Question: When a UE moves from GERAN/UTRAN to E-UTRAN, how are the 16 least significant bits of the GERAN/UTRAN <P-TMSI> mapped to the E-UTRAN GUTI?
Option 1: Mapped into bit 31 and down to bit 16 of the E-UTRAN <M-TMSI>
Option 2: Mapped into bit 15 and down to bit 0 of the E-UTRAN <M-TMSI>
Option 3: Mapped into bit 23 and down to bit 8 of the E-UTRAN <MME Group ID>
Option 4: Not mapped; only the P-TMSI signature is sent intact to the MME
Explanation: According to specified mapping rules for a UE transitioning from GERAN/UTRAN to E-UTRAN, the 16 least significant bits of the GERAN/UTRAN <P-TMSI> (starting at bit 15 and down to bit 0) are specifically mapped into bit 15 and down to bit 0 of the E-UTRAN <M-TMSI>, ensuring continuity and correct identification within the new network.