Collision avoidance in IEEE 802.11 contention free period (CFP) with overlapping basic service sets (BSSs)

• US 20020071448A1
• Filed: 06/30/2001
• Published: 06/13/2002
• Est. Priority Date: 07/07/2000
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Choi, Sunghyun, Cervello, Gerard
• Granted Patent: US 7,054,329 B2
• Time in Patent Office: Days
• US Class Current: 370/445
• CPC Class Codes: H04W 74/0816 with collision avoidance
• CPC Class Codes: H04W 80/02 Data link layer protocols
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/10 adapted for operation in multiple networks, e.g. multi-mode access points

Abstract

A medium access control (MAC) protocol is provided for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs). The MAC protocol includes hardware/software for utilizing ready-to-send(RTS)/clear-to-send(CTS) exchange during CFPs to avoid potential collision from STAs in overlapping BSSs and hardware/software for providing overlapping network allocation vectors (ONAV) in addition to a network allocation vector (NAV), the ONAV included to facilitate the effectiveness of the RTS/CTS during CFPs.

Claims

1. A medium access control (MAC) protocol for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs), comprising:

means for utilizing ready-to-send-(RTS)/clear-to-send(CTS) exchange during CFPs to avoid potential collision from STAs in overlapping BSSs; and

means for providing overlapping network allocation vectors (ONAV) in addition to a network allocation vector (NAV), the ONAV included to facilitate the effectiveness of the means for utilizing.

2. The MAC protocol defined by claim 1, further comprising means for updating the duration/ID of both the RTS and CTS frames during the CFP and maintaining that the overlapping STA(s) will not interfere with transmission between and STA and its corresponding AP following the RTS/CTS exchanges.

3. The MAC protocol defined by claim 2, wherein the means for updating the duration/ID of the RTS frame by adding the time length of the CTS to the (duration of the CF data minus the poll frame) and the duration of the CF-ACK, and for updating the duration/ID of the CTS frame by adding the duration/ID specified in the received RTS frame with the duration of the data and the time length if the CF-ACK and subtracting the duration time of the CTS from same.

4. The MAC protocol defined by claim 2, including means for determining if the RTS/CTS exchange is successful, and, if unsuccessful, deferring polling of the STA by its corresponding AP to a future time, where the AP then polls another STA.

5. The MAC protocol defined by claim 1, further comprising means for implementing ONAV rules.

6. The MAC protocol defined by claim 1, further comprising means for determining when to implement the RTS/CTS during CFP.

8. A wireless local area network (WLAN) which implements the MAC protocol defined in claim 1.

7. A method for implementing a medium access control (MAC) protocol for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs), the method comprising the steps:

utilizing ready-to-send-(RTS)/clear-to-send(CTS) exchange during CFPs to avoid potential collision from STAs in overlapping BSSs; and

providing overlapping network allocation vectors (ONAV) in addition to a network allocation vector (NAV), the ONAV included to facilitate the effectiveness of the Step of utilizing.

9. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for which define a medium access control (MAC) protocol for implementing a medium access control (MAC) protocol for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs), the method comprising the steps:

utilizing ready-to-send-(RTS)/clear-to-send(CTS) exchange during CFPs to avoid potential collision from STAs in overlapping BSSs; and

providing overlapping network allocation vectors (ONAV) in addition to a network allocation vector (NAV), the ONAV included to facilitate the effectiveness of the Step of utilizing.

10. A medium access control (MAC) protocol for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs), comprising:

means for utilizing ready-to-send-(RTS)/clear-to-send(CTS) exchange during CFPs to avoid potential collision from STAs in overlapping BSSs.

11. A medium access control (MAC) protocol for avoiding collisions from stations (STAs) comprising two or more IEEE 802.11 basic service sets (BSSs) collocated and operating in the same channel during contention free periods (CFPs), comprising:

means for providing overlapping network allocation vectors (ONAV) in addition to a network allocation vector (NAV), the ONAV included to facilitate the effectiveness said collision avoidance.