Importance

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Abstract

When a mobile communication unit (e.g. a cellular telephone) is powered up, the unit must lock on to a local base station, or 'acquire' a base station signal, to enable the user to send and receive calls. To lock on a local base station, the mobile unit must determine the delay at which the base station is sending the pseudo random (PN) code. This process is called the 'acquisition.' The current art of acquiring a base station involves searching the possible code phases, or delays, one by one until the first signal is found. However, multiple base stations may be available to the mobile user, and the first found pilot signal may not be the strongest and may not be from the nearest base station. The present invention discloses a method and apparatus for searching all possible PN code phases and selecting the strongest phase instead of selecting the first phase. The method comprises of steps of testing all PN code delays, storing the delay and its corresponding signal strength of the delays having a signal strength greater than a threshold, and finally selecting the delay with the strongest signal among the stored delays.

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First Claim