Method of addressing messages, method of establishing wireless communications and communications system

• US RE44,411 E1
• Filed: 12/17/2009
• Issued: 08/06/2013
• Est. Priority Date: 02/19/1998
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Round Rock Research LLC
• Inventors: Wood, Clifton W. Jr., Hush, Don
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US12/641,249
• Time in Patent Office: 1,328 Days
• Field of Search: 370/329, 370/437, 370/462
• US Class Current: 370/329
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10049 binary tree
• CPC Class Codes: H04L 12/44 Star or tree networks
• CPC Class Codes: H04W 4/06 Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 8/005 Discovery of network devices, e.g. terminals
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support

Abstract

A method of and apparatus for establishing wireless communications between an interrogator and individual ones of multiple wireless identification devices, the method comprising utilizing a tree search method to establish communications without collision between the interrogator and individual ones of the multiple wireless identification devices, a search tree being defined for the tree search method, the tree having multiple levels representing subgroups of the multiple wireless identification devices, the number of devices in a subgroup in one level being half of the number of devices in the next higher level, the tree search method employing level skipping wherein at least one level of the tree is skipped. 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 levels of the tree are occasionally skipped. In one aspect, the method comprises transmitting a first command to select a group of RFID devices based at least in part on a first memory range beginning at a first bit location. The method further comprises transmitting a second command, successively following the first command, to select a subgroup of the group of RFID devices based at least in part on a second memory range beginning at a second bit location. The second bit location is shifted by two or more bits from the first bit location and receives a reply from at least one RFID device of the subgroup of RFID devices. The reply includes an identifier to uniquely identify the RFID device.

Claims

1. A method of establishing wireless communications between an interrogator and wireless identification devices, the method comprising utilizing a tree search technique to establish communications without collision between the interrogator and individual ones of the multiple wireless identification devices, the method including using a binary search tree having multiple levels representing subgroups of the multiple wireless identification devices, the number of devices in a subgroup in one level being less than the number of devices in the next level, the tree search technique employing level skipping wherein every second level of the tree is skipped.

2. 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.

3. A method in accordance with claim 1 wherein when a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, the device that is not within communications range of the interrogator does not respond to the command.

4. A method in accordance with claim 1 wherein when a subgroup contains both a device that is within communications range of the interrogator, and a device that is not within communications range of the interrogator, the device that is within communications range of the interrogator responds to the command.

5. A method in accordance with claim 1 wherein a device in a subgroup changes between being within communications range of the interrogator and not being within communications range, over time.

6. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices, the method comprising:

establishing for respective devices unique identification numbers;

causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;

transmitting a communication, from the interrogator, requesting devices having random values within a specified group of random values to respond;

receiving the communication at multiple devices, devices receiving the communication respectively determining if the random value chosen by the device falls within the 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, using a search tree, that is one quarter of the first mentioned specified group, wherein at least one level of a search tree is skipped.

7. A method of addressing messages from an interrogator to a selected one or more of a number of communications devices in accordance with claim 6 wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply.

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 6 wherein sending a reply to the interrogator comprises transmitting the random value 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 6 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.

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 6 wherein, after receiving a reply without collision from a device, the interrogator sends a command individually addressed to that device.

11. A method of addressing messages from a transponder to a selected one or more of a number of communications devices, the method comprising:

causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;

transmitting a communication, from the transponder, requesting devices having random values within a specified group of a plurality of possible groups of random values to respond, the 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 having a plurality of levels, wherein groups of random values decrease in size with each level descended;

devices receiving the communication respectively determining if the random value chosen by the device falls within the specified group and, if so, sending a reply to the transponder; and

, if not, not sending a reply; and

determining using the transponder if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group by descending at least two levels in the tree.

12. A method of addressing messages from a transponder to a selected one or more of a number of communications devices in accordance with claim 11 and further comprising establishing unique identification numbers for respective devices.

13. A method of addressing messages from a transponder to a selected one or more of a number of communications devices in accordance with claim 12 and further including establishing a predetermined number of bits to be used for the random values.

14. A method of addressing messages from a transponder 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 sixteen bits.

15. A method of addressing messages from a transponder to a selected one or more of a number of communications devices in accordance with claim 13 wherein devices sending a reply to the transponder 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 unique identification numbers;

causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;

transmitting from the interrogator 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 or equal to the entire set of random values, the plurality of possible groups being organized in a binary tree having a plurality of levels, wherein groups of random values decrease in size with each level;

receiving the command at multiple of the devices, the 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;

determining using the interrogator if a collision occurred between devices that sent a reply and, if so, creating a new, smaller, specified group using a level of the tree different from the level used in the interrogator transmitting, wherein at least one level of the tree is skipped, 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 wherein every second level is skipped.

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 the unique identification numbers are respectively defined by a predetermined number of bits.

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 the unique identification numbers are respectively defined by a predetermined number of bits and wherein the random values are respectively defined by a predetermined number of bits.

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 and further comprising, after the interrogator transmits a command requesting devices having random values within the new specified group of random values to respond:

devices receiving the command respectively determining if their chosen random values fall within the new smaller specified group and, if so, sending a reply to the interrogator.

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 20 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.

22. A system comprising:

an interrogator;

a number of communications devices capable of wireless communications with the interrogator;

means for establishing for respective devices unique identification numbers respectively having the first predetermined number of bits;

means for causing the devices to select random values, wherein respective devices choose random values independently of random values selected by the other devices;

means for causing the interrogator to transmit a command requesting devices having random values within a specified group of random values to respond;

means for causing devices receiving the command to determine if their chosen random values fall within the specified group and, if so, to send a reply to the interrogator; and

means for causing the interrogator to determine if a collision occurred between devices that sent a reply and, if so, to create a new, smaller, specified group that is one quarter of the first mentioned specified group, wherein at least one level of the tree is skipped.

23. A system in accordance with claim 22 wherein sending a reply to the interrogator comprises transmitting the unique identification number of the device sending the reply.

24. A system in accordance with claim 22 wherein sending a reply to the interrogator comprises transmitting the random value of the device sending the reply.

25. A system in accordance with claim 22 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.

26. A system in accordance with claim 22 wherein the interrogator further includes means for, after receiving a reply without collision from a device, sending a command individually addressed to that device.

33. The interrogator of claim 22, wherein the reply further includes an identification number that identifies a person with whom the RFID device is associated.

27. An interrogator that, when operated, performs a method comprising:

transmitting a first command to select a group of RFID devices based, at least in part, on a first memory range beginning at a first bit location;

transmitting a second command, successively following the first command, to select a subgroup of the group of RFID devices based, at least in part, on a second memory range beginning at a second bit location, wherein the second bit location is shifted by two or more bits from the first bit location; and

receiving a reply from at least one RFID device of the subgroup of RFID devices, the reply including an identifier to uniquely identify the RFID device.

28. The interrogator of claim 27, wherein the method further comprises transmitting a third command after transmitting the second command and before receiving the reply, the third command including a at least one field configured to select at least a portion of the subgroup of RFID devices to reply to the third command.

29. The interrogator of claim 28, wherein the method further comprises transmitting a signal, the signal associated with a slotted arbitration scheme.

30. The interrogator of claim 27, wherein the reply further includes an identification number that identifies a person with whom the RFID device is associated.

31. The interrogator of claim 27, wherein the method further comprises transmitting a command that causes the subgroup of RFID devices to independently generate random numbers as identifiers.

32. The interrogator of claim 27, wherein the method further comprises transmitting a signal after transmitting the second command and before receiving the reply, the signal indicating a number of slots in accordance with a slotted arbitration scheme.

34. A method, comprising:

providing an RFID device storing an identification number to identify a person;

sending a first command from an interrogator, the first command configured to select a group of RFID devices based, at least in part, on a respective first value stored in each respective RFID device of the group of RFID devices, the respective first value bounded at a respective first bit location within a memory of the respective RFID device;

sending a second command from the interrogator after sending the first command and before sending any intervening command from the interrogator, the second command configured to select a subgroup of the group of RFID devices based, at least in part, on a respective second value stored in the respective RFID device of the group of RFID devices, the respective second value bounded at a respective second bit location within the memory of the respective RFID device, wherein the second bit location is at least two bits away from the first bit location; and

receiving a unique identifier of the RFID device from the RFID device, the RFID device belonging to the subgroup, the unique identifier being separate from the identification number.

35. The method of claim 34, wherein the respective first value of the RFID device comprises at least a portion of the unique identifier.

36. The method of claim 34, further comprising receiving the identification number from the RFID device.

37. The method of claim 36, further comprising sending the unique identifier to the device.

38. The method of claim 37, further comprising sending a third command to the RFID device, the third command associated with a slot value.

39. The method of claim 34, further comprising sending a third signal from the interrogator, the third signal being associated with a slotted random anticollision algorithm and indicating a number of slots for the RFID device.

40. The method of claim 39, further comprising receiving the identification number from the RFID device.

41. A system comprising:

an RFID reader configured to send a first command to indicate a first bit string and a first range of bits, followed, without any intervening query commands, by a second command to indicate a second bit string and a second range of bits, wherein the first range of bits differs from the second range of bits by at least two bits;

an RFID device storing an identification code, the RFID device configured to compare the first bit string to a first value stored in memory corresponding to the first range of bits, to compare the second bit string to a second value stored in memory corresponding to the second range of bits, to provide an identifier to uniquely identify the RFID device, and to provide the identification code.

42. The system of claim 41, wherein the reader is further configured to send the identifier to the RFID device.

43. The system of claim 42, wherein the RFID device is further configured to pick a random slot value.

44. The system of claim 43, wherein the reader is further configured to send a third command to instruct the RFID device to generate the identifier.