JPWO2008026260A1 - Wireless communication apparatus, wireless communication method, and program - Google Patents

Abstract

Even when a high output type and a low output type reader / writer device coexist, radio wave interference between the reader / writer device and the reader / writer device and between the reader / writer device and the tag is avoided. In the reader / writer device 1 that performs wireless communication with the tag 3, the transmission channel interference level setting unit 1g sets the interference level threshold value of the scheduled transmission frequency channel to be used for transmission, and the adjacent channel interference level setting unit 1i Is set according to the use of the reader / writer device that uses each channel, the transmission channel interference detection unit 1h measures the interference level of the scheduled transmission frequency channel, and the adjacent channel interference detection unit 1j Measures the interference level of the adjacent channel, the transmission availability determination unit 1l compares the interference level measurement result with the interference level threshold value to determine whether transmission is possible in the scheduled transmission frequency channel, and the transmission / reception control unit 1b determines whether transmission is possible. Based on the determination result of the unit 11, transmission / reception control with the tag is performed.

Description

  The present invention relates to a transmission / reception control technique for a wireless communication device, and more particularly to a transmission / reception control technique for a reader / writer device that communicates with a wireless tag (hereinafter also simply referred to as a tag).

In recent years, RFID (Radio Frequency Identification), which is a non-contact recognition technology using radio waves, has been used in various fields.
In particular, 950 MHz band RFID, which has a longer communication distance between the reader / writer device and the tag than conventional ones, is attracting attention and is expected to spread rapidly in the future. However, as the communication distance between the reader / writer device and the tag becomes longer, a reduction in the tag reading rate due to radio wave interference between the RFID systems is raised as a new problem.

In order to solve this problem, the LBT (Listen Before Talk) method has been used as a standard technology in Japan and Europe.
In the LBT method, before each reader / writer device starts communication with a tag, carrier sense is performed on the transmission frequency channel, and the transmission frequency channel is in a non-transmission state (a state in which no other reader / writer device is transmitting). Only in this case, communication with the tag is performed on the transmission frequency channel. Thereby, radio wave interference between the reader / writer device and the reader / writer device can be avoided.
However, since the tag has no frequency selectivity, it cannot be determined whether the transmitted command is from the reader / writer device of its own system or from the reader / writer device of another system. Therefore, if a command is received from a reader / writer device of another system during communication with the reader / writer device of its own system, it malfunctions.
In the conventional LBT system, such radio wave interference between the reader / writer device and the tag cannot be avoided.

In the international publication WO99 / 59362, when a high-power type and a low-power type wireless communication system are mixed in a cell-type wireless communication system, they are assigned to different operators (for example, mobile phone operators). A method for avoiding interference with other operators by assigning a low output type to a channel adjacent to a frequency band is disclosed.
However, an interference avoidance method in the frequency band of the same operator is not disclosed.
In addition to the international publication WO99 / 59362, as a method for avoiding interference between the reader / writer device and the tag, interference between the reader / writer device and the tag occurs not only on the transmission channel but also on other channels. A method of performing carrier sense at a possible level has been proposed.
International Publication No. WO99 / 59362

The conventional LBT method and the method disclosed in International Publication WO99 / 59362 cannot avoid radio wave interference between the reader / writer device and the tag.
Also, in the currently proposed method for avoiding interference between a reader / writer device and a tag, radio wave interference can be avoided when the transmission output of each reader / writer device is the same, but reader / writer devices with different outputs, such as high When the output type (mainly stationary type) and low output type (mainly portable type) reader / writer devices coexist, the high output type senses the communication status of the low output type because the transmission power of the low output type is low. The problem is that radio waves are transmitted without being able to interfere with the tag that is communicating with the low-power reader / writer device, causing a reduction in the reading rate of the tag related to communication between the low-power reader / writer device and the tag. was there.

The main object of the present invention is to solve the above-described problems.
That is, the main purpose is to avoid radio wave interference between the reader / writer device and the reader / writer device and between the reader / writer device and the tag even when a high output type and a low output type reader / writer device coexist. To do.

A wireless communication device according to the present invention is a wireless communication device that performs wireless communication with a communication target device using any one of a plurality of communication channels,
Classifying the plurality of communication channels into a plurality of categories, and an interference level setting unit that sets an interference level threshold for each category;
An interference detector for detecting the interference level for each communication channel;
The interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold value of the category to which each communication channel belongs, and whether or not to perform wireless communication with the communication target device based on the comparison result. And an interference level comparison unit for determining.

The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the interference level threshold of the category to which each communication channel belongs, all the interference levels of each communication channel detected by the interference detection unit are supported. When it is below the interference level threshold value of the category to be determined, it is determined to perform wireless communication with the communication target device.

The interference level setting unit
The plurality of communication channels are classified into a category of scheduled transmission channels to be used for wireless communication with the communication target device and a category of adjacent channels, and between the category of scheduled transmission channels and the category of adjacent channels. And setting different interference level thresholds.

The interference level setting unit
Classifying the communication channels belonging to the category of the adjacent channel into a plurality of categories according to transmission power levels according to the transmission power levels supported by the respective communication channels;
A different interference level threshold is set for each of the plurality of categories by the transmission power level.

The interference level setting unit
For each category, a first interference level threshold when the wireless communication device performs wireless communication with the communication target device with normal transmission power, and the communication target device with transmission power limited by the wireless communication device And a second interference level threshold for wireless communication,
The interference level comparison unit
The interference level of each communication channel detected by the interference detection unit is compared with the first interference level threshold of the category to which each communication channel belongs, and the interference level of each communication channel detected by the interference detection unit and each It is characterized by comparing with the second interference level threshold value of the category to which the communication channel belongs to determine whether or not to perform wireless communication with the communication target device.

The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the first interference level threshold of the category to which each communication channel belongs, the interference level of at least one communication channel is the first of the corresponding category. When the interference level threshold is exceeded, the interference level of each communication channel detected by the interference detection unit is compared with the second interference level threshold of the category to which each communication channel belongs.

The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the second interference level threshold of the category to which each communication channel belongs, all the interference levels of each communication channel detected by the interference detection unit Is less than or equal to the second interference level threshold value of the corresponding category, it is determined that wireless communication is performed with the communication target apparatus with limited transmission power.

The interference level setting unit
The plurality of communication channels are classified into a category of scheduled transmission channels to be used for wireless communication with the communication target device and a category of adjacent channels, and between the category of scheduled transmission channels and the category of adjacent channels. A first interference level threshold and a second interference level threshold different from each other are set.

The interference level setting unit
Classifying the communication channels belonging to the category of the adjacent channel into a plurality of categories according to transmission power levels according to the transmission power levels supported by the respective communication channels;
A first interference level threshold value and a second interference level threshold value which are different between the categories of the plurality of transmission power level categories are set.

The wireless communication device
The reader / writer device performs wireless communication with a wireless tag.

A wireless communication method according to the present invention is a wireless communication method for performing wireless communication with a communication target device using any one of a plurality of communication channels,
Classifying the plurality of communication channels into a plurality of categories, setting an interference level threshold for each category,
Detect the interference level for each communication channel,
The interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold value of the category to which each communication channel belongs, and whether or not to perform wireless communication with the communication target device based on the comparison result. It is characterized by determining.

The program according to the present invention uses any one of a plurality of communication channels in a computer that performs wireless communication with a communication target device.
Classifying the plurality of communication channels into a plurality of categories, and an interference level setting process for setting an interference level threshold for each category;
Interference detection processing for detecting the interference level for each communication channel;
Compare the interference level of each communication channel detected by the interference detection process with the interference level threshold of the category to which each communication channel belongs, and based on the comparison result, whether to perform wireless communication with the communication target device. The interference level comparison process to be determined is executed.

  According to the present invention, a plurality of communication channels are classified into a plurality of categories, an interference level threshold is set for each category, the interference level is detected for each communication channel, the interference level of each communication channel, and each communication channel In order to determine whether or not to perform wireless communication by comparing the interference level threshold of the category to which the device belongs, even in an environment where wireless communication devices of different categories such as high output type and low output type are mixed, In addition, radio communication can be performed while avoiding radio wave interference between the radio communication device and the communication target device.

Embodiment 1 FIG.
As an embodiment of the present invention, a reader / writer device that performs communication with a tag only when interference levels in all frequency channels are lower than a threshold value will be described with reference to the drawings.

FIG. 1 shows a configuration example of a reader / writer device.
In FIG. 1, reference numeral 1 denotes a reader / writer device (wireless communication device).
A host PC control unit 1a controls data transmission / reception with a host PC (Personal Computer).
A transmission / reception control unit 1b controls data transmission / reception with a tag in response to a request from the host PC.
Reference numeral 1c denotes a transmission unit that modulates and transmits a command to the tag.
Reference numeral 1d denotes a transmission channel control unit that controls the transmission channel according to the transmission power to the tag.
1e is a transmission power control unit, which controls transmission power to the tag.
If is a receiving unit, it receives and demodulates the response from the tag.
Reference numeral 1g denotes a transmission channel interference level setting unit, which sets an interference level threshold for determining the presence or absence of interference in a scheduled transmission frequency channel (hereinafter also referred to as a transmission scheduled channel) to be used for transmission.
Reference numeral 1h denotes a transmission channel interference detection unit, which measures the interference level (reception level) of the transmission frequency channel scheduled to be used for transmission.
Reference numeral 1i denotes an adjacent channel interference level setting unit, which sets an interference level threshold value for determining the presence or absence of interference in all frequency channels except the scheduled transmission frequency channel to be used for transmission. The adjacent channel interference level setting unit 1i sets an interference level threshold value for a transmission power level category (a channel dedicated to a high-power reader device, a channel dedicated to a low-power reader device).
Reference numeral 1j denotes an adjacent channel interference detection unit that measures the interference levels (reception levels) of all frequency channels except for the scheduled transmission frequency channel to be used for transmission.
Reference numeral 11 denotes a transmission permission / inhibition determination unit that compares the interference level threshold set by the transmission channel interference level setting unit 1g with the interference level measured by the transmission channel interference detection unit 1h, so that the own reader / writer device and the like The presence or absence of interference with the reader / writer device is determined. Further, by comparing the interference level threshold set by the adjacent channel interference level setting unit 1i with the interference level measured by the adjacent channel interference detection unit 1j, the own reader / writer device and another reader / writer device are communicating. Determine if there is any interference with the tag.

The transmission channel interference level setting unit 1g and the adjacent channel interference level setting unit 1i classify a plurality of communication channels into a plurality of categories (transmission scheduled channels, channels dedicated to high-power reader devices, channels dedicated to low-power reader devices). The interference level threshold value is set for each category, which corresponds to the interference level setting unit.
The transmission channel interference detection unit 1h and the adjacent channel interference detection unit 1j measure and detect the interference level for each communication channel, and correspond to the interference detection unit.
The transmission permission / inhibition determining unit 11 is set by the transmission channel interference level setting unit 1g and the adjacent channel interference level setting unit 1i detected by the transmission channel interference detection unit 1h and the adjacent channel interference detection unit 1j. It compares with the interference level threshold value of the category to which each communication channel belongs, and determines whether or not to perform wireless communication with the tag based on the comparison result, and corresponds to an interference level comparison unit.

In FIG. 1, reference numeral 2 denotes an antenna that transmits and receives radio waves.
Reference numeral 3 denotes a tag (communication target device) that communicates with the reader / writer device 1.
A host PC 4 controls the reader / writer device 1.

Next, a hardware configuration example of the reader / writer device 1 shown in the present embodiment and the embodiments described below will be described.
FIG. 10 is a diagram illustrating an example of hardware resources of the reader / writer device 1 according to the present embodiment and the embodiments described below. The configuration in FIG. 10 is merely an example of the hardware configuration of the reader / writer device 1, and the hardware configuration of the reader / writer device 1 is not limited to the configuration illustrated in FIG. Also good.
In FIG. 10, the reader / writer device 1 includes a CPU 911 (also referred to as a central processing unit, a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, and a processor) that executes a program. The CPU 911 is connected to, for example, a ROM (Read Only Memory) 913, a RAM (Random Access Memory) 914, a communication board 915, and a magnetic disk device 920 via the bus 912, and controls these hardware devices. Further, instead of the magnetic disk device 920, a storage device such as a flash memory, an optical disk device, or a memory card read / write device may be used.
The RAM 914 is an example of a volatile memory. The storage media such as the ROM 913 and the magnetic disk device 920 are examples of nonvolatile memories. These are examples of the storage device.
The communication board 915 is an example of an input device or an output device.

The communication board 915 can wirelessly communicate with the tag 3 as shown in FIG. It is also connected to a host PC. The communication board 915 may be connected to a network such as a LAN (Local Area Network), a WAN (Wide Area Network), and the Internet.
The magnetic disk device 920 stores an operating system 921 (OS), a window system 922, a program group 923, and a file group 924. The programs in the program group 923 are executed by the CPU 911, the operating system 921, and the window system 922.

The program group 923 stores a program for executing a function described as “... Unit” in the present embodiment and the following description of the embodiment. The program is read and executed by the CPU 911.
In the file group 924, in the following description, “determination of...”, “Calculation of...”, “Comparison of...”, “Detection of. Information, data, signal values, variable values, and parameters indicating the results of the processing described as “...” Are stored as items of “... File” and “. “... File” and “... Database” are stored in a recording medium such as a disk or a memory. Information, data, signal values, variable values, and parameters stored in a storage medium such as a disk or memory are read out to the main memory or cache memory by the CPU 911 via a read / write circuit, and extracted, searched, referenced, compared, Used for CPU operations such as calculation, calculation, processing, editing, output, printing, and display. Information, data, signal values, variable values, and parameters are stored in the main memory, registers, cache memory, and buffers during the CPU operations of extraction, search, reference, comparison, calculation, processing, editing, output, printing, and display. It is temporarily stored in a memory or the like.
The arrows in the flowchart described below mainly indicate input / output of data and signals. The data and signal values are the memory of the RAM 914, the magnetic disk of the magnetic disk device 920, other flexible disks, compact disks, optical disks, mini-disks. It is recorded on a recording medium such as a disk or DVD. Data and signals are transmitted online via a bus 912, signal lines, cables, or other transmission media.

  In addition, what is described as “... Unit” in the present embodiment and the following description of the embodiment is “... circuit”, “... device”, “... device”. "... means", or "... step", "... procedure", "... processing". That is, what is described as “... Unit” may be realized by firmware stored in the ROM 913. Alternatively, it may be implemented only by software, or only by hardware such as elements, devices, substrates, and wirings, by a combination of software and hardware, or by a combination of firmware. Firmware and software are stored as programs in a recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, and a DVD. The program is read by the CPU 911 and executed by the CPU 911. That is, the program causes the computer to function as “... Unit” of the present embodiment and the embodiments described below. Alternatively, it causes the computer to execute the procedures and methods of “... Unit” in the present embodiment and the embodiments described below.

  As described above, the reader / writer device 1 described in this embodiment and the embodiments described below is a computer including a CPU as a processing device, a memory as a storage device, a magnetic disk, and a communication board as an input device and an output device. Yes, as described above, the function indicated as “... Unit” is realized by using these processing device, storage device, input device, and output device.

Next, when there is only a reader / writer device with the same output in a space of several tens of meters where interference between the reader / writer device and between the reader / writer device and the tag may occur, or a high output type with a transmission output of, for example, 1 W The operation of the reader / writer device will be described with reference to FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. 6, taking as an example the case where a reader / writer device and a low-power reader / writer device with a transmission output of, for example, 10 mW coexist. .
FIG. 2 is a diagram illustrating interference avoidance when only the same output (high output type) reader / writer device exists.
FIG. 3 is a diagram illustrating interference avoidance when a high-output type and a low-output type reader / writer device coexist.
FIG. 4 is a diagram illustrating an interference level threshold for determining the presence or absence of interference for each frequency channel.
FIG. 5 is a diagram showing uses (categories) for each frequency channel.
FIG. 6 is a flowchart showing a series of operations for avoiding interference in the present embodiment, based on FIGS. 2, 3, 4, and 5.

  As shown in FIG. 4, in the present embodiment, carrier sense corresponding to the use of the assigned frequency channel (for transmitting the own reader / writer device, for the high-power reader / writer device, for the low-power reader / writer device). By setting the level, the reader / writer device-reader / writer can be used in an environment where only the same output type reader / writer device exists (FIG. 2) or in an environment where a high output type and a low output type reader / writer device coexist (FIG. 3). Radio wave interference between devices and between a reader / writer device and a tag can be avoided.

  Next, an operation example (wireless communication method) of the reader / writer device 1 according to the present embodiment will be described with reference to FIG.

(1) Interference Level Threshold Setting Step First, the step of setting the interference level threshold for each frequency channel (steps S101 to S102 in FIG. 6) will be described.
In step S101, the user of the system sets an interference level threshold for determining the presence or absence of interference in the transmission scheduled channel of the reader / writer device 1 by the transmission channel interference level setting unit 1g, and the process proceeds to step S102. Note that the set interference level threshold of the scheduled transmission channel is output to the transmission permission / inhibition determining unit 11, and the transmission permission / inhibition determining unit 11 holds the interference level threshold of the scheduled transmission channel.
In step S102, the user uses the adjacent channel interference level setting unit 1i to use all adjacent channels except the channel scheduled for transmission of the reader / writer device 1 (in this embodiment, ch1-9 is dedicated to the high-power reader / writer device, An interference level threshold is set for determining the presence or absence of interference according to ch10-14 dedicated to the low-power reader / writer device, and the process proceeds to step S103. Note that the set interference level threshold value of the adjacent channel is output to the transmission permission / inhibition determination unit 11, and the transmission permission / inhibition determination unit 11 holds the interference level threshold value of the adjacent channel.

(2) Interference level detection step (i)-Channel to be transmitted-
Next, the step of detecting the interference level in the channel scheduled to be used for transmission by the reader / writer device 1 (steps S103-104 and 110-111 in FIG. 6) will be described.
In step S103, the reader / writer device 1 measures the interference level (reception level) in the transmission scheduled channel to be used for transmission by the transmission channel interference detection unit 1h, and proceeds to step S104.
In step S104, the transmission permission / inhibition determination unit 1l inputs the interference level (reception level) value measured by the transmission channel interference detection unit 1h, and the input interference level value and the transmission scheduled channel set in step S101 are input. Compare with the interference level threshold.
If it is below the threshold, the transmission permission / inhibition determining unit 11 determines that the channel is not used by any other reader / writer device, determines the channel as a transmission channel, and proceeds to step S105.
If the threshold value is exceeded, the transmission permission / inhibition determination unit 1l determines that the channel is in use by another reader / writer device and interference between the reader / writer devices may occur, so that transmission is not possible. move on.
In step S110, the transmission channel interference detection unit 1h uses the reader / writer device 1 in accordance with an instruction from the transmission permission determination unit 11 (in this embodiment, for the high-power reader / writer device or the low-power reader / writer device). When the interference level measurement unit 1l determines that the interference level of all channels exceeds the threshold value, it determines that there is no channel that can be used for transmission. The process proceeds to step S112.
When the interference level measurement and the comparison with the threshold are not performed for all channels, the process proceeds to step S111.
In step S111, the channel is switched to the channel on which the interference level is measured next, and the process proceeds to step S103.

(3) Interference level detection step (ii)-Channel dedicated to high-power reader / writer devices-
Next, the step of detecting the interference level in the high-power reader / writer device dedicated channel (ch1-9 in this embodiment) (steps S105-106 in FIG. 6) will be described.
If the interference level of the channel to be transmitted is below the interference level threshold value, the transmission permission determination unit 1l measures the interference level of the dedicated channel for the high-power reader device with respect to the adjacent channel interference detection unit 1j in step S105. The adjacent channel interference detection unit 1j measures the interference level (reception level) in all the high-power reader / writer device dedicated channels except the transmission scheduled channel, and proceeds to step S106.
In step S106, the transmission possibility determination unit 1l inputs the interference level (reception level) value measured by the adjacent channel interference detection unit 1j, all the input interference level values, and the high output set in step S102. The interference level threshold value of the dedicated channel for the reader / writer device is compared. When all the channels are below the threshold, the transmission permission determination unit 1l determines that there is no possibility of interference between the own reader / writer device and the other high-power reader / writer device communicating with the tag, Proceed to step S107.
If even one channel exceeds the threshold, it is determined that there is a possibility of interference between the own reader / writer device and the other high-power reader / writer device communicating, and the process proceeds to step S112.

(4) Interference level detection step (iii)-Channel dedicated to low-power reader / writer device-
Next, the step of detecting the interference level in the channel dedicated to the low-power reader / writer device (in this embodiment, ch10-14) (steps S107-108 in FIG. 6) will be described.
If the interference level of all channels of the high-power reader device dedicated channel is below the interference level threshold value, the transmission permission / inhibition determination unit 1l determines the low-power reader device dedicated channel to the adjacent channel interference detection unit 1j in step S107. The adjacent channel interference detection unit 1j measures the interference level (reception level) in all the low-power reader / writer device dedicated channels except the transmission scheduled channel, and the process proceeds to step S108.
In step S108, the transmission permission determination unit 1l inputs the interference level (reception level) value measured by the adjacent channel interference detection unit 1j, all the input interference level values, and the low output set in step S102. The interference level threshold value of the dedicated channel for the reader / writer device is compared. If all channels are below the threshold, the transmission permission determination unit 11 determines that there is no possibility of interference between the own reader / writer device and another low-power reader / writer device communicating with the tag. Thereby, since the interference level is less than or equal to the threshold value in all channels of the scheduled transmission channel, the high-power reader device dedicated channel, and the low-power reader device dedicated channel, the transmission permission determination unit 1l determines that communication with the tag is possible, The process proceeds to step S109.
If even one channel exceeds the threshold, it is determined that there is a possibility of interference between the own reader / writer device and the other low-power reader / writer device communicating, and the process proceeds to step S112.

(5) Intertag Communication Start Step Next, the step of starting wireless communication with the tag (step S109 in FIG. 6) will be described.
In step S109, the reader / writer device 1 sets the transmission power according to the application by the transmission power control unit 1e, sets the transmission channel determined in step S103-104 by the transmission channel control unit 1d, and sets the transmission channel by the transmission unit 1c. , Start inter-tag communication.

(6) Abnormal End Notification Step Next, the step of notifying the host PC of an abnormal end (step S112 in FIG. 6) will be described.
In step S112, as a result of the interference level detection steps (i), (ii), and (iii), the reader / writer device 1 may interfere with another reader / writer device or a tag that is communicating with another reader / writer device. If it is determined that the inter-tag communication cannot be started, the host PC control unit 1a notifies the host PC 4 of the abnormal end and notifies that the inter-tag communication cannot be started. .

  As described above, by setting interference level thresholds according to the application for each frequency channel and performing interference detection for each, not only the same output but also high output type reader / writer devices and low output type reader / writer devices coexist. Even in the space, interference between reader / writer devices and between reader / writer devices and tags can be avoided, and a plurality of RFID systems can be installed at high density.

  As described above, in the present embodiment, an interference level setting unit that sets an interference level threshold value that determines the presence or absence of interference according to an application for each frequency channel, an interference detection unit that detects interference for each frequency channel, The reader / writer device including the transmission / reception control unit that performs transmission / reception control with the tag based on the result of the interference detection unit has been described.

  In addition, the reader / writer device according to the present embodiment includes, as an interference level setting unit, a transmission channel interference level setting unit that sets an interference level threshold value of a frequency channel used for transmission, and an interference level threshold value of another adjacent channel. It has been described that the adjacent channel interference level setting unit is set according to the application of the reader / writer device that uses the channel.

  In the present embodiment, the transmission power control unit that changes the transmission power of the reader / writer device, and the transmission channel control that uniquely determines the frequency channel used for transmission according to the transmission power changed by the transmission power control unit. It has been explained that the use of the reader / writer device that uses the channel can be identified by uniquely determining the transmission power that can be used for each frequency channel.

  Also, the reader / writer device according to the present embodiment includes, as an interference detection unit, a transmission channel interference detection unit that detects interference of a frequency channel used for transmission, and an adjacent channel interference detection that detects interference of other adjacent channels. Explained that it has a part.

  Also, the reader / writer device according to the present embodiment has the interference level of the transmission channel detected by the transmission channel interference detection unit equal to or lower than the interference level set by the transmission channel interference level setting unit, and adjacent channel interference detection. When the interference level of all adjacent channels detected by the unit is equal to or lower than the interference level set by the adjacent channel interference level setting unit, the transmission / reception control unit that performs transmission / reception control with the tag has been described.

Embodiment 2. FIG.
In the first embodiment described above, the inter-tag communication is not started when there is a possibility that interference with another system may occur in the transmission scheduled channel and the adjacent channel.
Next, an embodiment that attempts to avoid interference by reducing transmission output even when interference with other systems may occur will be described with reference to the drawings.

FIG. 7 illustrates a configuration example of the reader / writer device 1 according to the present embodiment.
In FIG. 7, reference numeral 1k denotes a transmission permission / inhibition determination level setting unit, which sets an interference level threshold for determining the possibility of interference avoidance by reducing the transmission output when there is a possibility of interference with other systems. To do.
In this embodiment, in addition to the operation shown in the first embodiment, the transmission permission / inhibition determining unit 11 recognizes the interference level (reception level) measured by the transmission channel interference detection unit 1h and the adjacent channel interference detection unit 1j. The threshold value of the interference level set by the transmission enable / disable determination level setting unit 1k is compared, and it is determined whether or not transmission is possible by reducing the transmission power to avoid interference.
The other components are the same as in FIG.
In the present embodiment, each of transmission channel interference level setting unit 1g, adjacent channel interference level setting unit 1i, and transmission availability determination level setting unit 1k corresponds to an interference level setting unit. The interference level threshold set by the transmission channel interference level setting unit 1g and the adjacent channel interference level setting unit 1i is an interference level threshold when the reader / writer device 1 performs radio communication with the tag 3 with normal transmission power. Yes, corresponding to the first interference level threshold. On the other hand, the interference level threshold set by the transmission permission / inhibition determination level setting unit 1k is an interference level threshold when the reader / writer device 1 performs wireless communication with the tag 3 with limited transmission power, and the second interference level. It corresponds to a threshold value.

Next, when there is only a reader / writer device with the same output in a space of several tens of meters where interference between the reader / writer device and between the reader / writer device and the tag may occur, or a high output type with a transmission output of, for example, 1 W The operation of the reader / writer device will be described with reference to FIGS. 2, 3, 4, 5, 8, and 9, taking as an example the case where a reader / writer device and a low-power reader / writer device with a transmission output of, for example, 10 mW are mixed. I will explain.
2, FIG. 3, FIG. 4, and FIG. 5 are the same as those in the first embodiment, and thus description thereof is omitted.
FIG. 8 is a diagram illustrating an interference level threshold when transmission power is reduced.
FIG. 9 is a flowchart showing a series of operations for avoiding interference according to the present embodiment, based on FIG. 2, FIG. 3, FIG. 4, FIG.

  Next, an operation example (wireless communication method) of the reader / writer device 1 according to the present embodiment will be described with reference to FIG.

(1) Interference Level Threshold Setting Step First, the step of setting the interference level threshold for each frequency channel (steps S201-202 in FIG. 9) will be described.
In step S201, the user of the system sets an interference level threshold value for determining the presence or absence of interference in the transmission scheduled channel of the reader / writer device 1 by the transmission channel interference level setting unit 1g, and proceeds to step S202.
In step S202, the adjacent channel interference level setting unit 1i uses all the adjacent channels except the channel scheduled for transmission of the reader / writer device 1 (in this embodiment, ch1-9 is for the high-power reader / writer device, ch10-14). Set an interference level threshold value for determining the presence or absence of interference according to the low-power reader / writer device), and proceeds to step S203.
The above steps S201 and S202 are the same processes as steps S101 and S102 shown in FIG.

(2) Transmission Allowability Determination Level Setting Step Next, the step of setting an interference level threshold for determining the possibility of interference avoidance when the transmission power is reduced (step S203 in FIG. 9) will be described.
In step S203, the user of the system sets an interference level threshold (FIG. 8) for determining the possibility of interference avoidance by reducing the transmission power when there is a possibility of interference by the transmission permission determination level setting unit 1k. Then, the process proceeds to step S204. The interference level threshold set by the transmission availability determination level setting unit 1k is output to the transmission availability determination unit 11 and the transmission availability determination unit 11 holds this interference level threshold.

(3) Interference level detection step (i)-Channel to be transmitted-
Next, the step of detecting the interference level in the channel scheduled to be used for transmission by the reader / writer device 1 (steps S203-205 and 210-211 in FIG. 6) will be described.
In step S204, the reader / writer device 1 measures the interference level (reception level) in the transmission scheduled channel scheduled to be used for transmission by the transmission channel interference detection unit 1h, and proceeds to step S205.
In step S205, the transmission permission / inhibition determination unit 1l inputs the interference level (reception level) value measured by the transmission channel interference detection unit 1h, and the input interference level value and the transmission scheduled channel set in step S201. Compare with the interference level threshold.
If it is below the threshold, the transmission permission / inhibition determining unit 11 determines that the channel is not used by any other reader / writer device, determines the channel as a transmission channel, and proceeds to step S206.
If the threshold value is exceeded, the transmission permission determination unit 1l determines that the channel is in use by another reader / writer device and interference between the reader / writer devices may occur, and therefore transmission is impossible, and the process proceeds to step S210. move on.
In step S210, the transmission channel interference detection unit 1h uses the reader / writer device 1 in accordance with an instruction from the transmission permission determination unit 11 (in this embodiment, for the high-power reader / writer device or the low-power reader / writer device). When the interference level measurement unit 1l determines that the interference level of all channels exceeds the threshold value, it determines that there is no channel that can be used for transmission. The process proceeds to step S206.
If the measurement of the interference level and the comparison with the threshold are not performed for all channels, the process proceeds to step S211.
In step S211, the channel is switched to the channel on which the interference level is measured next, and the process proceeds to step S204.

(4) Interference level detection step (ii)-Channel dedicated to high-power reader / writer devices-
Next, a step (step S206 in FIG. 9) of detecting the interference level in the high-power reader / writer device dedicated channel (ch1-9 in this embodiment) will be described.
In step S206, the reader / writer device 1 uses the adjacent channel interference detection unit 1j to measure the interference levels (reception levels) in all the channels dedicated to the high-power reader / writer device except the channel scheduled to be used for transmission, and determine whether transmission is possible. The unit 1l stores the measurement result and proceeds to step S207.

(5) Interference level detection step (iii)-Channel dedicated to low-power reader / writer device-
Next, the step (step S207 in FIG. 9) of detecting the interference level in the channel dedicated to the low-power reader / writer device (ch10-14 in this embodiment) will be described.
In step S207, the reader / writer device 1 uses the adjacent channel interference detection unit 1j to measure the interference level (reception level) in all the channels dedicated to the low-power reader / writer device except the channel scheduled to be used for transmission, and determine whether transmission is possible. The unit 1l stores the measurement result and proceeds to step S208.

(6) Interference Level Confirmation Step Next, the step of confirming the interference level measured in the interference level detection step (step S208 in FIG. 9) will be described.
In step S208, if it is determined in step S210 that there is no channel that can be used for transmission, or all interference levels in the high-power reader / writer device dedicated channel read in step S206 are set in step S202. The interference level threshold value of the high-power reader / writer device is compared and if even one channel exceeds the threshold value, or all interference levels in the channel dedicated to the low-power reader / writer device read in step S207 and the step S202 If the interference level threshold of the low-power reader / writer device set in the above is compared and the threshold is exceeded even for one channel, the transmission permission / inhibition determining unit 1l determines whether it is between the own reader / writer device and the other reader / writer device or the own reader / writer device. Between a writer device and a tag communicating with another reader / writer device Interference is determined that there is likely to occur, the process proceeds to step S212.
If all channels are below the threshold, it is determined that there is no possibility of interference, and the process proceeds to step S209.

(7) Transmission Allowability Determination Step by Decreasing Transmission Output Next, a step (steps S212 to 213 in FIG. 9) for determining whether or not inter-tag communication can be avoided by reducing transmission power will be described.
In step S212, the transmission permission / inhibition determining unit 11 compares the interference level of the channel that has exceeded the interference level threshold in step S208 with the interference level threshold when the transmission power set in step S203 is reduced, The process proceeds to S213.
In step S213, if all channels are below the threshold, the transmission permission determination unit 11 determines that communication with the tag 3 is possible because interference can be avoided, and the process proceeds to step S214.
If even one channel exceeds the threshold value, the transmission availability determination unit 1l determines that communication with the tag 3 is impossible because interference cannot be avoided, and the process proceeds to step S215.

(8) Transmission Power Changing Step Next, the step of changing the transmission power (step S214 in FIG. 9) will be described.
In step S214, the transmission power control unit 1e decreases the transmission power, and the process proceeds to step S209.

(9) Intertag Communication Start Step Next, the step of starting wireless communication with the tag (step S209 in FIG. 9) will be described.
In step S209, the reader / writer device 1 sets the transmission power according to the application by the transmission power control unit 1e or changed in step S214, and the transmission determined in step S204-205 or 213 by the transmission channel control unit 1d. A channel is set and inter-tag communication is started by the transmission unit 1c.

(10) Abnormal End Notification Step Next, the step of notifying the host PC of the abnormal end (step S215 in FIG. 9) will be described.
In step S215, as a result of the interference level detection steps (i), (ii), (iii), or a result of the transmission permission / inhibition determining step by reducing the transmission output, the reader / writer device 1 is replaced with another reader / writer device or If it is determined that inter-tag communication cannot be started because there is a possibility of interference with a tag in communication with another reader / writer device, the host PC control unit 1a notifies the host PC 4 of abnormal termination. Then, it informs that inter-tag communication could not be started.

As described above, by setting interference level thresholds according to the application for each frequency channel and performing interference detection for each, not only the same output but also high output type reader / writer devices and low output type reader / writer devices coexist. Even in the space, interference between reader / writer devices and between reader / writer devices and tags can be avoided, and a plurality of RFID systems can be installed at high density.
Also, when there is a possibility of interference, it tries to avoid interference by reducing the transmission power, and realizes improvement of tag reading performance.

  In the reader / writer device according to the present embodiment, the transmission channel interference level detected by the transmission channel interference detection unit is equal to or lower than the interference level set by the transmission channel interference level threshold setting unit, and the adjacent channel When a part of the interference level of the adjacent channel detected by the channel interference detection unit is higher than the interference level set by the adjacent channel interference level threshold setting unit, the transmission power is changed by the transmission power changing unit and the tag It has been described that a transmission / reception control unit for performing communication is provided.

  In the above embodiment, the reader / writer device is described as the wireless communication device and the wireless tag is used as the communication target device. However, the present invention is not limited thereto, and the present invention can be applied to any device that performs wireless communication. It is.

  In the above embodiment, the reader / writer device is divided into two categories, ie, high output type and low output type. For example, the reader / writer device is divided into three categories: low output type, medium output type, and high output type. Alternatively, it may be divided into four or more categories.

  In the above embodiment, as an example, a high-power reader / writer device outputs 1 W and a low-power reader / writer device outputs 10 mW. However, the output value is not limited thereto.

1 is a diagram illustrating a system configuration example including a reader / writer device according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating an example in which the same output type reader / writer device according to the first and second embodiments exists. The figure which shows the example in which the low output type and the high output type reader / writer apparatus which concern on Embodiment 1, 2 are mixed. FIG. 6 is a diagram showing an example of an interference level threshold value for each frequency channel according to the first embodiment. FIG. 3 is a diagram showing a use (category) for each frequency channel according to the first embodiment. FIG. 3 is a flowchart illustrating an operation example of the reader / writer device according to the first embodiment. FIG. 4 is a diagram illustrating a system configuration example including a reader / writer device according to a second embodiment. The figure which shows the example of the interference level threshold at the time of reducing the transmission power which concerns on Embodiment 2. FIG. FIG. 6 is a flowchart showing an operation example of the reader / writer device according to the second embodiment. FIG. 3 is a diagram illustrating a hardware configuration example of a reader / writer device according to Embodiments 1 and 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Reader / writer apparatus, 1a Host PC control part, 1b Transmission / reception control part, 1c Transmission part, 1d Transmission channel control part, 1e Transmission power control part, 1f Reception part, 1g Transmission channel interference level setting part, 1h Transmission channel interference detection part 1i adjacent channel interference level setting unit, 1j adjacent channel interference detection unit, 1k transmission availability determination level setting unit, 1l transmission availability determination unit, 2 antenna, 3 tag, 4 host PC.

Claims (12)

A wireless communication device that performs wireless communication with a communication target device using any one of a plurality of communication channels,
Classifying the plurality of communication channels into a plurality of categories, and an interference level setting unit that sets an interference level threshold for each category;
An interference detector for detecting the interference level for each communication channel;
The interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold value of the category to which each communication channel belongs, and whether or not to perform wireless communication with the communication target device based on the comparison result. A wireless communication apparatus comprising: an interference level comparison unit for determining. The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the interference level threshold of the category to which each communication channel belongs, all the interference levels of each communication channel detected by the interference detection unit are supported. The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus determines to perform wireless communication with the communication target apparatus when the interference level is equal to or lower than an interference level threshold of a category to be transmitted. The interference level setting unit
The plurality of communication channels are classified into a category of scheduled transmission channels to be used for wireless communication with the communication target device and a category of adjacent channels, and between the category of scheduled transmission channels and the category of adjacent channels. The wireless communication apparatus according to claim 1, wherein different interference level thresholds are set. The interference level setting unit
Classifying the communication channels belonging to the category of the adjacent channel into a plurality of categories according to transmission power levels according to the transmission power levels supported by the respective communication channels;
4. The wireless communication apparatus according to claim 3, wherein a different interference level threshold is set between each of the plurality of categories by the transmission power level. The interference level setting unit
For each category, a first interference level threshold when the wireless communication device performs wireless communication with the communication target device with normal transmission power, and the communication target device with transmission power limited by the wireless communication device And a second interference level threshold for wireless communication,
The interference level comparison unit
The interference level of each communication channel detected by the interference detection unit is compared with the first interference level threshold of the category to which each communication channel belongs, and the interference level of each communication channel detected by the interference detection unit and each 2. The wireless communication apparatus according to claim 1, wherein a comparison is made with a second interference level threshold value of a category to which a communication channel belongs to determine whether to perform wireless communication with the communication target apparatus. The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the first interference level threshold of the category to which each communication channel belongs, the interference level of at least one communication channel is the first of the corresponding category. The interference level of each communication channel detected by the interference detection unit is compared with the second interference level threshold of the category to which each communication channel belongs when the interference level threshold of the communication channel is exceeded. 5. The wireless communication device according to 5. The interference level comparison unit
As a result of comparing the interference level of each communication channel detected by the interference detection unit with the second interference level threshold of the category to which each communication channel belongs, all the interference levels of each communication channel detected by the interference detection unit The wireless communication according to claim 6, wherein the wireless communication is determined to perform wireless communication with the communication target device with limited transmission power when the threshold is equal to or lower than a second interference level threshold value of a corresponding category. apparatus. The interference level setting unit
The plurality of communication channels are classified into a category of scheduled transmission channels to be used for wireless communication with the communication target device and a category of adjacent channels, and between the category of scheduled transmission channels and the category of adjacent channels. 6. The wireless communication apparatus according to claim 5, wherein a first interference level threshold and a second interference level threshold different from each other are set. The interference level setting unit
Classifying the communication channels belonging to the category of the adjacent channel into a plurality of categories according to transmission power levels according to the transmission power levels supported by the respective communication channels;
9. The wireless communication apparatus according to claim 8, wherein a first interference level threshold and a second interference level threshold that are different between each of the plurality of categories by transmission power level are set. The wireless communication device
The wireless communication device according to claim 1, wherein the wireless communication device is a reader / writer device that performs wireless communication with a wireless tag. A wireless communication method for performing wireless communication with a communication target device using any one of a plurality of communication channels,
Classifying the plurality of communication channels into a plurality of categories, setting an interference level threshold for each category,
Detect the interference level for each communication channel,
The interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold value of the category to which each communication channel belongs, and whether or not to perform wireless communication with the communication target device based on the comparison result. A wireless communication method characterized by determining. Using one of a plurality of communication channels, a computer that performs wireless communication with a communication target device,
Classifying the plurality of communication channels into a plurality of categories, and an interference level setting process for setting an interference level threshold for each category;
Interference detection processing for detecting the interference level for each communication channel;
Compare the interference level of each communication channel detected by the interference detection process with the interference level threshold of the category to which each communication channel belongs, and based on the comparison result, whether to perform wireless communication with the communication target device. A program for executing an interference level comparison process to be determined.

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