Other

Hewlett-Packard Company

Hien Nguyen

Anil Gupta

Pierre Trudeau

Roger D Sands

Thomas S Stefanski

A fast roaming (handoff) service is provided for a WLAN infrastructure. A given mobile station (STA) obtains a pairwise master key (PMK) when it associates with an access point (AP) in the infrastructure. A neighbor graph identifies prospective APs to which the STA may then roam. At initialization, preferably the neighbor graph is fully-connected (i.e., each AP is assumed to be connected to every other AP). The PMK (obtained by the STA initially) is shared proactively with the neighbor APs as indicated in the neighbor graph. Thus, when the STA roams to a neighbor AP, because the PMK is already available, there is no requirement that the STA initiate a real-time request to an authentication server to re-associate to the new AP. Further, the new AP causes an update to the neighbor graph information implicitly by simply issuing a notification that it is now handling the STA that arrived from the prior AP; in this manner, the prior AP is confirmed as a neighbor, but there is no requirement for any inter-AP dialog before a given neighbor graph is updated. As roaming occurs the neighbor graph is pruned down (to reflect the actual neighbor AP connections) using the implicit notification data.

Fast roaming in a wireless network using per-STA pairwise master keys shared across participating access points

An automatic channel selection (ACS) process enables an access point to determine a best channel available, i.e., the channel with a least amount of interference, for it operation. When ACS is enabled, the access point scans frequencies for all neighboring access points and their signal strengths. Based on this data, the access point then determines which frequency is least likely to be interfered with by these other access points. The access point switches itself to this frequency and begins operation. During normal operation, the access point may periodically rescan the air space and reevaluate its current operating channel. Preferably, every neighboring access point has its own channel, and the co-channel interference levels should be low enough so that there is a maximum coverage and high throughput for the network. If these characteristics cannot be achieved, the access point may then adjust its power automatically to reduce the interference level in the network. This automatic power adjustment (APA) feature preferably operates across a set of access points, each of which has the function. In this manner, the transmitting power of the neighboring access points in the wireless network is 'cooperatively' adjusted to minimize the channel interference and maximize the coverage and throughput for the network. A method of determining optimal access point locations for access points that perform the ACS and APA functions is also described.

Determining optimal access point locations for access points that perform automatic channel selection and automatic power adjustment

Wireless access point (AP) automatic channel selection and automatic power adjustment

Wireless access point (AP) automatic channel selection

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Northborough, MA, United States of America

Hien Nguyen