Method of addressing messages and communications system

Abstract

A method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices, the method comprising utilizing a tree search method to attempt to identify individual ones of the multiple wireless identification devices so as to be able to perform communications, without collision, between the interrogator and individual ones of the multiple wireless identification devices, a search tree being defined for the tree search method, the tree having multiple nodes respectively representing subgroups of the multiple wireless identification devices, wherein the interrogator transmits a command at a node, requesting that devices within the subgroup represented by the node respond, wherein the interrogator determines if a collision occurs in response to the command and, if not, repeats the command at the same node. An interrogator configured to transmit a command at a node, requesting that devices within the subgroup represented by the node respond, the interrogator further being configured to determine if a collision occurs in response to the command and, if not, to repeat the command at the same node.

1. A method of establishing wireless communications between an interrogator and wireless identification devices, the method comprising utilizing a tree search technique to establish communications, without collision, between the interrogator and individual ones of the multiple wireless identification devices, the method including using a search tree having multiple nodes respectively representing sub-groups of the multiple wireless identification devices, the method further comprising, for a node, transmitting a command, using the interrogator, requesting that devices within the subgroup represented by the node respond, determining with the interrogator if a collision occurred in response to the command and, if not, repeating the command at the same node. 
     
     
       2. A method in accordance with  claim 1  and further comprising, if a collision occurred in response to the first mentioned command, sending a command at a different node, using the interrogator. 
     
     
       3. A method in accordance with  claim 1  wherein when a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, the device that is not within communications range of the interrogator does not respond to the command. 
     
     
       4. A method in accordance with  claim 1  wherein when a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, the device that is within communications range of the interrogator responds to the command. 
     
     
       5. A method in accordance with  claim 1  wherein a device in a subgroup changes between being within communications range of the interrogator and not being within communications range, over time. 
     
     
       6. A method in accordance with  claim 1  wherein the wireless identification device comprises an integrated circuit including a receiver, a modulator, and a microprocessor in communication with the receiver and modulator. 
     
     
       7. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices, the method comprising:
 establishing for respective devices unique identification numbers;    causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;    transmitting a communication, from the interrogator, requesting devices having random values within a first specified group of random values to respond;    receiving the communication at multiple devices, devices receiving the communication respectively determining if the random value chosen by the device falls within the first specified group and, if so, sending a reply to the interrogator; and    determining using the interrogator if a collision occurred between devices that sent a reply and, if so, creating a second specified group smaller than the first specified group; and, if not, again transmitting a communication requesting devices having random values within the first specified group of random values to respond.    
     
     
       8. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices in accordance with  claim 7  wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply. 
     
     
       9. A method in accordance with  claim 7  wherein one of the first and second specified groups contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, and wherein the device that is not within communications range of the interrogator does not respond to the interrogator. 
     
     
       10. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices in accordance with  claim 7  wherein, after receiving a reply without collision from a device, the interrogator sends a communication individually addressed to that device. 
     
     
       11. A method of addressing messages from a transponder to a selected one or more of a number of communications devices, the method comprising:
 establishing unique identification numbers for respective devices;    causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;    transmitting a communication from the transponder requesting devices having random values within a specified group of a plurality of possible groups of random values to respond, the plurality of possible groups being organized in a binary tree defined by a plurality of nodes at respective levels, the specified group being defined as being at one of the nodes;    receiving the communication at multiple devices, devices receiving the communication respectively determining if the random value chosen by the device falls within the specified group and, if so, sending a reply to the transponder; and, if not, not sending a reply; and    determining using the transponder if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group by descending in the tree; and, if not, transmitting a communication at the same node.    
     
     
       12. A method of addressing messages from a transponder to a selected one or more of a number of communications devices in accordance with  claim 11  wherein establishing unique identification numbers for respective devices comprises establishing a predetermined number of bits to be used for the unique identification numbers. 
     
     
       13. A method of addressing messages from a transponder to a selected one or more of a number of communications devices in accordance with  claim 12  and further including establishing a predetermined number of bits to be used for the random values. 
     
     
       14. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices, the method comprising:
 establishing for respective devices unique identification numbers;    causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;    transmitting a command using the interrogator requesting devices having random values within a specified group of a plurality of possible groups of random values to respond, the specified group being equal to or less than the entire set of random values, the plurality of possible groups being organized in a binary tree defined by a plurality of nodes at respective levels;    receiving the command at multiple RFID devices, RFID devices receiving the command respectively determining if their chosen random values fall within the specified group and, only if so, sending a reply to the interrogator, wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply;    determining using the interrogator if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group using a different level of the tree, the interrogator transmitting a command requesting devices having random values within the new specified group of random values to respond; and, if not, the interrogator re-transmitting a command requesting devices having random values within the first mentioned specified group of random values to respond; and    if a reply without collision is received from a device, the interrogator subsequently sending a command individually addressed to that device.    
     
     
       15. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 14  wherein the first mentioned specified group contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, and wherein the device that is not within communications range of the interrogator does not respond to the transmitting of the command or the re-transmitting of the command. 
     
     
       16. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 14  wherein the first mentioned specified group contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, and wherein the device that is within communications range of the interrogator responds to the transmitting of the command and the re-transmitting of the command. 
     
     
       17. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 14  wherein a device in the first mentioned specified group is capable of changing between being within communications range of the interrogator and not being within communications range of the interrogator over time. 
     
     
       18. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 14  wherein the devices respectively comprise an integrated circuit including a receiver, a modulator, and a microprocessor in communication with the receiver and modulator. 
     
     
       19. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 14  and further comprising, after the interrogator transmits a command requesting devices having random values within the new specified group of random values to respond;
 devices receiving the command respectively determining if their chosen random values fall within the new smaller specified group and, if so, sending a reply to the interrogator.  
 
     
     
       20. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 19  and further comprising, after the interrogator transmits a command requesting devices having random values within the new specified group of random values to respond;
 determining if a collision occurred between devices that sent a reply and, if so, creating a new specified group and repeating the transmitting of the command requesting devices having random values within a specified group of random values to respond using different specified groups until all of the devices capable of communicating with the interrogator are identified.  
 
     
     
       21. A communications system comprising an interrogator, and a plurality of wireless identification devices configured to communicate with the interrogator using RF, the interrogator being configured to employ tree searching to attempt to identify individual ones of the multiple wireless identification devices, so as to be able to perform communications without collision between the interrogator and individual ones of the multiple wireless identification devices, the interrogator being configured to follow a search tree, the tree having multiple nodes respectively representing subgroups of the multiple wireless identification devices, the interrogator being configured to transmit a command at a node, requesting that devices within the subgroup represented by the node respond, the interrogator further being configured to determine if a collision occurs in response to the command and, if not, to repeat the command at the same node. 
     
     
       22. A communications system in accordance with  claim 21  wherein the interrogator is configured to send a command at a different node if a collision occurs in response to the first mentioned command. 
     
     
       23. A communications system in accordance with  claim 21  wherein a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator. 
     
     
       24. A communications system in accordance with  claim 21  wherein a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, and wherein the device that is within communications range of the interrogator responds to the command. 
     
     
       25. A communications system in accordance with  claim 21  wherein a device in a subgroup is movable relative to the interrogator so as to be capable of changing between being within communications range of the interrogator and not being within communications range. 
     
     
       26. A communications system in accordance with  claim 21  wherein the wireless identification device comprises an integrated circuit including a receiver, a modulator, and a microprocessor in communication with the receiver and modulator. 
     
     
       27. A system comprising:
 an interrogator;    a number of communications devices capable of wireless communications with the interrogator;    means for establishing for respective devices unique identification numbers respectively having the first predetermined number of bits;    means for causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;    means for causing the interrogator to transmit a command requesting devices having random values within a specified group of random values to respond;    means for causing devices receiving the command to determine if their chosen random values fall within the specified group and, if so, to send a reply to the interrogator; and    means for causing the interrogator to determine if a collision occurred between devices that sent a reply and, if so, to create a new, smaller, specified group; and, if not, transmit a command requesting devices having random values within the same specified group of random values to respond.    
     
     
       28. A system in accordance with  claim 27  wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply. 
     
     
       29. A system in accordance with  claim 27  wherein a specified group contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator. 
     
     
       30. A system in accordance with  claim 27  wherein the interrogator further includes means for, after receiving a reply without collision from a device, sending a command individually addressed to that device. 
     
     
       31. A system comprising:
 an interrogator configured to communicate to a selected one or more of a number of communications devices; and    a plurality of communications devices; the devices being configured to select random values, wherein respective devices choose random values independently of random values selected by the other devices; the interrogator being configured to transmit a command requesting devices having random values within a specified group of a plurality of possible groups of random values to respond, the specified group being less than the entire set of random values, the plurality of possible groups being organized in a binary tree defined by a plurality of nodes at respective levels, the specified group being defined as being at one of the nodes; devices receiving the command being configured to respectively determine if their chosen random values fall within the specified group and, only if so, send a reply to the interrogator, wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply; the interrogator being configured to determine if a collision occurred between devices that sent a reply and, if so, create a new, smaller, specified group using a different level of the tree, the interrogator being configured to transmit a command requesting devices having random values within the new specified group of random values to respond; and, if not, the interrogator being configured to re-transmit a command requesting devices having random values within the first mentioned specified group of random values to respond.    
     
     
       32. A system in accordance with  claim 31  wherein the first mentioned specified group contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator. 
     
     
       33. A system in accordance with  claim 31  wherein a device in the first mentioned specified group is capable of changing between being within communications range of the interrogator and not being within communications range of the interrogator over time. 
     
     
       34. A system in accordance with  claim 31  wherein the respective devices comprise an integrated circuit including a receiver, a modulator, and a microprocessor in communication with the receiver and modulator. 
     
     
       35. A system comprising:
 an interrogator configured to communicate to a selected one or more of a number of RFID devices;    a plurality of RFID devices, respective devices being configured to store a unique identification number, respective devices being further configured to store a random value;    the interrogator being configured to transmit a command requesting devices having random values within a specified group of a plurality of possible groups of random values to respond, the plurality of possible groups being organized in a binary tree defined by a plurality of nodes at respective levels, the specified group being defined as being at one of the nodes;    devices receiving the command respectively being configured to determine if their chosen random values fall within the specified group and, if so, send a reply to the interrogator; and, if not, not send a reply; and    the interrogator being configured to determine if a collision occurred between devices that sent a reply and, if so, to create a new, smaller, specified group by descending in the tree; and, if not, to transmit a command at the same node.    
     
     
       36. A system in accordance with  claim 35  wherein the unique identification numbers for respective devices are stored in digital form and respectively comprise a predetermined number of bits. 
     
     
       37. A system in accordance with  claim 35  wherein the random values for respective devices are stored in digital form and respectively comprise a predetermined number of bits. 
     
     
       38. A system in accordance with  claim 35  wherein the interrogator is configured to determine if a collision occurred between devices that sent a reply in response to respective Identify commands and, if so, to create further new specified groups and repeat the transmitting of the command requesting devices having random values within a specified group of random values to respond using different specified groups until all responding devices capable of responding are identified. 
     
     
       39. A method implemented in a radio frequency identification ( RFID )  system, the method comprising:      transmitting a radio frequency wireless signal from at least one interrogator to cause a plurality of RFID tags to individually generate random numbers;        transmitting a first wireless request from the at least one interrogator to request RFID tags having generated random numbers in a first subset of random numbers to reply;        if a response to the first request, transmitted from one RFID tag of the plurality of RFID tags, is obtained at the at least one interrogator, repeating the first request; and        if no response to the first request is obtained at the at least one interrogator, transmitting a second request from the at least one interrogator to request RFID tags having generated random numbers in a second subset of random numbers to reply.     
     
     
       40. The method of  claim 39 , wherein if no response to the first request is obtained due to response collision, the second subset is a portion of the first subset. 
     
     
       41. The method of  claim 39 , further comprising:
   the at least one interrogator obtaining the response transmitted from the RFID tag, including an identifier of the RFID.     
     
     
       42. The method of  claim 39 , wherein each of the plurality of RFID tags is affixed to a corresponding object to identify the object. 
     
     
       43. The method of  claim 39 , wherein the first request includes one or more selection bits to identify the first subset. 
     
     
       44. The method of  claim 39 , wherein the plurality of RFID tags are configured to provide responses at time slots determined by random numbers. 
     
     
       45. The method of  claim 39 , wherein the response to the first request includes identifying information of the RFID tag; and the method further comprises:
   transmitting a wireless command from the at least on interrogator to silence the RFID tag using the identifying information of the RFID tag.     
     
     
       46. A radio frequency identification ( RFID )  reader, comprising:      a transmitter to transmit at least a first portion of an identifier to request a first response from an RFID device that has at least a first portion of an identification code equal to the at least first portion of the identifier;        a receiver to receive the first response from the device; and        a processing circuit coupled to the transmitter and receiver to implement an algorithm to detect at least one from among potentially multiple RFID devices, wherein in accordance with the algorithm the processing circuit is to perform collision detection on the first response and, in response to detecting no collision, to retransmit, via the transmitter, the at least first portion of the identifier and to request a second response thereto.     
     
     
       47. The reader of  claim 46 , wherein the processing circuit is configured to determine an identifier of the RFID device using the first response. 
     
     
       48. The reader of  claim 47 , wherein the identifier of the RFID device comprises a random number generated on the RFID device. 
     
     
       49. The reader of  claim 47 , wherein the transmitter is configured to provide an RF field to be modulated by the RFID device to communicate the first response. 
     
     
       50. The reader of  claim 46 , wherein in accordance with the algorithm the processing circuit is to retransmit no more than the first portion of the identifier. 
     
     
       51. The reader of  claim 46 , wherein the transmitter is configured to communicate at a first bit rate during a first period of time, and at a second bit rate during a second period of time. 
     
     
       52. The reader of  claim 46 , wherein the transmitter is configured to transmit a signal to silence the RFID device and to transmit a wake up command to transition the RFID device from a sleep state. 
     
     
       53. The reader of  claim 46 , wherein in accordance with the algorithm the processing circuit is to transmit, via the transmitter, a signal to silence the RFID device in response to the detecting no collision and before retransmitting the first portion. 
     
     
       54. The reader of  claim 46 , wherein the transmitter is configured to transmit an indication of a first number of time slots from which one or more RFID devices are to randomly select a first time slot in which to communicate a random value identifier to the reader. 
     
     
       55. The reader of  claim 54 , wherein the transmitter is further configured to transmit an indication of a second number of time slots, different from the first number of time slots, responsive to collision detection by the processing circuit. 
     
     
       56. A system, comprising:
   an RFID target device to receive at least a first portion of an identifier, to compare the at least first portion of the identifier to at least a first portion of an identification code of the target device, and to communicate a reply value if the at least first portion of the identifier is equal to the at least first portion of the identification code; and        an RFID initiating device to initiate communication with one or more RFID target devices, the initiating device to transmit a first request including a first command and first information, to receive a first response to the first request from each of one or more RFID target devices that has a respective identification code selected by the first information, to perform collision detection on the first response, and to transmit a second request including a retransmission of at least the first command and the first information responsive to detecting no collision.     
     
     
       57. The system of  claim 56 , wherein the target and initiating devices are to implement a time slot method in accordance with a protocol with which the target and initiating devices are compliant. 
     
     
       58. The system of  claim 57 , wherein the target device is to modulate an RF field provided by a remote device to communicate the reply value. 
     
     
       59. The system of  claim 58 , wherein the system is to operate in a selectable one of a first communication mode and a second communication mode in accordance with the protocol, wherein in accordance with the first communication mode the target device is to communicate by modulating a remotely generated RF field and in accordance with the second communication mode the target device is to generate an RF field. 
     
     
       60. The system of  claim 59 , wherein the target and initiating devices are to communicate at a selectable one of a plurality of bit rates in accordance with the protocol. 
     
     
       61. The system of  claim 60 , wherein the target device is to transition from a sleep state upon receiving a wake up command. 
     
     
       62. The system of  claim 56 , wherein the reply value comprises a random number generated by the RFID target device. 
     
     
       63. The system of  claim 56 , wherein the target device is to modulate an RF field provided by a remote device to communicate the reply value. 
     
     
       64. The system of  claim 56 , wherein the initiating device is to transmit a signal to silence the one or more target devices. 
     
     
       65. The system of  claim 64 , wherein the initiating device is to transmit the signal in response to the detecting no collision before transmitting the second request. 
     
     
       66. The system of  claim 56 , wherein the target device is to implement a slotted aloha algorithm in which the target device is to communicate a first identifier in a randomly selected time slot of a number of time slots indicated to the target device. 
     
     
       67. The system of  claim 66 , wherein the first identifier is randomly generated by the target device. 
     
     
       68. The system of  claim 67 , wherein the target device is to modulate a remotely generated RF field to communicate the reply. 
     
     
       69. The system of  claim 56 , wherein the one or more target devices comprises the target device. 
     
     
       70. A radio frequency identification ( RFID )  device, comprising:      a memory to store a first identifier;        a receiver coupled to an antenna to receive a transmission of a first set of bits from a reader in accordance with an algorithm to enable the reader to determine the first identifier;        processing circuitry to compare the first set of bits to a first set of bits of an identification code of RFID device; and        a modulating circuit to modulate an RF field produced by the reader to communicate a second set of bits to the reader if the first set of bits is equal to the first set of bits of the identification code, wherein the first identifier comprises the second set of bits, and wherein in accordance with the algorithm the receiver is to further receive a retransmission of at least the first set of bits from the reader if the reader receives the second set of bits without collision.     
     
     
       71. The device of  claim 70 , wherein the second set of bits comprises the first set of bits. 
     
     
       72. The device of  claim 70 , further comprising:
   a random number generator to generate the first identifier and a random value, wherein the random value is to be used to select a slot in which to communicate the second set of bits in accordance with a time slot method.     
     
     
       73. The device of  claim 70 , wherein the modulating circuit is to operate in an alternate communication mode in which the modulating circuit is to modulate an RF field produced by the device itself. 
     
     
       74. The device of  claim 70 , wherein the modulating circuit is to communicate at one of a plurality of selectable bit rates. 
     
     
       75. The device of  claim 74 , wherein the receiver is receive a wake up command from the reader to transition the device from a sleep state. 
     
     
       76. The device of  claim 70 , wherein the processing circuitry is to implement a slotted aloha algorithm. 
     
     
       77. The device of  claim 76 , further comprising memory storing the identification code, separate from the first identifier. 
     
     
       78. The device of  claim 70 , further comprising memory storing the identification code, separate from the first identifier. 
     
     
       79. The device of  claim 70 , wherein in accordance with the algorithm the receiver is to receive a signal from the reader addressed to the device responsive to the reader receiving the second set of bits without collision. 
     
     
       80. The device of  claim 79 , wherein the signal is to silence the device. 
     
     
       81. The device of  claim 80 , wherein in accordance with the algorithm the signal is to be received by the receiver before the retransmission of the at least first set of bits. 
     
     
       82. The device of  claim 70 , wherein the receiver is to receive an indication of a first number of time slots from which the device is to randomly select a first time slot in which to communicate the first identifier and to receive an indication of a second number of time slots, different from the first number of time slots. 
     
     
       83. A radio frequency identification ( RFID )  method, comprising:      transmitting a first wireless radio frequency  ( RF )  signal from an RFID reader, the first RF signal specifying a first set of bits to request a set of RFID devices having the first set of bits to identify themselves, wherein each of the RFID devices generates a random value to select a time slot to identify themselves;        receiving at the RFID reader a response to the first RF signal from at least a first RFID device in a first time slot, wherein the first RFID device selects the first time slot to transmit the response in accordance with a first random value generated by the first RFID device and the response including an identifier of the first RFID device;        determining the identifier of the first RFID device from the response received in the RFID reader;        transmitting a second wireless RF signal from the RFID reader, the second RF signal to prevent the first RFID device from responding when the first RF signal is repeated; and        retransmitting the first RF signal from the RFID reader.     
     
     
       84. The method of  claim 83 , wherein the second wireless RF signal silences the first RFID device. 
     
     
       85. The method of  claim 83 , wherein the identifier of the first RFID device comprises a number generated by the first RFID device. 
     
     
       86. The method of  claim 85 , wherein the number is a random number. 
     
     
       87. The method of  claim 83 , wherein the identifier of the first RFID device is a predetermined identification code. 
     
     
       88. The method of  claim 83 , wherein the identifier comprises the first set of bits. 
     
     
       89. The method of  claim 83 , further comprising:
   identifying by the RFID reader a number of time slots for the set of RFID devices to respond to the first RF signal.     
     
     
       90. The method of  claim 89 , wherein the identifying comprises:
   transmitting at least one third wireless RF signal from the RFID reader to indicate timing of a plurality of time slots for the set of RFID devices to identify themselves.     
     
     
       91. A radio frequency identification ( RFID )  method, comprising:      transmitting a first wireless command from an RFID reader, the first command including a first set of bits to address a set of RFID devices identified by the first set of bits, the first command to request the RFID devices to respond with identifiers of the RFID devices;        determining an identifier of at least a first RFID device from at least one reply to the first command;        after the determining of the identifier, transmitting a second wireless command from the RFID reader, the second wireless command to silence the first RFID device for a third wireless command; and        transmitting the third wireless command from the RFID reader, the third command including the first set of bits to address a set of RFID devices identified by the first set of bits.     
     
     
       92. The method of  claim 91 , wherein the third wireless command is identical to the first wireless command. 
     
     
       93. The method of  claim 92 , wherein the identifier of the first RFID device comprises a number generated by the first RFID device. 
     
     
       94. The method of  claim 93 , wherein the number is a random number. 
     
     
       95. The method of  claim 92 , wherein the identifier of the first RFID device is an unique identification code. 
     
     
       96. The method of  claim 92 , wherein the identifier comprises the first set of bits. 
     
     
       97. The method of  claim 91 , further comprising:
   identifying by the RFID reader a number of time slots for the set of RFID devices to respond to the first RF signal.     
     
     
       98. The method of  claim 97 , wherein the identifying comprises:
   transmitting at least one third wireless RF signal from the RFID reader to indicate timing of a plurality of time slots for the set of RFID devices to identify themselves.     
     
     
       99. The method of  claim 97 , further comprising:
   identifying by the RFID reader a different number of time slots to respond to the fourth RF signal.     
     
     
       100. A radio frequency identification method, comprising:
   transmitting at least a first portion of an identifier to request a first response from a radio frequency device that has at least a first portion of an identification code equal to the at least first portion of the identifier;        receiving the first response from the radio frequency device;        executing an algorithm to identify at least one from among potentially multiple radio frequency devices, wherein in accordance with the algorithm a processing circuit is to perform collision detection on the first response and, if no collision is detected, retransmitting the at least first portion of the identifier to request a second response;        receiving the second response;        determining an identifier of the radio frequency device using at least the first response;        associating an owner with the identifier of the radio frequency device; and        debiting an account held by the owner.     
     
     
       101. The method of  claim 100 , wherein the debiting of the account held by the owner is associated with the payment of a toll. 
     
     
       102. The method of  claim 101 , wherein at least the acts of transmitting at least a first portion and executing an algorithm are performed by apparatus disposed within a toll both, and said method further comprises operating said apparatus disposed within said toll both at least when said radio frequency device issuing said first response is in proximity thereto. 
     
     
       103. The method of  claim 101 , wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       104. The method of  claim 101 , wherein at least the act of transmitting at least a first portion is performed by apparatus disposed within a toll both, and said receiving a first response occurs substantially when said radio frequency device issuing said first response is in proximity to said apparatus disposed within said toll booth. 
     
     
       105. The method of  claim 100 , wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       106. The method of  claim 100 , wherein the debiting of the account held by the owner is for payment for goods or services. 
     
     
       107. The method of  claim 100 , wherein the identifier of the radio frequency device comprises a random number generated on the radio frequency device. 
     
     
       108. The method of  claim 100 , further comprising:
   transmitting an indication of a first number of time slots from which one or more radio frequency devices are to randomly select a first time slot in which to communicate a random value identifier.     
     
     
       109. The method of  claim 108 , further comprising:
   transmitting an indication of a second number of time slots, different from the first number of time slots, responsive to collision detection.     
     
     
       110. A method implemented in a radio frequency identification apparatus, the method comprising:
   transmitting a first wireless request from at least one interrogating apparatus to request one or more radio frequency devices having random numbers in a first subset of random numbers to reply;        if a response to the first request, transmitted from one radio frequency device of the plurality of radio frequency devices, is obtained at the at least one interrogating apparatus, repeating the first request; and        if no response to the first request is obtained at the at least one interrogating apparatus, transmitting a second request from the at least one interrogating apparatus to request radio frequency devices having generated random numbers in a second subset of random numbers to reply;        receiving an identifier of one radio frequency device of the plurality of radio frequency devices;        associating the identifier of the one radio frequency device of the plurality of radio frequency devices with an account; and        debiting the account.     
     
     
       111. The method of  claim 110 , wherein the debiting of the account is associated with the payment of a toll for passage through a tollbooth by the one radio frequency device. 
     
     
       112. The method of  claim 110 , wherein the debiting of the account is for the payment of goods or services. 
     
     
       113. The method of  claim 112 , wherein the debiting of the account occurs pursuant to receipt of a credit card number. 
     
     
       114. The method of  claim 110 , wherein if no response to the first request is obtained due to response collision, the second subset is a portion of the first subset. 
     
     
       115. The method of  claim 110 , wherein the first request includes one or more selection bits to identify the first subset. 
     
     
       116. The method of  claim 110 , wherein the plurality of radio frequency devices are configured to provide responses at time slots determined by random numbers. 
     
     
       117. A radio frequency identification method, comprising:
   transmitting at least a first portion of an identifier to request a first response from a radio frequency device that has at least a first portion of an identification code equal to the at least first portion of the identifier;        receiving the first response from the radio frequency device;        executing an algorithm to detect at least one from among potentially multiple radio frequency devices, wherein in accordance with the algorithm a processing circuit is to perform collision detection on the first response and, after detecting no collision, retransmitting the at least first portion of the identifier to request a second response;        receiving the second response and determining an identifier of the radio frequency device using the first response;        associating the identifier of the radio frequency device with a financial account; and        debiting the account for the value of at least one of  ( i )  a good;  ( ii )  a service; and/or  ( iii )  a roadway toll, provided to a possessor of the radio frequency device.     
     
     
       118. The method of  claim 117 , wherein the debiting of the account is associated with the payment of a toll, and the method is performed substantially by apparatus disposed within a toll booth through which the radio frequency device passes. 
     
     
       119. The method of  claim 117 , wherein the debiting of the account held by the owner is for the remote payment of goods or services. 
     
     
       120. The method of  claim 117 , wherein the identifier of the radio frequency device comprises a random number generated on the radio frequency device. 
     
     
       121. The method of  claim 117 , further comprising:
   transmitting an indication of a first number of time slots from which one or more radio frequency devices are to randomly select a first time slot in which to communicate a random value identifier.     
     
     
       122. The method of  claim 121 , further comprising:
   transmitting an indication of a second number of time slots, different from the first number of time slots, responsive to collision detection.     
     
     
       123. A method of conducting a transaction using radio frequency identification apparatus, comprising:
   operating interrogation apparatus;        transmitting via the interrogation apparatus at least a first portion of an identifier to request a first response from a radio frequency device that has at least a first portion of an identification code equal to the at least first portion of the identifier;        receiving the first response from the radio frequency device;        executing an algorithm to identify at least one from among potentially multiple radio frequency devices, wherein in accordance with the algorithm a processing circuit is to perform collision detection on the first response and, if no collision is detected, retransmitting the at least first portion of the identifier from the interrogation apparatus to request a second response;        receiving the second response;        determining an identifier of the radio frequency device using at least the first response; and        debiting an account associated with the identifier.     
     
     
       124. The method of  claim 123 , wherein the debiting of the account associated with the identifier is pursuant to payment of a toll associated with a tollbooth through which the radio frequency device passes. 
     
     
       125. The method of  claim 123 , wherein at least the acts of transmitting at least a first portion and executing an algorithm are performed by apparatus disposed within a toll both, and said method further comprises operating said apparatus disposed within said toll both at least when said radio frequency device issuing said first response is in proximity thereto. 
     
     
       126. The method of  claim 124 , wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       127. The method of  claim 123 , wherein at least the act of transmitting at least a first portion is performed by apparatus disposed within a toll both, and said receiving a first response occurs substantially when said radio frequency device issuing said first response is in proximity to said apparatus disposed within said toll booth. 
     
     
       128. The method of  claim 123 , wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       129. The method of  claim 123 , wherein the debiting of the account is for payment for goods or services.