Abstract:
Contactless cards and a corresponding anti-collision coupling method are provided, where the method includes requesting that the cards transmit their unique identifiers that each include a fixed number of bytes, receiving the unique identifiers simultaneously as byte-wise positive pulses, counting the received positive pulses, and determining that more than one card responded if the number of received positive pulses exceeds the fixed number of bytes; and where the contactless cards each include a unique identifier having a number of bytes, a receiver for receiving an anti-collision command indicative of a desired identifier byte, a comparator in signal communication with the receiver for comparing the desired identifier byte with a corresponding byte of the unique identifier, and a transmitter responsive to the comparator for transmitting the unique identifier as byte-wise positive pulses if the desired identifier byte matches the corresponding byte of the unique identifier.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present disclosure relates to contactless interface devices, and more particularly relates to anti-collision coupling for contactless interface devices. An anti-collision coupling for contactless interface devices is provided.  
         [0002]     Contactless integrated circuit (IC) cards and radio frequency (RF) identification (RFID) cards are types of contactless interface devices known as contactless cards. In such contactless cards, an interface coupling or information exchange may be accomplished when the contactless cards come within range of a contactless card reader.  
         [0003]     If more than one contactless card approaches a reader at the same time, there may be confusion in the reader because of multiple concurrent signals from each card. To alleviate such confusion, an anti-collision interface coupling method is used to identify the cards that approach the reader.  
         [0004]     The anti-collision coupling methods for contactless cards are typically divided into close coupling methods and remote coupling methods, according to the desired approach distance between a card and a reader. In addition, the remote coupling methods are typically divided into proximity, vicinity and RF methods.  
         [0005]     An example of a close coupling method (CICC) is set forth in the ISO 10536 standard, as known in the art. Examples of proximity coupling methods (PICC) are set forth in the ISO/IEC 14443 standard, as also known in the art. An example of a vicinity coupling method (VICC) is set forth in the ISO/IEC 15693 standard, as further known in the art.  
         [0006]     The PICC methods defined in the ISO/IEC 14443 standard include a type A coupling method and a type B coupling method. For the type A method, the anti-collision method of the contactless cards that satisfy the ISO 14443 type A standard make use of a Unique Identification (UID), which each card has separately. When the contactless cards approach an effective region of the reader, the contactless cards each generate a signal to indicate their presence, the reader requests a card to transfer its UID, the card transfers the UID to the reader by unit, and the reader identifies the card by comparing the UID separately. The ISO 14443-A standard uses a UID method and a bit collision method, where the card is required to respond within a precise response time. Unfortunately, it takes the card a long time to respond because of the bit unit identification required within each card.  
         [0007]     For the type B method, the anti-collision method of the contactless cards that satisfy the ISO 14443 type B standard makes use of an optional value called a Pseudo Unique Proximity card Identifier (PUPI), which each card generates separately. When the contactless cards approach an effective region of the reader, the reader requests the cards to generate a random value having a set scope, the cards each generate PUPI values different from each other, and the reader selects a card by calling one of the received PUPI values. In the ISO 14443-B standard, the card must generate a random value within a fixed range and the reader must generate slots. Unfortunately, this process takes a long time because of the card operation required within each card.  
         [0008]     For the vicinity method, the anti-collision method of the contactless cards that satisfy the ISO 15693 standard makes use of a Unique Identification (UID), which each card has separately. When the contactless cards approach an effective region of the reader, the reader generates a slot having sixteen values whenever an EOF occurs. The reader requests a card to transfer a UID and recognizes the card by noting that the card responds to a slot that has the same value as its UID. The ISO 15693 standard uses a UID method, where the reader must make 16 slots. The card responds to the corresponding slot when the UID is in accord with the slot. The card compares its UID with the slots  0  to  16 , and counts the slot whenever the EOF occurs. Unfortunately, this process takes a long time because of the card operation required within each card. Thus, conventional methods for anti-collision coupling suffer from the disadvantage that a complex arithmetic operation is required within each card. The above and other drawbacks and disadvantages of the prior art are addressed by an anti-collision coupling for contactless cards in accordance with exemplary embodiments of the present disclosure.  
       SUMMARY OF THE INVENTION  
       [0009]     Contactless cards and a corresponding anti-collision coupling method are provided. An exemplary embodiment anti-collision coupling method includes requesting that contactless cards transmit their unique identifiers that each include a fixed number of bytes, receiving the unique identifiers simultaneously as byte-wise positive pulses, counting the received positive pulses, and determining that more than one card responded if the number of received positive pulses exceeds the fixed number of bytes.  
         [0010]     Exemplary embodiment contactless cards include a unique identifier having a number of bytes, a receiver for receiving an anti-collision command indicative of a desired identifier byte, a comparator in signal communication with the receiver for comparing the desired identifier byte with a corresponding byte of the unique identifier, and a transmitter responsive to the comparator for transmitting the unique identifier as byte-wise positive pulses if the desired identifier byte matches the corresponding byte of the unique identifier.  
         [0011]     These and other features of the present disclosure will become apparent from the following description of exemplary embodiments, which is to be read in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The present disclosure presents an anti-collision coupling for contactless cards in accordance with the following exemplary figures, in which:  
         [0013]      FIG. 1  shows a schematic block diagram for a communication between a contactless card and a reader;  
         [0014]      FIG. 2  shows a schematic block diagram for a communication method of contactless cards that meets the ISO/IEC 14443 type A standard;  
         [0015]      FIG. 3  shows a schematic block diagram for a communication method of contactless cards that meets the ISO/IEC 14443 type B standard;  
         [0016]      FIG. 4  shows a schematic block diagram for a communication method of contactless cards that meets the ISO/IEC 15693 standard;  
         [0017]      FIG. 5  shows a schematic block diagram for a communication method of contactless cards in accordance with an exemplary embodiment of the present disclosure;  
         [0018]      FIG. 6  shows a schematic signal diagram for transferring and receiving card identifications with positive pulses in accordance with  FIG. 5 ;  FIGS. 7 and 8  show a schematic flow diagram for an anti-collision method using card identification in accordance with  FIG. 5 ;  FIG. 9  shows a schematic signal diagram for a call command from the reader to nearby cards in accordance with  FIG. 5 ;  FIG. 10  shows a schematic signal diagram for responses from the nearby cards to the reader in accordance with  FIG. 9 ;  FIG. 11  shows a schematic signal diagram for an anti-collision command from the reader to a selected card in accordance with  FIG. 10 ;  
         [0019]      FIG. 12  shows a schematic signal diagram for a response from the selected card to the reader in accordance with  FIG. 11 ;  
         [0020]      FIG. 13  shows a schematic signal diagram for an anti-collision command from the reader to selected cards in accordance with  FIG. 10 ;  
         [0021]      FIG. 14  shows a schematic signal diagram for responses from the selected cards to the reader in accordance with  FIG. 13 ;  
         [0022]      FIG. 15  shows a schematic signal diagram for a second anti-collision command from the reader to the selected card in accordance with  FIG. 14 ;  
         [0023]      FIG. 16  shows a schematic signal diagram for a response from the selected card to the reader in accordance with  FIG. 15 ;  
         [0024]      FIG. 17  shows a schematic signal diagram for a second anti-collision command from the reader to the selected card in accordance with  FIG. 14 ; and  
         [0025]      FIG. 18  shows a schematic signal diagram for a response from the selected card to the reader in accordance with  FIG. 17 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0026]     The present disclosure relates to contactless integrated circuit (IC) cards and radio frequency (RF) interface devices (RFID), and more particularly relates to anti-collision methods for interfacing such cards and devices. An exemplary method is used to identify a number of contactless IC or RFID cards associated with a reader by using a unique identification (UID) of each of the cards when a plural number of cards approach the reader. The method identifies each card to prevent collisions between the cards without requiring complex arithmetic operations by the cards. As shown in  FIG. 1 , a conventional communication system between a reader  110  and contactless cards  120 ,  130  and  140  is indicated generally by the reference numeral  100 . If more than one contactless card is approaching the reader, confusion may arise in the reader because of concurrent signals from the cards to the reader. An anti-collision method is used to identify the cards that approach the reader in an effort to prevent such confusion.  
         [0027]     Turning to  FIG. 2 , a conventional communication method for contactless cards that satisfies the ISO/IEC 14443 type A standard is indicated generally by the reference numeral  200 . The anti-collision method  200  makes use of a Unique Identification (UID), which each card has separately. Here, the UID may be an 8-byte value using a bitwise comparison. When the contactless cards approach an effective region of the reader, the contactless cards generate a signal to alert the reader to their presence. The reader requests the card to transfer the UID at step S 200 . The card transfers the UID to the reader by unit at step S 210 . The UID is transmitted bitwise in the shape of negative pulse modulation on a center frequency using Manchester coding and bit operations. Here, the probability of a bit collision between corresponding bits from two different cards is 1 in 2 or 50%. The reader identifies the card by comparing the UID separately at step S 220 . This ISO 14443-A method uses a UID method and a bit collision method, where the card is required to meet a precise response time. Unfortunately, the bit unit identification is time consuming and bit collisions for multiple cards are obscured by the central frequency.  
         [0028]     Turning now to  FIG. 3 , a conventional communication method for contactless cards that satisfies the ISO/IEC 14443 type B standard is indicated generally by the reference numeral  300 . The anti-collision method  300  makes use of an optional value, which is called a Pseudo Unique Proximity card Identifier (PUPI) and which each card generates separately. The PUPI is a single-byte randomized value corresponding to a slot. When the contactless cards approach an effective region of the reader, the reader requests the cards to each generate a random value having a set scope at step S 300 . The cards generate a PUPI different from each other at step S 31   0 . The reader discerns the card by calling one of the PUPI identifiers at step S 320 . This ISO 14443-B method requires the card to make a random value within a fixed range and requires the reader to make slots. Unfortunately, the card operation is time consuming.  
         [0029]     As shown in  FIG. 4 , a conventional communication method for contactless cards that satisfies the ISO/IEC 15693 standard is indicated generally by the reference numeral  400 . The anti-collision method  400  makes use of a UID, which each card has separately. When the contactless cards approach an effective region of the reader, the reader generates a slot having sixteen values whenever an EOF occurs at step S 400 . The reader requests the card to transfer a UID at step S 410 . The reader discerns the card by detecting that the card responds a slot that has the same value as its UID at step S 420 . This ISO 15693 method uses a UID method and requires the reader to make 16 slots. The card must respond to the corresponding slot when the UID is in accord with the slot. Thus, the card compares its UID with the slots  0  through  16 , and counts the slot whenever the EOF occurs. Unfortunately, the card operation is time consuming.  
         [0030]     Turning to  FIG. 5 , a communication system embodiment of the present disclosure is indicated generally by the reference numeral  500 . The system  500  includes a reader  510  and contactless cards  520 ,  530  and  540 . Each contactless card has its own peculiar UID. When the contactless cards approach an effective range of the reader, the reader generates a command to call for the UIDs of the cards. The cards simultaneously transfer their respective UIDs to the reader per byte, where each byte is in the shape of a positive pulse. Unlike the negative pulses of the prior art, the positive pulses of the present embodiment prevent the values from becoming obscured. Here, the probability of a byte collision between a corresponding byte from two different cards is 1 in 256 or about 0.4%.  
         [0031]     Turning now to  FIG. 6 , signals for transferring and receiving card identifications with positive pulses are indicated generally by the reference numeral  600 . The signals  600  show how each card that received a call command transfers its UID to the reader in shape of the positive pulse. Card  1  transfers its UID  610  to the reader, Card  2  transfers its UID  620  to the reader, and Card  3  transfers its UID  630  to the reader. The reader receives the composite UID signal  640 , in which the bytes of the card UIDs are individually detectable by detecting the positive pulses.  
         [0032]     Thus, each card that receives the call command transfers its UID to the reader as positive pulses. The UID  610  of Card  1  includes a first UID byte value of 150, a second UID byte value of 180 and a third UID byte value of 180. The UID  620  of Card  2  includes a first UID byte value of 100, a second UID byte value of 80 and a third UID byte value of 80. The UID  630  of Card  3  includes a first UID byte value of 150, a second UID byte value of 120 and a third UID byte value of 120. The composite UID signal  640  at the reader includes first UID byte values of 100 and 150, second UID byte values of 80, 120 and 180, and third UID byte values of 80, 120 and 180.  
         [0033]     As shown in  FIGS. 7 and 8 , an anti-collision method using card identification is indicated generally by the reference numerals  700  and  800 . The method  700  includes a function block S 600 , at which the reader requests the cards to transfer the UIDs. That block passes control to a function block S 610 , at which each card transfers the bytes of its UID to the reader, each UID byte in the shape of a positive pulse. That block, in turn, passes control to a decision block S 620 , which determines if more than one card approaches the reader. If only one card approaches, that card is selected and control passes to a function block S 700 , at which the selected card or cards are activated and other commands from the reader may be executed. If more than one card approaches, control is passed from block S 620  to a function block S 630 , at which the reader selects a first card&#39;s first UID byte from the received first UID bytes and calls the corresponding card. That block passes control to a decision block S 640 , which determines if more than one card responds to the reader. If only one card responds, control is passed to another decision block S 650 , which determines if the reader has called all of the first UID bytes received in the composite signal. If the reader has not yet called all of the first UID bytes, control is passed back to the function block S 630 . If, on the other hand, the reader has already called all of the first UID bytes, control is passed to the function block S 700 .  
         [0034]     If the decision block S 640  determines that more than one card responds to the reader, control is passed to a function block S 660 , at which the reader selects a second UID byte from among the second UID bytes received in the composite UID and calls the corresponding card. That block passes control to a decision block S 670 , which determines if more than one card still responds to the reader. If only one card responds to the reader, the block S 670  passes control to another decision block S 680 , which determines if the reader has called all of the second UID bytes received in the composite UID signal. If the reader has not yet called all of the second UID bytes, control is passed back to the function block S 660 . If, on the other hand, the reader has already called all of the second UID bytes, control is passed to the function block S 700 .  
         [0035]     If the decision block S 670  determines that more than one card still responds to the reader, control passes to a function block S 690 . At the function block S 690 , which represents a recursive loop duplicating steps S 630  through S 650  or S 660  through S 680  for up to an nth UID byte (e.g., n=3,4,5 . . . ), the reader selects an nth UID byte from among the nth UID bytes received in the composite UID signal and calls the corresponding card. The function block S 690  passes control to the function block S 700 .  
         [0036]     Turning now to  FIG. 9 , a signal for a call command from the reader to nearby cards is indicated generally by the reference numeral  900 . Here, the signal  900  includes a UID call command. The reader  510  of  FIG. 5  generates the UID call command to call for the UIDs of the contactless cards  520 ,  530  and  540  when the contactless cards approach an effective region of the reader, where each contactless card has its own peculiar UID.  
         [0037]     The signal  900  further includes a start and an end using a Start of Frame (SOF) and an End of Frame (EOF), respectively. The reader  510  transfers the SOF and the UID call command and the SOF when the contactless cards  520 ,  530  and/or  540  approach the reader.  
         [0038]     As shown in  FIG. 10 , signals for responses from the nearby cards to the reader are indicated generally by the reference numeral  1000 . These card signals could follow the receiver signal  900  of  FIG. 9 . The cards  520 ,  530  and  540  of  FIG. 5 , which each receive the UID call command from the reader  510 , transfer their particular UIDs to the reader as the signals  1020 ,  1030  and  1040 , respectively. Each card transfers each of its UID bytes to the reader in the shape of a positive pulse. The signals  1020 , 1030  and  1040  each begin with an SOF, followed by the first through fourth UID bytes for the respective card and an EOF. Thus, the UID of Card  1  is 96h, B4h, B4h, A9h; the UID of Card  2  is 64h, 50h, 50h, 10h; and the UID of card  3  is 96h, 78h, 78h, 12h. The reader  510  recognizes whether more than one card approaches the reader by counting the positive pulses. That is, for the exemplary four-byte UIDs, the reader expects exactly four positive pulses if a single card approaches, but five or more pulses for multiple cards since at least one byte of the UID will be different for other cards.  
         [0039]     Turning to  FIG. 11 , a signal for an anti-collision command from the reader to a selected card is indicated generally by the reference numeral  1100 . This receiver signal could follow the card signals  1000  of  FIG. 10 . The signal indicates how the reader  510  of  FIG. 5  calls the corresponding card by selecting one of the first UID bytes (e.g., 64h or 96h) for the cards  520 ,  530  or  540 . The reader transfers the anti-collision command “02” and the UID byte location “01” and the UID value 64h to the card.  
         [0040]     Turning now to  FIG. 12 , a signal for a response from the selected card to the reader is indicated generally by the reference numeral  1200 . This card signal could follow the receiver signal  1100  of  FIG. 11 . The signal  1200  shows that Card  2  or  530  of  FIG. 5  sends an SOF followed by a first UID byte of 64h in response to the reader&#39;s call signal  1100  of  FIG. 11 . The card  530  responds to the call of the reader and transfers its UID bytes consecutively each in the shape of a positive pulse after receiving the anti-collision command “02”, the UID location “01” and the matching first UID byte value of 64h.  
         [0041]     As shown in  FIG. 13 , a signal for an anti-collision command from the reader to selected cards is indicated generally by the reference numeral  1300 . This receiver signal could follow the card signals  1000  of  FIG. 10 . The signal  1300  includes an SOF, the anti-collision command “02”, the UID byte location “01” indicating the first UID byte, the first UID byte value of 96h, and an EOF. The signal  1300  may occur when the reader  510  of  FIG. 5  fully identifies one card (i.e., Card  2  or  530  of  FIG. 5 ) and then calls another first byte of 96h. Thus, the reader transfers the anti-collision command specifying the first UID byte location and the first UID byte value of 96h to the matching cards.  
         [0042]     Turning to  FIG. 14 , signals for responses from the selected cards to the reader are indicated generally by the reference numeral  1400 . These card signals could follow the receiver signal  1300  of  FIG. 13 . The response signals  1400  include a response signal  1420  from Card  1  or  520  of  FIG. 5 , and a response signal  1440  from Card  3  or  540  of  FIG. 5 . Each of the response signals begins with an SOF and has the same first UID byte value of 96h. The two cards each correspond to the first UID byte of 64h that the reader  510  calls, thus each of these two cards responds to the reader and transfers its respective UID bytes in shape of a positive pulse per byte immediately after receiving the anti-collision command “02”, the UID byte location “01” and the first UID byte value of 64h.  
         [0043]     Turning now to  FIG. 15 , a signal for a second anti-collision command from the reader to the selected card is indicated generally by the reference numeral  1500 . This receiver signal could follow the card signals  1400  of  FIG. 14 . The signal  1500  includes an SOF, the anti-collision command “02”, the UID location “02” indicating the number of UID bytes specified, the first UID byte value of 96h, the second UID byte value of B4h, and an EOF. The reader  510  of  FIG. 5  transfers the anti-collision command, the highest UID byte location, and the first and second UID byte values of 96h and B4h, respectively, to the cards  520  and  540  in order to discern between these two cards having the same first UID byte value of 96h.  
         [0044]     As shown in  FIG. 16 , a signal for a response from the selected card to the reader is indicated generally by the reference numeral  1600 . This card signal could follow the receiver signal  1500  of  FIG. 15 . The card signal  1600  includes a SOF, the first through fourth UID bytes of 96h, B4h, B4h, and A9h, respectively, and an EOF. Thus, Card  1  or  520  of  FIG. 5  responds to the reader because it corresponds to the first and the second UID bytes of 96h and B4h that the reader selects. Card  1  responds to the reader and transfers its particular UID bytes in the shape of a positive pulse per byte after receiving the anti-collision command “02”, the greatest UID byte location “02” and the first and second UID byte values of 96h and B4h, respectively.  
         [0045]     Turning to  FIG. 17 , a signal for a second anti-collision command from the reader to the selected card is indicated generally by the reference numeral  1700 . This receiver signal could follow the card signals  1400  of  FIG. 14 . The signal  1700  includes an SOF, the anti-collision command “02”, the UID location “02” indicating the number of consecutive UID bytes specified, the first UID byte value of 96h, the second UID byte value of 78h, and an EOF. The signal  1700  is used by the reader  510  of  FIG. 5  to identify another card, where the reader calls another second byte, this time 78h. Thus, the reader transfers to the cards the anti-collision command “02” and the highest UID byte location “02” and the first and the second UID byte values of 96h and 78h, respectively.  
         [0046]     Turning now to  FIG. 18 , a signal for a response from the selected card to the reader is indicated generally by the reference numeral  1800 . This card signal could follow the receiver signal  1700  of  FIG. 17 . The card signal  1800  includes a SOF, the first through fourth UID bytes of 96h, 78h, 78h, and 12h, respectively, and an EOF. Thus, the Card  3  or  540  of  FIG. 5  responds to the reader because it is the one corresponding to the first and the second UID bytes of 96h and 78h, respectively, that the reader selects and calls. Card  3  responds to the reader and transfers its UID bytes in shape of a positive pulse for each byte immediately after receiving the anti-collision command “02”, the number of UID byte locations “02”, and the first and second UID byte values of 96h and 78h, respectively. These and other features and advantages of the present disclosure may be readily ascertained by one of ordinary skill in the pertinent art based on the teachings herein. For example, it shall be understood that the teachings of the present disclosure may be extended to UIDs having an arbitrary number of bytes, or to UIDs that are randomly generated on the fly. The features of positive pulse detection and byte-wise comparison are useful for collision prevention.  
         [0047]     It is to be understood that the teachings of the present disclosure may be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof. Most preferably, the teachings of the present disclosure are implemented as a combination of hardware and software. Moreover, the software is preferably implemented as an application program tangibly embodied on a program storage unit. The application program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (“CPU”), a random access memory (“RAM”), and input/output (“I/O”) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the application program, or any combination thereof, which may be executed by a CPU. In addition, various other peripheral units may be connected to the computer platform such as an additional data storage unit and a printing unit.  
         [0048]     It is to be further understood that, because some of the constituent system components and methods depicted in the accompanying drawings are preferably implemented in software, the actual connections between the system components or the process function blocks may differ depending upon the manner in which the present disclosure is programmed. Given the teachings herein, one of ordinary skill in the pertinent art will be able to contemplate these and similar implementations or configurations of the present disclosure.  
         [0049]     Although illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as set forth in the appended claims.