  In the positioning system of the present embodiment, the synchronization time is detected when the system mode set by the positioning server 40 is a positioning mode different from the communication mode. In the positioning mode, baseband information is not transmitted from the mobile station 20 in order to reduce the amount of sampling data.

  Below, the positioning process of the positioning system which concerns on this embodiment is demonstrated using the flowchart of FIG.

(Spread code generation control signal transmission processing)
First, in the positioning system of this embodiment, when the system mode is the positioning mode, the spreading code transmitted from the mobile station 20 as a signal using the PN code generated by the spreading code generator 110 of the base station 30 is used. The synchronization is detected, and the synchronization time by the clock of each base station is measured. Accordingly, the positioning server 40 switches the system mode to a positioning mode for positioning, and transmits a spreading code generation control signal to the spreading code generator 110 of the base station 30 (step S60).

(Spread code generation processing)
The spread code generator 110 of the base station 30 that has received the spread code generation control signal takes a timing using the clock signal obtained by the clock generator 106 to thereby obtain a spread code generator composed of a plurality of shift registers. The value of the flip-flop inside 110 is shifted to generate a spreading code (step S40). Here, the frequency cl ₁₀₆ of the clock signal obtained by the clock generator 106 is a value obtained from cl ₁₀₆ = f _P (chip rate) in relation to the chip rate f _P.

(Transmission process of PN code for first synchronization detection process)
While the positioning system mode is the positioning mode, the mobile station 20 transmits a PN signal as a spreading code at a predetermined cycle (step S30). Regarding the transmission timing, the end timing of the PN code (PN code for one cycle) is set so that the time information of the clock 22 in the mobile station 20 is every P seconds, for example, P = 1 second (FIG. 4). ).

  In order to generate one period of PN code, the controller 24 of the mobile station 20 sends a clock signal to the spread code generator 26 from the spread code generation start time to the spread code generation end time. Transmit (FIG. 5). Also, in order to generate one period of PN code based on a predetermined time, a spread code generation start time and a spread code generation end time are set according to the flowchart of FIG.

(First sampling process)
The PN code generated by the spread code generator 26 of the mobile station 20 is modulated by the transceiver circuit 28 and then transmitted from the antenna. In the base station 30, the received signal is demodulated by the transceiver circuit 32, and the synchronization time detector 34, more specifically, the quantizer 120 for the first synchronization detection process, and the second synchronization detection process. To the quantizer 150.

In the quantizer 120, first, the received signal is sampled at a first sampling frequency cl ₁ (= cl ₁₀₂ ) Hz and subjected to a first sampling process for quantization (step S42). Then, the signal quantized by the quantizer 120 is transmitted to the matched filter 122. Here, the first sampling frequency cl ₁₀₂ is set so that the relational expression of cl ₁₀₂ = n ₁ · f _P is established in relation to the chip rate f _P of the spreading code generated by the mobile station 20. Incidentally, n ₁ is an integer, in the first synchronous detection processing, selecting and determining as correlation calculation to calculate an autocorrelation value of the autocorrelation function becomes possible operations in real time.

(First synchronization detection process)
After executing the first sampling process (step S42), the signal quantized by the quantizer 120 in real time without storing the signal quantized by the quantizer 120 in a memory or the like, and the quantizer The auto-correlation value with the PN code quantized by 112 is calculated using the matched filter 122, and a first synchronization detection process is performed in which the sample time calculation unit 130 calculates the time at which the auto-correlation value peaks. (Step S44). The first synchronization detection resolution, as described above, in the first sampling processing, since doing sampling quantized by the first sampling frequency _{cl 102 (= n 1 · f} P) Hz, chip time (= 1 / _{f P)} becomes 1 and _{n 1} minute of.

(Second synchronization detection processing sampling time calculation processing)
The time at which the autocorrelation value peaks is calculated from the autocorrelation value of the autocorrelation function calculated by the first synchronization detection process (step S44) and the time information output from the clock 108, and the calculated peak Sampling start time t _2SS and sampling end time t _2Sf that define the synchronization detection range for the second synchronization detection processing are calculated based on the time of forming (step S46). Note that the sampling control signal generator 140 uses the quantizer 150 to calculate the sampling start time t _2SS and the sampling end time t _2Sf that define the synchronization detection range for the second synchronization detection process and the time information. A start signal for sampling and starting quantization and an end signal for ending are transmitted to the quantizer 150.

Processing for calculating the sampling start time t _2SS and the sampling end time t _2Sf will be described with reference to FIG. FIG. 12 is a flowchart for calculating the sampling start time t _2SS and the sampling end time t _2Sf .

First, in order to calculate the sampling start time t _2SS and the sampling end time t _2Sf , the sample time calculation unit 130 uses the time when the peak is detected in the autocorrelation value output from the matched filter 122 as the first synchronization detection process. to set the synchronization time _{t 1a} (step S70). Next, the sampling start time t _2ss (= t _1a −t _2ssp + P−T _s ) is calculated (step S72). Here, t _2ssp represents the second pre-synchronization spare time, P represents the PN code generation interval, and T _s represents the code period. Further, the sampling end time t _2sf (= t _1a + t _2sfp + P) is calculated (step S74). Here, t _2sfp represents the second post-synchronization spare time.

Note that a new pre-synchronization side spare time t _2ssp and a second post-synchronization side spare time t _2sfp are added to the synchronization detection range defined by the sampling start time t _2ss and the sampling end time t _2sf. By setting the correct synchronization detection range and sampling within the set synchronization detection range, it is possible to reliably acquire the second sampling result including the spread code transmitted as a signal from the mobile station. Therefore, precise synchronization time detection and positioning can be performed. The two spare times are clock pitch errors, which are clock errors caused by differences in the speeds of the clocks provided to the mobile station and the base station, that is, when the clock provided to one of the mobile station and the base station has passed a unit time. In addition, it is determined in consideration of a clock pitch error caused by other stations indicating an elapsed time different from the unit time, a quantization error based on a difference in sampling frequency between the first detection means and the second detection means, and the like.

  Therefore, since the synchronization detection range can be more accurately determined, in order to perform precise synchronization time detection and positioning, a sampling result that reliably includes a spreading code transmitted as a signal from the mobile station is surely obtained. In addition to being able to acquire, the synchronization time detection in the base station can be performed with less power consumption, and a positioning system capable of positioning with low power consumption can be realized.

(Transmission process of PN code for second synchronization detection process)
Since the mobile station 20 transmits a PN signal as a spread code at a predetermined cycle, the mobile station 20 transmits the first synchronization detection processing PN code, and then transmits the second synchronization detection processing PN code (step S32). ). In the present embodiment, the end timing of the PN code (PN code for one cycle) is set to the time information of the clock 22 in the mobile station 20 every P seconds (FIG. 4).

(Second sampling process)
In the base station 30 that has received the signal transmitted from the mobile station 20, the transceiver circuit 32 demodulates the received signal, and the quantizer 120 for the first synchronization detection process and the second synchronization detection process. To the first quantizer 150.

In the quantizer 150, first, the synchronization detection range for the second synchronization detection process calculated based on the result of the first synchronization detection process (step S44), that is, the sampling start time _t2SS and the sampling end time. between t _2SF, the received signal, a second sampling frequency _cl 2 _{(= cl} 104) second sampling processing for sampling quantized in Hz (step S48). Then, the signal quantized by the quantizer 150 is transmitted to the matched filter 154. Here, the second sampling frequency cl ₁₀₄ is set so that the relational expression of cl ₁₀₄ = n ₂ · f _P is established in relation to the chip rate f _P of the spreading code generated by the mobile station 20. Note that n ₂ is an integer sufficiently larger than n ₁ . Therefore, the second sampling frequency cl ₁₀₄ is sufficiently higher than the first sampling frequency cl ₁₀₂ , and the second synchronization detection process can perform a more accurate synchronization detection process compared to the first synchronization detection process. To do.

  In addition, since the first sampling clock signal and the second sampling clock signal use a common clock, a synchronization shift occurs between the first sampling process and the synchronization detection process and the second sampling process and the synchronization detection process. Does not occur.

(Storage processing of quantized received signal)
Since the signal quantized by the quantizer 150 has a large amount of information compared to the signal quantized by the quantizer 120 for the first synchronization detection process (step S44), the correlation is performed at high speed. It is difficult to perform synchronization detection processing that requires computation in real time. Therefore, the signal quantized by the quantizer 150 is stored in the memory or register 152 (step S50).

(Second synchronization detection process)
The autocorrelation value between the signal quantized by the quantizer 150 and stored in the memory or register 152 and the PN code quantized by the quantizer 114 is calculated using the matched filter 154, and the autocorrelation is calculated. A second synchronization detection process is performed in which the time at which the value reaches a peak is calculated by the synchronization time calculation unit 160 (step S52). Since the second synchronization detection resolution is sampled and quantized at the second sampling frequency cl ₁₀₄ (= n ₂ · f _P ) Hz in the second sampling process as described above, the chip time It becomes n _{1/2 of} (= 1 / f _P ).

(Synchronization time calculation process)
The synchronization time calculator 160 calculates the synchronization time at each base station from the autocorrelation value of the autocorrelation function output from the matched filter 154 and the sampling start time t _2SS output from the sample time calculator 130. A synchronous time calculation process is executed (step S54). Specifically, the second synchronization detection time is calculated by detecting the sampling start time t _2SS and the time from the sampling start time t _2SS until the autocorrelation value of the autocorrelation function shows a peak value.

Here, using FIG. 13, in the synchronization detection range for the second synchronization detection process from the sampling start time t _2ss to the sampling end time t _2sf , the received signal quantized by the quantizer 150 and spread A method of calculating the second synchronization detection time from the b _pn bit PN code (replica) generated by the code generator 110 and quantized by the quantizer 114 will be described. Since the received signal quantized by the quantizer 150 during the period of the synchronous detection range from the sampling start time t 2 _ss to the sampling end time t 2 _sf includes a spreading code (PN code) with one code period T _s It is possible to measure the maximum value of the autocorrelation value of the autocorrelation function in the received signal. Therefore, the synchronization time t _2a can be calculated from the sampling start time t _2ss of the second synchronization detection process and the bit number at which the autocorrelation value in the received signal sampled for the second synchronization detection becomes a maximum value. it can.

Specifically, the PN code (replica) is b _pn bit, and the received signal quantized by the quantizer 150 for the second synchronization detection processing from the sampling start time t _2ss by the matched filter 154 is PN code is shifted every 1bit relative (replica) by calculating the autocorrelation values of the autocorrelation function, it measures the bit number b _2a autocorrelation value becomes the maximum value. Therefore, the synchronization detection time _{t 2a (= t 2ss + (} b pn + b 2a) / cl 104) can be calculated. Here, cl ₁₀₄ is the second sampling frequency of the second sampling clock signal used for the second synchronization detection processing based on the clock signal transmitted from the clock generator 100 in the clock generator 104.

(Positioning process)
The synchronization time calculated in the synchronization time calculation process (step S54) is transmitted to the positioning server 40 together with the base station number. Then, positioning of the mobile station 20 is performed based on the synchronization detection time of the spreading code transmitted by the mobile station 20 calculated for at least three base stations (step S62).

Specifically, the positioning system calculates the coordinates (x, y) of the mobile station 20 by solving the following three simultaneous equations, and sets the coordinates (x, y) as unknowns.
(X−x1) ² + (y−y1) ² = (d1 + s) ² (Equation 1)
(X−x2) ² + (y−y2) ² = (d2 + s) ² (Expression 2)
(X−x3) ² + (y−y3) ² = (d3 + s) ² (Equation 3)
Here, the coordinates of the base station 30A are (x1, y1), the coordinates of the base station 30B are (x2, y2), and the coordinates of the base station 30C are (x3, y3). By positioning the base station 30A, the base station 30B, and the base station 30C at positions where the positions are known in advance, these coordinates can be set to known constants. Further, the distance between the mobile station 20 and the base station 30A is represented as d1, the distance between the mobile station 20 and the base station 30B is represented as d2, and the distance between the mobile station 20 and the base station 30C is represented as d3. These distances can also be known constants. Let s be the clock error between the mobile station 20 and the base station 30. In the positioning system, the position of the mobile station 20 can be calculated from the difference between the base stations 30 of the synchronization time of the signal transmitted from the mobile station 20 between the base stations. Specifically, the following mathematical formula is obtained from (Equation 1), (Equation 2), and (Equation 3).
[(X−x1) ² + (y−y1) ² ] ^(1/2) − [(x−x2) ² + (y−y2) ² ] ^(1/2) = (d1 + s) − (d2 + s) ( (Equation 4)
[(X−x1) ² + (y−y1) ² ] ^(1/2) − [(x−x3) ² + (y−y3) ² ] ^(1/2) = (d1 + s) − (d3 + s) ( (Equation 5)

Further, assuming that the synchronization times of the base stations 30A, 30B and 30C are T2a30A, T2a30B and T2a30C and the speed of light is c, the following relationship is established.
(D1 + s) − (d2 + s) = (T2a30A−T2a30B) × c (Equation 6)
(D1 + s) − (d3 + s) = (T2a30A−T2a30C) × c (Equation 7)
From (Expression 6) and (Expression 7), (Expression 4) and (Expression 5) are as follows.
[(X−x1) ² + (y−y1) ² ] ^(1/2) − [(x−x2) ² + (y−y2) ² ] ^(1/2) = (T2a30A−T2a30B) × c ( (Equation 8)
[(X−x1) ² + (y−y1) ² ] ^(1/2) − [(x−x3) ² + (y−y3) ² ] ^(1/2) = (T2a30A−T2a30C) × c ( (Equation 9)
The unknowns x and y can be calculated by (Equation 8) and (Equation 9).

<Flow of synchronization time detection processing by positioning system>
Hereinafter, as a specific example, the code period T _S of the PN code transmitted from the mobile station 20 1 m sec, the flow of the synchronization time detection processing in case of setting the interval P of the PN code generation end timing to 1 second, FIG. 14 will be described.

(Transmission process of PN code for first synchronization detection process)
First, the PN code transmitted from the mobile station 20, reference numeral period T _S is 1m sec, since the interval P of the PN code generation end timing is set to 1 second, generation start time of the PN signal is the mobile station time Is 02 minutes 02.999 seconds, and the generation end time is 02 minutes 03.000 seconds as the mobile station time, the next PN code generation start time is 02 minutes 03.999 seconds, and the PN signal generation end time is 02 minutes. 04.000 seconds. In this way, the mobile station 20 transmits a PN code that is a spreading code at a constant period.

(First synchronization detection process)
Then, the received signal demodulated by the base station 30 and demodulated by the transceiver circuit 32 is sampled by the quantizer 120 at a first sampling frequency cl ₁₀₂ of 10 MHz, for example, and the first signal is quantized. As a result of the synchronization detection processing, when the peak value of the autocorrelation value of the autocorrelation function is measured at 02 minutes 03.000003421 seconds, the synchronization time t _1a can be measured as 02 minutes 03.000003421 seconds.

(Second synchronization detection processing sampling time calculation processing)
Then, according to the flowchart of FIG. 12, a sampling start time t _2SS and a sampling end time t _2Sf that define a synchronization detection range for the second synchronization detection process are calculated. In the present embodiment, the second synchronous front preliminary time _{T 2SSp} is 0.1m sec, the second synchronous rear preliminary time _{T 2Sfp} is a 0.1m sec. As a result, the sampling start time t _2SS can be calculated as 02 minutes 03.99983421 seconds, the sampling end time t _2Sf can be calculated as 02 minutes 04.0000103421 seconds, and the sampling period can be calculated as 1.2 milliseconds.

(Second synchronization detection process)
Then, after the base station 30 receives the signal transmitted from the mobile station 20 after one period, the quantizer 150 converts the received signal demodulated by the transceiver circuit 32 with the second sampling frequency cl ₁₀₄ of 511.5 MHz, for example. The signal sampled and quantized by the above is stored in a memory or register 152. Therefore, 613.8 * 10 ^ 3 bits (= (1.2 * 10 ^ (− 3)) * 511.5 * 10 ^ 6) is stored in the memory or register 152.

  The autocorrelation value of the autocorrelation function between the signal quantized by the quantizer 150 and stored in the memory or register 152 and the PN code (replica) quantized by the quantizer 114 is calculated using the matched filter 154. Then, the second synchronization detection process is performed. As a result, the synchronization time can be measured based on the synchronization detection result of the second synchronization detection process.

Here, from the code period T _S (= 1 msec) of the PN code, the PN code quantized at 511.5 MHz by the quantizer 114 is 511.5 * 10 ^ 3 bits (= (1.0 * 10 ^). (-3)) * 511.5 * 10 ^ 6). As a result of calculating the autocorrelation value of the autocorrelation function by shifting the sampling start time _t2SS and the quantized PN code by 1 bit, and measuring the number of bits for detecting the peak of the autocorrelation value, 562606 (= 51106 + 511) 5 * 10 ^ 3) The peak of the autocorrelation value was calculated in bits.

(Synchronization time calculation process)
Since 562606 bits correspond to 1.099914 * 10 ^ (-3) seconds (= 562606 / (511.5 * 10 ^ 6)), the synchronization time is 02 minutes 04.000003335 seconds (02 minutes 03.999033421 seconds + 1). 099914 * 10 ^ (− 3) seconds).

(Positioning process)
As a result, the synchronization time difference between the base stations is calculated from the synchronization time of each base station, and positioning of the mobile station can be performed.

<< Modification >>
In the above-described embodiment, the clock generator 100 that generates a clock signal that is a reference for the synchronization detection process performed in the synchronization time detection unit 34 transmits the generated clock signal to the clock generators 102, 104, and 106. Therefore, the first sampling clock signal having the first sampling frequency used for the first synchronization detection process generated by the clock generator 102 and the second synchronization detection process generated by the clock generator 104 are used. Since the second sampling clock signal having the sampling frequency is generated based on the common clock signal, no synchronization shift occurs in the first synchronization detection process and the second synchronization detection process.

  However, it is also possible to generate sampling clock signals for the first and second synchronization detection processes based on clock signals generated by independent clock generators (not shown). A modification of the above embodiment is shown in FIG. In addition, the same code | symbol is attached | subjected about the same component as the structural example of FIG.

<< PN code >>
The mobile station 20 generates a PN code by the spread code generator 26 and transmits it to the transceiver circuit 28. The PN code transmitted by the mobile station 30 includes a plurality of different continuous PN codes, and the base station 30 includes a matched filter corresponding to the plurality of PN codes. Since the base station receives a plurality of continuous PN codes, even if a bit error occurs in one PN code of a plurality of PN codes, any of the plurality of PN codes does not generate an error bit. There is a high possibility of being a PN code. Therefore, when the radio wave condition is bad, the base station 30 can correctly receive the signal of the mobile station 20 even when there is a malfunction (burst error) in which a plurality of bit errors occur continuously in the received signal. FIG. 16 shows a code composed of a plurality of continuous PN codes. The code in FIG. 16 includes four PN codes having the same code length, specifically, a PN code A, a PN code B, a PN code C, and a PN code D. These four PN codes are continuously transmitted from the mobile station 20.

  As described above, according to the positioning system of the present embodiment, the sample time calculation unit 130 that performs the first synchronization detection process and determines the synchronization detection range for the second synchronization detection process based on the synchronization detection result information. And a synchronization time calculation unit 160 that samples the signal received from the mobile station 20 in the synchronization detection range after the first synchronization detection processing and detects synchronization with the spread code (replica) as the second synchronization detection processing; Therefore, in order to perform precise positioning of the mobile station 20, only the synchronization detection range determined for the second synchronization detection process based on the synchronization detection result information of the first synchronization detection process is sampled. It becomes possible. Therefore, the sampling period can be limited to a desired period.

  As a result, only the sampling for the second detection is sampled at a high sampling frequency, and the second synchronization detection process is more accurately performed based on the synchronization detection result information of the first synchronization detection process. Since accurate synchronization detection result information can be obtained, the positioning server 40 can perform precise positioning. In particular, since only the synchronization detection range for the second synchronization detection process is sampled and quantized at a high sampling frequency with respect to the received signal, it is not always necessary to perform sampling at a high sampling frequency. The synchronization time detection in the station 20 can be performed with low power consumption, and a positioning system capable of positioning with low power consumption can be realized.

  Furthermore, the positioning system according to the present invention is not limited to the above-described embodiment, and includes various other embodiments.

1 is a schematic configuration diagram of a positioning system in which a synchronous time detection system according to the present invention is used. It is a schematic block diagram of the mobile station 20 of the synchronous time detection system which concerns on this invention. It is an example of the circuit of the spreading code generator 26 of this embodiment. The code period T _S of the PN code 1m sec, in the case of setting the PN code generation interval P per second, which is a specific example showing the spreading code generation end time spreading code generation start time. 4 is a flowchart for explaining processing in which a controller 24 transmits a clock signal to a spread code generator 26 from a spread code generation start time to a spread code generation end time. 7 is a flowchart for explaining a setting process of a spread code generation start time and a spread code generation end time, which is executed in the controller 24. 2 is a schematic configuration diagram of a base station 30 that performs synchronization time detection for a mobile station 20. FIG. 3 is a configuration diagram of a synchronization time detection unit 34. FIG. 3 is a configuration diagram of a matched filter 122. FIG. 4 is a configuration diagram of a matched filter 154. FIG. It is a flowchart for demonstrating the positioning process of the positioning system which concerns on this embodiment. 7 is a flowchart for calculating a sampling start time and a sampling end time in the sample time calculation unit 130. It is a figure for demonstrating the synchronous time calculation method in a 2nd synchronous detection process. It is a figure for demonstrating the flow of a synchronous time detection process. It is a block diagram of the synchronous time detection part 34 which is a modification. It is a code composed of a plurality of continuous PN codes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Positioning system 20 Mobile station 22 Clock 24 Controller 26 Spreading code generator 20 Transceiver circuit 30, 30A, 30B, 30C, 30D Base station 32 Transceiver circuit 34 Synchronization time detection part 40 Positioning server 100 Clock generator 102, 104, 106 Clock generator 108 Clock 110 Spreading code generator 112, 114 Quantizer 120 Quantizer 122 Matched filter 130 Sample time calculator 140 Sampling control signal generator 150 Quantizer 152 Memory 154 Matched filter 160 Synchronous time calculator

Claims (5)

A positioning system including a base station that receives a signal transmitted from a mobile station, and a positioning calculation unit connected to the base station through a network,
The mobile station
Signal transmission means for transmitting the spread code generated by the mobile station itself as the signal at a predetermined period;
The base station
Sampling means for receiving a signal from the mobile station and sampling the signal;
First detection means for detecting spreading code synchronization as a first detection from the first sampling result sampled by the sampling means;
Determining means for determining a synchronization detection range for the second detection based on the synchronization detection result information of the first detection means;
Second detection means for detecting synchronization of a spread code as the second detection from a second sampling result obtained by sampling a signal received from the mobile station in the synchronization detection range after the first detection;
The positioning calculation unit
Positioning calculation means for performing positioning based on synchronization detection result information obtained by the second detection means by at least three of the base stations,
The positioning system, wherein a sampling frequency for the second detection is higher than a sampling frequency for the first detection. The determination means adds a time to at least one of a sampling start time and a sampling end time obtained based on the synchronization detection result information, and sets a synchronization detection range as a new sampling start time and sampling end time. decide,
The positioning system according to claim 1. The additional time is determined based on a clock pitch error and a sampling frequency of the first detection means and the second detection means.
The positioning system according to claim 2, wherein: Wireless communication between the mobile station and the base station by direct spread spectrum spread communication method or ultra-wideband wireless communication method,
The positioning system according to one of claims 1 to 3, wherein The mobile station transmits a plurality of different consecutive PN codes as the spreading code,
The first detection unit and the second detection unit each include a matched filter corresponding to each of the PN codes.
The positioning system according to claim 1, wherein:

Images