Today we will start with Online Charging, or Ro interface in our terminology. And because Online Charging is a bit more complex than Offline Billing, we’ll split it into several posts. In this first one we will take a look at so-call Direct-Debiting, which is used mainly for charging of SMS Service.
Perhaps from our Charging Overview you remember that we can use two different approaches to the Online Charging – Session based or Event based. SMS Ro Charging is using Event based mechanism. It is easier than the Session based and we will also need it later to complement the Session based Charging for the Voice service.
The SMS Charging architecture is standardized in 3GPP 32.274, the SMS online charging then uses the Credit-Control application as specified in TS 32.299.
Ro Reference Point for SMS
The Online Charging is triggered over Ro Reference point. It is up to a Mobile Operator if they will signal charging operations from IP-SM-GW, SMSC, SMS Router or any combination of these. Typically the charging requests are sent from SMSC only. For simplicity we will refer only to the SMSC in the following text. SMSC may either directly support Ro interface, or it can use CAP (CAMEL) protocol which is then translated to Ro by an Interworking Function (IWF) as described in 3GPP 32.293.
The SMS charging may use two different models:
Immediate Event Charging (IEC)
Event Charging with Unit Reservation (ECUR)
In this post we will rather focus on IEC, as the ECUR is more complex and in my personal experience it is less common than IEC. The ECUR principle is specified in TS 32.299.
In the last post we talked about VoLTE charging on a high level. This time we will zero-in and focus on a role of Telephony Application Server (TAS) in offline charging during a Voice/Video Call. Charging on the TAS is described in the 3GPP 32.260 and 32.275. The basic charging is fairly simple, but we also have to count with Supplementary Services, Roaming Scenarios and rainy-days scenarios.
TAS Charging, Ro, Rf
We already know that the 3GPP specification requires Network Elements like TAS to provide offline billing so that service providers can collect and correlate charging information from a variety of sources as well as to generate CDRs. An IMS system is composed of many entities that can generate charging events which need to be collated in order to generate a bill for the customer. These elements are referred in our terminology as the Charging Trigger Functions (CTF). The CTF function works in connection with TAS call processing by receiving SIP call events, translating SIP messages into Diameter messages with call parameters copied into 3GPP-defined AVP set, and sending Accounting Request(ACR) messages to the external CDF. The CDF acknowledges the receipt of ACR message by sending back an Accounting Answer(ACA) message indicating success or failure of the operation. The communication between CTF (TAS) and CDF happens over the Rf interface, which uses the Base Diameter protocol.
Charging has been for a long time on my todo list. Now it’s the time and you can expect couple of posts related to charging, mainly Online Charging. Today we’ll go through the most basic stuff. For details refer to 3GPP 32.240.
Charging is a world of its own, it has its own rules, flows and well, also documentation. To really understand how to properly charge your calls, data, or messages is probably the same or even bigger challenge than to understand the actual service.
Charging Specification – source 3GPP 32.240
GSM/UMTS/EPC networks provide functions that implement offline and/or online charging mechanisms on the bearer (e.g. EPC), subsystem (e.g. IMS) and service (e.g. SMS) levels. In order to support these charging mechanisms, the network performs real-time monitoring of resource usage for those three levels in order to detect the relevant chargeable events.
In general we recognize Onlineand Offline charging mechanisms. They may be performed simultaneously and independently for the same charging events.
Support and operation engineers don’t need to understand the majority of algorithms hidden in telecom software. But time to time it helps if you have an understanding of how some particular functionality is implemented.
The typical situation is Traffic Shaping or Overload Protection. Many operators want to understand and test, how their system behaves under a huge load of calls or messages. There are many ways how to implement these features, so let’s take a look at the most common ones.
The easiest way how to protect the system is to define some limit. For example, we can say that our SBC is able to handle only 1.2 mil. parallel calls. If we receive a new invitate which exceeds this threshold, we respond with system error.
Similarly, we can set a limit for CPU or memory consumption. Whenever we reach, let’s say 60 % of the CPU we raise an alarm and don’t allow any new call/registration. As soon as the resource utilization drops below the threshold again, we can resume the standard system behavior and accept new calls.
Sounds reasonable and simple, however, in case that the load is close to our limit – 60 % of CPU – it can lead to so called throttling causing system instability. The last thing which you desire for if you are facing high traffic.
After years in mobile industry with 5G I’ve recently started to be more cautious about health implications. For last 12 months I’m going through various studies and honestly it is difficult to come to any final conclusion. Some researchers claim that there is no evidence cell phones would increase risk of cancer, some argument with studies on rats, where radiation makes rats uniquely prone to a rare tumor called a schwannoma. As a technician it is hard to judge for me, but there are some basic facts, which I’ve noted down:
to call only is not that bad, to use mobile for data is a completely different story
non-ioinizing radiation maybe more harmful than it was thought
studies reveal that the exposure to cell phones, laptops, or Wi-Fi affect sperm in their count, morphology, motility, an increased DNA damage
we don’t have much evidence on mobile induced cancer when it comes to humans
studies are mostly miles behind the current technological development
distance matters – just a few centimeters can make a difference
What would happen if the scientists would actually prove, that 5G can mean a serious risk to us? Many people are so adicted to Internet, that they are ok to pay by their own health anyway. Not talking about all those companies which invested so much into 5G and AR/VR.. Lets’ wait for some clear data and don’t keep cellphones in our pockets till then – just for sure.
GSMA Intelligence forecasts that the number of 5G connections globally will reach 1.3 billion by 2025, covering 40 percent of the world’s population or approximately 2.7 billion people. At that time, the Americas region is expected to account for over 260 million 5G connections or 20 percent of the global market.
The question everyone is asking in telco last couple of years is – do we really need 5G? Do we really need that throughput for our voice, video and messaging services? Can we significantly improve real-time communication services so that customers would be willing to pay for it? RCS aka Advanced Messaging is a great example of how difficult it can be to find the right business model for new technologies. EVS supported in 4G is more than what we need for voice calling. Although video calling is possible in 4G, not that many customers are using this option on their mobile devices. More popular than video is desktop-sharing, collaboration and communication in context. Well, lower latency and better throughput can be useful – but is it a reason strong enough to invest into the new 5G infrastructure, when collaboration applies mainly to fixed networks?
5G Drivers. Source GSMA
Still there are real-time communication applications which require low latency and huge amount of data so that 4G is not enough. Virtual Reality (VR) applications like 360-degree video will necessitate higher resolutions of 8K and above, and stereoscopic video (which separates left and right eye views in VR) also requires additional bandwidth. When most people hear about 3D video, holograms, Augmented Reality (AR) and Virtual Reality (VR), they mostly think about gaming. And yes, gaming can be a good example and people like to spend money for entertainment. But there are other examples, where AR and VR can make a difference.
Impossible not to mention. Ethereal – these days known as Wireshark – is twenty! In 1998 Gerald Combs publicly released its first version 0.2.0. And he truly changed the IT (and particulary telco) world. Over the years Wireshark has won several industry awards,and it is one of the top-rated sniffers. Wireshark is a real gift for every engineer who works with a protocol stack. At the same time many BIG companies don’t even realize what contribution Wireshark means to their daily business!
Thank you Gerald and everyone who has helped with this great project!
So we have a first robot citizen. When we read about human-robots they are presented as future cleaning-ladies, news anchors, soldiers or sex-machines.
Everyone can imagine possible threats. In the current world of spam and fake news robots can manipulate our reality even in a more advanced way. It’s not just a robot shop assistant which – by the way – mentions how great is a new laundry detergent or your joy-robot asking for an upgrade in a (im)proper time. It can also spy what you have at home, how much time you spend with various activities, assess your income or overhear conversation with your spouse – all, of course, in your best interest (let’s call it cookies 2.0). Not talking about real malware and ransomware.
In the same way participants in reality show forget about TV cameras, we’ll forget that robots are just robots. They don’t even need to look very real. Our brain is not that difficult to deceive. So the question is how to protect ourselves. At some point AI outsmarts human brain and we’ll need some help.
Let us know in comments section, what is your view and how to protect ourselves – e.g. how a new antispam sw/hw could look like.
Everyone knows that SIP headers like R-URI, To, From, P-Asserted-Identity, Path, Route and others contain Uniform Resource Identifiers (URI) – sip uri or tel uri. But do you know what formats we can use, with what parameters? As URI is one of the IP communication’s corner stones, it worth to have some better understanding.
SIP URI in VoLTE
Let’s start from the beginning. SIP URI is defined in RFC 3261, TEL URI in RFC 3966 (this RFC defines also modem and fax URL schemes).
SIP URI has a similar form to an email address. It contains typically a username and a hostname, for example firstname.lastname@example.org, where realtimecommunication.info is the domain of a SIP service provider. TEL URI is simply a telephone (landline or mobile) number as tel:+611234567890. It is needed mainly to support CS related scenarios and Mobile Number Portability (MNP). In practice we can see various forms of sip-uris:
Last but not least we have also a SIPS URI, which specifies that the resource is to be contacted securely. For that we use TLS as a transport layer protocol. The format for a SIPS URI is the same, except that the scheme is “sips” instead of sip. Note, that any resource described by a SIP URI can be “upgraded” to a SIPS URI by just changing the scheme, if it is desired to communicate with that resource securely.
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.