Systems and methods for interference mitigation with respect to periodic interferers in short-range wireless applications

• US 7,079,812 B2
• Filed: 01/20/2003
• Issued: 07/18/2006
• Est. Priority Date: 05/16/2002
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cognio, Inc. (Cisco Systems, Inc.)
• Inventors: Diener, Neil R., Miller, Karl A., Kloper, David S.
• Primary Examiner(s): Milord, Marceau
• Application Number:
  US10/248,434
• Publication Number:
  US 20040203474A1
• Time in Patent Office: 1,275 Days
• Field of Search: 455/41.2, 455/69, 455/63.1, 455/67.11, 455/67.13, 455/501, 375/130, 375/134, 375/132, 340/572.1, 340/10.33, 340/448, 370/342, 370/395.42
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04

Abstract

Several techniques are provided for use by wireless devices to avoid interference with signals that are of a periodic or quasi-periodic nature that may operate in the same frequency band and proximity. In some cases, the periodic signals are detected and their timing is determined so as to predict when a next interfering event will occur. Devices that are affected by the periodic signal (such as an affected device with information to be transmitted or devices that have information to be transmitted to the affected device) are controlled to prevent transmissions during the interfering intervals. In addition, a process is provided to dynamically fragment a transmit frame of information to transmit part of the information before the interfering interval and the remainder of the information after the interfering interval, rather than waiting to transmit the entire frame until after the interfering interval. Moreover, techniques are provided to correct for clock drift between the periodic signal and a device affected by the periodic signal, as well as for clock drift between a device affected by the periodic signal and other devices that communicate with that device. These techniques prevent interference with periodic signals and in so doing, improve the quality of service of the communication link for both the interfering devices and the other devices.

Claims

1. A method for wireless communication between first and second communication devices, a method comprising:

a. at the first communication device;

i. detecting a periodic or quasi-periodic wireless signal;

ii. generating information describing the wireless signal including a start time, duration of an interference interval during which the wireless signal is present and may interfere with signals transmitted to or from the first communication device, and period of occurrence of the wireless signal; and

iii. transmitting a message to the second communication device containing the information describing the wireless signal;

b. at the second communication device;

i. receiving the message containing the information describing the wireless signal from the first communication device; and

ii. scheduling transmissions of signals to the first communication device to avoid interfering with the wireless signal based on the information contained in the message.

2. The method of claim 1, and further comprising, at the first communication device, steps of determining a clock drift between the wireless signal and the first communication device to allow for correction of the clock drift at the first communication device or second communication device.

3. The method of claim 2, and further comprising the step at either the first communication device or second communication device of adding a time period cushion to the beginning or end of the interference interval associated with the occurrence of the wireless signal to account for the clock drift.

4. The method of claim 3, and further comprising the step of occasionally or periodically measuring the clock drift so as to minimize the length of the time period cushion added to the interference interval associated with the occurrence of the wireless signal.

5. The method of claim 1, and further comprising, at the first communication device, steps of determining a clock drift between the first communication device and the second communication device to allow for correction of the clock drift at the first communication device or second communication device.

6. The method of claim 5, wherein the step of determining the clock drift between the first communication device and the second communication device is based on time stamp information contained in a signal transmitted by one of the first and second communication devices to the other.

7. The method of claim 1, and further comprising the step of transmitting from the first communication device to the second communication device a message informing the second communication device that the wireless signal has subsided or terminated.

8. The method of claim 1, and further comprising receiving signals from one or more other communication devices at the second communication device and transmitting signals to the one or more other communication devices from the second communication device when the wireless signal detected at the first communication device does not affect the one or more other communication devices or the second communication device.

9. The method of claim 1, and further comprising the step, at the second communication device, of transmitting a message to a plurality of other communication devices in a wireless network, the message containing the information about the wireless signal.

10. The method of claim 1, wherein at the first communication or second communication device, further comprising the step of dividing a frame of information to be transmitted into at least first and second sub-frames such that the first sub-frame is transmitted prior to the interference interval and the second sub-frame is transmitted after the interference interval.

11. The method of claim 10, and further comprising determining whether there is sufficient time remaining before the interference interval to receive an acknowledgment message from a device that received the first sub-frame, wherein the first sub-frame is transmitted prior to the interference interval if there sufficient time.

12. The method of claim 10, wherein the step of transmitting the first sub-frame comprises designating in the first sub-frame a reservation of the radio frequency channel of sufficient time to allow for the first sub-frame, the interference interval and the second sub-frame.

13. The method of claim 1, and further comprising steps of:

a. at the first communication device, synchronizing a clock module to the wireless signal detected by the first communication device; and

b. at the second communication device, synchronizing a clock module to the wireless signal reported by the first communication to the second communication device.

14. The method of claim 13, wherein at the first communication device, further comprising synchronizing a clock module to each periodic or quasi-periodic wireless signal detected by the first communication device.

15. The method of claim 14, wherein at the second communication device, further comprising synchronizing a clock module to each periodic or quasi-periodic wireless signal reported by the first communication device and any other communication device in the wireless network that detects a periodic or quasi-periodic wireless signal.

16. The method of claim 15, wherein at the second communication device, further comprising storing information to associate each synchronized clock module to the corresponding communication device that reported it to the second communication device.

17. The method of claim 1, wherein at the first communication device, the step of transmitting the message containing the information about the wireless signal comprises transmitting the message to a plurality of communication devices to inform them about the interference experienced by the first communication device so that the plurality of communication devices schedule transmissions to the first communication device not to coincide with the wireless signal detected by the first communication device.

18. A processor readable medium encoded with instructions that, when executed by a processor, cause the processor to perform steps comprising:

a. generating information describing a periodic or quasi-periodic wireless signal including a start time, duration of an interference interval during which the wireless signal is present, and period of occurrence of the wireless signal; and

b. generating a message to be transmitted by the first communication device to a second communication device, the message including the information describing the wireless signal.

19. The processor readable medium of claim 18, and further comprising instructions encoded on the medium to generate information pertaining to clock drift between the first communication device and the wireless signal and/or between the first communication device and the second communication device to allow for correction for the clock drift.

20. The processor readable medium of claim 19, and further comprising instructions encoded on the medium to generate a time period cushion to be added to the beginning and/or end of the interference interval associated with the occurrence of the wireless signal to account for the clock drift.

21. The processor readable medium of claim 20, and further comprising instructions encoded on the medium to generate a message to be transmitted by the first communication device to the second communication device that indicates that the wireless signal has terminated.

22. The processor readable medium of claim 18, and further comprising instructions encoded on the medium to generate a message for transmission to a plurality of other communication devices, the message containing the information about the wireless signal.

23. The processor readable medium of claim 18, and further comprising instructions encoded on the medium to divide a frame of information to be transmitted into at least first and second sub-frames such that the first sub-frame is transmitted prior to occurrence of the interference interval and the second sub-frame is transmitted after the interference interval.

24. The processor readable medium of claim 23, and further comprising instructions encoded on the medium for determining if there is sufficient time remaining before the interference interval to transmit the first sub-frame and receive an acknowledgment message from a device that received the first sub-frame.

25. The processor readable medium of claim 23, and further comprising instructions encoded on the medium for designating in the first sub-frame a reservation of the radio frequency channel of sufficient time to allow for the first sub-frame, the interference interval and the second sub-frame.

26. A radio communication device comprising the processor readable medium of claim 18, and further comprising a processor coupled to the processor readable medium that executes the instructions encoded thereon, a radio transceiver for transmitting and receiving radio signals and a baseband modem coupled to the processor and to the radio transceiver for generating signals containing information to be transmitted and recovering information from signals that are received by the radio transceiver.

27. The radio communication device of claim 26, and further comprising a clock module that synchronizes to each periodic or quasi-periodic wireless signal detected by the first communication device.

28. A processor readable medium encoded with instructions that, when executed by a processor, cause the processor to perform steps comprising:

a. receiving at a second communication device a message from a first communication device containing information describing a periodic or quasi-periodic wireless signal including a start time, duration of an interference interval during which the wireless signal is present, and period of occurrence of the wireless signal; and

b. scheduling transmissions of signals to the first communication device during times to avoid interfering with the wireless signal detected by the first communication device based on the information contained in the message.

29. The processor readable medium of claim 28, and further comprising instructions encoded on the medium to cause resumption of normal scheduling of transmissions to the first communication device in response to receiving a message from the first communication device that the wireless signal has terminated.

30. The processor readable medium of claim 28, and further comprising instructions encoded on the medium to schedule transmissions of signals with respect to the interference interval associated with the occurrence of the wireless signal to account for clock drift between the first communication device and the wireless signal and/or clock drift between the first communication device and the second communication device.

31. The processor readable medium of claim 28, and further comprising instructions encoded on the medium to divide a frame of information to be transmitted from the second communication device to the first communication into at least first and second sub-frames such that the first sub-frame is transmitted prior to occurrence of the interference interval and the second sub-frame is transmitted after the interference interval.

32. The processor readable medium of claim 31, and further comprising instructions encoded on the medium for determining if there is sufficient time remaining before the interference interval to transmit the first sub-frame to the first communication device and receive an acknowledgment message from the first communication device that it received the first sub-frame.

33. The processor readable medium of claim 31, and further comprising instructions encoded on the medium for designating in the first sub-frame a reservation of the radio frequency channel of sufficient time to allow for the transmission of first sub-frame by the second communication device, occurrence of the interference interval, and transmission of the second sub-frame by the second communication device.

34. A radio communication device comprising the processor readable medium of claim 28, and further comprising a processor coupled to the processor readable medium that executes the instructions encoded thereon, a radio transceiver for transmitting and receiving radio signals and a baseband modem coupled to the processor and to the radio transceiver for generating signals carrying information to be transmitted and recovering information from signals that are received by the radio transceiver.

35. The radio communication device of claim 34, and further comprising a clock module that synchronizes to each periodic or quasi-periodic wireless signal reported to the second communication device.

36. A wireless communication method comprising steps of:

a. detecting a periodic or quasi-periodic wireless signal at a first communication device; and

b. transmitting a first signal from the first communication device that will cause communication devices that receive it to defer transmissions to the first communication device for a time period corresponding to a time interval of occurrence of the wireless signal detected by the first communication device.

37. The method of claim 36, and further comprising steps at a second communication device, of:

c. receiving the first signal from the first communication device; and

d. transmitting a second signal intended to be received by a plurality of communication devices that informs them to defer transmissions to the first communication device for the time period corresponding to the time interval of occurrence of the wireless signal.

38. The method of claim 37, wherein the step of transmitting the first signal comprises transmitting a signal that will cause other communication devices compliant with one or more communication protocols to defer transmissions to the first communication device for a time period corresponding to the time interval of occurrence of the wireless signal.

39. The method of claim 38, wherein the step of transmitting the second signal from the second communication device comprises transmitting a signal compliant with the one or more communication protocols to defer transmissions to the first communication device for a time period corresponding to the time interval of occurrence of the wireless signal.

40. The method of claim 39, wherein the step of transmitting the first signal comprises transmitting a request-to-send (RTS) packet in accordance with an IEEE 802.11 communication protocol, and the step of transmitting the second signal comprises transmitting a clear-to-send (CTS) packet in accordance with the IEEE 802.11 communication protocol, the CTS packet including a field informing communication devices that receive it not to transmit for the time interval of occurrence of the wireless signal.

41. The method of claim 38, wherein the step of transmitting the first signal comprises transmitting a clear-to-send (CTS) packet in accordance with an IEEE 802.11 communication protocol, the CTS packet including a field informing communication devices that receive it not to transmit for the time interval of occurrence of the wireless signal.

42. The method of claim 36, and further comprising detecting clock drift between the wireless signal and the first communication device and/or clock drift between the first communication device and another communication device to allow for correction of the clock drift.

43. A method for avoiding interference with a periodic or quasi-periodic wireless signal, comprising steps of:

a. detecting a periodic or quasi-periodic wireless signal at a first communication device;

b. determining a start time, duration of an interference interval during which the wireless signal is present, and period of occurrence of the wireless signal;

c. receiving a signal from at least one other communication device; and

d. suppressing transmission of a response signal that should be transmitted in response to the signal received from the other communication device if the response signal would be scheduled for transmission during the interference interval of the wireless signal.

44. The method of claim 43, wherein the step of suppressing transmission of a response signal comprises suppressing transmission of an acknowledgment signal to a signal received from the other communication device.

45. The method of claim 43, wherein the step of suppressing transmission of a response signal comprises suppressing transmission of a signal intended to be received a plurality of communication devices that informs communication devices that receive the signal not to transmit for a time period corresponding to a requested reservation.

46. The method of claim 45, wherein the step of suppressing transmission comprises suppressing transmission of a clear-to-send (CTS) packet.

47. The method of claim 43, wherein the step of suppressing transmission further comprises correcting for a clock drift between the first communication device and the wireless signal.

48. A method for avoiding interference with a periodic of or quasi-periodic wireless signal, comprising steps of:

a. detecting a periodic or quasi-periodic wireless signal at a first communication device;

b. determining a start time, duration of an interference interval during which the wireless signal is present, and period of occurrence of the wireless signal;

c. detecting a clock drift between the wireless signal and the first communication device; and

d. scheduling transmissions by the first communication device to avoid the wireless signal, corrected for the clock drift.

49. The method of claim 48, and further comprising transmitting a signal to a second communication device that allows the second communication device to schedule transmissions to the first communication device so as to avoid the wireless signal.

50. The method of claim 49, and further comprising steps of detecting a clock drift between the first communication device and a second communication device to allow for correction for the clock drift by the first communication device or the second communication device.

51. The method of claim 48, and further comprising the step of occasionally or periodically measuring the clock drift so as to minimize a length of a time period cushion added to the interference interval associated with the occurrence of the wireless signal.

52. A method for scheduling transmission of signals from a first communication device to a second communication device comprising steps of:

a. detecting a periodic or quasi-periodic wireless signal;

b. determining a duration of an interference interval during which the wireless signal is present and period of occurrence of the wireless signal; and

c. dividing a frame of information to be transmitted into at least first and second sub-frames such that the first sub-frame is transmitted prior to occurrence of the interference interval and the second sub-frame is transmitted after the interference interval.

53. The method of claim 52, and further comprising determining whether there is sufficient time remaining before the interference interval to receive an acknowledgment message from a device that received the first sub-frame, wherein the first sub-frame is transmitted and the acknowledgment message is received prior to the interference interval.

54. The method of claim 52, and further comprising detecting a clock drift between the first communication and the wireless signal to correct for the clock drift in scheduling transmissions from the first communication device.