Multimedia in VoLTE

It’s very interesting (and well, a bit suspicious) that the main focus of most VoLTE textbooks and trainings is signalling. But from the user-point-of-view, it is the voice data, what matters. As an end-subscriber I don’t care about signalling. My only interest is the call quality. But times they are a changin and engineers are asking about how to improve the overall voice-call quality and user experience. Today we’ll go through the basics as jitter, mouth-to-ear delay, packet loss rate or MOS, needed for QoS analysis.

For real-time multimedia we used to have dedicated telephone/radio networks. That has changed and voice/video streams are transported over IP network now.

We should understand that these IP networks were originally designed for data transport. To transport data we prefer the best-effort service model, which allows an easy network scaling and simple routers’ logic. On the other hand we don’t care much if packets arrive in-order or what are the delays between particular packets. We simply wait until we receive a whole file. If any packet is lost, TCP will re-transmit it.

Packets in Data Networks

It’s a different story with the real-time communication services though. RTC applications are less sensitive to packet loss, but they are very sensitive to packet delay. Usage of IP data network as a carrier brings a lot of challenges which have to be addressed by media protocols and network elements.

Continue reading

Advertisements

IMS and 5G

Maybe you have already heard about some features as Dynamical Network Slicing, CloudRAN, Network-as-a-Services, …  Some basic 5G principals we’ll briefly discussed also in this post. However my question is: What will be the change from the real-time communication point of view? What will be the 5G calling look like? Is the IMS (IP Multimedia Services, don’t confuse with International Microwave Symposium) to stay in the operators’ networks?

5G trial deployments – map, © GSMA Intelligence 2017

Seems that at the first stage the change will be less dramatic than when we introduced 4G. 4G was in many ways a revolution, whereas 5G is “only” an evolution. In fact 4G and 5G, at least in the beginning, will coexist and complement one each other. Still 5G will have a big impact on our existing technologies and the way we work with telecommunication networks.

5GS + EPC + IMS

Continue reading

VoLTE Flows and CS Network

Before I’ll finish a new post about 5G I decided to take a break and create a presentation which would complement VoLTE Basic Flows.

Btw. I can’t find the option on slideshare which would allow to update the material .. does anyone know??

VoLTE KPIs

I have never planned to talk about such an operator specific matter as KPIs. But since I posted NEWS: Telco Monitoring I’m receiving many questions related to this topic and I guess we can discuss at least the basic principles.

Inside AT&T’s Network Operations Center by PCWorldVideos

If you have read the VoLTE standards such as GSMA IR.92 or VoLTE Service Description and Implementation Guidelines, you probably noticed that performance monitoring is more or less ignored. And at the same time all operators are asking about it. What KPIs to watch, how, what are the guidelines?

Btw. I always enjoy being in NOC (Network Operation Centre) or war or crisis rooms. Especially during events like NYE. However mostly it is not allowed to take any photos there, so instead I’ve linked some youtube videos showing the scene. Respect to you bros working day and night to keep the network running!

Continue reading

VoLTE Flows – Basics

I’ve just recently changed my job and that reminded me, what it means to start from the beginning again. To help those of you who have just started with VoLTE/IMS I’ve created a short presentation.

Let me know if it works (and maybe one day I’ll find some to make a recording too 🙂 ). Good luck!

Other presentations:

NEWS: Number Portability & ENUM

Even in 2017 the telephone number remains the most universal identifier for real-time communication. And as the word is moving to be All-IP, we have to be able to translate the number into something more meaningful for routing in IP networks. The GSMA organization selected for this purpose the Electronic Number Mapping System (ENUM) and in 2007 released the first version of PRD IR.67.

ENUM based Routing

Moreover Mobile Operators in over 50 countries have to support Mobile Number Portability (MNP). Although for MNP is a great feature for end subscribers, it makes the signalling more complex and costly for the Operators. The MNP is not just a problem for signalling (routing) but also for billing and management of interconnect agreements. Last but not least it can be a significant issue for content and application providers who may not be aware of the change of the operator for a particular user.

Continue reading

SIP Illustrated 5: SIP Session Routing

In the last post we have seen a basic SIP (VoLTE) session. This time we should analyze in more detail, what headers are used by network elements for their routing decisions and how they discover what port and IP to use. In practice that’s what people are not always sure about. They know the flow, order of signalling messages, but when something goes wrong, they are just guessing what could be the reason.

SIP Message Routing

Let’s recap what we have learnt so far. We use loose routing. So if a SIP message contains a Route header, we will use the top most one for the routing. If there is no Route header the routing is done based on the Request-URI, which contains the address of the final recipient. Don’t forget, network elements are able to add and modify the headers. The way how we handle the messages and modify their content within the IMS is described in 3GPP standards.

Continue reading