Importance

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Abstract

A method for performing the network direct system selection (NDSS) of a mobile station (MS) in a cellular communications system that includes the steps of: making a base station (BS) to include a dialed phone number designated for the NDSS in a CM SERVICE REQUEST message being transferred from the MS to a first MSC; making the first MSC to transmit a NDSS FEATURE REQUEST INVOKE message of the MS to the HLR upon confirming that the dialed phone number corresponds to the NDSS; making the first MSC to transmit a FEATURE REQUEST INVOKE CONFIRMATION message to the MS via the BS; making the HLR to transmit a QUALIFICATION DIRECTIVE message containing a service re-direction information to a first VLR coupled to the first MSC when the FEATURE REQUEST INVOKE message is accepted by the HLR; making the first VLR to confirm whether the QUALIFICATION DIRECTIVE message includes the service re-direction information; making the first VLR to transmit a SERVICE RE-DIRECTION message, consisting of the service re-direction information and a command to request the MS to report the return cause information when the NDSS failure occurs, to the MS; and, registering the location of the MS in a second VLR of a second MSC as directed by the SERVICE RE-DIRECTION message.

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First Claim