Building EPC Systems Webinar: Your Questions Answered!

Last week we concluded our second webinar in the Radisys LTE Webinar Series, during which we continue to explore the complex but interesting topic of implementing LTE network infrastructure.

This second session was about ‘Building EPC systems’, and we explored the various technical challenges we face when delivering the LTE Evolved Packet Core; subjects covered included LTE EPC equipment ranging from highly scalable network elements to the converged ‘EPC in a box’ offerings with an entire network in a small form factor.

We appreciated the participation and great turn out, and response to poll questions. Please be sure to see the end of this post to view the entire presentation, as well as listen to the audio of the actual webcast.

With this blog, I would take this opportunity to address some interesting questions received during the Q&A session.

Q: Why must data delay be < 5 ms but signal delay can be 100ms?

Certain applications like voice, video, interactive gaming etc. require low user plane latency; lower the latency/data delay, better will be quality of user experience.

Hence LTE standards define a lower transmission time interval (TTI); user plane latency includes UE processing time, TTI duration (1 ms for LTE), HARQ retransmission and eNB processing delays for RLC/MAC plus ciphering/compression and is budgeted at <5ms.

Control plane latency is measured as the time required by UE to complete signaling transaction to move from idle state to connected state. This includes processing delays at eNB, network delays for message transfer and retransmissions to complete the signaling. This is accounted for at 100 ms.

Q: Why S4-SGSN is not supported in the COM product?

Often the EPC in a box solution over COMe is deployed for specialized applications like military and warfare communications, public safety or government agencies where there is a need for a secure, reliable network supporting internet access but separate from the commercial cellular networks. Due to lack of reliable backhaul, these ‘in a box’ networks offer basic services with minimum external interfaces and need not interoperate with other adjacent networks for mobility etc. and hence can be deployed without the S4 towards SGSN.

However, there could be other specialized applications for such converged networks, e.g. in rural deployments where the S4 might be needed to enable interaction and HO to existing 3G networks and can be supported as specified in the standards.

Looking ahead, next up in this exciting webinar series is “The LTE Service Layer.” This presentation will focus on how end-to-end LTE systems such as Small Cells/eNodeB, EPC, and MRF/IMS elements will have to evolve in order to support LTE services. Be sure to register today!

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