System and Method for Active Scanning in Multi-channel Wi-Fi System

• US 20140010089A1
• Filed: 07/05/2013
• Published: 01/09/2014
• Est. Priority Date: 07/06/2012
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Cai, Lin, Chen, Bin
• Granted Patent: US 9,210,652 B2
• Time in Patent Office: Days
• US Class Current: 370/241
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

It is possible to shorten channel monitoring periods of unoccupied channels during Wi-Fi discovery by verifying whether or not a message indicating the presence of a Wi-Fi AP has been detected prior to the probe timer reaching a medium channel time (MedChannelTime). For example, STAs detecting some channel activity during the clear channel assessment may nevertheless discontinue monitoring a Wi-Fi Channel when no messages indicating the presence of a Wi-Fi AP are detected prior to expiration of the MedChannelTime. Messages indicating the presence of a Wi-Fi AP may include any Wi-Fi messages sent from or destined for a Wi-Fi AP, while excluding probe requests and non-Wi-Fi messages.

Claims

1. A method for actively scanning a Wi-Fi network, the method comprising:

sending, by a station (STA), a probe request message over a first channel in a multi-channel wireless local area network (WLAN);

monitoring, by the STA, the first channel for probe response messages;

setting, by the STA, a probe timer;

detecting, by the STA, at least some channel activity prior to the probe timer reaching a minimum channel time (MinChannelTime);

discontinue monitoring, by the STA, of the first channel when the probe timer reaches a medium channel time (MedChannelTime) unless a message indicating the presence of a Wi-Fi access point (AP) is detected on the first channel prior to the probe timer reaching the MedChannelTime; and

monitoring, by the STA, the first channel until the probe timer reaches a maximum channel time (MaxChannelTime) when at least one message indicating the presence of a Wi-Fi AP is detected on the first channel prior to expiration of the MedChannelTime.

2. The method of claim 1, wherein the MedChannelTime is longer than or equal to the MinChannelTime but shorter than or equal to the MaxChannelTime.

3. The method of claim 1, wherein the MedChannelTime is equal to the MinChannelTime but shorter than or equal to the MaxChannelTime.

4. The method of claim 1, wherein messages indicating the presence of a Wi-Fi AP include Wi-Fi data frames and Wi-Fi control frames.

5. The method of claim 4, wherein messages indicating the presence of a Wi-Fi AP include Wi-Fi management frames that are not Wi-Fi probe requests.

6. The method of claim 4, wherein messages indicating the presence of a Wi-Fi AP exclude probe request messages transmitted by mobile stations.

7. The method of claim 4, wherein messages indicating the presence of a Wi-Fi AP exclude messages transmitted by stations operating in an independent basic service set (IBSS) mode.

8. The method of claim 4, wherein messages indicating the presence of a Wi-Fi AP exclude device-to-device (D2D) messages.

9. The method of claim 1, wherein detecting at least some channel activity prior to expiration of the MinChannelTime comprises:

detecting a physical channel clear channel assessment (PHY-CCA) indication (busy) primitive prior to the probe timer reaching the MinChannelTime.

10. The method of claim 1, wherein the STA is a mobile station.

11. The method of claim 1, wherein the STA is an access point.

12. A station (STA) comprising:

a processor; and

a computer readable storage medium storing programming for execution by the processor, the programming including instructions to;

send a probe request message over a first channel in a multi-channel wireless local area network (WLAN); and

monitor the first channel for probe response messages;

set a probe timer;

detect at least some channel activity prior to the probe timer reaching a minimum channel time (MinChannelTime);

cease monitoring the first channel when the probe timer reaches a medium channel time (MedChannelTime) unless a message indicating the presence of a Wi-Fi access point (AP) is detected on the first channel prior to the probe timer reaching the MedChannelTime; and

monitor the first channel until the probe timer reaches a maximum channel time (MaxChannelTime) if at least one message indicating the presence of a Wi-Fi AP is detected on the first channel prior to expiration of the MedChannelTime.

13. The STA of claim 12, wherein the MedChannelTime is longer than or equal to the MinChannelTime but shorter than or equal to the MaxChannelTime.

14. The STA of claim 12, wherein the MedChannelTime is equal to the MinChannelTime but shorter than the MaxChannelTime.

15. The STA of claim 12, wherein messages indicating the presence of a Wi-Fi AP include Wi-Fi data frames and Wi-Fi control frames.

16. The STA of claim 15, wherein messages indicating the presence of a Wi-Fi AP include Wi-Fi management frames that are not Wi-Fi probe requests.

17. The STA of claim 15, wherein messages indicating the presence of a Wi-Fi AP exclude probe request messages transmitted by mobile stations.

18. The STA of claim 15, wherein messages indicating the presence of a Wi-Fi AP exclude messages transmitted by stations operating in an independent basic service set (IBSS) mode.

19. The STA of claim 15, wherein messages indicating the presence of a Wi-Fi AP exclude device-to-device (D2D) messages.

20. The STA of claim 12, wherein the instructions to detect at least some channel activity prior to expiration of the MinChannelTime include instructions to:

detect a physical channel clear channel assessment (PHY-CCA) indication (busy) primitive prior to the probe timer reaching the MinChannelTime.

21. A method for actively scanning a Wi-Fi network, the method comprising:

sending, by a station (STA), a probe request over a channel in a multi-channel wireless local area network (WLAN);

starting a probe timer;

detecting a physical channel clear channel assessment indication (PHY-CCA.indication) (busy) primitive before the probe timer reaches a minimal channel time (MinChannelTime);

setting a network allocation vector (NAV) to zero and scanning a next channel in the multi-channel WLAN if all frames detected before the probe timer reaches the MinChannelTime are probe request frames; and

monitoring the channel for probe response messages until the probe timer reaches a maximum channel time (MaxChannelTime) if at least one frame that is not a probe request frame is detected before the probe timer reaches the MinChannelTime.

22. The method of claim 21, further comprising:

processing all received probe responses when the probe timer reaches the MaxChannelTime.