KR100926292B1 - Distance estimation method between two sensor nodes using round trip time delay - Google Patents

Abstract

The present invention proposes a new method based on a bidirectional round trip technique as a method for measuring the distance between wireless nodes. The main object of the present invention is to propose a method for correcting hardware delay occurring inside a node, which is the biggest problem in the bidirectional scheme, and to calculate a transmission / reception delay time according to an error-free physical distance. The configuration of the present invention is divided into an algorithm that calculates a physical delay by measuring the time of a signal arriving at the quasi-mobile node and quasi-reference node and the quasi-mobile node and quasi-reference node installed next to the mobile node and the reference node. Since the present invention is directly used for precise distance determination between two sensor nodes indoors, the application field can be referred to as indoor robot driving and positioning of objects for various purposes.

Wireless sensor network, distance estimation, indoor localization system, round trip (two-way communication), time delay

Description

Distance estimation method using two-way radio propagation travel time {Distance estimation method between two sensor nodes using round trip time delay}

The present invention relates to a distance measuring method using a two-way radio propagation time, and more particularly, to measure the delay time occurring within a node of these radio waves when there is radio wave transmission and reception between two sensor nodes in a wireless sensor network environment. The present invention relates to a distance measurement method using two-way radio propagation travel time, which calculates a travel time by measuring only a delay time occurring at an actual physical distance by providing a method.

The present invention is derived from the research conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Promotion. [Task Management Number: 2005-S-092-02, Title: USN-based Ubiquitous Robotic Space Technology Development].

The time it takes for the actual radio wave to be transmitted and received includes hardware delays inside the sensor node, signal processing delays, data link delays, and time delays due to actual physical movement. Therefore, in order to measure the transmission and reception time of the radio wave due to the actual physical distance movement, it is necessary to correct the delay time occurring inside the sensor node such as hardware delay, signal processing delay, and data link delay.

Since the measured physical delay time can be used to calculate the distance between two nodes, it can be directly used to determine the location of an object indoors or in a place where a wireless sensor node is installed. Therefore, the background technology to which the present invention belongs may be referred to as a wireless sensor network, location measurement of objects, signal processing, and the like. Specifically, the present invention proposes a method for calculating a propagation time of a signal by two-way (round trip) radio transmission and reception, and thus, a detailed technique may be referred to as a measurement of distance using Round-Trip Time (RTT). Related papers include McCrady, D. D; Doyle, L .; Forstrom, H .; Dempsey, T .; Martorana, M, “Mobile Ranging Using Low Accuracy Clocks”, IEEE Transactions on Microwave Theory and Techniques, Vol. 48, No. 6, June 2000, pp.951-958 introduces RTT related technology, but does not suggest a method for correcting the internal delay time occurring inside the sensor node by placing two sensors proposed in the present invention at a short distance.

On the other hand, triangulation (triangulation) is widely used to measure the position of an object using a wireless sensor network. In the position measurement system using triangulation method, the time of arrival of the signal (Time Of Arrival) or the time difference of arrival (Time Difference Of Arrival) is widely used as a method of measuring position. However, although TOA and TDOA show excellent performance, they have a very difficult problem of time synchronization between a mobile node and a reference node. As a method for solving the time synchronization problem, a method using the Round-Trip Time (RTT) using the difference between the start and return time of the propagation time by bidirectional communication that does not require time synchronization as described in the above paper is an alternative. It is used as.

However, because RTT is not widely used when measuring distances in the existing positioning system, a large time delay is generated in the system when measuring the time that the mobile node and the reference node exchange packets to measure the RTT. Because it occurs. That is, since it is difficult to accurately measure hardware and software time delays, time delays caused by spatial propagation of signals cannot be measured purely. Delays in the system include hardware pass-through time, signal processing time, antenna transmit / receive time, data link time, etc. It is not practical to calculate this system delay time and there is no suitable equipment to measure it. have.

Meanwhile, although US Patent No. 7054226, a prior patent, proposes a method for measuring distance using a total delay time of a sound wave signal reflected after transmitting sound waves, it does not present a concept of distance measurement using a wireless sensor network. . Therefore, there is a need for more accurate distance measurement through the physical distance measuring method between two sensor nodes that compensates for the internal delay time of sensor nodes generated during round trip, or two-way communication in wireless sensor network environment. .

The present invention has been proposed to meet the above-mentioned necessity and to solve the above-mentioned problems, and an object thereof is to provide an internal sensor node generated during a round trip or two-way communication process in a wireless sensor network environment. The present invention provides a distance measuring method using a bidirectional radio propagation movement time between a reference node and a mobile node whose delay time is corrected.

Accordingly, the distance measuring method using the bidirectional radio propagation movement time for achieving the object of the present invention is composed of a reference node and a mobile node, the distance measurement method using the bidirectional radio propagation movement time, the first quasi-reference node is a mobile node. A first step of transmitting a packet to the mobile node and the first quasi-reference node, and a reference signal to the reference node and the first node in response to the packet received by the mobile node. And a second transmission step of transmitting to the quasi-reference node, and a calculation step of obtaining an eRTT value indicating a delay time according to the physical distance.

In addition, the distance measurement method using the bidirectional radio propagation movement time of the present invention is a distance measurement method using a bidirectional radio propagation movement time composed of a reference node and a mobile node, the second quasi-reference node is provided adjacent to the reference node A first transmission step in which the reference node transmits packets to the mobile node and the second quasi-reference node, and the mobile node transmits an acknowledgment signal to the reference node and the second quasi-reference node in response to the received packet. The second transmission step and a calculation step for obtaining the eRTT value representing the delay time by the physical distance.

In addition, the distance measurement method using the two-way radio wave propagation time of the present invention comprises a reference node and a mobile node, the distance measurement method using the two-way radio wave propagation time, the first quasi-reference node is provided adjacent to the mobile node The installation step of installing the second quasi-reference node adjacent to the reference node, and the removal of the internal delay is the first transmission step in which the reference node transmits packets to the mobile node, the first quasi-reference node and the second quasi-reference node, respectively. And a second transmission step of transmitting an acknowledgment signal to the reference node, the first quasi-reference node, and the second quasi-reference node in response to the received packet, and obtaining an eRTT value indicating the delay time according to the physical distance. It is characterized by consisting of a calculation step.

In the present invention, two quasi-reference nodes are installed to measure the actual physical distance between two nodes by two-way communication of radio waves, which can be directly used for measuring distances between nodes in a room. It is effective to accurately measure.

In addition, the present invention has an effect that can be widely used in robot navigation, office automation, construction, wireless communication services, etc. for location recognition of objects using radio waves of an indoor space or a wireless sensor network.

Hereinafter, with reference to the accompanying drawings will be described in more detail with respect to the configuration of the present invention.

1 is a block diagram illustrating a process of transmitting and receiving data between a reference node and a mobile node according to an embodiment of the present invention.

Referring to FIG. 1, first, N ₁ , the node on the left side, is set as a reference node, and N ₂ , the node on the right side, is described as a mobile node, and the distance between two nodes is d. The time taken to move the distance is set as ΔT _D = ΔT _D ′.

The reference node N ₁ transmits a radio wave at time T ₁ , and the mobile node N ₂ receives the radio signal at time T ₂ , records the time, and sends an acknowledgment signal to T ₃ again. At time T ₄ , the reference node N ₁ receives the confirmation signal. In this process, the delay time in the reference node N ₁ is represented by ΔT _R and ΔT _R ′, respectively, and the delay time in the mobile node N ₂ is ΔT _M , T ₃ -T ₂ , respectively. And ΔT _M ′.

In order to measure the distance from the reference node (N ₁ ) to the mobile node (N ₂ ) using the delay time (RTT) by physical distance, the time markers obtained by the reference node (N ₁ ) are timestamp T ₁ and T ₄ . Then, when RTT ', which is the total time delay including the time delay occurring inside the node, is represented by Equation 1 below, and the delay time by physical distance is represented by RTT, Equations 1 and 2, which represent RTT' and RTT, respectively, respectively. It is represented as follows.

RTT '= T ₄ -T ₁

RTT = ΔT _D + ΔT _D ′

Then, the distance d 'and the physical distance d, including the delay inside the node, may be represented as follows in Equations 3 and 4, respectively.

d ′ = cRTT ′ / 2

d = cRTT / 2

Here, the c value shown in Equations 3 and 4 represents the speed of light. However, the RTT ′ value obtained in Equation 1 is significantly different from RTT, which is a time taken for a signal to actually move a distance between two nodes. This is because there is a delay between the time when the packet is sent from the system of each node, the time when the signal is actually sent by the antenna, the time when the packet is received by the system, and the time when the signal is received by the antenna.

In FIG. 1, the internal delays of the reference node N ₁ and the mobile node N ₂ are respectively represented by ΔT _R , ΔT _R ′ and ΔT _M , T ₃ -T ₂ , ΔT _M ′, respectively. Since the times are generally much larger in the room than the time at which the signal travels (ΔT _D , ΔT _D ′), the accuracy of the measurement distance d ′ including the time delay is very low.

In other words, the total time delay is T ₄ T ₁ = ΔT _R + ΔT _D + ΔT _M + T ₃ -T ₂ + ΔT _M ′ + ΔT _D ′ + ΔT _R ′ and the internal delay is usually much larger than the delay due to physical distance. Expressed in mathematical form, ΔT _R + ΔT _R ′ + ΔT _M + T ₃ -T ₂ + ΔT _M ′ >> ΔT _D It can be expressed by the relationship of + ΔT _D ′. 2 is a device configuration diagram illustrating a configuration of a reference node, a mobile node, and a quasi-reference node installed in proximity to the mobile node according to an embodiment of the present invention.

Referring to FIG. 2, a first semi-reference node, which is a node in charge of internal delay measurement, is added to accurately measure internal delay occurring in the mobile node N ₂ , which is a position measurement object. . For convenience, the added node installed in proximity to the mobile node N ₂ is referred to as a first quasi-reference node N ₃ . In this case, the first quasi-reference node N ₃ is positioned to be very close to the mobile node N ₂ as compared to the reference node N _{1 to be} measured.

At this time, as shown in Figure 2, the packet sent by the reference node (N ₁ ) will be delivered to the mobile node (N ₂ ) and the first quasi-reference node (N ₃ ), respectively, the mobile node (N ₂ ) and the first quasi Since the reference nodes (N ₃ ) are located very close to each other, it is assumed that the time taken for transmission is about the same. Accordingly, it can be represented by Equation 5 according to the assumption that there is no distance difference between the reference node N ₁ and the first quasi-reference node N ₃ as shown in FIG. 2.

d d″

dd ″

Where d ″ is the pure physical distance between the reference node N ₁ and the first quasi-reference node N ₃ . Therefore, forward packets between the mobile node (N ₂₎ and the first semi-reference node (N _3), between the distance difference is almost no reference node (N ₁₎ the mobile node (N ₂₎ and given a reference node (N ₃₎ from Assuming that the time it takes to be almost the same, it can be expressed as shown in Equation 6.

ΔT_D ΔT_D″

ΔT _D ΔT _D ″

Here, ΔT _D ″ represents a time taken for a packet to move from the reference node N ₁ to the first quasi reference node N ₃ .

3 is a block diagram illustrating a state in which radio waves are transmitted from a mobile node to a quasi-reference node according to an embodiment of the present invention.

Under the assumption of Equations 5 and 6, the mobile node N ₂ transmits an acknowledgment signal in response to the received packet. In this case, the confirmation signal transmitted from the mobile node N ₂ is transmitted to both the reference node N ₁ and the first quasi-reference node N ₃ . In this case, the time taken to be transmitted from the mobile node N ₂ to the first quasi-reference node N ₃ is defined as ΔT _MSR1 , and the time delay in the first quasi-reference node N ₃ is ΔT. _It is defined as _M.

Meanwhile, the delays ΔT _R , ΔT _R ′, ΔT _M , ΔT _M ′, which occur in hardware among internal delays at the reference node N ₁ , the mobile node N ₂ , and the first quasi-reference node N ₃ . Looking at the variance of ΔT _SR1 , ΔT _SR1 ′), the variance of the delay that occurs when a signal passes through the wireless equipment at the node is a Gaussian Random Variable, which is the sum of the random variables, or the sum of the delays, respectively. If it is represented by Equation 7, it may be expressed as Equation 7 below.

σ _RTT ² = σ _RN ² + σ _MN ²

In Equation 7, σ _RTT ² , σ _RN ² , and σ _MN ² are the variance of the delay of RTT, the variance of the internal delay T ₁ of the reference node N ₁ , and the internal delay T of the mobile node N _2, respectively. ₃ ) dispersion.

Meanwhile, references (McCrady, D. D; Doyle, L .; Forstrom, H .; Dempsey, T .; Martorana, M, "Mobile Ranging Using Low Accuracy Clocks", IEEE Transactions on Microwave Theory and Techniques, Vol. 48 , No. 6, June 2000, pp.951-958), it can be seen that the actual dispersion values obtained through experiments are very small to be ignored as follows.

σ _RN ² = 0.3675ⅹ10 ^-18 seconds

σ _MN ² = 0.3675ⅹ10 ^-18 + σ _cf ² (σ _cf ² = 0.25ⅹ10 ^-18 ) seconds

σ _RTT = ± 0.9ns

Therefore, it may be reasonable to assume that the delay occurring in hardware among the node internal delays assumed in the present invention is almost fixed. Under this assumption, the internal delay time of the mobile node can be estimated in the following way. The first quasi-reference node N ₃ receives radio waves from the reference node N1 at T ₅ hours, records the time, and then again transmits the first quasi-reference node N ₃ from the mobile node N ₂ . Receive at T ₆ hours. Therefore, eDelayMob indicating the internal delay of the mobile node N2 may be represented by T ₆ -T ₅ . On the other hand, when we define eDelayMob as T ₆ -T ₅ , we can get the following relations.

eDelayMob = T ₃ + ΔT _M ′ + ΔT _MSR1 + ΔT _SR1 ′-(T ₁ + ΔT _R + ΔT _D ″ + ΔT _SR1 )

= T ₃ + ΔT _M ′ + ΔT _{MSR 1} − (T ₁ + ΔT _R + ΔT _D ″)

ΔT_M′, ΔT_R

ΔT_R′, ΔT_MSR1

0 (또는 두 노드(이동노드(N₂)와 준기준노드(N₃)) 사이의 거리에서 직접 값을 얻어낼 수도 있다). 이러한 경우 더 실제에 가까운 물리적 거리에 의한 지연시간을 나타내는 eRTT값을 다음의 수학식 9와 같이 표현할 수 있다. Here, we use the eDelayMob inferred and we want to calculate a more realistic RTT value. On the other hand, a more realistic RTT value will be defined as eRTT. In this case, it is assumed that the mobile node N ₂ is hardly moved and the internal delay occurring at the reference node N ₁ is almost constant. ΔT _M

ΔT _M ′, ΔT _R

ΔT _R ′, ΔT _MSR1

0 (or you can get the value directly from the distance between two nodes (mobile node N ₂ and quasi-reference node N ₃ )). In this case, an eRTT value representing a delay time due to a more physical distance can be expressed as in Equation 9 below.

eRTT = T ₄ -T ₁ -eDelayMob

= T ₃ + ΔT _M ′ + ΔT _D ′ + ΔT _R ′-T ₁ -T ₃ -ΔT _M ′ _{-ΔT MSR1} + T ₁ + ΔT _R + ΔT _D ″

= ΔT _D ′ + ΔT _D ″ + ΔT _R ′ + ΔT _R -ΔT _MSR1

2ㆍΔT_D + 2ㆍΔT_R

2 · ΔT _D + 2 · ΔT _R

Accordingly, it can be seen that by using eDelayMob, internal delays ΔT _M , T ₃ -T ₂ , ΔT _M ′ generated in the mobile node N ₂ can be eliminated. Subsequently, the quasi-reference node N ₄ may be added to the reference node N _{1 in} order to remove 2 · ΔT _R , which represents a delay occurring at the still remaining reference node N ₁ .

FIG. 4 is a block diagram illustrating a state in which another quasi-reference node is installed next to a reference node and a radio wave generated from the reference node is received according to another embodiment of the present invention, and FIG. 5 is according to another embodiment of the present invention. The device configuration diagram shows a state in which another quasi-reference node is installed next to the reference node and the radio wave generated from the mobile node is received.

Referring to FIGS. 4 and 5, FIGS. 4 and 5 show two quasi-reference nodes N ₃ and N ₄ installed close to the reference node N ₁ and the mobile node N ₂ , respectively. Shows. Here, the quasi-reference node N ₃ installed in proximity to the mobile node N ₂ is referred to as the first quasi-reference node, and the quasi-reference node N ₄ installed in proximity to the reference node N ₁ is referred to as the second quasi-reference node. This is called a node.

In this case, if the internal delay occurring at the reference node N ₁ is eDelayRef, eDelayRef may be represented by Equation 10 below.

eDelayRef = T ₄ -T _1- (T ₈ -T ₇ )

ΔT_D′

ΔT_D″

ΔT_D″′, ΔT_SR1

ΔT_SR1′, ΔT_{MS R1}

ΔT_MSR2 = 0 , ΔT_SR2 =ΔT_SR2′(또는 두 node 사이의 거리에서 직접 값을 얻어 낼 수도 있다)의 조건하에 우리는 최종적으로 기준 노드와 이동 노드에서의 내부 지연을 제거한 eRTT를 다음의 수학식 11에서 다음과 같은 계산식을 통해 구할 수 있다.ΔT _D

ΔT _D ′

ΔT _D ″

ΔT _D ″ ′, ΔT _SR1

ΔT _SR1 ′, ΔT _{MS R1}

Under the condition of ΔT _MSR2 = 0, ΔT _SR2 = ΔT _SR2 ′ (or we can get the value directly from the distance between two nodes), we finally compute the eRTT by removing the internal delay at the reference and mobile nodes. Equation 11 can be obtained from the following equation.

eRTT = T ₄ -T ₁ -eDelayMob-eDelayRef

= T ₄ -T _1- (T ₆ -T ₅ )-(T ₄ -T ₁ -T ₈ + T ₇ )

= T ₅ -T ₆ + T ₈ -T ₇

= T ₁ + ΔT _R + ΔT _D ″ + ΔT _SR1- (T ₃ + ΔT _M ′ + ΔT _MSR1 + ΔT _SR1 ′) + T ₃ + ΔT _M ′ + ΔT _D ″ ′ + ΔT _SR2 ′-(T ₁ + ΔT _R + ΔT _MSR2 + ΔT _SR2 )

= ΔT _D ″ + ΔT _SR1 -ΔT _MSR1 ΔT _SR1 ′ + ΔT _D ″ ′ + ΔT _SR2 ′ _{-ΔT MSR2} ΔT _SR2

ΔT_D″- ΔT_MSR1 + ΔT_D″′- ΔT_MSR2

ΔT _D ″ _{-ΔT MSR1} + ΔT _D ″ ′ _{-ΔT MSR2}

ΔT_D′+ ΔT_D″′

ΔT _D ′ + ΔT _D ″ ′

2ㆍΔT_D

2 · ΔT _D

After all, we can find out the RTT value more accurately by using eDelayMob and eDelayRef as above. That is, it can be seen that a more accurate RTT value can be obtained by installing the first quasi-reference node N ₃ and the second quasi-reference node N ₄ .

6 is a flowchart illustrating a distance measurement process using a bidirectional radio propagation time after installing a first quasi-reference node according to an embodiment of the present invention.

The first quasi-reference node N ₃ is installed adjacent to the mobile node N ₂ so as to eliminate an internal delay occurring in the mobile node N ₂ at the time of distance measurement (S202).

In order to remove an internal delay occurring in the mobile node N ₂ , the reference node N ₁ transmits a packet to the mobile node N ₂ and the first quasi-reference node N ₃ , respectively (S204). ).

The mobile node N ₂ transmits an acknowledgment signal to both the reference node N ₁ and the first quasi-reference node N _{3 in} response to the received packet (S206).

An eRTT value representing a delay time due to a physical distance close to an actual value is obtained using Equation 9 using ΔT _D and ΔT _R values (S208).

7 is a flowchart illustrating a distance measurement process using a bidirectional radio propagation time after installing a second quasi-reference node according to an embodiment of the present invention.

The second quasi-reference node N ₄ is installed adjacent to the reference node N ₁ to remove the internal delay occurring in the reference node N ₂ at the time of distance measurement (S302).

Said reference and sends each packet to the node (N ₁₎ is the basic node (N ₁₎ in order to remove the internal delay caused by the mobile node (N ₂₎ and the second quasi-reference node (N ₄₎ (S304 ).

The mobile node N ₂ transmits an acknowledgment signal to both the reference node N ₁ and the second quasi-reference node N _{4 in} response to the received packet (S306).

An eRTT value representing a delay time due to a physical distance close to the actual value is obtained using ΔT _D and ΔT _M values (S308).

8 is a flowchart illustrating a distance measurement process using a bidirectional radio propagation time after installing a first quasi-reference node and a second quasi-reference node according to an embodiment of the present invention.

Installed adjacent to the mobile node inside the delay occurring in the (N ₂₎ and a reference node (N ₂₎ the mobile node (N ₂₎ of the first quasi-reference node (N ₃₎ so as to remove the internal delay occurring in the time distance measurements The second quasi-reference node N ₄ is installed adjacent to the reference node N ₁ (S402).

To remove the internal delay, the reference node N ₁ transmits a packet to the mobile node N ₂ , the first quasi-reference node N ₃ , and the second quasi-reference node N ₄ , respectively. (S404).

The mobile node N ₂ transmits an acknowledgment signal to the reference node N ₁ , the first quasi-reference node N ₃ , and the second quasi-reference node N ₄ in response to the received packet. (S406).

An eRTT value representing a delay time due to a physical distance close to the actual value is obtained by using Equation 11 using ΔT _D value, which is a time taken for radio waves to travel between the reference node N1 and the mobile node N2 (S408). ).

1 is a block diagram illustrating a process of transmitting and receiving data between a reference node and a mobile node according to an embodiment of the present invention.

2 is a device configuration diagram showing the configuration of a reference node, a mobile node and a quasi-reference node installed in proximity to the mobile node according to an embodiment of the present invention.

3 is a block diagram illustrating a state in which radio waves are transmitted from a mobile node to a quasi-reference node according to an embodiment of the present invention.

4 is a block diagram illustrating a state in which another quasi-reference node is installed next to a reference node and a radio wave generated from the reference node is received according to another embodiment of the present invention.

5 is a block diagram illustrating an apparatus for installing another quasi-reference node next to a reference node and receiving radio waves generated from a mobile node according to another embodiment of the present invention.

6 is a flowchart illustrating a distance measurement process using a bidirectional radio propagation time after installing a first quasi-reference node according to an embodiment of the present invention.

7 is a flowchart illustrating a distance measurement process using a bidirectional radio propagation time after installing a second quasi-reference node according to an embodiment of the present invention.

8 is a flowchart illustrating a distance measurement process using the bidirectional radio propagation time after installing the first and second quasi-reference nodes according to an embodiment of the present invention.

Claims (6)

A distance measuring method using a two-way radio propagation time composed of a reference node and a mobile node, An installation step of installing a first quasi-reference node adjacent to the mobile node; A first transmission step of transmitting, by the reference node, a packet to the mobile node and the first quasi-reference node; A second transmission step of transmitting an acknowledgment signal to the reference node and the first quasi-reference node in response to the packet received by the mobile node; Subtract the time when the first quasi-reference node receives the radio wave from the mobile node from the time when the first quasi-reference node receives the radio wave from the reference node to remove the internal delay time generated in the mobile node, Comprising a step of calculating the delay time for the distance measurement method using a two-way radio wave propagation time characterized in that it comprises. The method of claim 1, The eRTT value representing the delay time with respect to the physical distance from which the internal delay time is removed from the mobile node is eRTT

2 · ΔT _D + 2 · ΔT _R ΔT _D is a time taken to move the distance between the reference node and the mobile node, and ΔT _R is a bidirectional radio propagation time, characterized in that it represents a delay required inside the reference node. Distance measurement method used. A distance measuring method using a two-way radio propagation time composed of a reference node and a mobile node, An installation step of installing a second quasi-reference node adjacent to the reference node; A first transmission step of transmitting, by the reference node, a packet to the mobile node and the second quasi-reference node, respectively; A second transmission step of transmitting a confirmation signal to the reference node and the second quasi-reference node in response to the received packet; Subtract the time when the reference node transmits the radio wave to the mobile node from the time when the reference node receives the confirmation signal from the mobile node, and subtract the time when the second quasi-reference node receives the radio wave from the mobile node. And calculating a delay time with respect to a physical distance by removing the internal delay time generated by the reference node by adding the time at which the second quasi-reference node receives the radio wave from the reference node. Distance measurement method using two-way radio propagation time. The method of claim 3, The eRTT value representing the delay time with respect to the physical distance from which the internal delay time is removed from the reference node is eRTT

2 · ΔT _D + 2 · ΔT _M ΔT _D is a time taken to move the distance between the reference node and the mobile node, and ΔT _M is a bidirectional radio propagation time, characterized in that it represents a delay required inside the mobile node. Distance measurement method used. A distance measuring method using a two-way radio propagation time composed of a reference node and a mobile node, An installation step of installing the first quasi-reference node adjacent to the mobile node and installing the second quasi-reference node adjacent to the reference node; A first transmission step of transmitting, by the reference node, a packet to the mobile node, the first quasi-reference node, and the second quasi-reference node; A second transmission step of transmitting a confirmation signal to the reference node, the first quasi-reference node, and the second quasi-reference node in response to the received packet; The time when the first quasi-reference node receives the radio wave from the reference node from the result of subtracting the time when the reference node transmits the radio wave to the mobile node from the time when the reference node receives the confirmation signal from the mobile node. Subtracts the result of subtracting the time when the first quasi-reference node receives the radio wave from the mobile node, and confirms the time when the reference node transmits the radio wave to the mobile node from the mobile node. Is subtracted from the received time, and subtracts the time when the second quasi-reference node receives the radio wave from the mobile node, and adds the time when the second quasi-reference node receives the radio wave from the reference node. A subtraction step of calculating an eRTT value representing a delay by physical distance. Distance measurement method using directional radio propagation time. The method of claim 5, An eRTT value representing a delay time with respect to the physical distance from which internal delay time is removed from the reference node and the mobile node is eRTT

2 · ΔT _D The ΔT _D is an approximate equation, and the ΔT _D represents a time taken to move the distance between the reference node and the mobile node.

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