JP2007221347A - Communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable the number of time slots to be properly and automatically set according to an operating condition. <P>SOLUTION: It is determined whether the frequency of collisions within one round of a time slot communication exceeds the predetermined threshold of the frequency of collisions often or not. When it is determined that the frequency of collisions is high, a numerical value stored in a numerical value storage means is updated toward the direction in which the number of time slots increases. It is determined whether the number of communication media which receive information within one round of a time slot communication is often smaller than the predetermined threshold of the number of the communication media or not. When it is determined that the number of the communication media which receive information is often smaller than the threshold of the number of communication media, a numerical value stored in the numerical value storage means is updated toward the direction in which the number of time slots decreases. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a communication device that performs non-contact communication with a communication medium such as an RFID (Radio Frequency Identification) tag and reads information held in the communication medium, and in particular, communication control with a plurality of communication media. The present invention also relates to a communication apparatus using a time slot type anti-collision function.

  In recent years, there has been a small communication medium that can transmit data held in a memory or write received data in a memory by performing non-contact communication with a communication device using electromagnetic waves or radio waves. Developed and used in various fields such as distribution, logistics, transportation and security. Incidentally, the communication medium is generally called an RFID tag, a wireless tag, an IC tag, an electronic tag, or the like. The communication device is called a tag reader, a tag reader / writer, an interrogator, or the like.

  For example, in the distribution field, each product displayed on a display shelf of a store is attached with a communication medium in which information unique to the product is written, and is attached to each product using a communication device as necessary. It has been proposed to carry out inventory management, product authentication, etc. by reading and searching information on existing communication media. One of the characteristic functions of a communication system using such a communication medium is a function that allows a communication device to receive data from a plurality of communication media substantially simultaneously. As a result, when a communication medium is applied to a product, information specific to the product can be read from a plurality of products almost simultaneously and in a non-contact manner, so that work such as inventory management and product authentication can be made more efficient. (For example, refer to Patent Document 1).

  A mechanism for realizing this function is called anti-collision (collision prevention). Anti-collision is a function for controlling a response procedure of a communication medium, and there are a binary tree method and a time slot method as typical algorithms adopted in international standards. The time slot method is an access control method widely used in packet communication such as a wireless local area network (LAN) and is also called an ALOHA method.

An operation of a general time slot type anti-collision function will be described.
First, the communication apparatus designates specific bits (2 ⁰ to 2 ^Q : Q is a fixed value of ≧ 1) as a time slot for a communication medium existing in the communication area of the antenna.

  The communication medium that has received the specification of the time slot generates a random number within the bit range. For example, when the time slot is 2 bits (Q = 1), the communication medium generates any one of 2-bit random numbers [00], [01], [10], and [11]. Then, a response is returned to the communication device using a time slot at a timing that matches the generated random number.

  At this time, if only one communication medium returns a response to one time slot, the data of the communication medium is received by the communication device. However, when a plurality of communication media return responses to one time slot at the same time, a collision occurs, and data of these communication media is not received.

A random number is generated again in the communication medium that has collided. Then, a response is returned to the communication device using a time slot at a timing that matches the generated random number. By repeating such a series of processing, the communication apparatus can receive data from a plurality of communication media substantially simultaneously.
JP 2002-74286 A

  As described above, in the case of the time slot type anti-collision function, when the number of communication media existing in the antenna communication area of the communication device is large, the number of collisions can be reduced by increasing the number of time slots. Communication efficiency will be good. Conversely, when the number of communication media is small, the communication time can be shortened by reducing the number of time slots, so that the communication efficiency is good.

  However, in this type of conventional communication apparatus, the number of time slots is fixed by software installed in advance, and the number of time slots cannot be increased or decreased as appropriate. For this reason, the user selects a communication device with an appropriate number of timeslots set based on the system usage environment, etc., but good communication efficiency can be obtained if there is a misunderstanding or the usage environment changes. There was a problem that it was not possible.

  The present invention has been made based on such circumstances, and the object of the present invention is to automatically set an appropriate number of time slots according to the use situation, and always obtain good communication efficiency. A communication device is to be provided.

  The present invention allows a numerical value for determining the number of time slots to be varied in a communication apparatus that receives information from a plurality of communication media existing in a communication area of an antenna using a time slot type anti-collision function. Numerical storage means for storing, communication control means for setting time slot communication of the number of time slots determined by numerical values to one round, and repeating time slot communication in the same round from the start to the end of communication with the communication medium, and time Collision occurrence frequency determining means for determining the frequency with which the number of collision occurrences in one round of slot communication exceeds a preset collision occurrence frequency threshold, and the frequency of collision occurrences by this collision occurrence frequency determining means If it is determined that the value is high, the numerical value stored in the numerical value storage means is updated in the direction in which the number of time slots increases. It is obtained by a numerical updating means.

  In addition to the numerical value storage means and the communication control means, the present invention increases or decreases the frequency at which the number of communication media that have received information within one round of time slot communication does not reach a preset threshold for the number of communication media. If it is determined that there is a high frequency that the number of communication media that have received information by the reception frequency determination means is less than the communication medium number threshold value, the numerical value storage means stores the information. Numerical value updating means for updating the numerical value in the direction of decreasing the number of time slots.

  According to the present invention in which such a measure is taken, it is possible to automatically provide an appropriate number of time slots according to the use situation, and to provide a communication apparatus that can always obtain good communication efficiency.

The best mode for carrying out the present invention will be described below with reference to the drawings.
This embodiment is a case where the communication device of the present invention is applied to inventory management, product authentication, etc. in the distribution field. For convenience of explanation, a communication medium attached to each product is referred to as an RFID tag, and communication is performed. The device is called a tag reader.

  FIG. 1 is a block diagram showing a main configuration of a tag reader according to the present embodiment. The tag reader is composed of a portable reader body 10 and an antenna 20 attached to the reader body 10. The antenna 20 radiates a high-frequency signal as a radio wave during transmission and functions to convert the radio wave into a high-frequency signal during reception. The radio wave radiated from the antenna 20 reaches the RFID tag 30 that is attached to each product and used, and is received by each RFID tag 30. The communication area of the antenna 20 is determined by the transmission method, antenna shape, and the like.

  Each RFID tag 30 stores a unique identification number in a fixed manner. In addition, information unique to the product to which the tag is attached is stored in a rewritable manner. Each RFID tag 30 corresponds to a time slot type anti-collision function.

  The reader main body 10 is mounted with a time slot type anti-collision function, and includes an interface unit 11, a modulation unit 12, a transmission amplifier 13, a circulator 14, a reception amplifier 15, a demodulation unit 16, and a signal input / output unit (I / O). 17, a memory unit 18 and a control unit 19 for controlling each unit.

  The interface unit 11 relays data communication performed between the externally connected host device and the control unit 19. The modulation unit 12 modulates the digital transmission data given from the control unit 19 into a high frequency signal and outputs it to the transmission amplifier 13. The transmission amplifier 13 amplifies the high frequency signal modulated by the modulation unit 12 and outputs the amplified signal to the circulator 14. The circulator 14 outputs the modulated wave signal amplified by the transmission amplifier 13 to the antenna 20 side. Further, the high frequency signal received by the antenna 20 is output to the reception amplifier 15 side. The reception amplifier 15 amplifies the high frequency signal input from the circulator 14 side and outputs the amplified signal to the demodulation unit 16. The demodulator 16 demodulates the high frequency signal amplified by the reception amplifier 15, converts it to digital received data, and outputs it to the controller 19. The control unit 19 reads the memory data of the RFID tag 30 based on the digital reception data demodulated by the demodulation unit 16.

  The signal input / output unit 17 inputs an on / off signal of the reading start button 41 and notifies the control unit 19 of the signal. Further, an on / off signal is output to the reading lamp 42 under the control of the control unit 19.

  The memory unit 18 is an area for storing various setting data and variable data. In particular, as shown in FIG. 2 as a memory area according to the present invention, a random number range setting value Q storage memory 51, a random number range setting value lower limit value QMIN setting memory 52, a random number range setting value upper limit value QMAX setting memory 53, Collision occurrence number threshold x setting memory 54, read tag number threshold value n setting memory 55, collision occurrence number abnormality determination threshold value y setting memory 56, read tag number abnormality determination threshold value m setting memory 57, a first counter memory 58 for the count value Y, a second counter memory 59 for the count value M, and the like.

  Each setting memory 52, 53, 54, 55, 56, 57 is preset with a predetermined value (an integer of 1 or more: QMIN <QMAX). Incidentally, in the case of a tag reader compliant with the standard EPC (Electronic Product Code Generation) -2, the random number range set value upper limit value QMAX is [15], and the random number range set value lower limit value QMIN is [0].

Further, the storage memory 51 is stored in the range from the random number range set value lower limit value QMIN set in the setting memory 52 to the random number range set value upper limit value QMAX set in the setting memory 53 when the tag reader is shipped. An arbitrary value is set as the initial value of the random number range setting value Q. Incidentally, the random number range setting value Q is a value that determines the number of time slots (2 ^Q +1) in the anti-collision function of the time slot method. The storage memory 51 stores the random number range setting value Q in a variable manner. Here, the storage memory 51 functions as numerical value storage means for variably storing numerical values for determining the number of time slots.

  The tag reader having such a configuration is configured such that when the reading start button 41 is turned on by the user, the control unit 19 executes the processing of the procedure shown in the flowchart of FIG.

  That is, the control unit 19 starts this process in response to the ON signal of the reading start button 41 being input via the signal input / output unit 17. First, as ST (step) 1, the current random number range setting value Q is read from the storage memory 51 and stored in a work area (not shown). In ST2, the count values Y and M of the first counter memory 58 and the second counter memory 59 are reset to “0”.

  Next, the control part 19 produces | generates the digital data of the tag reading command containing the said random number range setting value Q as ST3, and outputs it to the modulation part 12. FIG. Thus, the digital data is modulated into a high frequency signal by the modulation unit 12, amplified by the transmission amplifier 13, and radiated from the antenna 20 via the circulator 14. The high frequency signal radiated from the antenna 20 is received by the RFID tag 30 existing in the communication area of the antenna 20.

The RFID tag 30 generates a voltage from the received high-frequency signal and is activated to receive a tag read command. The RFID tag 30 that has received the tag read command generates a random number with bits (0 to 2 ^Q ) within the range specified by the random number range setting value Q in the command. Then, a response is returned to the tag reader using a time slot at a timing that matches the generated random number.

On the other hand, after transmitting the tag read command, the control unit 19 performs time slot communication as ST4. That is, the number of time slots (2 ^Q +1) calculated by the random range setting value Q is transmitted in time series. When there is a response from one RFID tag 30 for one time slot, memory data is read from the RFID tag 30 by wireless communication without contact. On the other hand, when there is a response from a plurality of RFID tags 30 for one time slot, a collision occurs. Thus, when the transmission of (2 ^Q +1) time slots is completed, the control unit 19 determines that one round has passed as ST5.

  When recognizing that one round has elapsed, the control unit 19 obtains the number of collision occurrences c within that round as ST6. In ST7, it is determined whether or not the number of collision occurrences c has exceeded a collision occurrence number threshold value x preset in the setting memory 54 (collision occurrence number determination means). If it is determined that the collision occurrence count c has exceeded the collision occurrence count threshold value x, the control unit 19 increases the count value Y of the first counter memory 58 by “1” as ST8 (collision occurrence). Threshold crossing count counting means). When it is determined that the collision occurrence count c does not exceed the collision occurrence count threshold value x, the count value Y is left as it is.

  Next, the control unit 19 acquires the number r of the RFID tags 30 that have read the memory data within one round as ST9. Then, in ST10, it is determined whether or not the RFID tag number r is less than the read tag number threshold value n preset in the setting memory 55 (communication medium number determination means). If it is determined that the RFID tag number r is less than the read tag number threshold value n, the control unit 19 increases the count value M of the second counter memory 59 by “1” as ST11 ( Communication medium number threshold failure count counting means). When it is determined that the RFID tag number r is equal to or greater than the read tag number threshold value n, the count value M is left as it is.

  Next, the control unit 11 determines whether or not the count value Y of the first counter memory 58 has exceeded the collision occurrence number abnormality determination threshold value y preset in the setting memory 56 (ST12). Abnormality determination means). Here, when it is determined that the number of collisions has exceeded, it is determined that the frequency of occurrence of collision within one round of the time slot communication is higher than a preset threshold value x, and when it is determined that the number does not exceed. Determines that the frequency is low (collision frequency determination means).

  If it is determined that the frequency of collision occurrence is high, the control unit 11 resets the count value Y of the first counter memory 58 to “0” as ST13, and then stores the random number range stored in the work area as ST14. It is determined whether or not the set value Q has reached the random number range set value upper limit value QMAX set in the setting memory 53. If the random number range setting value Q has not reached the upper limit value QMAX, the random number range setting value Q in the work area is increased by “1” as ST15. If the random range setting value Q has already reached the upper limit value QMAX, the process of ST15 is not performed. If it is determined that the frequency of collision occurrence is low, the processes of ST13 to ST15 are not performed.

  Next, in ST16, the control unit 11 determines whether or not the count value M of the second counter memory 59 has exceeded the reading tag number abnormality determination threshold value m preset in the setting memory 57 (the number of communication media). Abnormality determination means). If it is determined that the number of RFID tags 30 that have received information within one round of the time slot communication is high, the frequency is determined to be less than the preset threshold value n. Is determined to be low (reception frequency determination means).

  When it is determined that the frequency that the number of RFID tags 30 that have received information is less than the preset threshold value n is high, the control unit 11 sets the count value M of the second counter memory 59 to “ After resetting to 0 ″, it is determined whether the random number range setting value Q stored in the work area as ST18 has reached the random number range setting value lower limit value QMIN set in the setting memory 52 or not. If the random number range setting value Q does not reach the lower limit value QMIN, the random number range setting value Q in the work area is decreased by “1” as ST19. When the random number range setting value Q has already reached the lower limit value QMIN, the process of ST19 is not performed. Further, when it is determined that the frequency that the number of RFID tags 30 that have received the information does not reach a preset threshold value n is low, the processes of ST17 to ST19 are not performed.

  Then, the control part 19 returns to the process of ST4, and repeats the same time slot communication (communication control means). After that, when the reading start button 41 is turned off by the user, the control unit 19 overwrites the storage memory 51 with the random number range setting value Q stored in the work area as shown in the flowchart of FIG. The random number range setting value Q in the storage memory 51 is updated. Thereby, when the random number range setting value Q in the work area has been increased in the processing of ST15 in FIG. 4, the random number range setting value Q in the storage memory 51 is increased. That is, the random number range setting value Q is updated in the direction in which the number of time slots increases. Conversely, if the random number range setting value Q in the work area has been decreased in the process of ST19 in FIG. 4, the random number range setting value Q in the storage memory 51 is decreased. That is, the random number range setting value Q is updated in the direction in which the number of time slots decreases (numerical value updating means).

  In the tag reader of this embodiment that operates in this way, the number of time slots derived from the random number range setting value Q stored in the storage memory 51 is the number of RFID tags 30 that can exist in the communication area of the antenna 20. The random number range setting value Q is automatically increased in the direction in which the number of time slots increases by actually repeating the reading operation of the RFID tag 30 under a usage environment where collisions occur frequently. Will be changed. Then, an appropriate random number range setting value Q is automatically determined under the usage environment. Thereby, since the frequency of occurrence of collision is reduced, communication efficiency is improved.

  Conversely, the number of time slots derived from the current random number range setting value Q is considerably larger than the number of RFID tags 30 that may exist in the communication area of the antenna 20, and useless time slot communication is performed. In such a usage environment, the random number range setting value Q is automatically changed in the direction of decreasing the number of time slots by actually repeating the reading operation of the RFID tag 30. Then, an appropriate random number range setting value Q is automatically determined under the usage environment. As a result, the communication time is shortened, so that the communication efficiency is also improved.

The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.
For example, in the processing procedure shown in the flowchart of FIG. 4, the sequence of steps ST12 to ST15 and the sequence of steps ST16 to ST19 may be reversed. Further, the random number range setting value Q at the time of shipment of the tag reader may be set to the random number range setting value lower limit value QMIN, and a series of processing of ST16 to ST19 may be omitted. Similarly, the random number range setting value Q at the time of tag reader shipment can be set to the random number range setting value upper limit value QMAX, and a series of processing of ST12 to ST15 can be omitted.

  In the above-described embodiment, the random number range setting value Q is increased or decreased by 1 in the processing of ST15 and ST19 in FIG. 4, but the increase / decrease range is not limited to 1, and may be increased or decreased by 2 for example. . Further, the increase / decrease width may be changed according to the difference from the random number range set value upper limit value QMAX or the random number range set value lower limit value QMIN. For example, in the process of ST15, when the difference from the current random number range setting value Q to the random number range setting value upper limit value QMAX is a certain value or more, the increase width is 2, and when the difference is less than the certain value, the increase width is set. It may be 1. Similarly, in the process of ST19, when the difference between the current random number range setting value Q and the random number range setting value lower limit value QMIN is a certain value or more, the decrease width is 2, and when the difference is less than the certain value, the decrease value is decreased. The width may be 1.

  In the above-described embodiment, the control unit 19 activates the reading start process by turning on the reading start button 41 and activates the reading end process by turning off the reading start button 41, but is connected via the interface unit 11. It is also possible to start reading in response to a read start command from the host device and start processing, and to start read end processing in response to a read end command. Therefore, the tag reader body 10 is not limited to a portable type, and may be a stationary type. Needless to say, the present invention can be applied not only to a reader-dedicated device but also to a reader / writer that can write data.

In addition, the present invention is not limited to a communication device with a communication medium called an RFID tag, a wireless tag, an IC tag, an electronic tag, or the like. It can be applied to all communication devices using the collision function.
In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, the constituent elements over different embodiments may be combined.

The block diagram which shows the principal part structure of the tag reader which is one embodiment of this invention. The schematic diagram which shows the main memory areas formed in the memory part of the tag reader. The flowchart which shows the procedure of the read completion process which the control part of the tag reader performs. The flowchart which shows the procedure of the reading start process which the control part of the tag reader performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Tag reader main body, 11 ... Interface part, 12 ... Modulation part, 13 ... Transmission amplifier, 14 ... Circulator, 15 ... Reception amplifier, 16 ... Demodulation part, 17 ... Signal input / output part, 18 ... Memory part, 19 ... Control part 20 ... antenna, 30 ... RFID tag, 41 ... reading start button.

Claims (6)

In a communication device that receives information from a plurality of communication media existing in the antenna communication area using a time slot type anti-collision function,
Numerical value storage means for variably storing numerical values for determining the number of time slots;
Communication control means for setting the time slot communication of the number of time slots determined by the numerical value to one round, and repeating the time slot communication of the same round from the start to the end of communication with the communication medium;
A collision occurrence frequency determining means for determining whether the frequency of collision occurrence within one round of the time slot communication exceeds a preset collision occurrence frequency threshold;
When it is determined by the collision occurrence frequency determining means that the frequency of collision occurrence is high, the numerical value updating means for updating the numerical value stored in the numerical value storing means in the direction in which the number of time slots increases;
A communication apparatus comprising: In a communication device that receives information from a plurality of communication media existing in the antenna communication area using a time slot type anti-collision function,
Numerical value storage means for variably storing numerical values for determining the number of time slots;
Communication control means for setting the time slot communication of the number of time slots determined by the numerical value to one round, and repeating the time slot communication of the same round from the start to the end of communication with the communication medium;
A reception frequency determining means for determining whether the number of communication media that have received information within one round of the time slot communication is less than a preset threshold for the number of communication media;
If it is determined that the number of communication media that have received information by the reception frequency determination means is high enough that the number of communication media does not reach the communication medium number threshold, the numerical value stored by the numerical value storage means is calculated as the number of time slots. Numerical value updating means for updating in a decreasing direction;
A communication apparatus comprising: In a communication device that receives information from a plurality of communication media existing in the antenna communication area using a time slot type anti-collision function,
Numerical value storage means for variably storing numerical values for determining the number of time slots;
Communication control means for setting the time slot communication of the number of time slots determined by the numerical value to one round, and repeating the time slot communication of the same round from the start to the end of communication with the communication medium;
A collision occurrence frequency determining means for determining whether the frequency of collision occurrence within one round of the time slot communication exceeds a preset collision occurrence frequency threshold;
A reception frequency determining means for determining whether the number of communication media that have received information within one round of the time slot communication is less than a preset threshold for the number of communication media;
When the collision occurrence frequency determining unit determines that the frequency of collision occurrence is high, the numerical value stored in the numerical value storage unit is updated in the direction in which the number of time slots increases, and the reception frequency determining unit updates the information. Numerical value updating means for updating the numerical value stored in the numerical value storing means in the direction of decreasing the number of time slots when it is determined that the number of received communication media is less than the communication medium number threshold value. When,
A communication apparatus comprising: The collision occurrence frequency determining means includes
A collision occurrence number determining means for determining whether or not the number of collision occurrences within the round exceeds the preset collision occurrence number threshold every time one round of the time slot communication ends;
A collision threshold transcendence count counting means for counting the number of times that the collision occurrence count within the round is determined to have exceeded the collision occurrence count threshold by the collision occurrence count determination means;
A collision occurrence number abnormality determination means for determining whether or not the count value by the collision threshold transcendence number counting means exceeds a preset collision occurrence number abnormality determination threshold,
The collision occurrence frequency abnormality determining means determines that the frequency of the collision occurrence frequency is high when it is determined that the count value by the collision threshold transcendence frequency counting means exceeds the collision occurrence frequency abnormality determination threshold value. The communication device according to claim 1 or 3. The reception frequency determining means includes
Communication medium number determination means for determining whether or not the number of communication media that have received information within a round of the time slot communication is less than a preset communication medium number threshold value, ,
A communication medium number threshold unreachable number counting means for counting the number of times that the number of communication media that have received information within the round is determined to be less than the communication medium number threshold by the communication medium number determining means; ,
The communication medium number threshold unachieved number counting means comprises a communication medium number abnormality determination means for determining whether or not the count value by the communication medium number abnormality determination threshold has been set in advance.
When the communication medium number abnormality determining means determines that the count value by the communication medium number threshold unachieved number counting means exceeds the communication medium number abnormality determination threshold, the number of communication media that have received information is The communication apparatus according to claim 2, wherein the communication apparatus determines that the frequency that does not satisfy the communication medium number threshold is high.   The communication device according to claim 1, wherein the communication medium is an RFID tag.

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