Appeal No. 2000-0326 Page 2
Application No. 08/644,465
unit, i.e., a cellular subscriber. When the subscriber moves
to the periphery of the coverage area of its serving base
station, an increase in path losses between the serving base
station and the subscriber creates a situation in which an
adjacent base station can better serve the subscriber.
Consequently, service of the subscriber is handed off to the
adjacent station.
Service must sometimes be handed off between a CDMA base
station and a base station utilizing a communication system
protocol that is not spread spectrum, e.g., the Advanced
Mobile Phone Service (“AMPS”) protocol. Heretofore, service
to a subscriber was prematurely handed off to the AMPS base
station, thereby squandering the benefit of spread-spectrum
services.
In contrast, the appellants determine when to hand off
service from a CDMA base station to an AMPS base station by
comparing a subscriber's phase shift measurement to a
threshold and determining a reference CDMA base station from
an active set of CDMA base stations. Next, corrected phase
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