This white paper provides a summary of the MultiService Forum's (MSF) Global LTE Interoperability event which took place from March 15-30, 2010.

The LTE Interoperability Event is designed to test standards compliance of Evolved Packet Core network scenarios of interest to major Service Providers, and to gauge vendor support for this technology. Building on the success of previous Global MSF Interoperability (GMI) events, the LTE Interoperability event provided the first global "real network" multi-vendor trial of the Evolved Packet Core infrastructure. Incorporating the Evolved Packet Core defined within the Third Generation Partnership Project (3GPP) Release 8 (R8) standards, the MSF architecture introduced new access tiles to support LTE access and non-3GPP (specifically eHRPD) access to EPC. The IMS core network provided the application layer for which services may be deployed, and the binding of Quality of Service utilizing the Policy and Charging Control (PCC) for the bearer.

The event demonstrated that most of the defined LTE/EPC interfaces were mature and interoperable; however limited backwards compatibility between different implementations of 3GPP Release 8 specifications did create some issues. The fact that 3GPP does not require backward compatibility is a known limitation, but it is important to understand that this is limiting interoperability with commercially available equipment. Service providers will need to factor this into vendor selection.

Highlights of the event included:

- Sessions were successfully established via LTE access to EPC, with creation of default and dedicated bearers with appropriate Quality of Service applied.
- An end-to-end IMS Voice over LTE session was also successfully demonstrated.
- Access to the EPC via a simulated eHRPD access was successfully tested.
- Handover between LTE and eHRPD,
- Roaming was successfully tested.

Though the essential standards are reasonably mature, the implementation of early versions of the standards within several of the available implementations of network nodes highlights the problems that can arise due to non-backwards compatibility between 3GPP releases. It is also clear that early implementations have focused initially on development of LTE access to EPC and that support for legacy access (2G/3G) to EPC is somewhat behind. Events such as the MSF LTE Interoperability event highlight these issues and prove the validity of the MSF approach to achieving multi-vendor interoperability.

Source: MSF