Symmetric transmit opportunity (TXOP) truncation

• US 8,031,661 B2
• Filed: 01/10/2007
• Issued: 10/04/2011
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Intellectual Ventures I LLC (Intellectual Ventures LLC)
• Original Assignee: Intellectual Ventures I LLC (Intellectual Ventures LLC)
• Inventors: Wentink, Menzo
• Primary Examiner(s): Chang; Kent
• Assistant Examiner(s): Siddiqui; Kashif
• Application Number:
  US11/651,879
• Publication Number:
  US 20070115882A1
• Time in Patent Office: 1,728 Days
• Field of Search: 370229-240, 370/252, 370328-338, 455450-454
• US Class Current: 370/329
• CPC Class Codes: H04N 21/4126 The peripheral being portable, e.g. PDAs or mobile phones
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 28/12 using signalling between network elements
• CPC Class Codes: H04W 74/08 Non-scheduled access, e.g. ALOHA hybrid access H04W74/02
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 74/0866 using a dedicated channel for access
• CPC Class Codes: H04W 74/0891 for synchronized access
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface

Abstract

Symmetric transmit opportunity (TXOP) truncation (STT) including receiving a frame that truncates a TXOP around a first station, and responsive to receiving the frame, sending a second frame that truncates the TXOP around a second station. By transmitting a second frame that repeats the truncation of the TXOP transmitted from the first station, a hidden node problem can be avoided and equitable access to the medium provided by ensuring that stations that may be outside the broadcast range of the first station also receive the frame truncating the TXOP. Also disclosed is an access point (AP) that receives an extended interframe space (EIFS) set frame responsively transmits a second frame having a completed transmission corresponding to time based on an interval of EIFS less DIFS, the interval commencing from an end of the EIFS set frame.

Claims

1. A symmetric transmit opportunity (TXOP) truncation method, comprising:

transmitting, from an access point and to a terminal, a final data frame of a plurality of data frames, wherein the final data frame includes an identifier that signals the terminal to respond with a truncation frame;

receiving an acknowledgment from the terminal at the access point;

receiving, at the access point, a first truncation frame from the terminal, wherein the first truncation frame is configured to truncate an existing TXOP around the terminal, wherein the first truncation frame is distinct from the acknowledgment; and

transmitting, from the access point and in response to receiving the first truncation frame, a second truncation frame, wherein the second truncation frame is configured to truncate the TXOP around the access point.

2. The method of claim 1, wherein the first and second truncation frames comprise CF-end frames.

3. The method of claim 2, wherein the first truncation frame contains an address of the access point.

4. The method of claim 3, wherein the address of the access point is contained in a basic service set identification (BSSID) field of the first truncation frame.

5. The method of claim 1, wherein the second truncation frame comprises a CF-end frame that contains an address of the terminal, the access point, or a third station in a basic service set identification (BSSID) field of the second frame.

6. The method of claim 1, wherein the second truncation frame contains an address of the access point.

7. The method of claim 1, wherein a BSSID field of the second truncation frame contains an address of a third station, and further comprising receiving the second truncation frame at the third station.

8. The method of claim 7, further comprising, in response to receiving the second truncation frame at the third station, the third station transmitting a third truncation frame, wherein the third truncation frame is configured to truncate the TXOP around the third station.

9. The method of claim 8, wherein a BSSID field of the third truncation frame contains an address of the third station.

10. The method of claim 1, wherein the second truncation frame is transmitted after a short interframe space (SIFS) interval or a PCF interframe space (PIFS) interval.

11. The method of claim 2, wherein the second truncation frame is transmitted within a NAV duration value set by the first truncation frame.

12. The method of claim 1, wherein the first truncation frame has a physical layer convergence protocol duration substantially equal to a duration of the first truncation frame plus a short interframe space (SIFS) interval plus an expected duration of the second truncation frame.

19. The method of claim 1, wherein the first truncation frame is sent at a non-basic rate.

26. The method of claim 1, wherein the first truncation frame and the second truncation frame each contain a basic service set identification (BSSID) field.

27. The method of claim 26, wherein the BSSID fields of the first and second truncation frames both include a MAC address of at least one of the terminal and access point.

13. An access point comprising:

a processor; and

a memory having instructions stored thereon that, if executed by the processor, cause the access point to

transmit a final data frame of a plurality of data frames to a terminal, wherein the final data frame includes an identifier that signals the terminal to respond with a truncation frame;

receive an acknowledgment from the terminal;

receive a first truncation frame from the terminal, wherein the first truncation frame is configured to truncate an existing TXOP around the terminal, wherein the first truncation frame is distinct from the acknowledgment; and

transmit, in response to receiving the first truncation frame, a second truncation frame, wherein the second truncation frame is configured to truncate the TXOP around the access point.

14. The access point of claim 13, wherein the first and second truncation frames comprise CF-end frames.

15. The access point of claim 13, wherein the first truncation frame includes an address of the access point.

16. The access point of claim 13, wherein the second truncation frame is addressed to the terminal, the access point, or a third station.

17. The access point of claim 13, wherein the second truncation frame comprises an address of the terminal, an address of the access point, or an address of a third station in a basic service set identification (BSSID) field of the second truncation frame.

20. The access point of claim 13, wherein the first truncation frame is sent at a non-basic rate.

28. The access point of claim 13, wherein the first truncation frame and the second truncation frame each contain a basic service set identification (BSSID) field.

29. The access point of claim 28, wherein the BSSID fields of the first and second truncation frames both include a MAC address of at least one of the terminal and access point.

18. An article of manufacture including a non-transitory computer-readable medium having instructions stored thereon comprising:

instructions for transmitting, from an access point and to a terminal, a final data frame of a plurality of data frames, wherein the final data frame includes an identifier that signals the terminal to respond with a truncation frame;

instructions for receiving an acknowledgment from the terminal at the access point;

instructions for receiving, at the access point, a first truncation frame from the terminal, wherein the first truncation frame is configured to truncate an existing TXOP around the terminal, wherein the first truncation frame is distinct from the acknowledgment; and

instructions for transmitting, from the access point and in response to receiving the first truncation frame, a second truncation frame, wherein the second truncation frame is configured to truncate the TXOP around the access point.

21. The article of manufacture of claim 18, wherein the first truncation frame is sent at a non-basic rate.

22. The article of manufacture of claim 18, wherein the first and second truncation frames comprise CF-end frames.

23. The article of manufacture of claim 18, wherein the first truncation frame includes an address of the access point.

24. The article of manufacture of claim 18, wherein the second truncation frame is addressed to the terminal, the access point, or a third station.

25. The article of manufacture of claim 18, wherein the second truncation frame comprises an address of the terminal, an address of the access point, or an address of a third station in a basic service set identification (BSSID) field of the second truncation frame.

30. The article of manufacture of claim 18, wherein the first truncation frame and the second truncation frame each contain a basic service set identification (BSSID) field.

31. The article of manufacture of claim 30, wherein the BSSID fields of the first and second truncation frames both include a MAC address of at least one of the terminal and access point.