A.CSFB B.Esrvcc C.VoLTE D.CSFB和VoLTE
A.UPDATE B.re-INVITE C.100Trying D.183response
A.8kHz B.8Hz C.16kHz D.16Hz
A.MME B.SGSN C.IMS D.EPC
A.15 B.25 C.30 D.5
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