Based on conventional SIP network, we have been exposed to various kinds of SIP tools such as MS Lync or VoIP phones. As LTE purely packet service has been coming in cellular network, IMS is one of highly achievable voice solutions lately. IMS network is composed in SIP protocols, which must be understood through several RFC or other associated websites. There are many test procedures about MTSI (Multimedia Telephony Service for IMS) in 3GPP specifications.
If you would like to refer IMS normal registration regarding LTE devices, TS36.508 4.5A.3 Procedure for IMS signalling, TS34.229 C.2 Generic Registration Test Procedure - IMS support, and Annex A.
Most of IMS embedded LTE devices have P-CSCF Server address one of these 3 types, IPv4, IPv6, or IPv4v6 from LTE network unless any commonly published IMS applications like IMSdroid. EPS QCI (QoS Class Indicator) is also allocated while a default EPS bearer is established for IMS. Based on TS23.203 Table 6.1.7, QCI = 5 can be allocated for IMS signalling, which may be changed by operator's policy.
Based on these information through LTE protocol procedure, UE can access P-CSCF with REGISTER procedure with Authentication according to TS36.508 4.5A.3. If REGISTER procedure went through properly, P-Associated-URI must be delivered to UE.
After this, UE is supposed to go through SUBSCRIBE/NOTIFY procedure, which must include "reg" event package and maybe other else in Event header field. The first registration with REGISTER method would be done SIP protocol perspective while the second one with SUBSCRIBE/NOTIFY method would be necessary for several purposes at operator's network; Confirmation of subscription creation, requesting/refreshing of subscriptions, and receiving and processing State information as well as protect operator's network. Once subscription is done properly, Subscription-State, registration aor, id, and state, contact id, state, event, and uri in xml message must be delivered by NOTIFY method. RFC6665 can be referred in detail.
While testing lots of LTE IMS devices, different domain names are used, noticed. Definitely user=phone must be included in From and To header field for REGISTER procedures. More will be added..
When LTE devices would like to approach E-CSCF to PSAP (Public Safety Answering Point), it is almost similar to normal IMS registration procedure but 2-3 points. Based on TS36.508 4.5A.4 Generic Test Procedure for IMS Emergency call establishment in EUTRA and TS34.229 C.20 Generic Test Procedure for IMS emergency registration and Annex A, another default EPS bearer is required with PDN Request type value = emergency under environment is required with ims-EmergencySupport-r9 IE = true in SIB1.
When UE triggers REGISTER procedure with Authentication based on what it gets from LTE network, Contact header field includes "sos" parameter. After P-Associated-URI is delivered, it is going to be used in INVITE method directly with no SUBSCRIBE/NOTIFY methods.
IMS Normal Registration
If you would like to refer IMS normal registration regarding LTE devices, TS36.508 4.5A.3 Procedure for IMS signalling, TS34.229 C.2 Generic Registration Test Procedure - IMS support, and Annex A.
Most of IMS embedded LTE devices have P-CSCF Server address one of these 3 types, IPv4, IPv6, or IPv4v6 from LTE network unless any commonly published IMS applications like IMSdroid. EPS QCI (QoS Class Indicator) is also allocated while a default EPS bearer is established for IMS. Based on TS23.203 Table 6.1.7, QCI = 5 can be allocated for IMS signalling, which may be changed by operator's policy.
Based on these information through LTE protocol procedure, UE can access P-CSCF with REGISTER procedure with Authentication according to TS36.508 4.5A.3. If REGISTER procedure went through properly, P-Associated-URI must be delivered to UE.
After this, UE is supposed to go through SUBSCRIBE/NOTIFY procedure, which must include "reg" event package and maybe other else in Event header field. The first registration with REGISTER method would be done SIP protocol perspective while the second one with SUBSCRIBE/NOTIFY method would be necessary for several purposes at operator's network; Confirmation of subscription creation, requesting/refreshing of subscriptions, and receiving and processing State information as well as protect operator's network. Once subscription is done properly, Subscription-State, registration aor, id, and state, contact id, state, event, and uri in xml message must be delivered by NOTIFY method. RFC6665 can be referred in detail.
IMS associated identities
While testing lots of LTE IMS devices, different domain names are used, noticed. Definitely user=phone must be included in From and To header field for REGISTER procedures. More will be added..
IMS Emergency Registration
When LTE devices would like to approach E-CSCF to PSAP (Public Safety Answering Point), it is almost similar to normal IMS registration procedure but 2-3 points. Based on TS36.508 4.5A.4 Generic Test Procedure for IMS Emergency call establishment in EUTRA and TS34.229 C.20 Generic Test Procedure for IMS emergency registration and Annex A, another default EPS bearer is required with PDN Request type value = emergency under environment is required with ims-EmergencySupport-r9 IE = true in SIB1.
When UE triggers REGISTER procedure with Authentication based on what it gets from LTE network, Contact header field includes "sos" parameter. After P-Associated-URI is delivered, it is going to be used in INVITE method directly with no SUBSCRIBE/NOTIFY methods.