Interference source estimation system

Abstract

To provide an interference source estimation system with which it is possible to estimate in real time the generation of an interference source in an RFID reader writer network.SOLUTION: An interference source estimation system 900 measures received electric power Pr1, received electric power Pr2, and received electric power Pr3 having been received by a plurality of antennas on the basis of an interference wave in a first RFID reader writer network 11 composed of a plurality of antennas ANT1-1 to ANT1-3 connected to the first RFID reader writer network 12, calculates a distance d from the plurality of antennas to an interference source In on the basis of these received electric powers, estimates the location of the interference source In from an intersection Ia of the distance d and creates an interference source estimation database 621 on the basis of the calculated distance d from the plurality of antennas to the interference source In, detects an interference wave on the basis of the interference source estimation database 621, and notifies of the interference source In when the interference intensity of the detected interference wave is greater than or equal to a threshold.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an interference source estimation system. [Background technology]

[0002] Conventionally, RFID reader / writers using the UHF band are convenient because of their relatively long communication distances, but the frequency bands and available channels are limited, making them susceptible to interference from radio waves from the antennas of other RFID reader / writers, which can cause communication with tags to fail.

[0003] Therefore, in order to avoid and reduce communication failures due to interference in RFID reader / writer networks consisting of multiple antennas connected to RFID reader / writers, the hopping method is used as a radio wave transmission method overseas, while the LBT (Listen Before Talk) and MS (Miller Subcarrier) methods are used in Japan.Other physical workarounds have included the installation of radio wave absorbers, shielding plates, and shielding cases.

[0004] For example, an RFID system has been disclosed that has multiple antennas that read data from RFID tags, and the position detection means is equipped with a distance sensor that detects the distance to the position of the RFID tag (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-249488 Summary of the Invention [Problem to be solved by the invention]

[0006] However, interference prevention in radio wave transmission methods is not perfect. For example, in the hopping method, retransmission is performed when a collision occurs due to interference, which can result in a decrease in throughput due to frequent retransmissions. In the LBT method, the frequency channel may be used by another RFID reader / writer, and communication delays due to waiting time for an open channel can result in a decrease in throughput.

[0007] Furthermore, the effectiveness of installing radio wave absorbers and shields is limited, and they are also expensive. With these methods, even if interference occurs, it is not immediately detected; the problem is only noticed once a significant drop in throughput occurs. The problem is that it takes a great deal of time and effort to then conduct an on-site investigation to resolve the cause.

[0008] In view of the above-mentioned problems, an object of the present invention is to provide an interference source estimation system that can estimate the occurrence of an interference source in an RFID reader / writer network in real time. [Means for solving the problem]

[0009] In order to achieve the above object, the interference source estimation system of the present invention measures the received power received by multiple antennas based on interference waves in an RFID reader / writer network consisting of multiple antennas connected to RFID reader / writers, calculates the distance from the multiple antennas to an interference source based on the received power measured by the multiple antennas, estimates the position of the interference source from the intersection of the distances based on the distances to the interference source calculated from the multiple antennas to create an interference source estimation database, detects the interference waves based on the interference source estimation database, and reports the interference source if the interference strength of the detected interference waves is equal to or greater than a threshold. [Effects of the Invention]

[0010] According to the present invention, it is possible to estimate in real time the occurrence of an interference source in an RFID reader / writer network. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an example of an interference source estimation system according to the present embodiment. [Figure 2] FIG. 10 is a diagram showing an example of observing interference waves (radio waves) from each antenna arranged in the RFID reader / writer network. [Figure 3] FIG. 10 is a diagram illustrating that the position of an interference source can be identified by inputting different assumed values ​​to the function α. [Figure 4] FIG. 1 illustrates an example of identifying an interference source based on a directional antenna. [Figure 5] FIG. 10 is a diagram showing an example in which each antenna detects interference waves from other RFID reader / writer networks based on an interference source estimation database and reports the estimated interference source. [Figure 6] FIG. 10 is a diagram showing an example of reporting an estimated interference source on a map (coordinates) on which actual stores are located. [Figure 7] FIG. 10 is a diagram showing an example of sharing setting information between RFID reader / writer networks. [Figure 8] FIG. 10 is a diagram showing an example in which antenna coordinates, transmission power, frequency channel used, and transmission timing are adjusted based on shared setting information. [Figure 9] Of the setting information described in FIG. 8, this diagram illustrates the positions (coordinates) of the antennas arranged in the first RFID reader / writer network and the second RFID reader / writer network. [Figure 10] FIG. 10 is a diagram showing the transition of sharing of setting information in each RFID reader / writer network. [Figure 11] FIG. 10 is a diagram showing the transition of sharing of setting information in each RFID reader / writer network. [Figure 12] FIG. 10 is a diagram showing the transition of sharing of setting information in each RFID reader / writer network. [Figure 13] FIG. 10 is a diagram showing the transition of sharing of setting information in each RFID reader / writer network. [Figure 14]FIG. 10 is a diagram showing the transition of sharing of setting information in each RFID reader / writer network. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present embodiment will be described below with reference to the drawings. Note that each embodiment can be implemented in combination with a plurality of other embodiments within a range that does not contradict each other.

[0013] An interference source estimation system according to this embodiment will be described. Fig. 1 is a diagram showing an example of an interference source estimation system 900 according to this embodiment. The interference source estimation system 900 is used to estimate the occurrence of an interference source in an RFID reader / writer network in real time.

[0014] The interference source estimation system 900 shown in Fig. 1 is provided in a first store 100, a second store 200, a third store 300, and a fourth store 400. The interference source estimation system 900 shown in Fig. 1 includes a first RFID reader / writer network 11, a second RFID reader / writer network 21, and a server 600. The first RFID reader / writer network 11 is provided in the first store 100. The first RFID reader / writer network 11 is made up of at least one first RFID reader / writer 12 and a plurality of antennas ANT1-1, ANT1-2, ANT1-3, and ANT1-4 arranged in the first store 100. The second RFID reader / writer network 21 is provided in the fourth store 400. The second RFID reader / writer network 21 is made up of at least one or more second RFID reader / writers 22 and a plurality of antennas ANT2-1, ANT2-2, ANT2-3, ANT2-4, and ANT2-5 arranged in the fourth store 400. That is, the first RFID reader / writer network 11 is made up of the first RFID reader / writer 12 and antennas ANT1-1, ANT1-2, ANT1-3, and ANT1-4 connected to the first RFID reader / writer 12 so as to be able to communicate with each other, and the second RFID reader / writer network 21 is made up of the second RFID reader / writer 22 and antennas ANT2-1, ANT2-2, ANT2-3, ANT2-4, and ANT2-5 connected to the second RFID reader / writer 22 so as to be able to communicate with each other.

[0015] The server 600 includes a control unit 610 and a storage unit 620. The storage unit 620 includes an interference source estimation database 621.

[0016] The control unit 610 comprehensively controls the entire interference source estimation system 900, and includes a CPU (Central Processing Unit) (not shown) that reads programs and executes control processing.

[0017] The control unit 610 controls the overall operation of the interference source estimation system 900 by loading programs stored in a RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), etc. of the storage unit 620 into the RAM of the storage unit 620 and sequentially executing the programs. The control unit 610 controls the overall operation of the interference source estimation system 900 by executing various programs such as an OS (Operating System) program and application programs.

[0018] The storage unit 620 is a RAM, ROM, HDD, SSD, or the like, and stores programs executed by the control unit 610, various setting information, etc. The storage unit 620 can also store information such as the position and direction of an interference source estimated in the interference source estimation system 900 in an interference source estimation database 621. Details of the interference source estimation database 621 will be described later.

[0019] 1, only one first RFID reader / writer 12 is shown in the RFID reader / writer network itself, but this is not limited to this and one can be provided for each of antennas ANT1-1, ANT1-2, ANT1-3, and ANT1-4. Similarly, only one second RFID reader / writer 22 is shown in the RFID reader / writer network itself, but this is not limited to this and one can be provided for each of antennas ANT2-1, ANT2-2, ANT2-3, ANT2-4, and ANT2-5. Only one server 600 is shown in the interference source estimation system 900, but this is not limited to this and one can be provided for each RFID reader / writer network (first RFID reader / writer network 11, second RFID reader / writer network 21). Furthermore, although the interference source estimation system 900 is equipped with a server 600, this is not limited to this, and the server 600 may be omitted and the functions of the server 600 may be realized by each RFID reader / writer (first RFID reader / writer 12, second RFID reader / writer 22) that constitutes each RFID reader / writer network (first RFID reader / writer network 11, second RFID reader / writer network 21).

[0020] The interference source estimation system 900 shares setting information between the antennas of each RFID reader / writer (first RFID reader / writer 12, second RFID reader / writer 22) of each RFID reader / writer network (first RFID reader / writer network 11, second RFID reader / writer network 21). The setting information is information indicating parameters set for each antenna constituting each RFID reader / writer network. The setting information includes information such as the number of antennas constituting each RFID reader / writer network, the coordinates of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, and transmission direction.

[0021] The coordinates of each antenna in the setting information can be expressed in three dimensions: x, y, and z. The coordinates of each antenna in the setting information may be expressed in two dimensions: x and y, omitting the z axis, or in one dimension: x, omitting the y and z axes. Furthermore, if there is an antenna that has a moving part and whose position is determined depending on time, the time component t may be added, and the coordinates of each antenna may be expressed in four dimensions: x, y, z, and t.

[0022] Transmission power refers to the transmission power of an RFID reader / writer. For example, EIRP (Effective Isotropic Radiated Power) can be used as transmission power. EIRP is one measure of the transmission power of an RFID reader / writer, and is the virtual power that can be radiated when each antenna is isotropic, that is, when it radiates radio waves evenly in all directions. EIRP is calculated by combining the actual output power of the antenna and the gain of that antenna (antenna gain). EIRP is an index that indicates how much power is radiated in a specific direction. EIRP is calculated using the following formula (1):

[0023] EIRP = RFID reader / writer output power + antenna gain - transmission line loss...Equation (1)

[0024] The transmission power of an RFID reader / writer refers to the amount of power supplied to the antenna, antenna gain refers to how much power the antenna can radiate directionally, and transmission line loss refers to the power loss due to cables to the antenna. Using EIRP makes it possible to compare the effective radio wave radiation capabilities of different types of antennas and each RFID reader / writer network (first RFID reader / writer network 11, second RFID reader / writer network 21).

[0025] The operating frequency channel is used for communication with RFID tags (not shown). The operating frequency channels in RFID readers / writers mainly operate in the low frequency (LF), high frequency (HF), and ultra-high frequency (UHF) ranges, each with different characteristics. For example, in the UHF band, the range of 860 MHz to 960 MHz is commonly used, and multiple channels exist within this range. The operating frequency channel can be selected arbitrarily depending on national and local regulations, the operating environment, and application requirements.

[0026] The modulation method is a radio wave signal processing technology used to transmit data between an RFID reader / writer and an RFID tag. Any modulation method can be used, such as ASCII modulation (ASK), frequency shift keying (FSK), or phase shift keying (PSK).

[0027] Transmission timing refers to the control of the timing at which the antenna of the RFID reader / writer transmits radio waves (interference waves) and receives responses from tags.

[0028] The transmission direction refers to a specific direction in which an antenna connected to an RFID reader / writer emits radio waves (interference waves). The antenna used in the RFID reader / writer of this embodiment is not limited to a dipole antenna, and a directional antenna such as a patch antenna having directivity in a specific direction can also be used. Therefore, when specifying the distance and position between each antenna, the distance from each antenna to the interference source In can be estimated with greater accuracy by using an elliptical or multidimensional figure corrected for the antenna gain of each antenna, rather than a concentric circle.

[0029] Next, it will be described how the distance to the interference source In can be identified by observing interference waves from multiple antennas ANT. FIG. 2 is a diagram showing an example of observing interference waves (radio waves) from each antenna arranged in the RFID reader / writer network itself. In the embodiment shown in FIG. 2, multiple antennas ANT1-1, ANT1-2, and ANT1-3 (hereinafter referred to as "antennas ANT" unless otherwise specified) are arranged in the first RFID reader / writer network 11 provided in the first store 100, and the case will be described where interference waves with reception powers Pr1, Pr2, and Pr3 received by each antenna ANT1-1, ANT1-2, and ANT1-3 are observed. That is, the interference source estimation system 900 measures reception powers Pr1, Pr2, and Pr3 at each antenna ANT1-1, ANT1-2, and ANT1-3, respectively, based on the interference waves in the first RFID reader / writer network 11. In this embodiment, the receiving antenna gains Gr1, Gr2, and Gr3 of the receiving antennas ANT1-1, ANT1-2, and ANT1-3 and the receiving powers Pr1, Pr2, and Pr3 of the receiving antennas ANT1-1, ANT1-2, and ANT1-3 are calculated, and the positions (coordinates) of the receiving antennas ANT1-1, ANT1-2, and ANT1-3 are assumed to be known. While the embodiment illustrated in FIG. 1 focuses on the multiple antennas ANT1-1, ANT1-2, and ANT1-3 that make up the first RFID reader / writer network 11 installed in the first store 100, this is not a limitation. For example, the embodiment may also be applied to the multiple antennas ANT2-1, ANT2-2, ANT2-3, ANT2-4, and ANT2-5 that make up the second RFID reader / writer network 21 installed in the fourth store 400.

[0030] In the embodiment shown in FIG. 2(2), the distance d from the antenna ANT to the interference source In is calculated by the following formulas (2) and (3) using the Friis Transmission Equation.

[0031]

number

[0032]

number

[0033] In equations (2) and (3), Pt represents the transmission power of the interference source, and indicates the amount of power output from the interference source's antenna ANT. Gt represents the transmission antenna gain of the interference source, and indicates the degree to which the interference source's antenna ANT efficiently transmits radio waves. Pr represents the received power of the observed interference wave, and indicates the amount of power observed at the receiving antenna ANT. Gr represents the receiving antenna gain at which the interference wave is observed, and indicates the degree to which the receiving antenna ANT efficiently receives radio waves. λ represents the wavelength, and indicates the wavelength of the signal transmitted from the transmitting antenna ANT. d represents the distance from the receiving antenna ANT to the interference source In.

[0034] In order to calculate the distance d from the above equations (2) and (3), α is defined as a function of the transmission power Pt, the transmission antenna gain Gt, and the wavelength λ. The function α is expressed by the following equation (4).

[0035]

number

[0036] By substituting equation (4) into equations (2) and (3), the distance d from the receiving antenna ANT to the interference source In is calculated by the following equation (5).

[0037]

number

[0038] The location of the interference source can be identified by using multiple receiving antennas to observe interference. Specifically, to calculate the distances d1, d2, and d3 from each of the antennas ANT1-1, ANT1-2, and ANT1-3 to the interference source In, Equation (5) is applied using the received power Pr1, received power Pr2, and received power Pr3 of each of the antennas ANT1-1, ANT1-2, and ANT1-3, and the received antenna gains Gr1, Gr2, and Gr3. As a result, the distances d1, d2, and d3 from each of the antennas ANT1-1, ANT1-2, and ANT1-3 to the interference source In are calculated using the following Equations (6), (7), and (8), respectively.

[0039]

number

[0040]

number

[0041]

number

[0042] In equations (6), (7), and (8), receiving antenna gain Gr1, receiving antenna gain Gr2, and receiving antenna gain Gr3 represent the receiving antenna gains of the receiving antennas ANT1-1, ANT1-2, and ANT1-3, respectively, and Pr1, Pr2, and Pr3 represent the receiving powers of the receiving antennas ANT1-1, ANT1-2, and ANT1-3, respectively. The value of function α in equations (6), (7), and (8) can be a function in which the transmission power of the interference source is Pt and the antenna gain of the interference source is Gt. Here, since the positions (coordinates) of antennas ANT1-1, ANT1-2, and ANT1-3 are known, distances d1, d2, and d3 to the interference source In can be determined by determining α that satisfies equations (6) to (8). Here, assuming that the antenna gain of each receiving antenna is uniform in all directions, it is possible to plot an arc (with radii r1, r2, and r3) of the estimated position of the interference source centered on each receiving antenna on a map (coordinate system), and from this, it is possible to identify the position of the interference source In.

[0043] FIG. 3 is a diagram showing that the position of the interference source In can be identified by inputting different assumed values ​​to the function α. ​​In this embodiment, interference waves from the interference source are observed by each of antennas ANT1-1, ANT1-2, and ANT1-3 in the RFID reader / writer network. The positions (coordinates) of the receiving antennas ANT1-1, ANT1-2, and ANT1-3 are stored in advance in the storage unit 620 of the interference source estimation system 900. In FIG. 3, dotted lines Do1 to Do3 indicate estimated position arcs where the interference source that sent the interference waves received by each of antennas ANT1-1, ANT1-2, and ANT1-3 may exist. By measuring the interference waves by the receiving antennas ANT1-1, ANT1-2, and ANT1-3, the interference source In can be estimated from each of antennas ANT1-1, ANT1-2, and ANT1-3.

[0044] Furthermore, in order to improve the accuracy of locating the interference source In, a specific signal (hereinafter referred to as a "specific signal") may be transmitted from each of the antennas ANT1-1, ANT1-2, and ANT1-3 of the RFID reader / writer network. The specific signal to be transmitted may be an unmodulated constant power signal of any frequency. The specific signal to be transmitted may be set arbitrarily so as to comply with the regulations used in each country. The positions of the antennas ANT1-1, ANT1-2, and ANT1-3 that transmit the specific signal are stored in advance in the interference source estimation system 900.

[0045] By measuring specific signals transmitted from each of antennas ANT1-1, ANT1-2, and ANT1-3 with other antennas, it is possible to improve the accuracy of estimating the external interference source In that each of antennas ANT1-1, ANT1-2, and ANT1-3 receives. The interference source In can also be specified by the direction and distance of the interference source In and the interference wave power generated at the interference source In.

[0046] That is, a pseudo interference wave with a known transmission output and transmission antenna gain is transmitted in advance as a calibration using a fixed antenna or a handheld antenna. Then, each of antennas ANT1-1, ANT1-2, and ANT1-3 receives the pseudo interference wave transmitted from the fixed antenna or the handheld antenna. For example, antenna ANT1-1 should observe the pseudo interference wave from the position of ANT1-3 at a calculated distance of -20 dBm, but due to actual obstruction, it can be determined that the observed signal is -40 dBm in the actual environment. By measuring the reflection and obstruction of the pseudo interference wave in the actual environment taking environmental factors into account, the position of the interference source In can be corrected, thereby improving the accuracy of identifying the interference source In's location.

[0047] Depending on the environment, such as a warehouse or store, where the antennas ANT1-1, ANT1-2, and ANT1-3 that make up the RFID reader / writer network are installed, various reflecting objects may be present. The presence of these reflecting objects may make it difficult for the antennas ANT1-1, ANT1-2, and ANT1-3 to accurately estimate the location of the interference source In due to the effects of wireless multipath. Therefore, the occurrence of multipath due to reflecting objects may be determined by analyzing a specific pulse signal on the time domain and observing the difference in arrival time between the initial wave and the reflected wave of the specific signal. Based on this determination result, the presence or absence of the effects of reflection from reflecting objects can be estimated.

[0048] Fig. 3(1) is a diagram showing an example of identifying the position of the interference source In when "1" is substituted into the function α as an assumed value. As shown in Fig. 3(1), when the function α is 1, the arc of the estimated position circle of the interference source from antenna ANT1-1 (hereinafter also referred to as the "estimated interference source position circle") and the arc of the estimated interference source position circle of antenna ANT1-2 intersect at two intersection points Ia, but the arc of the estimated interference source position circle of antenna ANT1-3 does not have an intersection point Ia. For this reason, when "1" is substituted into the function α as an assumed value, the interference source In cannot be identified.

[0049] FIG. 3(2) is a diagram showing an example of identifying the position of the interference source In when "2" is substituted into the function α as an assumed value. As shown in FIG. 3(2), when the function α is 2, the arc of the interference source estimated position circle of antenna ANT1-1, the arc of the interference source estimated position circle of antenna ANT1-2, and the arc of the interference source estimated position circle of antenna ANT1-3 intersect at one intersection point Ia. This indicates that this intersection point Ia is highly likely to be the position of the interference source In. Therefore, "2" can be used as a solution to the function α, and by substituting "2" into the function α, the intersection point Ia can be identified as the position of the interference source In.

[0050] FIG. 3(3) is a diagram showing an example of identifying the position of the interference source In when "3" is substituted into the function α as an assumed value. As shown in FIG. 3(3), when the function α is 3, the arc of the interference source estimated position circle for antenna ANT1-1 and the arc of the interference source estimated position circle for antenna ANT1-2 do not intersect, while the arc of the interference source estimated position circle for antenna ANT1-1 and the arc of the interference source estimated position circle for antenna ANT1-3, and the arc of the interference source estimated position circle for antenna ANT1-2 and the arc of the interference source estimated position circle for antenna ANT1-3 intersect at two intersection points Ia. This indicates that there may be multiple interference sources In or that the assumed value of the function α is inappropriate. For this reason, when "3" is substituted into the function α as an assumed value, the interference source In cannot be identified.

[0051] As described above, in this embodiment, the position (coordinates) of the interference source In can be identified based on the positions (coordinates) of the antennas and information on the received signals. As an identification method, the interference source estimation system 900 calculates the distances d1, d2, and d3 from each of the antennas ANT1-1, ANT1-2, and ANT1-3 to the interference source In using different assumed values ​​for the function α, and plots these distances as arcs on a map (coordinates). Then, by changing the value of the function α based on the intersection Ia where these arcs intersect and identifying an appropriate assumed value, the position of the interference source In can be estimated. In the above embodiment, the function α is changed from 1 to 3, but this is not limited to this and any numerical value can be used.

[0052] The interference source estimation system 900 creates an interference source estimation database 621 indicating the position of the interference source In based on information about the estimated position (coordinates) of the interference source In. The interference source estimation system 900 stores the created interference source estimation database 621 in the storage unit 620. The interference source estimation database 621 stores information about the positions (coordinates) of the antennas ANT1-1, ANT1-2, and ANT1-3 and the position (coordinates) of the interference source In.

[0053] 3, the single intersection point Ia is identified as the position of the interference source In by substituting "2" as an assumed value for the function α, but in the actual operating environment of the antennas ANT1-1, ANT1-2, and ANT1-3, it is considered that due to measurement errors and environmental factors, it is rare for the arcs representing the distances d1, d2, and d3 to the interference source In to intersect at exactly the same intersection point Ia. For this reason, in order to identify the exact position of the interference source In, the following method 1 and / or method 2 can be used in combination.

[0054] (Method 1) For example, as Method 1, the interference source estimation system 900 calculates the positions (coordinates) of intersection points Ia of arcs of interference source estimation position circles of interference waves received by each of antennas ANT1-1, ANT1-2, and ANT1-3, and identifies a function α that minimizes the distance between the calculated intersection points Ia. To identify the function α, simultaneous equations can be used to find the coordinates of the intersection point that converges most.

[0055] Specifically, the interference source estimation system 900 draws arcs on a map (coordinates) indicating interference source estimation position circles for each of the antennas ANT1-1, ANT1-2, and ANT1-3. The interference source estimation system 900 uses the above-mentioned Friis formula to draw the interference source estimation position circles on the map (coordinates) based on the positions (coordinates), received power Pr, and receiving antenna gain Gr of each of the antennas ANT1-1, ANT1-2, and ANT1-3.

[0056] Next, the interference source estimation system 900 calculates the positions (coordinates) (x 1, y1), (x 2, y2), (x 3, The relationship between the radii r1, r2, and r3 of the arcs of the interference source estimated position circles for the antennas ANT1-1, ANT1-2, and ANT1-3 and the radii r1, r2, and r3 is expressed by the following equations (9) to (11).

[0057] (x-x1) 2 +(y-y1)2 =r1 2 ...Equation (9) (x-x2) 2 +(y-y2) 2 =r2 2 ...Equation (10) (x-x3) 2 +(y-y3) 2 =r3 2 ...Equation (11)

[0058] In equation (9), (x 1, where y1) is the position (coordinate) of antenna ANT1-1, and r1 is the radius of the interference source estimation circle for antenna ANT1-1. The same applies to equations (10) and (11). By solving the simultaneous equations of equations (9) to (11), the interference source estimation system 900 can estimate the position (coordinate) of the intersection Ia of the interference waves of each of antennas ANT1-1, ANT1-2, and ANT1-3.

[0059] The interference source estimation system 900 calculates the distance between the intersection points Ia of the estimated interference source estimated position circles, and can adopt the function α that makes the distance between the intersection points Ia the smallest (the most convergent) as the function α that indicates the most probable location of the interference source In.

[0060] (Method 2) Furthermore, if it is difficult to solve the simultaneous equations, the interference source estimation system 900 can use method 2 to use numerical calculations to change the value of function α using the control unit 610 of the server 600, and estimate the function α that minimizes the distance between the intersection points Ia formed by the arcs of the interference source estimation position circles of each antenna ANT1-1, antenna ANT1-2, and antenna ANT1-3 (converges the most) as the function α that indicates the most probable position of the interference source In.

[0061] Specifically, the interference source estimation system 900 draws arcs on a map (coordinates) indicating interference source estimation position circles for each of the antennas ANT1-1, ANT1-2, and ANT1-3. The interference source estimation system 900 uses the above-mentioned Friis formula to draw the interference source estimation position circles on the map (coordinates) based on the positions (coordinates), received power Pr, and receiving antenna gain Gr of each of the antennas ANT1-1, ANT1-2, and ANT1-3.

[0062] The interference source estimation system 900 sets an initial value for the function α. ​​This initial value can start from any value. The interference source estimation system 900 then changes the value of the function α by gradually increasing or decreasing it, and analyzes how the intersection points Ia of the interference source estimation position circles for each of the antennas ANT1-1, ANT1-2, and ANT1-3 drawn on the map (coordinate system) change during this process. Then, as a result of the analysis, the function α on which the intersection points Ia are most concentrated (converged) can be adopted as the function α that indicates the most probable location of the interference source In.

[0063] In the above-described embodiment, the transmit antenna gain Gt of each of the antennas ANT1-1, ANT1-2, and ANT1-3 is a perfect circle, i.e., an isotropic antenna or the like having uniform antenna gain in all directions. However, this is not necessarily the case. In other words, an isotropic antenna is an ideal model that simplifies the behavior of an actual antenna. In other words, in an actual embodiment, an antenna such as a patch antenna having directional antenna gain can be used. A directional antenna can transmit a strong signal in a specific direction, thereby suppressing interference more effectively than an antenna with omnidirectional gain characteristics. Therefore, when using a directional antenna, the location of the interference source In can be identified based on the gain characteristics of each of the antennas ANT1-1, ANT1-2, and ANT1-3. In this case, the above-described (Method 2) is particularly effective.

[0064] Fig. 4 is a diagram showing an example of identifying an interference source In based on a directional antenna. As shown in Fig. 4(1), the antenna ANT1-1 has a gain characteristic directed to the right side of Fig. 4. Note that the gain characteristic is not limited to the right side, and may be in any direction, as shown in Fig. 4(2).

[0065] That is, in the above-described embodiment, the interference source estimation system 900 plots the arcs representing the estimated interference source position circles of each of the antennas ANT1-1, ANT1-2, and ANT1-3 on the map (coordinate system) as perfect circles, but this is not limited to this. The interference source estimation system 900 may use the above-described Friis formula to plot the estimated interference source positions corrected based on the positions (coordinate systems) of each of the antennas ANT1-1, ANT1-2, and ANT1-3, the received power Pr, and the receiving antenna gain Gr taking directivity into account as non-concentric loops (hereinafter also referred to as "estimated interference source position loops") on the map (coordinate system). The position of the interference source In can be estimated based on the intersection Ia of these loops. An appropriate assumed value can be identified by changing the value of the function α, resulting in a more accurate estimation of the position (coordinate systems) of the interference source In taking actual measurement errors and / or environmental factors into account. The interference source estimation system 900 then creates an interference source estimation database 621 indicating the position of the interference source In based on information about the estimated position (coordinate systems) of the interference source In. The interference source estimation system 900 stores the created interference source estimation database 621 in the storage unit 620. The interference source estimation database 621 stores information on the positions (coordinates) of each of the antennas ANT1-1, ANT1-2, and ANT1-3, and the position (coordinates) of the interference source In identified by an interference source estimation position loop of the positions (coordinates) of each of the antennas ANT1-1, ANT1-2, and ANT1-3. When there are multiple RFID reader / writer networks, the interference source estimation database 621 may store, for each RFID reader / writer network, information on the positions (coordinates) of each of the antennas ANT1-1, ANT1-2, and ANT1-3, and the position (coordinates) of the interference source In identified by an interference source estimation position loop of the positions (coordinates) of each of the antennas ANT1-1, ANT1-2, and ANT1-3.

[0066] Next, an embodiment will be described in which interference waves from other than the own RFID reader / writer network are detected based on the interference source estimation database 621 and the estimated interference source is reported. Fig. 5 is a diagram showing an example in which each of antennas ANT1-1, ANT1-2, and ANT1-3 detects interference waves from other than the own RFID reader / writer network based on the interference source estimation database 621 and reports the estimated interference source In. In Fig. 5, dashed lines Da1 to Da4 indicate the distance from the estimated interference source In and the degree of interference. Da1 indicates the strongest interference caused by the interference source In, dashed line Da2 indicates the second strongest interference caused by the interference source In, dashed line Da3 indicates the third strongest interference caused by the interference source In, and dashed line Da4 indicates the fourth strongest interference caused by the interference source In.

[0067] As shown in Figure 5 (1), the interference source estimation system 900 determines whether each antenna ANT1-1, antenna ANT1-2, and antenna ANT1-3 detects interference waves from other than its own RFID reader / writer network based on information on the positions (coordinates) of each antenna ANT1-1, antenna ANT1-2, and antenna ANT1-3 stored in the interference source estimation database 621 and the position (coordinates) of the interference source In generated by interference waves at the positions (coordinates) of each antenna ANT1-1, antenna ANT1-2, and antenna ANT1-3.

[0068] When each of antennas ANT1-1, ANT1-2, and ANT1-3 detects an interference wave from a network other than its own RFID reader / writer network, the interference source estimation system 900 determines whether the strength of the detected interference wave is equal to or greater than a threshold value. The threshold value can be set arbitrarily. The threshold value is preferably set to a level at which there is a possibility of degradation of reading performance by the RFID reader / writer due to interference. By setting the threshold value to a level at which there is a possibility of degradation of reading performance due to interference, if there is a possibility of degradation of reading performance due to interference, it is possible to quickly estimate the interference source In that may be causing degradation of reading performance.

[0069] When the strength of the detected interference wave is equal to or greater than a threshold, the interference source estimation system 900 can report the estimated interference source In, as shown in Fig. 5(2). As a method of reporting, the position and / or direction of the estimated interference source In can be displayed. As a method of displaying the position of the interference source In, as shown in Fig. 5(2), the position of the interference source In can be displayed by displaying the position of the interference source In on a map (coordinates) with an icon Ic. As a method of displaying the direction of the interference source In, as shown in Fig. 5(2), the arrows Ar1, Ar2, and Ar3 pointing to the interference source In can be displayed on a map (coordinates).

[0070] Fig. 6 is a diagram showing an example of reporting an estimated interference source In on a map (coordinates) on which actual stores are arranged. In the embodiment of Fig. 6, the interference source estimation system 900 will be described as being provided in a first store 100, a second store 200, a third store 300, and a fourth store 400. The interference source estimation system 900 is made up of a plurality of antennas ANT1-1, ANT1-2, and ANT1-3 provided in the first RFID reader / writer network 11.

[0071] As shown in FIG. 6 , the interference source estimation system 900 displays an icon Ic indicating the location of the interference source In and arrows Ar1, Ar2, and Ar3 indicating the direction of the interference source In on a map (coordinates) showing the first store 100, the second store 200, the third store 300, and the fourth store 400. By viewing the icon Ic indicating the location of the interference source In and the arrows Ar1, Ar2, and Ar3 indicating the direction of the interference source In, the operator of the interference source estimation system 900 can appropriately identify the estimated location and direction of the interference source In on a picture, such as a map of the store. After identifying the location and direction of the interference source In, the operator can quickly resolve the interference by visiting the actual site configured by the RFID reader / writer network and adjusting the setting information of antennas ANT1-1, ANT1-2, and ANT1-3. Furthermore, even in the case of an unknown interference source antenna not installed by the operator (e.g., an antenna installed in a store by another company), the system can quickly identify the source and begin negotiations regarding the interference. As a result, the operator can reduce the time and effort required to resolve the cause on-site.

[0072] The presence or absence of interference waves from the interference source In may be displayed on a map (coordinates). When displaying the presence or absence of interference waves from the interference source In on a map (coordinates), the interference waves and the radio waves transmitted by the RFID reader / writer network may be displayed on the time axis. By displaying the transmitted radio waves, it is possible to determine the occurrence and frequency of readability issues due to interference.

[0073] Each RFID reader / writer network may be provided with a calibration RFID tag in advance. By determining whether the pre-installed calibration RFID tag can be read, it is possible to determine whether interference occurring in each RFID reader / writer network is a hindrance to the antennas ANT1-1, ANT1-2, and ANT1-3 that make up each RFID reader / writer network. At least one calibration RFID tag needs to be provided, and multiple tags may be provided.

[0074] 7 is a diagram showing an example of sharing setting information between RFID reader / writer networks. As shown in FIG. 7, before the setting information is shared, the first RFID reader / writer network 11 and the second RFID reader / writer network 21 only have setting information 13 for the first RFID reader / writer network and setting information 23 for the second RFID reader / writer network, respectively. In other words, each RFID reader / writer network only has setting information for its own RFID reader / writer network and does not have setting information for other RFID reader / writer networks. As shown in FIG. 7, the setting information includes information such as the number of antennas constituting each RFID reader / writer network, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, and transmission direction.

[0075] For example, when the first RFID reader / writer 12 of the first RFID reader / writer network 11 shown in FIG. 1 transmits setting information 13 of the first RFID reader / writer network, such as the number of antennas constituting the first RFID reader / writer network 11, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc., to the second RFID reader / writer network 21 (step S11), for example, the second RFID reader / writer 22 of the second RFID reader / writer network 21 shown in FIG. 1 receives the setting information 13 of the first RFID reader / writer network, such as the number of antennas constituting the first RFID reader / writer network 11, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc., transmitted from the first RFID reader / writer network 11 (step S12), and shares it within the second RFID reader / writer network 21.

[0076] Similarly, when the second RFID reader / writer 22 of the second RFID reader / writer network 21 transmits setting information 23 of the second RFID reader / writer network to the first RFID reader / writer network 11, such as the number of antennas constituting the second RFID reader / writer network 21, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc. (step S13), the first RFID reader / writer 12 of the first RFID reader / writer network 11 receives the setting information 23 of the second RFID reader / writer network transmitted from the second RFID reader / writer network 21, such as the number of antennas constituting the second RFID reader / writer network 21, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc. (step S14), and shares it within the first RFID reader / writer network 11. As a result, setting information 13 and setting information 23, such as the number of antennas constituting each antenna network, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, and transmission direction, are shared between the first RFID reader / writer network 11 and the second RFID reader / writer network 21. Between the first RFID reader / writer network 11 and the second RFID reader / writer network 21, the interference source In can be estimated based on setting information 13 and setting information 23, such as the number of antennas constituting each shared antenna network, the coordinates (x, y, z) of each antenna, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, and transmission direction.

[0077] Fig. 8 is a diagram showing an example in which antenna coordinates, transmission power, frequency channel used, and transmission timing are adjusted based on shared setting information. Fig. 9 is a diagram illustrating the positions (coordinates) of each antenna arranged in the first RFID reader / writer network 11 and the second RFID reader / writer network 21 from the setting information described in Fig. 8. In Fig. 9, for convenience of explanation in the drawing, the position (coordinates) of each antenna in the setting information is represented two-dimensionally by x and y.

[0078] Before the setting information is shared, interference occurs between antenna ANT1-2 of the first RFID reader / writer network 11 and antenna ANT2-1 of the second RFID reader / writer network 21, as shown in Fig. 8. That is, as shown in Figs. 8 and 9, the antenna coordinates (7,7,0) of antenna ANT1-2 of the first RFID reader / writer network 11 and the antenna coordinates (11,10,0) of antenna ANT2-1 are located close to each other, the same operating frequency channel (918.0 MHz) is used, and the radio waves transmitted from each antenna overlap with each other at a transmission power (30 dBm). Therefore, the radio waves transmitted from antenna ANT1-2 of the first RFID reader / writer network 11 and the radio waves transmitted from antenna ANT2-1 of the second RFID reader / writer network 21 may collide with each other, causing interference.

[0079] Therefore, the interference source estimation system 900 estimates the interference source based on the setting information of each RFID reader / writer network, and adjusts the shared setting information to prevent interference, thereby suppressing the occurrence of interference. That is, the first RFID reader / writer 12 of the first RFID reader / writer network 11 identifies information on the interference wave transmitted from the antenna ANT1-2 of the first RFID reader / writer network 11 and the interference wave transmitted from the antenna ANT2-1 of the second RFID reader / writer network 21 based on the setting information 13 of the first RFID reader / writer network 11 and the setting information 23 of the second RFID reader / writer network 21 transmitted from the second RFID reader / writer network 21, and determines the distance to the interference source based on the identified information.

[0080] Similarly, the second RFID reader / writer 22 of the second RFID reader / writer network 21 identifies information on the interference waves transmitted from the antenna ANT1-2 of the first RFID reader / writer network 11 and the interference waves transmitted from the antenna ANT2-1 of the second RFID reader / writer network 21 based on the setting information 23 of the second RFID reader / writer network 21 and the setting information 13 of the first RFID reader / writer network 11 transmitted from the first RFID reader / writer network 11, and determines the distance to the interference source based on the identified information.

[0081] In the case shown in Figure 8, the interference source estimation system 900 adjusts the frequency channel used by the antenna ANT2-1 of the second RFID reader / writer network 21 from "918.0 MHz" to "920.4 MHz" based on the setting information 13 of the first RFID reader / writer network 11 and the setting information 23 of the second RFID reader / writer network 21, thereby eliminating the overlap of the frequency channels used and avoiding interference between the antenna ANT1-2 of the first RFID reader / writer network 11 and the antenna ANT2-1 of the second RFID reader / writer network 21.

[0082] In the embodiment of FIG. 8, interference is avoided by adjusting the frequency channel in use, but this is not limited to this. Interference can be avoided by adjusting at least one or a combination of the number of antennas, the coordinates (x, y, z) of each antenna, the transmission power (EIRP, etc.), the frequency channel in use, the modulation method, the transmission timing, and the transmission direction.

[0083] Here, the overall flow of this embodiment will be explained. In this embodiment, for example, the interference source In may be a reader / writer network known to the user, or an unknown factor caused by a reader / writer network of another store or an unknown radio device brought in.

[0084] Each receiving antenna in each reader / writer network continues to receive radio waves when not transmitting radio waves, and detects signals suspected of being an interference source when receiving radio waves. This allows the interference source In, which is the source of a signal that may have a negative impact on reception quality, to be identified as a suspected interference source.

[0085] Each reader / writer network uses its receiving antenna to estimate the location and transmission level (e.g., EIRP) of the suspected interference source In. This estimation is performed by analyzing the signal strength and direction of arrival, and can reveal the approximate location and transmission characteristics of the interference source In. This provides a basis for determining whether the interference source In is within the reader / writer network itself or is external interference.

[0086] Each reader / writer network can then optionally display the location information of the estimated interference source In. For example, each reader / writer network can display the location (coordinates) of the estimated interference source on a map. This allows the operator to intuitively grasp the presence of the interference source In. As a result, the occurrence of the interference source In in each RFID reader / writer network can be estimated in real time.

[0087] Furthermore, each reader / writer network determines whether the coordinates of the interference source In correspond to a known transmitting / receiving antenna.

[0088] If the interference source In is a known transmitting / receiving antenna, attempts can be made to eliminate the interference by controlling that antenna. Specifically, by changing parameters such as the antenna output, frequency, and timing, the impact of the interference source In can be minimized.

[0089] On the other hand, if the interference source In is unknown, its existence can be made clear to system users and appropriate measures can be taken to prompt them to take appropriate action, such as removing, relocating, barriering, or suspending the use of the interference source In.

[0090] 10 to 14 are diagrams showing the transition of sharing of setting information in each RFID reader / writer network.

[0091] 10 to 14 includes a first RFID reader / writer network 11, a second RFID reader / writer network 21, and a third RFID reader / writer network 31. The first RFID reader / writer network 11 is made up of a first RFID reader / writer 12 and a plurality of antennas ANT1-1, ANT1-2, ANT1-3, and ANT1-4 connected to the first RFID reader / writer 12 and disposed in a first store 100. The second RFID reader / writer network 21 is made up of a second RFID reader / writer 22 and a plurality of antennas ANT2-1, ANT2-2, ANT2-3, ANT2-4, and ANT2-5 connected to the second RFID reader / writer 22 and disposed in a fourth store 400. The third RFID reader / writer network 31 is made up of a third RFID reader / writer 32 and a plurality of antennas ANT3-1, ANT3-2, ANT3-3, ANT3-4, ANT3-5, and ANT3-6 connected to the third RFID reader / writer 32 and placed in the fifth store 500. The first RFID reader / writer network 11, the second RFID reader / writer network 21, and the third RFID reader / writer network 31 are used in the operations of the first store 100, the fourth store 400, and the fifth store 500, respectively.

[0092] As shown in Figure 10, the first RFID reader / writer 12 connected to the first RFID reader / writer network 11 stores, as setting information 13 for the first RFID reader / writer network 11, information such as the number of antennas in the first RFID reader / writer network 11 that make up the first RFID reader / writer network 11, the coordinates (x, y, z) of each antenna ANT1-1, antenna ANT1-2, antenna ANT1-3, and antenna ANT1-4, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc. in the memory unit of the first RFID reader / writer 12.

[0093] The second RFID reader / writer 22 connected to the second RFID reader / writer network 21 stores, as setting information 23 for the second RFID reader / writer network 21, information such as the number of antennas of the second RFID reader / writer network 21 that make up the second RFID reader / writer network 21, the coordinates (x, y, z) of each antenna ANT2-1, antenna ANT2-2, antenna ANT2-3, antenna ANT2-4, and antenna ANT2-5, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc. in a memory unit of the second RFID reader / writer 22.

[0094] The third RFID reader / writer 32 connected to the third RFID reader / writer network 31 stores, as setting information 33 for the third RFID reader / writer network 31, information such as the number of antennas of the third RFID reader / writer network 31 that make up the third RFID reader / writer network 31, the coordinates (x, y, z) of each antenna ANT3-1, antenna ANT3-2, antenna ANT3-3, antenna ANT3-4, antenna ANT3-5, and antenna ANT3-6, transmission power (EIRP, etc.), frequency channel used, modulation method, transmission timing, transmission direction, etc. in the memory unit of the third RFID reader / writer 32.

[0095] That is, before the sharing of each setting information 13, setting information 23, and setting information 33, the first RFID reader / writer 12 of the first RFID reader / writer network 11, the second RFID reader / writer 22 of the second RFID reader / writer network 21, and the third RFID reader / writer 32 of the third RFID reader / writer network 31 each only holds the setting information of their own RFID reader / writer network.

[0096] As shown in Figure 11, when the third RFID reader / writer 32 of the third RFID reader / writer network 31 transmits from the antenna ANT3-1 to the second RFID reader / writer network 21 that its own RFID reader / writer network has an interference estimation function, the second RFID reader / writer 22 connected to the antenna ANT2-3 of the second RFID reader / writer network 21 recognizes this and receives the setting information 33 of the third RFID reader / writer network 31 transmitted from the third RFID reader / writer network 31.

[0097] The second RFID reader / writer 22 connected to the second RFID reader / writer network 21 stores the received setting information 33 of the third RFID reader / writer network 31 in a memory unit of the second RFID reader / writer 22 and shares it in the second RFID reader / writer network 21. This allows the second RFID reader / writer 22 of the second RFID reader / writer network 21 to estimate the interference source In between the third RFID reader / writer network 31 and the second RFID reader / writer network 21 based on the setting information 33 of the third RFID reader / writer network 31 transmitted from the third RFID reader / writer network 31 and the setting information 23 of the second RFID reader / writer network 21.

[0098] Similarly, as shown in Figure 12, when the second RFID reader / writer 22 of the second RFID reader / writer network 21 transmits from antenna ANT2-3 to the third RFID reader / writer network 31 a message that the second RFID reader / writer network has an interference estimation function, the third RFID reader / writer 32 connected to antenna ANT3-1 of the third RFID reader / writer network 31 recognizes this and receives the setting information 23 of the second RFID reader / writer network 21 transmitted from the second RFID reader / writer network 21.

[0099] The third RFID reader / writer 32 connected to the third RFID reader / writer network 31 stores the received setting information 23 of the second RFID reader / writer network 21 in a memory unit of the third RFID reader / writer 32 and shares it in the third RFID reader / writer network 31. This enables the third RFID reader / writer 32 of the third RFID reader / writer network 31 to estimate the interference source In using the setting information 23 of the second RFID reader / writer network 21 transmitted from the second RFID reader / writer network 21 and the setting information 33 of the third RFID reader / writer network 31.

[0100] Similarly, as shown in Figure 13, when the second RFID reader / writer 22 of the second RFID reader / writer network 21 transmits from antenna ANT2-1 to the first RFID reader / writer network 11 that its own RFID reader / writer network has an interference estimation function, the first RFID reader / writer 12 connected to antenna ANT1-2 of the first RFID reader / writer network 11 recognizes this and receives the setting information 23 of the second RFID reader / writer network 21 and the setting information 33 of the third RFID reader / writer network 31 transmitted from the second RFID reader / writer network 21.

[0101] The first RFID reader / writer 12 connected to the first RFID reader / writer network 11 stores the received setting information 23 of the second RFID reader / writer network 21 and setting information 33 of the third RFID reader / writer network 31 in a memory unit of the first RFID reader / writer 12 and shares the information in the first RFID reader / writer network 11. This enables the first RFID reader / writer network 11 to estimate the interference source In using the first RFID reader / writer network 11, the second RFID reader / writer network 21, and the third RFID reader / writer network 31 based on the setting information 23 of the second RFID reader / writer network 21 and the setting information 33 of the third RFID reader / writer network 31 transmitted from the second RFID reader / writer network 21, and the setting information 13 of the first RFID reader / writer network 11.

[0102] Similarly, as shown in Figure 14, when the first RFID reader / writer 12 of the first RFID reader / writer network 11 transmits from the antenna ANT1-2 to the second RFID reader / writer network 21 that the first RFID reader / writer network has an interference estimation function, the second RFID reader / writer 22 connected to the antenna ANT2-1 of the second RFID reader / writer network 21 recognizes this and receives the setting information 13 of the first RFID reader / writer network 11 transmitted from the first RFID reader / writer network 11.

[0103] The second RFID reader / writer 22 connected to the second RFID reader / writer network 21 stores the received setting information 13 of the first RFID reader / writer network 11, setting information 33 of the third RFID reader / writer network 31, and setting information 23 of the second RFID reader / writer network 21 in a memory unit of the second RFID reader / writer 22 and shares them in the second RFID reader / writer network 21. This allows the second RFID reader / writer network 21 to estimate sources of interference among the first RFID reader / writer network 11, the second RFID reader / writer network 21, and the third RFID reader / writer network 31 based on the setting information 13 of the first RFID reader / writer network 11, setting information 33 of the third RFID reader / writer network 31, and setting information 23 of the second RFID reader / writer network 21 transmitted from the first RFID reader / writer network 11. Thereafter, the first RFID reader / writer network 11, the second RFID reader / writer network 21, and the third RFID reader / writer network 31 repeatedly share the setting information 13, the setting information 23, and the setting information 33 with each other.

[0104] In the above-described embodiment, the RFID reader / writer network can periodically notify other RFID reader / writer networks that it has an interference detection function and share setting information with them, thereby enabling the RFID reader / writer network to share information for reducing interference with the other RFID reader / writer networks.

[0105] Furthermore, each RFID reader / writer network can share configuration information with other surrounding RFID reader / writer networks. This allows each RFID reader / writer network to understand potential interference caused by the antennas that make up each other's RFID reader / writer networks and share configuration information. By adjusting the transmission output and radio wave transmission timing based on the shared configuration information, it becomes possible to avoid interference between antennas. As a result, interference between the RFID reader / writer networks can be prevented or the possibility of interference occurring can be reduced.

[0106] In this embodiment, the setting information is shared by transmitting it via radio waves output from each antenna of the RFID reader / writer, but this is not limited to this. For example, each RFID reader / writer network may be connected via a wired or wireless LAN (Local Area Network), and the setting information may be shared between the RFID reader / writer networks via the LAN. This makes it possible to share large amounts of data that are difficult to transmit using an RFID reader / writer.

[0107] Furthermore, when transmitting the setting information of one RFID reader / writer network to another RFID reader / writer network, it is possible to share not only the information of the one RFID reader / writer network but also information of neighboring RFID reader / writer networks that it has previously acquired. In other words, the one RFID reader / writer network can share not only the setting information of the adjacent RFID reader / writer network, but also the setting information of the RFID reader / writer network next door to it. This allows for even more efficient interference avoidance.

[0108] In the above-described embodiment, the distance to the interference source In is estimated by changing the function α using the Friis formula, but this is not limitative. For example, each antenna constituting the RFID reader / writer network may be provided with a gyroscope and / or a compass. The gyroscope and / or compass provided in the antenna can improve the accuracy of estimating the direction and position (coordinates) of the interference source In.

[0109] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments. For example, all components shown in the embodiments can be appropriately combined. Furthermore, components from different embodiments can be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention. [Explanation of symbols]

[0110] 11: First RFID reader / writer network 12: First RFID reader / writer 13: Setting information 21: Second RFID reader / writer network 22: Second RFID reader / writer 23: Setting information 31: Third RFID reader / writer network 32: Third RFID reader / writer 33: Setting information 100: First store 200: Second store 300: 3rd store 400: 4th store 500: 5th store 600: Server 610: Control unit 620: Storage section 621: Interference source estimation database 900: Interference source estimation system ANT: Antenna ANT1-1~ANT1-4: Antennas ANT2-1~ANT2-5: Antennas ANT3-1~ANT3-6: Antennas Ia: Intersection Ic: Icon In: Interference source

Claims

1. measuring the received power received by the plurality of antennas based on interference waves in an RFID reader / writer network configured with the plurality of antennas connected to the RFID reader / writer; calculating distances from the plurality of antennas to an interference source based on the received powers measured at the plurality of antennas; creating an interference source estimation database by estimating a position of the interference source from an intersection of the distances calculated from the plurality of antennas to the interference source; The interference wave is detected based on the interference source estimation database, and when the interference strength of the detected interference wave is equal to or greater than a threshold, the interference source is notified. An interference source estimation system comprising:

2. The distance detection uses a diagram corrected by the gain of each directional antenna.

2. The interference source estimation system according to claim 1 .

3. Displays whether or not there is interference from the interference source 3. The interference source estimation system according to claim 2.

4. When displaying the presence or absence of the interference wave from the interference source on a map, the transmitted radio wave between the interference wave and the RFID reader / writer network is displayed on a time axis.

4. The interference source estimation system according to claim 3.

5. A specific signal of constant power and no modulation of any frequency is transmitted from any of the antennas in the RFID reader / writer network.

5. The interference source estimation system according to claim 4.

6. The specific signal converted into a pulse signal is analyzed on the time axis, and the difference in arrival time between the initial wave and the reflected wave of the specific signal is observed.

6. The interference source estimation system according to claim 5.

7. The RFID reader / writer network includes at least two of the RFID reader / writer networks, The RFID reader / writer networks share setting information indicating parameters set for each antenna constituting the RFID reader / writer network.

7. The interference source estimation system according to claim 1, wherein the interference source estimation system comprises: a first receiving unit;

8. The previously acquired nearby setting information is also shared in the adjacent RFID reader / writer network. The interference source estimation system according to claim 7 .

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