This blog post was written by Wayne Cutler, Interoperability Solutions Director (Networks) and Product Manager for the GSMA Interoperability Testing Service.
While VoLTE is now widespread and commonly deployed, a significant majority of mobile network operators are yet to launch it, and VoLTE Roaming is lagging behind further still. At the time of writing, there are 717 LTE networks launched globally across 230 markets. Of those LTE networks, 232 have also launched VoLTE in over 106 markets. Of the 232 VoLTE network operators, around 50 have also launched VoLTE Roaming.
VoLTE and spectrum refarming
With the advent of 5G came the need to re-farm existing 2G and 3G spectrum to make way for new 5G services. This can only be done when legacy 2G/3G services have been replaced by alternative options. For voice telephony, this means replacing 2G/3G based voice with VoLTE. There is therefore a pressing need for both VoLTE and VoLTE Roaming deployments to be significantly increased in order to replace legacy voice services and retire obsolete network equipment.
OEM locking and smaller operators
One of the biggest issues facing operators looking to launch VoLTE is that of ‘OEM locking’ whereby a device inhibits its VoLTE functionality for networks with which it has not performed 1:1 testing. The device checks the network identity of the SIM card to see whether the network is on its approved/tested list or not. This action is taken to protect against reputational damage to the OEM in the event of the VoLTE experience being poor due to interoperability issues with the network. This locking typically impacts on smaller (non-Tier 1) operators and is exacerbated by the fact that such smaller operators often do not have the resources, and cannot access all the relevant devices, to conduct 1:1 testing on their network.
GSMA Interoperability Testing to mitigate OEM locking
Based on recommendations made by the GSMA Networks Group and documented in PRD IR.25, the GSMA has recently launched a VoLTE interoperability testing service. It enables testing of devices and networks both individually and in combination and covers both non-roaming and roaming scenarios. Four different tests are offered :-
- Network Test
- Network Roaming Test
- Combined Network & Device Test
- Device Test (specifically for OEMs)
The testing focusses on IMS settings and the related configuration parameters as defined in GSMA PRD TS.32. The settings are uploaded by the network operators to the GSMA Network Settings Exchange database in order to facilitate quick and secure sharing with the world’s device manufacturers.
Network Tests are carried out using the preferred IMS settings of the network (‘IMS Profile’) whilst devices are tested against six different IMS profiles that have been defined by the GSMA Networks Group to generically test the IMS / VoLTE functionality of the device.
Successfully tested networks and devices will be listed on the GSMA Interoperability Testing results page and communicated to GSMA Network Settings Exchange subscribers so that both parties (MNOs and OEMs) can publicly communicate their compliance, thereby instilling confidence within the industry and reducing any requirement for OEM locking.
GSMA PRD TS.59 and Open Market Devices
The device manufacturer community of the GSMA Terminal Steering Group has published TS.59 (‘Device Type Naming Requirements’) which defines an Open Market Device (OMD) as “neither a Non-Operator Locked Device nor a SIM/USIM Locked Device and has software intended for use on the network that supports any of the GSMA Service Profiles that the device also supports”.
TS.59 is applicable where ‘devices and networks have obtained GSMA certification of compliance with IR.25’ and therefore, a TS.59 compliant OMD shall not lock the IMS capabilities when a network has:
- been successfully tested against the standards documented in PRD IR.25
- uses an IMS Profile already tested/supported by the device
Any operator wishing to mitigate OEM locking should therefore ensure that its network is tested by the GSMA and should select an IMS Profile likely to be supported by OEMs. This implies that network operators that have yet to launch VoLTE should :-
- select one of the six IMS Profiles defined by the GSMA Networks Group, or
- should replicate the IMS Profile of a larger, neighbouring operator i.e. a “regional profile”.
Successful testing of a network via GSMA Interoperability Testing (and the promotion of these results to the industry) and use of a common IMS Profile in conjunction with TS.59 guidelines, enables OEM locking to be mitigated without the need for bespoke 1:1 testing between a network and TS.59 compliant OMDs. Such mitigation will instill confidence in the industry and facilitate the roll-out of additional VoLTE deployments.
If you would like to find out more about GSMA Interoperability Testing, please get in touch here.