Access point channel forecasting for seamless station association transition
Seamless migration of an AP/STA link across channels to compensate for a changing RF environment is achieved by forecasting alternate AP communication channels to an STA prior to loss of connectivity on the link. The AP, when identifying a preferred communication channel, also identifies an alternate communication channel, and communicates this alternate channel to a coupled STA. In the event that communication between the AP and the STA is lost, the STA can quickly predict the new location of the AP, and migrate to the new channel without loss of communication state. The AP is not required to communicate to any STA that it has switched stations. Rather, the fact that the AP has switched is inferred at the STA by the inability of the STA to communicate with the AP. Thus the present invention may be used to preserve link state when a communication channel used by the AP/STA link is blocked.
1 . A method for maintaining an association with a station by an access point in a wireless network comprising the steps of:
selecting a first channel and at least one alternate channel for transmissions by the access point;
storing, in a channel forecast table, the at least one alternate channel;
forwarding the channel forecast table to the station;
detecting a loss of availability of the first channel; and
initiating communications on the alternate channel without notice to other devices in the network.
2 . The method according to claim 1 , further comprising the step of:
transmitting a first portion of a data sequence to the station on the first channel; and
transmitting a second portion of the data sequence to the station on the alternate channel.
3 . The method according to claim 1 , wherein the step of forwarding the channel forecast table is performed at initialization of the access point.
4 . The method according to claim 1 , further comprising the steps of:
scanning channels to identify desirable transmission channels;
updating the channel forecast table to include the desirable transmission channels; and
transmitting the updated channel forecast table to the station.
5 . The method according to claim 1 further including the steps of:
receiving an indication from the station regarding an ability of the station to utilize the channel forecast table; and
selectively storing state for the station in response to the received indication.
6 . A network device for use as an access point in a wireless network comprising:
channel selection means for selecting a first channel and at least one alternate channel for transmissions;
a channel forecast table for storing the at least one alternate channel; and
forwarding means for forwarding the channel forecast table associated stations.
7 . The network device of claim 6 further comprising:
a channel migration group table for storing identifiers of stations in the wireless network capable of seamlessly transitioning with the access point from the first channel to the at least one alternate channel.
8 . A method of maintaining an association with an access point by a station in a wireless network including the steps of:
receiving, from the access point, a channel forecast table including at least one alternate transmission channel;
communicating with the access point on a first channel; and
upon a detection of a loss of transmissions by the access point on the first channel, switching to the at least one alternate transmission channel.
9 . The method of claim 8 wherein the channel forecast table is received at initial association with the access point.
10 . The method of claim 8 further comprising the steps of periodically receiving updates to the channel forecast table and updating the channel forecast table responsive to the updates.
11 . The method of claim 8 including the step of indicating to the access point that the station is capable of seamlessly transitioning to the alternate channel with the access point.
12 . The method according to claim 8 including the steps of:
determining whether the access point is at the first one of the at least one alternate channels in the channel forecast table; and
responsive to a determination that the access point is not at the first one of the at least one alternate channels in the channel forecast table, cycling through the channel forecast table a predetermined number of times to locate the access point.
13 . The method according to claim 12 , further including the step of attempting to locate an alternative access point responsive to failure to locate the access point at any of the first channel or alternate channels in the channel forecast table.
14 . A network device including:
means for establishing communications with an access point in a wireless network on a first channel;
a channel forecast table, storing at least one alternate channel for communications with the access point;
means for detecting a loss of connectivity with the access point; and
means for switching to the alternate channel to locate the access point.