No IMS, how?

As word spreads that NewPace has an RCS-e solution that doesn’t require an IMS core we are frequently running in to the question of how our service operates.  The IMS vendors have done a great job of convincing everyone the only way you can run a SIP application on a mobile network is inside their infrastructure.   SIP is an IP protocol, just like HTTP, SMTP, POP etc., all of which run now in mobile networks without IMS components.

We're using Digest Authentication, as allowed in the RCS-e specification, instead of GIBA since the network operator may not have the required components in place to do GIBA authentication. If that support is in place, we can switch to GIBA-based authentication (such that clients are essentially authenticated before they get to us and we don't have to take the extra steps required for Digest Authentication). Otherwise all of the traffic is IP-based and can be routed as such by the network.

All of the SIP signalling between the client and the network is exactly as it would be if an IMS core were in place. If an operator decides to migrate our solution "in-house" there will be some configuration changes to the applications to change the signalling routes, but there will be no real changes from the client perspective.

Authentication, Authorization and Accounting (AAA) is handled through two components we call the “Account Server” and the “Reporting Server”.  The Account Server provides an interface point between a mobile operator’s existing OSS/BSS (in place of the IMS HSS) and we customize the protocol for each customer’s unique interface as required. The Reporting Server generates Charging Data Records (CDR) in the format required by the customer’s accounting systems.

As you can see, through careful encapsulation of functionality and proper software design, it is possible to create an RCS-e service without all of the complexity of a full IMS network.

-- Gavin