Enhanced uplink modulated backscatter system

• US 5,940,006 A
• Filed: 12/12/1995
• Issued: 08/17/1999
• Est. Priority Date: 12/12/1995
• Status: Expired due to Term

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Vannucci, Giovanni, MacLellan, John Austin, Shober, R. Anthony
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): BEAULIEU, YONEL
• Application Number:
  US08/571,004
• Time in Patent Office: 1,344 Days
• Field of Search: 340/825.54, 340/825.49, 340/825.35, 340/505, 340/568, 340/572, 340/573, 235/375, 235/435, 235/380, 342/44, 342/51, 455/88
• US Class Current: 370/314
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G06K 17/0022 arrangements or provisious for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous

Abstract

A Time Division Multiple Access (TDMA) duplex radio communication system uses an Interrogator to generate a first radio signal by modulating a first information signal onto a radio carrier signal which is sent to at least one remote Tag of the system. The remote Tag receives and modulates a second information signal onto a second radio carrier signal to form a second modulated signal which is transmitted, in a time-slotted manner, back to the Interrogator. The remote Tag selects, or is instructed, how many times it should repetitively transmit the second modulated signal; and selects, or is instructed, over how many of the time slots following receipt of the first radio signal the remote Tag should repetitively transmit the second modulated signal. Other embodiments use Modulated Backscatter to transmit the second modulated signal, and use homodyne detection to demodulate the second modulated signal. A Frequency Division Multiple Access (FDMA) duplex radio communication system embodiment utilizes multiple subcarrier frequencies and another embodiment combines the FDMA and the TDMA methods. A Code Division Multiple Access (CDMA) embodiment utilizes multiple spreading codes and another embodiment combines the CDMA and the TDMA methods.

Claims

1. A radio communication system comprising

an interrogator including

means to generate a first radio signal, and

means to transmit said first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to generate a second modulated signal by modulating a multiple bit digital second information signal onto a radio carrier signal,

means to divide time into a series of time slots, and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

2. The radio communication system of claim 1 wherein said interrogator generates a CW signal following said first radio signal and said at least one tag generates said second modulated signal utilizing modulated backscatter of said CW signal.

3. The radio communication system of claim 2 wherein said interrogator demodulating means utilizes homodyne detection.

4. The radio communication system of claim 1 wherein said means to modulate said second information signal onto said radio carrier signal utilizes phase shift keying.

5. The radio communication system of claim 1 wherein

said interrogator includes

means to generate said first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code, and

said at least one tag contains

means to demodulate said first information signal from said first radio signal, and

means to determine said operations code from said first information signal.

8. The radio communications system of claim 5 wherein

said interrogator includes

means to include at least one parameter, designated "Mode 2", in said first information signal;

and

said at least one tag includes

means to decode the contents of said "Mode 2" parameter from said first information signal, and

means to use the contents of "Mode 2" to determine how many of said time slots, following receipt of said first radio signal, said certain number of repetitions of said second modulated signal should be transmitted within.

9. The radio communication system of claim 8 wherein said interrogator further includes

means to monitor communications performance of said second modulated signals, and

means to dynamically adjust said "Mode 2" parameter based upon said communications performance of said second modulated signals.

10. The radio communications system of claim 5 wherein

said interrogator includes

means to include at least two additional parameters, designated "Mode 1" and "Mode 2", in said first information signal;

and

said tag includes

means to decode the contents of said "Mode 1" and said "Mode 2" parameters from said first information signal, and

means to use the contents of "Mode 1" to determine the number of said repetitions to use, and to use the contents of "Mode 2" to determine how many of said time slots, following receipt of said first radio signal, said number of said repetitions of said second modulated signal should be transmitted within.

11. The radio communication system of claim 10 wherein said interrogator further includes

means to monitor communications performance of said second modulated signals, and

means to dynamically adjust said "Mode 1" and said "Mode 2" parameters based upon said communications performance of said second modulated signals.

12. The radio communication system of claim 1 wherein said interrogator has means to repetitively transmit said first radio signal.

13. The radio communication system of claim 5 wherein said interrogator includes means to repetitively transmit said first radio signal.

16. The radio communications system of claim 5 wherein

said interrogator includes

means to generate a third information signal, containing at least a Tag Address, a Tag Command, and if data is necessary a Tag Data,

means to generate a third modulated signal by modulating said third information signal onto a radio carrier signal, and

means to transmit said third modulated signal to said at least one tag;

and

said tag includes

means to receive said third modulated signal,

means to demodulate said third information signal from said third modulated signal, and

means to decode said third information signal.

17. The radio communications system of claim 16 wherein said at least one tag includes

means to examine the contents of said Tag Address and said Tag Command,

means, responsive to the results of said examination, to determine if said at least one tag is addressed, and

means to determine if said Tag Command has been properly executed.

18. The radio communications system of claim 16 wherein

said interrogator includes means to transmit said first radio signal to said at least one tag following the transmission of said third modulated signal.

19. The radio communications system of claim 18 wherein

said at least one tag includes

means to generate a fourth information signal, which includes one or more fields selected from a group including a Tag Data field, a Synchronization field, a Tag Ack field, an Error Detect field, and a Correct field,

means to generate a fourth modulated signal by modulating said fourth information signal onto a radio carrier signal,

means to transmit said fourth modulated signal only if said operations code contained within said first information signal is "Tag Respond" and if said at least one tag is an addressed tag, and

means to not transmit said fourth modulated signal if said at least one tag is not an addressed tag;

and

said interrogator has

means to receive said fourth modulated signal, and

means to demodulate said fourth information signal from said fourth modulated signal.

23. The radio communications system of claim 19 wherein said Tag Data includes means to include the time slot numbers being used to transmit said second modulated signal by said at least one tag.

24. The radio communication system of claim 19 wherein at said at least one tag the means for modulating said second or fourth modulated signals onto said radio carrier signal utilizes modulated backscatter of a CW signal provided by said interrogator.

25. The radio communication system of claim 24 wherein said interrogator demodulating means utilizes homodyne detection.

30. The radio communications system of claim 1 wherein the series of time slots are of equal length.

31. The radio communications system of claim 1 wherein at least two of the series of time slots are not of equal length.

6. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code,

means to include at least one parameter, designated "Mode 1", in said first information signal, and

means to transmit said first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to decode the contents of said "Mode 1" parameter from said first information signal,

means to use the contents of "Mode 1" to determine how many repetitions of said second modulated signal to transmit,

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to divide time into a series of time slots, and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

7. The radio communication system of claim 6 wherein said interrogator further includes

means to monitor communications performance of said second modulated signals, and

means to dynamically adjust said "Mode 1" parameter based upon said communications performance of said second modulated signals.

14. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code and

means to transmit said first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to include within said second information signal at least one information field for said at least one tag selected from a group of fields including a unique identification field, a Synchronization field, an additional Data field, a Tag Ack field, an Error Detect field, and a Correct field,

means to transmit said second information signal upon receiving said operations code designated "PAMA Respond",

means to divide time into a series of time slots, and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

15. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code and

means to transmit said first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to not transmit any of said second modulated signals upon receiving said operations code designated "Listen",

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to divide time into a series of time slots, and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal;

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

20. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code,

means to generate a third information signal, containing at least a Tag Address, a Tag Command, and if data is necessary a Tag Data,

means to generate a third modulated signal by modulating said third information signal onto a radio carrier signal,

means to transmit said third modulated signal to said at least one tag and

means to transmit said first radio signal to said at least one tag following the transmission of said third modulated signal

said at least one tag including

means to receive said third modulated signal,

means to demodulate said third information signal from said third modulated signal,

means to decode said third information signal

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to divide time into a series of time slots,

means to generate said second information signal, contained within said second modulated signal, which contains "Positive Acknowledgment" in said Tag Ack field,

means to transmit said second modulated signal if said operations code contained within said first information signal is "PAMA Respond", and if said at least one tag is an addressed tag, and if said Tag Command has been properly executed and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal;

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

26. The radio communication system of claim 20 wherein at said at least one tag the means for modulating said second or fourth modulated signals onto said radio carrier signal utilizes modulated backscatter of a CW signal provided by said interrogator.

27. The radio communication system of claim 26 wherein said interrogator demodulating means utilizes homodyne detection.

21. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code,

means to generate a third information signal, containing at least a Tag Address, a Tag Command, and if data is necessary a Tag Data,

means to generate a third modulated signal by modulating said third information signal onto a radio carrier signal,

means to transmit said third modulated signal to said at least one tag, and

means to transmit said first radio signal to said at least one tag following the transmission of said third modulated signal;

said at least one tag including

means to receive said third modulated signal,

means to demodulate said third information signal from said third modulated signal,

means to decode said third information signal,

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to divide time into a series of time slots,

means to generate said second information signal, contained within said second modulated signal, which contains "Negative Acknowledgment" in said Tag Ack field,

means to transmit said second modulated signal if said operations code contained within said first information signal is "PAMA Respond", and if said at least one tag is either not addressed or properly executed and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

28. The radio communication system of claim 21 wherein at said at least one the means for modulating said second or fourth modulated signals onto said radio carrier signal utilizes modulated backscatter of a CW signal provided by said interrogator.

29. The radio communication system of claim 28 wherein said interrogator demodulating means utilizes homodyne detection.

22. A radio communication system comprising

an interrogator including

means to generate a first radio signal by modulating a first information signal onto a radio carrier signal, where said first information signal contains at least one operations code,

means to generate a third information signal, containing at least a Tag Address, a Tag Command, and if data is necessary a Tag Data,

means to generate a third modulated signal by modulating said third information signal onto a radio carrier signal,

means to transmit said third modulated signal to said at least one tag and

means to transmit said first radio signal to said at least one tag following the transmission of said third modulated signal;

said at least one tag including

means to receive said third modulated signal,

means to demodulate said third information signal from said third modulated signal,

means to decode said third information signal,

means to examine the contents of said Tag Address and said Tag Command,

means, responsive to the results of said examination, to determine if said at least one tag is addressed,

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal,

means to determine said operations code from said first information signal,

means to determine if said Tag Command has been properly executed,

means to make no further transmissions upon receiving said command "Quiet" within said Tag Command,

means to generate a second modulated signal by modulating a second information signal onto a radio carrier signal,

means to divide time into a series of time slots,

means to generate said second information signal, contained within said second modulated signal, which contains "Positive Acknowledgment" in said Tag Ack field,

means to transmit said second modulated signal if said operations code contained within said first information signal is "PAMA Respond", and if said at least one tag is an addressed tag, and if said Tag Command has been properly executed,

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal,

means to resume said transmissions of said second modulated signal upon reception of said first radio signal where said Operations Code contained within said first information signal contained within said first radio signal contains the command "Clear, PAMA Respond"; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

32. A radio communication system comprising

an interrogator including means to transmit a first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to generate and select one of a set of subcarriers,

means to generate a modulated subcarrier by modulating a second information signal onto said selected subcarrier,

means to generate a second modulated signal by modulating said modulated subcarrier onto a radio carrier signal, by using modulated backscatter, and

means to transmit said second modulated signal; and

said interrogator further including

means to demodulate said second modulated signal, to obtain said second information signal.

33. The radio communication system of claim 32 wherein said interrogator demodulating means utilizes homodyne detection.

34. The radio communication system of claim 32 wherein

said interrogator further includes

means to generate said first radio signal by modulating a first information signal onto a radio carrier signal, and

means to transmit said first radio signal to at least one tag;

and

said at least one tag further includes

means to receive said first radio signal,

means to demodulate said first information signal from said first radio signal, and

means to decode said first information signal.

35. The radio communication system of claim 34 wherein said at least one tag further includes means to perform said selection of said selected subcarrier based upon contents of said first information signal.

36. The radio communication system of claim 32 wherein said interrogator means to demodulate said second modulated signal includes a digital signal processor.

37. A radio communication system comprising

an interrogator including

means to generate a first radio signal,

means to transmit said first radio signal to at least one tag, and

means to divide time into a series of time slots;

said at least one tag including

means to receive said first radio signal,

means to create and select one of a set of subcarriers,

means to generate a modulated subcarrier by modulating a second information signal onto said selected subcarrier,

means to generate a second modulated signal by modulating said modulated subcarrier onto a radio carrier signal, by using modulated backscatter,

means to divide time into a series of time slots, where said time slots may or may not be of equal length, and

means to transmit N repetitions of said second modulated signal, where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

38. The radio communication system of claim 37 wherein said interrogator demodulating means utilizes homodyne detection.

39. The radio communication system of claim 37 wherein

said interrogator includes

means to generate said first radio signal by modulating a first information signal onto a radio carrier signal;

and

said at least one tag includes

means to demodulate said first information signal from said first radio signal, and

means to perform said selection of said selected subcarrier based upon contents of said first information signal.

40. The radio communication system of claim 37 wherein said interrogator demodulation means includes a digital signal processor.

41. The radio communications system of claim 37 wherein the series of time slots are of equal length.

42. The radio communications system of claim 37 wherein at least two of the series of time slots are not of equal length.

43. A radio communication system comprising

an interrogator including means to transmit a first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to create and select one of a set of spreading codes,

means to generate a spread information signal by modulating a second information signal onto said selected spreading code,

means to generate a second modulated signal by modulating said spread information signal onto a radio carrier signal portion of said first radio signal, by using modulated backscatter, and

means to transmit said second modulated signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

44. The radio communication system of claim 43 wherein

said interrogator further includes

means to generate said first radio signal by modulating a first information signal onto a radio carrier signal;

and

said at least one tag further includes

means to demodulate said first information signal from said first radio signal,

means to decode said first information signal, and

means to perform said selection of said selected spreading code based upon the contents of said first information signal.

45. The radio communication system of claim 43 wherein said interrogator demodulating means utilizes homodyne detection.

46. The radio communication system of claim 43 wherein said at least one tag includes means to change the reflection coefficient of the antenna.

47. The radio communication system of claim 46 wherein said means to change said reflection coefficient of said antenna includes means to vary the amount of modulation current through a diode modulator.

48. A radio communication system comprising

an interrogator including means to transmit a first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to create and select one of a set of spreading codes,

means to generate a spread information signal by modulating a second information signal onto said selected spreading code,

means to generate a second modulated signal by modulating said spread information signal onto a radio carrier signal, by using modulated backscatter,

means to divide time into a series of time slots, and

means to transmit N repetitions of said second modulated signal where N is two or more, within a certain number of said time slots following the reception of said first radio signal; and

said interrogator further including

means to receive said second modulated signal, and

means to demodulate said second modulated signal to obtain said second information signal.

49. The radio communication system of claim 48 wherein

said interrogator includes means to generate said first radio signal by modulating a first information signal onto a radio carrier signal;

and

said at least one tag further includes

means to demodulate said first information signal from said first radio signal,

means to decode said first information signal, and

means to perform said selection of said selected spreading code based upon the contents of said first information signal.

50. The radio communication system of claim 48 wherein said interrogator demodulating means utilizes homodyne detection.

51. The radio communication system of claim 48 wherein said interrogator demodulation means includes a digital signal processor.

52. The radio communications system of claim 48 wherein the series of time slots are of equal length.

53. The radio communications system of claim 48 wherein at least two of the series of time slots are not of equal length.

54. A radio communication system comprising

an interrogator including

means to generate a first radio signal, and

means to transmit said first radio signal to at least one tag;

said at least one tag including

means to receive said first radio signal,

means to generate a second modulated signal, by the use of modulated backscatter, by modulating a second information signal onto a radio carrier signal portion of said first radio signal,

means to continuously vary the reflection coefficient of the antenna contained within said at least one tag, and

means to transmit said second modulated signal; and

said interrogator further including

means to receive said second modulated signal.

55. The radio communication system of claim 54 wherein said means to continuously vary said reflection coefficient of said antenna includes means to vary the amount of modulation current through a diode modulator.

56. The radio communication system of claim 54 wherein

said interrogator includes means to demodulate said second information signal from said second modulated signal, and

said demodulating means utilizes homodyne detection.

57. The radio communication system of claim 54 wherein

said interrogator includes means to generate said first radio signal by modulating a first information signal onto a radio carrier signal;

and

said at least one tag includes

means to demodulate said first information signal from said first radio signal,

means to decode the contents of said first information signal, and

means to change said reflection coefficient of said antenna based upon the contents of said first information signal.

58. A radio communication tag comprising

receiver means to receive an interrogator radio signal,

means to generate a modulated signal by modulating a multiple bit digital second information signal onto a radio carrier signal,

means to divide time into a series of time slots, and

transmitter means to transmit the modulated radio signal, N times, where N is two or more, within a certain number of said time slots following the reception of said received interrogator radio signal.