Method for determining DFS channel availability in a wireless LAN

• US 20080056200A1
• Filed: 08/31/2006
• Published: 03/06/2008
• Est. Priority Date: 08/31/2006
• Status: Active Grant

• Current Assignee: Spectralink Corporation (Mobile Devices Holdings LLC)
• Original Assignee: Spectralink Corporation (Mobile Devices Holdings LLC)
• Inventors: Johnson, Paul D.
• Granted Patent: US 7,813,744 B2
• Time in Patent Office: Days
• US Class Current: 370/333
• CPC Class Codes: H04W 36/0085 Hand-off measurements

Abstract

A LAN has a wireless portion which includes access points and wireless communications devices and a wired portion which includes such things as routers, servers, and a PBX. The LAN operates in a radio frequency band where certain channels (DFS channels) are shared with a signal that is of higher priority than the communications signals transmitted and received by the access point and the wireless communications devices. If a higher priority signal is sensed on a particular channel of the wireless medium by a master device, it is necessary for all of the slave devices communicating on this channel to stop transmitting on that channel within a short period of time. The wireless communications devices are mobile and can be easily transported around in space or roam during a communications session. While roaming during a communications session, it is likely that the communications device will move out of range of an access point with which it is currently associated and possibly cause the session to end prematurely, and so it is important that a handoff procedure operates so that a communications session is continuous as the communications device roams from access point to access point. By setting and maintaining a timer dedicated to each available DFS channel, it is possible to ensure that the communications sessions is not interrupted during the roaming process in an environment were certain channels are shared with a higher priority signal.

Claims

1. In a wireless local area communications network comprised of at least one access point for communicating with a wireless communications device over at least one channel shared with a higher priority signal, a method for the wireless communications device to determine an availability of the at least one channel shared with the higher priority signal comprising the steps of:

turning on the wireless communications device;

the wireless communications device sensing the wireless medium on at least one of the channels shared with the higher priority signal for a qualified transmission;

the wireless communications device receiving a qualified transmission over one of the channels shared with the higher priority signal and setting a timer dedicated to the channel;

the wireless communications device transmitting at least one signal over the channel;

the at least one wireless communications device receiving a response to the transmitted signal over the channel, using the response to reset the timer dedicated to the channel and measuring and storing an indication of the signal quality associated with the channel.

2. The wireless communications device of claim 1 senses the wireless medium for at least one DCA cycle.

3. The indication of signal quality of claim 1 is one or both of a measured signal strength and a measured packet error rate.

4. The higher priority signal of claim 1 is a radar signal.

5. The wireless communications device of claim 1 is a mobile phone.

6. The qualified transmission of claim 1 is one of a beacon and a directed packet.

7. The method of claim 1 further comprising:

the wireless communications device transitioning into the call state;

the wireless communications device transmitting an association request to the at least one access point over a channel with the highest stored indication of signal quality;

the wireless communications device receiving an association response from the at least one access point over the channel with the highest stored indication of signal quality; and

the wireless communications device establishing a communications session with the at least one access point over the channel with the highest stored indication of signal quality.

8. In a wireless local area communications network comprised of a plurality of access points for communicating with a plurality of wireless communications devices over a plurality of channels each shared with a higher priority signal, a method for at least one of the wireless communications devices to determine availability of at least one of the plural channels shared with the higher priority signal for communicating with at least one of the plural access points comprising:

turning on the wireless communications device;

the wireless communications device sensing the wireless medium on at least one of the channels shared with the higher priority signal for a qualified transmission;

the wireless communications device receiving a qualified transmission over one of the channels shared with the higher priority signal and setting a timer dedicated to the channel;

the wireless communications device transmitting at least one signal over the channel;

the wireless communications device receiving a response to the transmitted signal over the channel, using the response to reset the timer dedicated to the channel and measuring and storing an indication of the signal quality associated with the channel. the wireless communications device transitioning into the call state;

the wireless communications device transmitting an association request to at least one of the plural access points over a channel with the highest stored indication of signal quality;

the wireless communications device receiving an association response from the at least one access point over the channel with the highest stored indication of signal quality; and

the wireless communications device establishing a communications session with the at least one access point over the channel with the highest stored indication of signal quality.

9. The wireless communications device of claim 8 senses the wireless medium for at least one DCA cycle.

10. The indication of signal quality of claim 8 is one or both of a measured signal strength and a measured bit error rate.

11. The higher priority signal of claim 8 is a radar signal.

12. The wireless communications device of claim 8 is a mobile phone.

13. The qualified transmission of claim 8 is one of a beacon and a directed packet.

14. In a wireless local area communications network comprised of at least one access point for communicating with a wireless communications device over at least one channel shared with a higher priority signal and at least one channel not shared with a higher priority signal, a method for the wireless communications device selecting a channel over which to communicate with the access point comprising the steps of:

turning on the wireless communications device;

the wireless communications device sensing the wireless medium on at least one of the channels shared with the higher priority signal for a qualified transmission;

the wireless communications device receiving a qualified transmission over one of the channels shared with the higher priority signal and setting a timer dedicated to the channel;

the wireless communications device transmitting at least one signal on the channel over which the qualified transmission was received and transmitting at least one signal on a channel not shared with a higher priority signal;

the at least one wireless communications device receiving a response to the transmitted signals over the channel shared with the higher priority signal and the channel not shared with the higher priority signal, using the response to reset the timer dedicated to the channel shared with the higher priority signal and measuring and storing an indication of the signal quality associated with both the channel shared with the higher priority signal and the channel not shared with the higher priority signal;

the wireless communications device transitioning into the call state;

the wireless communications device transmitting an association request to at least one of the plural access points over a channel with the highest stored indication of signal quality;

the wireless communications device receiving an association response from the at least one access point over the channel with the highest stored indication of signal quality; and

the wireless communications device establishing a communications session with the at least one access point over the channel with the highest stored indication of signal quality.

15. The wireless communications device of claim 14 senses the wireless medium for at least one DCA cycle.

16. The indication of signal quality of claim 14 is one or both of a measured signal strength and a measured bit error rate.

17. The higher priority signal of claim 14 is a radar signal.

18. The wireless communications device of claim 14 is a mobile phone.

19. The qualified transmission of claim 14 is one of a beacon and a directed packet.