Method for determining DFS channel availability in a wireless LAN

• US 7,813,744 B2
• Filed: 08/31/2006
• Issued: 10/12/2010
• Est. Priority Date: 08/31/2006
• Status: Expired due to Fees

• Current Assignee: Spectralink Corporation (Mobile Devices Holdings LLC)
• Original Assignee: Polycom Incorporated (HP Inc.)
• Inventors: Johnson, Paul D.
• Primary Examiner(s): MIZRAHI, DIANE D
• Application Number:
  US11/513,763
• Publication Number:
  US 20080056200A1
• Time in Patent Office: 1,503 Days
• Field of Search: 455/1, 455/414, 455/3.03, 455/3.04, 455/456.3, 455/463.1, 455/464, 455/509, 455/529, 370/208, 370/211, 370/312, 370328-350, 370/432
• US Class Current: 455/464
• 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 radar signal, a method for the wireless communications device to determine an availability of the at least one channel shared with the radar signal comprising the steps of:

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

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

the wireless communications device transmitting at least one probe signal on the channel over which the qualified transmission was received only while the timer dedicated to the channel has not expired; and

the at least one wireless communications device receiving a probe response signal to the at least one transmitted probe signal on the channel over which the qualified transmission was received, using the probe response signal to reset the timer dedicated to the channel and to measure and store an indication of a signal quality associated with the channel;

the wireless communications device transitioning into the call state, transmitting an association request to the at least one access point over the channel and the wireless communications device receiving an association response from the at least one access point over the channel; and

the wireless communications device establishing a communications session with the at least one access point over the channel only during the time that the timer dedicated to the channel has not expired.

2. The method of claim 1 wherein the wireless communications device senses the wireless medium for at least one dynamic channel access cycle.

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

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

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

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

7. 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 radar signal, a method for at least one of the wireless communications devices to determine availability of at least one of the plurality of the channels shared with the radar signal for communicating with at least one of the plural access points comprising:

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

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

the wireless communications device transmitting at least one probe signal on the channel over which the qualified transmission was received only while the timer dedicated to the channel has not expired;

the wireless communications device receiving a probe signal to the transmitted at least one probe signal on the channel over which the qualified transmission was received, using the probe response signal to reset the timer dedicated to the channel and to measure and store 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 on the channel over which the qualified transmission was received;

the wireless communications device receiving an association response from the at least one access point over the channel over which the qualified transmission was received; and

the wireless communications device establishing a communications session with the at least one access point over the channel over which the qualified transmission was received only during the time that the timer dedicated to the channel has not expired.

8. The method of claim 7 wherein the wireless communications device senses the wireless medium for at least one dynamic channel access cycle.

9. The method of claim 7 wherein the indication of signal quality is one or both of a measured signal strength and a measured bit error rate.

10. The method of claim 7 wherein the wireless communications device is a mobile phone.

11. The method of claim 7 wherein the qualified transmission one of a beacon and a directed packet.

12. 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 radar signal and at least one channel not shared with a radar signal method for the wireless communications device selecting a channel over which to communicate with the access point comprising the steps of:

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

the wireless communications device radar priority signal and setting a timer dedicated to the channel;

the wireless communications device transmitting at least one probe signal on the channel over which the qualified transmission was received only while the timer has not expired and transmitting at least one probe signal on a channel not shared with a radar signal;

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

13. The method of claim 12 wherein the wireless communications device senses the wireless medium for at least one dynamic channel access cycle.

14. The method of claim 12 wherein the indication of signal quality is one or both of a measured signal strength and a measured bit error rate.

15. The method of claim 12 wherein the higher priority signal is a radar signal.

16. The method of claim 12 wherein the wireless communications device is a mobile phone.

17. The method of claim 12 wherein the qualified transmission is one of a beacon and a directed packet.