Interoperability in the Real World, Part 2
August 10, 2007
By Oren Libis
Last time, I tried to explain my view on the GCF test cases. As these are test cases that you need to pass before deploying your product (by going to GCF test labs), no matter how farfetched they are, you need to handle them. But there are another important interoperability issues that the GCF doesn’t handle. These are the real deployments out there today.
There are a large and growing number of 3G handsets out there and they are coming from several handset vendors. Each one has its own behavior and quirks. You’d be amazed how much effort it takes when you develop a 3G-324M stack to handle all of these quirks and how much you need to invest on the codec level and application level to get things done right.
Difference in behavior
This difference in behavior happens due to the complexity and richness of 3G-324M. Granted – it does only a video call, in a straightforward enough scenario, but the amount of options that this single scenario has is almost unlimited:
- It supports multiple types of codecs each with its own set of configurable parameters
- There are H.245 messages flowing
- Media quality needs to be handled differently by the various media systems out there
- Different developers have implemented 3G-324M, each one understanding the standard in his own way
Server side equipment
There are also servers on the network. These most of the time are using circuit switched networks in front of the handsets, where they are running 3G-324M, but they are also using IP based standards such as H.323 and SIP on the network side, when interacting with media servers for example. They have a different kind of behavior than handsets and they have a different decision making processes designed into them, bringing in more interoperability issues to bear.
What do you do?
The most important suggestion I can give developers of 3G-324M products is to do the GCF test cases that they must in order to get validated, but to focus and invest a lot on the handsets and servers interoperability. Try to get your hands on as much information as possible during your development regarding the differences in behavior of the handsets and servers and make sure you test against as many handsets as possible before you try to deploy your product through an operator.
Technorati Tags: 3G-324M, WCDMA, Interoperability, GCF, Oren Libis
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Interoperability in the Real World
July 23, 2007
By Oren Libis
Managing interoperability for 3G-324M is not easy if you are a handset developer. There’s a lot to be done and some of it doesn’t always make sense.
What happens when a handset manufacturer finish developing and testing his 3G handset and wants to go sell it through an operator?
This seems like a straightforward enough process: you take the handset, you make sure you test it properly in your labs with a professional QA team and you’re done. That may be the case for things long supported by 3G handsets, such as audio calls over GSM or sending SMS messages, but for 3G-324M this is usually a bit more complex.
3G-324M testing has several different test phases: there are the IMTC, which does interoperability events – and publishes test cases, you have the GCF test labs, which validate handsets using a subset of the IMTC test cases, and then you have handsets and servers that are already deployed.
I have been working for a long time now with handset manufacturers and I have come to the conclusion that sometimes the focus is on the wrong kind of tests.
It might take a bit of time, so let me start by focusing on the GCF.
Take the GCF selected test cases for example. Since most of them are important when you validate your handset – they are all mandatory. But from analyzing them closely you can easily split them up into 3 distinct groups:
- Important test cases
- “Nice to have” test cases
- Unnecessary test cases
I’ll give an example of each. By the way, as the GCF test cases are simply references to the IMTC, you can find all of these test cases here, separated into two distinct documents: interoperability and compliance.
Important test case
An example of an important test case is test case 54. It deals with master slave conflicts – a situation that is common when you have a call between two handsets from different vendors. A few years ago, a lot of handsets on the market and those developed by IMTC companies were unable to pass this test case. As this one deals with a plausible and common scenario, it is important to test it.
“Nice to have” test case
A “Nice to have” test case is test case 47. It checks to see if a handset is capable of accepting a change in media transmission rate because the other terminal/server requested him to do so. I have never quite seen this kind of a scenario happen in real life (it might, I just never saw it). You can take my word for it that this procedure is not that necessary and effective when video is presented on a small screen like the one used in 3G handsets. So this is a “nice to have” test case in my view – it’s a good enough feature, but the problem it comes to fix is just not there most of the time.
Unnecessary test case
An unnecessary test case is test case 45 (and 45u). In this test case, you need to respond to a RequestMultiplexEntry message – either by acknowledging it and sending the entry’s information or rejecting it. If someone is sending it to you, it means that he is already in a lot of trouble, as he didn’t remember what you told him (there are only 16 entries, so this must make him a senile). Let’s assume you reject it – this makes him unable to do a thing about it but drop the call. So we have a test case where the one you are working against is faulty/senile – you choose, and you can decide you don’t support this feature, hence causing a disconnection (and you are still validated by the GCF!). I have never seen a real handset acting in this kind of a way when the terminal he was working against was doing his part of the job. This means that developers need to handle this test case (and a few others similar to it) although their handsets will never actually be in this scenario.
Distinguishing between the different test cases is not easy and requires some knowledge in 3G-324M and in what different products, both handsets and server, are doing. At the IMTC’s 3G-324M Activity Group each company gets to work against a large variety of companies and products with the actual QA and development teams of these companies. This provides important information that can assist any handset vendor to pass his interoperability tests once he gets to that point.
Technorati Tags: 3G-324M, WCDMA, Interoperability, IMTC, GCF, Oren Libis
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3G-324M - From Connectivity to Services
June 26, 2007
By Oren Libis
Today, 3G-324M is used for video telephony and it is deployed in Europe and Asia, and many many handsets. China is now joining the bandwagon as well, with their TD-SCDMA network.
At the IMTC, we have been covering the adoption of 3G-324M over the last several years, especially from the point of view of the handset. This includes interoperability testing between two points, each running 3G-324M. During that time, we focused on making sure that channels are opened properly, and that video codecs are negotiated reasonably. From there, we moved on to handling call setup time. Along the way, other technical issues were dealt with and solved.
Today, I feel confident that the technical issues of video calls between two handsets are solved. The level of interoperability we have achieved within our group is high. I am also quite impressed by the level of interoperability that the newest addition to the standard – H.324 Annex K (also known is MONA) enjoys. I had my doubts, but during the last SuperOp! event on April, I was able to interoperate quite well with several vendors – no small achievement for a new specification that several companies are implementing independently.
And this led me to think about what’s next in store for our Activity Group. 3G-324M is relatively limited. You can use it to open multiple multimedia channels between two points, and this is mainly used to execute video telephony calls. You can try adding text, adding more codecs or trying to increase the bandwidth, but I believe the next challenge for the 3G-324M AG will be services.
As 3G-324M is used by operators to offer interactive video services to customers, our primary concern should be making sure that 3G-324M is as flexible as possible for services. We already have basic calls up and running well. But there are other technical aspects that didn’t get as much attention as they needed. Deploying a video ring-back tone service, for example, is a technical challenge due to the way 3G-324M is defined. This is an issue that makes the deployment of such a service so expensive to operators. From my conversations with service providers, I believe that there are a lot more services that subscribers would like, but we don’t handle well enough. So we have our work cut out for us.
If you are an operator or if you are in the business of developing services for operators, I suggest you join the IMTC 3G-324M Activity Group. The time has come to make 3G-324M services a reality.
Technorati Tags: 3G-324M, ITU, MONA, Oren Libis, TD-SCDMA, WCDMA
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TD-SCDMA Video Telephony and Interoperability
June 15, 2007
By Oren Libis
In the IMTC 3G-324M Activity Group we handle interoperability for video telephony. The companies participating in this group focus on WCDMA, though other networks can be easily supported as well.
Recently, we have noticed that China is working more quickly on building its TD-SCDMA network building – most probably because of the Olympic Games planned for next year. TD-SCDMA also enables use of 3G-324M for video telephony like WCDMA – you get a 64kbps circuit switched connection in both directions of your call and you use it to transmit H.324 bit streams.
If we try to predict what’s in store for the TD-SCDMA industry, it seems like the IMTC can offer a lot to China in terms of experience with 3G-324M interoperability. We know the companies, the technology, and the facilities that test video telephony. We handled standardization when it was required and have seen more and more products conform to the 3G-324M standard and improve interoperability.
As TD-SCDMA embarks on its first steps as a live network, I am sure that vendors will face the same interoperability problems that we faced in the beginning of WCDMA. But this time, there are lessons to be learnt from our experience developing and deploying WCDMA handsets and services. My feeling is that interoperability between TD-SCDMA and WCDMA is also important.
I would like to invite all TD-SCDMA vendors out there to join us in the IMTC. Benefit from the vast experience we have accumulated and be part of our efforts to promote the use of 3G-324M in mobile handsets. There’s a lot of work to be done. We’re here to help.
Technorati Tags: 3G-324M, Oren Libis, TD-SCDMA, WCDMA
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