The DC keeps track of a client's location, using the algorithm described in [11]. The algorithm takes into account the signal strength of a client's transmissions as reported by various DAPs, and the location of those DAPs, to determine the approximate location of the client. The median location error is about 1.5 meters. This is sufficient for our purpose because we only need to detect that the client's location has changed significantly.
The DC updates the locations of clients in the system every 30 seconds.
When a client's location changes by more than 10 meters, the DC finds another DAP for the client to associate with, using the criteria
described in the previous section. If such a DAP is found, the client is
handed off to the new DAP. A client that undergoes handoff is considered
ineligible to participate in the subsequent round for load balancing to
prevent oscillations. It is, however, eligible to participate in another,
mobility-related handoff.
