Method of addressing messages and communications systems

Abstract

A method of and apparatus for establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices., the method comprising utilizing a tree search method to establish 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 levels respectively representing subgroups of the multiple wireless identification devices, the method further comprising starting the tree search at a selectable level of the search tree. A communications system comprising an interrogator, and a plurality of wireless identification devices configured to communicate with the interrogator in a wireless fashion, the respective wireless identification devices having a unique identification number, the interrogator being configured to employ a tree search technique to determine the unique identification numbers of the different wireless identification devices so as to be able to establish communications between the interrogator and individual ones of the multiple wireless identification devices without collision by multiple wireless identification devices attempting to respond to the interrogator at the same time, wherein the interrogator is configured to start the tree search at a selectable level of the search tree The interrogator transmits an initial wireless command to start identification of the wireless identification devices. The initial wireless command specifies at least two bits and requesting first devices having the at least two bits to reply. If there is no collision in response to the initial wireless command, the interrogator identifies, from a response to the initial command, a random number generated at one of the devices.

1. A method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices, the wireless identification devices having respective identification numbers and being addressable by specifying identification numbers with any one of multiple possible degrees of precision, the method comprising utilizing a tree search in an arbitration scheme to determine a degree of precision necessary to establish one-on-one communications 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 selectable levels respectively representing subgroups of the multiple wireless identification devices, the level at which a tree search starts being variable the method further comprising starting the tree search at any selectable level of the search tree. 
     
     
       2. A method in accordance with  claim 1  and further comprising determining the maximum possible number of wireless identification devices that could communicate with the interrogator, and selecting a level of the search tree based on the determined maximum possible number of wireless identification devices that could communicate with the interrogator. 
     
     
       3. A method in accordance with  claim 2  and further comprising starting the tree search at a level determined by taking the base two logarithm of the determined maximum possible number, wherein the level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively. 
     
     
       4. A method in accordance with  claim 2  and further comprising starting the tree search at a level determined by taking the base two logarithm of the determined maximum possible number, wherein the level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively, and wherein the maximum number of devices in a subgroup in one level is half of the maximum number of devices in the next higher level. 
     
     
       5. A method in accordance with  claim 2  and further comprising starting the tree search at a level determined by taking the base two logarithm of the power of two nearest the determined maximum possible number, wherein the level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively, and wherein the maximum number of devices in a subgroup in one level is half of the maximum number of devices in the next higher level. 
     
     
       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 respectively having a first predetermined number of bits;   establishing a second predetermined number of bits to be used for random values;   causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;   determining the maximum number of devices potentially capable of responding to the interrogator;   transmitting a command from the interrogator requesting devices having random values within a specified group of random values to respond, by using a subset of the second predetermined number of bits, the specified group being chosen in response to the determined maximum number;   receiving the command at multiple devices, devices receiving the command respectively determining if the random value chosen by the device falls within the 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 new, smaller, specified group.   
     
     
       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 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 random value of the device sending the reply. 
     
     
       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 sending a reply to the interrogator comprises transmitting both the random value of the device sending the reply and the unique identification number of the device sending the reply. 
     
     
       11. 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 command individually addressed to that device. 
     
     
       12. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices, the method comprising:
 causing the devices to select random values for use as arbitration numbers, wherein respective devices choose random values independently of random values selected by the other devices, the devices being addressable by specifying arbitration numbers with any one of multiple possible degrees of precision;   transmitting a command from 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 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, wherein the size of groups of random values decrease in size by half with each node descended, wherein the specified group is below a node on the tree selected based on the maximum number of devices capable of communicating with the interrogator;   receiving the command at multiple devices, devices receiving the command respectively determining if the random value chosen by the device falls within the specified group and, if so, sending a reply to the interrogator; and, if not, not sending a reply; and   determining using the interrogator if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group by descending in the tree.   
     
     
       13. A method of addressing messages from an interrogator 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 communications devices in accordance with  claim 13  wherein the predetermined number of bits to be used for the random values comprises an integer multiple of eight. 
     
     
       15. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices in accordance with  claim 13  wherein devices sending a reply to the interrogator do so within a randomly selected time slot of a number of slots. 
     
     
       16. 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 a predetermined number of bits to be used for random values, the predetermined number being a multiple of sixteen;   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 from 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, wherein the maximum size of groups of random values decrease in size by half with each node descended, wherein the specified group is below a node on a level of the tree selected based on the maximum number of devices known to be capable of communicating with the interrogator;   receiving the command at multiple devices, devices receiving the command respectively determining if the random value chosen by the device falls within the specified group and, only if so, sending a reply to the interrogator, wherein sending a reply to the interrogator comprises transmitting both the random value of the device sending the reply and the unique identification number of the device sending the reply;   using the interrogator to determine if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group using a level of the tree different from the level used in the interrogator transmitting, the interrogator transmitting a command requesting devices having random values within the new 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.   
     
     
       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 16  and further comprising determining the maximum possible number of wireless identification devices that could communicate with the interrogator. 
     
     
       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 16  wherein selecting the level of the tree comprises taking the base two logarithm of the determined maximum possible number, wherein a level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively. 
     
     
       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 16  wherein selecting the level of the tree comprises taking the base two logarithm of the determined maximum possible number, wherein a level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively, and wherein the maximum number of devices in a subgroup in one level is half of the maximum number of devices in the next higher level. 
     
     
       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 16  wherein selecting the level of the tree comprises taking the base two logarithm of the power of two nearest the determined maximum possible number, wherein the level of the tree containing all subgroups is considered level zero, and lower levels are numbered consecutively, and wherein the maximum number of devices in a subgroup in one level is half of the maximum number of devices in the next higher level. 
     
     
       21. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 16  wherein the wireless identification device comprises an integrated circuit including a receiver, a modulator, and a microprocessor in communication with the receiver and modulator. 
     
     
       22. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 16  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, using devices receiving the command, if their chosen random values fall within the new smaller specified group and, if so, sending a reply to the interrogator. 
     
     
       23. A method of addressing messages from an interrogator to a selected one or more of a number of RFID devices in accordance with  claim 22  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 within communications range are identified. 
     
     
       24. A communications system comprising an interrogator, and a plurality of wireless identification devices configured to communicate with the interrogator in a wireless fashion, the wireless identification devices having respective identification numbers, the interrogator being configured to employ a tree search in a search tree having multiple selectable levels, to determine the identification numbers of the different wireless identification devices with sufficient precision so as to be able to establish one-on-one communications between the interrogator and individual ones of the multiple wireless identification devices, wherein the interrogator is configured to start the tree search at any selectable level of the search tree. 
     
     
       25. A communications system in accordance with  claim 24  wherein the tree search is a binary tree search. 
     
     
       26. A communications system in accordance with  claim 24  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 a predetermined number of bits to be used as random numbers, and for causing respective devices to select random numbers respectively having the predetermined number of bits;   means for inputting a predetermined number indicative of the maximum number of devices possibly capable of communicating with the receiver;   means for causing the interrogator to transmit a command requesting devices having random values within a specified group of random values to respond, the specified group being chosen in response to the inputted predetermined number;   means for causing devices receiving the command to determine if their chosen random values fall within the specified group and, if so, 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, create a new, smaller, specified group.   
     
     
       28. A system in accordance with  claim 27  wherein sending a reply to the interrogator comprises transmitting the random value of the device sending the reply. 
     
     
       29. 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. 
     
     
       30. A system comprising:
 an interrogator configured to communicate to a selected one or more of a number of communications devices;   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, different sized groups of devices being addressable by specifying random values with differing levels of precision;   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, wherein the size of groups of random values decrease in size by half with each node descended, wherein the specified group is below a node on the tree selected based on a predetermined maximum number of devices capable of communicating with the interrogator;   devices receiving the command being configured to respectively 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, create a new, smaller, specified group by descending in the tree.   
     
     
       31. A system in accordance with  claim 30  wherein the random values respectively have a predetermined number of bits. 
     
     
       32. A system in accordance with  claim 30  wherein respective devices are configured to store unique identification numbers of a predetermined number of bits. 
     
     
       33. A system in accordance with  claim 30  wherein respective devices are configured to store unique identification numbers of sixteen bits. 
     
     
       34. 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 unique identification numbers respectively having a first predetermined number of bits, respective devices being further configured to store a second predetermined number of bits to be used for random values, respective devices being configured to select random values independently of random values selected by the other devices;   the interrogator being configured to transmit an identify command requesting a response from devices having random values within a specified group of a plurality of possible groups or random values, the specified group being less than or equal to 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, wherein the maximum size of groups of random values decrease in size by half with each node descended, wherein the specified group is below a node on a level of the tree selected based on the maximum number of devices known to be capable of communicating with the interrogator;   devices receiving the command respectively being configured to 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 both the random value of the device sending the reply and 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 level of the tree different from the level used in previously transmitting an identify command, the interrogator transmitting an identify command requesting devices having random values within the new specified group of random values to respond; and   the interrogator being configured to send a command individually addressed to a device after communicating with a device without a collision.   
     
     
       35. A system in accordance with  claim 34  wherein the interrogator is configured to input and store the predetermined number. 
     
     
       36. A system in accordance with  claim 34  wherein the devices are configured to respectively determine if their chosen random values fall within a specified group and, if so, send a reply, upon receiving respective identify commands. 
     
     
       37. A system in accordance with  claim 36  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, create further new specified groups and repeat the transmitting of the identify command requesting devices having random values within a specified group of random values to respond using different specified groups until all responding devices are identified. 
     
     
       38. A method, comprising:
 transmitting, from a master wireless device having a communication field, an initial wireless command requesting responses to start identification of a plurality of radio frequency communications devices configured to transmit at least identification information, the initial command to be sent after the radio frequency communications devices are disposed in the communication field and before any of the radio frequency communications devices communicate any responses to the master wireless device, the initial wireless command specifying at least two bits to identify first radio frequency communications devices and requesting the first radio frequency communications devices to reply with identification numbers to be used by the master wireless device in subsequent communications to individually address the first radio frequency communications devices;   determining whether there is a collision in response to the initial wireless command;   identifying, from a response to the initial command, an identification number of a radio frequency communications device, if there is no collision in response to the initial wireless command; and   individually addressing the radio frequency communications device, by the master wireless device, using the identification number identified from the response to the initial command, to request a reply from the radio frequency communications device.   
     
     
       39. The method of claim 38, further comprising:
 transmitting, from the master wireless device, a subsequent wireless command requesting responses to continue the identification of the plurality of radio frequency communications devices, the subsequent wireless command to identify a subset of the first radio frequency communications devices and request the subset to reply with identification numbers.   
     
     
       40. The method of claim 38, wherein the response comprises further information about the radio frequency communications device. 
     
     
       41. The method of claim 38, wherein the identification number comprises a unique identification code that uniquely identifies the radio frequency communications device among the first radio frequency communications devices. 
     
     
       42. The method of claim 38, wherein the identification number comprises a random number generated by the radio frequency communications device. 
     
     
       43. The method of claim 38, wherein the radio frequency communications device is to select a random value that determines a time slot in which the radio frequency communications device provides the master wireless device with a response containing the identification number. 
     
     
       44. The method of claim 43, wherein the response containing the identification number is in response to the initial wireless command. 
     
     
       45. A radio frequency master device, comprising:
 one or more antennas;   a controller;   a transmitter coupled to the controller and the one or more antennas to send a first wireless radio frequency (RF) signal to start identification of individual devices of a population of radio frequency communications devices configured to provide at least identification information, the first RF signal having first bits to identify first radio frequency communications devices and requesting the first radio frequency communications devices to reply with identification numbers to be used by the master device in subsequent communications to individually address the first radio frequency communications devices; and   a receiver coupled to the controller and the one or more antennas to detect a collision in response to the first RF signal and, when there is no collision in response to the first RF signal, to determine an identification number of a first radio frequency communications device from a reply to the first RF signal;   wherein the transmitter is to subsequently use the identification number, identified from the reply to the first wireless RF signal, to request replies from the first radio frequency communications device.   
     
     
       46. The master device of claim 45, wherein the transmitter is to further send a second wireless RF signal to continue the identification of individual devices of the population of radio frequency communications devices, the second RF signal requesting a subset of the first radio frequency communications devices to reply with identification numbers. 
     
     
       47. The master device of claim 45, wherein the identification number comprises a unique identification code that uniquely identifies the first radio frequency communications device among the population of radio frequency communications devices. 
     
     
       48. The master device of claim 45, wherein the radio frequency communications device is to select a random value that determines a time slot to provide the master device with a response containing the identification number. 
     
     
       49. The master device of claim 48, wherein the response containing the identification number is in response to the first wireless RF signal. 
     
     
       50. A radio frequency communications system, comprising:
 a plurality of radio frequency communications devices configured to provide at least identification information; and   a wireless controlling device having a range for wireless communications, the plurality of radio frequency communications devices disposed within the range for wireless communications, the controlling device comprising   at least one antenna,   a transmitter coupled to the at least one antenna to transmit a first wireless radio frequency (RF) signal to initiate a search to identify the radio frequency communications devices, the first RF signal specifying at least two bits to identify first radio frequency communications devices and request replies from the first radio frequency communications devices, wherein the first radio frequency communications devices reply to the first RF signal with identification numbers to be used by the controlling device in subsequent communications to individually address the first radio frequency communications devices, and   a receiver coupled to the at least one antenna to identify, from at least one reply to the first RF signal, an identification number of a first radio frequency communications device, if there is no response collision in replying to the first RF signal;   wherein the transmitter is to subsequently use the identification number, identified from the reply to the first wireless RF signal, to request replies from the first radio frequency communications device.   
     
     
       51. The radio frequency communications system of claim 50, wherein each of the first radio frequency communications devices identified by the at least two bits is to generate a random value which determines a time slot to provide identification numbers to the controlling device. 
     
     
       52. The radio frequency communications system of claim 51, wherein the transmitter is to further transmit a plurality of second signals to indicate a plurality of time slots. 
     
     
       53. The radio frequency communications system of claim 51, wherein each of the first radio frequency communications devices is to provide an identification number in the time slot in response to the first RF signal. 
     
     
       54. The radio frequency communications system of claim 50, wherein the identification number comprises a unique identification code that uniquely identifies the first radio frequency communications device. 
     
     
       55. The radio frequency communications system of claim 50, wherein the identification number comprises a random number generated by the first radio frequency communications device. 
     
     
       56. The radio frequency communications system of claim 50, wherein the transmitter is to transmit a second wireless RF signal to continue the search, the second wireless RF signal to identify a subset of the first radio frequency communications devices and to request the subset to reply with identification numbers. 
     
     
       57. A radio frequency identification communications system, comprising:
 A wireless controlling device to transmit an initial wireless radio frequency (RF) signal to start a search to identify radio frequency communications devices configured to transmit at least identification information, the initial wireless RF signal specifying at least two first bits to identify first radio frequency communications devices and requesting the first radio frequency communications devices to reply with identification numbers; and   a set of radio frequency communications devices, each device of the set having an antenna, and
 a circuit coupled to the antenna, if identified by the at least two first bits the circuit to receive the initial RF signal, to generate a random value that determines a time slot, and to provide an identification number to the controlling device in accordance with the time slot; 
   wherein the controlling device is to subsequently use an identification number of a first radio frequency communications device, identified from a reply to the first wireless RF signal, to request replies from the first radio frequency communications device.   
     
     
       58. The radio frequency communications system of claim 57, wherein the controlling device is to transmit a subsequent wireless RF signal requesting responses to continue the search. 
     
     
       59. The radio frequency communications system of claim 58, wherein the subsequent wireless RF signal is to identify a subset of the first radio frequency communications devices and request identification numbers from the subset. 
     
     
       60. The radio frequency communications system of claim 59, wherein the identification number of the first radio frequency communications device comprises a random number generated on the first radio frequency communications device that provides the reply to the controlling device. 
     
     
       61. The radio frequency communications system of claim 59, wherein the identification number comprises a unique identification code to uniquely identify, among the set of radio frequency communications devices, the first radio frequency communications device. 
     
     
       62. The radio frequency communications system of claim 57, wherein if identified by the at least two first bits, each device of the set is to provide an identification number to the controlling device in accordance with the time slot in a response to the initial wireless RF signal. 
     
     
       63. A radio frequency communications method, comprising:
 transmitting, from a wireless master device, a first wireless command to initiate identification of a population of radio frequency communications devices and a plurality of subsequent wireless commands to continue the identification of the population of radio frequency communications devices, the first command including first bits that identify first radio frequency communications devices, the first command requesting the first radio frequency communications devices to reply with identifiers of the first radio frequency communications devices;   generating, by the first radio frequency communications devices, random values; replying to the wireless master device, by the first radio frequency communications devices that have received the first wireless command, to provide identifiers in time slots determined at least in part according to the random values;   receiving, at the wireless master device, a reply to the first wireless command from a first radio frequency communications device;   determining whether there is a collision in replying to the first wireless command; if there is no collision in responses to the first wireless command, identifying from the reply an identifier of the first radio frequency communications device; and   transmitting a second wireless command to individually identify the first radio frequency communications device using the identifier of the first radio frequency communications device and to request the first radio frequency communications device to reply.   
     
     
       64. The method of claim 63, wherein the plurality of subsequent wireless commands comprise a third wireless command from the wireless master device to continue identification of the population of radio frequency communications devices, the third command identifying a subset of the first radio frequency communications devices and requesting the subset to reply with identifiers. 
     
     
       65. The method of claim 64, wherein the third command includes one more bit than the first bits to identify the subset. 
     
     
       66. The method of claim 63, wherein the identifier of the first radio frequency communications device is a random number generated by the first radio frequency communications device. 
     
     
       67. The method of claim 63, wherein the first bits are a common portion of identifiers of the first radio frequency communications devices. 
     
     
       68. The method of claim 63, wherein the identifier of the first radio frequency communications device is a unique identification code that tells the first radio frequency communications device apart from the population of radio frequency communications devices. 
     
     
       69. The method of claim 63, wherein the first radio frequency communications devices are to provide the identifiers in the time slots in response to the first wireless command. 
     
     
       70. A radio frequency communications method, comprising:
 transmitting, from a master wireless device having a communication field, an initial wireless command requesting responses to start identification of a plurality of radio frequency communications devices configured to transmit at least identification information, the initial command to be sent after the radio frequency communications devices are disposed in the communication field and before any of the radio frequency communications devices communicate any responses to the master wireless device, the initial wireless command specifying at least two bits to identify first radio frequency communications devices and requesting the first radio frequency communications devices to reply with identification numbers to be used by the master wireless device in subsequent communications to individually address the first radio frequency communications devices;   determining whether there is a collision in response to the initial wireless command;   identifying, from a response to the initial command, an identification number of a radio frequency communications device, if there is no collision in response to the initial wireless command;   individually addressing the radio frequency communications device, by the master wireless device, using the identification number identified from the response to the initial command, to request a reply from the radio frequency communications device;   determining an owner of the radio frequency communications device based at least in part on said identification number of said radio frequency communications device; and   debiting an account held by said owner.   
     
     
       71. The method of claim 70, wherein the debiting of the account held by the owner is associated with the payment of a toll. 
     
     
       72. The method of claim 71, wherein said master wireless device is disposed within a toll booth, and said method further comprises operating said master wireless device disposed within said toll booth at least when said radio frequency communications device issuing said response to said initial wireless command is in proximity thereto. 
     
     
       73. The method of claim 71, wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       74. The method of claim 71, wherein the radio frequency communications device is to select a random value that determines a time slot in which the radio frequency communications device provides the master wireless device with the response used to identify the identification number. 
     
     
       75. The method of claim 70, wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       76. The method of claim 70, wherein the debiting of the account held by the owner is for payment for goods or services. 
     
     
       77. The method of claim 76, further comprising:
 transmitting, from the master wireless device, a subsequent wireless command requesting responses to continue the identification of the plurality of radio frequency communications devices, the subsequent wireless command to identify a subset of the first radio frequency communications devices and request the subset to reply with identification numbers.   
     
     
       78. The method of claim 76, wherein the response comprises further information about the radio frequency communications device. 
     
     
       79. The method of claim 76, wherein the identification number comprises a unique identification code that uniquely identifies the radio frequency communications device among the plurality of radio frequency communications devices. 
     
     
       80. The method of claim 76, wherein the identification number comprises a random number generated by the radio frequency communications device. 
     
     
       81. The method of claim 76, wherein the radio frequency communications device is to select a random value that determines a time slot in which the radio frequency communications device provides the master wireless device with the response used to identify the identification number. 
     
     
       82. The method of claim 70, wherein the radio frequency communications device is to select a random value that determines a time slot in which the radio frequency communications device provides the master wireless device with the response used to identify the identification number. 
     
     
       83. A radio frequency communications method, comprising:
 transmitting, from a wireless master device, a first wireless command to initiate identification of a population of radio frequency communications devices and a plurality of subsequent wireless commands to continue the identification of the population of radio frequency communications devices, the first command including first bits that identify first radio frequency communications devices, the first command requesting the first radio frequency communications devices to reply with identifiers of the first radio frequency communications devices;   generating, by the first radio frequency communications devices, random values;   replying to the wireless master device, by the first radio frequency communications devices that have received the first wireless command, to provide identifiers in time slots determined at least in part according to the random values;   receiving, at the wireless master device, a reply to the first wireless command from a first radio frequency communications device;   determining whether there is a collision in replying to the first wireless command;   if there is no collision in responses to the first wireless command, identifying from the reply an identifier of the first radio frequency communications device; and   transmitting a second wireless command to individually identify the first radio frequency communications device using the identifier of the first radio frequency communications device and to request the first radio frequency communications device to reply; and   determining an account associated with the first radio frequency communications device based at least in part on said received reply of said first radio frequency communications device.   
     
     
       84. The method of claim 83, further comprising debiting the account. 
     
     
       85. The method of claim 84, wherein the debiting of the account is associated with the payment of a toll. 
     
     
       86. The method of claim 85, wherein said master wireless device is disposed within a toll booth, and said method further comprises operating said master wireless device disposed within said toll booth at least when said first radio frequency communications device issuing said reply to the first wireless command is in proximity thereto. 
     
     
       87. The method of claim 85, wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       88. The method of claim 84, wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       89. The method of claim 84, wherein the debiting of the account is for the payment of goods or services. 
     
     
       90. The method of claim 83, further comprising:
 transmitting, from the master wireless device, a subsequent wireless command requesting responses to continue the identification of the population of radio frequency communications devices, the subsequent wireless command to identify a subset of the population of radio frequency communications devices and request the subset to reply with identification numbers.   
     
     
       91. The method of claim 83, wherein the reply to the first wireless command comprises further information about the first radio frequency communications device. 
     
     
       92. The method of claim 83, wherein the identifier comprises a unique identification code that uniquely identifies the first radio frequency communications device from the population of radio frequency communications devices. 
     
     
       93. The method of claim 83, wherein the identifier comprises a random number generated by the first radio frequency communications device. 
     
     
       94. The method of claim 83, wherein the first radio frequency communications device is to select a random value that determines a time slot in which the first radio frequency communications device provides the master wireless device with the reply containing the identifier. 
     
     
       95. The method of claim 83, wherein the reply used to identify the identifier is in response to the first wireless command. 
     
     
       96. A radio frequency communications-based method of conducting a financial transaction, comprising:
 transmitting, from a master wireless device having a communication field, an initial wireless command requesting responses to start identification of at least one of a plurality of radio frequency communications devices configured to transmit at least identification information, the initial command to be sent after the at least one radio frequency communications devices are disposed in the communication field and before any of the at least one radio frequency communications devices communicate any response or responses to the master wireless device, the initial wireless command specifying at least two bits to identify one or more first radio frequency communications devices and requesting the one or more first radio frequency communications devices to reply with respective identification numbers to be used by the master wireless device in subsequent communications to individually address the one or more first radio frequency communications devices;   determining whether there is a collision in response to the initial wireless command;   identifying, from a received response to the initial command, an identification number of a particular radio frequency communications device, if there is no collision in response to the initial wireless command;   individually addressing the particular radio frequency communications device, by the master wireless device, using the identification number identified from the response to the initial command, to request a reply from the particular radio frequency communications device;   identifying a financial account associated with an owner of the particular radio frequency communications device based at least in part on said identification number of said particular radio frequency communications device; and   debiting said account as part of said financial transaction.   
     
     
       97. The method of claim 96, wherein the financial transaction is associated with the payment of a toll. 
     
     
       98. The method of claim 97, wherein said master wireless device is disposed within a toll booth, and said method further comprises operating said master wireless device disposed within said toll booth at least when said particular radio frequency communications device issuing said response to said initial wireless command is in proximity thereto. 
     
     
       99. The method of claim 97, wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       100. The method of claim 96, wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       101. The method of claim 96, wherein the financial transaction is for payment for goods or services. 
     
     
       102. The method of claim 101, further comprising:
 transmitting, from the master wireless device, a subsequent wireless command requesting one or more responses to continue the identification of the at least one of the plurality of radio frequency communications devices, the subsequent wireless command to identify a subset of the one or more first radio frequency communications devices and request the subset to reply with identification numbers.   
     
     
       103. The method of claim 96, wherein the response comprises further information about the particular radio frequency communications device. 
     
     
       104. The method of claim 96, wherein the identification number comprises a unique identification code that uniquely identifies the particular radio frequency communications device among the plurality of radio frequency communications devices. 
     
     
       105. The method of claim 96, wherein the identification number comprises a random number generated by the particular radio frequency communications device. 
     
     
       106. The method of claim 96, wherein the particular radio frequency communications device is to select a random value that determines a time slot in which the particular radio frequency communications device provides the master wireless device with the response used to identify the identification number. 
     
     
       107. The method of claim 96, wherein the particular radio frequency communications device is to select a random value that determines a time slot in which the particular radio frequency communications device provides the master wireless device with the response used to identify the identification number. 
     
     
       108. A radio frequency communications-based method of collecting a toll, comprising:
 transmitting, from a wireless master device disposed substantially within or proximate to a toll booth, a first wireless command to initiate identification of at least one of a population of radio frequency communications devices and a plurality of subsequent wireless commands to continue the identification of the at least one of the population of radio frequency communications devices, the first command including first bits that identify one or more first radio frequency communications devices, the first command requesting the one or more first radio frequency communications devices to reply with identifiers, the first command causing the one or more first radio frequency communications devices to generate respective ones of random values;   receiving, at the wireless master device, a reply to the first wireless command from a particular first radio frequency communications device, the reply including an identifier and having been received in a time slot determined at least in part according to one of the random values;   determining whether there is a collision in receiving the reply to the first wireless command;   if there is no collision, identifying from the received reply the identifier of the particular first radio frequency communications device; and   transmitting a second wireless command to individually identify the particular first radio frequency communications device using the identifier of the particular first radio frequency communications device, and to request the particular first radio frequency communications device to reply; and   debiting an account associated with the particular first radio frequency communications device based at least in part on a received reply of said particular first radio frequency communications device.   
     
     
       109. The method of claim 108, wherein said method further comprises operating said master wireless device disposed within or proximate to said toll booth at least when said particular first radio frequency communications device issuing said reply to the first wireless command is in proximity thereto. 
     
     
       110. The method of claim 108, wherein the debiting of the account comprises receiving a credit card number against which the toll can be charged. 
     
     
       111. The method of claim 108, wherein the debiting of the account comprises receiving a credit card number which can be charged. 
     
     
       112. The method of claim 108, further comprising:
 transmitting, from the master wireless device, a subsequent wireless command requesting response to continue the identification of the radio frequency communications devices, the subsequent wireless command to identify a subset of the population of radio frequency communications devices and request the subset to reply with respective identification numbers.   
     
     
       113. The method of claim 108, wherein the reply to the first wireless command comprises further information about the particular first radio frequency communications device. 
     
     
       114. The method of claim 108, wherein the identifier comprises a unique identification code that uniquely identifies the particular first radio frequency communications device from the population of radio frequency communications devices. 
     
     
       115. The method of claim 108, wherein the identifier comprises a random number generated by the particular first radio frequency communications device. 
     
     
       116. The method of claim 108, wherein the particular first radio frequency communications device is configured to select a random value that determines a time slot in which the particular first radio frequency communications device provides the master wireless device with the reply containing the identifier. 
     
     
       117. A radio frequency communications-based method of conducting a financial transaction, comprising:
 transmitting, from a wireless transmitter means having a communication field, an initial wireless command requesting one or more responses to start identification of at least one of a plurality of radio frequency means configured to transmit at least identification information, the initial command to be sent after the at least one radio frequency means are disposed in the communication field and before any of the at least one radio frequency means communicate any response or responses to the wireless transmitter means, the initial wireless command specifying means for identifying one or more first radio frequency means, and requesting the one or more first radio frequency means to reply with respective identification numbers to be used by the wireless transmitter means in subsequent communications to individually address the one or more first radio frequency means;   determining whether there is a collision in response to the initial wireless command;   identifying, from a received response to the initial command, an identification number of a particular radio frequency means, if there is no collision in response to the initial wireless command;   individually addressing the particular radio frequency means, by the wireless transmitter means, using the identification number identified from the response to the initial command, to request a reply from the particular radio frequency means;   identifying a financial account associated with an owner of the particular radio frequency means based at least in part on said identification number of said particular radio frequency means; and   debiting said account as part of said financial transaction.   
     
     
       118. The method of claim 117, wherein the financial transaction is associated with the payment of a toll, said wireless transmitter means is disposed within or proximate to a toll booth, and said method further comprises operating said wireless transmitter means at least when said particular radio frequency means issuing said response to said initial wireless command is in proximity thereto. 
     
     
       119. The method of claim 118, further comprising receiving a credit card number against which the toll can be charged. 
     
     
       120. The method of claim 117, further comprising receiving a credit card number which can be charged. 
     
     
       121. The method of claim 117, wherein the financial transaction is for payment for goods or services. 
     
     
       122. The method of claim 117, wherein the identification number comprises a unique identification code that uniquely identifies the particular radio frequency means among the plurality of radio frequency means. 
     
     
       123. The method of claim 117, wherein the identification number comprises a random number generated by the particular radio frequency means; and
 wherein the particular radio frequency means is configured to select a random value that determines a time slot in which that particular radio frequency means is to provide the wireless transmitter means with the response used to identify the identification number.