1). One Voice Initiative - IMS “One Voice” Profile
§ As LTE is a pure IP technology, traditional voice and SMS services must be implemented over the packet network.
§ The One Voice Initiative aims to achieve an industry agreement on a harmonized way to implement voice and SMS over LTE based on existing standards.
§ One Voice Initiative uses current open standards to define the minimum mandatory set of functionality for interoperable IMS-based voice & SMS in LTE.
§ A technical profile document was created, covering the device (UE), the LTE Access Network, the Evolved Packet Core Network, and the IP Multimedia Subsystem
§ This “Voice over IMS Profile” specification has been produced by AT&T,
§ The One Voice Initiative aims to achieve an industry agreement on a harmonized way to implement voice and SMS over LTE based on existing standards -“Voice over IMS Profile” specification
§ This solution envisaged for the mid and long term is to introduce network operator based voice services in LTE with the IMS.
Note: For facilitating session transfer (SRVCC) of the voice component from LTE to the CS domain, the IMS multimedia telephony sessions needs to be anchored in the IMS
2). IMS “One Voice” Profile
Pros:
§ Most feature rich
§ Enables Real time Rich Media - fully IP based platform for rich media communication
§ Doesn’t require MSC support
§ Handing-over ongoing IMS based voice calls to circuit switched networks via SRVCC (between IMS over PS access and CS access for calls is anchored in IMS)
§ Convergence via ICS – IMS based on the popular SIP is widely used in fixed line IP based networks for Voice over IP
Cons:
§ Complexity - significant complexity of the system, and it will still take several years before large scale commercial IMS deployments, and features to handle wireless specific issues such as unreliable radio connections, application servers for external application development, international roaming, scalability, security, etc.
§ IMS Market timing
§ SRVCC provides the ability to transition a voice call from the VoIP/IMS packet domain to the legacy circuit domain, but the ability to transition from the circuit domain to the packet domain is not addressed in the current generation (R8) of LTE standards
§ Limited LTE Coverage if only hotspots at the initial phase
§ SRVCC-capable mobile initiated in a voice call determines that it is moving away from LTE coverage
§ ICS-capable UE if ICS is utilized
3). The scope of the profile includes the following aspects:
§ IMS basic capabilities and voice including supplementary services
§ Real-time media negotiation, transport and codecs
§ LTE radio and evolved packet core capabilities
§ Functionality that is relevant across the protocol stack and subsystems
4). Voice over IMS Profile – Network Architecture:
§ Network Architecture http://docs.google.com/View?id=ddh56dhg_299c2gzj5gv
5). Supplementary Services (SS) overview
§ Supplementary services shall be supported as defined as part of 3GPP MMTel
§ It is up to the operator to enable these services.
§ UE and TAS shall support the supplementary services listed below.
§ Originating Identification Presentation
§ Terminating Identification Presentation
§ Originating Identification Restriction
§ Terminating Identification Restriction
§ Communication Diversion Unconditional
§ Communication Diversion on not Logged
§ Communication Diversion on Busy
§ Communication Diversion on not Reachable
§ Communication Diversion on No Reply
§ Barring of All Incoming Calls
§ Barring of All Outgoing Calls
§ Barring of Outgoing International Calls
§ Barring of Incoming Calls - When Roaming
§ Communication Hold
§ Message Waiting Indication
§ Communication Waiting
§ Ad-Hoc Multi Party Conference
§ For supplementary service configuration, the UE and IMS core network shall support XCAP at the Ut
6). Minimum Feature Set for IMS VoIP over LTE
The minimum feature set for the UEs and networks to support the IMS VoIP over LTE.
§ Domain Selection
§ SR-VCC
§ Service Setting Management
§ Emergency Service - support emergency services via E-CSCF in the IMS domain
§ Roaming Service - support IMS roaming with both P-CSCF and PGW in the visited network
§ SMS Support
Note:
§ session based charging via Rf interface is supported in home and visited network;
§ signalling encryption is terminated in the P-CSCF in the visited network, which may be required to fulfil regulatory requirements;
7). IMS Function Supported for IMS VoIP over LTE
§ SIP Registration: support for service route discovery, network-initiated de-registration, subscribe to the registration event package
§ Authentication: support the procedures for ISIM based authentication, for USIM based authentication, for authentication at the Ut
§ Addressing: support SIP URIs (alphanumeric) and MSISDN based IMPU, local numbers and may support geo-local numbers
§ Call establishment and termination: follow the SIP procedures for establishment and termination of a call, support reliable provisional responses, use an ICSI value to indicate the IMS Multimedia Telephony service (MMTel)
§ Forking: UE shall be ready to receive responses generated due to a forked request and behave
§ Support for Signalling Compression shall be mandatory in the UE and the P-CSCF
§ Support of the debug event package is optional
§ IMS Media: The needed SDP support in UEs and in the IMS core network and it describes the necessary media capabilities both for UEs and for entities in the IMS core network (MRFP and the MGW) that terminate the user plane.
§ IMS Codecs for Voice Media: The UE and the entities in the IMS core network that terminate the user plane shall support the AMR speech codec including all eight (8) modes and source rate controlled operations.
8). Protocol Supported for IMS VoIP over LTE
§ The UE and the network shall support both IPv4 and IPv6 for all protocols
§ Protocol Stack Support for VoIP application: SIP, SDP, RTP, RTCP and XCAP/HTTP
§ The IMS profile part lists the mandatory capabilities, which are required over the Gm and Ut reference points.
§ TCP/IP includes UDP, and HTTP includes XCAP in the protocol suite
§ The UE and the entities in the IMS core network that terminate the user plane shall use RTP over UDP to transport voice.
§ The UE shall use the same port number for sending and receiving RTP packets.
§ The UE and the IMS core network shall be able to receive and answer to an SDP offer using SDPCapNeg.
§ The answer shall indicate the use of the RTP AVP profile.
§ Support for RTP profile AVP
§ The bandwidth for RTCP traffic shall be described using the
§ Protocol Stack http://docs.google.com/View?id=ddh56dhg_3013hdmqddf
9). Function Supported for IMS VoIP over LTE
§ TAS from MMTel or IMS Centralized Services (ICS) - Service anchor in IMS to improve service consistency
§ Single Radio Voice Call Continuity (SR-VCC) - Swap between IMS and CS without preserving services
§ IP Multimedia Subsystem (IMS) Emergency Sessions is supported via E-CSCF.
§ The Emergency solution should be able to provide continuity of location support the SR VCC of emergency calls.
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