RFID readers transmitting preambles denoting communication parameters and RFID tags interpreting the same and methods

• US 7,501,953 B2
• Filed: 07/13/2004
• Issued: 03/10/2009
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Diorio, Christopher J., Cooper, Scott Anthony
• Primary Examiner(s): Lee; Benjamin C
• Assistant Examiner(s): Mehmood; Jennifer
• Application Number:
  US10/890,976
• Publication Number:
  US 20050225447A1
• Time in Patent Office: 1,701 Days
• Field of Search: 370/468, 370/470, 370/471, 370/473, 340 101- 1051, 3405721-5729, 340/7.43, 340/825.2, 340/825.21, 455/41.2, 455/41.3, 455/556.1, 455/556.2, 455/136, 709/209, 709/233, 709/224, 709/237
• US Class Current: 340/572.4
• 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 7/10297 arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092 cryptographic protocols H04L9/00; network security protocols H04L63/00; real-time communication protocols in data switching networks H04L65/00; network protocols for data switching network services H04L67/00

Abstract

RFID readers transmit data to query RFID tags. Before transmitting the data, the RFID readers also transmit special preambles that inform of parameters of communication that are to be used. RFID tags decode the preamble, and adjust accordingly to optimize the communication. The preambles of the invention start with a delimiter that has a substantially constant duration regardless of the communication parameters that will be used, such as transmission data rate.

Claims

1. An RFID reader adapted to at least:

transmit to an RFID tag a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion that encodes a first communication parameter other than a transmission data rate of the reader; and

then exchange data with the tag according to the first communication parameter.

2. The RFID reader of claim 1, wherein the reader is further adapted to:

determine the first communication parameter for encoding in the protocol portion.

3. The RFID reader of claim 1, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

4. The RFID reader of claim 1, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

5. The RFID reader of claim 4, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

6. The RFID reader of claim 4, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

7. The RFID reader of claim 1, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a variable duty cycle of the violation.

8. The RFID reader of claim 1, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a duration of the violation.

9. The RFID reader of claim 1, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

10. The RFID reader of claim 9, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

11. The RFID reader of claim 9, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

12. The RFID reader of claim 1, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

13. The RFID reader of claim 1, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

14. The RFID reader of claim 13, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

15. The RFID reader of claim 1, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

16. The RFID reader of claim 1, wherein

a second communication parameter is encoded in the protocol portion, and

exchanging data is performed also according to the second communication parameter.

17. The RFID reader of claim 16, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

18. The RFID reader of claim 16, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

19. The RFID reader of claim 18, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

20. The RFID reader of claim 18, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

21. A device comprising:

means for transmitting to an RFID tag a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion that encodes a first communication parameter other than a transmission data rate of the reader; and

means for exchanging data with the tag according to the transmitted first communication parameter.

22. The device of claim 21, further comprising:

means for determining the first communication parameter for encoding in the protocol portion.

23. The device of claim 21, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

24. The device of claim 21, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

25. The device of claim 24, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

26. The device of claim 24, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

27. The device of claim 21, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a variable duty cycle of the violation.

28. The device of claim 21, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a duration of the violation.

29. The device of claim 21, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

30. The device of claim 29, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

31. The device of claim 29, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

32. The device of claim 21, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

33. The device of claim 21, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

34. The device of claim 33, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

35. The device of claim 21, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

36. The device of claim 21, wherein

a second communication parameter is encoded in the protocol portion, and exchanging data is performed also according to the second communication parameter.

37. The device of claim 36, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

38. The device of claim 36, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

39. The device of claim 38, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

40. The device of claim 36, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

41. A method for an RFID reader, comprising:

transmitting to an RFID tag a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion that encodes a first communication parameter other than a transmission data rate of the reader; and

then exchanging data with the tag according to the first communication parameter.

42. The method of claim 41, further comprising:

determining the first communication parameter for encoding in the protocol portion.

43. The method of claim 41, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

44. The method of claim 41, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

45. The method of claim 43, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

46. The method of claim 43, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

47. The method of claim 41, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a variable duty cycle of the violation.

48. The method of claim 41, wherein

the protocol portion includes a violation, and

the first communication parameter is encoded in a duration of the violation.

49. The method of claim 41, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

50. The method of claim 49, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

51. The method of claim 49, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

52. The method of claim 41, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

53. The method of claim 41, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

54. The method of claim 53, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

55. The method of claim 41, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

56. The method of claim 41, wherein

a second communication parameter is encoded in the protocol portion, and

exchanging data is performed also according to the second communication parameter.

57. The method of claim 56, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

58. The method of claim 56, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

59. The method of claim 58, wherein

the backscatter rate of the tag is to be determined also from the transmission data rate.

60. The method of claim 56, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

61. An RFID tag adapted to at least:

receive from an RFID reader a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion;

decode from the protocol portion a first communication parameter other than a transmission data rate of the reader; and

then exchange data with the reader according to the decoded first communication parameter.

62. The RFID tag of claim 61, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

63. The RFID tag of claim 61, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

64. The RFID tag of claim 63, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

65. The RFID tag of claim 63, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

66. The RFID tag of claim 61, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a variable duty cycle of the violation.

67. The RFID tag of claim 61, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a duration of the violation.

68. The RFID tag of claim 61, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

69. The RFID tag of claim 68, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

70. The RFID tag of claim 68, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

71. The RFID tag of claim 61, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

72. The RFID tag of claim 61, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

73. The RFID tag of claim 72, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

74. The RFID tag of claim 61, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

75. The RFID tag of claim 61, wherein

a second communication parameter is encoded in the protocol portion, and exchanging data is performed also according to the second communication parameter.

76. The RFID tag of claim 75, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

77. The RFID tag of claim 75, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

78. The RFID tag of claim 77, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

79. The RFID tag of claim 75, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

80. A device comprising:

means for receiving from an RFID reader a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion;

means for decoding from the protocol portion a first communication parameter other than a transmission data rate of the reader; and

means for exchanging data with the reader according to the decoded first communication parameter.

81. The device of claim 80, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

82. The device of claim 80, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

83. The device of claim 82, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

84. The device of claim 82, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

85. The device of claim 80, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a variable duty cycle of the violation.

86. The device of claim 80, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a duration of the violation.

87. The device of claim 80, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

88. The device of claim 87, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

89. The device of claim 87, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

90. The device of claim 80, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

91. The device of claim 80, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

92. The device of claim 91, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

93. The device of claim 80, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

94. The device of claim 80, wherein

a second communication parameter is encoded in the protocol portion, and

exchanging data is performed also according to the second communication parameter.

95. The device of claim 94, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

96. The device of claim 94, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

97. The device of claim 96, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

98. The device of claim 94, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

99. A method for an RFID tag, comprising:

receiving from an RFID reader a preamble that includes a delimiter portion of a duration substantially equal to a preset delimiter duration, and a protocol portion;

decoding from the protocol portion a first communication parameter other than a transmission data rate of the reader; and

then exchanging data with the reader according to the first communication parameter.

100. The method of claim 99, wherein

the preset delimiter duration is one of approximately 12.5 μ

sec and approximately 6.25 μ

sec.

101. The method of claim 99, wherein

the protocol portion includes a pattern that identifies the start of a transmission of data, and

the first communication parameter is encoded in a timing of features of the pattern.

102. The method of claim 101, wherein

the pattern includes a pulse, and

the timing is that of a duration of the pulse.

103. The method of claim 101, wherein

the pattern includes a pulse, and

the timing is that of a duty cycle of the pulse.

104. The method of claim 99, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a variable duty cycle of the violation.

105. The method of claim 99, wherein

the protocol portion includes a violation, and

the first communication parameter is decoded from a duration of the violation.

106. The method of claim 99, wherein

the protocol portion includes a violation and a group of auxiliary transitions, and

the first communication parameter is encoded in a timing of the auxiliary transitions.

107. The method of claim 106, wherein

at least a portion of the group of auxiliary transitions occurs before the violation.

108. The method of claim 106, wherein

at least a portion of the group of auxiliary transitions occurs after the violation.

109. The method of claim 99, wherein

the first communication parameter is associated with a desired mode of encoding symbols by the tag.

110. The method of claim 99, wherein

the first communication parameter is associated with a desired backscatter rate of the tag.

111. The method of claim 110, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

112. The method of claim 99, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

the first communication parameter is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.

113. The method of claim 99, wherein

a second communication parameter is encoded in the protocol portion, and exchanging data is performed also according to the second communication parameter.

114. The method of claim 113, wherein

one of the first and second communication parameters is associated with a desired mode of encoding symbols by the tag.

115. The method of claim 113, wherein

one of the first and second communication parameters is associated with a desired backscatter rate of the tag.

116. The method of claim 115, wherein

the backscatter rate of the tag is determined also from the transmission data rate.

117. The method of claim 113, wherein

the data is encoded in terms of at least two symbols having different symbol durations, and

one of the first and second communication parameters is associated with one of a ratio of the symbol durations and a suggested checkpoint value for the symbols.