By Alfonso San Jose, Sales Consulting Systems Engineer
Now that LTE networks have been rolled out by most of the service providers in the world, the next objective for operators is the migration of the voice service to the LTE network. This migration is known as Voice over LTE or VoLTE.
VoLTE brings the two sides of the same coin. On the one hand, VoLTE is bringing multiple benefits for service providers (spectrum efficiency, high quality voice, OPEX & CAPEX reduction, etc) but on the other hand, VoLTE service is also bringing some challenges. Those challenges have an special impact on the Policy Management solutions currently deployed for Data Services as this node becomes a critical node in the network for VoLTE.
Policy Management plays a significant role in VoLTE and becomes a mandatory node in the network. This node is responsible for establishing and releasing, on behalf of the IMS domain, the bearer required to accommodate voice traffic.
Additionally, VoLTE is defining some stringent requirements for Policy Management solutions.
First of all, VoLTE Service is dramatically increasing the number of transactions (or Diameter requests) to be processed by Policy Management. As a consequence, Service Providers require very high performing Policy Management system and most importantly a solution able to scale in a very cost efficient way involving linear scalability, virtualization, N+1 redundancy, etc.
Secondly, VoLTE requires a very low latency figure (order of 10 ms) in comparison with the latency for Data Services (order of 100 ms). Service Providers require then Policy Management solution able to handle Diameter transactions in a very fast mode even at high TPS (transaction per second) rate.
In the third place, VoLTE requires a fundamental functionality, session correlation i.e. the ability at the Policy Management node to associate a Diameter request from the IMS domain to a Diameter session from the EPC domain. This functionality becomes more and more complex as service providers scale their policy management solutions.
Additionally, the fact that VoLTE is business critical makes Policy solutions increase the level of resiliency and redundancy from an initial High Availability for Data Services to a Geographic High Available solution required for VoLTE.
And finally, the biggest complexity resides in the fact that all these four requirements have to be met at the same time by Policy Management solutions.
Fortunately, Data Services and VoLTE Service allow a clean separation in the network for Policy Management. As a consequence, Service Providers can maintain their existing Policy Management solutions for Data Services and deploy a Policy Management solution specifically for VoLTE. As previously discussed, a Policy Management solution able to meet all those requirements and helping Service Providers solve the challenges introduced by VoLTE.