Pre-scan for wireless channel selection

• US 20070097940A1
• Filed: 11/03/2006
• Published: 05/03/2007
• Est. Priority Date: 11/03/2005
• Status: Active Grant

• Current Assignee: Xenogenic Development Limited Liability Company (Intellectual Ventures LLC)
• Original Assignee: Autocell Laboratories Incorporated
• Inventors: Yuen, Michael
• Granted Patent: US 8,411,616 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A pre-scan interval including three states is employed to synchronize access points and facilitate power control to facilitate initial channel selection where a group of nearby access point are contemporaneously initialized. In State 1 the access point is operable to transmit pre-scan frames which include device ID, and to listen for pre-scan frames transmitted by other access points. When a pre-scan frame is received, the received power level and device ID are noted and used to construct a table. The access point normally remains in State 1 until a minimum number of frame samples have been received from each access point that has been heard, and a minimum pre-scan time has elapsed. State 2 provides synchronization of transition of the access points between State 1 and State 3. When the access point is in State 2, it transmits pre-scan frames with a sync-mark bit set to indicate that the access point is in State 2. The access point continues to listen for pre-scan frames from other access points to determine whether those access points have transitioned to State 2, i.e., by reading the sync-mark bit in the received frames. The access point normally transitions to State 3 when all detected access points have transmitted pre-scan frames with the sync-mark bit set, i.e., when all detected access points have signaled readiness to move to State 3. In State 3 the access point begins a countdown to transition to the scan interval. While counting down, the access point transmits pre-scan frames which advertise the state of the countdown timer, and listens for pre-scan frames from other access points. If differences in the countdown state are detected then the access points re-synchronize by adopting the countdown state of the slowest clock.

Claims

1. A method executed by a first fixed location wireless device for improving initial channel selection in a wireless network where a plurality of fixed location wireless devices are contemporaneously initialized, comprising the steps of:

transmitting, on a predetermined channel, at least one message including an identifier of the first device;

transmitting, on the predetermined channel, at least one message indicative of readiness to transition to a subsequent step; and

commencing scanning for channel selection purposes.

2. The method of claim 1 wherein the subsequent step includes delaying transition to commencing scanning by a time indicated by a countdown timer.

3. The method of claim 2 including the further step of transmitting, on the predetermined channel, an indication of countdown timer state.

4. The method of claim 3 including the further step of receiving messages including device identifiers from other fixed location wireless devices.

5. The method of claim 4 wherein the step of transmitting at least one message indicative of readiness to transition to a subsequent step is not executed until (a) a minimum number of messages are received from each identified device, and (b) a predetermined minimum amount of time has elapsed.

6. The method of claim 3 wherein delaying transition to commencing scanning by a time indicated by a countdown timer is executed immediately if either (a) a predetermined maximum amount of time has elapsed, or (b) another fixed location wireless device has started a countdown timer to commencing scanning.

7. The method of claim 3 wherein, following transmitting the at least one message indicative of readiness to transition to a subsequent step, delaying transition to commencing scanning by a time indicated by a countdown timer is executed immediately if either (a) each identified device indicates readiness to begin a countdown timer to commencing scanning, or (b) a predetermined maximum amount of time has elapsed, or (c) another fixed location wireless device has stared a countdown timer to commencing scanning.

8. The method of claim 3 including the further step of adopting, as countdown timer state, a countdown timer state indicative of greatest amount of time remaining to transition to commencing scanning from countdown timer state advertisements from all detected fixed location wireless devices.

9. A first fixed location wireless device operable to facilitate initial channel selection in a wireless network where a plurality of fixed location wireless devices are contemporaneously initialized, comprising:

a transmitter operable to transmit, on a predetermined channel;

at least one message including an identifier of the first device, and

at least one message indicative of readiness to transition to a subsequent step; and

a receiver operable to commence scanning for channel selection purposes.

10. The device of claim 9 further including a countdown timer, and wherein the subsequent step includes delaying transition to commencing scanning by a time indicated by the countdown timer.

11. The device of claim 10 wherein the transmitter is further operable to transmit an indication of countdown timer state.

12. The device of claim 11 wherein the receiver is further operable to receive messages including device identifiers from other fixed location wireless devices.

13. The device of claim 12 wherein the transmitter does not transmit the at least one message indicative of readiness to transition to a subsequent step until (a) a minimum number of messages are received from each identified device, and (b) a predetermined minimum amount of time has elapsed.

14. The device of claim 11 further including circuitry operable to trigger commencement of the subsequent step if either (a) a predetermined maximum amount of time has elapsed, or (b) another fixed location wireless device has started a countdown timer to commencing scanning.

15. The device of claim 11 further including circuitry operable following transmission of the at least one message indicative of readiness to transition to a subsequent step, to trigger commencement of the subsequent step if either if either (a) each identified device indicates readiness to begin a countdown timer to commencing scanning, or (b) a predetermined maximum amount of time has elapsed, or (c) another fixed location wireless device has stared a countdown timer to commencing scanning.

16. The device of claim 11 further including circuitry operable to update the countdown timer state to be a countdown timer state indicative of greatest amount of time remaining to transition to commencing scanning from countdown timer state advertisements from all detected fixed location wireless devices.