WO2008026260A1

WO2008026260A1 - Wireless communication apparatus, wireless communication method and program

Info

Publication number: WO2008026260A1
Application number: PCT/JP2006/317050
Authority: WO
Inventors: Takehiro Itou; Toshihisa Kamemaru
Original assignee: Mitsubishi Electric Corporation
Priority date: 2006-08-30
Filing date: 2006-08-30
Publication date: 2008-03-06
Also published as: JPWO2008026260A1; CN101449615A; JP4456652B2

Abstract

Even in a case where high-power reader/writer apparatuses are coexistent with low-power reader/writer apparatuses, the radio interference between a reader/writer apparatus and a reader/writer apparatus and that between a reader/writer apparatus and a tag can be avoided. In a reader/writer apparatus (1) for performing wireless communication with a tag (3), a transmission channel interference level setting part (1g) sets an interference level threshold as to a transmission frequency channel to be used for transmission. An adjacent channel interference level setting part (1i) sets an interference level threshold as to each of other adjacent channels in accordance with the purpose of the reader/writer apparatus using that adjacent channel. A transmission channel interference determining part (1h) determines an interference level of the transmission frequency channel to be used for transmission. An adjacent channel interference determining part (1j) determines an interference level of each of the adjacent channels. A transmission determining part (1l) compares interference level determination results with the interference level thresholds to determine whether the transmission frequency channel to be used for transmission can be actually used for transmission. A transmission/reception control part (1b) controls the transmission/reception to/from the tag based on a determination result of the transmission determining part (1l).

Description

Specification

Wireless communication apparatus, wireless communication method, and program

Technical field

TECHNICAL FIELD [0001] 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).

Background art

In recent years, RFID (Radio Frequency Identification), a non-contact recognition technology using radio waves, has been used in various fields!

In particular, the 950 MHz band RFI D, which has a longer communication distance between the reader / writer device and the tag than the conventional one, is attracting attention, and is expected to spread rapidly in the future. However, as the communication distance between the reader / writer device tags increases, the tag reading rate decreases due to radio wave interference between the RFID systems.

[0003] 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 the tag, carrier sense is performed on the transmission frequency channel, and the transmission frequency channel is in a non-transmission state (other reader / writer devices transmit, In this case, communication with the tag is performed only in the state). Thereby, radio wave interference between the reader / writer device and the reader / writer device can be avoided.

However, since the tag does not have frequency selectivity, it is impossible to judge the strength of the transmitted command from the reader / writer device of its own system or from the reader / writer device of another system. Therefore, if a command from a reader / writer device of another system is received during communication with the reader / writer device of its own system, it malfunctions.

The conventional LBT method cannot avoid such radio wave interference between reader / writer device tags.

[0004] Also, in International Publication No. W099Z59362, in a cellular radio communication system, when a high power type and a low power type radio communication system coexist, different operators (examples) For example, a method for avoiding interference with other operators by assigning a low output type to a channel adjacent to a frequency band assigned to a cellular phone operator or the like is disclosed. However, the method for avoiding interference within the frequency band of the same operator is not disclosed.

In addition to the International Publication W099Z59362, as a method for avoiding interference between the reader / writer device and the tag, the reader / writer device has a level at which interference between the tags can occur with respect to other channels other than the transmission channel. A method of performing carrier sense has been proposed.

Patent Document 1: International Publication W099Z59362

Disclosure of the invention

Problems to be solved by the invention

[0005] The conventional LBT method and the method disclosed in International Publication No. W099Z59362 cannot avoid radio wave interference between reader / writer device tags.

Also, in the currently proposed method for avoiding interference between reader / writer devices, radio wave interference can be avoided if the transmission output of each reader / writer device is the same. 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 for communication between the low-power reader / writer device and the tag. was there.

[0006] 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 reader / writer devices and reader / writer devices and between reader / writer device tags even when high-output and low-output reader / writer devices coexist.

Means for solving the problem

[0007] 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,

The plurality of communication channels are classified into a plurality of categories and for each category. An interference level setting unit for setting an interference level threshold;

An interference detector for detecting the interference level for each communication channel;

Whether the interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result And an interference level comparison unit for determining whether or not.

[0008] The interference level comparison unit,

As a result of comparing the interference level of each communication channel detected by the interference detection unit and 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. If the interference level of the category to be transmitted is equal to or lower than the threshold value, it is determined that wireless communication is performed with the communication target device.

[0009] The interference level setting unit,

The plurality of communication channels are classified into a category of transmission scheduled channels to be used for wireless communication with the communication target device and a category of adjacent channels, and a category of the transmission scheduled channels and a category of the adjacent channels. Different interference level threshold values are set.

[0010] The interference level setting unit,

The communication channels belonging to the adjacent channel category are classified into a plurality of transmission power level categories according to the transmission power levels supported by the respective communication channels.

A different interference level threshold is set for each category of the plurality of categories by the transmission power level.

[0011] The interference level setting unit includes:

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 set the 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 value of the category to which each communication channel belongs, and the interference level of each communication channel detected by the interference detection unit 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.

[0012] The interference level comparison unit comprises:

As a result of comparing the interference level of each communication channel detected by the interference detector with the first interference level threshold of the category to which each communication channel belongs, the interference level force of at least one communication channel corresponds to 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. .

[0013] The interference level comparison unit comprises:

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, the interference level of each communication channel detected by the interference detection unit is When all power is equal to or less than the second interference level threshold value of the corresponding category, it is determined that wireless communication is performed with the communication target device with limited transmission power.

[0014] The interference level setting unit includes:

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

[0015] The interference level setting unit,

The communication channels belonging to the adjacent channel category are classified into a plurality of transmission power level categories 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 each category of the plurality of transmission power level categories are set.

[0016] The wireless communication device comprises:

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

[0017] 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 and setting an interference level threshold for each category,

Detect the interference level for each communication channel,

Whether the interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result It is characterized by determining.

[0018] A program according to the present invention provides a computer 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 process for setting an interference level threshold for each category;

Interference detection processing for detecting the interference level for each communication channel;

Whether the interference level of each communication channel detected by the interference detection process is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result And an interference level comparison process for determining the frequency.

The invention's effect

[0019] 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 power category, the interference level is detected for each communication channel, and the interference level of each communication channel is determined. In order to determine whether or not to perform wireless communication by comparing the interference level threshold of the category to which each communication channel belongs, even in an environment where wireless communication devices of different categories such as high-power type and low-power type are mixed. Wireless communication can be performed while avoiding radio wave interference between wireless communication devices and between wireless communication devices and communication target devices. it can.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Embodiment 1.

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 below 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).

la is a host PC control unit that controls data transmission / reception with a host PC (Personal Computer).

lb is a transmission / reception control unit that controls data transmission / reception with a tag in response to a request from the host PC.

lc is a transmission unit that modulates and transmits a command to the tag.

Id is a transmission channel control unit and controls the transmission channel according to the transmission power to the tag.

le is a transmission power control unit, and controls transmission power to the tag.

If is a receiving unit that receives and demodulates a response with tag power.

lg is a transmission channel interference level setting unit, and sets an interference level threshold value 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.

lh is a transmission channel interference detection unit, and measures the interference level (reception level) of a transmission frequency channel scheduled to be used for transmission.

li is an adjacent channel interference level setting unit, and 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 li sets the interference level threshold for the transmission power level category (high-power reader device dedicated channel, low-power reader device dedicated channel) of the communication channel.

lj is an adjacent channel interference detection unit, which is a scheduled transmission frequency channel to be used for transmission. Measure the interference level (reception level) of all frequency channels except the channel.

11 is a transmission permission / inhibition determination unit, which compares the interference level threshold set by the transmission channel interference level setting unit lg with the interference level measured by the transmission channel interference detection unit lh, Determine if there is interference with other reader / writer devices. The reader / writer device and another reader / writer device are communicating with each other by comparing the interference level threshold set by the adjacent channel interference level setting unit li and the interference level measured by the adjacent channel interference detection unit lj. The presence or absence of interference with other tags is determined.

[0022] The transmission channel interference level setting unit lg and the adjacent channel interference level setting unit li include a plurality of communication channels in 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 is set for each category and corresponds to the interference level setting section.

The transmission channel interference detection unit lh and the adjacent channel interference detection unit lj measure and detect the interference level for each communication channel and correspond to the interference detection unit.

The transmission permission / inhibition judgment unit 11 is set by the transmission channel interference level setting unit lg and the adjacent channel interference level setting unit li and the interference level of each communication channel detected by the transmission channel interference detection unit lh and the adjacent channel interference detection unit lj. It compares the interference level threshold 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 embodiment 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. Note that the configuration of 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 shown in FIG. Also good.

In FIG. 10, the reader / writer device 1 executes a CPU 911 (Central P rocessing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microphone computer, and processor). 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 a node 912, and controls these hard drive devices. Also, 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 medium such as the ROM 913 and the magnetic disk device 920 is an example of a nonvolatile memory. These are examples of the storage device.

The communication board 915 is an example of an input device or an output device.

[0025] The communication board 915 can wirelessly communicate with the tag 3 as shown in FIG. It is also connected to the host PC. The communication board 915 may be connected to a network such as a LAN (Local Area Network), WAN (Wide Area Network), or 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 the function described as “... Unit” in the present embodiment and the following description of the embodiment. The program is read and executed by CPU911.

In the file group 924, “determination”, “calculation”, “

Information, data, signal values, variable values, and parameter forces that indicate the results of the processing described as "Comparison", "Detection of ...", "Control of ...", etc. "And" ... database "are stored as each item. "... file" and "... database" are stored in a recording medium such as a disk. 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 CPU911 via a read / write circuit, and extracted 'search''reference' comparison ' Computation 'Calculation' Processing 'Editing' Output 'Printing / Display Used for CPU operations. Extract 'Search' reference • Compare 'Calculation' Processing 'Edit' Output 'Print' Display During CPU operation, information, data, signal values, variable values and parameters are temporarily stored in main memory, registers, cache memory, buffer memory, etc. Is remembered.

In addition, the arrows in the flowcharts described below mainly indicate input / output of data and signals. Data and signal values include RAM 914 memory, magnetic disk device 920 magnetic disk, other flexible disks, compact disks, optical disks, Recorded on a recording medium such as a mini-disc or DVD. Data and signals are transmitted online via the bus 912, signal lines, cables and other transmission media.

[0027] In addition, what is described as "... 'part" in this embodiment and the following description of the embodiment is "... circuit", "... device", " It may be “device” or “means”, or may be “... step”, “... procedure”, or “... process”. That is, what is described as “... Part” may be realized by firmware stored in the ROM 913. Alternatively, it may be implemented only with software, only hardware such as element “device” substrate ”wiring, a combination of software and hardware, or a combination of firmware. Firmware and software are stored as programs on recording media such as magnetic disks, flexible disks, optical disks, compact disks, mini-discs, and DVDs. The program is read by CPU911 and executed by CPU911. In other words, the program causes the computer to function as “... Part” of the present embodiment and the embodiments described below. Alternatively, the procedure and the method of “part” of the present embodiment and the embodiment described below are executed by a computer.

As described above, the reader / writer device 1 shown in the present embodiment and the embodiment described below includes a CPU as a processing device, a memory as a storage device, a magnetic disk, etc., a communication board as an input device and an output device, and the like. As described above, the function indicated as “...” Section is realized by using these processing device, storage device, input device, and output device.

[0029] Next, when there is only a reader / writer device with the same output in a space of several tens of meters where interference between reader / writer devices and between reader / writer device tags may occur, or transmission The operation of the reader / writer device is shown in Fig. 2, Fig. 3, Fig. 4 and Fig. 5, taking the case where a high-power reader / writer device with an output of 1W and a low-power reader / writer device with a transmission output of 10mW, for example, as an example. 5 and will be described with reference to FIG.

Fig. 2 is a diagram showing 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 showing an interference level threshold for determining the presence or absence of interference for each frequency channel.

Figure 5 shows the use (category) for each frequency channel.

FIG. 6 is a flowchart showing a series of operations for avoiding interference according to the present embodiment, based on FIG. 2, FIG. 3, FIG. 4, and FIG.

[0030] As shown in FIG. 4, in the present embodiment, the assigned frequency channel is used (for transmission to a self-writer / writer device, for a high-power reader / writer device, for a low-power reader / writer device). By setting the appropriate carrier sense level, the reader / writer can be used both in an environment where only the same output type reader / writer device exists (Fig. 2) or in an environment where both high output type and low output type reader / writer devices coexist (Fig. 3). Device Interference between reader / writer devices and between reader / writer devices and tags 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.

[0032] (1) Interference level threshold setting step

First, the step of setting the interference level threshold for each frequency channel (steps S 101 to 102 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 lg, and proceeds to step S102. Note that the set interference level threshold value of the scheduled transmission channel is output to the transmission permission determination unit 11, and the transmission permission determination unit 11 holds the interference level threshold value of the transmission planned channel. In step S102, the user uses the adjacent channel interference level setting unit li to use all adjacent channels except for the transmission scheduled channel of the reader / writer device 1 (in this embodiment, chl-9 is a high-power reader / writer device). Set the interference level threshold to determine the presence or absence of interference according to the dedicated, chlO-14 dedicated to low-power reader / writer devices), and proceed to step S103. Note that the set interference level threshold value of the adjacent channel is output to the transmission availability determination unit 11, and the transmission availability determination unit 11 holds the interference level threshold value of the adjacent channel. (2) Interference level detection step (i) One transmission scheduled channel

Next, the steps (steps S103-104, 110-111 in FIG. 6) for detecting the interference level in the channel that the reader / writer apparatus 1 is scheduled to use for transmission 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 lh, and proceeds to step S104.

In step S104, the transmission permission / inhibition determination unit 11 inputs the interference level (reception level) value measured by the transmission channel interference detection unit lh, and the input interference level value and the transmission set in step S101. Compare the interference level threshold of the scheduled channel.

If it is below the threshold value, the transmission permission / inhibition determining unit 11 determines that the channel is used by any other reader / writer device, determines that the channel is a transmission channel, and proceeds to step S105. .

When the threshold value is exceeded, the transmission permission / inhibition determining unit 11 determines that the channel is in use by another reader / writer device, and that there is a possibility that interference between the reader / writer devices may occur. Proceed to

In step S110, the transmission channel interference detection unit lh 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). If the interference level is measured sequentially for the frequency channels corresponding to, and the transmission availability determination unit 11 determines that the interference level of all channels exceeds the threshold, there is a channel that can be used for transmission. Judge not to step

Proceed to S112.

Perform interference level measurements and threshold comparisons for all channels. Proceed to step SI 11.

In step SI 11, the channel is switched to the next channel for measuring the interference level, and the process proceeds to step S 103.

[0034] (3) Interference level detection step (ii) One channel dedicated to a high-power reader / writer device

Next, the step of detecting the interference level in the dedicated channel for the high-power reader / writer device (in this embodiment, chl-9) (steps S105 and 106 in FIG. 6) will be described. When the interference level of the scheduled transmission channel falls below the interference level threshold value, the transmission permission determination unit 11 determines the interference level of the dedicated channel for the high-power reader device to the adjacent channel interference detection unit lj in step S105. The adjacent channel interference detection unit lj measures the interference level (reception level) in all the high-power reader / writer device dedicated channels except the channel scheduled for transmission, and proceeds to step S106.

In step S106, the transmission availability determination unit 11 inputs the interference level (reception level) value measured by the adjacent channel interference detection unit lj, and all the input interference level values are set in step S102. Compare the interference level threshold of the dedicated channel for high-power reader / writer equipment. When all the 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 the other high-power reader / writer device communicating. 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.

[0035] (4) Interference level detection step (iii) One channel dedicated to low-power reader / writer devices

Next, the step of detecting the interference level in the channel dedicated to the low-power reader / writer device (chlO-14 in this embodiment) (steps S107-108 in FIG. 6) will be described.

When the interference level of all channels of the high-power reader device dedicated channel is below the interference level threshold value, the transmission enable / disable determining unit 11 determines that the adjacent channel interference detection unit lj is dedicated to the low-power reader device in step S107. Instructs to measure the interference level of the channel, and the adjacent channel interference detection unit lj Measure the interference level (reception level) in the channel dedicated to one writer device, and go to step S108.

In step S108, the transmission availability determination unit 11 inputs the interference level (reception level) value measured by the adjacent channel interference detection unit lj, and all the input interference level values are set in step S102. Compare the interference level threshold of the dedicated channel for the low-power reader / writer device. 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 the tag with which the other low-power reader / writer device is communicating. As a result, since the interference level is less than or equal to the threshold for all of the scheduled transmission channel, the high-power reader device dedicated channel, and the low-power reader device dedicated channel, the transmission availability determination unit 11 determines that communication with the tag is possible. Then, the process proceeds to step S109.

If even one channel exceeds the threshold value, it is determined that there is a possibility of interference between the own reader / writer device and another low-power reader / writer device communicating, and the process proceeds to step S112.

[0036] (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 le, sets the transmission channel determined in step S103-104 by the transmission channel control unit Id, and sets the transmission unit lc. Thus, communication between tags is started.

[0037] (6) Abnormal termination notification step

Next, the step of notifying the host PC of abnormal termination (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 interferes 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 la notifies the host PC 4 of the abnormal end and indicates that the inter-tag communication cannot be started. Inform. [0038] As described above, by setting an interference level threshold according to the use for each frequency channel and performing interference detection for each, not only the same output but also a high output reader / writer device and a low output type Even in a space where reader / writer devices coexist, interference between reader / writer devices and between reader / writer device tags can be avoided, and multiple RFID systems can be installed at high density.

[0039] As described above, in the present embodiment, an interference level setting unit that sets an interference level threshold value for determining the presence or absence of interference according to the use for each frequency channel, and interference detection that detects interference for each frequency channel. And a reader / writer device having a transmission / reception control unit for performing transmission / reception control with a tag based on the result of the interference detection unit.

[0040] 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 other adjacent channels. It has been explained that an interference level threshold setting unit is provided for setting an interference level threshold according to the use of a reader / writer device that uses the channel.

[0041] In this embodiment, a transmission power control unit that changes the transmission power of the reader / writer device, and a frequency channel that is used for transmission are uniquely determined according to the transmission power changed by the transmission power control unit. It has been explained that by having a transmission channel control unit and uniquely determining the available transmission power for each frequency channel, it is possible to identify the purpose of the reader / writer device that uses that channel.

[0042] In addition, the reader / writer device according to the present embodiment detects, as an interference detection unit, a transmission channel interference detection unit that detects interference of a frequency channel used for transmission, and interference of other adjacent channels. It has been described that the adjacent channel interference detection unit is provided.

[0043] Also, the reader / writer device according to the present embodiment has an interference level force of the transmission channel detected by the transmission channel interference detection unit that is equal to or lower than the interference level set by the transmission channel interference level setting unit. The interference level force of all adjacent channels detected by the channel interference detection unit The interference level set by the adjacent channel interference level setting unit has been described as having a transmission / reception control unit that performs transmission / reception control with the tag in the following cases.

[0044] Embodiment 2. In the first embodiment described above, when there is a possibility that interference with other systems may occur in the transmission scheduled channel and the adjacent channel, the inter-tag communication is not started! This is the embodiment.

Next, an embodiment of trying 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 shows a configuration example of the reader / writer device 1 according to the present embodiment.

In FIG. 7, lk is a transmission permission determination level setting unit, and when there is a possibility of interference with other systems, setting an interference level threshold for determining the possibility of interference avoidance by reducing the transmission output To do.

In the present embodiment, the transmission permission / inhibition determining unit 11 determines the interference level (reception level) measured by the transmission channel interference detection unit lh and the adjacent channel interference detection unit lj in place of the operation shown in the first embodiment. Is compared with the threshold value of the interference level set by the transmission enable / disable determination level setting unit lk, and it is determined whether the transmission is possible by avoiding interference by reducing the transmission power.

Other components are the same as those in FIG.

In the present embodiment, each of transmission channel interference level setting section lg, adjacent channel interference level setting section li, and transmission availability determination level setting section lk corresponds to an interference level setting section. The interference level threshold set by the transmission channel interference level setting unit lg and the adjacent channel interference level setting unit li 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 determination level setting unit lk 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 Corresponds to the level threshold.

[0046] Next, when there is only a reader / writer device with the same output in a space of several tens of meters where interference between reader / writer devices and between reader / writer device tags may occur, or the transmission output is as high as 1W, for example. The operation of the reader / writer device is shown in Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 8, Fig. 8, taking the case where an output reader / writer device and a low output reader / writer device with a transmission output of 10mW, for example, coexist. 9 will be used for explanation. 2, FIG. 3, FIG. 4, and FIG.

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 in the present embodiment, based on FIGS. 2, 3, 4, 5, and 8.

[0048] (1) Interference level threshold setting step

First, the steps for setting the threshold of the interference level for each frequency channel (steps S 201 to 202 in FIG. 9) will be described.

In step S201, the user of the system sets an interference level threshold for determining the presence / absence of interference in the transmission scheduled channel of the reader / writer device 1 by the transmission channel interference level setting unit lg, and proceeds to step S202.

In step S202, the adjacent channel interference level setting unit li uses all adjacent channels except the channel scheduled for transmission of the reader / writer device 1 (in this embodiment, chl-9 is used for the high-power reader / writer device, chlO-14). Set an interference level threshold value for determining the presence or absence of interference according to (for a 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.

[0049] (2) Transmission availability 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 system user sets an interference level threshold value (Fig. 8) for determining the possibility of interference avoidance by reducing the transmission power when there is a possibility of interference, by using the transmission permission determination level setting unit lk. Then, the process proceeds to step S204. The interference level threshold set by the transmission permission / inhibition determination level setting unit lk is output to the transmission permission / inhibition determining unit 11, and the transmission permission / inhibition determining unit 11 holds this interference level threshold.

[0050] (3) Interference level detection step (i) One scheduled transmission channel

Next, the interference level in the channel that the reader / writer device 1 intends to use for transmission is set. Steps to detect (Fig. 6, Steps S203-205, 210-211) 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 lh, and proceeds to step S205.

In step S205, the transmission availability determination unit 11 inputs the interference level (reception level) value measured by the transmission channel interference detection unit lh, and the input interference level value and the transmission schedule set in step S201. Compare the channel interference level threshold.

If it is below the threshold value, the transmission permission / inhibition determination unit 11 determines that the channel is not used by any other reader / writer device, determines that the channel is a transmission channel, and proceeds to step S206.

When the threshold value is exceeded, the transmission permission determination unit 11 determines that transmission is impossible because another reader / writer device is using the channel and interference between the reader / writer devices may occur, and the process proceeds to step S210. move on.

In step S210, the transmission channel interference detection unit lh 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). If the interference level is measured sequentially for the frequency channels corresponding to, and the transmission availability determination unit 11 determines that the interference level of all channels exceeds the threshold, there is a channel that can be used for transmission. It judges that it does not carry out, and progresses to step S206.

If the interference level is measured for all the channels and compared with the threshold value, the process proceeds to step S211.

In step S211, the channel is switched to the next channel for performing interference level measurement, and the flow advances to step S204.

(4) Interference level detection step (ii) Channel for exclusive use of one high-power reader / writer device Next, step for detecting the interference level in the channel dedicated for high-power reader / writer device (chl-9 in this embodiment) (Fig. 9, Step S206) will be described.

In step S206, the reader / writer device 1 uses the adjacent channel interference detection unit lj to channel all dedicated high-power type reader / writer devices except for the channel scheduled to be used for transmission. The transmission level determination unit 11 measures the interference level (reception level) in step S207, stores the measurement result, and proceeds to step S207.

[0052] (5) Interference level detection step (iii) One 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, chlO-14) (step S207 in FIG. 9) will be described.

In step S207, the reader / writer device 1 uses the adjacent channel interference detection unit lj to measure the interference level (reception level) in all the channels dedicated to the low-power type reader / writer device except for the channel scheduled to be used for transmission. The availability determining unit 11 stores the measurement result and proceeds to step S208.

[0053] (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 that there is no channel that can be used for transmission in step S210, or all interference levels in the dedicated channel for the high-power reader / writer device read in step S206, and step S202 Compared to the interference level threshold of the high-power reader / writer device set in step 1, if even one channel exceeds the threshold, or all interference in the dedicated channel for the low-power reader / writer device read in step S207 If the level and the interference level threshold value of the low-power reader / writer device set in step S202 are compared, and the threshold is exceeded even for one channel, the transmission permission / inhibition judgment unit 11 determines that the own reader / writer device and the other reader / writer device There is a possibility that interference may occur between the device and the tag that is communicating with the reader / writer device and another reader / writer device. It is determined that that, 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.

[0054] (7) Transmission permission / inhibition judgment step by reducing transmission output

Next, a step (steps S 212 to 213 in FIG. 9) for determining whether or not the communication between the tags can be avoided by reducing the transmission power will be described.

In step S212, the transmission enable / disable determination unit 11 forces the interference level threshold in step S208. The interference level of the channel exceeding the value is compared with the interference level threshold when the transmission power set in step S203 is reduced, and the process proceeds to step 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, the transmission availability determination unit 11 determines that communication with the tag 3 is impossible because interference cannot be avoided, and the process proceeds to step S215.

[0055] (8) Transmit power change 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 le decreases the transmission power, and the process proceeds to step S209.

[0056] (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 le or changed in step S214, and the transmission channel control unit Id determines in step S204 to 205 or 213. The transmission channel set is set, and the inter-tag communication is started by the transmitter lc.

[0057] (10) Abnormal termination notification step

Next, the step of notifying the host PC of abnormal termination (step S215 in Fig. 9) will be described.

In step S215, as a result of the interference level detection step (i), (ii), (iii), or the 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 due to possible interference with tags communicating with other reader / writer devices, the host PC control unit la terminates abnormally with respect to the host PC 4. To notify that communication between tags cannot be started.

[0058] As described above, by setting an interference level threshold according to the use for each frequency channel and performing interference detection for each, it is possible to achieve not only the same output but also a high output reader / writer device and a low output. Even in a space where force reader / writer devices coexist, interference between reader / writer devices and between reader / writer device tags can be avoided, and a plurality of RFID systems can be installed at high density.

If there is a possibility of interference, try to avoid interference by reducing the transmission power, and improve the tag reading performance.

[0059] Further, the reader / writer device according to the present embodiment has a transmission channel interference level force detected by the transmission channel interference detection unit that is equal to or less than the interference level set by the transmission channel interference level threshold setting unit. If the interference level of the adjacent channel detected by the adjacent channel interference detection unit is higher than the interference level set by the adjacent channel interference level threshold setting unit, the transmission power change unit decreases the transmission power and tags It has been described that a transmission / reception control unit that performs communication with the communication device is provided.

In the above embodiment, the reader / writer device is described as an example of 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 is not limited to this. The invention can be applied.

[0061] Further, in the above embodiment, the force that divides the reader / writer device into two categories of high output type and low output type, for example, the three categories of low output type, medium output type, and high output type. It may be divided into 4 or more categories.

[0062] Further, 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. Not.

Brief Description of Drawings

FIG. 1 is a diagram showing a system configuration example including a reader / writer device according to a first embodiment.

FIG. 2 is a diagram showing an example in which the same output type reader / writer device according to the first and second embodiments is present.

FIG. 3 is a diagram showing an example in which low-output / high-output reader / writer devices according to Embodiments 1 and 2 coexist.

FIG. 4 is a diagram showing an example of an interference level threshold for each frequency channel according to the first embodiment.

FIG. 5 is a diagram showing a use (category) for each frequency channel according to the first embodiment.

FIG. 6 is a flowchart showing an operation example of the reader / writer device according to the first embodiment. FIG. 7 is a diagram showing a system configuration example including a reader / writer device according to a second embodiment.

FIG. 8 is a diagram showing an example of an interference level threshold when transmission power is reduced according to Embodiment 2.

FIG. 9 is a flowchart showing an operation example of the reader / writer device according to the second embodiment.

FIG. 10 is a diagram showing a hardware configuration example of the reader / writer device according to the first and second embodiments. Explanation of symbols

1 Reader / writer device, la host PC control unit, lb transmission / reception control unit, lc transmission unit, Id transmission channel control unit, le transmission power control unit, If reception unit, lg transmission channel interference level setting unit, lh transmission channel interference detection , Li adjacent channel interference level setting unit, lj adjacent channel interference detection unit, lk transmission availability determination level setting unit, 11 transmission availability determination unit, 2 antenna, 3 tag, 4 host PC.

Claims

The scope of the claims

[1] A wireless communication device that performs wireless communication with a communication target device using any one of a plurality of communication channels,

An interference level setting unit that classifies the plurality of communication channels into a plurality of categories and sets an interference level threshold for each category;

Whether the interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result And an interference level comparison unit for determining whether or not the wireless communication device is used.

[2] The interference level comparison unit

As a result of comparing the interference level of each communication channel detected by the interference detection unit and 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. 2. The wireless communication device according to claim 1, wherein the wireless communication device determines to perform wireless communication with the communication target device when the interference level is equal to or lower than a threshold value.

[3] The interference level setting unit includes:

The plurality of communication channels are classified into a category of transmission scheduled channels to be used for wireless communication with the communication target device and a category of adjacent channels, and a category of the transmission scheduled channels and a category of the adjacent channels. 2. The wireless communication apparatus according to claim 1, wherein a different interference level threshold is set between the wireless communication apparatus and the wireless communication apparatus.

[4] The interference level setting unit includes:

4. The radio communication apparatus according to claim 3, wherein a different interference level threshold is set for each category of the plurality of categories by the transmission power level.

[5] The interference level setting unit includes: 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 set the 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 value of the category to which each communication channel belongs, and the interference level of each communication channel detected by the interference detection unit 2. The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus determines whether to perform wireless communication with the communication target apparatus by comparing a second interference level threshold value of a category to which the communication channel belongs.

[6] The interference level comparison unit includes:

As a result of comparing the interference level of each communication channel detected by the interference detector with the first interference level threshold of the category to which each communication channel belongs, the interference level force of at least one communication channel corresponds to 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. The wireless communication device according to claim 5.

[7] The interference level comparison unit includes:

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, the interference level of each communication channel detected by the interference detection unit is 7. The wireless communication according to claim 6, wherein it is determined to perform wireless communication with the communication target device with limited transmission power when all powers are equal to or less than a second interference level threshold value of a corresponding category. apparatus.

[8] The interference level setting unit includes:

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

[9] The interference level setting unit includes:

9. The wireless communication apparatus according to claim 8, wherein a first interference level threshold value and a second interference level threshold value which are different between each category of the plurality of categories by transmission power level are set.

[10] The wireless communication device comprises:

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.

[11] A wireless communication method for performing wireless communication with a communication target device using any one of a plurality of communication channels,

Detect the interference level for each communication channel,

Whether the interference level of each communication channel detected by the interference detection unit is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result A wireless communication method characterized by determining whether or not.

[12] A computer that performs wireless communication with a communication target device using any one of a plurality of communication channels.

Whether the interference level of each communication channel detected by the interference detection process is compared with the interference level threshold of the category to which each communication channel belongs, and whether to perform wireless communication with the communication target device based on the comparison result A program characterized by causing an interference level comparison process for determining