Importance

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Abstract

A method and apparatus for providing a reliable means to perform handoff from a code division multiple access (CDMA) system using a pilot signal to an alternative access technique system. Simple pilot box circuitry is added to a set of border base stations. The border base stations are base stations which operate only in the alternative access technique and which have coverage areas which are contiguous with coverage areas of CDMA operation base stations. The mobile unit monitors for the pilot signal from the border base stations in the same manner as it monitors for pilot signals from the CDMA operation base stations. When the mobile unit detects the pilot signal corresponding to a border base station, it notifies a system controller in accordance with standard operation. The system controller is aware that the pilot signal corresponds to a border base station and thus triggers a hard handoff process to the alternative access technique system in response thereto. The border base stations use a time division duplex technique to monitor a pilot and synchronization sequence from a neighboring one of the CDMA operation base stations to obtain an estimate of absolute system time.

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First Claim