JP2006038771A - Distance measuring system, distance measuring method, and communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance measuring system and a distance measuring method for measuring a distance between radio terminals by a simple structure and at a low cost, and to provide a communication device. <P>SOLUTION: A radio wave is transmitted from a communication device provided on a first mobile terminal to a second mobile terminal. A direct wave and an indirect wave transmitted from the first mobile terminal are received by a communication device provided on the second mobile terminal to detect delay time ΔT between the direct and indirect waves. Further, a distance d between the first and second mobile terminals is calculated based on the detected delay time ΔT, the height h1 of an antenna 11A of the first mobile terminal, the height h2 of an antenna 11B of the second mobile terminal, and the propagation velocity c of the radio wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a distance measurement system, a distance measurement method, and a communication device that measure a distance between wireless terminals.

  In a wireless ad hoc network, wireless communication can be performed between mobile terminals without going through an infrastructure such as a base station. A mobile terminal constituting such a wireless ad hoc network has not only a function of a transmitter / receiver but also a function of a relay station, and the mobile terminal itself also functions as a router. When communication is performed between two mobile terminals, multihop communication using another mobile terminal as a relay station can be performed. As a result, even when radio waves do not reach between the two mobile terminals to be communicated, communication is possible via other mobile terminals.

  When each mobile terminal performs communication using an omnidirectional beam, the mobile terminal can communicate with a plurality of mobile terminals located in different directions. However, interference between the same channels occurs in communication between a plurality of sets of mobile terminals. Therefore, communication is performed using a directional beam so that interference between the same channels does not occur. In this case, in order to select a multi-hop communication route, it is necessary to know the positions of a plurality of mobile terminals constituting the network. For this purpose, each mobile terminal must always know the distance and direction to a plurality of other mobile terminals that are moving.

Conventionally, various mobile communication systems capable of measuring the position of a mobile terminal have been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 11-178038

  In the above conventional mobile communication system, the positioning device of the mobile radio terminal device transmits a positioning signal to the communication control center, measures the radio wave propagation delay time (phase) from the returned positioning signal, and the radio wave propagation delay Measure distance from time (phase).

  However, in the above conventional mobile communication system, each mobile radio terminal device can measure the distance to the communication control center, but each mobile radio terminal device directly measures the distance to other mobile radio terminal devices. It is not possible.

  Various radars that measure the distance to a moving object have also been developed, but the structure is complex and expensive.

  In order to perform multi-hop communication between mobile terminals in a wireless ad hoc network, it is desired to be able to measure the distance to the mobile terminal with a simple configuration and low cost.

  An object of the present invention is to provide a distance measurement system, a distance measurement method, and a communication device that can measure a distance between wireless terminals with a simple configuration and at low cost.

  A distance measurement system according to a first invention is a distance measurement system for measuring a distance between a plurality of wireless terminals, and includes a first antenna provided in one wireless terminal among the plurality of wireless terminals, A transmission means for transmitting radio waves from the first antenna to other radio terminals among the plurality of radio terminals, and a second antenna provided in the other radio terminals, and for transmitting radio waves transmitted from one radio terminal A receiving means for receiving a direct wave as a direct wave through the second antenna and receiving a radio wave transmitted from one wireless terminal and reflected by a predetermined surface as an indirect wave through the second antenna; Detection means for detecting a delay time until reception of the indirect wave by the reception means, delay time detected by the detection means, height of the first antenna from the predetermined plane, height of the second antenna from the predetermined plane And based on the propagation speed of the radio wave is obtained by a calculation means for calculating the distance between the first antenna and the other of the second antenna of the wireless terminal of the one wireless terminal.

  The predetermined surface is a road surface, a ceiling surface, a side wall surface, a floor surface, or the like.

  In the distance measurement system according to the present invention, radio waves are transmitted from the first antenna provided in one of the plurality of wireless terminals to the other wireless terminal among the plurality of wireless terminals by the transmission means. A radio wave transmitted from one wireless terminal is directly received by a receiving means through a second antenna provided in another wireless terminal as a direct wave, and a radio wave transmitted from one wireless terminal and reflected on a predetermined surface is received. The indirect wave is received by the receiving means through the second antenna. The delay time from the reception of the direct wave by the receiving means to the reception of the indirect wave by the receiving means is detected by the detecting means. Based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, the first of the one wireless terminal is calculated by the calculation means. The distance between the other antenna and the second antenna of the other wireless terminal is calculated.

  In this way, the direct wave transmitted directly from the first antenna of one wireless terminal to the second antenna of the other wireless terminal and the reflection on the predetermined surface from the first antenna of the one wireless terminal By using the indirect wave transmitted to the second antenna of another wireless terminal, it becomes possible to measure the distance between the wireless terminals with a simple configuration and at a low cost.

  The calculation means sets the delay time detected by the detection means to ΔT, sets the height of the first antenna from the predetermined plane to h1, sets the height of the second antenna from the predetermined plane to h2, and sets the propagation speed of the radio wave. Where c is

  A distance d between the first antenna of one wireless terminal and the second antenna of another wireless terminal may be calculated.

  In this case, using the delay time ΔT detected by the detection means, the known first antenna height h1, the known second antenna height h2, and the known radio wave propagation speed c, The distance d between the first antenna and the second antenna of another wireless terminal can be easily calculated.

  The plurality of wireless terminals may be mobile terminals provided on a moving body that moves on a predetermined plane. In this case, it is possible to measure the distance between the mobile terminals provided on the moving body moving on the predetermined plane with a simple configuration and at low cost.

  A communication device according to a second invention is a communication device that is provided in one wireless terminal having a first antenna and receives radio waves transmitted from another wireless terminal having a second antenna. Receiving means for directly receiving a radio wave transmitted from a wireless terminal as a direct wave through the first antenna and receiving a radio wave transmitted from another wireless terminal and reflected by a predetermined surface as an indirect wave through the first antenna; A detecting means for detecting a delay time from reception of a direct wave by the receiving means to reception of an indirect wave by the receiving means; a delay time detected by the detecting means; a height of the first antenna from a predetermined plane; And a calculating means for calculating a distance between the first antenna of one radio terminal and the second antenna of another radio terminal based on the height of the second antenna and the propagation speed of radio waves. It is.

  In the communication apparatus according to the present invention, a radio wave transmitted from another radio terminal is directly received by the receiving means through the first antenna as a direct wave, and is also transmitted from the other radio terminal and reflected by a predetermined surface. Is received by the receiving means through the first antenna as an indirect wave. The delay time from the reception of the direct wave by the receiving means to the reception of the indirect wave by the receiving means is detected by the detecting means. Based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, the first of the one wireless terminal is calculated by the calculation means. The distance between the other antenna and the second antenna of the other wireless terminal is calculated.

  As described above, the direct wave transmitted directly from the second antenna of the other wireless terminal to the first antenna and the reflection from the second antenna of the other wireless terminal to the first antenna via the reflection on the predetermined surface. By using the transmitted indirect wave, the distance between the wireless terminals can be measured with a simple configuration and at a low cost.

  A distance measuring method according to a third invention is a distance measuring method for measuring a distance between a plurality of wireless terminals, and a plurality of radio waves are transmitted from a first antenna provided in one wireless terminal among the plurality of wireless terminals. Transmitting to the other wireless terminal among the wireless terminals, and directly receiving the radio wave transmitted from the one wireless terminal through the second antenna provided in the other wireless terminal as a direct wave and from the one wireless terminal Receiving a radio wave transmitted and reflected by a predetermined surface as an indirect wave through a second antenna; detecting a delay time from reception of a direct wave to reception of an indirect wave; The first antenna of one radio terminal and the second antenna of another radio terminal based on the height of the first antenna from the plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave With It is obtained by a step of calculating the distance.

  In the distance measurement method according to the present invention, radio waves are transmitted from a first antenna provided in one wireless terminal among the plurality of wireless terminals to another wireless terminal among the plurality of wireless terminals. A radio wave transmitted from one radio terminal is directly received as a direct wave through a second antenna provided in another radio terminal, and a radio wave transmitted from one radio terminal and reflected on a predetermined surface is used as an indirect wave. Received through the second antenna. A delay time from reception of the direct wave to reception of the indirect wave is detected. Based on the detected delay time, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, the first antenna of one radio terminal and another radio A distance between the terminal and the second antenna is calculated.

  In this way, the direct wave transmitted directly from the first antenna of one wireless terminal to the second antenna of the other wireless terminal and the reflection on the predetermined surface from the first antenna of the one wireless terminal By using the indirect wave transmitted to the second antenna of another wireless terminal, it becomes possible to measure the distance between the wireless terminals with a simple configuration and at a low cost.

  A distance measurement system according to a fourth invention is a distance measurement system for measuring a distance between a plurality of wireless terminals in an ad hoc network, wherein a first antenna provided in one wireless terminal among the plurality of wireless terminals is provided. A transmission means for transmitting radio waves from a first antenna to another wireless terminal among the plurality of wireless terminals, and a second antenna provided in the other wireless terminal, and transmitted from one wireless terminal. Receiving means for directly receiving the received radio wave as a direct wave through the second antenna and receiving the radio wave transmitted from one wireless terminal and reflected by a predetermined surface as an indirect wave through the second antenna, and a direct wave by the receiving means Detecting means for detecting a delay time from the reception of the indirect wave by the receiving means, the delay time detected by the detecting means, the height of the first antenna from the predetermined plane, Calculation means for calculating a distance between the first antenna of one radio terminal and the second antenna of another radio terminal based on the height of the second antenna from the surface and the propagation speed of the radio wave It is a thing.

  In the distance measurement system according to the present invention, radio waves are transmitted from the first antenna provided in one of the plurality of wireless terminals to the other wireless terminal among the plurality of wireless terminals by the transmission means. A radio wave transmitted from one wireless terminal is directly received by a receiving means through a second antenna provided in another wireless terminal as a direct wave, and a radio wave transmitted from one wireless terminal and reflected on a predetermined surface is received. The indirect wave is received by the receiving means through the second antenna. The delay time from the reception of the direct wave by the receiving means to the reception of the indirect wave by the receiving means is detected by the detecting means. Based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, the first of the one wireless terminal is calculated by the calculation means. The distance between the other antenna and the second antenna of the other wireless terminal is calculated.

  In this way, the direct wave transmitted directly from the first antenna of one wireless terminal to the second antenna of the other wireless terminal in the ad hoc network and the reflection on the predetermined surface from the first antenna of the one wireless terminal. By using the indirect wave that is transmitted to the second antenna of the other wireless terminal via the route, the distance between the wireless terminals in the ad hoc network can be measured with a simple configuration and at a low cost.

  According to the present invention, a direct wave transmitted directly from one wireless terminal to another wireless terminal and an indirect wave transmitted from one wireless terminal to another wireless terminal via reflection on a predetermined surface are used. Accordingly, it is possible to measure the distance between the wireless terminals with a simple configuration and at a low cost.

  FIG. 1 is a block diagram showing a configuration of a wireless ad hoc network to which a distance measurement system according to an embodiment of the present invention is applied.

  The wireless ad hoc network in FIG. 1 includes a plurality of mobile terminals 100a to 100f. Here, the mobile terminals 100a to 100f are, for example, in-vehicle wireless devices mounted on vehicles such as automobiles moving on the road surface.

  Each of the mobile terminals 100a to 100f includes a communication device that will be described later, and an antenna that transmits and receives radio waves. The antenna may be an omnidirectional antenna or a variable beam antenna that can change the direction of the main beam. As the variable beam antenna, for example, an electronically controlled waveguide described in “Research Technical Report of IEICE, published by IEICE, AP99-61, SAT99-61, pp. 9-14, July 1999” An antenna can be used. Each of the mobile terminals 100a to 100f also has a relay station function in addition to a signal transmission / reception function, and functions as a router.

  In the example of FIG. 1, when communication is performed between two mobile terminals 100a and 100f, multi-hop communication using other mobile terminals 100b, 100c, 100d, and 100e as relay stations is performed. As a result, even when radio waves do not reach between the two mobile terminals 100a and 100f, communication is possible via the other mobile terminals 100b, 100c, 100d, and 100e.

  In this case, in order to select a multi-hop communication path, it is necessary to know the positions of the plurality of mobile terminals 100a to 100f constituting the wireless ad hoc network. For this purpose, each of the mobile terminals 100a to 100f must know the distance and direction to the plurality of other mobile terminals 100a to 100f that are constantly moving.

  The communication devices of the mobile terminals 100a to 100f have a distance measurement function and a direction measurement function. The distance measurement function will be described later. A known method is used for the direction measuring function.

  FIG. 2 is a block diagram showing a configuration of a communication apparatus according to an embodiment of the present invention.

  In the present embodiment, the communication device 1 in FIG. 2 provided in one mobile terminal and the communication device 1 in FIG. 2 provided in another mobile terminal constitute a distance measurement system.

  2 includes a high frequency unit 10, a data processing unit 20, and a determination unit 30.

  The high frequency unit 10 includes an antenna 11, a switch 12, an RF (high frequency) amplifier circuit 13 and an IF (intermediate frequency) amplifier circuit 14. The data processing unit 20 includes a rake / demodulator 21, a filter / modulator 22, and an interface 23. The determination unit 30 includes an encryption processing circuit 31 and a data processing circuit 32. The encryption processing circuit 31 and the data processing circuit 32 include a CPU (Central Processing Unit), a memory, and the like, and calculate a distance by a distance measurement method described later according to a program stored in advance.

  The switch 12 of the high frequency unit 10 switches between a transmission operation and a reception operation. The RF amplifier circuit 13 includes a transmission amplifier circuit and a reception amplifier circuit. The IF amplifier circuit 14 includes a transmission amplifier circuit and a reception amplifier circuit.

  At the time of transmission, the data processing circuit 32 of the determination unit 30 generates data to be transmitted and performs encryption processing on the data generated using the encryption processing circuit 31. The encrypted data is provided as a signal wave to the filter / modulator 22 via the interface 23 of the data processing unit 20.

  The filter / modulator 22 includes a bandpass filter and a modulator. The filter / modulator 22 obtains a modulated wave by modulating a carrier wave with a signal wave supplied from the interface 23, and passes a component of a predetermined frequency band of the modulated wave.

  The transmission amplifier circuit of the IF amplifier circuit 14 of the high frequency unit 10 upconverts the modulated wave output from the filter / modulator 22 to obtain an intermediate frequency signal and amplify the intermediate frequency signal. The transmission amplifier circuit of the RF amplifier circuit 13 obtains a high frequency signal by up-converting the intermediate frequency signal output from the IF amplifier circuit 14 and amplifies the high frequency signal.

  The switch 12 transmits a high-frequency signal output from the transmission amplifier circuit of the RF amplifier circuit 13 from the antenna 11 as a radio wave.

  At the time of reception, the switch 12 of the high frequency unit 10 applies the radio wave received by the antenna 11 to the reception amplifier circuit of the RF amplifier circuit 13 as a high frequency signal. The receiving amplifier circuit of the RF amplifier circuit 13 obtains an intermediate frequency signal by amplifying the high-frequency signal given from the switch 12 and down-converting it. The reception amplifier circuit of the IF amplifier circuit 14 obtains a low frequency signal by amplifying and down-converting the intermediate frequency signal output from the reception amplifier circuit of the RF amplifier circuit 13.

  The rake / demodulator 21 includes a rake receiver and a demodulator. The rake / demodulator 21 obtains a plurality of time-dispersed signal waves by demodulating the low-frequency signal output from the reception amplifier circuit of the IF amplifier circuit 14 and also the time-dispersed signal waves. A plurality of signal waves are synthesized by matching the phase and time. The rake / demodulator 21 obtains a time difference (delay time) between a plurality of signal waves dispersed in time.

  The signal wave synthesized by the rake / demodulator 21 is given as data to the data processing circuit 32 of the determination unit 30 via the interface 23. The data processing circuit 32 extracts a desired signal wave from the signal waves sequentially supplied from the interface 23 using the encryption processing circuit 31. The schematic configuration and operation of the rake receiver of the rake / demodulator 21 will be described later.

  FIG. 3 is a diagram showing the configuration and operation of the rake receiver in the rake / demodulator 21 of FIG. FIG. 3A shows an example of the waveform of a signal wave input to the rake receiver in the rake / demodulator 21, and FIG. 3B shows a schematic configuration of the rake receiver in the rake / demodulator 21. .

  As illustrated in FIG. 3B, the rake receiver 200 includes a plurality of delay elements 210 to 215, a combining unit 220, a plurality of level detectors 230 to 235, and a delay detector 240.

  The plurality of delay elements 210 to 215 are connected in series in a plurality of stages. A plurality of signal waves S0 to S5 dispersed in time are input to the first-stage delay element 210 in time order. In the example of FIG. 3A, the levels of two signal waves S2 and signal wave S5 out of the plurality of signal waves S0 to S5 dispersed in time exceed a predetermined threshold value TH.

  The plurality of input signal waves S0 to S5 are sequentially shifted to the plurality of delay elements 210 to 215. The combining unit 220 combines the plurality of signal waves S5 to S0 by matching the phases and times of the plurality of signal waves S5 to S0 output from the plurality of delay elements 210 to 215, and outputs the combined signal wave SC. .

  Further, the plurality of level detectors 230 to 235 determine whether or not the levels of the signal waves S5 to S0 output from the delay elements 210 to 215 respectively exceed a predetermined threshold value TH, and the determination result Is output. The delay detector 240 detects a time difference (delay time) between signal waves exceeding the threshold value TH based on the determination results output from the plurality of level detectors 230 to 235.

  In the example of FIG. 3A, since the level of the signal wave S2 output from the delay element 213 and the level of the signal wave S5 output from the delay element 210 exceed the threshold value TH, the delay detector 240 is The time difference between the signal wave S2 output from the delay element 213 and the signal wave S5 output from the delay element 210 is detected, and the detected time difference is output as a delay time ΔT.

  FIG. 4 is a diagram for explaining a distance measuring method in the distance measuring system according to the present embodiment.

  In FIG. 4, in order to distinguish the antenna 11 of the communication device 1 in one mobile terminal and the antenna 11 of the communication device 1 in another mobile terminal, the antenna 11 of one mobile terminal is denoted by reference numeral 11A. Reference numeral 11B is given to the antenna 11 of the mobile terminal.

  Here, the height from the road surface 300 to the power transmission / reception unit of the antenna 11A is h1, and the height from the road surface 300 to the power transmission / reception unit of the antenna 11B is h2. In this example, the mobile terminal is an in-vehicle wireless device, and each mobile terminal is installed in an automobile. Therefore, the height h1 of the antenna 11A and the height h2 of the antenna 11B are known.

Also, let d be the distance in the horizontal plane between the antenna 11A of one mobile terminal and the antenna 11B of another mobile terminal. Further, the propagation distance of a radio wave (hereinafter referred to as a direct wave) transmitted from the antenna 11A of one mobile terminal and directly received by the antenna 11B of the other mobile terminal is denoted by r _d, and the antenna 11A of the one mobile terminal Let _{r r be} the propagation distance of a radio wave (hereinafter referred to as an indirect wave) transmitted and reflected by the road surface and received by the antenna 11 of another mobile terminal.

In this case, the propagation distance r _d of the direct wave is expressed by the following equation.

The propagation distance r _r of the indirect wave is expressed by the following equation.

Furthermore, the time from when the direct wave is transmitted from the antenna 11A of one mobile terminal until the direct wave is received by the antenna 11B of another mobile terminal (hereinafter referred to as the direct wave propagation time) is _denoted by T _{rd. Let} T _rr be the time from when the indirect wave is transmitted from the antenna 11A of one mobile terminal until it is received by the antenna 11B of another mobile terminal (hereinafter referred to as indirect wave propagation time). The difference between the direct wave delay time T _rd and the indirect wave propagation time T _rr (hereinafter referred to as the delay time) is expressed by the following equation.

Here, c is the propagation speed of radio waves and is 3 × 10 ⁸ [m / sec].

  From the above equations (1), (2) and (3), the following equation is established.

  In the above equation (4), the height h1 of the antenna 11A of one mobile terminal, the height h2 of the antenna 11B of the other mobile terminal, and the propagation speed c of the radio wave are known, so by detecting the delay time ΔT The distance d from the antenna 11A of one mobile terminal to the antenna 11B of another mobile terminal can be calculated.

  In addition, it has already been proved as a two-wave model that the received power due to the above-described linear wave and indirect wave shows a peak in communication between mobile terminals on the road surface.

  In the distance measurement system according to the present embodiment, when the communication device 1 of one mobile terminal transmits a radio wave to the communication device 1 of another mobile terminal, the communication device 1 of the other mobile terminal uses the direct wave and the indirect wave. Can be received. In the communication device 1 of FIG. 2, the rake receiver 200 of the rake / demodulator 21 can detect the delay time ΔT from the time of receiving the direct wave to the time of receiving the indirect wave. In the example of FIG. 3, the signal wave S2 corresponds to a direct wave, and the signal wave S5 corresponds to an indirect wave. In this case, the delay detector 240 of the rake receiver 200 detects the delay time between the signal wave S2 and the signal wave S5 as the delay time ΔT between the direct wave and the indirect wave.

  As described above, in the distance measurement system according to the present embodiment, radio waves are transmitted from the communication device 1 provided in one mobile terminal to another mobile terminal. A direct wave and an indirect wave transmitted from one mobile terminal are received by the communication device 1 provided in another mobile terminal, and a delay time ΔT between the direct wave and the indirect wave is detected. Further, based on the detected delay time ΔT, the height h1 of the antenna 11A of one mobile terminal, the height h2 of the antenna 11B of another mobile terminal, and the propagation velocity c of the radio wave, one mobile terminal from Equation (4) A distance d between the mobile terminal and another mobile terminal is calculated.

  As described above, the direct wave transmitted directly from the antenna 11A of one mobile terminal to the antenna 11B of the other mobile terminal and the reflection of the other mobile terminal from the antenna 11A of the one mobile terminal via the road surface 300 are transmitted. By using the indirect wave transmitted to 11B, it is possible to measure the distance between the mobile terminals with a simple configuration and at a low cost.

  Each mobile terminal measures the direction (azimuth angle) of the other mobile terminal together with the distance to the other mobile terminal by a known method, and sends the measured distance and direction to other mobile terminals as signal waves at regular intervals. Send. Thereby, each mobile terminal can grasp the positions of a plurality of mobile terminals constituting the wireless ad hoc network. Therefore, each mobile terminal can perform multi-hop communication using another mobile terminal as a relay station.

  Although the case has been described with the present embodiment where the mobile terminal is an in-vehicle wireless device, the mobile terminal may be another wireless terminal such as a mobile phone. Further, even when the wireless terminal is not a mobile terminal but a fixed terminal, the distance to other wireless terminals can be measured by using the communication device 1 of FIG.

  In the present embodiment, the antenna 11 corresponds to the first and second antennas, the high frequency unit 10 and the data processing unit 20 correspond to the transmission unit and the reception unit, the rake / demodulator 21 corresponds to the detection unit, The data processing circuit 32 corresponds to calculation means, and the road surface corresponds to a predetermined surface.

  The present invention can be used to measure the distance between wireless terminals in a wireless ad hoc network or the like.

It is a block diagram which shows the structure of the radio | wireless ad hoc network to which the distance measurement system which concerns on embodiment of this invention is applied. It is a block diagram which shows the structure of the communication apparatus which concerns on one embodiment of this invention. It is a figure which shows the structure and operation | movement of the rake receiver in the rake / demodulator of FIG. It is a figure for demonstrating the distance measuring method in the distance measuring system which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Communication apparatus S2, S5 Signal wave 10 High frequency part 11, 11A, 11B Antenna 12 Switch 13 RF (high frequency) amplifier circuit 14 IF (intermediate frequency) amplifier circuit 20 Data processing part 21 Rake / demodulator 22 Filter / modulator 23 Interface 30 Discriminating Unit 31 Encryption Processing Circuit 32 Data Processing Circuit 100a, 100b, 100c, 100d, 100e, 100f Mobile Terminal 200 Rake Receiver 210, 211, 212, 213, 214, 215 Delay Element 220 Combining Unit 230, 231, 232 , 233, 234, 235 Level detector 240 Delay detector 300 Road surface

Claims (6)

A distance measurement system for measuring a distance between a plurality of wireless terminals,
A transmission unit that has a first antenna provided in one of the plurality of wireless terminals, and that transmits a radio wave from the first antenna to another wireless terminal of the plurality of wireless terminals;
A second antenna provided in the other wireless terminal; and a radio wave transmitted from the one wireless terminal is directly received as a direct wave through the second antenna and transmitted from the one wireless terminal. Receiving means for receiving, as an indirect wave, a radio wave reflected by a predetermined surface through the second antenna;
Detecting means for detecting a delay time from reception of a direct wave by the receiving means to reception of an indirect wave by the receiving means;
Based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, A distance measuring system comprising: a calculating means for calculating a distance between the first antenna and the second antenna of the other wireless terminal. The calculating means sets the delay time detected by the detecting means to ΔT, the height of the first antenna from the predetermined plane as h1, and the height of the second antenna from the road surface as h2. When the propagation speed of radio waves is c,

The distance measurement system according to claim 1, wherein a distance d between the first antenna of the one wireless terminal and the second antenna of the other wireless terminal is calculated. The distance measuring system according to claim 1, wherein the plurality of wireless terminals are mobile terminals provided on a moving body that moves on the predetermined plane. A communication device provided in one wireless terminal having a first antenna and receiving radio waves transmitted from another wireless terminal having a second antenna,
The first antenna receives a radio wave transmitted from the other radio terminal directly as a direct wave through the first antenna and transmits a radio wave transmitted from the other radio terminal and reflected by the predetermined surface as an indirect wave. Receiving means for receiving through,
Detecting means for detecting a delay time from reception of a direct wave by the receiving means to reception of an indirect wave by the receiving means;
The one wireless terminal based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave A communication device comprising: a calculating means for calculating a distance between the first antenna of the second wireless communication terminal and the second antenna of the other wireless terminal. A distance measurement method for measuring a distance between a plurality of wireless terminals,
Transmitting radio waves from a first antenna provided in one of the plurality of wireless terminals to another wireless terminal of the plurality of wireless terminals;
A radio wave transmitted from the one wireless terminal is directly received as a direct wave through a second antenna provided in the other wireless terminal, and a radio wave transmitted from the one wireless terminal and reflected by a predetermined surface is indirectly received. Receiving as a wave through the second antenna;
Detecting a delay time from reception of the direct wave to reception of the indirect wave;
Based on the detected delay time, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave, the first of the one wireless terminal A distance measuring method comprising: calculating a distance between one antenna and the second antenna of the other wireless terminal. A distance measurement system for measuring a distance between a plurality of wireless terminals in an ad hoc network,
A transmission unit that has a first antenna provided in one of the plurality of wireless terminals, and that transmits a radio wave from the first antenna to another wireless terminal of the plurality of wireless terminals;
A second antenna provided in the other wireless terminal; and a radio wave transmitted from the one wireless terminal is directly received as a direct wave through the second antenna and transmitted from the one wireless terminal. Receiving means for receiving, as an indirect wave, a radio wave reflected by a predetermined surface through the second antenna;
Detecting means for detecting a delay time from reception of a direct wave by the receiving means to reception of an indirect wave by the receiving means;
Based on the delay time detected by the detection means, the height of the first antenna from the predetermined plane, the height of the second antenna from the predetermined plane, and the propagation speed of the radio wave A distance measuring system comprising: a calculating unit that calculates a distance between the first antenna of a wireless terminal and the second antenna of the other wireless terminal.

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