Methods and apparatuses to identify devices

• US 20030019929A1
• Filed: 05/30/2002
• Published: 01/30/2003
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: RUIZHANG TECHNOLOGY LIMITED COMPANY
• Original Assignee: Alien Technology Corporation
• Inventors: Stewart, Roger G., Smith, John Stephen
• Granted Patent: US 6,988,667 B2
• Time in Patent Office: Days
• US Class Current: 235/385
• 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 7/08 by means detecting the change of an electrostatic or magnetic field, e.g. by detecting change of capacitance between electrodes
• CPC Class Codes: G06K 7/10049 binary tree

Abstract

Methods and apparatuses for identifying devices, such as RF tags, are described.

In one exemplary method of an embodiment of the invention, a reader identifies tags without requiring or determining whether a response to an interrogation was a single response from a single tag or multiple responses from multiple tags.

In another exemplary method of an embodiment, a method is performed by a tag in an identification system, and the method includes receiving a first data from a reader, and correlating the first data with a first corresponding portion of the tag'"'"'s identification code, and specifying a match if the first data matches the first corresponding portion, and receiving second data which, combined with the first data, is correlated with a second corresponding portion of the tag'"'"'s identification code.

Claims

1. A method performed by a reader for identifying tags, each having an identifier code, said method comprising:

transmitting data to a plurality of tags, said data specifying at least one identifier code; and

receiving at least one response indicating a match from said plurality of tags, wherein said reader does not attempt to distinguish between a single response indicating a match and a plurality of responses each indicating a match.

2. A method performed by a tag, said method comprising:

receiving a first data from a reader;

correlating said first data with a first corresponding portion of an identification code of a tag;

transmitting a response to said reader if said first data matches said first corresponding portion; and

receiving a second data which is correlated with a second corresponding portion of said identification code.

3. A method as in claim 2 wherein said second data is received after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

4. A method as in claim 3 further comprising:

receiving a test code from said reader prior to receiving said first data; and

activating said tag only if said test code is correctly processed by said tag prior to receiving said first data.

5. A method as in claim 2 wherein said first data comprises a first command and said second data comprises said first command or a second command.

6. A method as in claim 5 wherein said first command and said second command specify one of a position of a bit pointer or a value of a bit pointed to by said bit pointer.

7. A method performed by a reader to identify a tag having an identification code, said method comprising:

transmitting a first data from said reader, for receipt by said tag, said first data corresponding to a first portion of said identification code;

receiving a response from said tag if said first data matches said first portion; and

transmitting a second data which corresponds to a second portion of said identification code.

8. A method as in claim 7 wherein said second data is transmitted after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

9. A method performed by a reader for identifying a tag, said method comprising:

transmitting a first data from said reader, said first data specifying a first search at a first level of a number space;

receiving a response from at least one tag;

transmitting a second data from said reader, said second data specifying a second search at a second level of said number space, wherein said second level corresponds to a second portion of said number space and said first level corresponds to a first portion of said number space and said second portion is smaller than said first portion; and

storing a data structure which comprises said first portion and said second portion and which specifies tags which are identified and portions of said number space in which there are no tags.

10. A method as in claim 9 wherein said number space is a binary number space and said data structure is a binary tree which is assembled as said reader receives responses from tags.

11. A method as in claim 9 wherein said reader transmits said second data without regard to whether said receiving received a single response from one tag or a plurality of responses from a plurality of tags.

12. A method performed by a tag in order to identify the tag which has an identifier code, said method comprising:

receiving data from a reader; and

transmitting a single bit response to said reader in response to said data, wherein said data specifies at least a range of possible identifier codes.

13. A method performed by a reader in order to identify at least one tag which has an identifier code, said method comprising:

transmitting data from said reader; and

receiving, at said reader, a single bit response from at least one tag, said single bit response being in response to said data from said reader, wherein said data specifies at least a range of possible identifier codes.

14. A method as in claim 13 further comprising:

transmitting another data from said reader without regard to whether said receiving received a single response from one tag or a plurality of responses from a plurality of tags.

15. A method as in claim 13 wherein said reader does not attempt to distinguish between a single response from only one tag indicating a match and a plurality of responses from tags each indicating a match.

16. A method performed by a tag having an identifier code, said method comprising:

receiving, at said tag, data representing at least a portion of a test code from a reader;

processing said data in said tag and determining whether said test code has been properly received; and

silencing transmissions from said tag if said test code has not been properly received.

17. A method performed by a reader for identifying a tag having an identification code, said method comprising:

transmitting commands from a reader to any tags present, said commands causing a search of possible identification codes in a number space; and

transmitting a further command which requests tags in a portion of said number space to indicate whether said tags, if any, have a partial match to at least a part of an identification code, wherein if there are tags which are not yet identified in said portion, said reader transmits commands to search said portion before searching a larger portion of said number space.

18. A method as in claim 17 wherein said search of said portion is a neighborhood search performed after identifying and muting a first tag which is also in said portion.

19. A method performed by a reader for identifying at least one tag having an identification code, said method comprising:

transmitting at least one command from a reader to any tags present, said command causing a search of possible identification codes;

transmitting a portion of an identification code; and

receiving, in response to said transmitting said portion of said identification code, a response, from a tag, which indicates a match to said portion and which indicates at least one next bit in said tag'"'"'s identification code.

20. A method as in claim 19 wherein said possible identification codes exist in a number space and wherein said reader determines a portion of said number space for further searching after receiving said at least one next bit in said response.

21. A method as in claim 19 further comprising:

determining a relative strength of responses from tags indicating their corresponding at least one next bit.

22. A method as in claim 21 wherein if said relative strength of a first next bit response exceeds a second next bit response, then said reader continues a search with said portion of said identification code and said first next bit response.

23. A method as in claim 22 wherein said first next bit response is a “

1” and

said second next bit response is “

0.”

24. A method performed by a tag having an identification code, said method comprising:

receiving a portion of an identification code; and

transmitting from a tag, in response to said receiving said portion of said identification code, a response which indicates a match to said portion, if there is a match, and which indicates at least one next bit in said tag'"'"'s identification code.

25. A method as in claim 24 wherein if there is no match to said portion, said tag does not transmit a response.

26. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying tags, each having an identifier code, said method comprising:

transmitting data to a plurality of tags, said data specifying at least one identifier code; and

receiving at least one response indicating a match from said plurality of tags, wherein said reader does not attempt to distinguish between a single response indicating a match and a plurality of responses each indicating a match.

27. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method comprising:

receiving a first data from a reader;

correlating said first data with a first corresponding portion of an identification code of a tag;

transmitting a response to said reader if said first data matches said first corresponding portion; and

receiving a second data which is correlated with a second corresponding portion of said identification code.

28. A computer readable medium as set forth in claim 27, wherein said second data is received after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

29. A computer readable medium as set forth in claim 28, wherein the method further comprises:

receiving a test code from said reader prior to receiving said first data; and

activating said tag only if said test code is correctly processed by said tag prior to receiving said first data.

30. A computer readable medium as set forth in claim 27, wherein said first data comprises a first command and said second data comprises said first command or a second command.

31. A computer readable medium as set forth in claim 30, wherein said first command and said second command specify one of a position of a bit pointer or a value of a bit pointed to by said bit pointer.

32. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method to identify a tag having an identification code, said method comprising:

transmitting a first data from said reader, for receipt by said tag, said first data corresponding to a first portion of said identification code;

receiving a response from said tag if said first data matches said first portion; and

transmitting a second data which corresponds to a second portion of said identification code.

33. A computer readable medium as set forth in claim 32, wherein said second data is transmitted after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

34. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying a tag, said method comprising:

transmitting a first data from said reader, said first data specifying a first search at a first level of a number space;

receiving a response from at least one tag;

transmitting a second data from said reader, said second data specifying a second search at a second level of said number space, wherein said second level corresponds to a second portion of said number space and said first level corresponds to a first portion of said number space and said second portion is smaller than said first portion; and

storing a data structure which comprises said first portion and said second portion and which specifies tags which are identified and portions of said number space in which there are no tags.

35. A computer readable medium as set forth in claim 34, wherein said number space is a binary number space and said data structure is a binary tree which is assembled as said reader receives responses from tags.

36. A computer readable medium as set forth in claim 34, wherein said reader transmits said second data without regard to whether said receiving received a single response from one tag or a plurality of responses from a plurality of tags.

37. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for a tag in order to identify the tag which has an identifier code, said method comprising:

receiving data from a reader; and

transmitting a single bit response to said reader in response to said data, wherein said data specifies at least a range of possible identifier codes.

38. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for a reader in order to identify at least one tag which has an identifier code, said method comprising:

transmitting data from said reader; and

receiving, at said reader, a single bit response from at least one tag, said single bit response being in response to said data from said reader, wherein said data specifies at least a range of possible identifier codes.

39. A computer readable medium as set forth in claim 38 further comprising:

transmitting another data from said reader without regard to whether said receiving received a single response from one tag or a plurality of responses from a plurality of tags.

40. A computer readable medium as set forth in claim 38 wherein said reader does not attempt to distinguish between a single response from only one tag indicating a match and a plurality of responses from tags each indicating a match.

41. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for a tag having an identifier code, said method comprising:

receiving, at said tag, data representing at least a portion of a test code from a reader;

processing said data in said tag and determining whether said test code has been properly received; and

silencing transmissions from said tag if said test code has not been properly received.

42. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying a tag having an identification code, said method comprising:

transmitting commands from a reader to any tags present, said commands causing a search of possible identification codes in a number space; and

transmitting a further command which requests tags in a portion of said number space to indicate whether said tags, if any, have a partial match to at least a part of an identification code, wherein if there are tags which are not yet identified in said portion, said reader transmits commands to search said portion before searching a larger portion of said number space.

43. A computer readable medium as set forth in claim 42 wherein said search of said portion is a neighborhood search performed after identifying and muting a first tag which is also in said portion.

44. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for identifying at least one tag having an identification code, said method comprising:

transmitting at least one command from a reader to any tags present, said command causing a search of possible identification codes;

transmitting a portion of an identification code; and

receiving, in response to said transmitting said portion of said identification code, a response, from a tag, which indicates a match to said portion and which indicates at least one next bit in said tag'"'"'s identification code.

45. A computer readable medium as set forth in claim 44 wherein said possible identification codes exist in a number space and wherein said reader determines a portion of said number space for further searching after receiving said at least one next bit in said response.

46. A computer readable medium as set forth in claim 44 further comprising:

determining a relative strength of responses from tags indicating their corresponding at least one next bit.

47. A computer readable medium as set forth in claim 46 wherein if said relative strength of a first next bit response exceeds a second next bit response, then said reader continues a search with said portion of said identification code and said first next bit response.

48. A computer readable medium as set forth in claim 47 wherein said first next bit response is a “

1” and

said second next bit response is “

0.”

49. A computer readable medium containing executable computer program instructions, which when executed by a data processing system, cause the data processing system to perform a method for a tag having an identification code, said method comprising:

receiving a portion of an identification code; and

transmitting from a tag, in response to said receiving said portion of said identification code, a response which indicates a match to said portion, if there is a match, and which indicates at least one next bit in said tag'"'"'s identification code.

50. A computer readable medium as set forth in claim 49 wherein if there is no match to said portion, said tag does not transmit a response.

51. A tag comprising:

a receiver to receive a first data from a reader;

a processor coupled with said receiver, said processor is to correlate said first data with a first corresponding portion of an identification code of said tag; and

a transmitter coupled with said processor, said transmitter is to transmit a response to said reader if said first data matches said first corresponding portion of said identification code, wherein said receiver is to receive a second data which is to be correlated with a second corresponding portion of said identification code.

52. A tag as in claim 51 further comprising:

an antenna, wherein said antenna is to receive a signal from said reader, said signal to include said first data from said reader;

a receive/transmit switch coupled to said antenna and said receiver, wherein said receive/transmit switch is to allow said first data to be received by said receiver and said receive/transmit switch coupled to said transmitter, wherein said receive/transmit switch is to allow said response to be transmitted from said antenna.

53. A tag as in claim 51 wherein said processor is a correlator.

54. A tag as in claim 51 wherein said second data is to be received after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

55. A tag as in claim 54 wherein said receiver is to receive a test code from said reader prior to said first data and said response is to be transmitted only if said test code is correctly processed by said tag prior to receiving said first data.

56. A tag as in claim 55 wherein said first data comprises a first command and said second data comprises said first command or a second command.

57. A tag as in claim 56 wherein said first command and said second command specify one of a position of a bit pointer or a value of a bit pointed to by said bit pointer.

58. A tag as in claim 56 further comprising inter-command memory to store at least one of said first command and a result of said first command.

59. A tag comprising:

a receiver to receive data from a reader;

a processor coupled with said receiver, said processor is to process said data; and

a transmitter coupled with said processor, said transmitter is to transmit a single bit response to said reader in response to said data, wherein said data specifies at least a range of possible identifier codes.

60. A tag comprising:

a receiver to receive, at said tag, data representing at least a portion of a test code from a reader;

a processor coupled with said receiver, said processor is to process said data in said tag and is to determine whether said test code has been properly received; and

a transmitter coupled with said processor, said transmitter is to transmit a transmission from said tag, wherein said transmission from said tag is to be silenced if said test code has not been properly received.

61. A tag having an identification code, said tag comprising:

a receiver to receive a portion of an identification code;

a processor coupled with said receiver; and

a transmitter coupled with said processor, said transmitter is to transmit a response from said processor which indicates a match to said portion, if there is a match, and which indicates at least one next bit in said tag'"'"'s identification code, said response is to be in response to receipt of said portion of said identification code.

62. A tag as in claim 61 wherein if there is no match to said portion, said tag does not transmit a response.

63. An apparatus to identify tags, said apparatus comprising:

a microprocessor to control data;

a transmitter coupled with said microprocessor, said transmitter is to transmit said data to a plurality of tags, said data specifying at least one identifier code; and

a receiver coupled with said microprocessor, said receiver is to receive at least one response from a plurality of tags, wherein said apparatus does not attempt to distinguish between a single response indicating a match and a plurality of responses each indicating a match.

64. An apparatus as in claim 63 further comprising:

a data bus coupled with said microprocessor.

65. An apparatus as in claim 64 further comprising:

a network interface coupled with at least one of said data bus and said microprocessor, said network interface is to allow communication with a network.

66. An apparatus to identify a tag having an identification code, said apparatus comprising:

a microprocessor to control a first data;

a transmitter coupled with said microprocessor, said transmitter is to transmit said first data, said first data is to be received by said tag, said first data corresponding to a first portion of said identification code; and

a receiver coupled with said microprocessor, said receiver is to receive a response from said tag if said first data matches said first portion of said identification code, wherein said transmitter is to transmit a second data, which corresponds to a second portion of said identification code.

67. An apparatus as in claim 66 wherein said second data is to be transmitted after multiple responses are received from tags indicating a match to said first data and wherein said second data may include said first data.

68. An apparatus to identify a tag, said apparatus comprising:

a microprocessor having a memory, said microprocessor is to control a search for tags;

a transmitter coupled with said microprocessor, said transmitter is to transmit said first data, said first data specifying a first search at a first level of a number space; and

a receiver coupled with said microprocessor, said receiver is to receive a response from at least one tag, wherein said transmitter is to transmit a second data, said second data specifying a second search at a second level of said number space, wherein said second level corresponds to a second portion of said number space and said first level corresponds to a first portion of said number space and said second portion is smaller than said first portion and wherein a data structure is stored in said memory, said data structure comprises said first portion and said second portion and which specifies tags which are identified and portions of said number space in which there are no tags.

69. An apparatus as in claim 68 wherein said number space is a binary number space and said data structure is a binary tree, which is assembled as responses are received from tags.

70. An apparatus as in claim 68 wherein said apparatus is to transmit a second data without regard to whether said receiver received a single response from one tag or a plurality of responses from a plurality of tags.

71. An apparatus to identify at least one tag, which has an identifier code, said apparatus comprising:

a microprocessor to control data;

a transmitter coupled with said microprocessor, said transmitter is to transmit said data; and

a receiver coupled with said microprocessor, said receiver is to receive a single bit response from at least one tag, said single bit response being in response to said data, wherein said data specifies at least a range of possible identifier codes.

72. An apparatus as in claim 71 wherein said apparatus is to transmit another data without regard to whether said receiver received a single response from one tag or a plurality of responses from a plurality of tags.

73. An apparatus as in claim 71 wherein said apparatus does not attempt to distinguish between a single response from only one tag indicating a match and a plurality of responses from tags each indicating a match.

74. An apparatus to identify a tag having an identification code, said apparatus comprising:

a microprocessor to send commands; and

a transmitter coupled with said microprocessor, said transmitter is to transmit said commands to any tags present, said commands causing a search of possible identification codes in a number space and said transmitter is to transmit a further command which requests tags in a portion of said number space to indicate whether said tags, if any, have a partial match to at least a part of an identification code, wherein if there are tags which are not yet identified in said portion, said apparatus is to transmit commands to search said portion before searching a larger portion of said number space.

75. An apparatus as in claim 74 wherein said search of said portion is a neighborhood search performed after identifying and muting a first tag which is also in said portion.

76. An apparatus to identify at least one tag having an identification code, said apparatus comprising:

a microprocessor to send at least one command;

a transmitter coupled with said microprocessor, said transmitter is to transmit said at least one command from said apparatus to any tags present, said command causing a search of possible identification codes and said transmitter is to transmit a portion of an identification code; and

a receiver coupled with said microprocessor, said receiver is to receive in response to transmitting a portion of said identification code, a response, from a tag, which indicates a match to said portion and which indicates at least one next bit in said tag'"'"'s identification code.

77. An apparatus as in claim 76 wherein said possible identification codes exist in a number space and wherein said microprocessor is to determine a portion of said number space for further searching after receiving said at least one next bit in said response.

78. An apparatus as in claim 76 wherein said microprocessor is to determine a relative strength of responses from tags indicating their corresponding at least one next bit.

79. An apparatus as in claim 78 wherein if said relative strength of a first next bit response exceeds a second next bit response, then said microprocessor continues a search with said portion of said identification code and said first next bit response.

80. An apparatus as in claim 79 wherein said first next bit response is a “

1” and

said second next bit response is “

0.”

81. A tag comprising:

means for receiving a first data from a reader;

means for correlating said first data with a first corresponding portion of an identification code of a tag; and

means for transmitting a response to said reader if said first data matches said first corresponding portion of said identification code, wherein said receiver is to receive a second data which is correlated with a second corresponding portion of said identification code.

82. A tag as in claim 81 further comprising:

antenna means, wherein said antenna means is to receive a signal from said reader, said signal to include said first data from said reader; and

switch means to allow said first data to be received by said means for receiving, and wherein said switch means to allow said response to be transmitted from said antenna means.

83. A tag as in claim 81 wherein said second data is received after said reader receives multiple responses from tags indicating a match to said first data and wherein said second data may include said first data.

84. A tag as in claim 83 wherein said means for receiving is to receive a test code from said reader prior to said first data and said response is to be transmitted only if said test code is correctly processed by said tag prior to receiving said first data.

85. A tag as in claim 84 wherein said first data comprises a first command and said second data comprises said first command or a second command.

86. A tag as in claim 85 wherein said first command and said second command specify one of a position of a bit pointer or a value of a bit pointed to by said bit pointer.

87. A tag as in claims 85, further comprising means for storing at least one of said first command and a result of said first command.

88. A tag comprising:

means for receiving data from a reader;

means for processing said data; and

means for transmitting a single bit response to said reader in response to said data, wherein said data specifies at least a range of possible identifier codes.

89. A tag comprising:

means for receiving, at said tag, data representing at least a portion of a test code from a reader;

means for processing said data in said tag and to determine whether said test code has been properly received; and

means for transmitting a transmission from said tag, wherein said transmission from said tag is to be silenced if said test code has not been properly received.

90. A tag having an identification code, said tag comprising:

means for receiving, said means for receiving is to receive a portion of an identification code;

means for determining to process said portion of said identification code; and

means for transmitting, said means for transmitting is to transmit a response from said means for determining which indicates a match to said portion, if there is a match, and which indicates at least one next bit in said tag'"'"'s identification code, said response is to be in response to receipt of said portion of said identification code.

91. An apparatus as in claim 90 wherein if there is no match to said portion, said means for transmitting does not transmit a response.

93. An apparatus as in claim 91 further comprising:

means for interfacing said data with a network.

92. An apparatus to identify tags, said apparatus comprising:

means for controlling data;

means for transmitting said data to a plurality of tags, said data specifying at least one identifier code; and

means for receiving at least one response from a plurality of tags, wherein said apparatus does not attempt to distinguish between a single response indicating a match and a plurality of responses each indicating a match.

94. An apparatus to identify a tag having an identification code, said apparatus comprising:

means for controlling a first data;

means for transmitting said first data, said first data is to be received by said tag, said first data corresponding to a first portion of said identification code; and

means for receiving a response from said tag if said first data matches said first portion of said identification code, wherein said means for transmitting is to transmit a second data, which corresponds to a second portion of said identification code.

95. An apparatus as in claim 94 wherein said second data is to be transmitted after multiple responses are received from tags indicating a match to said first data and wherein said second data may include said first data.

96. An apparatus to identify a tag, said apparatus comprising:

means for controlling a first data;

means for storing data;

means for transmitting said first data, said first data specifying a first search at a first level of a number space; and

means for receiving a response from at least one tag, wherein said means for transmitting is to transmit a second data, said second data specifying a second search at a second level of said number space, wherein said second level corresponds to a second portion of said number space and said first level corresponds to a first portion of said number space and said second portion is smaller than said first portion and wherein a data structure is stored in said means for storing data, said data structure comprises said first portion and said second portion and which specifies tags which are identified and portions of said number space in which there are no tags.

97. An apparatus as in claim 96 wherein said number space is a binary number space and said data structure is a binary tree, which is assembled as responses are received from tags.

98. An apparatus as in claim 96 wherein said apparatus is to transmit a second data without regard to whether said means for receiving received a single response from one tag or a plurality of responses from a plurality of tags.

99. An apparatus to identify at least one tag, which has an identifier code, said apparatus comprising:

means for controlling data;

means for transmitting data; and

means for receiving to receive a single bit response from at least one tag, said single bit response being in response to said data, wherein said data specifies at least a range of possible identifier codes.

100. An apparatus as in claim 99 wherein said apparatus is to transmit another data without regard to whether said means for receiving received a single response from one tag or a plurality of responses from a plurality of tags.

101. An apparatus as in claim 99 wherein said apparatus does not attempt to distinguish between a single response from only one tag indicating a match and a plurality of responses from tags each indicating a match.

102. An apparatus to identify a tag having an identification code, said apparatus comprising:

means for sending commands; and

means for transmitting said commands to any tags present, said commands causing a search of possible identification codes in a number space and said means for transmitting is to transmit a further command which requests tags in a portion of said number space to indicate whether said tags, if any, have a partial match to at least a part of an identification code, wherein if there are tags which are not yet identified in said portion, said apparatus is to transmit commands to search said portion before searching a larger portion of said number space.

103. An apparatus as in claim 102 wherein said search of said portion is a neighborhood search performed after identifying and muting a first tag which is also in said portion.

104. An apparatus to identify at least one tag having an identification code, said apparatus comprising:

means for transmitting, said means for transmitting is to transmit at least one command to any tags present, said command causing a search of possible identification codes and said means for transmitting is to transmit a portion of an identification code; and

means for receiving, said means for receiving is to receive in response to transmitting said portion of said identification code, a response, from a tag, which indicates a match to said portion and which indicates at least one next bit in said tag'"'"'s identification code.

105. An apparatus as in claim 104, further comprising:

means for determining, wherein said possible identification codes exist in a number space and wherein said means for determining is to determine a portion of said number space for further searching after receiving said at least one next bit in said response.

106. An apparatus as in claim 105 wherein said means for determining is to determine a relative strength of responses from tags indicating their corresponding at least one next bit.

107. An apparatus as in claim 106 wherein if said relative strength of a first next bit response exceeds a second next bit response, then said means for determining continues a search with said portion of said identification code and said first next bit response.

108. An apparatus as in claim 107 wherein said first next bit response is a “

1” and

said second next bit response is “

0.”