Importance

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Abstract

Methods and apparatus for estimating mobile station location in a wireless communication system. At initiation of a call or a page response, a mobile station of the system sends an access request signal to a primary base station. The primary base station responds with an access acknowledgment which may be intentionally delayed such that the mo bile station increases its transmit power level. The primary base station then transmits a channel assignment message to the mobile station. The mobile station responds by transmitting a location signal in the form of a known user-specific traffic preamble at the higher transmit power level. The primary base station intentionally delays sending an acknowledgment of the preamble, such that the mobile station transmits the preamble for a longer period of time than it would otherwise. This additional transmission time allows the preamble to be detected accurately in the primary base station as well as in a number of other surrounding base stations in a manner suitable for generating path delay measurements. A primary location processor associated with the primary base station uses the path delay measurements from the primary and surrounding base stations to generate an estimate of mobile location. The mobile location estimation may be provided during an on-going call by the primary base station sending a fake handoff message to the mobile station directing it to handoff to the same base station and traffic channel but with a different power level and preamble length, or by the primary base station sending a predetermined location probe message directing the mobile station to transmit the traffic preamble with a desired power level and preamble length.

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First Claim