Recherche Images Maps Play YouTube Actualités Gmail Drive Plus »
Connexion
Les utilisateurs de lecteurs d'écran peuvent cliquer sur ce lien pour activer le mode d'accessibilité. Celui-ci propose les mêmes fonctionnalités principales, mais il est optimisé pour votre lecteur d'écran.

Brevets

  1. Recherche avancée dans les brevets
Numéro de publicationUSRE42900 E1
Type de publicationOctroi
Numéro de demandeUS 11/859,360
Date de publication8 nov. 2011
Date de dépôt21 sept. 2007
Date de priorité19 févr. 1998
Autre référence de publicationUS6118789, US6233369, US6307847, USRE41530, USRE41531, USRE43254
Numéro de publication11859360, 859360, US RE42900 E1, US RE42900E1, US-E1-RE42900, USRE42900 E1, USRE42900E1
InventeursClifton W. Wood, Jr.
Cessionnaire d'origineRound Rock Research, Llc
Exporter la citationBiBTeX, EndNote, RefMan
Liens externes: USPTO, Cession USPTO, Espacenet
Method of addressing messages and communications systems
US RE42900 E1
Résumé
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.
Images(4)
Previous page
Next page
Revendications(123)
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.
Description
CROSS REFERENCE TO RELATED APPLICATION

ThisMore than one reissue application has been filed for the reissue of U.S. Pat. No. 6,307,847, including the initial reissue application Ser. No. 10/693,696, filed Oct. 23, 2003, a continuation reissue application Ser. No. 11/859,364, filed Sep. 21, 2007, a continuation reissue application Ser. No. 12/493,542, filed Jun. 29, 2009, and the present continuation reissue application, which is a continuation application of U.S. patent application Ser. No. 10/693,696, filed Oct. 23, 2003 and titled “Method and Apparatus to Select Radio Frequency Identification Devices in Accordance With an Arbitration Scheme”, which is a reissue application of U.S. Pat. No. 6,307,847, issued from U.S. patent application Ser. No. 09/617,390, filed Jul. 17, 2000 and titled “Method of Addressing Messages and Communications System”, which is a Continuation continuation application of U.S. patent application Ser. No. 09/026,043, filed Feb. 19, 1998, and titled “Method of Addressing Messages and Communications System” now U.S. Pat. No. 6,118,789, each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This invention relates to communications protocols and to digital data communications. Still more particularly, the invention relates to data communications protocols in mediums such as radio communication or the like. The invention also relates to radio frequency identification devices for inventory control, object monitoring, determining the existence, location or movement of objects, or for remote automated payment.

BACKGROUND OF THE INVENTION

Communications protocols are used in various applications. For example, communications protocols can be used in electronic identification systems. As large numbers of objects are moved in inventory, product manufacturing, and merchandising operations, there is a continuous challenge to accurately monitor the location and flow of objects. Additionally, there is a continuing goal to interrogate the location of objects in an inexpensive and streamlined manner. One way of tracking objects is with an electronic identification system.

One presently available electronic identification system utilizes a magnetic coupling system. In some cases, an identification device may be provided with a unique identification code in order to distinguish between a number of different devices. Typically, the devices are entirely passive (have no power supply), which results in a small and portable package. However, such identification systems are only capable of operation over a relatively short range, limited by the size of a magnetic field used to supply power to the devices and to communicate with the devices.

Another wireless electronic identification system utilizes a large active transponder device affixed to an object to be monitored which receives a signal from an interrogator. The device receives the signal, then generates and transmits a responsive signal. The interrogation signal and the responsive signal are typically radio-frequency (RF) signals produced by an RF transmitter circuit. Because active devices have their own power sources, and do not need to be in close proximity to an interrogator or reader to receive power via magnetic coupling. Therefore, active transponder devices tend to be more suitable for applications requiring tracking of a tagged device that may not be in close proximity to an interrogator. For example, active transponder devices tend to be more suitable for inventory control or tracking.

Electronic identification systems can also be used for remote payment. For example, when a radio frequency identification device passes an interrogator at a toll booth, the toll booth can determine the identity of the radio frequency identification device, and thus of the owner of the device, and debit an account held by the owner for payment of toll or can receive a credit card number against which the toll can be charged. Similarly, remote payment is possible for a variety of other goods or services.

A communication system typically includes two transponders: a commander station or interrogator, and a responder station or transponder device which replies to the interrogator.

If the interrogator has prior knowledge of the identification number of a device which the interrogator is looking for, it can specify that a response is requested only from the device with that identification number. Sometimes, such information is not available. For example, there are occasions where the interrogator is attempting to determine which of multiple devices are within communication range.

When the interrogator sends a message to a transponder device requesting a reply, there is a possibility that multiple transponder devices will attempt to respond simultaneously, causing a collision, and thus causing an erroneous message to be received by the interrogator. For example, if the interrogator sends out a command requesting that all devices within a communications range identify themselves, and gets a large number of simultaneous replies, the interrogator may not be able to interpret any of these replies. Thus, arbitration schemes are employed to permit communications free of collisions.

In one arbitration scheme or system, described in commonly assigned U.S. Pat. Nos. 5,627,544; 5,583,850; 5,500,650; and 5,365,551, all to Snodgrass et al. and all incorporated herein by reference, the interrogator sends a command causing each device of a potentially large number of responding devices to select a random number from a known range and use it as that device's arbitration number. By transmitting requests for identification to various subsets of the full range of arbitration numbers, and checking for an error-free response, the interrogator determines the arbitration number of every responder station capable of communicating at the same time. Therefore, the interrogator is able to conduct subsequent uninterrupted communication with devices, one at a time, by addressing only one device.

Another arbitration scheme is referred to as the Aloha or slotted Aloha scheme. This scheme is discussed in various references relating to communications, such as Digital Communications: Fundamentals and Applications, Bernard Sklar, published January 1988 by Prentice Hall. In this type of scheme, a device will respond to an interrogator using one of many time domain slots selected randomly by the device. A problem with the Aloha scheme is that if there are many devices, or potentially many devices in the field (i.e. in communications range, capable of responding) then there must be many available slots or many collisions will occur. Having many available slots slows down replies. If the magnitude of the number of devices in a field is unknown, then many slots are needed. This results in the system slowing down significantly because the reply time equals the number of slots multiplied by the time period required for one reply.

An electronic identification system which can be used as a radio frequency identification device, arbitration schemes, and various applications for such devices are described in detail in commonly assigned U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996, and now U.S. Pat. No. 6,130,602, which is incorporated herein by reference.

SUMMARY OF THE INVENTION

The invention provides a wireless identification device configured to provide a signal to identify the device in response to an interrogation signal.

One aspect of the invention provides a method of establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices. The method comprises 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 is defined for the tree search method. The tree has 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. In one aspect of the invention, the method further comprises 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. In another aspect of the invention, the method further comprises 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.

Another aspect of the invention provides 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 have a unique identification number. The interrogator is 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. The interrogator is configured to start the tree search at a selectable level of the search tree.

One aspect of the invention provides a radio frequency identification device comprising an integrated circuit including a receiver, a transmitter, and a microprocessor. In one embodiment, the integrated circuit is a monolithic single die single metal layer integrated circuit including the receiver, the transmitter, and the microprocessor. The device of this embodiment includes an active transponder, instead of a transponder which relies on magnetic coupling for power, and therefore has a much greater range.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below with reference to the following accompanying drawings.

FIG. 1 is a high level circuit schematic showing an interrogator and a radio frequency identification device embodying the invention.

FIG. 2 is a front view of a housing, in the form of a badge or card, supporting the circuit of FIG. 1 according to one embodiment the invention.

FIG. 3 is a front view of a housing supporting the circuit of FIG. 1 according to another embodiment of the invention.

FIG. 4 is a diagram illustrating a tree splitting sort method for establishing communication with a radio frequency identification device in a field of a plurality of such devices.

FIG. 5. is a diagram illustrating a modified tree splitting sort method for establishing communication with a radio frequency identification device in a field of a plurality of such devices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).

FIG. 1 illustrates a wireless identification device 12 in accordance with one embodiment of the invention. In the illustrated embodiment, the wireless identification device is a radio frequency data communication device 12, and includes RFID circuitry 16. The device 12 further includes at least one antenna 14 connected to the circuitry 16 for wireless or radio frequency transmission and reception by the circuitry 16. In the illustrated embodiment, the RFID circuitry is defined by an integrated circuit as described in the above-incorporated patent application Ser. No. 08/705,043, filed Aug. 29, 1996, now U.S. Pat. No. 6,130,602. Other embodiments are possible. A power source or supply 18 is connected to the integrated circuit 16 to supply power to the integrated circuit 16. In one embodiment, the power source 18 comprises a battery.

The device 12 transmits and receives radio frequency communications to and from an interrogator 26. An exemplary interrogator is described in commonly assigned U.S. patent application Ser. No. 08/907,689, filed Aug. 8, 1997 and, now U.S. Pat. No. 6,289,209, which is incorporated herein by reference. Preferably, the interrogator 26 includes an antenna 28, as well as dedicated transmitting and receiving circuitry, similar to that implemented on the integrated circuit 16.

Generally, the interrogator 26 transmits an interrogation signal or command 27 via the antenna 28. The device 12 receives the incoming interrogation signal via its antenna 14. Upon receiving the signal 27, the device 12 responds by generating and transmitting a responsive signal or reply 29. The responsive signal 29 typically includes information that uniquely identifies, or labels the particular device 12 that is transmitting, so as to identify any object or person with which the device 12 is associated.

Although only one device 12 is shown in FIG. 1, typically there will be multiple devices 12 that correspond with the interrogator 26, and the particular devices 12 that are in communication with the interrogator 26 will typically change over time. In the illustrated embodiment in FIG. 1, there is no communication between multiple devices 12. Instead, the devices 12 respectively communicate with the interrogator 26. Multiple devices 12 can be used in the same field of an interrogator 26 (i.e., within communications range of an interrogator 26).

The radio frequency data communication device 12 can be included in any appropriate housing or packaging. Various methods of manufacturing housings are described in commonly assigned U.S. patent application Ser. No. 08/800,037, filed Feb. 13, 1997, and now U.S. Pat. No. 5,988,510, which is incorporated herein by reference.

FIG. 2 shows but one embodiment in the form of a card or badge 19 including a housing 11 of plastic or other suitable material supporting the device 12 and the power supply 18. In one embodiment, the front face of the badge has visual identification features such as graphics, text, information found on identification or credit cards, etc.

FIG. 3 illustrates but one alternative housing supporting the device 12. More particularly, FIG. 3 shows a miniature housing 20 encasing the device 12 and power supply 18 to define a tag which can be supported by an object (e.g., hung from an object, affixed to an object, etc.). Although two particular types of housings have been disclosed, the device 12 can be included in any appropriate housing.

If the power supply 18 is a battery, the battery can take any suitable form. Preferably, the battery type will be selected depending on weight, size, and life requirements for a particular application. In one embodiment, the battery 18 is a thin profile button-type cell forming a small, thin energy cell more commonly utilized in watches and small electronic devices requiring a thin profile. A conventional button-type cell has a pair of electrodes, an anode formed by one face and a cathode formed by an opposite face. In an alternative embodiment, the power source 18 comprises a series connected pair of button type cells. Instead of using a battery, any suitable power source can be employed.

The circuitry 16 further includes a backscatter transmitter and is configured to provide a responsive signal to the interrogator 26 by radio frequency. More particularly, the circuitry 16 includes a transmitter, a receiver, and memory such as is described in U.S. patent application Ser. No. 08/705,043, now U.S. Pat. No. 6,130,602.

Radio frequency identification has emerged as a viable and affordable alternative to tagging or labeling small to large quantities of items. The interrogator 26 communicates with the devices 12 via an electromagnetic link, such as via an RF link (e.g., at microwave frequencies, in one embodiment), so all transmissions by the interrogator 26 are heard simultaneously by all devices 12 within range.

If the interrogator 26 sends out a command requesting that all devices 12 within range identify themselves, and gets a large number of simultaneous replies, the interrogator 26 may not be able to interpret any of these replies. Therefore, arbitration schemes are provided.

If the interrogator 26 has prior knowledge of the identification number of a device 12 which the interrogator 26 is looking for, it can specify that a response is requested only from the device 12 with that identification number. To target a command at a specific device 12, (i.e., to initiate point-on-point communication), the interrogator 26 must send a number identifying a specific device 12 along with the command. At start-up, or in a new or changing environment, these identification numbers are not known by the interrogator 26. Therefore, the interrogator 26 must identify all devices 12 in the field (within communication range) such as by determining the identification numbers of the devices 12 in the field. After this is accomplished, point-to-point communication can proceed as desired by the interrogator 26.

Generally speaking, RFID systems are a type of multiaccess communication system. The distance between the interrogator 26 and devices 12 within the field is typically fairly short (e.g., several meters), so packet transmission time is determined primarily by packet size and baud rate. Propagation delays are negligible. In such systems, there is a potential for a large number of transmitting devices 12 and there is a need for the interrogator 26 to work in a changing environment, where different devices 12 are swapped in and out frequently (e.g., as inventory is added or removed). In such systems, the inventors have determined that the use of random access methods work effectively for contention resolution (i.e., for dealing with collisions between devices 12 attempting to respond to the interrogator 26 at the same time).

RFID systems have some characteristics that are different from other communications systems. For example, one characteristic of the illustrated RFID systems is that the devices 12 never communicate without being prompted by the interrogator 26. This is in contrast to typical multiaccess systems where the transmitting units operate more independently. In addition, contention for the communication medium is short lived as compared to the ongoing nature of the problem in other multiaccess systems. For example, in a RFID system, after the devices 12 have been identified, the interrogator can communicate with them in a point-to-point fashion. Thus, arbitration in a RFID system is a transient rather than steady-state phenomenon. Further, the capability of a device 12 is limited by practical restrictions on size, power, and cost. The lifetime of a device 12 can often be measured in terms of number of transmissions before battery power is lost. Therefore, one of the most important measures of system performance in RFID arbitration is total time required to arbitrate a set of devices 12. Another measure is power consumed by the devices 12 during the process. This is in contrast to the measures of throughput and packet delay in other types of multiaccess systems.

FIG. 4 illustrates one arbitration scheme that can be employed for communication between the interrogator and devices 12. Generally, the interrogator 26 sends a command causing each device 12 of a potentially large number of responding devices 12 to select a random number from a known range and use it as that device's arbitration number. By transmitting requests for identification to various subsets of the full range of arbitration numbers, and checking for an error-free response, the interrogator 26 determines the arbitration number of every responder station capable of communicating at the same time. Therefore, the interrogator 26 is able to conduct subsequent uninterrupted communication with devices 12, one at a time, by addressing only one device 12.

Three variables are used: an arbitration value (AVALUE), an arbitration mask (AMASK), and a random value ID (RV). The interrogator sends an Identify command (IdentifyCmnd) causing each device of a potentially large number of responding devices to select a random number from a known range and use it as that device's arbitration number. The interrogator sends an arbitration value (AVALUE) and an arbitration mask (AMASK) to a set of devices 12. The receiving devices 12 evaluate the following equation: (AMASK & AVALUE)==(AMASK & RV) wherein “&” is a bitwise AND function, and wherein “==” is an equality function. If the equation evaluates to “1” (TRUE), then the device 12 will reply. If the equation evaluates to “0” (FALSE), then the device 12 will not reply. By performing this in a structured manner, with the number of bits in the arbitration mask being increased by one each time, eventually a device 12 will respond with no collisions. Thus, a binary search tree methodology is employed.

An example using actual numbers will now be provided using only four bits, for simplicity, reference being made to FIG. 4. In one embodiment, sixteen bits are used for AVALUE and AMASK. Other numbers of bits can also be employed depending, for example, on the number of devices 12 expected to be encountered in a particular application, on desired cost points, etc.

Assume, for this example, that there are two devices 12 in the field, one with a random value (RV) of 1100 (binary), and another with a random value (RV) of 1010 (binary). The interrogator is trying to establish communications without collisions being caused by the two devices 12 attempting to communicate at the same time.

The interrogator sets AVALUE to 0000 (or “don't care” for all bits, as indicated by the character “X” in FIG. 4) and AMASK to 0000. The interrogator transmits a command to all devices 12 requesting that they identify themselves. Each of the devices 12 evaluate (AMASK & AVALUE)==(AMASK & RV) using the random value RV that the respective devices 12 selected. If the equation evaluates to “1” (TRUE), then the device 12 will reply. If the equation evaluates to “0” (FALSE), then the device 12 will not reply. In the first level of the illustrated tree, AMASK is 0000 and anything bitwise ANDed with all zeros results in all zeros, so both the devices 12 in the field respond, and there is a collision.

Next, the interrogator sets AMASK to 0001 and AVALUE to 0000 and transmits an identify command. Both devices 12 in the field have a zero for their least significant bit, and (AMASK & AVALUE)==(AMASK & RV) will be true for both devices 12. For the device 12 with a random value of 1100, the left side of the equation is evaluated as follows (0001 & 0000)=0000. The right side is evaluated as (0001 & 1100)=0000. The left side equals the right side, so the equation is true for the device 12 with the random value of 1100. For the device 12 with a random value of 1010, the left side of the equation is evaluated as (0001 & 0000)=0000. The right side is evaluated as (0001 & 1010)=0000. The left side equals the right side, so the equation is true for the device 12 with the random value of 1010. Because the equation is true for both devices 12 in the field, both devices 12 in the field respond, and there is another collision.

Recursively, the interrogator next sets AMASK to 0011 with AVALUE still at 0000 and transmits an Identify command. (AMASK & AVALUE)==(AMASK & RV) is evaluated for both devices 12. For the device 12 with a random value of 1100, the left side of the equation is evaluated as follows (0011 & 0000)=0000. The right side is evaluated as (0011 & 1100)=0000. The left side equals the right side, so the equation is true for the device 12 with the random value of 1100, so this device 12 responds. For the device 12 with a random value of 1010, the left side of the equation is evaluated as (0011 & 0000)=0000. The right side is evaluated as (0011 & 1010)=0010. The left side does not equal the right side, so the equation is false for the device 12 with the random value of 1010, and this device 12 does not respond. Therefore, there is no collision, and the interrogator can determine the identity (e.g., an identification number) for the device 12 that does respond.

De-recursion takes place, and the devices 12 to the right for the same AMASK level are accessed when AVALUE is set at 0010, and AMASK is set to 0011.

The device 12 with the random value of 1010 receives a command and evaluates the equation (AMASK & AVALUE)==(AMASK & RV). The left side of the equation is evaluated as (0011 & 0010)=0010. The right side of the equation is evaluated as (0011 & 1010)=0010. The right side equals the left side, so the equation is true for the device 12 with the random value of 1010. Because there are no other devices 12 in the subtree, a good reply is returned by the device 12 with the random value of 1010. There is no collision, and the interrogator 26 can determine the identity (e.g., an identification number) for the device 12 that does respond.

By recursion, what is meant is that a function makes a call to itself. In other words, the function calls itself within the body of the function. After the called function returns, de-recursion takes place and execution continues at the place just after the function call; i.e. at the beginning of the statement after the function call.

For instance, consider a function that has four statements (numbered 1,2,3,4 ) in it, and the second statement is a recursive call. Assume that the fourth statement is a return statement. The first time through the loop (iteration 1) the function executes the statement 2 and (because it is a recursive call) calls itself causing iteration 2 to occur. When iteration 2 gets to statement 2, it calls itself making iteration 3. During execution in iteration 3 of statement 1, assume that the function does a return. The information that was saved on the stack from iteration 2 is loaded and the function resumes execution at statement 3 (in iteration 2), followed by the execution of statement 4 which is also a return statement. Since there are no more statements in the function, the function de-recurses to iteration 1. Iteration 1, had previously recursively called itself in statement 2. Therefore, it now executes statement 3 (in iteration 1 ). Following that it executes a return at statement 4. Recursion is known in the art.

Consider the following code which can be used to implement operation of the method shown in FIG. 4 and described above.

Arbitrate(AMASK, AVALUE)
    {
    collision=IdentifyCmnd(AMASK, AVALUE)
    if (collision) then
       {
         /* recursive call for left side */
        Arbitrate((AMASK>>1)+1, AVALUE)
         /* recursive call for right side */
      Arbitrate((AMASK>>1)+1, AVALUE+(AMASK+1))
     } /* endif */
}/* return */

The symbol “<<” represents a bitwise left shift. “<<” means shift left by one place. Thus, 0001<<1 would be 0010. Note, however, that AMASK is originally called with a value of zero, and 0000<<1 is still 0000. Therefore, for the first recursive call, AMASK=(AMASK<<1)+1. So for the first recursive call, the value of AMASK is 0000+0001=0001. For the second call, AMASK=(0001<<)+1=0010+1=0011. For the third recursive call, AMASK=(0011<<1)+1=0110+1=0111.

The routine generates values for AMASK and AVALUE to be used by the interrogator in an identify command “IdentifyCmnd.” Note that the routine calls itself if there is a collision. De-recursion occurs when there is no collision. AVALUE and AMASK would have values such as the following assuming collisions take place all the way down to the bottom of the tree.

AVALUE AMASK
0000 0000
0000 0001
0000 0011
0000 0111
0000  1111*
1000  1111*
0100 0111
0100  1111*
1100  1111*

This sequence of AMASK, AVALUE binary numbers assumes that there are collisions all the way down to the bottom of the tree, at which point the Identify command sent by the interrogator is finally successful so that no collision occurs. Rows in the table for which the interrogator is successful in receiving a reply without collision are marked with the symbol “*”. Note that if the Identify command was successful at, for example, the third line in the table then the interrogator would stop going down that branch of the tree and start down another, so the sequence would be as shown in the following table.

AVALUE AMASK
0000 0000
0000 0001
0000  0011*
0010 0011
. . . . . .

This method is referred to as a splitting method. It works by splitting groups of colliding devices 12 into subsets that are resolved in turn. The splitting method can also be viewed as a type of tree search. Each split moves the method one level deeper in the tree.

Either depth-first or breadth-first traversals of the tree can be employed Depth first traversals are performed by using recursion, as is employed in the code listed above. Breadth-first traversals are accomplished by using a queue instead of recursion. The following is an example of code for performing a breadth-first traversal.

Arbitrate(AMASK, AVALUE)
    {
    enqueue(0,0)
    while (queue != empty)
     (AMASK,AVALUE) = dequeue( )
     collision=IdentifyCmnd(AMASK, AVALUE)
     if (collision) then
     {
      TEMP = AMASK+1
      NEW_AMASK = (AMASK>>1)+1
      enqueue(NEW_AMASK, AVALUE)
      enqueue(NEW_AMASK, AVALUE+TEMP)
      } /* endif */
    endwhile
    }/* return */

The symbol “!=” means not equal to. AVALUE and AMASK would have values such as those indicated in the following table for such code.

AVALUE AMASK
0000 0000
0000 0001
0001 0001
0000 0011
0010 0011
0001 0011
0011 0011
0000 0111
0100 0111
. . . . . .

Rows in the table for which the interrogator is successful in receiving a reply without collision are marked with the symbol “*”.

FIG. 5 illustrates an embodiment wherein the interrogator 26 starts the tree search at a selectable level of the search tree. The search tree has a plurality of nodes 51, 52, 53, 54 etc. at respective levels. The size of subgroups of random values decrease in size by half with each node descended. The upper bound of the number of devices 12 in the field (the maximum possible number of devices that could communicate with the interrogator) is determined, and the tree search method is started at a level 32, 34, 36, 38, or 40 in the tree depending on the determined upper bound. In one embodiment, the maximum number of devices 12 potentially capable of responding to the interrogator is determined manually and input into the interrogator 26 via an input device such as a keyboard, graphical user interface, mouse, or other interface. The level of the search tree on which to start the tree search is selected based on the determined maximum possible number of wireless identification devices that could communicate with the interrogator.

The tree search is started at a level determined by taking the base two logarithm of the determined maximum possible number. More particularly, the tree search is started at a level determined by taking the base two logarithm of the power of two nearest the determined maximum possible number of devices 12. The level of the tree containing all subgroups of random values is considered level zero (see FIG. 5), and lower levels are numbered 1, 2, 3, 4, etc. consecutively.

By determining the upper bound of the number of devices 12 in the field, and starting the tree search at an appropriate level, the number of collisions is reduced, the battery life of the devices 12 is increased, and arbitration time is reduced.

For example, for the search tree shown in FIG. 5, if it is known that there are seven devices 12 in the field, starting at node 51 (level 0 ) results in a collision. Starting at level 1 (nodes 52 and 53 ) also results in a collision. The same is true for nodes 54, 55, 56, and 57 in level 2. If there are seven devices 12 in the field, the nearest power of two to seven is the level at which the tree search should be started. Log2 8=3, so the tree search should be started at level 3 if there are seven devices 12 in the field.

AVALUE and AMASK would have values such as the following assuming collisions take place from level 3 all the way down to the bottom of the tree.

AVALUE AMASK
0000 0111 
0000 1111*
1000 1111*
0100 0111 
0100 1111*
1100 1111*

Rows in the table for which the interrogator is successful in receiving a reply without collision are marked with the symbol “*”.

In operation, the interrogator transmits a command requesting devices 12 having random values RV within a specified group of random values to respond, the specified group being chosen in response to the determined maximum number. Devices 12 receiving the command respectively determine if their chosen random values fall within the specified group and, if so, send a reply to the interrogator. The interrogator determines if a collision occurred between devices that sent a reply and, if so, creates a new, smaller, specified group, descending in the tree, as described above in connection with FIG. 4.

Another arbitration method that can be employed is referred to as the “Aloha” method. In the Aloha method, every time a device 12 is involved in a collision, it waits a random period of time before retransmitting. This method can be improved by dividing time into equally sized slots and forcing transmissions to be aligned with one of these slots. This is referred to as “slotted Aloha.” In operation, the interrogator asks all devices 12 in the field to transmit their identification numbers in the next time slot. If the response is garbled, the interrogator informs the devices 12 that a collision has occurred, and the slotted Aloha scheme is put into action. This means that each device 12 in the field responds within an arbitrary slot determined by a randomly selected value. In other words, in each successive time slot, the devices 12 decide to transmit their identification number with a certain probability.

The Aloha method is based on a system operated by the University of Hawaii. In 1971, the University of Hawaii began operation of a system named Aloha. A communication satellite was used to interconnect several university computers by use of a random access protocol. The system operates as follows. Users or devices transmit at any time they desire. After transmitting, a user listens for an acknowledgment from the receiver or interrogator. Transmissions from different users will sometimes overlap in time (collide), causing reception errors in the data in each of the contending messages. The errors are detected by the receiver, and the receiver sends a negative acknowledgment to the users. When a negative acknowledgment is received, the messages are retransmitted by the colliding users after a random delay. If the colliding users attempted to retransmit without the random delay, they would collide again. If the user does not receive either an acknowledgment or a negative acknowledgment within a certain amount of time, the user “times out” and retransmits the message.

There is a scheme known as slotted Aloha which improves the Aloha scheme by requiring a small amount of coordination among stations. In the slotted Aloha scheme, a sequence of coordination pulses is broadcast to all stations (devices). As is the case with the pure Aloha scheme, packet lengths are constant. Messages are required to be sent in a slot time between synchronization pulses, and can be started only at the beginning of a time slot. This reduces the rate of collisions because only messages transmitted in the same slot can interfere with one another. The retransmission mode of the pure Aloha scheme is modified for slotted Aloha such that if a negative acknowledgment occurs, the device retransmits after a random delay of an integer number of slot times.

Aloha methods are described in a commonly assigned patent application naming Clifton W. Wood, Jr. as an inventor, U.S. patent application Ser. No. 09/026,248, filed Feb. 19, 1998, titled “Method of Addressing Messages and Communications System,” filed concurrently herewith, and, now U.S. Pat. No. 6,275,476, which is incorporated herein by reference.

In one alternative embodiment, an Aloha method (such as the method described in the commonly assigned patent application mentioned above) is combined with determining the upper bound on a set of devices and starting at a level in the tree depending on the determined upper bound, such as by combining an Aloha method with the method shown and described in connection with FIG. 5. For example, in one embodiment, devices 12 sending a reply to the interrogator 26 do so within a randomly selected time slot of a number of slots.

In another embodiment, levels of the search tree are skipped. Skipping levels in the tree, after a collision caused by multiple devices 12 responding, reduces the number of subsequent collisions without adding significantly to the number of no replies. In real-time systems, it is desirable to have quick arbitration sessions on a set of devices 12 whose unique identification numbers are unknown. Level skipping reduces the number of collisions, both reducing arbitration time and conserving battery life on a set of devices 12. In one embodiment, every other level is skipped. In alternative embodiments, more than one level is skipped each time.

The trade off that must be considered in determining how many (if any) levels to skip with each decent down the tree is as follows. Skipping levels reduces the number of collisions, thus saving battery power in the devices 12. Skipping deeper (skipping more than one level) further reduces the number of collisions. The more levels that are skipped, the greater the reduction in collisions. However, skipping levels results in longer search times because the number of queries (Identify commands) increases. The more levels that are skipped, the longer the search times. Skipping just one level has an almost negligible effect on search time, but drastically reduces the number of collisions. If more than one level is skipped, search time increases substantially. Skipping every other level drastically reduces the number of collisions and saves battery power without significantly increasing the number of queries.

Level skipping methods are described in a commonly assigned patent application 09/026,045 naming Clifton W. Wood, Jr. and Don Hush as inventors, titled “Method of Addressing Messages, Method of Establishing Wireless Communications, and Communications Systems,” filed concurrently herewith, now U.S. Pat. No. 6,072,801, and incorporated herein by reference.

In one alternative embodiment, a level skipping method is combined with determining the upper bound on a set of devices and starting at a level in the tree depending on the determined upper bound, such as by combining a level skipping method with the method shown and described in connection with FIG. 5.

In yet another alternative embodiment, both a level skipping method and an Aloha method (as described in the commonly assigned applications described above) are combined with the method shown and described in connection with FIG. 5.

In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Citations de brevets
Brevet cité Date de dépôt Date de publication Déposant Titre
US407563224 mai 197621 févr. 1978The United States Of America As Represented By The United States Department Of EnergyInterrogation, and detection system
US476177811 avr. 19852 août 1988Massachusetts Institute Of TechnologyCoder-packetizer for random accessing in digital communication with multiple accessing
US47960235 déc. 19863 janv. 1989King Robert EStabilized binary tree protocol
US479905914 mars 198617 janv. 1989Enscan, Inc.Automatic/remote RF instrument monitoring system
US48455048 avr. 19874 juil. 1989M/A-Com, Inc.Mobile radio network for nationwide communications
US48624532 oct. 198729 août 1989The Marconi Company LimitedCommunication system
US492618229 mai 198715 mai 1990Sharp Kabushiki KaishaMicrowave data transmission apparatus
US49550188 nov. 19884 sept. 1990Echelon Systems CorporationProtocol for network having plurality of intelligent cells
US49691468 nov. 19886 nov. 1990Echelon Systems CorporationProtocol for network having a plurality of intelligent cells
US501981312 avr. 198828 mai 1991N.V. Nederlandsche Apparatenfabriek NedapSystem for the contactless exchange of data
US50254869 déc. 198818 juin 1991Dallas Semiconductor CorporationWireless communication system with parallel polling
US504606612 févr. 19873 sept. 1991Telesystems Slw Inc.Wireless local area network
US50559683 juil. 19898 oct. 1991Sony CorporationThin electronic device having an integrated circuit chip and a power battery and a method for producing same
US512140727 sept. 19909 juin 1992Pittway CorporationSpread spectrum communications system
US512469716 oct. 198923 juin 1992Motorola, Inc.Acknowledge-back pager
US514269424 juil. 198925 août 1992Motorola, Inc.Reporting unit
US514431324 avr. 19911 sept. 1992Steffen KirknesMethod for processing transmitted and reflected signals for removing unwanted signals and noise from wanted signals
US514466825 janv. 19911 sept. 1992Motorola, Inc.Signal overlap detection in a communication system
US51501146 nov. 199022 sept. 1992U.S. Philips CorporationPolling-type information transmission system
US515031030 août 198922 sept. 1992Consolve, Inc.Method and apparatus for position detection
US516498526 oct. 198817 nov. 1992Nysen Paul APassive universal communicator system
US51685105 avr. 19891 déc. 1992Comsource SystemsSpread spectrum-time diversity communications systems and transceivers for multidrop area networks
US519486015 nov. 199016 mars 1993The General Electric Company, P.L.C.Radio telemetry systems with channel selection
US523164616 mars 199227 juil. 1993Kyros CorporationCommunications system
US526692530 sept. 199130 nov. 1993Westinghouse Electric Corp.Electronic identification tag interrogation method
US53074637 déc. 199226 avr. 1994Allen-Bradley Company, Inc.Programmable controller communication module
US536555115 déc. 199215 nov. 1994Micron Technology, Inc.Data communication transceiver using identification protocol
US537350330 avr. 199313 déc. 1994Information Technology, Inc.Group randomly addressed polling method
US54492967 mars 199412 sept. 1995Cabel-Con, Inc. UsaCable connector apparatus for preventing radiation leakage
US546162724 déc. 199124 oct. 1995Rypinski; Chandos A.Access protocol for a common channel wireless network
US547941630 sept. 199326 déc. 1995Micron Technology, Inc.Apparatus and method for error detection and correction in radio frequency identification device
US550065015 déc. 199219 mars 1996Micron Technology, Inc.Data communication method using identification protocol
US553070231 mai 199425 juin 1996Ludwig KippSystem for storage and communication of information
US555054712 sept. 199427 août 1996International Business Machines CorporationMultiple item radio frequency tag identification protocol
US558385021 juin 199410 déc. 1996Micron Technology, Inc.Data communication system using identification protocol
US56087398 sept. 19954 mars 1997Micron Technology, Inc.Apparatus and method for error detection and correction in radio frequency identification device
US561964830 nov. 19948 avr. 1997Lucent Technologies Inc.Message filtering techniques
US56214127 juin 199515 avr. 1997Texas Instruments IncorporatedMulti-stage transponder wake-up, method and structure
US562562815 mars 199529 avr. 1997Hughes ElectronicsAloha optimization
US562754418 mars 19966 mai 1997Micron Technology, Inc.Data communication method using identification protocol
US56401518 nov. 199317 juin 1997Texas Instruments IncorporatedCommunication system for communicating with tags
US564929619 juin 199515 juil. 1997Lucent Technologies Inc.Full duplex modulated backscatter system
US5686902 *23 avr. 199611 nov. 1997Texas Instruments IncorporatedCommunication system for communicating with tags
US579094619 avr. 19954 août 1998Rotzoll; Robert R.Wake up device for a communications system
US58055862 mai 19958 sept. 1998Motorola Inc.Method, device and data communication system for multilink polling
US58417707 oct. 199624 nov. 1998Micron Technology, Inc.Data communication system using indentification protocol
US591467127 févr. 199722 juin 1999Micron Communications, Inc.System and method for locating individuals and equipment, airline reservation system, communication system
US593656018 juil. 199710 août 1999Fujitsu LimitedData compression method and apparatus performing high-speed comparison between data stored in a dictionary window and data to be compressed
US5940006 *12 déc. 199517 août 1999Lucent Technologies Inc.Enhanced uplink modulated backscatter system
US59429879 août 199624 août 1999Intermec Ip Corp.Radio frequency identification system with write broadcast capability
US595292231 déc. 199614 sept. 1999Lucent Technologies Inc.In-building modulated backscatter system
US596647123 déc. 199712 oct. 1999United States Of AmericaMethod of codebook generation for an amplitude-adaptive vector quantization system
US597407813 févr. 199726 oct. 1999Micron Technology, Inc.Modulated spread spectrum in RF identification systems method
US598851013 févr. 199723 nov. 1999Micron Communications, Inc.Tamper resistant smart card and method of protecting data in a smart card
US603845529 août 199614 mars 2000Cirrus Logic, Inc.Reverse channel reuse scheme in a time shared cellular communication system
US606134419 févr. 19989 mai 2000Micron Technology, Inc.Method of addressing messages and communications system
US607280119 févr. 19986 juin 2000Micron Technology, Inc.Method of addressing messages, method of establishing wireless communications, and communications system
US607597318 mai 199813 juin 2000Micron Technology, Inc.Method of communications in a backscatter system, interrogator, and backscatter communications system
US6097292 *19 sept. 19971 août 2000Cubic CorporationContactless proximity automated data collection system and method
US610433319 déc. 199615 août 2000Micron Technology, Inc.Methods of processing wireless communication, methods of processing radio frequency communication, and related systems
US611878919 févr. 199812 sept. 2000Micron Technology, Inc.Method of addressing messages and communications system
US6130602 *29 août 199610 oct. 2000Micron Technology, Inc.Radio frequency data communications device
US613062331 déc. 199610 oct. 2000Lucent Technologies Inc.Encryption for modulated backscatter systems
US6150921 *17 oct. 199721 nov. 2000Pinpoint CorporationArticle tracking system
US615763310 juin 19965 déc. 2000At&T Wireless Sucs. Inc.Registration of mobile packet data terminals after disaster
US616947423 avr. 19982 janv. 2001Micron Technology, Inc.Method of communications in a backscatter system, interrogator, and backscatter communications system
US6177858 *27 nov. 199623 janv. 2001Pierre RaimbaultMethod for remotely interrogating tags, and station and tag implementing said method
US618530713 janv. 19986 févr. 2001Gilbarco Inc.Cryptography security for remote dispenser transactions
US61922223 sept. 199820 févr. 2001Micron Technology, Inc.Backscatter communication systems, interrogators, methods of communicating in a backscatter system, and backscatter communication methods
US621613220 nov. 199710 avr. 2001International Business Machines CorporationMethod and system for matching consumers to events
US622630018 avr. 20001 mai 2001Micron Technology, Inc.Method of addressing messages, and establishing communications using a tree search technique that skips levels
US622998726 avr. 20008 mai 2001Micron Technology, Inc.Method of communications in a backscatter system, interrogator, and backscatter communications system
US6243012 *31 déc. 19965 juin 2001Lucent Technologies Inc.Inexpensive modulated backscatter reflector
US626596229 juin 200024 juil. 2001Micron Technology, Inc.Method for resolving signal collisions between multiple RFID transponders in a field
US626596323 juin 200024 juil. 2001Micron Technology, Inc.Methods of processing wireless communication, methods of processing radio frequency communication, and related systems
US627547619 févr. 199814 août 2001Micron Technology, Inc.Method of addressing messages and communications system
US628218624 avr. 200028 août 2001Micron Technology, Inc.Method of addressing messages and communications system
US6288629 *23 mai 199711 sept. 2001Intermec Ip Corp.Method of using write—ok flag for radio frequency (RF) transponders (RF Tags)
US62892098 août 199711 sept. 2001Micron Technology, Inc.Wireless communication system, radio frequency communications system, wireless communications method, radio frequency communications method
US630784717 juil. 200023 oct. 2001Micron Technology, Inc.Method of addressing messages and communications systems
US630784831 janv. 200123 oct. 2001Micron Technology, Inc.Method of addressing messages, method of establishing wireless communications, and communications system
US632421124 avr. 199827 nov. 2001Micron Technology, Inc.Interrogators communication systems communication methods and methods of processing a communication signal
US6415439 *4 févr. 19972 juil. 2002Microsoft CorporationProtocol for a wireless control system
US645972624 avr. 19981 oct. 2002Micron Technology, Inc.Backscatter interrogators, communication systems and backscatter communication methods
US64834279 mars 200019 nov. 2002Rf Technologies, Inc.Article tracking system
US65669973 déc. 199920 mai 2003Hid CorporationInterference control method for RFID systems
US657048722 avr. 199927 mai 2003Axcess Inc.Distributed tag reader system and method
US67073769 août 200216 mars 2004Sensormatic Electronics CorporationPulsed power method for increased read range for a radio frequency identification reader
US671455921 sept. 200130 mars 2004Broadcom CorporationRedundant radio frequency network having a roaming terminal communication protocol
US67716349 avr. 19993 août 2004At&T Wireless Services, Inc.Registration of mobile packet data terminals after disaster
US6778096 *17 nov. 199717 août 2004International Business Machines CorporationMethod and apparatus for deploying and tracking computers
US678478715 mai 200031 août 2004Btg International LimitedIdentification system
US68505108 mai 20021 févr. 2005Broadcom CorporationHierarchical data collection network supporting packetized voice communications among wireless terminals and telephones
US691979324 août 199919 juil. 2005Intermec Ip Corp.Radio frequency identification system write broadcast capability
US702693513 avr. 200411 avr. 2006Impinj, Inc.Method and apparatus to configure an RFID system to be adaptable to a plurality of environmental conditions
US731552228 mars 20011 janv. 2008Micron Technology, Inc.Communication methods using slotted replies
US738547729 nov. 200510 juin 2008Keystone Technology Solutions, LlcRadio frequency data communications device
US76722608 nov. 20052 mars 2010Keystone Technology Solutions, LlcMethod of addressing messages and communications system
US2003023518420 juin 200225 déc. 2003Dorenbosch Jheroen P.Method and apparatus for speaker arbitration in a multi-participant communication session
US2005006006912 avr. 200417 mars 2005Breed David S.Method and system for controlling a vehicle
US200502073641 juin 200522 sept. 2005Wood Clifton W JrMethod of addressing messages and communications system
US2006002280029 juil. 20052 févr. 2006Reva Systems CorporationScheduling in an RFID system having a coordinated RFID tag reader array
US2006002280129 juil. 20052 févr. 2006Reva Systems CorporationRFID tag data acquisition system
US2006002281529 juil. 20052 févr. 2006Fischer Jeffrey HInterference monitoring in an RFID system
US200600563258 nov. 200516 mars 2006Wood Clifton W JrMethod of addressing messages and communications system
US200602097812 mai 200621 sept. 2006Micron Technology, Inc.Method of addressing messages and communications system
US2007013916428 nov. 200621 juin 2007O'toole James ERadio frequency data communications device
US200701767512 janv. 20072 août 2007Cesar Christian LMultiple Item Radio Frequency Tag Identification Protocol
US2008000741214 sept. 200710 janv. 2008Wood Clifton W JrMethod of Addressing Messages and Communications System
US2008004280614 sept. 200721 févr. 2008Wood Clifton W JrMethod of Addressing Messages and Communications System
US2008004883230 août 200728 févr. 2008O'toole James ESystems Utilizing an Interrogator and One or More RFID Tags
US2008004883529 août 200728 févr. 2008O'toole James ERadio Frequency Identification Apparatuses
US200801294851 déc. 20065 juin 2008Micron Technology, Inc.RFID communication systems and methods, and RFID readers and systems
US2008018022130 janv. 200731 juil. 2008Micron Technology, Inc.Systems and methods for RFID tag arbitration
US200903224919 sept. 200931 déc. 2009Keystone Technology Solutions, LlcMethod of Addressing Messages and Communications System
EP1072128B13 févr. 19997 mai 2008Micron Technology, Inc.Method and system of identifying wireless units
JP2002228809A Titre non disponible
WO2008094728A19 janv. 20087 août 2008Keystone Technology Solutions, Llc.Systems and methods for rfid tag arbitration
Citations hors brevets
Référence
1Auto-ID Center, Massachusetts Institute of Technology, "13.56 MHz ISM Band Class 1 Radio Frequency Identification Tag Interface Specification: Recommended Standard," Technical Report, Feb. 1, 2003.
2Capetanakis, John I., "Generalized TDMA: The Multi-Accessing Tree Protocol," IEEE Transactions on Information Theory, vol. Com. 27, No. 10, pp. 1476-1484, Oct. 1979.
3Capetanakis, John I., "Tree Algorithms for Packet Broadcast Channels", IEEE Transactions on Information Theory, vol. IT-25, No. 5, pp. 505-515, Sep. 1979.
4CNN Money, "Manhattan Associates Announces Next-Generation Microsoft-Based RFID Solutions," located at http:// money.cnn.com/services/tickerheadlines/prn/cItu045.PI.09162003122727.24911.htm, Sep. 16, 2003.
5Engels, Daniel, "The Use of the Electronic Product Code," Auto-ID Center, Massachusetts Institute of Technology, Technical Report, Feb. 1, 2003.
6EPC Global, Inc. "EPC Radio Frequency Identity Protocols- Class-1 Generation-2 UHF RFID- Protocol for Communications at 860 MHz-960MHz," version 1.0.9, cover sheet and pp. 37-38, Jan. 2005.
7EPC Global, Inc. "EPC Radio Frequency Identity Protocols— Class-1 Generation-2 UHF RFID— Protocol for Communications at 860 MHz-960MHz," version 1.0.9, cover sheet and pp. 37-38, Jan. 2005.
8eRetailNews, "The Electronic Product Code (EPC)," located at http://www.eretailnews.com/features/epc/htm, accessed Oct. 15, 2003.
9eRetailNews, "The Electronic Product Code (EPC)-A Technology Revolution?" located at http://www.eretailnews.com/features/0105epc1.htm, accessed Oct. 15, 2003.
10eRetailNews, "The Electronic Product Code (EPC)—A Technology Revolution?" located at http://www.eretailnews.com/features/0105epc1.htm, accessed Oct. 15, 2003.
11eRetailNews, "The Electronic Product Code Schematic," located at http://eee.eretailnews.com/features/0105epcschema.htm, accessed Oct. 15, 2003.
12Extended Search Report and Search Opinion for EP Patent Application No. 05016513.3, Jan. 22, 2007.
13Extended Search Report and Search Opinion for EP Patent Application No. 05016514.1, Jan. 26, 2007.
14Finkenzeller, Klaus, "Radio Frequency ldenitifcation-The Authors Homepage of the RFID Handbook," located at http://www.rfid-handbook.com, accessed Feb. 22, 2007.
15Finkenzeller, Klaus, "Radio Frequency ldenitifcation—The Authors Homepage of the RFID Handbook," located at http://www.rfid-handbook.com, accessed Feb. 22, 2007.
16High Tech Aid, "ISO/IEC 18000-RFID Air Interface Standards," located at http://www.hightechaid.com/standards/18000.htm, Feb. 1, 2003.
17High Tech Aid, "ISO/IEC 18000—RFID Air Interface Standards," located at http://www.hightechaid.com/standards/18000.htm, Feb. 1, 2003.
18Humblet, Pierre A. et al., "Efficient Accessing of a Multiaccess Channel," Proceedings of the 19th IEEE Conference on Decision and Control including the Symposium on Adaptive Processes, pp. 624-627, 1980.
19International Application No. PCT/US08/50630, International Search Report, Jun. 27, 2008.
20International Application No. PCT/US08/50630, Written Opinion, Jun. 27, 2008.
21International Application No. PCT/US99/02288, Written Opinion, Jan. 27, 2000.
22International Application No. PCT/US99102288, International Search Report, Aug. 3, 1999.
23ISO/IEC "Identification Cards-Contactless Integrated Circuit(s) Cards-Proximity Cards-Part 4: Transmission Protocol," ISO/IEC FDIS 14443-4:2000(E), Jul. 13, 2000.
24ISO/IEC "Identification Cards—Contactless Integrated Circuit(s) Cards—Proximity Cards—Part 4: Transmission Protocol," ISO/IEC FDIS 14443-4:2000(E), Jul. 13, 2000.
25ISO/IEC, "Automatic Identification-Radio Frequency Identification for Item Management-Communications and Interfaces-Part 3: Physical Layer, Anti Collision System and Protocol Values at 13.56 MHz Mode 4," ISO/IEC 18000-3-4, Mar. 1, 2001.
26ISO/IEC, "Automatic Identification—Radio Frequency Identification for Item Management—Communications and Interfaces—Part 3: Physical Layer, Anti Collision System and Protocol Values at 13.56 MHz Mode 4," ISO/IEC 18000-3-4, Mar. 1, 2001.
27ISO/IEC, "Automatic Identification-Radio Frequency Identification for Item Management-Communications and Interfaces-Part 3: Physical Layer, Anti-Collision System and Protocol Values at 13.56 MHz Mode 1," ISO/IEC 18000-3-1, Mar. 1, 2001.
28ISO/IEC, "Automatic Identification—Radio Frequency Identification for Item Management—Communications and Interfaces—Part 3: Physical Layer, Anti-Collision System and Protocol Values at 13.56 MHz Mode 1," ISO/IEC 18000-3-1, Mar. 1, 2001.
29ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Proximity Cards-Part 1: Physical Characteristics," ISO/IEC FCD 14443-1, 1997.
30ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Proximity Cards—Part 1: Physical Characteristics," ISO/IEC FCD 14443-1, 1997.
31ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Proximity Cards-Part 2: Radio Frequency Power and Signal Interface," ISO/IEC FCD 14443-2, Mar. 26, 1999.
32ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Proximity Cards—Part 2: Radio Frequency Power and Signal Interface," ISO/IEC FCD 14443-2, Mar. 26, 1999.
33ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Proximity Cards-Part 3: Initiation and Anticollision," ISO/IEC FDIS 14443-3:2000(E), Jul. 13, 2000.
34ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Proximity Cards—Part 3: Initiation and Anticollision," ISO/IEC FDIS 14443-3:2000(E), Jul. 13, 2000.
35ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Vicinity Cards-Part 1: Physical Characteristics," ISO/IEC FDIS 15693-1:2000(E), May 19, 2000.
36ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Vicinity Cards—Part 1: Physical Characteristics," ISO/IEC FDIS 15693-1:2000(E), May 19, 2000.
37ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Vicinity Cards-Part 2: Interface and Initialization," ISO/IEC FDIS 15693-2:2000(E), Feb. 3, 2000.
38ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Vicinity Cards—Part 2: Interface and Initialization," ISO/IEC FDIS 15693-2:2000(E), Feb. 3, 2000.
39ISO/IEC, "Identification Cards-Contactless Integrated Circuit(s) Cards-Vicinity Cards-Part 3: Anitcollision and Transmission Protocol," ISO/IEC CD 15693-3:1999(E), Nov. 17, 1999.
40ISO/IEC, "Identification Cards—Contactless Integrated Circuit(s) Cards—Vicinity Cards—Part 3: Anitcollision and Transmission Protocol," ISO/IEC CD 15693-3:1999(E), Nov. 17, 1999.
41ISO/IEC, "Information Technology AIDC Techniques-RFID for Item Management-Air Interface-Part 3: Paramenters for Air Interface Communications at 13.56 MHz," ISO/IEC 18000-3 FCD, May 27, 2002.
42ISO/IEC, "Information Technology AIDC Techniques—RFID for Item Management—Air Interface—Part 3: Paramenters for Air Interface Communications at 13.56 MHz," ISO/IEC 18000-3 FCD, May 27, 2002.
43Mullin, Eileen, "Electronic Product Code," Baseline Magazine, located at www.baselinemag.com/article2/0,3959,655991,00.asp, Sep. 5, 2002.
44RFID Journal, "Second Source of Class 1 EPC Chips," located at http://www.rfidjournal.com/article/articleview/473/1/1/, Jun. 26, 2003.
45Smart Active Labels Consortium, organization homepage located at http://www.sal-c.org, accessed Feb. 22, 2007.
46Symbol Technologies, Inc., "Understanding Gen 2: What It Is, How You Will Benefit and Criteria for Vendor Assessment," white paper, Jan. 2006.
47Transaction History of related Transaction History of related U.S. Appl. No. 10/652,573, filed Aug. 28, 2003, entitled "Method of Addressing Messages and Communications System."
48Transaction History of related U.S. Appl. No. 09/026,043, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,118,789.
49Transaction History of related U.S. Appl. No. 09/026,045, filed Feb. 19, 1998, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System," now U.S. Patent No. 6,072,801.
50Transaction History of related U.S. Appl. No. 09/026,050, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,061,344.
51Transaction History of related U.S. Appl. No. 09/026,248, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,275,476.
52Transaction History of related U.S. Appl. No. 09/551,304, filed Apr. 18, 2000, entitled "Method of Addressing Messages and Communications Systems," now U.S. Patent No. 6,282,186.
53Transaction History of related U.S. Appl. No. 09/556,235, filed Apr. 18, 2000, entitled "Method of Addressing Messages, and Establishing Communications Using a Tree Search Technique That Skips Levels," now U.S. Patent No. 6,226,300.
54Transaction History of related U.S. Appl. No. 09/617,390, filed Jul. 17, 2000, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,307,847.
55Transaction History of related U.S. Appl. No. 09/773,461, filed Jan. 31, 2001, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System," now U.S. Patent No. 6,307,848.
56Transaction History of related U.S. Appl. No. 09/820,467, filed Mar. 28, 2001, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 7,315,522.
57Transaction History of related U.S. Appl. No. 10/693,696, filed Oct. 23, 2003, entitled "Method and Apparatus to Select Radio Frequency Identification Devices in Accordance with an Arbitration Scheme."
58Transaction History of related U.S. Appl. No. 10/693,697, filed Oct. 23, 2003, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
59Transaction History of related U.S. Appl. No. 11/143,395, filed Jun. 1, 2005, entitled "Method of Addressing Messages and Communications System."
60Transaction History of related U.S. Appl. No. 11/270,204, filed Nov. 8, 2005, entitled "Method of Addressing Messages and Communications System."
61Transaction History of related U.S. Appl. No. 11/416,846, filed May 2, 2006, entitled "Method of Addressing Messages and Communications System."
62Transaction History of related U.S. Appl. No. 11/700,525, filed Jan. 30, 2007, entitled "Systems and Methods for RFID Tag Arbitration."
63Transaction History of related U.S. Appl. No. 11/755,073, filed May 30, 2007, entitled "Methods and Systems of Receiving Data Payload of RFID Tags."
64Transaction History of related U.S. Appl. No. 11/855,855, filed Sep. 14, 2007, entitled "Method of Addressing Messages and Communications System."
65Transaction History of related U.S. Appl. No. 11/855,860, filed Sep. 14, 2007, entitled "Method of Addressing Messages and Communications System."
66Transaction History of related U.S. Appl. No. 11/859,364, filed Sep. 21, 2007, entitled "Method of Addressing Messages and Communications System."
67Transaction History of related U.S. Appl. No. 11/862,121, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications System."
68Transaction History of related U.S. Appl. No. 11/862,124, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications."
69Transaction History of related U.S. Appl. No. 11/862,130, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications System."
70Transaction History of related U.S. Appl. No. 11/865,580, filed Oct. 1, 2007, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
71Transaction History of related U.S. Appl. No. 11/865,584, filed Oct. 1, 2007, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
72Tuttle, John R., U.S. Appl. No. 11/755,073 entitled "Methods and Systems of Receiving Data Payload of RFID Tags," filed May 30, 2007.
73USPTO Transaction History of U.S. Appl. No. 09/026,043, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,118,789.
74USPTO Transaction History of U.S. Appl. No. 09/026,045, filed Feb. 19, 1998, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System," now U.S. Patent No. 6,072,801.
75USPTO Transaction History of U.S. Appl. No. 09/026,050, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,061,344.
76USPTO Transaction History of U.S. Appl. No. 09/026,248, filed Feb. 19, 1998, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,275,476.
77USPTO Transaction History of U.S. Appl. No. 09/551,304, filed Apr. 18, 2000, entitled "Method of Addressing Messages and Communications Systems," now U.S. Patent 6,282,186.
78USPTO Transaction History of U.S. Appl. No. 09/556,235, filed Apr. 18, 2000, entitled "Method of Addressing Messages, and Establishing Communications Using a Tree Search Technique That Skips Levels," now U.S. Patent No. 6,226,300.
79USPTO Transaction History of U.S. Appl. No. 09/617,390, filed Jul. 17, 2000, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 6,307,847.
80USPTO Transaction History of U.S. Appl. No. 09/773,461, filed Jan. 31, 2001, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System," now U.S. Patent No. 6,307,848.
81USPTO Transaction History of U.S. Appl. No. 09/820,467, filed Mar. 28, 2001, entitled "Method of Addressing Messages and Communications System," now U.S. Patent No. 7,315,522.
82USPTO Transaction History of U.S. Appl. No. 10/652,573, filed Aug. 28, 2003, entitled "Method of Addressing Messages and Communications System."
83USPTO Transaction History of U.S. Appl. No. 10/693,696, filed Oct. 23,2003, entitled "Method and Apparatus to Select Radio Frequency Identification Devices in Accordance with an Arbitration Scheme."
84USPTO Transaction History of U.S. Appl. No. 10/693,697, filed Oct. 23, 2003, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
85USPTO Transaction History of U.S. Appl. No. 11/143,395, filed Jun. 1, 2005, entitled "Method of Addressing Messages and Communications System."
86USPTO Transaction History of U.S. Appl. No. 11/270,204, filed Nov. 8, 2005, entitled "Method of Addressing Messages and Communications System."
87USPTO Transaction History of U.S. Appl. No. 11/416,846, filed May 2, 2006, entitled "Method of Addressing Messages and Communications System."
88USPTO Transaction History of U.S. Appl. No. 11/855,855, filed Sep. 14, 2007, entitled "Method of Addressing Messages and Communications System."
89USPTO Transaction History of U.S. Appl. No. 11/855,860, filed Sep. 14, 2007, entitled "Method of Addressing Messages and Communications System."
90USPTO Transaction History of U.S. Appl. No. 11/859,364, filed Sep. 21, 2007, entitled "Method of Addressing Messages and Communications System."
91USPTO Transaction History of U.S. Appl. No. 11/862,121, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications System."
92USPTO Transaction History of U.S. Appl. No. 11/862,124, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications."
93USPTO Transaction History of U.S. Appl. No. 11/862,130, filed Sep. 26, 2007, entitled "Method of Addressing Messages and Communications System."
94USPTO Transaction History of U.S. Appl. No. 11/865,580, filed Oct. 1, 2007, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
95USPTO Transaction History of U.S. Appl. No. 11/865,584, filed Oct. 1, 2007, entitled "Method of Addressing Messages, Methods of Establishing Wireless Communications, and Communications System."
96Wolf, Jack Keil, "Principles of Group Testing and an Application to the Design and Analysis of Multi-Access Protocols," NATO ASI Series E, Applied Sciences, No. 91, pp. 237-257, 1985.
97Wood, Jr., Clifton W., U.S. Appl. No. 10/652,573, filed Aug. 28, 2008.
98Wood, Jr., Clifton W., U.S. Appl. No. 10/693,696, filed Oct. 23, 2003.
99Wood, Jr., Clifton W., U.S. Appl. No. 10/693,697, filed Oct. 23, 2003.
100Wood, Jr., Clifton W., U.S. Appl. No. 11/859,364, filed Sep. 21, 2007.
101Wood, Jr., Clifton W., U.S. Appl. No. 11/862,121, filed Sep. 26, 2007.
102Wood, Jr., Clifton W., U.S. Appl. No. 11/862,124, filed Sep. 26, 2007.
103Wood, Jr., Clifton W., U.S. Appl. No. 11/862,130, filed Sep. 21, 2007.
104Wood, Jr., Clifton W., U.S. Appl. No. 11/865,580, filed Oct. 1, 2007.
105Wood, Jr., Clifton W., U.S. Appl. No. 11/865,584, filed Oct. 1, 2007.
106Wood, Jr., Clifton W., U.S. Appl. No. 12/493,542, filed Jun. 29, 2009.
107Wood, Jr., Clifton W., U.S. Appl. No. 12/541,882, filed Aug. 14, 2009.
108Wright, Jim, "Trends and Innovations in RF Indentification," Sun Microsystems Inc. presentation, Mar. 2005.
109Zebra Technologies Corporation, "Electronic Product Code (EPC)," located at http://www.rfid.zebra.com/epc/htm, accessed Oct. 15 2003.
Référencé par
Brevet citant Date de dépôt Date de publication Déposant Titre
US864522217 juin 20114 févr. 2014Jpmorgan Chase Bank, N.A.System and methods for mobile ordering and payment
US901407727 janv. 201421 avr. 2015Round Rock Research, LlcMethods and apparatus for conducting financial transactions
US923025910 mai 20105 janv. 2016Jpmorgan Chase Bank, N.A.Systems and methods for mobile ordering and payment
Classifications
Classification aux États-Unis370/329, 370/346, 370/347
Classification internationaleH04W4/00, H04L12/44, G06T5/20, G06T1/60, G06F13/40
Classification coopérativeG06F13/4027, H04L12/44, G06T5/20, H04W4/00, G06T1/60
Classification européenneH04L12/44, H04W4/00, G06T1/60, G06F13/40D5, G06T5/20
Événements juridiques
DateCodeÉvénementDescription
4 janv. 2010ASAssignment
Owner name: ROUND ROCK RESEARCH, LLC, NEW YORK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MICRON TECHNOLOGY, INC.;REEL/FRAME:023786/0416
Effective date: 20091223
26 janv. 2010ASAssignment
Owner name: MICRON TECHNOLOGY, INC., IDAHO
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KEYSTONE TECHNOLOGY SOLUTIONS, LLC;REEL/FRAME:023839/0881
Effective date: 20091222