VoLTE Conference Call

Maybe you remember what I said about Group Messaging. That all the RCS deployments would be done faster without this feature. A similar thing we can say about VoLTE Conferencing. Ad-Hoc Multi Party Conference Call (CONF) is one of the basic requirements we have on VoLTE calling. Simply put each VoLTE network has to support conference calling. But to troubleshoot this great functionality can be a nightmare.

Ad-Hoc Multi Party Conference is one of the Supplementary Services supported by Telephony Application Server (TAS) (a dedicated Conference AS is an option too) and it is described in GSMA IR.92, which then refers to 3GPP TS 24.605 and 24.147. Today we’ll take a look at the conference call flow, along with the Mr’ interface between TAS and Media Resource Function (MRF).

Add participant button

Although we talk about conferencing, in fact it’s just a multi-party call. We don’t schedule any conference call for a given list of participants. We can only add additional numbers to an existing call. That’s why we describe the service as an ad-hoc conference. From the mobile operator point of view the conferencing service provides the means for a user to create, manage, terminate, join and leave conferences as well as the ability to update the involved parties. But most of the stuff is truly hidden to the end subscribers.

In general both voice and video conference can be supported, but only the support of audio media is required by VoLTE standard. The maximum number of participants differs network to network, usually it is between 6 and 10. Note, that the functionality is not limited to VoLTE users only, we can add to the call the CS users too.

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News: RTC in 2017

GSMA has just recently published the final numbers for 2017. As expected the last year we’ve seen less 4G deployments than in 2016.

4G Deployments in 2017

The only exception was the RCS. (Btw. GSMA released its Universal Profile Version 2.0 for Advanced RCS Messaging.)

From the population coverage point of view the last year meant a great step forward. Although many developing countries have been still more focused on 3G (4G coverage is on average 35% there), the overall number of 4G coverage increased significantly.

Population Coverage, © GSMA Intelligence 2017

The main reasons for that are:

  • China has achieved 99% coverage in less than three years and it is now 4G-first
  • In India Reliance Jio has beem driving the technological move towards 4G and other operators are following
Technology Migration© GSMA Intelligence 2017

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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.

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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 (VoNR) 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

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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 and standards.

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!

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News: Trends in Telco

I like statistics. Sometimes it can be misleading or data can be hard to interpret. But it can help us when we struggle to see the forest for the trees.

The last two years the IP-based mobile technologies were booming. If you are working with 4G networks you know it well. This year however the number of new deployments decreased significantly (Sep 2017, source GSMA).

IP Deployments Sep-17

Well, there can be many reasons for that. Rather than guessing, let’s have a fun and take a look on how popular are some telco topics on Google in the last 3 years.

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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:

IMS Centralized Services – Overview

Have you heard about the IMS Centralized Services (ICS)? The basic idea is fairly simple. We want to apply services for IMS subscribers, regardless what access network they use. We know that in IMS we can do it for all IP-based access domains. But if the subscriber is accessing through the legacy CS network (e.g. because of a low LTE coverage in her area), we are still triggering the services in the CS Core network … right, unless we have the ICS in place. So ICS enables the IMS services even when one is using CS access for the media bearer.

IMS Centralized Services

The ICS is specified in GSMA IR.64 and 3GPP TS 23.292, 23.237 and 23.216. The scope of the specification includes:

  • Session establishment when using CS access for media transmission for an IMS service
  • Support of Service Continuity
  • Support of Single Radio Voice Call Continuity
  • Access Domain Selection (ADS)
  • IMS control of services where the media is transported via the CS network (e.g. managing of mid-call services)
  •  Service data management

The solution is applicable for UEs with or even without ICS functionality. As the first step all the sessions have to be anchored in the IMS. That is a job for Service Centralization and Continuity Application Server (SCC AS). The SCC AS is on the signalling path for both the originating and terminating services. Using the initial Filter Criteria (IFC), the SCC AS is triggered as the first AS for originating sessions and as the last for terminating sessions.

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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.

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