VoLTE: Voice, Text etc services over LTE

Essentially, Voice over LTE  (VoLTE) is GSMA’s adoption of the OneVoice initiative that describes standard configurations for carrying (packet) voice over LTE. VoLTE eliminates the need for 2G/3G voice and the whole problem of multiple networks and extra components and cost in devices by carrying the voice over the LTE channel using AMR coding. This is an interesting area to watch as a few network operators, several in the US have discussed it publicly including CSpire, US Cellular, Verizon Wireless and various public safety deployments.

Note VoLTE hand overs are Dual Radio Voice Call Continuity (DRVCC) for devices that have active 3G and LTE radio chains facilitating a seamless handover in spotty coverage, Single Radio Voice Call Continuity (SRVCC) enabling a seamless handover for spotty coverage with a single radio (either 3G or LTE at a time) and Circuit Switched Fall Back (CSFB) which is the in case all fails, throw the call over the wall and hope it sticks.

See Ericsson’s high level network art.

They have a good white paper too (see interesting links section.)

GSMA VoLTE initiative

The GSMA VoLTE (Voice over LTE) initiative was formally announced on 15th February 2010.  In establishing the VoLTE initiative, GSMA has adopted the work of the One Voice Initiative* as the basis of the work to lead the global mobile industry towards a standard way of delivering voice and messaging services for Long-Term Evolution (LTE).  Using IP Multimedia Subsystem specifications developed by 3GPP as its basis, GSMA have expanded upon the original scope of One Voice work to address the entire end-to-end voice and SMS ecosystem by also focussing on Roaming and Interconnect interfaces, in addition the interface between customer and network.

GSMA VoLTE is built upon some key, underlying principles.

Single implementation promotes scale – the GSM community of around 4 billion connections is built based on a single technology being used across all networks and all phones and devices.  This has led to a diverse range of GSM-enabled devices, and massive choice of form factor for the end-user.  Similar principles have driven the movement of HSPA from phones to dongles, and now to be embedded in laptops and consumer electronics.  For a Voice over LTE implementation to continue this model, it must be applicable to the entire LTE industry, and not subject to fragmentation or undue diversity.

Single implementation reduces complexity – when many ways of implementing a single service are deployed into networks, to allow customers to communicate with one another in an interoperable and inter-network fashion is very complex.  Interworking functionality is required which can affect the overall quality of service by inserting delay, potentially being a point of failure and not always guaranteeing the compatibility of the two service implementations.  It is better to have a single implementation that is adhered to by all so that messages and media flow smoothly from one customer to another, wherever those customers are and whoever they happen to be a customer of.

Single implementation enables Roaming – the GSMA has long held a role in defining the way in which Roaming takes place in the mobile telecommunications world.  For Roaming to work, every device must implement the interfaces between itself and the network it is trying to connect  to in exactly the same way.  Similarly, every network must accept devices that are attaching to it because of the common implementation of interfaces between the two entities.  This only happens when everyone adheres to a single common standard.
By taking these principles as its bedrock, GSMA VoLTE will develop the function and technical definitions for the way in which Voice and SMS will work in the future, and will define the interfaces for an end-to-end calling structure that will take into account interconnect and roaming (see diagram).

By taking these principles as its bedrock, GSMA VoLTE will develop the function and technical definitions for the way in which Voice and SMS will work in the future, and will define the interfaces for an end-to-end calling structure that will take into account interconnect and roaming (see diagram).

This is comprised of three sets of interfaces

• The User Network interface (UNI) between the customer’s equipment and the operators network.
• The Roaming Network Network Interface (R-NNI) between the Home and Visited Network of a subscriber that is not attached to their normal Home network.
• The Interconnect Network Network Interface (I-NNI) between the networks of the two parties making a call.

The work of GSMA VoLTE will also encompass

• The continuity of Voice calls when a customer moves from LTE coverage to an area where LTE coverage is not available (this is achieved through Single Radio Voice Call Continuity, or SR-VCC).
• Optimal Routing of bearers for Voice calls when customers are Roaming.
• The establishment of commercial frameworks associated with Roaming and Interconnect for services implemented using VoLTE definitions
• Capabilities associated with the model of Roaming Hubbing.
• A thorough security and fraud threat audit

If you would like to learn more about GSMA VoLTE, express your support for the VoLTE initiative and find out how to get involved in the work please e-mail [email protected].

Players to watch

Qualcomm

Ericsson

Samsung

Alcatel Lucent