With the rise of 4G technologies and the deployment of several LTE networks, voice over LTE is becoming more and more a necessity. One of the major challenges standing in the way of MNO’s towards all-IP networks is to benefit from the cost-effectiveness  of the ecosystem while maintaining a superior level of quality for both, voice and SMS services over LTE. This requires a fully compliant ecosystem equipped with robust handset clients in order to provide transparent end-user experience in terms of voice, SMS, as well as other supplementary services over LTE. IMS, which has become the platform of choice for an increasing number of MNOs, is considered to be the corner stone for VoLTE services. IPneo has been among the very first companies to provide VoLTE clients thanks to its complete, standards compliant IMS stack that responds to the market call for reliable, interoperable, and portable VoLTE clients.

IPneo offers a distinctive VoLTE client that is fully compliant with the latest GSMA profile for Voice over LTE. IPneo’s VoLTE client, has been designed to provide both LTE OEM's and operators with a safe path towards reliable Voice over LTE services. The client is built upon a robust IMS stack that provides all necessary IMS core functionalities including registration, AKA authentication with IPSec support, session setup and resource reservations. AMR voice codecs (both WB and NB) are supported in bandwidth efficient mode with an optimized jitter buffer implementation according to MMTel recommendations. The media plane runs on top of an optimized RTP stack thus enabling voice communications with high quality. The client is built with VoIP and supplementary services enablers thus enabling easy integration with any VoIP application to run on top of IPneo’s VoLTE client. The client is quite modular and flexible, provided with a well-defined set of API's to allow full access to the core functionalities, and it is both hardware and OS independent. This gives both OEM's and operators the freedom of choice between different target platforms and shrinks their time to market.

Features:

• Full compliance with VoLTE profile (IR.92)
• SIP-based registration and call setup
• IMS AKA with IPSec support
• Supplementary services support (Call forwarding, Incoming/Outgoing Call Barring, ID presentation and restriction, etc…)
• Emergency services support
• SMS over IP
• QoS negotiation using SIP Preconditions
• Seamless support of dedicated signaling and media bearers
• AMR-NB and AMR-WB codecs in both octet and bandwidth efficient modes

VoLTE Client Architecture:

• VoIP
  • Exposes the interfaces needed for the application to initiate, receive , accept or reject voice calls
  • Interacts with the Supplementary services for call privacy, call waiting, call diversion, hold, resume, and ad-hoc conference calls

• SMS over IP
  • Exposes the interfaces needed for the application to send and receive messages over IP and display delivery notifications

• Supplementary Services
  • Interact with VoIP services module for handling supplementary services
  • Interacts with XCAP for configuring and retrieving Supplementary services configurations from Application server

• IMS stack
  • SIP Stack - Implements the complete SIP protocol
  • SDP Stack - Negotiates the supported codecs and updates the sessions accordingly
  • RTP Stack - Implements the complete RTP/RTCP protocols
  • Resource Reservation - Guarantees the required resources based on SIP preconditions and the underlying access layer
  • Sigcomp - Implements the Signalling compression for SIP messages

• Environment Layer
  • Link Abstraction - provides the IMS stack abstraction from the access network (EUTRAN, UTRAN, GERAN, WiFi, etc...)
  • Security Abstraction - provides the IMS stack abstraction from the platform dependent TLS and IPSec implementations
  • Audio/Video Abstraction - provides the IMS stack interface to platform dependent audio and video drivers

In the past few years the mobile devices revolutionized to the extent that leveraged the end-users expectations to have a seamless cellular access to all-to-date Internet services. The IP Multimedia Subsystem is the key technology that makes it possible to access Internet services from emails and instant messaging to VoIP and Video transmission through the cellular network. In other words, IMS provides a seamless access to the Internet independent of the network type, either wireless or wired network, the terminal type, either mobile orfixed,  the device, either PC, user equipment or even  a TV.

IMS specifications were first introduced in 3GPP Release 5 as an enhancement to Packet Switched (PS) domain supporting IP Multimedia Services. IMS can be interpreted as the multimedia session and service control for PS domain. Besides, IMS provides inter-working functionalities to existing networks such as the traditional Circuit Switched (CS) domain, PSTN/ISDN networks and the Internet as well as the establishment of multimedia sessions in the same or between different IMS domains.

IMS provides the complete solution to support any IP multimedia application, including voice and video communications. It is a three-layered structure allowing full convergence in terms of access, services, charging, control, and management. The three-layered structure ensures that IMS is access-independent and thus different access networks can be used to deploy IMS achieving the convergence ever aimed for. In addition to the initially supported GPRS-CN access (Cellular), 3GPP has added WLAN in Release 6 (WiFi) and xDSL in Release 7 as additional IP-Connectivity Access Networks (IP-CANs).

IMS allows easy and fast service development and integration through the specification of common functions such as registration, authentication, authorization, security, charging, session management, policy and bearer control. IMS also offers an open application and service architecture, thereby allowing fast deployment and operator differentiation. In this context, IMS can be viewed as "the" application enabling platform of the 3GPP Core Network.

All these aspects -- including the use of well established common IETF protocols such as SIP and SDP -- are beneficial from an operator's, service provider's and manufacturer's perspective to enable the convergence of data, speech and mobile networks. Even organizations outside 3GPP can easily define services on top of IMS using its common functions. This concept was proven with the development of the Push-to-Talk over Cellular (PoC), SIMPLE Presence, XML Document Management (XDM) and Instant Messaging (IM) services by the Open Mobile Alliance (OMA).

This virtually provided operators and terminal manufacturers with infinite capabilities to develop myriad enriched services for their end-users through a cost-effective IP-based platform namely, the IMS. One of the key applications built on top of IMS and aiming for enriching end user experience is the Rich Communication Suite (RCS) group of standards. RCS is an initiative led by GSMA and a group of operators, terminal vendors, infrastructure providers and other telecommunication companies, gathering their efforts to standardize these desired services . RCS is a suite of applications and services defined by GSMA that enables interoperable, enriched communications and feature rich services including Enhanced Phonebook, Enhanced Messaging and Enriched Voice Calls. RCS covers a group of services including: presence, image share, SMS/MMS, Instant messaging, file transfer, and Video Share.

From a user equipment (UE) point of view, this requires a flexible IMS client framework equipped with several standardized service enablers so that the end user gains full access to this new and emerging world of mobile multimedia applications. IPneo capitalizes on these promising and standardized technologies to provide robust solutions that help operators and terminals manufacturers reshaping and enriching their end-users’ experience thus meeting their ever growing needs.