想了解一下實際的信令流程，按照一些資料的說法，LTE上的SMS可以采用 SMS Over SGs或者SMS over IP，如果哪位大俠有SMS Over IP的碼流，求分享一下：

With SMS-over-IP functionality, the UE can send traditional short text messages over the IMS network. In the IMS network, an IP-Short-Message-Gateway (IP-SM-GW) provides the protocol interworking to submit short messages from the sending UE to the service center, and from the serving center to the receiving UE. It also handles SMS status reports from the serving center to the sender.
Figure 19 shows the message flow for mobile originating SMS. The UE as SM-over-IP sender submits a short message via a SIP MESSAGE request. This request includes the short message, and routing information for the IP-SM-GW to forward the short message. The S-CSCF analyses the request against the initial filter criteria (iFC) and determines whether to send the SIP MESSAGE request to the IP-SM-GW. The initial filter criteria are made available from HSS to S-CSCF during user registration and indicate the user’s subscription information, i.e. information about the application server to be contacted and trigger points that should be checked before the application server is contacted. The IP-SM-GW forwards the short message to the service center which returns a submission report. The submission report is sent to the UE in a SIP MESSAGE.