CSFB的3GPP协议有没？

参见 23.272

 R10 版本，23.272协议里面：

CSFB Priority call handling ensures that, when GERAN/UTRAN supports eMLPP service (TS 22.067 [37]), end-to-end priority handling is provided for both mobile originated CSFB calls by a service user in E-UTRAN and for mobile terminated CSFB call from a service user to a normal or service user in E-UTRAN. A service user's EPS subscription contains an indication of the users CS domain priority status, i.e. MPS CS Priority. If the UE is subscribed to CS domain priority, the UE's USIM shall belong to one of Access Class 11 to 15.