Voice Over 5G

Explore dual connectivity in 5g, detailing how user equipment connects to a master and a secondary base station and how master and secondary cell groups carry data and signaling.

Describe the 5G standalone option, with a pure 5G core (AMF and UPF) linked to the master GNP, using dual connectivity for coverage and high data rates.

Explore non-standalone option three, where the 4G LTE core and 5G radio connect through master e node B and enhanced gNB, with data bearer split by option three variants.

Explore 5G non-standalone option 4, using the 5G core network with a master GNB, dual connectivity to a next generation Enode B, and data bearer splitting at the UPF.

Examine 5g non-standalone option seven, detailing how the 5g core network and master gnb coordinate data bearer split, upf involvement, and dual connectivity with a secondary gnb.

Explore voice over 5G solutions across deployment options, including voice over LTE in 5G non-standalone, LTE fallback (EPs or internet), and voice over 5G NR.

Explore VoLTE in 5G non-standalone deployment (option 3/3A/3X) with a 4G core EPC, master and secondary eNodeB, IMS voice, and CSFB/SRVCC handoffs across 2G/3G while noting dual connectivity energy concerns.

Explain how voice over LTE uses eps and rat fallback to enable calls during early to mid 5G deployment, switching between 5G core and 4G core IMS.

Explore voice over 5g new radio (vonr) in standalone 5g deployments with ims calls, delivering high quality voice and reduced complexity, while interoperating with 4g for mobility and broad coverage.

Explain how voice services in 5g deployment options 4 and 7 use a 5g core connected to master and secondary enodeBs to provide VoNR or VoLTE with IMS.

Explore how the IP multimedia subsystem (IMS) enables unified voice over IP and multimedia services across fixed and mobile networks, with seamless handover between Wi-Fi and cellular using SIP signaling.

Explore IMS features: a scalable, flexible layered architecture with diverse application servers and backward-compatible, open, vendor-independent interfaces across access networks.

Study the IMS architecture’s layers: the application layer hosts service logic on application servers, the control layer manages session control, and the transport layer connects end devices via access technologies.

Regulate IMS communication flows via the call session control function, supported by the Home Subscriber server and the media resource function and media gateway control function.

Explore call session control functions (CSCFs) in IMS networks, focusing on the proxy CSCF that routes SIP requests, blocks flooding attacks, and ensures QoS for end-to-end voice and multimedia calls.

Describe how the interrogating CSCF queries the HSS to locate a device’s registration status or its serving CSCF, enabling registration and incoming-call routing in IMS networks.

The serving call session control function authenticates devices by querying the HSS for security keys during IMS registration and coordinates voice call setup with application servers for billing.

Discover how telephony application servers in the IMS network extend call setup with supplementary services and value-added features like instant messaging, gaming, and video conferencing.

Explore the IMS protocols SIP, Diameter, and RTP, learning how SIP establishes call sessions, Diameter handles authentication, authorization, and billing for devices, and RTP carries voice and video media.

Explore how the Session Initiation Protocol negotiates call parameters by carrying Session Description Protocol (SDP) packets inside SIP packets, enabling devices to agree on IP addresses, ports, codecs, and bandwidth.

Explore SIP services that locate the called device IP, determine availability, and negotiate device capabilities using HTTP, then set up sessions via session setup and session management signaling.

Learn how the SIP protocol uses a client-server model with a SIP user agent client and server, and explore invite, acknowledgement, buy, cancel, register, and options methods.

Learn how a user equipment connects to the IMS network by establishing a PDU session, registers with the IMS, and then can make an IMS call.

PDU sessions connect user equipment to the 5G core and IMS data network, creating two QoS flows: signaling with high priority and media bearer with guaranteed bitrate.

See how the 5G core connects to the IMS network via upgraded interfaces. The UDM acts as the HSS under 5G service-based architecture, with ENC_IMS services on release 16.

Describe how a user equipment registers with the IMS network by establishing a PDU session with QoS Qci 5 and discovering P-CSCF IP via SMF assignment, static configuration, or DHCP/DNS.

Explore how a user equipment registers with the IMS network via a SIP registration request, through proxy, interrogating and serving call session control functions, with UDM authentication and registration confirmation.

During third party registration, the serving call session control function informs the telephony application server that the user is connected, enabling call diversion and caller ID hiding.

Explain the signaling path for a 5g ims voice call from registration to setup, via proxy, serving, and interrogating call session control functions, with sip invite and 183 session progress.

Follow end-to-end SIP signaling for call setup in 5G IMS, detailing SIP invite, 183 session progress, Prague message, 200 OK, and IMS media bearer with QoS flow and RTP transport.

Explain how proxy call session control functions monitor SIP bye and 200 ok messages to tear down the IMS bearer with 5G QoS identifier value 1.

Explore how speech codecs encode and decode voice for voice over IP, using adaptive multi-rate schemes that switch bit rates every 20 ms to match link quality on IMS.

Explore 4g lte and 5g voice codecs, including ebs backward compatible with wideband amr, robust to delay jitter and packet loss, ivr for immersive mono and stereo vr, rtp/udp/ip transport.

Describe enhanced voice services (EVS) codecs and their frequency ranges—from narrow band 300–3400 Hz to full band 23–20000 Hz—and the interoperable and primary modes that enable cross-network calls.

Learn how the optional N26 interface enables seamless 5G to 4G voice call continuity and mobility, preserving IP address continuity with a unified UDM/HSS database and S5 signaling.

Learn UE registration modes, including single registration with or without the N26 interface and dual registration, enabling seamless mobility between 4G and 5G networks with context and IP address transfer.

Explain how single registration without the N26 interface reroutes signaling from AMF to SMF, then via the PDM gateway and serving gateway to 4G/5G networks, causing voice call delays.

Enable dual registration mode registers a user equipment to both the 4G EPC and 5G core networks, creating EPC Gooty and 5G Gooty with separate sessions and no N26 interface.

Explore how 5G user equipment registers with the network, focusing on IMS voice support, AMF authentication and key agreement, and the exchange of UI capability information.

Demonstrate end-to-end voice over new radio call flow in a 5G IMS network, detailing PDU session establishment, SMF PCF policy checks, UPF coordination, and IMS bearer setup.

Describe eps fallback from the 5g core to the 4g core during voice setup, including redirection based fallback, inter-system handover, and context transfer via the n26 interface.

Explore EPS fallback high level signaling for IMS voice, detailing QoS flows, SIP invites, PDU session modification, and how gNodeB triggers 4G fallback to establish a dedicated IMS voice bearer.

Node B decides EPs fallback as either handover-based or redirection-based, using B two measurement-based handover with measurement reports, or blind handover and redirection via RRC release with redirection.

Compare v2 measurement based handover, blind redirection, and b1 measurement based redirection for eps fallback, noting blind redirection's simple planning and shorter setup versus measurement based redirection's higher success.

Describe EPS fallback from 5G to 4G via N26, detailing PDU session reconfiguration, IMS SIP signaling, and IMS bearer establishment in the 4G core.

Explain eps fallback signaling from the 5g core to the 4g core via n26, triggering ue redirection to the enodeb and establishing an eps bearer with qci 1 for ims.

Describe red fallback signaling from G node B to E node B when IMS voice cannot be established, including PDU session modification, QoS flows, and optional 4G fallback.

Explore volte in 5G NSA EN-DC, where non-standalone deployment uses a 4G core with a master eNB and a secondary gNB for IMS voice and data bearers.

Describe VoLTE signaling flow from 4G attach to IMS registration, detailing default bearers with qci values 6-9 and 5, SIP invite, and the dedicated voice bearer for voice packets.