Detecting a hidden node in a wireless local area network

• US 20030174680A1
• Filed: 03/14/2002
• Published: 09/18/2003
• Est. Priority Date: 03/14/2002
• Status: Active Grant

• Current Assignee: NetScout Systems Incorporated
• Original Assignee: Airmagnet (NetScout Systems Incorporated)
• Inventors: Kuan, Chia-Chee, Wu, Miles, Au, Dean
• Granted Patent: US 7,130,289 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/188 Time-out mechanisms
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method and system for detecting a hidden node in a wireless local area network having a first station, a second station, and an access point. The first station can send a message, where the message can be sent as a data frame. After receiving the message, the access point can send the message to the second station. The second station can receive the message from the access point. In response to receiving the message, the second station can send an acknowledgement to the access point, where the acknowledgement can be sent as a control frame. The first station can monitor for the acknowledgement sent from the second station to the access point.

Claims

1. A method of detecting a hidden node in a wireless local area network having a first station and a second station both associated with an access point, the method comprising:

sending a message from the first station,

wherein the message is sent as a data frame;

receiving the message at the access point;

sending the message from the access point to the second station;

receiving the message from the access point at the second station;

sending an acknowledgement from the second station to the access point in response to receiving the message at the second station,

wherein the acknowledgement is sent as a control frame; and

monitoring at the first station for the acknowledgement sent from the second station to the access point.

2. The method of claim 1, further comprising determining that the second station is a hidden node of the first station if the first station fails to detect the acknowledgement.

3. The method of claim 1, further comprising determining that the second station is not a hidden node of the first station if the first station detects the acknowledgement.

4. The method of claim 1, further comprising:

sending an acknowledgement from the access point to the first station in response to receiving the message at the access point,

wherein the acknowledgement is sent from the access point to the first station as a control frame;

receiving the acknowledgement sent from the access point at the first station.

5. The method of claim 1, further comprising resending the message from the first station if the first station fails to receive an acknowledgement from the access point for the message within a specified period of time.

6. The method of claim 1, wherein the message includes a header having a destination address set to the second station, a BSSID set to the access point, and a source address set to the first station.

7. The method of claim 1, wherein the data frame and the control frame are sent and received below a network layer in an OSI model.

8. The method of claim 1, wherein the data frame and the control frame are sent at a data link layer of an OSI model according to the IEEE 802.11 standard.

9. The method of claim 1,

wherein the data frame is at least 29 bytes in length,

wherein the control frame is at most 20 bytes in length, and

wherein the acknowledgement is 14 bytes in length.

10. The method of claim 1, wherein the first station is a diagnostic tool.

11. The method of claim 1, wherein the first station is an administrative tool.

12. The method of claim 1, further comprising:

repetitively sending messages from the first station,

wherein the messages are sent as a data frames; and

monitoring at the first station for acknowledgements sent from the second station to the access point,

wherein the acknowledgements are sent as control frames.

13. The method of claim 12, further comprising determining that the second station is not a hidden node of the first station if the first station detects at least one acknowledgement sent from the second station to the access point.

14. The method of claim 12, further comprising determining that the second station is a hidden node of the first station if the first station fails to detect at least one acknowledgement sent from the second station to the access point.

15. A method of detecting a hidden node in a wireless local area network having a first station and a second station both associated with an access point, the method comprising:

sending a message from the first station to the second station through the access point,

wherein the message is sent as a data frame; and

monitoring at the first station for an acknowledgement sent from the second station to the access point,

wherein the acknowledgement is sent by the second station in response to receiving the message from the access point,

wherein the acknowledgement is sent as a control frame.

16. The method of claim 15, further comprising determining that the second station is a hidden node of the first station if the first station fails to detect the acknowledgement.

17. The method of claim 15, further comprising determining that the second station is not a hidden node of the first station if the first station detects the acknowledgement.

18. The method of claim 15, further comprising:

receiving an acknowledgement at the first station from the access point,

wherein the acknowledgement is sent by the access point in response to receiving the message from the first station,

wherein the acknowledgement is sent as a control frame.

19. The method of claim 15, further comprising resending the message from the first station if the first station fails to receive an acknowledgement from the access point for the message within a specified period of time.

20. The method of claim 15, wherein the message includes a header having a destination address set to the second station, a BSSID set to the access point, and a source address set to the first station.

21. The method of claim 15, wherein the data frame and the control frame are sent and received below a network layer in an OSI model.

22. The method of claim 15, wherein the data frame and the control frame are sent at a data link layer of an OSI model according to the IEEE 802.11 standard.

23. The method of claim 15,

wherein the data frame is at least 29 bytes in length,

wherein the control frame is at most 20 bytes in length, and

wherein the acknowledgement is 14 bytes in length.

24. The method of claim 15, wherein the first station is a diagnostic tool.

25. The method of claim 15, wherein the first station is an administrative tool.

26. The method of claim 15, further comprising:

repetitively sending messages from the first station,

wherein the messages are sent as a data frames; and

monitoring at the first station for acknowledgements sent from the second station to the access point,

wherein the acknowledgements are sent as control frames.

27. The method of claim 26, further comprising determining that the second station is not a hidden node of the first station if the first station detects at least one acknowledgement sent from the second station to the access point.

28. The method of claim 26, further comprising determining that the second station is a hidden node of the first station if the first station fails to detect at least one acknowledgement sent from the second station to the access point.

29. A method of detecting a hidden node in a wireless local area network having a first station, a second station, and an access point, the method comprising:

sending a message from the access point to the second station,

wherein the message is sent as a data frame;

receiving the message from the access point at the second station;

sending an acknowledgement from the second station to the access point in response to receiving the message at the second station,

wherein the acknowledgement is sent as a control frame;

detecting the message sent from the access point at the first station; and

monitoring at the first station for the acknowledgement sent from the second station to the access point.

30. The method of claim 29, further comprising determining that the second station is a hidden node of the first station if the first station fails to detect the acknowledgement.

31. The method of claim 29, further comprising determining that the second station is not a hidden node of the first station if the first station detects the acknowledgement.

32. The method of claim 29, further comprising:

sending a message from the first station to the second station through the access point,

wherein the message is sent as a data frame; and

monitoring at the first station for an acknowledgement sent from the second station to the access point,

wherein the acknowledgement is sent by the second station in response to receiving the message from the access point,

wherein the acknowledgement is sent as a control frame.

33. The method of claim 29, wherein the data frame and the control frame are sent and received below a network layer in an OSI model.

34. The method of claim 29, wherein the data frame and the control frame are sent at a data link layer of an OSI model according to the IEEE 802.11 standard.

35. The method of claim 29,

wherein the data frame is at least 29 bytes in length,

wherein the control frame is at most 20 bytes in length, and

wherein the acknowledgement is 14 bytes in length.

36. The method of claim 29, wherein the first station is a diagnostic tool.

37. The method of claim 29, wherein the first station is an administrative tool.

38. A system for detecting a hidden node in a wireless local area network comprising:

a first station configured to;

send a message,

monitor for an acknowledgement sent from a second station to an access point;

an access point configured to;

receive a message from the first station,

send a message received from the first station to a second station;

a second station configured to;

receive a message sent from the access point,

send an acknowledgement to the access point in response to receiving a message from the access point;

wherein the acknowledgement is sent as a control frame; and

wherein the message is sent as a data frame.

39. The system of claim 38, wherein the first station is further configured to determine that the second station is a hidden node of the first station if the first station fails to detect the acknowledgement.

40. The system of claim 38, wherein the first station is further configured to determine that the second station is not a hidden node of the first station if the first station detects the acknowledgement.

41. The system of claim 38,

wherein the access point is further configured to send an acknowledgement to the first station in response to receiving a message from the first station, and

wherein the first station is further configured to receive an acknowledgement sent from the access point.

42. The system of claim 41, wherein the first station is further configured to resend a message if the first station fails to receive an acknowledgement from the access point for the message within a specified period of time.

43. The system of claim 38, wherein the message includes a header having a destination address set to the second station, a BSSID set to the access point, and a source address set to the first station.

44. The method of claim 38, wherein the data frame and the control frame are sent and received below a network layer in an OSI model.

45. The system of claim 38, wherein the data frame and the control frame are sent at a data link layer of an OSI model according to the IEEE 802.11 standard.

46. The system of claim 38,

wherein the data frame is at least 29 bytes in length,

wherein the control frame is at most 20 bytes in length, and

wherein the acknowledgement is 14 bytes in length.

47. The system of claim 38, wherein the first station is a diagnostic tool.

48. The system of claim 38, wherein the first station is an administrative tool.

49. The system of claim 38, wherein the first station is further configured to:

repetitively send messages,

wherein the messages are sent as a data frames; and

monitor for acknowledgements sent from the second station to the access point,

wherein the acknowledgements are sent as control frames.

50. The method of claim 49, wherein the first station is further configured to determine that the second station is not a hidden node of the first station if the first station detects at least one acknowledgement sent from the second station to the access point.

51. The method of claim 49, wherein the first station is further configured to determine that the second station is a hidden node of the first station if the first station fails to detect at least one acknowledgement sent from the second station to the access point.

52. A computer readable medium comprising computer code for detecting a hidden node in a wireless local area network having a first station and a second station both associated with an access point, the computer readable medium comprising:

computer code for sending a message from the first station to the second station through the access point,

wherein the message is sent as a data frame; and

computer code for monitoring at the first station for an acknowledgement sent from the second station to the access point,

wherein the acknowledgement is sent by the second station in response to receiving the message from the access point,

wherein the acknowledgement is sent as a control frame.

53. The computer readable medium of claim 52, further comprising computer code for determining that the second station is a hidden node of the first station if the first station fails to detect the acknowledgement.

54. The computer readable medium of claim 52, further comprising computer code for determining that the second station is not a hidden node of the first station if the first station detects the acknowledgement.

55. The computer readable medium of claim 52, further comprising computer code for resending the message from the first station if the first station fails to receive an acknowledgement from the access point for the message within a specified period of time.

56. The computer readable medium of claim 52, wherein the message includes a header having a destination address set to the second station, a BSSID set to the access point, and a source address set to the first station.

57. The computer readable medium of claim 52, wherein the data frame and the control frame are sent and received below a network layer in an OSI model.

58. The computer readable medium of claim 52, wherein the data frame and the control frame are sent at a data link layer of an OSI model according to the IEEE 802.11 standard.

59. The computer readable medium of claim 52,

wherein the data frame is at least 29 bytes in length,

wherein the control frame is at most 20 bytes in length, and

wherein the acknowledgement is 14 bytes in length.

60. The computer readable medium of claim 52, wherein the first station is a diagnostic tool.

61. The computer readable medium of claim 52, wherein the first station is an administrative tool.

62. The computer readable medium of claim 52, further comprising:

computer code for repetitively sending messages from the first station,

wherein the messages are sent as a data frames; and

computer code for monitoring at the first station for acknowledgements sent from the second station to the access point,

wherein the acknowledgements are sent as control frames.

63. The computer readable medium of claim 62, further comprising computer code for determining that the second station is not a hidden node of the first station if the first station detects at least one acknowledgement sent from the second station to the access point.

64. The method of claim 62, further comprising computer code for determining that the second station is a hidden node of the first station if the first station fails to detect at least one acknowledgement sent from the second station to the access point.