KR20100094264A - System for estimating the distance between communication devices and method thereof - Google Patents

Abstract

PURPOSE: A system for estimating the distance between communication devices and a method thereof are provided to continuously measure the distance between mobile devices using only a function that a device itself has. CONSTITUTION: An input unit(31) is equipped in device B. The input unit receives an emitted sound file. A recognition unit(32) is equipped in device B. The recognition unit recognizes the inputted sound file. A distance calculating unit(33) is equipped in device A. The distance calculating unit calculates the distance between device A and device B based on a time difference between a time point of the emission and a time point of the recognition.

Description

System for estimating the distance between communication devices and method

The present invention relates to a distance measuring system and method thereof between communication devices, and more particularly to a system and method capable of continuously (continuously) accurately measuring a distance between communication devices, not intermittently. The present invention relates to a system and method for continuously measuring distances between communication devices using only functions (equipment) owned by the communication device itself without any additional equipment.

Distance measurement between communication devices may enable various applications of the device, such as screen sharing and location tracking through video between communication devices. In the distance measurement between devices, it is very important to measure only the basic functions of the device and to maintain the persistence of the measurement.

Although there is a method of using a GPS (Global Positioning System) as a conventional distance measuring method, GPS has a disadvantage in that it cannot operate properly indoors. Therefore, researches on distance measurement that can be performed indoors have been conducted, and research on distance measurement indoors mainly uses IEEE802.11 wireless LAN technology. However, because the technology basically uses the characteristics of radio frequency, accurate distance measurement is difficult. Many attempts have been made in the sensor network, and the use of special (separate) hardware for distance measurement can lead to price increases and limitations in the application of additional equipment.

On the other hand, a distance measuring method that uses a device-generated sound to measure distances relatively accurately has been introduced. This method, however, has the disadvantage of not being able to continuously measure distance and has a disadvantage in that it is very sensitive to effects such as reflections and echoes in the indoor environment.

The problem to be solved by the present invention is to provide a system and method that can continuously measure the distance between mobile devices using only the function (equipment) owned by the device itself without any additional equipment for distance measurement.

In order to solve the above problems, the distance measuring system disclosed herein includes a predetermined communication device that emits a sound file; An input unit provided in the communication device (the other device) to measure the distance to the predetermined communication device and receiving the emitted sound file; A recognition unit provided in the counterpart device and recognizing the input sound file; And a distance calculator which is provided in the predetermined communication device and calculates a distance between the two devices based on a time difference between the time of the emission and the time of the recognition.

In addition, the two communication devices check the sensitivity of the signal periodically transmitted and received to the AP (Access Point) linked to the self, if the deviation of the signal sensitivity between the time point of the check is initialized to initialize the distance measurement The present invention further includes a unit to solve the problems of the present invention.

In order to solve the above problems, the distance measuring method disclosed in the present specification is

(a) receiving a sound file emitted from a predetermined communication device by a distance measurement target communication device (an external device) with the predetermined communication device; (b) the counterpart device recognizing the input sound file; And (c) calculating, by the predetermined communication device, a distance between the two devices based on a time difference between the time of the emission and the time of the recognition.

(D) checking a sensitivity of a signal periodically transmitted / received by the predetermined communication device to an AP (Access Point) linked thereto; And (e) if the deviation of the signal sensitivity between the time point of the check is more than a predetermined value, further comprising the step of returning to the step (a) solves the problem of the present invention.

The present invention relates to the measurement of relative distances between communication devices, in particular mobile devices. The proliferation of mobile devices such as PDAs today enables a variety of applications. Distance measurement between devices enables a video sharing service between two mobile devices, etc. According to the present invention, distance measurement can be implemented very simply because the distance between devices is measured using only a function (equipment) of the device. In addition, the continuous distance measurement between the mobile devices according to the present invention will provide information for accurate positioning to various other positioning systems and will enable the dissemination of many location-based services.

Prior to the description of the specific contents of the present invention, for the convenience of understanding, an outline of a solution of the problem to be solved by the present invention is first presented.

In the present invention, the sound generated by the communication device is used for accurate distance measurement between devices using only basic functions (basic equipment) of the communication device. In particular, many mobile devices such as PDAs are basically equipped with speakers and microphones to support multimedia services. Since sound has a relatively slower transmission speed than WLAN frequency, measuring distance between mobile devices using sound enables relatively accurate measurement than measuring distance using wireless frequency.

In addition, in the present invention, by measuring the distance to reflect the movement (movement) of the device to ensure the persistence of the distance calculation between devices, to improve the accuracy of the distance calculation.

Hereinafter, the configuration of the invention for clarifying the solution to the problem to be solved by the present invention will be described in detail with reference to the accompanying drawings, based on the preferred embodiment of the present invention, to give a reference numeral to the components of the drawings In the drawings, like reference numerals refer to like elements even though they are on different drawings, and it is to be noted that components of other drawings may be cited when necessary in describing the drawings. In addition, when it is determined that the detailed description of the known function or configuration and other matters related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

We mentioned that there is an existing method that uses sound to measure the distance between mobile devices. This conventional method uses two different devices to output different sounds at different times, and record the relative sound using sampling information of the recorded data. Make a distance measurement.

1 is a view showing a conventional distance measuring method using sound.

In FIG. 1, it is assumed that each device A and B have a sound file to be output and a sound file of the other party and are currently in a recordable state. Device A outputs its own sound at a given time t _A0 . Device A records its sound at time t _A1 . Device B recognizes and records the sound that device A outputs at time t _A0 at time t _B0 .

Device B outputs its sound at time t _B1 after a specific time after device A outputs sound and records its sound at time t _B2 like device A. Device A recognizes and records the sound output by device B at time t _A2 .

The two devices perform cross-correlation to extract a time point at which their sound and the other party's sound are recorded. At this time, after each sound file and the other party's sound file are correlated, the time point at which each sound is recorded is calculated. The distance is measured using the calculated time and sound velocity.

In FIG. 1, d _{B, A} represents the actual linear distance from the device B to A and d _{A, B} represents the actual linear distance from the device A to B. d _{A, A} , d _{B, B} represent the distance between the devices A and B's own speakers and microphone, respectively. In the case of device B, its sound output time is t _B1, but the actual execution time of the command is performed at time t _B2 because of the processing time inside the device. Therefore, the effective linear distance from device B to A becomes d _{B, A} -d _{B, B.} The same applies to device A. In other words, in order to predict the internal processing time, the user records his sound and finds out when his sound is recorded.

Therefore _, the average of d _{B, A} + d _{A, B} is the relative distance between the devices A and B, and when it is expressed by the equation, it becomes as shown in FIG. When cross-correlation is applied to the recorded data, index information about the recorded point in memory is obtained. When the index information is divided using the sampling rate used during recording, The value is calculated.

However, the correlation technique in the conventional distance measurement method shown in FIG. 1 is inappropriate in an indoor environment, as shown in FIG. 2. 2 is a simulation result of the correlation technique in the indoor environment. In the case of Fig. 2, the actual recorded time point is 0.65, and the point where the degree of association between the sound file of the user and the opponent's sound file is the highest. However, the correlation method in the conventional distance measuring method may cause an error of calculating the point 1.3 at the actual recorded point. This is because duplicate sounds may be recorded depending on phenomena such as reflection and ringing, because this is not considered.

To solve this problem, the present invention uses weighted cross-correlation. Hereinafter, the operation of the present invention will be described in detail.

3 is a view showing a preferred configuration of the present invention, Figure 4 is a view showing a preferred flow of the present invention.

As shown in FIG. 3, the distance measuring system according to the present invention performs distance measurement between devices using only basic functions (basic equipment) of the communication device (mobile device) as mentioned above. Each of the components is distributed in a communication device (hereinafter, referred to as a "relative device" or device B) for measuring the distance between the predetermined communication device (device A) and device A. In other words, device A becomes the subject of distance measurement, and device B becomes an object of distance measurement.

At this time, such a relationship between the device A and the device B may of course be interchanged with each other, and therefore, each of the components 31, 32, 33, and 34 of FIG. 3 is provided in the devices A and B. FIG. 3 is only a diagram showing only a corresponding component in each device according to a main user's status of the device for convenience of description. That is, the devices A and B each have all the components 31, 32, 33, and 34 of FIG. 3, respectively, but only some of the components are operated or not depending on whether they are subjects or objects of distance measurement. The same applies to the following. The device A and the device B may be various types of communication devices, but may include a personal digital assistant (PDA).

First, device A emits a sound file through its speaker. The input unit 31 of the device B receives a sound file emitted from the device A (s41). The input unit 31 corresponds to a device capable of detecting a sound such as a microphone of the device B. At this time, if the time corresponding to the time of the emission is set to '0', the time at which the input starts is set to T _in . This means that the time interval from the time of release to the time of input is T _in .

The recognition unit 32 of the device B performs a function of recognizing the input sound file (S42). The meaning of the recognition unit 32 is that even if the sound file emitted from the device A starts inputting (reaching) the device B, the recognition of the input sound file detects that the processing time of the device B itself (the sound file emitted from the device A has been input). However, since the time taken internally by the device B) cannot occur at the same time as the input time, the time when device B actually recognizes the input sound file (T _recog ) is regarded as the arrival time of the sound file emitted from the device A. It is. At this time, the reference point of T _recog is T _in .

On the other hand, the recognition unit 32 recognizes the inputted sound file by correlating the sound file emitted from the device A with the sound file of the device B to calculate the point of greatest correlation. The point of greatest degree is the point T _recog actually recognized by the device B, and the calculation thereof is preferably performed as follows.

The recognition section 32 is a sound file and device B a voice file recognition (T _cc) to (B the recorded sound file) obtained by using a correlation technique (cross-correlation) mentioned above, with release from the device A And a recognition time T _amdf obtained using the Average-Magnitude-Difference Function (AMF) (S421), and T _recog is determined based on these two time points. At this time, the sound of device B means a sound file pre-recorded in device B. The baseline for T _cc and T _amdf is T _in , just like T _recog .

T _cc by the correlation technique can be obtained as follows.

--- 식(1).

--- Equation (1).

Here, f _rec (n + τ) means a sound file that device B has, and f _ref (τ) means a sound file (sound file input to device B) emitted from device A. N denotes the data length of the sound file of the device B, and τ denotes the data length of the sound file (sound file emitted from the device A) input to the device B.

In the above formula (1), if m is 44,100 and τ is 2,205, the parentheses of the formula (1) are as follows.

f _rec (1 + 0) f _ref (0) + f _rec (1 + 1) f _ref (1) +... + f _rec (1 + 2205) f _ref (2205) + f _rec (2 + 0) f _ref (0) + f _rec (2 + 1) f _ref (1) +... + f _rec (2 + 2205) f _ref (2205) +... + f _rec (44,100 + 0) f _ref (0) + f _rec (44,100 + 1) f _ref (1) +. + f _rec (44,100 + 2205) f _ref (2205).

In this way, the parenthesis of Equation (1) is a technique corresponding to convolution from an analog signal processing point of view, and the meaning of Equation (1) is to calculate the value of n that maximizes the above sum. T _cc is the time corresponding to this value of n.

On the other hand, the recognition time (T _amdf ) by the AMDF (Average-Magnitude-Difference Function) can be obtained as follows.

The correlation technique estimates T _recog at the point that maximizes the sum of the products at each time point (τ = 0, τ = 1, ..., τ = 2,205 in the example above), but AMDF T _recog is estimated to minimize the sum of the absolute values of the differences at the time points (τ = 0, τ = 1, ..., τ = 2,205 in the above example). This technique is known to be quite robust to ambient noise, and therefore, it is known to enable more accurate estimation than the correlation technique, which is vulnerable to ambient noise.

--- 식(2).

--- Equation (2).

In equation (2), f _rec (n + τ), f _ref (τ), n, τ are the same as in the case of equation (1).

As in the above in Equation (2), assuming that m is 44,100 and τ is 2,205, the parentheses of Equation (2) are as follows.

f _rec (1 + 0) -f _ref (0) + | f _rec (1 + 1) -f _ref (1) | +… + | f _rec (1 + 2205) -f _ref (2205) | + | f _rec (2 + 0) -f _ref (0) | + | f _rec (2 + 1) -f _ref (1) | +… + | f _rec (2 + 2205) -f _ref (2205) | +… + | f _rec (44,100 + 0) -f _ref (0) | + | f _rec (44,100 + 1) -f _ref (1) | +… + | f _rec (44,100 + 2205) -f _ref (2205) |.

The meaning of equation (2) is to calculate the value of n that minimizes this sum, and T _amdf is a time point corresponding to the value of n.

The present invention also determines the T _recog to determine T based on the _recog by T and T _{cc amdf} As mentioned above, not only to use only the two values are independently of each other by fusion. This is weighted cross-correlation. The weighted correlation technique is a technique that takes only the advantages of the simple correlation technique and AMDF described above, and the recognition time point T _wc obtained using the weighted correlation technique can be obtained as follows.

--- 식(3).

--- Equation (3).

On the other hand, the recognition unit 32 does not necessarily determine the actual recognition time T _recog as T _wc . This is due to the need to reduce the time required to calculate the distance and to reduce the load on the device. Therefore, the recognition section 32 is a variation of the T _cc and T value deviation is pre-set in _amdf (Th) or more when T _recog the T _cc and T (s422) determines the smaller of _amdf, T _cc and T _amdf group If less than the set value Th, T _wc is determined as T _recog (s423).

If the difference between T _cc and T _amdf is large, it means that a calculation error of T _recog is high. Therefore, the smaller of the two values is determined as T _recog (s422). The reason for the small value is that T _recog should be as short as possible, that is, the point of recognition should be fast enough to improve the accuracy of distance measurement between devices. In other words, if the distance calculation formula of (distance) = (sonic speed) * (sound propagation time) is _used , the distance itself varies depending on which value of T _recog is directly connected to (sound propagation time). For example, if T _cc is 10 seconds from the T _in and T _amdf is 5 seconds from the T _in , this means that it is more likely to be recognized when the time point is 5 seconds, and thus (sound propagation time) This is because the distance is accurately calculated when the direct recognition time is reflected in the sound propagation time (5 seconds in this example).

The smaller the deviation between T _cc and T _amdf, the lower the probability of a T _recog calculation error occurs. To further improve the low probability, T _wc is determined as T _recog (s423).

In addition, the predetermined value Th is a value for checking whether reflection and ringing occur. It is most desirable that T _cc and T _{amdf be} the same, and T _cc and T _amdf are theoretically the same without reflection and ringing. However, even if there is no reflection and ringing, there is actually a deviation between the two values. If this deviation is more than Th, it means that reflection and ringing have occurred, and it means that the calculation error of T _recog is likely to occur. Therefore, it is recognized that this is due to reflection and ringing. Therefore, if the deviation between two values is greater than Th, it is preferable to select the smaller of the two values, and even if less than Th, since there is a slight deviation between the two values, the weighted correlation method is used to reduce the error in calculating the distance.

6 is a diagram illustrating a simulation result for the weighted correlation technique. Compared to the case of FIG. 2, the actual recognition time is shown to be calculated more accurately, and thus will enable more accurate distance measurement in the surrounding noise environment or indoor environment.

_Upon determining T _recog , the recognition unit 32 _notifies the distance calculator 33 of the device A that T _recog has been determined through the AP.

The distance calculator 33 is provided in the device A, and calculates a distance between the two devices based on the time difference between the time point of the emission and the time point T _recog of the notified actual recognition ( _S43 ). This distance can be obtained by the above very simple formula: (distance) = (sonic speed) * (sound propagation time), where d is the distance, c is the speed of sound, and the time at which the sound file emitted from device A reaches device B. Let Δt be.

The key to distance calculation according to the present invention lies in what the time Δt is set to. [Delta] t corresponds to the time when the sound file emitted from device A reaches (propagated) device B, and the time at which the sound file starts to be emitted from device A as described above is '0'.

As mentioned above, the point in time when the sound file emitted from the device A reaches the device B is not the point T _in at which the sound file starts to be input to the input unit 31, but the device B actually recognizes the input sound file. From the point of time T _recog , Δt is determined as follows.

Δt = T _in + T _recog .

Therefore, the distance d between device A and device B is calculated as follows.

d = c * (T _in + T _recog ).

Here, c corresponds to the speed of sound, and when T is the temperature (centigrade unit) of the medium that transmits the speed of sound, it is expressed as c = 331 + 0.9 * T [m / sec]. Typically, c represents 340 [m / sec] as a representative value.

Each of the time points mentioned above in Figure 5 is presented in a simplified diagram.

Meanwhile, the present invention calculates the distance while considering the movement (movement) of the device during the calculation of the distance between the devices. Calculating the distance by reflecting the movement situation is a method of securing the 'continuity' of the distance calculation, thereby providing an effect that can always accurately calculate (check) the distance between devices.

When the devices move, the distance information produced by the distance calculation procedure already in progress cannot maintain accuracy. Therefore, distance measurement persistence (continuity) is required, which may allow device A to continuously generate sound to enable continuous distance measurement. However, this can cause a sudden power dissipation problem because the results of the load on device A and device B can be seen.

Therefore, the present invention monitors the movement of the device using the IEEE802.11 wireless LAN standard and proceeds with distance measurement accordingly. According to the IEEE802.11 wireless LAN standard, a communication device periodically exchanges signals with its associated peripheral node (Access Point (AP)) to measure the sensitivity of the signal.

Each of the initialization units 34 and 35 of the devices A and B periodically checks the sensitivity of the signal according to the IEEE802.11 wireless LAN standard. If the deviation of the signal sensitivity between the check points is greater than or equal to the predetermined value Sth, the motion is generated. The judgment is made to initialize the distance measurement so that the distance calculation is started again (initialize). Initialization may occur at any time if the above initialization condition is satisfied during the process of the present invention. Even if the distance is calculated, if the above described initialization condition occurs, the calculated distance is meaningless, and thus initialization occurs. Each of the initialization units 34 and 35 of the devices A and B notifies each other that a situation requiring initialization occurs through an access point (AP), and the initialization is performed by the initialization unit 35 of the device B to the recognition unit 32. The initialization unit 35 of A is performed by transmitting a reset signal to the distance calculator 33.

In addition, it is more preferable to adopt the deviation of the signal sensitivity of the current check point and the signal sensitivity of the previous check point in order to improve the continuous accuracy of the distance measurement.

The present invention can also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system.

Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, and also implemented in the form of carrier waves (for example, transmission over wired or wireless networks). It includes being. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

The present invention has been described above with reference to preferred embodiments thereof. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention.

Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

1 is a view showing a conventional distance measuring method using sound.

FIG. 2 is a view provided to show the disadvantages (disadvantages of the correlation technique) of the distance measuring method according to FIG. 1.

3 is a view showing a preferred configuration of the present invention.

4 is a view showing a preferred flow of the present invention.

5 is a diagram illustrating each of the viewpoints mentioned in the present invention in a simplified diagram.

6 is a diagram illustrating a simulation result for the weighted correlation technique.

Claims (11)

Any communication device that emits a sound file; An input unit provided in the communication device (the other device) to measure the distance to the predetermined communication device and receiving the emitted sound file; A recognition unit provided in the counterpart communication device and recognizing the input sound file; And And a distance calculator provided in the predetermined communication device, the distance calculator calculating a distance between the two devices based on a time difference between the time of the emission and the time of the recognition. The method of claim 1, wherein the recognition unit _Between the emitted sound file and the sound file included in the distance measurement target communication device, and calculating a time point T _recog having the greatest degree of association, and recognizing the input sound file. Distance measuring system. In this case, the reference time point of the T _recog is a time point at which the emitted sound file starts to be input to the input unit. The method of claim 2, wherein the recognition unit On the basis of the two sound files on the correlation technique recognize obtained using the (cross-correlation) point (T _cc) and recognition (T _amdf) obtained using AMDF (Average-Magnitude-Difference Function ) the T _recog Determining the distance between the communication devices. In this case, the reference time point of the T _cc and T _amdf is a time point at which the emitted sound file starts to be input to the input unit. The method of claim 3, wherein the recognition unit If the deviation of the T _cc and the T _amdf a predetermined value or higher, and determining the T _recog to a value of the T _cc and the T _amdf; When the deviation between the T _cc and the T _amdf is less than or equal to the preset value, the recognition time point T _wc obtained by using a weighted cross-correlation of the T _cc and the T _amdf is determined. Distance measuring system between communication devices, characterized in that determined by T _recog . The device of claim 1, wherein the two communication devices are: The apparatus further includes an initialization unit which checks the sensitivity of a signal periodically transmitted / received with the AP (Access Point) linked to each other, and if the deviation of the signal sensitivity between the time points of the check is greater than or equal to a predetermined value, initializing the distance measurement. Distance measuring system between the communication device, characterized in that. (a) receiving a sound file emitted from a predetermined communication device by a distance measurement target communication device (an external device) with the predetermined communication device; (b) the counterpart device recognizing the input sound file; And (c) the predetermined communication device calculating a distance between the two devices based on a time difference between the time of the emission and the time of the recognition. The method of claim 6, wherein step (b) A distance between the communication devices, wherein the emitted sound file and the sound file of the counterpart device are correlated with each other to calculate a point in time (T _recog ) having the greatest degree of association, and recognize the input sound file. How to measure. In this case, the reference time point of the T _recog is a time point at which the emitted sound file starts to be input to the counterpart device. The method of claim 7, wherein step (b) On the basis of the two sound files on the correlation technique recognize obtained using the (cross-correlation) point (T _cc) and recognition (T _amdf) obtained using AMDF (Average-Magnitude-Difference Function ) the T _recog Determining the distance between the communication devices. At this time, the reference time point of the T _cc and T _amdf is a time point at which the emitted sound file starts to be input to the counterpart device. The method of claim 8, wherein step (b) (b1) determining by the T _cc and wherein if the deviation of T _amdf a predetermined value or higher, the smaller of the T _recog the T _cc and the T _amdf; And (b2) If the deviation between the T _cc and the T _amdf is less than or equal to the predetermined value, a recognition time point T _wc obtained by using a weighted cross-correlation of the T _cc and the T _amdf . And determining T _recog as the distance between the communication devices. The method according to any one of claims 6 to 9, (d) checking, by the two communication devices, a sensitivity of a signal periodically transmitted and received with an access point (AP) linked thereto; And and (e) if the deviation of the signal sensitivity between the time points of the check is greater than or equal to a preset value, returning to step (a). A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 6 to 10 on a computer.

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