Error recovery in RFID reader systems

• US 20060236203A1
• Filed: 03/22/2006
• Published: 10/19/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Colleran, William T., Bridges, Seth W., Diorio, Christopher J., Esterberg, Aanand
• Granted Patent: US 7,405,660 B2
• Time in Patent Office: Days
• US Class Current: 714/760
• CPC Class Codes: G06K 17/00 Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
• 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: H03M 13/09 Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit

Abstract

RFID systems, devices, software and methods are adapted for receiving from an RFID tag at least waves that communicate at least a first version of its code. An output tag code is output that is the same as the first version, if a fidelity criterion is met regarding the first version. If not met, the output tag code is instead a final version that is reconstructed from the first version, and also from any additionally optionally subsequently received versions. In some embodiments, an error recovery block includes a subcomponent fidelity criterion checking block that can determine whether the fidelity criterion is met, and a code reconstruction block that can derive the final version.

Claims

1. An RFID reader system for outputting a code of an RFID tag from waves received by a reader antenna, comprising:

input circuitry operable to decode from a first one of the waves a first version of the code; and

an operational processing block operable to determine whether a fidelity criterion regarding the first version is met, and if so to output the first version of the code, else to derive from the first version a final version of the code that is different from the first version, and to output the final version instead of the first version.

2. The system of claim 1, in which operational processing block includes

a fidelity criterion checking block operable to determine whether the fidelity criterion is met, and

a code reconstruction block operable to derive the final version, if the fidelity criterion regarding the first version is not met.

3. The system of claim 1, in which

the fidelity criterion is met regarding the final version.

4. The system of claim 1, in which

the input circuitry operable to further decode from the first wave at least one checking bit, and

in which the fidelity criterion is met if a preset correspondence between the first version and the checking bit is met.

5. The system of claim 4, in which

the correspondence is a parity type checking.

6. The system of claim 4, in which

the correspondence is a Cyclic Redundancy Checking.

7. The system of claim 1, in which

the first version includes sampled data values that span a range, and

the fidelity criterion is met if none of the sampled data values is within a suspect window of the range.

8. The system of claim 1, further comprising:

a memory block operable to store a developing statistic about previously outputted versions of other codes, and

in which the statistic is compared to an aspect of the first version to determine whether the fidelity criterion is met.

9. The system of claim 1, in which

the first version includes first ordered samples at least one of which is suspect,

a first trial version is generated from most of the first ordered samples, but with changing the suspect sample, and

the first trial version becomes the final version if the fidelity criterion is met regarding the first trial version.

10. The system of claim 9, in which

the samples are logical bits.

11. The system of claim 9, in which

a second trial version is generated that is different from the first trial version and from the first received version, if the fidelity criterion is met regarding the first trial version, and

the second trial version becomes the final version if the fidelity criterion is met regarding the second trial version.

12. The system of claim 9, in which

the samples correspond to respective sampled data values that span a range, and

the suspect sample is identified as being the one whose sampled data value is closest to a decision threshold of the range.

13. The system of claim 12, in which

the range is between a minimum and a maximum, and

the decision threshold is derived as a statistic of the minimum and the maximum.

14. The system of claim 12, in which

the decision threshold becomes adjusted later responsive to the sampled data values.

15. The system of claim 1, in which

the final version is derived and outputted without decoding another version of the code.

16. The system of claim 1, in which

the input circuitry is further operable to decode from a second one of the waves a second version of the code, and

the reconstruction block is operable to derive the final version also from the second version.

17. The system of claim 16, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version is derived from the first and second samples that are similar, and by arbitrating between the first and the second samples that are different.

18. The system of claim 17, in which

the first and second samples are logical bits.

19. The system of claim 17, in which

arbitrating is performed by

generating a trial version from at least one the first version and the second version, and

determining whether the fidelity criterion is met for the trial version.

20. The system of claim 16, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version includes final ordered samples that correspond to and are derived from statistics of the first ordered samples and the second ordered samples.

21. The system of claim 16, in which

the input circuitry is further operable to decode from a third one of the waves a third version of the code, and

the reconstruction block is operable to derive the final version also from the third version.

22. The system of claim 21, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the third version is received if a number of the first samples and the second samples that are different exceeds a threshold.

23. The system of claim 21, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples,

the third version includes third ordered samples that correspond to the first and the second ordered samples, and

the final version is derived from the first, second and third samples that are similar, and by arbitrating between the first, second and third samples that are different.

24. The system of claim 23, in which

arbitrating is performed by majority voting between the first, second and third samples, where they are different.

25. A method for an RFID reader system to output a code of a first RFID tag, comprising:

receiving from the tag a first wave;

decoding from the first wave a first version of the code;

determining whether a fidelity criterion regarding the first version is met; and

if so, outputting the first version of the code,

else if not, deriving from the first version a final version of the code that is different from the first version, and outputting the final version instead of the first version.

26. The method of claim 25, in which

the fidelity criterion is met regarding the final version.

27. The method of claim 25, further comprising:

decoding from the first wave at least one checking bit, and

in which the fidelity criterion is met if a preset correspondence between the first version and the checking bit is met.

28. The method of claim 27, in which

the correspondence is a parity type checking.

29. The method of claim 27, in which

the correspondence is a Cyclic Redundancy Checking.

30. The method of claim 25, in which

the first version includes sampled data values that span a range, and

the fidelity criterion is met if none of the sampled data values is within a suspect window of the range.

31. The method of claim 25, further comprising:

storing a developing statistic about previously outputted versions of other codes, and

in which the statistic is compared to an aspect of the first version to determine whether the fidelity criterion is met.

32. The method of claim 25, in which

the first version includes first ordered samples at least one of which is suspect,

a first trial version is generated from most of the first ordered samples, but with changing the suspect sample, and

the first trial version becomes the final version if the fidelity criterion is met regarding the first trial version.

33. The method of claim 32, in which

the samples are logical bits.

34. The method of claim 32, in which

a second trial version is generated that is different from the first trial version and from the first received version, if the fidelity criterion is met regarding the first trial version, and

the second trial version becomes the final version if the fidelity criterion is met regarding the second trial version.

35. The method of claim 32, in which

the samples correspond to respective sampled data values that span a range, and

the suspect sample is identified as being the one whose sampled data value is closest to a decision threshold of the range.

36. The method of claim 35, in which

the range is between a minimum and a maximum, and

the decision threshold is derived as a statistic of the minimum and the maximum.

37. The method of claim 35, in which

the decision threshold becomes adjusted later responsive to the sampled data values.

38. The method of claim 25, in which

the final version is derived and outputted without decoding another version of the code.

39. The method of claim 25, further comprising:

receiving from the tag a second wave;

decoding from the second wave a second version of the code, and

in which the final version is derived also from the second version.

40. The method of claim 39, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version is derived from the first and second samples that are similar, and by arbitrating between the first and the second samples that are different.

41. The method of claim 40, in which

the first and second samples are logical bits.

42. The method of claim 40, in which

arbitrating is performed by generating a trial version from at least one the first version and the second version, and

determining whether the fidelity criterion is met for the trial version.

43. The method of claim 39, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version includes final ordered samples that correspond to and are derived from statistics of the first ordered samples and the second ordered samples.

44. The method of claim 39, further comprising:

receiving from the tag a third wave;

decoding from the third wave a third version of the code, and

in which the final version is derived also from the third version.

45. The method of claim 44, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the third version is received if a number of the first samples and the second samples that are different exceeds a threshold.

46. The method of claim 44, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples,

the third version includes third ordered samples that correspond to the first and the second ordered samples, and

the final version is derived from the first, second and third samples that are similar, and by arbitrating between the first, second and third samples that are different.

47. The method of claim 46, in which

arbitrating is performed by majority voting between the first, second and third samples, where they are different.

48. An RFID reader system comprising:

receiving means for receiving from an RFID tag a first wave;

decoding means for decoding from the first wave a first version of a code of the tag;

determining means for determining whether a fidelity criterion regarding the first version is met;

deriving means for deriving from the first version a final version of the code that is different from the first version, and

outputting means for outputting the first version of the code if the fidelity criterion is met regarding the first version, and the final version instead of the first version otherwise.

49. The system of claim 48, in which

the fidelity criterion is met regarding the final version.

50. The system of claim 48, in which

the decoding means is operable to further decode from the first wave at least one checking bit, and

the fidelity criterion is met if a preset correspondence between the first version and the checking bit is met.

51. The system of claim 50, in which

the correspondence is a parity type checking.

52. The system of claim 50, in which

the correspondence is a Cyclic Redundancy Checking.

53. The system of claim 48, in which

the first version includes sampled data values that span a range, and

the fidelity criterion is met if none of the sampled data values is within a suspect window of the range.

54. The system of claim 48, in which

the first version includes first ordered samples at least one of which is suspect,

a first trial version is generated from most of the first ordered samples, but with changing the suspect sample, and

the first trial version becomes the final version if the fidelity criterion is met regarding the first trial version.

55. The system of claim 54, in which

the samples are logical bits.

56. The system of claim 54, in which

a second trial version is generated that is different from the first trial version and from the first received version, if the fidelity criterion is met regarding the first trial version, and

the second trial version becomes the final version if the fidelity criterion is met regarding the second trial version.

57. The system of claim 54, in which

the samples correspond to respective sampled data values that span a range, and

the suspect sample is identified as being the one whose sampled data value is closest to a decision threshold of the range.

58. The system of claim 57, in which

the range is between a minimum and a maximum, and

the decision threshold is derived as a statistic of the minimum and the maximum.

59. The system of claim 48, in which

the final version is derived and outputted without decoding another version of the code.

60. The system of claim 48, in which

the receiving means is operable to receive from the tag a second wave,

the decoding means is operable to decode from the second wave a second version of the code, and

the final version is derived also from the second version.

61. The system of claim 60, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version is derived from the first and second samples that are similar, and by arbitrating between the first and the second samples that are different.

62. The system of claim 61, in which

the first and second samples are logical bits.

63. The system of claim 61, in which

arbitrating is performed by generating a trial version from at least one the first version and the second version, and

determining whether the fidelity criterion is met for the trial version.

64. The system of claim 60, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version includes final ordered samples that correspond to and are derived from statistics of the first ordered samples and the second ordered samples.

65. An article comprising:

a memory having instructions stored thereon, in which when the instructions are executed by an operational processing block, they result in;

determining whether a fidelity criterion is met regarding a first version of a tag code decoded from a first wave received from an RFID tag; and

if so, outputting the first version of the code, else if not, deriving from the first version a final version of the code that is different from the first version, and outputting the final version instead of the first version.

66. The article of claim 65, in which

the fidelity criterion is met regarding the final version.

67. The article of claim 65, in which

the first version includes sampled data values that span a range, and

the fidelity criterion is met if none of the sampled data values is within a suspect window of the range.

68. The article of claim 65, in which

the first version includes first ordered samples at least one of which is suspect,

a first trial version is generated from most of the first ordered samples, but with changing the suspect sample, and

the first trial version becomes the final version if the fidelity criterion is met regarding the first trial version.

69. The article of claim 68, in which

the samples are logical bits.

70. The article of claim 68, in which

a second trial version is generated that is different from the first trial version and from the first received version, if the fidelity criterion is met regarding the first trial version, and

the second trial version becomes the final version if the fidelity criterion is met regarding the second trial version.

71. The article of claim 68, in which

the samples correspond to respective sampled data values that span a range, and

the suspect sample is identified as being the one whose sampled data value is closest to a decision threshold of the range.

72. The article of claim 71, in which

the range is between a minimum and a maximum, and

the decision threshold is derived as a statistic of the minimum and the maximum.

73. The article of claim 71, in which

the decision threshold becomes adjusted later responsive to the sampled data values.

74. The article of claim 65, in which

the final version is derived and outputted without decoding another version of the code.

75. The article of claim 65, in which

the final version is derived also from a second version of the tag code decoded from a second wave received from the RFID tag.

76. The article of claim 75, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version is derived from the first and second samples that are similar, and by arbitrating between the first and the second samples that are different.

77. The article of claim 76, in which

the first and second samples are logical bits.

78. The article of claim 76, in which

arbitrating is performed by

generating a trial version from at least one the first version and the second version, and

determining whether the fidelity criterion is met for the trial version.

79. The article of claim 75, in which

the first version includes first ordered samples,

the second version includes second ordered samples that correspond to the first ordered samples, and

the final version includes final ordered samples that correspond to and are derived from statistics of the first ordered samples and the second ordered samples.