US 5,633,888 AGranted

Method of using an access point adjacency matrix to establish handoff in a wireless LAN

AssigneeAdvanced Micro Devices, Inc.

InventorBrett B. Stewart

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Abstract

An adjacency matrix is incorporated into a local area network in order to provide smoother and faster transitions between mobile devices and access points of adjacent or overlapping microcells. The adjacency matrix can be based on fuzzy logic and updated periodically. Factors used to create the matrix can include the ability to establish a communication link, signal strength measurements, roam times, time of day, day of week and other factors germaine to the local area network topology and patterns of its usage. The mobile device thus effects the transition by attempting to communicate on the frequencies associated with hopping schemes of the access points which are most likely adjacent to the previous access point. As a result, the average transition time is greatly reduced.

Claims18

Dependent claims

A method of maintaining communication in wireless local area network (LAN) with an access point coverage topology in a dynamic environment, the LAN containing a plurality of access points and a plurality of active mobile devices, the method comprising the steps of:

(a) assigning a unique frequency hopping scheme to each of the access points;
(b) initiating a communication link between an active mobile device and a corresponding one of the access points, the communication link being in accordance with the frequency hopping scheme of the access point;
(c) determining, for the active mobile devices, a most likely frequency hopping scheme of an alternate access point by referring to an access point adjacency matrix, the alternate access point being different from the corresponding access point;
(d) attempting to establish a communication link between the active mobile device and the alternate access point in accordance with the most likely frequency hopping scheme;
and
(e) returning to the adjacency matrix to obtain a next most likely frequency hopping scheme if the communication link is not established in step (d),
wherein steps (d) and (e) are repeated until the frequency hopping scheme of the alternate access point is obtained from the adjacency matrix and a communication link is established between the active mobile device and the alternate access point in accordance with its frequency hopping scheme.

4 more elements

Dependencies are inferred from the claim text.