VoLTE | Voice Over LTE & IMS Network full package

Understand the IMS architecture and the role of CCF and CSCF, SIP signaling, and SDP negotiation to enable VoLTE over LTE, contrasted with CS fallback.

Explore the IMS and VoLTE architecture, including MRF C and MRF P, CSF, PCF, and default and dedicated beer, and how SIP signaling and SDP enable calls.

Explore how the serving CCF, proxy CSC, interrogating CSC, and emergency CCF in IMS coordinate registration, mutual authentication, service access, and call signaling to enable VoLTE traffic.

Explore the IMS architecture and SIP signaling flow for voice sessions, tracing SIP invites through the CCF, serving CSCF, XSS lookup, to QoS bearers.

Learn how a VoLTE user accesses the IMS network over LTE, registers via the default bearer, and uses a dedicated bearer for media traffic with IMS QoS.

Explore how the IMS CSS interworking function enables VoLTE calls between the IMS and legacy circuit-switched networks, detailing signaling gateways, media gateways, SIP/ISUP conversion, and SDP negotiation.

Learn how the MRFC and RFP manage media in IMS. MRFC sends control commands to the RFP in the user plane to play announcements, enable conferences, and perform transcoding.

Explore the interconnect border control function in IMS networks, detailing the application layer gateway, transcoding gateway, topology hiding function, IPv4/IPv6 translation, and the role of session border gateways.

Explore how the home subscription server (XSS) in the APC and IMS networks functions as a unified subscriber database, handling authentication, authorization, accounting, mobility management, user services, and session setup.

Learn about IMS user identities—the IMPI (private), IMPU (public), PSI (public service identity), and the service key—and how they authenticate and register within the IMS network.

Learn how a subscriber's sim card enables ims access through usim and isim, with impi profiles, authentication keys, and filtering criteria for 2g-4g roaming and service access.

Understand the VoLTE concept and IMS integration, how operators enable VoLTE on handsets via vendor licensing and testing, delivering voice, SMS over IP, and video over LTE.

Explore session border controller (sbc) at the ims edge or between cs and ims, enabling proxy ccf, qos reservation via pcf, emergency call handling, and single radio voice call continuity.

Learn roaming in IMS, detailing signalling between home and visited networks. Explore how default and dedicated beer govern call setup and media paths via proxy ccf, s-cscf, p-cscf.

Explore how IMS APNs enable VoLTE by connecting via the default IMS APN and the UTI APM for supplementary services through IMS API, including roaming and home network scenarios.

Explore how VoLTE bearers manage signaling and media in IMS: default IMS APN, dedicated IMS APN, and UTI APN bearers with QoS, IP addresses, and guaranteed bitrate considerations.

Discover VoLTE security in IMS networks, including mutual authentication, encryption, and integrity protection, and how a security association protects signaling with IMS keys and algorithm sets during registration.

Learn how SIP handles registration and session initiation in the IMS network, with SDP describing media and RTP transporting it, enabling conferencing and codec negotiation.

Explain how sip messages drive volte and ims, distinguishing sip requests from responses and detailing register, invite, bye, options, cancel, and acknowledge with provisional and final codes.

Explains how the multimedia telephony application server in the IMS network manages sessions between two users and handles supplementary services, including roaming status.

3GPP defines four voice domain preferences for user equipment, prioritizing IMS/VoLTE or CS based on 4G coverage and device usage settings.

Discover how IMS assigns two identities per subscriber: the IMPI private identity and the IMPU public identity; private is unique per user, while public can include multiple IMPUs.

Learn UE and HSS requirements to access IMS for VoLTE, including device and software readiness, voice domain preference, icin/impi/impu identities, and SIP, SDP, RTP signaling.

Learn IMS registration for VoLTE, including PLMN and cell selection and RR connection establishment, attach procedures, DNS proxy CSC lookup, SIP registration, and third-party registration with the application server.

Describe how a UE attaches to the network via attach request, authentication, update location, and bearer establishment. Explain key derivation: master, cipher, integrity, and cosmic keys, and they secure traffic.

Learn how a user attaches to the IMS APN by issuing a PDN connectivity request, establishing a default bearer for IMS signaling, and coordinating gateway and PCF for IMS QoS.

Explore the SIP register message in IMS, detailing the registration flow from user equipment to proxy CSCF, including message lines, max-forwards, registration expiry, and authentication with nonce.

Describe the IMS registration flow, including CIP register messages, IMPI and IMPU, and the UE IP address, routed by proxy and interrogating CCF.

Explore the third party registration process in VoLTE IMS, where the serving call session control function updates the user profile and identifies originating and terminating services.

Learn how the user equipment registers on the EPC and IMS and subscribes to the registration state event via the proxy CCF and S-CSCF, with authorization and notifications.

Explore how VoLTE uses the IMS network for roaming call flows, covering SIP register, SIP invite, SDP, and precondition, update, 180 ringing.

Explore how the invite message carries the sdp offer, detailing version, owner, session, media, codecs, and addressing, while outlining rtp media flow and quality of service considerations.

Explore how mobile originating calls in VoLTE use invite messages, SIP/SDP negotiation, codec selection, and IMS signaling through proxy-CSCF, DNS, and call session control functions to establish a call.

Explore the VoLTE call flow at a high level, detailing media handshake, resource reservation, precondition, and signaling procedures like SIP invite, SDP offers/answers, and codec negotiation.

Learn the VoLTE SIP call flow: invite with SDP offer and IMS details via proxy CSC to the serving call session control function, plus 100 trying and 183 progress.

Trace ims call flow from sip invite to setup, showing proxies, serving call session control function, hss, and enum guiding 100 trying, 183 session progress, and 200 ok with sdp.

Explore how the PCF interacts with IMS to enable early call setup via the 183 session progress and to reserve dedicated bearers with QCI, bitrate, and negotiated codecs.

Establish a dedicated bearer by exchanging a create dedicated bearer request between the PD and gateway, using S5 and S1 tunnel endpoint IDs, followed by radio bearer setup and reauthentication.

SRVCC enables single-radio voice call continuity across 4G to 3G/2G handovers to prevent call drops, featuring basic, advanced, enhanced, video, and reverse SRVCC types.

Compare srvcc and csfb in volte and ims networks, where csfb switches before a call to 2g and 3g, while srvcc maintains the call, reducing drops and setup time.

Follow a high-level SRVCC flow for volte calls as 4g coverage wanes and handover to 3g occurs, detailing signaling via the v interface, resource reservation, and call continuity.

Explain the SVC flow by detailing the preparation phase and execution phase, emphasizing resource reservation, measurement reports, and handover requests guiding a 4G to 3G transition.

Describe the srvcc flow execution phase as a 3g user receives Node B signals, completes ue handover to the msc, and initiates tmc allocation with 3g voice and data sessions.