hehe, 見(jiàn)規(guī)范有這條描述啊
The UE shall include this IE if the TIN indicates "
-TMSI" and the UE holds a valid GUTI, P-TMSI and RAI.
TRACKING AREA UPDATE REQUEST message.
If the UE supports A/Gb mode or Iu mode, the UE shall handle the Old GUTI IE as follows:
-If the TIN indicates "
-TMSI" and the UE holds a valid P-TMSI and RAI, the UE shall map the P-TMSI and RAI into the Old GUTI IE. If a P-TMSI signature is associated with the P-TMSI, the UE shall include it in the Old P-TMSI signature IE. Additionally, if the UE holds a valid GUTI, the UE shall indicate the GUTI in the Additional GUTI IE.
NOTE:The mapping of the P-TMSI and RAI to the GUTI is specified in 3GPP TS 23.003 [2].
-If the TIN indicates "GUTI" or "RAT-related TMSI" and the UE holds a valid GUTI, the UE shall indicate the GUTI in the Old GUTI IE.
覺(jué)得不難理解了俄~~~