JP2020134146A - Range-finding device and range-finding system - Google Patents

Abstract

To provide a range-finding device and range-finding system that can more accurately estimate a distance to a transmission station.SOLUTION: A range-finding device is provided that comprises: a first lead timing estimation unit that estimates a first lead timing of a reception signal acquired from a transmission station; a time window function part that hews out the reception signal with a prescribed time window on the basis of the first lead timing; a second lead timing estimation unit that estimates a second lead timing of the reception signal on the basis of a hewed-out reception signal; a third lead timing estimation unit that estimates a third lead timing of the reception signal on the basis of a waveform obtained by improving resolution power of a waveform of a second correlation function with the second lead timing as a center; and a range-finding unit that estimates a distance to the transmission station.SELECTED DRAWING: Figure 3

Description

The present invention relates to a distance measuring device and a distance measuring system.

In recent years, a technique for estimating the distance to a wireless terminal (transmitting station), which is a source of a packet, has been developed based on information about a packet received by a base station. As such a technique, for example, a method of estimating the distance to the wireless terminal based on the reception time of the packet between the base station and the wireless terminal can be mentioned.

Japanese Unexamined Patent Publication No. 2006-352314 JP-A-2010-147575

In recent years, there has been a demand for more accurate estimation of the distance to a wireless terminal (transmitting station). Therefore, the present invention has been made in view of such a situation, and an object of the present invention is a new and improved measurement capable of estimating the distance to the transmitting station more accurately. The purpose is to provide a distance device and a distance measurement system.

In order to solve the above problems, according to a certain viewpoint of the present invention, a first of the received signals is based on a first correlation function which is a cross-correlation function of a received signal acquired from a transmitting station and a known signal. Based on the first head timing estimation unit that estimates the head timing and the first head timing, the received signal is multiplied by a time window function to cut out the received signal having a predetermined time window. Second head timing estimation that estimates the second head timing of the received signal based on the time window function unit and the second correlation function that is a cross-correlation function between the received signal and the known signal that has been cut out. A third, which estimates the third head timing of the received signal based on the waveform obtained by improving the resolution of the waveform of the second correlation function centering on the unit and the second head timing. A head timing estimation unit, a distance measuring unit that estimates the distance to the transmitting station based on the transmission timing obtained from the received signal and the reception timing of the received signal estimated from the third head timing. A ranging device comprising, is provided.

The time window function unit may cut out the received signal including the preamble unit from the received signal.

The distance measuring device may further include a decoding unit that acquires the transmission timing by decoding the received signal.

The first start timing is based on a third correlation function which is a cross-correlation function between the received signal, a signal portion reproduced based on the third start timing, and an extended known signal including a preamble portion. , The fourth head timing of the received signal may be estimated.

The extended known signal may further include a payload section.

The third head timing estimation unit extracts a plurality of sample points from the second correlation function at predetermined intervals around the second head timing, and interpolates the extracted plurality of sample points. By performing the process, the resolution of the waveform of the second correlation function may be improved.

The third head timing estimation unit extracts a plurality of sample points from the second correlation function at predetermined intervals around the second head timing, and approximates the extracted plurality of sample points. By performing the process, the resolution of the waveform of the second correlation function may be improved.

Further, in order to solve the above problems, according to another aspect of the present invention, the distance measuring system includes a plurality of distance measuring devices, and the distance measuring device is a received signal and a known signal acquired from a transmitting station. The first start timing estimation unit that estimates the first start timing of the received signal based on the first correlation function that is a mutual correlation function with the above, and the received signal based on the first start timing. A second correlation, which is a mutual correlation function between the cut-out received signal and the known signal, and the time window function unit that cuts out the received signal having a predetermined time window by multiplying the time window function. Based on the function, the resolution of the waveform of the second correlation function is improved centering on the second head timing estimation unit that estimates the second head timing of the received signal and the second head timing. Based on the obtained waveform, it is estimated from the third head timing estimation unit that estimates the third head timing of the received signal, the transmission timing obtained from the received signal, and the third head timing. Provided is a distance measuring system including a distance measuring unit that estimates a distance to the transmitting station based on a reception timing of the received signal.

As described above, according to the present invention, it is possible to provide a distance measuring device and a distance measuring system capable of estimating the distance to the transmitting station with higher accuracy.

It is explanatory drawing which shows the outline of the wireless communication system 10 which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the configuration example of the packet which concerns on this embodiment. It is a block diagram which shows the structural example of the base station 200 which concerns on this embodiment. It is a flowchart which shows the operation example of the base station 200 which concerns on this embodiment. It is explanatory drawing for demonstrating the processing example of the time window function which concerns on this embodiment. It is explanatory drawing for demonstrating the processing example which improves the resolution of the 2nd correlation function waveform which concerns on this embodiment. It is a flowchart which shows the operation example of the base station 200 which concerns on 2nd Embodiment of this invention. It is a block diagram which showed the hardware configuration example of the base station 200 which concerns on embodiment of this invention.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

Further, in the present specification and the drawings, a plurality of components having substantially the same or similar functional configurations may be distinguished by adding different alphabets after the same reference numerals. However, if it is not necessary to distinguish each of the plurality of components having substantially the same or similar functional configurations, only the same reference numerals are given.

Further, in the following description, unless otherwise specified, "connection" means electrically connecting a plurality of elements so as to be able to carry a signal (high frequency analog signal or digital signal). Means. Further, the "connection" in the following description includes not only the case where a plurality of elements are directly connected but also the case where a plurality of elements are indirectly connected via other elements.

<< First Embodiment >>
<Overview of wireless communication system 10>
A first embodiment of the present invention relates to a wireless communication system (distance measuring system) 10 that estimates the position of a wireless terminal 100 (transmitting station) using a plurality of base stations (distance measuring devices) 200. Hereinafter, the outline of the wireless communication system 10 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is an explanatory diagram showing an outline of the wireless communication system 10 according to the present embodiment, and FIG. 2 is an explanatory diagram showing a configuration example of a packet according to the present embodiment.

As shown in FIG. 1, the wireless communication system 10 of the present embodiment is, for example, a wireless LAN (Local Area Network) system (for example, a wireless LAN system compliant with IEEE802.11), and a plurality of base stations 200a to 200d. And the wireless terminal 100. Further, in the present embodiment, it is assumed that each base station 200 is a fixed station whose position is fixed, and the wireless terminal 100 is a mobile station that can move. Although only one wireless terminal 100 is shown in FIG. 1, a plurality of wireless terminals 100 may be included in the present embodiment. Further, the wireless communication system 10 may include a server (not shown) that aggregates information acquired by the following base station 200 (for example, information on the distance from each base station 200 to the wireless terminal 100).

Further, in the present embodiment, the communication method of the wireless communication system 10 is not particularly limited, and for example, an interface (base station or terminal) for short-range wireless communication such as Bluetooth (registered trademark) or ZigBee (registered trademark). ), Wi-Fi (registered trademark), communication interface (base station or terminal) such as mobile communication network (LTE, 3G), car navigation system, ETC (Electronic Doll Collection) system, and the like.

In the wireless communication system 10, the position of the wireless terminal 100 is estimated based on the packet transmission / reception time at the base station 200, that is, the position of the wireless terminal 100 is estimated based on the TOA (Time of Arrival) method. In the present embodiment, for example, in the wireless communication system 10, a plurality of base stations 200 whose time synchronization is established may send and receive packets broadcast to the wireless terminal 100, for example. Then, each base station 200 has a time when the wireless terminal 100 transmits a packet to each base station 200 (hereinafter, also referred to as a transmission time) and a time when each base station 200 receives the packet (hereinafter, reception time). The distance to the wireless terminal 100 is estimated based on (also referred to as time). At that time, in the present embodiment, the start timing of the received signal used for the distance estimation, that is, the calculation of the reception time at which the received signal is received is performed as described below to estimate the distance to the wireless terminal 100. The accuracy of can be further improved.

The outline of each device included in the wireless communication system 10 according to the present embodiment will be sequentially described below.

(Wireless terminal 100)
The wireless terminal 100 is a wireless terminal that performs wireless communication with the base station 200. For example, the wireless terminal 100 sends and receives packets to and from the base station 200. Further, in the present embodiment, the wireless terminal 100 is a target of distance estimation. Specifically, for example, the wireless terminal 100 can send and receive packets that can be used for distance estimation to and from the base station 200.

Here, a configuration example of the packet according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the packet transmitted / received between the base station 200 and the wireless terminal 100 is composed of a preamble unit 50, a signal unit 52, and a payload unit 54. The preamble unit 50 is a symbol sequence used to detect the symbol timing of the packet, and is known between the wireless terminal 100 and the base station 200. The time length of the preamble portion 50 is known, for example, 16 μs. Therefore, since the preamble unit 50 is a known signal between the wireless terminal 100 and the base station 200, the signal received by the base station 200 and the known signal acquired and stored in advance by the base station 200 are cross-correlated. By performing the processing, it is possible to calculate the start timing of the received signal.

The signal unit 52 is a symbol that includes control information such as information such as the transmission speed, packet length, and modulation method of the payload unit 54. The time length of the signal unit 52 is a single symbol length, for example, 4 μs. The payload unit 54 is a symbol series including information such as application data and transmission time, which are information generated by the application of the wireless terminal 100, and is composed of a plurality of symbols. Further, the time length per one of the plurality of symbols constituting the payload unit 54 is, for example, 4 μs, and the total time length of the payload unit 54 is the total of the time lengths of the plurality of symbols. The time length of the payload unit 54 is longer than that of the preamble unit 50.

(Base station 200)
The base station 200 is a wireless communication device that performs wireless communication with the wireless terminal 100. For example, the base station 200 is connected to the wireless terminal 100 by an arbitrary communication method and performs wireless communication. In the present embodiment, as described above, the communication method of the base station 200 is not particularly limited. Further, the base station 200 can calculate the start timing of the packet based on the information when the packet is transmitted / received to / from the wireless terminal 100. Further, the base station 200 can estimate the distance from the base station 200 to the wireless terminal 100 based on the calculated start timing, that is, the reception time and the transmission time. Details of the configuration of the base station 200 will be described later.

<Configuration example of base station 200>
The outline of the wireless communication system 10 according to the present embodiment has been described above with reference to FIGS. 1 and 2. Subsequently, a configuration example of the base station 200 according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration example of the base station 200 according to the embodiment. As shown in FIG. 3, the base station 200 according to the present embodiment mainly has two blocks, a communication unit 230 and a processing unit 240. The details of the two blocks included in the base station 200 will be described below.

(Communication unit 230)
The communication unit 230 has a function of transmitting and receiving packets. For example, the communication unit 230 transmits / receives packets to / from the wireless terminal 100. Specifically, as shown in FIG. 3, the communication unit 230 mainly includes an antenna 201, a demodulator 202, and an ADC (Analog to Digital Converter) 203. The details of each functional unit including the communication unit 230 will be described below.

~ Antenna 2001 ~
The antenna 201 has a single antenna element or a plurality of antenna elements, and has a function of transmitting and receiving a radio signal to and from an antenna of another communication device. For example, the antenna 201 receives a high-frequency radio signal transmitted from the antenna of the wireless terminal 100. Then, the antenna 201 outputs the received radio signal as a reception signal to the demodulator 202.

~ Demodulator 202 ~
The demodulator 202 has a function of demodulating the received signal. For example, the demodulator 202 is connected to the antenna 201 and converts the received signal input from the antenna 201 into an analog baseband received signal. Then, the demodulator 202 outputs the analog baseband reception signal to the ADC 203.

~ ADC203 ~
The ADC 203 is an analog-digital conversion circuit (A / D conversion circuit), and has a function of converting an analog signal into a digital signal, that is, a function of sampling an analog signal. For example, the ADC 203 is connected to a demodulator 202 and converts an analog baseband reception signal received from the demodulator 202 into a digital baseband reception signal, and the ADC 203 processes the digital baseband reception signal. Output to unit 240.

(Processing unit 240)
The processing unit 240 is a functional unit that performs processing related to the radio signal received by the communication unit 230 described above. For example, the processing unit 240 can estimate the start timing of the received signal received from the wireless terminal 100 and determine the reception time. Further, the processing unit 240 can estimate the distance to the wireless terminal 100 based on the determined reception time. In order to realize the above-mentioned functions, the processing unit 240 according to the present embodiment includes, for example, an FPGA (Field Programmable Gate Array) (not shown) and a storage device (not shown). The details of the processing unit 240 will be sequentially described below.

Specifically, the FPGA has a function of performing digital signal processing, estimates the start timing of the received signal described above, and estimates the distance to the wireless terminal 100. Here, the FPGA is an integrated circuit whose configuration can be rewritten by the user after manufacturing. More specifically, as shown in FIG. 3, the FPGA includes a first head timing detection unit (first head timing estimation unit) 204, a time window function unit 205, and a second head timing detection unit (1st head timing estimation unit). It mainly has a second head timing estimation unit) 206, a third head timing detection unit (third head timing estimation unit) 207, a distance measurement calculation unit (distance measurement unit) 208, and a decoding unit 210. .. The details of these functional units will be described in order below.

~ First start timing detection unit 204 ~
The first head timing detection unit 204 acquires the baseband reception signal acquired from the communication unit 230, and based on the first correlation function which is a cross-correlation function between the baseband reception signal and the known signal, the first The start timing of 1 is detected (estimated). Specifically, the first head timing detection unit 204 performs cross-correlation processing in the time domain using a known preamble signal stored in a storage device described later on the packet of the baseband reception signal, and first. Calculate the cross-correlation waveform of. More specifically, the first head timing detection unit 204 superimposes a known preamble signal on the baseband reception signal while shifting by a predetermined time, and the baseband reception signal and the known preamble signal at that time Calculate the degree of matching of. As described above, since the packet of the baseband received signal includes the preamble portion 50 at the head portion, there is a time domain that matches the known preamble signal. Then, the first head timing detection unit 204 can calculate the first cross-correlation waveform by calculating the relationship of the degree of coincidence between the baseband received signal and the known preamble signal with respect to the shifted time. it can. Then, the first head timing detection unit 204 is based on the first correlation peak position, which is the maximum value (that is, the most matched portion) of the calculated first cross-correlation waveform, at the time when the most coincidence occurs. A certain first start timing is detected. Further, the first head timing detection unit 204 outputs the detected first head timing to the time window function unit 205, which will be described later.

~ Time window function part 205
The time window function unit 205 multiplies the baseband received signal acquired from the communication unit 230 by the time window function based on the first head timing detected by the first head timing detection unit 204. A signal having a predetermined time window can be cut out. Specifically, the time window function unit 205 is a range of received signals from the baseband received signal having a time window corresponding to the signal length of the known preamble signal, starting from the first start timing, that is, the preamble unit. The received signal including 50 can be cut out. By doing so, in the present embodiment, it is possible to attenuate the amplitude component of the unnecessary signal waveform such as noise before the beginning of the baseband received signal, that is, before the preamble portion 50. Further, in the present embodiment, the amplitude component of the signal waveform of the signal unit 52 located behind the preamble unit 50 of the baseband received signal can be attenuated. In other words, in the present embodiment, the time window function unit 205 attenuates the signal components other than the preamble unit 50 in the baseband received signal. Therefore, according to the present embodiment, the influence of noise and the like can be suppressed by multiplying the time window function and cutting out the preamble portion 50 as described above. Therefore, the detection of the head timing in the subsequent processing The accuracy of can be improved.

Then, the time window function unit 205 uses the second head timing detection unit 206 and the third head timing, which will be described later, for the baseband reception signal (reception signal to which the time window has been applied) cut out by multiplying the time window function. Output to the detection unit 207. In the present embodiment, the time window function unit 205 is not limited to cutting out the preamble unit 50, and the signal unit 52, the payload unit 54, etc. may be cut out together with the preamble unit 50. It is preferable to appropriately select the time length of the time window to be cut out according to the range to be cut out. The details of the processing by the time window function unit 205 will be described later.

~ Second head timing detector 206 ~
The second head timing detection unit 206 is based on the second correlation function which is a cross-correlation function between the base band reception signal (reception signal to which the time window has been applied) and the known signal cut out by the time window function unit 205. , Detects (estimates) the second head timing. Specifically, the second head timing detection unit 206, like the first head timing detection unit 204, cross-correlates the received signal to which the time window has been applied in the time domain using a known preamble signal. The process is performed to calculate the second cross-correlation waveform. In the present embodiment, since the received signal to which the time window has been applied is a received signal cut out so as to include the preamble unit 50, there is a time domain that matches the known preamble signal. Then, the second head timing detection unit 206 is based on the second correlation peak position, which is the maximum value (that is, the most matched portion) of the calculated second cross-correlation waveform, at the time when the most coincidence occurs. A certain second start timing is detected. At this time, the received signal to which the time window has been applied, which is the target of the cross-correlation processing, mainly includes the preamble section 50, and the signal components other than the preamble section 50 are attenuated. It is possible to accurately detect the second head timing while suppressing the increase in processing time. Further, the second head timing detection unit 206 outputs the detected second head timing to the third head timing detection unit 207, which will be described later.

~ Third head timing detection unit 207 ~
The third head timing detection unit 207 is based on the cut out baseband reception signal (received signal to which the time window has been applied) and the second head timing from the second head timing detection unit 206. The resolution of the correlation function waveform of is improved, and the third head timing is detected (estimated). For example, the third head timing detection unit 207 extracts a plurality of sample points from the second correlation function waveform at predetermined intervals centering on the second head timing detected by the second head timing detection unit 206. , The resolution of the second correlation function waveform can be improved by performing interpolation processing (for example, acquiring a waveform passing through each sample point) on the extracted plurality of sample points. Alternatively, the third head timing detection unit 207 extracts a plurality of sample points from the second correlation function waveform at predetermined intervals centering on the second head timing detected by the second head timing detection unit 206. , The resolution of the second correlation function waveform can be improved by performing approximation processing (for example, acquiring a waveform that approximates each sample point) on the extracted plurality of sample points. In the present embodiment, the method for improving the resolution of the second correlation function waveform is not limited to the above-mentioned methods such as interpolation processing and approximation processing.

Further, the third head timing detection unit 207 detects the third correlation peak position, that is, the more consistent time domain from the maximum value of the waveform obtained by improving the resolution of the second correlation function waveform. , The third head timing is detected based on the detected third correlation peak position. The third head timing detection unit 207 outputs the detected third head timing to the distance measurement calculation unit 208, which will be described later. In the present embodiment, since the resolution of the correlation function waveform is improved in this way, the third peak position can be detected more accurately, and as a result, the third head timing can be detected more accurately. .. The details of the processing by the third head timing detection unit 207 will be described later.

~ Distance measurement calculation unit 208 ~
The distance measurement calculation unit 208 uses the transmission time (transmission timing) obtained by performing the known decoding process of the payload unit 54 of the baseband reception signal by the decoding unit 210 described later, and the third head timing detection unit 207. The distance to the wireless terminal 100 can be estimated based on the reception time (reception timing) estimated from the detected third head timing. More specifically, the distance measurement calculation unit 208 can estimate the distance to the wireless terminal 100 from the difference time between the transmission time and the reception time.

~ Decoding unit 210
The decoding unit 210 specifies the range of the payload unit 54 of the baseband received signal based on the third head timing, and performs a known decoding process on the specified payload unit 54, thereby being included in the payload unit 54. Information on the transmitted transmission time (transmission timing) can be acquired. Then, the decoding unit 210 outputs the acquired transmission time information to the distance measurement calculation unit 208 described above. Further, the decoding unit 210 may specify the signal unit 52 of the baseband reception signal and decode the signal unit 52 based on the third head timing, and may perform decoding of the signal unit 52, and the signal unit 52 and the payload of the baseband reception signal. The unit 54 may be specified, and the signal unit 52 and the payload unit 54 may be decoded.

~Storage device~
Further, the processing unit 240 has a storage device (not shown) as described above. The storage device is a device for storing information used in processing in the base station 200. For example, the storage device stores data such as a waveform of a known signal (preamble signal).

<Operation example>
The configuration example of the base station 200 according to the present embodiment has been described above with reference to FIG. Subsequently, an operation example of the wireless communication system 10 according to the present embodiment will be described with reference to FIGS. 4 to 6. FIG. 4 is a flowchart showing an operation example of the base station 200 according to the present embodiment. Further, FIG. 5 is an explanatory diagram for explaining a processing example of the time window function according to the present embodiment, and FIG. 6 is a processing example for improving the resolution of the second correlation function waveform according to the present embodiment. It is explanatory drawing for demonstrating.

As shown in FIG. 4, the operation example of the wireless communication system 10 according to the present embodiment includes, for example, a plurality of steps from step S101 to step S119. The details of each step shown in FIG. 4 will be described below.

(Step S101)
The communication unit 230 of the base station 200 acquires a packet from the wireless terminal 100, converts the analog baseband reception signal into a digital baseband reception signal, and outputs the packet to the processing unit 240 of the base station 200.

(Step S103)
The first head timing detection unit 204 of the processing unit 240 of the base station 200 performs cross-correlation processing in the time domain using a known preamble signal on the packet of the baseband reception signal acquired from the communication unit 230. The first cross-correlation waveform is calculated.

(Step S105)
Next, the first head timing detection unit 204 detects the first head timing by detecting the first correlation peak position from the calculated maximum value of the first cross-correlation waveform.

(Step S107)
The time window function unit 205 of the processing unit 240 multiplies the time window function on the baseband received signal acquired from the communication unit 230 based on the first head timing detected by the first head timing detection unit 204. By stacking, a received signal having a time window of the signal length of the known preamble signal (received signal to which the time window is applied) is cut out.

FIG. 5 shows an example of a time window function that is multiplied with respect to the baseband received signal. As shown in the lower part of FIG. 5, the time window function has a flat amplitude response characteristic with respect to the known time length L of the preamble portion 50, and has an amplitude response characteristic that attenuates the outside of the time length L. Is a function with. FIG. 5 shows a case where the first head timing is ideally detected in step S105 described above. In such a case, since the first start timing and the start of the preamble portion 50 included in the baseband received signal are in a state of substantially matching, when the time window function is applied, other than the preamble portion 50 The signal component of is suitably attenuated, and the preamble portion 50 can be appropriately cut out. In the present embodiment, by doing so, it is possible to attenuate the amplitude component of the unnecessary signal waveform such as noise before the beginning of the baseband received signal, that is, before the preamble portion 50. Further, according to the present embodiment, it is possible to attenuate the amplitude component of the signal waveform of the signal unit 52 and the like located behind the preamble unit 50 of the baseband received signal.

In the present embodiment, in order to further improve the accuracy of detecting the head timing, the cut-out received signal includes the preamble portion 50, and the signal components other than the preamble portion 50 are further attenuated. Is preferable. Therefore, in the present embodiment, it is preferable that the time length L of the predetermined time window to be cut out is equivalent to the time length of the preamble signal. However, since the first head timing, which is the starting point when applying the time window, does not always exactly coincide with the head of the preamble portion 50, it is cut out so as to include the entire preamble portion 50. The time length L of the predetermined time window is preferably set to be slightly longer than the time length of the preamble signal.

(Step S109)
The second head timing detection unit 206 of the processing unit 240 performs cross-correlation processing of the time domain using the known preamble signal on the received signal to which the time window has been applied cut out by the time window function unit 205. The second cross-correlation waveform is calculated.

(Step S111)
Next, the second head timing detection unit 206 detects the second head timing by detecting the second correlation peak position from the calculated maximum value of the second cross-correlation waveform.

(Step S113)
The third head timing detection unit 207 extracts and extracts a plurality of sample points from the second correlation function waveform at predetermined intervals centering on the second head timing detected by the second head timing detection unit 206. Interpolation processing (for example, acquiring a waveform passing through each sample point) is performed on a plurality of sample points.

For example, as shown in FIG. 6, the third head timing detection unit 207 is, for example, from the second cross-correlation waveform, M samples (three in FIG. 6) before and after the second head timing. The points are extracted, and an interpolation process such as Lagrange interpolation is applied to these 2M + 1 (7 in FIG. 6) sample points. By performing such an interpolation process, a cross-correlation waveform as shown in FIG. 6 can be obtained. In the present embodiment, since the resolution of the correlation function waveform is improved in this way, the third head timing can be detected with high accuracy in the subsequent step S115.

(Step S115)
Further, the third head timing detection unit 207 detects the third correlation peak position at a position (that is, between the sample points) that is a non-integer multiple of the sampling interval by the interpolation process in step S113. , Detects the third start timing.

(Step S117)
The decoding unit 210 of the processing unit 240 acquires information on the transmission time (transmission timing) by performing known decoding processing on the payload unit 54 of the baseband reception signal.

(Step S119)
The distance measurement calculation unit 208 has a difference time between the transmission time (transmission timing) obtained in step S117 described above and the reception time (reception timing) estimated from the third head timing obtained in step S115 described above. Estimates the distance from to the wireless terminal 100.

In the present embodiment, information on the distance to the wireless terminal 100 estimated by a plurality of (for example, three or more) base stations 200 whose positions are known is aggregated in a server (not shown) and aggregated. The position of the wireless terminal 100 may be estimated based on the information.

<Summary>
As described above, according to the present embodiment, the distance to the wireless terminal 100 can be estimated more accurately. Specifically, in the present embodiment, the preamble portion 50 of the baseband reception signal can be cut out by multiplying the baseband reception signal by a time window function. In the present embodiment, by doing so, the amplitude component of the unnecessary signal waveform such as noise before the beginning of the baseband received signal, that is, before the preamble portion 50 is attenuated. Further, in the present embodiment, by doing so, the amplitude component of the signal waveform of the signal unit 52 located behind the preamble unit 50 of the baseband received signal is attenuated. Therefore, according to the present embodiment, the influence of noise and the like can be suppressed, so that the accuracy of detecting the head timing can be improved. Further, in the present embodiment, the accuracy of detecting the head timing can be further improved by improving the resolution of the correlation function waveform by using interpolation processing or the like. Then, in the present embodiment, since the accuracy of detecting the head timing is improved, the accuracy of estimating the reception time based on the head timing is improved, and the distance to the wireless terminal 100 can be estimated more accurately. ..

<Modification example>
In the present embodiment, when the base station 200 has a plurality of antennas 201, the above operations are performed for each of the received signals obtained by the plurality of antennas 201, and the plurality of estimated distance measurements obtained are obtained. The data may be averaged. Alternatively, the received signals obtained by the plurality of antennas 201 may be combined by multiplying the weighting coefficients having amplitudes and phases, respectively, and the above operation may be performed on the combined received signals.

<< Second Embodiment >>
In the first embodiment of the present invention described above, cross-correlation processing is performed on the preamble portion 50. However, the embodiment of the present invention is not limited to such a first embodiment. For example, the flow of the first embodiment described above is repeatedly carried out, and in the second flow, the signal unit is used. The cross-correlation processing may be performed by including the 52 and the payload unit 54, that is, by expanding the range. The second embodiment of the present invention will be described below.

In the present embodiment, the configuration of the wireless communication system (distance measuring system) 10 and the configuration of each device included in the wireless communication system 10 are the same as those of the first embodiment of the present invention described above. , The description is omitted here.

<Operation example>
Next, an operation example of the wireless communication system 10 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing an operation example of the base station 200 according to the present embodiment.

As shown in FIG. 7, the operation example of the wireless communication system 10 according to the present embodiment includes, for example, a plurality of steps from step S201 to step S221. The details of each step shown in FIG. 7 will be described below.

(Step S201)
Since step S201 is the same as step S101 of the first embodiment shown in FIG. 4, description thereof will be omitted here.

(Step S203)
The first head timing detection unit 204 performs cross-correlation processing in the time domain using a known preamble signal on the packet of the baseband reception signal acquired from the communication unit 230, and calculates the first cross-correlation waveform. To do.

In the second step S203, the first head timing detection unit 204 includes the signal unit 52 reproduced in step S217, which will be described later, behind the known preamble signal with respect to the baseband reception signal. The time domain cross-correlation processing using the known preamble signal is performed, and the third cross-correlation waveform (third correlation function) is calculated. In the present embodiment, by doing so, the accuracy of detecting the head timing can be further improved.

(Step S205)
Since the first step S205 is the same as the step S105 of the first embodiment shown in FIG. 4, the description thereof is omitted here.

In step S205 performed for the second time, the first head timing detection unit 204 detects the fourth correlation peak position from the maximum value of the third cross-correlation waveform calculated in step S203, thereby performing the fourth. Detects the start timing of.

(Step S207)
The time window function unit 205 of the processing unit 240 multiplies the baseband received signal by the time window function based on the first head timing detected in the first step S205 to obtain a known preamble signal. A received signal having a time window of signal length (received signal to which the time window has been applied) is cut out.

In step S207 to be performed a second time, the first head timing detection unit 204 multiplies the baseband reception signal by a time window function to display the signal unit 52 reproduced in step S217 described later. A received signal having a time window of the signal length of the extended preamble signal included behind the known preamble portion (received signal to which the time window has been applied) may be cut out. At this time, a time window having a longer time length than the signal length of the extended preamble signal may be used. By doing so, the accuracy of the second first timing detection can be further improved.

(Step S209 to Step S215)
Since steps S209 to S215 are the same as steps S109 to S115 of the first embodiment shown in FIG. 4, description thereof will be omitted here.

(Step S217)
The decoding unit 210 identifies the position of the signal unit 52 behind the preamble unit 50 based on the third head timing detected in step S215, decodes the signal unit 52 composed of a single symbol, and then decodes the signal unit 52. The waveform (reproduction / reception signal) of the signal unit 52 is reproduced based on the decoded bit sequence. Then, the decoding unit 210 outputs the regenerated waveform including the preamble unit 50 and the signal unit 52 to the first head timing detection unit 204, and proceeds to step S219. In the present embodiment, after step S219, the process returns to step S203, and the cross-correlation processing with the baseband received signal is performed again using the extended preamble unit (extended known signal) including the signal unit 52. The accuracy of detecting the head timing can be further improved.

In step S217, which is performed a second time, the decoding unit 210 acquires information on the transmission time (transmission timing) by performing a known decoding process on the payload unit 54 of the baseband reception signal.

(Step S219)
If the distance measurement calculation unit 208 has acquired the transmission time information in step S217, the process proceeds to step S221, while if the distance measurement calculation unit 208 has not acquired the transmission time information in step S217, the process proceeds to step S221. , Return to step S203.

<Summary>
As described above, according to the present embodiment, the distance from the base station 200 to the wireless terminal 100 can be estimated more accurately. More specifically, in the present embodiment, since the operation in the first embodiment is repeatedly performed, the accuracy of detecting the head timing can be further improved. As a result, also in the present embodiment, the accuracy of detecting the head timing is further improved, so that the accuracy of estimating the reception time based on the head timing is further improved, and the distance from the base station 200 to the wireless terminal 100 is further improved. It can be estimated accurately.

In the present embodiment, if the signal waveform of the payload unit 54 is known, in step S217, an extended preamble unit including the preamble unit 50, the signal unit 52, and the payload unit 54 is used, and step S203 is used. By performing the cross-correlation processing in a wider range, the accuracy of detecting the head timing can be further improved.

<< Hardware configuration >>
Next, the hardware configuration of the base station 200 according to the embodiment of the present invention will be described with reference to FIG. FIG. 8 is a block diagram showing an example of the hardware configuration of the base station 200 according to the embodiment of the present invention. The information processing by the base station 200 according to the embodiment of the present invention is realized by the cooperation between the software and the hardware described below.

The base station 200 includes a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 903, and a RAM (Random Access Memory) 905. Further, the base station 200 has a storage device 907 and a network interface 909.

The CPU 901 functions as an arithmetic processing device and a control device, and controls the overall operation in the base station 200 according to various programs. Further, the CPU 901 may be an FPGA or a microprocessor. The ROM 903 stores programs, calculation parameters, and the like used by the CPU 901. The RAM 905 temporarily stores a program used in the execution of the CPU 901, parameters that are appropriately changed in the execution, and the like. Then, these are connected to each other by a host bus composed of a CPU bus or the like. The CPU 901, ROM 903, and RAM 905 can realize, for example, the functions of the distance measuring calculation unit 208 and the like described with reference to FIG.

The storage device 907 is a device for storing data. The storage device 907 may include a storage medium, a recording device for recording data on the storage medium, a reading device for reading data from the storage medium, a deletion device for deleting the data recorded on the storage medium, and the like. The storage device 907 is composed of, for example, an HDD (Hard Disk Drive) or an SSD (Solid Stage Drive), or a memory having an equivalent function. The storage device 907 drives the storage and stores programs and various data executed by the CPU 901.

The network interface 909 is, for example, a communication interface composed of a communication device or the like for connecting to a network. Such communication interfaces include, for example, short-range wireless communication interfaces such as Bluetooth (registered trademark) or ZigBee (registered trademark), and communication such as wireless LAN, Wi-Fi (registered trademark), or mobile communication network (LTE, 3G). Can be an interface. Further, the network interface 909 may be a wired communication device that performs wired communication.

The hardware configuration example of the base station 200 has been described above with reference to FIG.

<< Supplement >>
Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.

In the above description, the distance from each base station 200 to the wireless terminal 100 has been estimated, but each embodiment of the present invention is not limited thereto. For example, in each embodiment of the present invention, the distance to each base station 200 can be estimated in the wireless terminal 100 by giving the wireless terminal 100 the same function as the processing unit 240 of the base station 200 described above. Good.

In addition, the above-described operation (processing) according to the embodiment of the present invention does not necessarily have to be performed or processed in the order described. For example, each step of the above operation may be processed by changing the order as appropriate. Further, each step may be partially processed in parallel or individually instead of being processed in chronological order. Further, the operation method or processing method of each step does not necessarily have to be operated or processed according to the described method, and may be operated or processed by another functional unit by another method, for example.

Further, at least a part of the operation (process) according to the above embodiment can be configured by software as an information processing program for operating a computer, and when configured by software, at least of these methods. A program that realizes a part of the program is stored in a recording medium such as a flexible disk or a CD-ROM (Compact Disk Read Only Memory), and is read and executed by the base station 200 or the like or another device connected to the base station 200. You may let me. The recording medium is not limited to a removable one such as a magnetic disk or an optical disk, and may be a fixed recording medium such as a hard disk device or a memory. Further, a program that realizes at least a part of these operations may be distributed via a communication line (including wireless communication) such as the Internet. Further, the program may be encrypted, modulated, compressed, and distributed via a wired line or wireless line such as the Internet, or stored in a recording medium.

10 Wireless communication system 50 Preamble part 52 Signal part 54 Payload part 100 Wireless terminal 200 Base station 201 Antenna 202 Demodulator 203 ADC
204 1st head timing detection unit 205 Time window function part 206 2nd head timing detection unit 207 3rd head timing detection unit 208 Distance measurement calculation unit 210 Decoding unit 230 Communication unit 240 Processing unit 901 CPU
903 ROM
905 RAM
907 Storage device 909 Network interface

Claims (8)

A first head timing estimation unit that estimates the first head timing of the received signal based on the first correlation function that is a cross-correlation function between the received signal and the known signal acquired from the transmitting station.
A time window function unit that multiplies the received signal by a time window function based on the first first timing and cuts out the received signal having a predetermined time window.
A second head timing estimation unit that estimates the second head timing of the received signal based on the second correlation function that is a cross-correlation function between the received signal and the known signal that has been cut out.
A third head timing estimation that estimates the third head timing of the received signal based on the waveform obtained by improving the resolution of the waveform of the second correlation function centering on the second head timing. Department and
A distance measuring unit that estimates the distance to the transmitting station based on the transmission timing obtained from the received signal and the reception timing of the received signal estimated from the third head timing.
A distance measuring device equipped with. The time window function unit cuts out the received signal including the preamble unit from the received signal.
The ranging device according to claim 1. The distance measuring device according to claim 1 or 2, further comprising a decoding unit that acquires the transmission timing by decoding the received signal. The first head timing is based on a third correlation function which is a cross-correlation function between the received signal, a signal unit reproduced based on the third head timing, and an extended known signal including a preamble part. The distance measuring device according to claim 1, wherein the fourth head timing of the received signal is estimated. The distance measuring device according to claim 4, wherein the extended known signal further includes a payload unit. The third head timing estimation unit is
A plurality of sample points are extracted from the second correlation function at predetermined intervals centered on the second start timing.
By performing interpolation processing on the plurality of extracted sample points, the resolution of the waveform of the second correlation function is improved.
The distance measuring device according to any one of claims 1 to 3. The third head timing estimation unit is
A plurality of sample points are extracted from the second correlation function at predetermined intervals centered on the second start timing.
By performing approximation processing on the plurality of extracted sample points, the resolution of the waveform of the second correlation function is improved.
The distance measuring device according to any one of claims 1 to 3. A ranging system that includes multiple ranging devices
The distance measuring device is
A first head timing estimation unit that estimates the first head timing of the received signal based on the first correlation function that is a cross-correlation function between the received signal and the known signal acquired from the transmitting station.
A time window function unit that multiplies the received signal by a time window function based on the first first timing and cuts out the received signal having a predetermined time window.
A second head timing estimation unit that estimates the second head timing of the received signal based on the second correlation function that is a cross-correlation function between the received signal and the known signal that has been cut out.
Third head timing estimation that estimates the third head timing of the received signal based on the waveform obtained by improving the resolution of the waveform of the second correlation function centering on the second head timing. Department and
A distance measuring unit that estimates the distance to the transmitting station based on the transmission timing obtained from the received signal and the reception timing of the received signal estimated from the third head timing.
Have,
Distance measurement system.

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