Distance estimation system, information processing device, and distance estimation method

Abstract

The present invention improves estimation accuracy of a distance.　A distance estimation system (1) comprises: a reference communication terminal (100) and a target communication terminal (10) that each perform multicarrier transmission; and an information processing device (500) that estimates a distance between the reference communication terminal and the target communication terminal according to a result of communication between the reference communication terminal and the target communication terminal. The information processing device: specifies a tentative estimation value of the distance on the basis of a received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal; removes a component of a long-delay wave from a received wave of the received signal on the basis of the tentative estimation value; calculates a distance spectrum of the received signal on the basis of the received signal from which the component of the long-delay wave has been removed; and estimates the distance on the basis of an intensity of the distance spectrum in a predetermined distance search range including the tentative estimation value.

Description

Distance estimation system, information processing device, distance estimation method

[0001] The present invention relates to a distance estimation system, an information processing device, and a distance estimation method.

[0002] A known technique for estimating the distance to a target object includes a transmitting means for transmitting a transmission signal and a receiving means for receiving the reflected wave of the transmission signal as a received signal, and the technique involves processing the received signal to detect the target (see Patent Document 1).

[0003] In the above technology, the radar device includes an FFT transformation means for Fourier transforming a received signal into frequency spectrum data, a peak frequency detection means for detecting the peak frequency of the frequency spectrum data, a data extraction means for extracting data near the peak frequency from the frequency spectrum data, an inverse FFT transformation means for inversely transforming the data near the peak frequency into time-axis data, and a target detection means for detecting a target by performing high-resolution processing on the time-axis data.

[0004] Japanese Patent Publication No. 2014-132250

[0005] Incidentally, round-trip based channel sounding is known as a distance estimation method between two communication terminals. In round-trip, distance is measured by the two communication terminals coordinating to alternately send and receive signals. As for channel sounding, for example, specifically, multi-carrier phase-based distance estimation is known, which estimates distance by comparing the received phases of unmodulated carrier transmissions across multiple frequencies.

[0006] On the other hand, in channel sounding, it is necessary to eliminate the effects of reflected and delayed waves, which degrade the estimation. For this reason, channel sounding employs high-resolution multipath separation techniques such as the MUSIC (Multiple Signal Classification) algorithm, and round-trip signal transmission, which removes the phase of the local oscillator by multiplying the signal that reaches the target communication terminal (target) from the reference communication terminal (anchor node) by the signal that reaches the anchor node from the target.

[0007] However, if each of the round-trip propagation paths between the anchor node and the target consists of, for example, L paths (propagation paths), and if we consider overlaps with the same delay time due to the product of the bidirectional signals as a single path, then L(L+1) / 2 paths are generated, increasing the number of paths. When the number of paths increases, there is a problem that the accuracy of distance estimation decreases if it exceeds the resolution of the multipath separation technique.

[0008] This invention addresses the above-mentioned problems as an example and aims to provide a technology for improving the accuracy of distance estimation.

[0009] To achieve the above objective, the distance estimation system according to the present invention comprises a reference communication terminal and a target communication terminal that perform multi-carrier transmission, and an information processing device that estimates the distance between the reference communication terminal and the target communication terminal according to the communication results between the reference communication terminal and the target communication terminal. The information processing device identifies a provisional estimate of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removes the long-time delayed wave component from the received wave of the received signal based on the provisional estimate, calculates the distance spectrum of the received signal based on the received signal from which the long-time delayed wave component has been removed, and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimate.

[0010] The distance estimation system according to the present invention can improve the accuracy of distance estimation.

[0011] This is a functional block diagram schematically showing the configuration of a distance estimation system according to an embodiment of the present invention. This is a flowchart showing an example of distance estimation processing in the distance estimation system according to this embodiment. This is a schematic diagram showing round-trip transmission performed between a reference communication terminal and a target communication terminal in the distance estimation system according to this embodiment. This is a diagram for explaining the process of identifying a provisional distance estimate based on a received signal in the distance estimation system according to this embodiment. This is a diagram for explaining the process of removing the long-time delayed wave component from the received wave of the received signal in the distance estimation system according to this embodiment. This is a diagram showing an enlarged view of region A in Figure 6. This is a diagram showing an example of distance estimation results between the distance estimation system according to this embodiment and the reference example distance estimation system.

[0012] 1. Outline of Embodiments First, a general overview of a typical embodiment of the invention disclosed in this application will be given. In the following description, as an example, reference numerals on the drawings corresponding to the components of the invention are indicated in parentheses.

[0013] [1] A distance estimation system (1) comprising a reference communication terminal (100) and a target communication terminal (10) that each perform multi-carrier transmission, and an information processing device (500) that estimates the distance between the reference communication terminal and the target communication terminal according to the communication result between the reference communication terminal and the target communication terminal, wherein the information processing device identifies a provisional estimate of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removes the long-time delayed wave component from the received wave of the received signal based on the received signal from which the long-time delayed wave component has been removed, and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimate.

[0014] [2] The provisional estimated value is the index with the smallest value among the indexes exceeding a threshold determined based on the maximum peak in the waveform obtained by converting the received signal into a time response. The distance estimation system according to [1].

[0015] [3] The distance is estimated based on the maximum value of the intensity of the distance spectrum within the search range. The distance estimation system according to [1] or [2].

[0016] [4] The distance spectrum is calculated by converting the received signal with the components of the long-time delay wave removed into a frequency-domain signal and separating the multipaths included in the frequency-domain signal. The distance estimation system according to any one of [1] to [3].

[0017] [5] An information processing apparatus (500) that estimates the distance between a reference communication terminal (100) and a target communication terminal (10) that each perform multi-carrier transmission, based on the communication results. The apparatus specifies a provisional estimated value of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removes the components of the long-time delay wave from the received wave of the received signal based on the provisional estimated value, calculates the distance spectrum of the received signal based on the received signal with the components of the long-time delay wave removed, and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimated value.

[0018] [6] A distance estimation method for estimating the distance between a reference communication terminal (100) and a target communication terminal (10) that each perform multi-carrier transmission, based on the communication results. An information processing apparatus (500) specifies a provisional estimated value of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removes the components of the long-time delay wave from the received wave of the received signal based on the provisional estimated value, calculates the distance spectrum of the received signal based on the received signal with the components of the long-time delay wave removed, and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimated value.

[0019] 2. Specific Examples of Embodiments The distance estimation system, information processing device, and distance estimation method according to embodiments of the present invention will be described below with reference to the drawings.

[0020] Figure 1 is a functional block diagram schematically showing the configuration of a distance estimation system according to an embodiment of the present invention. As shown in Figure 1, the distance estimation system 1 consists of a target communication terminal 10, a reference communication terminal 100, and a server 500. In the distance estimation system 1, the target communication terminal 10 is a terminal that moves together with the target object whose position is to be estimated. In the distance estimation system 1, the reference communication terminal 100 is a terminal that communicates wirelessly with the target communication terminal 10 and acquires information necessary for estimating the distance to the target communication terminal 10, which is necessary for the distance estimation method.

[0021] The reference communication terminal 100 is an electronic device capable of multi-carrier transmission. The reference communication terminal 100 may be a device used to estimate the position coordinates of the target communication terminal 10 by wireless communication such as a radio beacon, or it may be an electronic device such as a smartphone, tablet terminal, or various types of computers.

[0022] In the distance estimation system 1, in order for the reference communication terminal 100 to estimate the distance to the target communication terminal 10, it is required that the reference communication terminal 100 is in a state where it can communicate with the target communication terminal 10. However, as long as the reference communication terminal 100 and the target communication terminal 10 can communicate, there is no particular limit to the number of target communication terminals 10 and reference communication terminals 100 within the distance estimation system 1.

[0023] The target communication terminal 10 is an electronic device capable of multi-carrier transmission, similar to the reference communication terminal 100. The target communication terminal 10 can be any electronic device capable of communicating with the reference communication terminal 100 via wireless communication, such as a smartphone, tablet, or various types of computers. The target communication terminal 10 and the reference communication terminal 100 may be the same electronic device, or they may be different electronic devices capable of communicating with each other.

[0024] Both the target communication terminal 10 and the reference communication terminal 100 have control units 11, 110, storage units 12, 120, and communication units 13, 130.

[0025] The control units 11 and 110 are implemented by a computer such as a microcomputer, which is realized by a processor such as an MCU (Micro Control Unit) (not shown) and a memory for calculations such as RAM (Random Access Memory). The MCU is a calculation device that realizes various functions as the target communication terminal 10 or reference communication terminal 100 by executing calculation processing of a program. The memory is a volatile memory in which the program processed by the MCU is stored. The control units 11 and 110 store the function programs stored in the storage units 12 and 120 in the memory. The function programs stored in the storage units are programs for realizing various functions of the target communication terminal 10 or reference communication terminal 100 in this embodiment. Programs corresponding to the functions to be realized are sequentially stored in the memory and executed sequentially by the MCU. The program is composed of functions and fixed values ​​corresponding to the function. When the program is executed, not only functions but also data, which are fixed values, are required.

[0026] The memory units 12 and 120 store identification information that can uniquely identify each target communication terminal 10 or reference communication terminal 100 within the distance estimation system 1, the position coordinates of the reference communication terminal 100 itself, and programs that can be executed by the control units 11 and 110 described above.

[0027] Communication units 13 and 130 both transmit and receive multiple carriers and perform multi-carrier transmission with different wavelengths for each carrier. Through multi-carrier transmission, communication units 13 and 130 enable either the reference communication terminal 100 or the target communication terminal 10 to communicate with the other of the target communication terminal 10 or the reference communication terminal 100. The multi-carrier transmission used by the target communication terminal 10 and the reference communication terminal 100 includes, for example, OFDM (Orthogonal Frequency-Division Multiplexing) such as Wi-Fi and LTE, and frequency-hopping spread spectrum such as Bluetooth®.

[0028] Server 500 is an example of an information processing device. Server 500 can, for example, communicate the communication results between a reference communication terminal 100 and a target communication terminal 10 via wireless or wired communication. Server 500 is an example of a computer, such as a PC or server device, realized by a processor (such as an MCU, not shown), a memory for calculations (such as RAM, or Random Access Memory), and a memory unit for storing programs and processing data. The MCU is a calculation unit that realizes various functions of Server 500, as described below, by executing the calculations of a program. The memory is a volatile memory in which programs processed by the MCU are stored. Server 500 stores the functional programs stored in the memory. The functional programs stored in the memory are programs for realizing various functions of Server 500 in this embodiment. The memory sequentially stores programs corresponding to the functions to be realized and is executed sequentially by the MCU. The programs consist of functions and fixed values ​​corresponding to the functions. When a program is executed, it requires not only functions but also fixed data values.

[0029] The server 500, with the hardware configuration and program described above, comprises functional blocks such as a control unit 510, a storage unit 520, and a communication unit 530.

[0030] The control unit 510, in cooperation with the MCU and memory, executes a program stored in the storage unit 520, thereby realizing its function as an information processing device in the distance estimation system 1 by the server 500, and performing the following processing, and executing the distance estimation method for the target communication terminal 10.

[0031] The memory unit 520 is implemented using non-volatile memory such as EEPROM (Electrically Erasable Programmable Read-Only Memory). The memory unit 520 stores functional programs for realizing various functions. The memory unit 520 also stores various processing data used by the server 500, such as information used when estimating the distance between the target communication terminal 10 and the reference communication terminal 100, specifically numerical values ​​used for distance estimation and information on calculation formulas described later.

[0032] The communication unit 530 can communicate with external devices, i.e., the reference communication terminal 100, for example, by wireless or wired communication using a communication interface (not shown). The communication unit 530 may also be able to communicate with the target communication terminal 10.

[0033] The server 500 may also be equipped with an operation unit and a display unit, which are input interfaces for the user to operate the server 500 and output interfaces for the user to perceive the operating status of the server 500.

[0034] Examples of hardware configurations for implementing the control unit include various touch panels, keyboards, numeric keypads, buttons, etc. However, the hardware configuration for implementing the control unit is not limited to the examples described above; it only needs to have the functionality to receive input from the user to operate the server 500. The control unit may, for example, accept operations via commands from various communication interfaces via the communication unit 530, or it may accept operations via voice command input.

[0035] The hardware configuration for realizing the display unit is a display device equipped with a functional unit for the user to perceive the operating status of the server 500, such as an LCD (Liquid Crystal Display) or an organic EL display. If the operation unit and display unit are, for example, a touch panel, then the operation unit function and the display unit function are integrated. Furthermore, the server 500 may not have some of the functions of an operation unit or display unit. Also, the server 500 is not limited to having an operation unit and display unit; for example, the operation unit and display unit functions of the server 500 may be realized from other information processing terminals such as a reference communication terminal 100, a smartphone, or a tablet terminal.

[0036] Next, we will describe the specific processing of the distance estimation method for the target communication terminal 10, which is executed by the server 500 in the distance estimation system 1.

[0037] Figure 3 is a schematic diagram showing round-trip transmission between a reference communication terminal 100 and a target communication terminal 10 in the distance estimation system according to this embodiment.

[0038] Let n be the subcarrier index at the anchor node, the reference communication terminal 100, and f be the subcarrier frequency. ｎ , the phase of the local oscillator is θ Ａ (n) Then the complex band signal u of the transmitted tone signal Ａ (n) is given by the following equation (1).

[0039]

[0040] Let H(n) be the channel in the propagation path, and the target received down-converted signal u is converted to a baseband signal by a down-converting carrier wave at the target communication terminal 10. Ｔ (n) is given by the following equation (2).

[0041]

[0042] Here, assuming that the propagation path is a single-wave environment in line-of-sight (LOS) space, H(n) is given by the following equation (3).

[0043]

[0044] Here, a ０ is the channel gain, and τ ０ is the time delay. Assuming the distance is d and the speed of light is c, then τ ０ = d / c. Therefore, the received down-converted signal u Ｔ (n) on the target side shown in Equation (2) becomes the following Equation (4).

[0045]

[0046] Similarly, the complex band signal v Ｔ (n) of the transmission tone signal from the target communication terminal 10 to the reference communication terminal 100 is given by the following Equation (5).

[0047]

[0048] On the other hand, the down-converted signal v Ａ (n) of the signal that has reached the reference communication terminal 100 becomes the following Equation (6).

[0049]

[0050] The received down-converted signal u Ｔ (n) on the target side fed back from the target communication terminal 10 to the reference communication terminal 100, and the down-converted signal v Ａ (n) held by the reference communication terminal 100 are used to multiply the received down-converted signal u Ｔ (n) on the target side and the down-converted signal v Ａ (n) on the anchor node side. The resulting signal s(n) (n = 1, 2,..., N Ｃ ) can be expressed by the following Equation (7).

[0051]

[0052] As shown in Equation (7), in the server 500, the local oscillator phases on the anchor node side and the target side are canceled out by the multiplication operation represented by Equation (7), and a signal s(n) with a phase displacement amount proportional to the propagation path distance d = c·τ ０ is obtained.

[0053] Figure 2 is a flowchart illustrating an example of distance estimation processing in the distance estimation system 1 according to this embodiment. Figure 2 shows the processing related to the distance estimation method performed by the server 500 in the distance estimation system 1. As shown in Figure 2, the server 500, through the cooperation of the MCU and memory of the control unit 510, executes a program stored in the storage unit 520, thereby realizing its function as an information processing device in the distance estimation system 1 and executing the distance estimation method for the target communication terminal 10.

[0054] In the reference communication terminal 100 and the target communication terminal 10, the signal s(n) shown in equation (7) can be considered as a frequency response. Therefore, the server 500 converts the signal s(n) into a time-response signal using an inverse fast Fourier transform (IFFT) (step S101). At this time, the number of IFFT points is N. ＩＦＦＴ is, N Ｃ Set it to a larger value than that.

[0055] Figure 4 is a diagram illustrating the process of identifying a provisional distance estimate based on a received signal in the distance estimation system 1 according to this embodiment. The waveform shown in Figure 4 is obtained by converting the signal s(n) into a time-response signal using the IFFT in step S101.

[0056] Server 500 determines the maximum peak A of the amplitude in a predetermined search range for the signal s(n) shown in Figure 4, which has been converted. Ｐ Detect (step S102). The maximum amplitude peak A shown in Figure 4. Ｐ The search range SR is the range of the index that corresponds to the range between the assumed minimum and maximum distance d between the reference communication terminal 100 and the target communication terminal 10.

[0057] Server 500 has a maximum amplitude peak A as shown in Figure 4. Ｐ Based on this, the maximum peak A Ｐ Peak A of the leading wave is a peak that occurred prior to the main peak. ｆ Threshold A for detection Ｂ Set it as shown in the following equation (8) (step S103). Peak A of the leading wave ｆ Threshold A ＢAmong the signal peaks exceeding a certain value, this is the peak with the smallest distance, i.e., the peak with the smallest index value. Leading wave peak A ｆ The index of I ｆ Let it be so. In equation (8), A ＳＬ The index of the signal converted to a time response ranges from 0 to I. ｆ This is the side lobe level, which is the average amplitude between the two points. Also, η is the threshold A. Ｂ These are parameters for setting [something].

[0058] A Ｂ =η・(A Ｐ -A ＳＬ ) + A ＳＬ ... (8)

[0059] Server 500 is at peak A ｆ Index I ｆ Detect this index I ｆ This is used as a provisional distance estimate (step S104).

[0060] Figure 5 is a diagram illustrating the process of removing long-time delayed wave components from the received wave of the received signal in the distance estimation system 1 according to this embodiment.

[0061] As shown in Figure 5, the server 500 converts s(n) into a time response waveform and uses the index I detected in step S104. ｆ The window function is shifted so that the gain of the window function is maximized. Based on the window function, the server 500 weights the output of the waveform obtained by converting s(n) to a time response. By weighting the output of the waveform obtained by converting to a time response, the server 500 performs a filtering process to remove waveform peaks with large index values ​​in the signal obtained by converting to a time response, i.e., long-delayed waves (step S105).

[0062] Server 500 performs a Fast Fourier Transform (FFT) on the signal from which long-time delayed waves have been removed, thereby converting the signal, which has been converted from s(n) to a time response, into a frequency domain signal (step S106).

[0063] In step S106, the server 500 calculates a correlation matrix for the signal converted to a frequency domain signal while shifting the subchannels corresponding to the subarray (step S107). Specifically in step S107, the received I / Q signal with a predetermined subchannel length NS (<NC) is treated as a vector with respect to the channel length NC, and multiplied by its complex conjugate transpose vector. This operation is performed while shifting the subchannels, and the resulting correlation matrix of NS rows and NS columns is calculated by adding them together. Furthermore, in order to improve the separation of the arriving path, the subchannel vector length may be set to NT (>NS), and the subchannel vector may be multiplied by a random matrix of NS rows and NT columns to obtain a compressed subchannel vector as a preprocessing step, while similarly calculating the correlation matrix of NS rows and NS columns. Moreover, the path separation characteristics of the correlation matrix may be improved by adding a forward correlation matrix that shifts from lower frequencies to higher frequencies and a backward correlation matrix that is calculated while shifting from higher frequencies to lower frequencies.

[0064] Figure 6 shows an example of a distance spectrum calculated by removing the long-time delayed wave component from the received signal in the distance estimation system 1 according to this embodiment. Figure 7 is an enlarged view of region A in Figure 6. In Figures 6 and 7, the vertical axis represents the intensity of the frequency domain signal (arriving signal), and the horizontal axis represents the round-trip distance. Figures 6 and 7 show the distance spectrum ds1 from the distance estimation system 1 and the distance spectrum ds2 from the reference example distance estimation system. The reference example distance estimation system is a system that estimates distance without performing the processing of step S105 in the distance estimation system 1.

[0065] Server 500 uses index I, which corresponds to the provisional distance estimate identified in step S104. ｆ The search range SR2 before and after (see Figures 6 and 7) is set as the search range for distance d (step S108).

[0066] The server 500 performs eigenvector decomposition on the correlation matrix calculated in step S107 and calculates the distance spectrum (step S109).

[0067] Server 500 uses peak A, which is the peak with the maximum intensity of the distance spectrum ds1 in the search range SR2, to estimate the distance d. ｄs１ It is detected as such (step S110).

[0068] Server 500 detects peak A in step S110. ｄｓ１ The index is converted and estimated as distance d (step S111). In Figures 6 and 7, the shortest distance peak A of the distance spectrum ds1 by the distance estimation system 1 is shown. ｄｓ１ The distance d estimated from this is 11.0 m / 2 = 5.5 m. On the other hand, the shortest distance peak A in the distance spectrum ds2 obtained by the distance estimation system in the reference example. ｄｓ２ The estimated distance d is 11.7 m / 2 = 5.85 m.

[0069] As described above, when comparing the distance spectrum ds1 from distance estimation system 1 with the distance spectrum ds2 from the reference example distance estimation system, the shortest distance peak A in distance spectrum ds1 ｄｓ１ The shortest distance peak A in the distance spectrum ds2 is ｄｓ２ This shows that the error between the calculated distance and the actual distance is smaller.

[0070] Figure 8 shows an example of distance estimation results between the distance estimation system 1 according to this embodiment and the distance estimation system of the reference example.

[0071] In Figure 8, the vertical axis represents the cumulative distribution function (CDF), and the horizontal axis represents distance. Figure 8 shows the distance estimation results by distance estimation system 1 and the distance estimation results by the reference example distance estimation system for distances d = 2.0 m, 5.0 m, 8.0 m, and 11.0 m, respectively. In Figure 8, the cumulative distribution function of the distance estimation results by distance estimation system 1 is shown as a solid line, and the cumulative distribution function of the distance estimation results by the reference example distance estimation system is shown as a dashed line.

[0072] As shown in Figure 8, compared to the distance estimation results from the reference example distance estimation system, the difference between the set distance d and the estimated result is smaller for distance estimation system 1. The median estimation error for distance estimation results from the reference example distance estimation system is 0.5 m or more, while the median estimation error for distance estimation results from distance estimation system 1 is 0.5 m or less.

[0073] As explained above, in the distance estimation system 1, the server 500 uses the received signals of the reference communication terminal 100 transmitted and received between the reference communication terminal 100 and the target communication terminal 10, which each perform multi-carrier transmission, to determine the index I as a provisional estimate of the distance d. ｆ Identify the index I. Server 500 is index I ｆ Based on this, the long-time delayed wave component is removed from the received waveform of the received signal, specifically the waveform obtained by converting s(n) into a time response. Server 500 calculates the distance spectrum ds1 of the received signal based on the received signal from which the long-time delayed wave component has been removed, and index I ｆ Within a predetermined search range SR2 that includes the specified area, the distance d is estimated based on the intensity of the distance spectrum ds1.

[0074] Specifically, in the distance estimation method executed by the server 500 in the distance estimation system 1, the provisional estimate is the maximum peak A of the amplitude in the time response of the signal s(n). Ｐ Threshold A based on this Ｂ The smallest index I among signals exceeding this value. ｆ That's fine.

[0075] Furthermore, in the distance estimation method executed by the server 500 in the distance estimation system 1, the maximum value of the intensity of the distance spectrum ds1 in the distance search range SR2, i.e., peak A ｄｓ１ The distance d may be estimated based on this.

[0076] Furthermore, in the distance estimation method executed by the server 500 in the distance estimation system 1, the distance spectrum ds1 may be calculated using a multipath separation technique that converts the received signal, from which the long-time delayed wave component has been removed, into a frequency domain signal and separates the multipath components contained in the frequency domain signal.

[0077] To eliminate the effects of reflected and delayed waves, which degrade estimation, channel sounding employs high-resolution multipath separation techniques such as the MUSIC algorithm and round-trip signal transmission, as described above. If the number of paths increases due to the product of the bidirectional signals in the round-trip propagation paths between the reference communication terminal 100 and the target communication terminal 10, the accuracy of distance estimation may decrease if the resolution of the multipath separation technique is exceeded.

[0078] Here, according to the distance estimation method executed by the server 500 in the distance estimation system 1, the server 500 uses index I ｆ Based on this, by removing the long-time delayed wave component from the waveform obtained by converting s(n) into a time response, the influence of long-distance paths can be suppressed from the increasing number of paths. As a result, the distance estimation method executed by server 500 can effectively utilize the resolution of the multipath separation technology, thereby improving the accuracy of distance estimation while suppressing the degradation of distance estimation accuracy.

[0079] Furthermore, those skilled in the art may modify the present invention as appropriate in accordance with prior art knowledge. Such modifications, insofar as they still possess the configuration of the present invention, are of course included within the scope of the present invention.

[0080] For example, in the distance estimation system 1, an example was described in which the information processing device that performs the distance estimation method is a server 500, but the present invention is not limited to this. The information processing device that performs the distance estimation method may be an information processing device other than the server 500. Also, the information processing device that performs the distance estimation method and the reference communication terminal 100 may be a single device, that is, the reference communication terminal 100 may be the device that performs the distance estimation method.

[0081] For example, in distance estimation system 1, the high-resolution multipath separation technique is not limited to the MUSIC method, but may be performed by other methods.

[0082] 1... Distance estimation system, 10... Target communication terminal, 11, 110, 510... Control unit, 12, 120, 520... Storage unit, 13, 130, 530... Communication unit, 100... Reference communication terminal, 500... Server (information processing device), A Ｂ ...Peak threshold, A ｄ , A ｄｓ１ , A ｄｓ２ ...Peak, A ｆ ...Peak of the leading wave, A Ｐ ...Maximum peak, d...distance, ds1...distance spectrum, ds2...distance spectrum, SR, SR2...search range, I ｆ ...index

Claims

1. A distance estimation system comprising: a reference communication terminal and a target communication terminal, each performing multi-carrier transmission; and an information processing device that estimates the distance between the reference communication terminal and the target communication terminal according to the communication results between the reference communication terminal and the target communication terminal, wherein the information processing device identifies a provisional estimate of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal; removes the long-time delayed wave component from the received wave of the received signal based on the received signal from which the long-time delayed wave component has been removed; and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimate.

2. The distance estimation system according to claim 1, wherein the provisional estimate is the index with the smallest value among the indices that exceed a threshold determined based on the maximum peak in the waveform converted to the time response of the received signal.

3. The distance estimation system according to claim 1 or 2, wherein the distance is estimated based on the maximum value of the intensity of the distance spectrum within the search range.

4. The distance estimation system according to any one of claims 1 to 3, wherein the distance spectrum is calculated by converting the received signal from which the long-time delayed wave component has been removed into a frequency domain signal, and separating the multipath included in the frequency domain signal.

5. An information processing device for estimating the distance between a reference communication terminal and a target communication terminal according to the communication results of a reference communication terminal and a target communication terminal, respectively, which perform multi-carrier transmission, the information processing device for determining a provisional estimate of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removing the long-time delayed wave component from the received wave of the received signal based on the received signal from which the long-time delayed wave component has been removed, and estimating the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimate.

6. A distance estimation method for estimating the distance between a reference communication terminal and a target communication terminal according to the communication results of a reference communication terminal and a target communication terminal that each perform multi-carrier transmission, wherein an information processing device identifies a provisional estimate of the distance based on the received signal of the reference communication terminal transmitted and received between the reference communication terminal and the target communication terminal, removes the long-time delayed wave component from the received wave of the received signal based on the received signal from which the long-time delayed wave component has been removed, and estimates the distance based on the intensity of the distance spectrum within a predetermined search range of the distance including the provisional estimate.

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