JP2010074564A - Packet detecting apparatus and packet detecting method, distance measuring device and distance measuring method, communication device, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine the arrival time of reply packet from a receiving end terminal in higher accuracy than that of a sampling clock in digital processing. <P>SOLUTION: The packet detecting apparatus shifts a tap coefficient of a digital filter with the same characteristic as the transmitting side at a plurality of timings smaller than a clock width, and it creates a plurality of kinds of known patterns through each of filters in advance and stores them. Then, the packet detecting apparatus computes a mutual correlation between each of a plurality of kinds of known patterns and a received signal, and estimates a timing corresponding to the known pattern having a maximum correlation value as the arrival time of packet. Thus, the arrival of packet position can be estimated in higher accuracy than that of sampling clock width. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless packet detection device and packet detection method, a distance measurement device and a distance measurement method, a communication device, and a computer program, and in particular, a transmission source (measurement side) terminal and a reception destination (measurement target side). The present invention relates to a packet detection device and a packet detection method of a communication method using packet transmission between terminals and a response procedure thereof, a distance measurement device and a distance measurement method, a communication device, and a computer program.

  More specifically, the present invention relates to a packet detection device and a packet detection method, a distance measurement device and a distance measurement method in which a transmission source terminal finds a reply packet from a reception destination terminal by correlation processing of a preamble part and determines an arrival time. The present invention relates to a communication apparatus and a computer program, and in particular, a packet detection apparatus and a packet detection method for determining the arrival time of a reply packet from a destination terminal at a transmission source terminal with higher accuracy (resolution) than a sampling clock in digital processing, The present invention relates to a distance measuring device, a distance measuring method, a communication device, and a computer program.

  A wireless network is attracting attention as a system free from wiring in the conventional wired communication system. For example, wireless LAN (Local Area Network) standards such as IEEE (The Institute of Electrical and Electronics Engineers) 802.11a / b, g are representative. According to the wireless LAN, flexible Internet connection is possible. In addition to replacing the existing wired LAN, Internet connection means can be provided in public places such as hotels, airport lounges, stations, and cafes.

  In many wireless communications, data transmission is performed in a multipath environment in which a direct wave and a plurality of reflected / delayed waves arrive at the receiving device. Therefore, delay distortion occurs due to multipath, and communication errors occur. May be caused. Therefore, in wireless LAN standards such as IEEE 802.11a / g, OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is employed. In the OFDM transmission system, transmission data is distributed and transmitted to a plurality of carriers whose frequencies are orthogonal to each other, so that the bandwidth of each carrier is narrow, the frequency utilization efficiency is very high, and it is resistant to frequency selective fading interference. is there.

  Wireless LANs are already widely used, but recently they are used not only for information devices such as personal computers (PCs) but also for small and light CE (Consumer Electronics) devices such as digital cameras, music players, and mobile phones. It is becoming common to install a wireless LAN function. Many wireless communications allow flexible connections with omnidirectional antennas. On the other hand, when a wireless LAN is mounted on a portable device, the antenna is required to be small, and a directional antenna is used to connect to a specific communication partner holding the device at a relatively close distance. An application such as Such an application requires a technique for detecting or estimating the distance to a communication partner that transmits and receives radio waves.

For example, the propagation speed of radio waves (3.0 × 10 ⁸ meters per second) in the elapsed time from radiating a radio wave toward the measurement object and receiving the reflected wave and transmitting the radio wave until receiving the reflected wave The distance can be measured by multiplying by. However, in such a method, it is necessary to transmit a highly directional radio wave toward the target to be measured, and since the time from transmission to reception of the reflected wave is short, the antenna is There are drawbacks such as the need to have two for transmission and one for reception.

  Therefore, communication system distance measurement is usually performed. For example, when the transmission source terminal A measures the distance to the reception destination terminal B, first, a packet for distance measurement is transmitted from the transmission source terminal A to the reception destination terminal B using an omnidirectional antenna. The receiving terminal B that has received the packet performs normal packet reception processing, decodes the data in the packet and understands that the packet is addressed to itself, and within a certain time after receiving the packet A packet is transmitted to A. The source terminal A receives the packet sent back from the destination terminal B, and receives the packet from the source terminal A to the destination terminal B and the packet in the destination terminal B after receiving the packet. The total processing delay time until the packet is sent back and the total time for the packet to reach the transmission source terminal A from the reception destination terminal B can be acquired. Here, if a certain processing time in the receiving terminal B is known in advance, it is possible to measure the time required for the packet traffic in the space. Then, by using this required time, the distance between the transmission source terminal A and the reception destination terminal B can be calculated. According to this method, the distance to a specific terminal can be measured.

  For example, a system has been proposed for ranging and positioning using packet transmission between a transmission source and a reception destination and a response procedure thereof (see, for example, Patent Document 1). When the wireless device 1 transmits a packet to the wireless device 2 that is a communication partner, the wireless device 2 always transmits the packet after an integral multiple of the unit time has elapsed since the packet was detected. The wireless device 1 measures the time from when it transmits a packet until it detects the packet of the wireless device 2 with a counter, and measures the time from when the wireless device 2 detects the packet to transmission and the processing time of the wireless device 1 itself. Ranging can be realized by converting the time subtracted from the time into the propagation distance with the wireless device 2 as the communication partner.

  In the distance measurement method using the packet transmission between the transmission source and the reception destination and the response procedure as described above, the transmission source, that is, the measurement side terminal transmits the packet, and then the reception destination, that is, the measurement target side. The time until receiving a reply packet from the terminal (that is, packet detection) is usually measured with reference to the clock in the transmission source terminal. Specifically, the time required for the round trip of the packet can be known by activating the counter when the packet is transmitted and observing the counter value when the reply packet from the receiving terminal is received. Here, when the reference clock for incrementing the internal counter has a period of 80 MHz, since one clock is 12.5 nanoseconds, the arrival time is measured with an accuracy (resolution) of 12.5 nanoseconds. Will do.

  Further, packet detection in a communication terminal is usually determined by correlating a known training sequence repeatedly included in a preamble, and the correlation value exceeds a predetermined threshold (see, for example, Patent Document 2). ). This packet detection process is performed in the digital domain.

For example, when correlation processing is performed on received data sampled with an 80 MHz clock, the arrival time of the return packet can be determined with a correlation output of 80 MHz accuracy (resolution). In other words, the packet arrival time measurement result is rounded to a clock width of 80 MHz. Further, by receiving a plurality of packets, it is possible to obtain the accuracy with finer precision than sampling at 80 MHz, but there is a problem that the effect of the averaging is limited. Considering that the propagation speed of radio waves is 3.0 × 10 ⁸ meters per second, it is difficult to ignore the effect that the accuracy of the packet arrival time is rounded to the sampling clock width.

Japanese Patent No. 3649404 Japanese Patent Laying-Open No. 2004-221940, paragraph 0202, FIG.

  The object of the present invention is to be able to suitably measure the distance between the terminals using the packet transmission between the transmission source (measurement side) terminal and the reception destination (measurement target side) terminal and its response procedure. Another object of the present invention is to provide a packet detecting device and a packet detecting method, a distance measuring device and a distance measuring method, a communication device, and a computer program.

  Further object of the present invention is that when performing distance measurement of the above communication method, the transmission source terminal can find the return packet from the reception destination terminal by correlation processing of the preamble part, and can appropriately determine the arrival time. An object is to provide an excellent packet detection device and packet detection method, a distance measurement device and a distance measurement method, a communication device, and a computer program.

  A further object of the present invention is to determine the arrival time of a return packet from a receiving terminal at a source terminal with higher accuracy than a sampling clock in digital processing when performing distance measurement of the communication method. An object is to provide an excellent packet detection device and packet detection method, a distance measurement device and a distance measurement method, a communication device, and a computer program.

The present application has been made in consideration of the above-described problems, and the invention according to claim 1 is a packet detection device for detecting a packet received from a communication partner, in a digital processing unit operating at a predetermined clock. In order to detect the packet by taking the cross-correlation of the known pattern added to the head of the received packet,
A plurality of types of cross-correlation obtained by passing the known pattern through a plurality of types of digital filters obtained by shifting the same tap coefficients as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A known pattern providing unit for cross-correlation that selectively provides a known pattern as a tap coefficient for cross-correlation;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival estimation unit that estimates arrival of a packet at a timing within a period of
A packet detection apparatus comprising:

The invention according to claim 2 of the present application is a packet detection device for detecting a packet received from a communication partner, and is added to the head of the received packet in a digital processing unit operating at a predetermined clock. In order to detect the packet by cross-correlating the known patterns,
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival estimation unit that estimates arrival of a packet at a timing within the period of the clock corresponding to
A packet detection apparatus comprising:

  The invention according to claim 3 of the present application further includes an averaging unit that averages the estimation results of the packet arrival estimation unit using a plurality of received packets, and the packet arrival estimation accuracy is improved by the averaging effect. It is to improve.

The invention according to claim 4 of the present application is a packet detection method for detecting a packet received from a communication partner, and is added to the head of the received packet in a digital processing unit operating at a predetermined clock. In order to detect the packet by cross-correlating the known patterns,
A plurality of types of cross-correlation known obtained by passing the known patterns through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. Providing a known pattern for cross-correlation that selectively provides a pattern;
The clock corresponding to the known pattern for cross-correlation which calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern for cross-correlation step, and becomes the maximum correlation value A packet arrival estimation step for estimating the arrival of a packet at a timing within a period of
A packet detection method characterized by comprising:

The invention according to claim 5 of the present application is a packet detection method for detecting a packet received from a communication partner, and is added to the head of the received packet in a digital processing unit operating at a predetermined clock. In order to detect the packet by cross-correlating the known patterns,
A plurality of types of received signals for cross-correlation obtained by passing the received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. A reception signal providing step for cross-correlation that selectively provides
A cross-correlation received signal that has a maximum correlation value by calculating a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing step. A packet arrival estimation step of estimating the arrival of a packet at a timing within the period of the clock corresponding to
A packet detection method characterized by comprising:

The invention according to claim 6 of the present application is a distance measuring device that performs distance measurement using a packet response procedure in a digital processing unit that operates with a predetermined clock,
A packet transmission time holding unit that holds the time at which the packet was transmitted to the communication partner;
A plurality of types of mutual gains obtained through known patterns respectively held in advance by a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A cross-correlation known pattern providing unit that selectively provides a known pattern for correlation;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within a period of
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring device comprising:
It is.

The invention according to claim 7 of the present application is a distance measuring device that performs distance measurement using a packet response procedure in a digital processing unit that operates with a predetermined clock,
A packet transmission time holding unit that holds the time at which the packet was transmitted to the communication partner;
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within the period of the clock corresponding to
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
It is a distance measuring device characterized by comprising.

The invention according to claim 8 of the present application is a distance measurement method in which distance measurement using a packet response procedure is performed in a digital processing unit operating with a predetermined clock,
A packet transmission time holding step for holding the time at which the packet was transmitted to the communication partner;
A plurality of types of mutual gains obtained through known patterns respectively held in advance by a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. Providing a known pattern for cross-correlation that selectively provides a known pattern for correlation;
The clock corresponding to the known pattern for cross-correlation which calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern for cross-correlation step, and becomes the maximum correlation value A packet arrival time estimation step for estimating a packet arrival time at a timing within a period of
A distance calculating step for calculating a distance from the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring method characterized by comprising:

The invention according to claim 9 of the present application is a distance measuring method for performing distance measurement using a packet response procedure in a digital processing unit operating with a predetermined clock,
A packet transmission time holding step for holding the time at which the packet was transmitted to the communication partner;
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A cross-correlation received signal providing step for selectively providing a signal;
A cross-correlation received signal that has a maximum correlation value by calculating a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing step. A packet arrival time estimation step for estimating a packet arrival time at a timing within a period of the clock corresponding to
A distance calculating step for calculating a distance from the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring method characterized by comprising:

The invention according to claim 10 of the present application is
A transmission / reception unit for transmitting / receiving packets to / from a communication partner;
A data processing unit that performs data processing of a packet to be transmitted to the communication partner and a packet received from the communication partner;
A distance determining unit that is arranged in a digital processing unit that operates at a predetermined clock and determines a distance to the communication partner;
Comprising
The distance discriminating unit
A packet transmission time holding unit that holds a time at which a packet is transmitted to the communication partner, and a plurality of types of tap coefficients that are shifted at a plurality of timings smaller than the clock width, the same tap coefficient as the digital filter used by the communication partner. A cross-correlation known pattern providing unit that selectively provides a plurality of types of cross-correlation known patterns obtained through known patterns respectively held in advance in the digital filter;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within a period of
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
Comprising
It is a communication apparatus characterized by this.

The invention according to claim 11 of the present application is
A transmission / reception unit for transmitting / receiving packets to / from a communication partner;
A data processing unit that performs data processing of a packet to be transmitted to the communication partner and a packet received from the communication partner;
A distance determining unit that is arranged in a digital processing unit that operates at a predetermined clock and determines a distance to the communication partner;
Comprising
The distance discriminating unit
A packet transmission time holding unit that holds a time at which a packet is transmitted to the communication partner, and a plurality of types of tap coefficients that are shifted at a plurality of timings smaller than the clock width, the same tap coefficient as the digital filter used by the communication partner. A cross-correlation reception signal providing unit that selectively provides a plurality of types of cross-correlation reception signals obtained by passing the reception signals through the digital filter;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within the period of the clock corresponding to
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
Comprising
It is a communication apparatus characterized by this.

In the invention according to claim 12 of the present application, in the digital processing unit operating at a predetermined clock, the packet is detected by taking the cross-correlation of the known pattern added to the head of the packet received from the communication partner. A computer program written in a computer-readable format to execute the process on a computer,
A plurality of types of cross-correlation obtained by passing the known pattern through a plurality of types of digital filters obtained by shifting the same tap coefficients as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A known pattern providing unit for cross-correlation that selectively provides a known pattern;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival estimation unit that estimates the arrival of a packet at a timing within a period of
It is a computer program to function as.

In the invention according to claim 13 of the present application, in the digital processing unit operating at a predetermined clock, the packet is detected by taking the cross-correlation of the known pattern added to the head of the packet received from the communication partner. A computer program written in a computer-readable format to execute the process on a computer,
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival estimation unit that estimates arrival of a packet at a timing within a period of the clock corresponding to
It is a computer program to function as.

  The computer program according to each of claims 12 and 13 of the present application defines a computer program described in a computer-readable format so as to realize predetermined processing on a computer. In other words, by installing the computer program according to each of claims 12 and 13 of the present application on a computer, a cooperative action is exhibited on the computer, and packet detection according to each of claims 1 and 2 of the present application. The same effects as the device can be obtained.

  According to the present invention, it is possible to preferably measure the distance between the terminals using the packet transmission between the transmission source (measurement side) terminal and the reception destination (measurement target side) terminal and its response procedure. A packet detection device and a packet detection method, a distance measurement device and a distance measurement method, a communication device, and a computer program can be provided.

  According to the present invention, when measuring the distance of the above communication method, the transmission source terminal can find the return packet from the reception destination terminal by the correlation processing of the preamble part, and can appropriately determine the arrival time. An excellent packet detection device and packet detection method, distance measurement device and distance measurement method, communication device, and computer program can be provided.

  Further, according to the present invention, when measuring the distance of the above communication method, it is possible to determine the arrival time of the return packet from the destination terminal at the transmission source terminal with higher accuracy than the sampling clock in the digital processing. An excellent packet detection device and packet detection method, distance measurement device and distance measurement method, communication device, and computer program can be provided.

  At the time of packet transmission, a digital filter is used to limit the band, and a digital filter having the same characteristics is also used on the receiving side in a normal wireless communication device. According to the invention described in claims 1, 4, and 12 of the present application, the tap coefficient of the digital filter having the same characteristic as that of the transmission side is shifted at a plurality of timings smaller than the clock width, and a plurality of types are passed through each filter. The known pattern is prepared, the cross-correlation is calculated with each of a plurality of types of known patterns with the received signal, and the timing corresponding to the known pattern having the maximum correlation value is estimated as the arrival time of the packet. The arrival of the packet position can be estimated with higher accuracy than the sampling clock width in the processing unit.

  In addition, according to the invention described in claims 2, 5 and 13 of the present application, a plurality of types of digital filters in which the tap coefficients of the digital filter having the same characteristics as the transmission side are shifted at a plurality of timings smaller than the clock width. Each of the received signals is passed through, and the cross-correlation between each signal and the known pattern is sequentially calculated, and the timing corresponding to the known pattern having the maximum correlation value is estimated as the arrival time of the packet. The arrival of the packet position can be estimated with higher accuracy than the clock width.

  Further, according to the invention described in claim 3 of the present application, the correlation output corresponding to each digital shifted by timing finer than the clock width is obtained by the effect of averaging the packet arrival estimation results using a plurality of packets. The accuracy of comparison can be increased.

  The inventions described in claims 6, 8 and 10 of the present application measure the distance of a communication method using packet transmission with a communication partner and its response procedure. The tap coefficient of the filter is shifted at multiple timings finer than the clock width, multiple types of known patterns are prepared through each filter, and cross correlation is calculated with each of the multiple types of known patterns with the received signal Since the timing corresponding to the known pattern having the maximum correlation value is estimated as the packet arrival time, it is possible to estimate the packet arrival time with higher accuracy than the sampling clock width in the digital processing unit. , Improve the accuracy of distance measurement.

  Further, the invention according to claims 7, 9, and 11 of the present application performs distance measurement of a communication method using packet transmission with a communication partner and a response procedure thereof. The received signal is passed through multiple types of digital filters with the tap coefficient of the filter shifted at multiple timings finer than the clock width, and the cross-correlation between each signal and the known pattern is sequentially calculated, and the maximum correlation value and Since the timing corresponding to the known pattern is estimated as the packet arrival time, it is possible to estimate the packet arrival time with a higher accuracy than the sampling clock width in the digital processing unit, improving the accuracy of distance measurement To do.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

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

  FIG. 9 shows a configuration example of a computer equipped with a wireless communication function.

  A CPU (Central Processing Unit) 1 executes a program stored in a ROM (Read Only Memory) 2 or a hard disk drive (HDD) 11 under a program execution environment provided by an operating system (OS). . For example, the received packet synchronization process described later or a part of the process can be realized in a form in which the CPU 1 executes a predetermined program.

  The ROM 2 permanently stores program codes such as POST (Power On Self Test) and BIOS (Basic Input Output System). A RAM (Random Access Memory) 3 is used to load a program stored in the ROM 2 or the HDD 11 when the CPU 1 executes it, or to temporarily hold work data of the program being executed. These are connected to each other by a local bus 4 directly connected to a local pin of the CPU 1.

  The local bus 4 is connected via a bridge 5 to an input / output bus 6 such as a peripheral component interconnect (PCI) bus.

  A keyboard 8 and a pointing device 9 such as a mouse are input devices operated by a user. The display 10 includes an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays various information as text and images.

  The HDD 11 is a drive unit incorporating a hard disk as a recording medium, and drives the hard disk. The hard disk is used for installing programs executed by the CPU 1 such as an operating system and various applications, and for storing data files and the like.

  The communication unit 12 is a wireless communication interface according to, for example, IEEE802.11a / n, and operates as an access point or a terminal station in the infrastructure mode, or operates in the ad hoc mode, and is in the communication range. Execute communication with the communication terminal. In the present embodiment, the communication unit 12 measures the distance of a communication method using packet transmission with a communication partner and a response procedure thereof (described later).

  FIG. 1 schematically shows a configuration example in the communication unit 12 equipped in the computer shown in FIG. It is assumed that the digital processing of the illustrated communication device operates based on, for example, an 80 MHz clock. The illustrated communication device is assumed to be used for a plurality of communication systems using different channels such as IEEE802.11a and IEEE802.11b. Since IEEE802.11a uses a frequency channel of 5 GHz band and IEEE802.11b uses a frequency channel of 2.4 GHz band (well-known), the transmission / reception branch is for an RF transmission / reception unit for 5 GHz band and for 2.4 GHz band. The combination of the RF transmitter / receiver is provided. However, the gist of the present invention is not limited to a communication device corresponding to a plurality of channels.

  The transmission / reception antenna 101 is connected to the RF transmission / reception circuit unit 103 via the antenna switch 102. The RF transmission / reception circuit unit 103 includes, as a reception system, a low noise amplifier (LNA), an orthogonal demodulator (IQ demodulator) that down-converts a reception signal in the RF frequency band, and an AD converter in which the power of the reception signal is in a subsequent stage Equipped with an AGC (Automatic Gain Control) amplifier that normalizes to fit within the dynamic range of (Analog to Digital Converter: ADC), an analog low-pass filter (LPF) that removes signal components other than the desired band, etc. Also, as a transmission system, an analog LPF that removes signal components other than the desired band from the analog transmission signal after DA conversion, a quadrature modulator (IQ modulator) that upconverts to a transmission signal in the RF frequency band, Power amplifier for power-amplifying the signal (Power Amplifier) (not shown either) composed like.

  Further, as described above, the communication device is assumed to be used in a multipath communication environment in which IEEE802.11a using the 5 GHz band and IEEE802.11b using the 2.4 GHz band coexist. The transmission / reception circuit unit 103 includes a 5 GHz band RF transmission / reception unit 103A and a 2.4 GHz band RF transmission / reception unit 103B.

  Each of the RF transmission / reception processing units 103A and 103B is connected to an AD converter (ADC) 105A and a DA converter (DAC) 105B via a switch 104.

  The transmission data processing unit 109 divides the transmission data stream passed from the higher-level processing unit 110 into packets, performs processing such as encoding, and then passes them to the DA converter 105B. In a communication system that employs the OFDM modulation scheme, OFDM modulation processing such as IFFT (Inverse FFT: Inverse Fast Fourier Transform) calculation is performed. The transmission digital filter 106B limits the band on the digital transmission signal immediately before analog conversion.

  The reception digital filter 106A limits the band of the reception signal digitally converted by the AD converter 105A. In a normal communication device, a digital filter having the same characteristics as the transmission side (that is, composed of the same tap coefficients) is used on the reception side.

  The synchronization processing unit 107 uses rough determination of reception timing (temporary reception timing) based on packet discovery, frequency offset correction, noise estimation, and provisional reception timing for the digital reception signal subjected to band limitation. Processing such as more accurate reception timing extraction is performed. The temporary reception timing can be determined based on the autocorrelation calculation of the known burst-like reference signal at the head of the packet. In addition, accurate reception timing can be determined based on cross-correlation calculation of known reference signals.

  Then, the received data processing unit 108 performs a decoding process on the portion (information field) after the synchronization processing, reproduces the original data, and passes it to the higher-level processing unit 110. In a communication system employing the OFDM modulation scheme, OFDM demodulation processing such as FFT operation is performed.

  Note that a packet generally includes a known signal portion composed of a training sequence shared between transmission and reception and an information signal portion (user data) composed of a header and a payload (see FIG. 10). In the frame format in IEEE802.11a / g, a preamble section (STF: Short Training Field) consisting of a short training sequence (STS) that can be used for temporary reception timing determination and frequency offset, and accurate reception timing extraction Although a preamble section (LTF) consisting of a long training sequence (LTS) that is cut by use is defined, detailed description thereof is omitted in this specification.

  The communication device according to the present embodiment performs distance measurement of a communication method using packet transmission with a communication partner and a response procedure thereof, which will be described in detail below.

The communication device shown in FIG. 1 stores the time at which a packet is transmitted to the communication partner in the packet transmission time holding unit 121, and the packet arrival time determination unit 122 determines the arrival time of the reply packet from the communication partner at the beginning of the packet. Discrimination is performed based on cross-correlation calculation of known patterns. Since the distance calculation unit 124 knows in advance a certain processing time from when a packet is received on the communication partner side to when it is returned, the processing time is removed from the time difference between the packet transmission time and the packet arrival time. The time required for packet traffic is obtained above. Then, by dividing the one-half of the time required by the radio wave propagation speed (per 3.0 × 10 ⁸ meters), it is possible to calculate the distance to the communication partner.

  When the packet arrival time discriminating unit 122 performs correlation processing based on the clock in the communication device, when the reference clock has a period of 80 MHz, the arrival time is measured with an accuracy of 12.5 nanoseconds. That is, there is a concern that the resolution for time discrimination is rounded down to the clock width, and sufficient distance measurement accuracy cannot be obtained.

  Therefore, in the present embodiment, the tap coefficients of the digital filter are shifted at a plurality of fine timings within the clock width, and a plurality of types of known patterns are used for correlation by passing these patterns through the plurality of types of digital filters. The arrival position of the packet is determined with an accuracy higher than the accuracy of the clock width by creating and detecting the maximum one of the correlation outputs between the plurality of known patterns and the received signal.

  FIG. 2 illustrates a mechanism in which the packet arrival time discriminating unit 122 discriminates the packet arrival time by cross-correlation with a known pattern.

  The cross-correlation known pattern providing unit 123 first subdivides the clock width into, for example, 100 equal parts, and prepares a known pattern for correlation for each subdivided timing. Specifically, the digital filter tap coefficient of the same characteristics as the transmission digital filter on the communication partner side is shifted at a plurality of fine timings divided into 100 equal parts to create 100 types of digital filters. By passing the defined known patterns through each digital filter, 100 kinds of known patterns corresponding to the respective timings obtained by dividing the clock width into 100 equal parts can be created. A known pattern consists of a set of tap coefficients for each sampling period.

The values of the black circles in FIG. 3 are the tap coefficients of the basic digital filter. In FIG. 4 and FIG. 5, the tap coefficients shifted at fine timings within the clock width are represented by black circles. . The cross-correlation known pattern providing unit 123 includes N tap coefficients W _i (0), W _i (1),..., W _i (N−1) obtained by passing the known patterns through these digital filters. Is stored as a known pattern for correlation at each shifted timing (however, the subscript i is the serial number of the timing obtained by subdividing the clock width).

The packet arrival time determination unit 122 includes a delay unit 201 configured by serially connecting a plurality (N) of delay elements each having a delay time corresponding to a sample period, and the delay unit 202 as a whole is a timing estimation section. Give delay time. On the other hand, the cross-correlation known pattern providing unit 123 holds 100 kinds of correlation known patterns corresponding to each timing obtained by subdividing the clock width into 100 equal parts, and represents a tap coefficient representing a known pattern for each timing i. W _i (0), W _i (1),..., W _i (N−1) are sequentially selected by the selection unit 204 and supplied to the packet arrival time determination unit 122.

The correlation known pattern consists of a set of N tap coefficients for each sampling period (described above). The packet arrival time determination section 122, the received signal samples delayed by one sample by the delay elements of the delay unit 201, each tap coefficient of each of the delayed signal from the cross-correlation for the known pattern providing section 123 W _i (0), W _i (1),..., W _i (N−1) are multiplied and summed by the summation unit 202, and the processing is repeated for each timing obtained by subdividing the clock width into 100 equal parts. The cross-correlation value for each subdivided timing can be obtained.

  Since the peak detection unit 203 estimates the timing corresponding to the known pattern having the maximum correlation value as the arrival time of the packet, it estimates the arrival of the packet position with higher accuracy than the sampling clock width in the digital processing unit. It becomes possible.

  FIG. 6 shows an example of a cross-correlation output between a received signal and a known pattern for cross-correlation corresponding to a certain timing. The input data corresponding to the peak value of the correlation output is estimated as the input sequence having the highest correlation with the N tap coefficients, and becomes a candidate for the arrival time of the packet at the timing. In the present embodiment, the peak detection unit 203 takes a packet having the highest correlation among the arrival time candidates of packets obtained at each timing obtained by subdividing the clock width.

  Further, the accuracy of comparing the correlation outputs corresponding to the respective digital signals shifted at timings smaller than the clock width can be improved by the effect of averaging the packet arrival estimation results using a plurality of packets.

  The processing procedure for the communication device to measure the distance to the communication partner is summarized below.

Step 1:
A packet is transmitted to the communication partner, and a counter is started with an 80 MHz clock.
Step 2:
When the communication partner receives the packet, it sends back the packet with a fixed number of clocks (for example, within 100 clocks). At the same time, the communication partner acquires the packet arrival position with a precision (correlation corresponding to 100 types of filters) finer than the clock width, and sends back this position information together.
Step 3:
A packet from the communication partner is received, the reception position is acquired with 100 kinds of accuracy smaller than the clock width, and the 80 MHz counter is stopped.
Step 4:
Calculate turnaround time. The turnaround time here is a value obtained by multiplying a counter value of 80 MHz by a constant delay clock on the communication partner side, a high accuracy correction value on the communication partner side, and a high accuracy correction value on the own terminal. .
Step 5:
Divide the turnaround time by 2 and further divide by the radio wave propagation speed (3.0 × 10 ⁸ meters per second) to find the distance.

  FIG. 7 shows a processing procedure for estimating the arrival time with high accuracy from the maximum value of the correlation coefficient using 100 types of filters in the above procedures 2 and 3, in the form of a flow chat. In the illustrated flowchart, the maximum value A is the final maximum value, and the maximum value B is the temporary maximum value.

  First, a cross-correlation between a received pattern and a known pattern generated through a basic (that is, timing is not shifted from a reference clock) digital filter is obtained (step S1).

  Then, when the correlation result as shown in FIG. 6 is obtained, the maximum peak value of the correlation value is acquired and held as the maximum value A (step S2).

  Next, 1 is substituted into the variable i (step S3). i is a variable used for designating the serial number of the digital filter.

  Next, the cross correlation between the received pattern and the known pattern created through the i-th digital filter is obtained with respect to the reception data at three timings including the timing at which the cross correlation peaks and the timing before and after the timing, The maximum value among the above three timing cross-correlation values is set as the maximum value B (step S4). The maximum value B is the maximum temporary value.

  Next, the obtained maximum value B and the previously obtained maximum value A are compared in magnitude (step S5). If the maximum value B is larger (Yes in step S5), the maximum value B is substituted for the maximum value A (step S6).

  Then, until i reaches 100 (No in step S7), i is incremented by 1 (step S8), and the process returns to step S4. In this way, the process for obtaining the cross-correlation is repeatedly executed for the known pattern created by the digital filter shifted to all timings with the clock width subdivided. Then, the maximum value A is output as the final maximum value.

  As a modification of the communication apparatus having the distance measuring function shown in FIG. 1, the received signal is not a known pattern for cross-correlation, but a received digital filter corresponding to a plurality of timings in which the clock width is subdivided. Thus, it is expected that the same effect can be obtained even if the correlation between one known pattern and a plurality of types of received signals is obtained.

  FIG. 8 schematically shows a configuration example of this communication device. The digital processing of the illustrated communication device is assumed to operate based on, for example, an 80 MHz clock, and is assumed to be used for a plurality of communication systems using different channels such as IEEE802.11a and IEEE802.11b (same as above). ).

  The transmission / reception antenna 101 is connected to the RF transmission / reception circuit unit 103 via the antenna switch 102. The RF transmission / reception circuit unit 103 includes an LNA, a quadrature demodulator, an AGC amplifier, an analog LPF, and the like as a reception system, and an analog LPF, a quadrature modulator, a power amplification amplifier, and the like as a transmission system (all are Not shown).

  The RF transmission / reception circuit unit 103 for each transmission / reception branch includes a 5 GHz band RF transmission / reception unit 103A and a 2.4 GHz band RF transmission / reception unit 103B. Each of the RF transmission / reception processing units 103A and 103B is connected to an AD converter (ADC) 105A and a DA converter (DAC) 105B via a switch 104.

  The transmission data processing unit 109 divides the transmission data stream passed from the higher-level processing unit 110 into packets, performs processing such as encoding, and then passes them to the DA converter 105B. The transmission digital filter 106B limits the band on the digital transmission signal immediately before analog conversion.

  The reception digital filter 106A limits the band of the reception signal digitally converted by the AD converter 105A. In a normal communication device, a digital filter having the same characteristics as that of the transmission side is used on the reception side.

  The synchronization processing unit 107 performs rough reception timing determination, frequency offset correction, noise estimation, extraction of more accurate reception timing using provisional reception timing, and the like for the digital reception signal after band limitation is performed. Processing is performed. Then, the received data processing unit 108 performs a decoding process on the portion (information field) after the synchronization processing, reproduces the original data, and passes it to the higher-level processing unit 110.

The communication device shown in FIG. 1 stores the time at which a packet is transmitted to the communication partner in the packet transmission time holding unit 121, and the packet arrival time determination unit 122 determines the arrival time of the reply packet from the communication partner at the beginning of the packet. Discrimination is performed based on cross-correlation calculation of known patterns. Since the distance calculation unit 124 knows in advance a certain processing time from when a packet is received on the communication partner side to when it is returned, the processing time is removed from the time difference between the packet transmission time and the packet arrival time. The time required for packet traffic is obtained above. Then, the distance to the communication partner is calculated by dividing half of the required time by the propagation speed of radio waves (3.0 × 10 ⁸ meters per second).

  At the time of distance measurement, the tap coefficient providing unit 801 supplies a plurality of types (for example, 100 types) of tap coefficients shifted with fine timing within the clock width to the reception digital filter 106A. Accordingly, the packet arrival time discriminating unit 122 discriminates the arrival position of the packet with an accuracy higher than the accuracy of the clock width by detecting the maximum correlation output between one type of known pattern and a plurality of types of received signals. can do.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  The scope of application of the present invention is not limited to wireless LAN standards such as IEEE802.11a / n, and the present invention can be applied to various digital wireless technologies.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1 is a diagram illustrating a configuration example of a communication device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a mechanism for determining the packet arrival time by the cross-correlation calculation with the known pattern in the packet arrival time determination unit 122. FIG. 3 is a diagram illustrating tap coefficients of a basic digital filter. FIG. 4 is a diagram illustrating tap coefficients obtained by shifting the digital filter shown in FIG. 3 at a fine timing within the clock width. FIG. 5 is a diagram illustrating tap coefficients obtained by shifting the digital filter shown in FIG. 3 at a fine timing within the clock width. FIG. 6 is a diagram illustrating an example of a cross-correlation output between a received pattern and a known pattern for cross-correlation corresponding to a certain timing. FIG. 7 is a flow chat showing a processing procedure for estimating the arrival time with high accuracy from the maximum value of the correlation coefficient using 100 types of filters. FIG. 8 is a diagram illustrating a configuration example of a communication device according to another embodiment of the present invention. FIG. 9 is a diagram illustrating a configuration example of a computer having a wireless communication function. FIG. 10 is a diagram schematically illustrating a packet configuration.

Explanation of symbols

1 ... CPU
2 ... ROM
3 ... RAM
4 ... Local bus 5 ... Bridge 6 ... I / O bus 7 ... I / O interface 8 ... Keyboard 9 ... Pointing device (mouse)
10 ... Display 11 ... HDD
DESCRIPTION OF SYMBOLS 12 ... Communication part 101 ... Antenna 102 ... Antenna switch 103 ... RF transmission / reception circuit part 103A ... RF transmission / reception circuit part for 5 GHz band 103B ... RF transmission / reception circuit part for 2.4 GHz band 104 ... Switch 105A ... AD converter (ADC), 105B ... DA converter (DAC)
106A ... Reception digital filter 106B ... Transmission digital filter 107 ... Synchronization processing unit 108 ... Reception data processing unit 109 ... Transmission data processing unit 110 ... Upper processing unit 121 ... Packet transmission time holding unit 122 ... Packet arrival time determination unit 123 ... Cross correlation known pattern providing unit 124 ... distance calculating unit 201 ... delay unit 202 ... totaling unit 203 ... peak detecting unit 204 ... selecting unit 801 ... tap coefficient providing unit

Claims (13)

A packet detection apparatus for detecting a packet received from a communication partner, and detecting a packet by taking a cross-correlation of a known pattern added to the head of the received packet in a digital processing unit operating at a predetermined clock. To do
A plurality of types of cross-correlation known obtained by passing the known patterns through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. A known pattern providing unit for cross-correlation that selectively provides a pattern;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival estimation unit that estimates arrival of a packet at a timing within a period of
A packet detection apparatus comprising: A packet detection apparatus for detecting a packet received from a communication partner, and detecting a packet by taking a cross-correlation of a known pattern added to the head of the received packet in a digital processing unit operating at a predetermined clock. To do
A plurality of types of received signals for cross-correlation obtained by passing the received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival estimation unit that estimates arrival of a packet at a timing within the period of the clock corresponding to
A packet detection apparatus comprising: An averaging unit that averages the estimation results of the packet arrival estimation unit using a plurality of received packets;
The packet detection apparatus according to claim 1, wherein the packet detection apparatus is a packet detection apparatus. A packet detection method for detecting a packet received from a communication partner, wherein a packet is detected by taking a cross-correlation of a known pattern added to the head of the received packet in a digital processing unit operating at a predetermined clock. To do
A plurality of types of cross-correlation known obtained by passing the known patterns through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. Providing a known pattern for cross-correlation that selectively provides a pattern;
The clock corresponding to the known pattern for cross-correlation which calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern for cross-correlation step, and becomes the maximum correlation value A packet arrival estimation step for estimating the arrival of a packet at a timing within a period of
A packet detection method comprising: A packet detection method for detecting a packet received from a communication partner, wherein a packet is detected by taking a cross-correlation of a known pattern added to the head of the received packet in a digital processing unit operating at a predetermined clock. To do
A plurality of types of received signals for cross-correlation obtained by passing the received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used at the communication partner at a plurality of timings finer than the clock width. A reception signal providing step for cross-correlation that selectively provides
A cross-correlation received signal that has a maximum correlation value by calculating a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing step. A packet arrival estimation step of estimating the arrival of a packet at a timing within the period of the clock corresponding to
A packet detection method comprising: A distance measuring device that performs distance measurement using a packet response procedure in a digital processing unit that operates with a predetermined clock,
A packet transmission time holding unit that holds the time at which the packet was transmitted to the communication partner;
A plurality of types of mutual gains obtained through known patterns respectively held in advance by a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A cross-correlation known pattern providing unit that selectively provides a known pattern for correlation;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within a period of
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring device comprising: A distance measuring device that performs distance measurement using a packet response procedure in a digital processing unit that operates with a predetermined clock,
A packet transmission time holding unit that holds the time at which the packet was transmitted to the communication partner;
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within the period of the clock corresponding to
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring device comprising: A distance measuring method for performing distance measurement using a packet response procedure in a digital processing unit operating with a predetermined clock,
A packet transmission time holding step for holding the time at which the packet was transmitted to the communication partner;
A plurality of types of mutual gains obtained through known patterns respectively held in advance by a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. Providing a known pattern for cross-correlation that selectively provides a known pattern for correlation;
The clock corresponding to the known pattern for cross-correlation which calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern for cross-correlation step, and becomes the maximum correlation value A packet arrival time estimation step for estimating a packet arrival time at a timing within a period of
A distance calculating step for calculating a distance from the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring method characterized by comprising: A distance measuring method for performing distance measurement using a packet response procedure in a digital processing unit operating with a predetermined clock,
A packet transmission time holding step for holding the time at which the packet was transmitted to the communication partner;
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A cross-correlation received signal providing step for selectively providing a signal;
A cross-correlation received signal that has a maximum correlation value by calculating a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing step. A packet arrival time estimation step for estimating a packet arrival time at a timing within a period of the clock corresponding to
A distance calculating step for calculating a distance from the communication partner based on a time difference between the packet transmission time and the packet arrival time;
A distance measuring method characterized by comprising: A transmission / reception unit for transmitting / receiving packets to / from a communication partner;
A data processing unit that performs data processing of a packet to be transmitted to the communication partner and a packet received from the communication partner;
A distance determining unit that is arranged in a digital processing unit that operates at a predetermined clock and determines a distance to the communication partner;
Comprising
The distance discriminating unit
A packet transmission time holding unit for holding a time at which a packet is transmitted to the communication partner;
A plurality of types of mutual gains obtained through known patterns respectively held in advance by a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A cross-correlation known pattern providing unit that selectively provides a known pattern for correlation;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within a period of
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
Comprising
A communication device. A transmission / reception unit for transmitting / receiving packets to / from a communication partner;
A data processing unit that performs data processing of a packet to be transmitted to the communication partner and a packet received from the communication partner;
A distance determining unit that is arranged in a digital processing unit that operates at a predetermined clock and determines a distance to the communication partner;
Comprising
The distance discriminating unit
A packet transmission time holding unit for holding a time at which a packet is transmitted to the communication partner;
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival time estimation unit that estimates the arrival time of a packet at a timing within the period of the clock corresponding to
A distance calculator that calculates a distance to the communication partner based on a time difference between the packet transmission time and the packet arrival time;
Comprising
A communication device. A computer-readable format for executing processing on a computer for detecting a packet by taking a cross-correlation of a known pattern added to the head of a packet received from a communication partner in a digital processing unit that operates at a predetermined clock. A computer program described in claim 1, wherein the computer is
A plurality of types of cross-correlation obtained by passing the known pattern through a plurality of types of digital filters obtained by shifting the same tap coefficients as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A known pattern providing unit for cross-correlation that selectively provides a known pattern;
The clock corresponding to the known pattern for cross-correlation that calculates the cross-correlation between the received signal and each of the plurality of types of known patterns for cross-correlation provided from the known pattern-providing unit for cross-correlation, and becomes the maximum correlation value A packet arrival estimation unit that estimates the arrival of a packet at a timing within a period of
A computer program that functions as a computer. A computer-readable format for executing processing on a computer for detecting a packet by taking a cross-correlation of a known pattern added to the head of a packet received from a communication partner in a digital processing unit that operates at a predetermined clock. A computer program described in claim 1, wherein the computer is
A plurality of types of cross-correlation receptions obtained by passing received signals through a plurality of types of digital filters obtained by shifting the same tap coefficient as the digital filter used by the communication partner at a plurality of timings finer than the clock width. A reception signal providing unit for cross-correlation that selectively provides a signal;
A cross-correlation received signal that calculates a cross-correlation between a known pattern held in advance and each of a plurality of types of cross-correlation received signals provided from the cross-correlation received signal providing unit, and has a maximum correlation value. A packet arrival estimation unit that estimates arrival of a packet at a timing within a period of the clock corresponding to
A computer program that functions as a computer.

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