Appeal No. 2000-0326 Page 3
Application No. 08/644,465
shifts are calculated for each CDMA base station in the active
set. Service unit is handed off to an AMPS base station
underlying the CDMA coverage area having the smallest
corrected phase shift. Waiting until a threshold event is
received by the subscriber to hand off service allows the
subscriber to travel farther in the CDMA coverage area before
being handed off to the AMPS base station.
Claim 1, which is representative for present purposes,
follows:
1. A method for performing handoff in a spread-
spectrum communication system, the method comprising
the steps of:
measuring a time between a base station's
transmitted signal and a corresponding received
signal transmitted from a remote unit to produce a
measured phase shift;
comparing the measured phase shift to a
threshold to produce a comparison;
correcting the measured phase shift to produce a
corrected phase shift, wherein the step of
correcting comprises adjusting the measured phase
shift based on a time between a second base
station's transmitted signal and a corresponding
signal received at the second base station; and
handing off the remote unit based on the
corrected phase shift and the comparison.
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