Finding Your Way on the 3GPP Web Site

As requested last week by a reader, here is a post that will try to help you navigate through the 3GPP web site and its specifications.

The bad news is that 3GPP is a very big and complex standardization body. It usually takes time to understand how it works and to find what you need on the web site.

On the other hand, the good news is that 3GPP is a very structured and formal group. Moreover, all its specifications (including intermediate versions), contributions, and meeting minutes are available to everybody who can find its way to them.

Overview of 3GPP Work Items

In 3GPP, every standardization topic is associated to one or several work items. Each work item is defined in a work item description document (WID), which describes the topic, the reason for it, the companies initially supporting the work item, the 3GPP groups taking part into it, the specifications it will create or impact, as well as a preliminary roadmap.

New topics are proposed to 3GPP as WID drafts, and a certain number of companies needs to agree on a draft and place their name into it as a supporting company in order for the work item to be considered for inclusion in the current 3GPP release.

The 3GPP workplan is a convenient way to have an overview of all the work items, their roadmap and actualized completion status.

Individual WIDs referenced in the workplan are stored here. You can also get information on each there. The WID is a good starting point for your search on a specific topic. More especially, you will know which 3GPP working groups will be involved and the specifications or technical reports they will write.

In 3GPP, technical reports (TRs) are used to investigate a topic or perform a feasibility study. Once the report is completed, it might form the baseline for a Technical Specification (TS), lead to a few sentences added to one, or simply disappear in the void of failed 3GPP standardization attempts. Beware that a TR is interesting only if it is currently being worked on. Past TRs are just there for history and it is more important to look for how they possibly translated into specifications.

3GPP Working Groups

The 3GPP organization is presented here. You can click on each group to have more information.

In the context of IMS, the following groups are the most important.

TSG SA WG1 (SA1 in short) is responsible for producing requirements (stage 1 specifications, TS 22.xxx). The group belongs to operators.

TSG SA WG2 (SA2) defines the architecture (stage 2 specifications, TS 23.xxx). This is the most strategic and political group, controlled by the big Network Equipment Providers and by a few operators.

Other groups define the details of the procedures and protocols: TSG CT WG1 (CT1) is the group specifying SIP aspects and TSG CT WG4 (CT4) is the Diameter/HSS group. These groups are usually less political, and CT1 might even look like an annex of the IETF in 3GPP.

Finally, some groups address specific aspects such as security (SA3) or OSS/BSS (SA5).

3GPP Specifications

You can see the specifications related to each work item in the WID page indicated above. You can also have access to all 3GPP (and ETSI GSM) specifications in this matrix. This page is usually my entry point to the 3GPP web site, and I usually make a search on keywords to find the specifications or reports that relate to the topic of interest. When you click on the specification number, you can access all the past and current versions of the document.

Work in Progress / Contributions

The versions of the specifications (or technical reports) you can access from the matrix may not reflect the latest status of an ongoing activity.

If you want to closely follow an item in progress of analyze the positions of different companies on a specific topic (who is pushing for what? Who is championning this idea? Who is trying to block this item? Is this company active in the discussion?) you need access to the contributions and minutes of the working groups that takes care of the specification or report you are interested in.

To do this, you need to access the meetings of the working groups on the 3GPP FTP server.

Let's take the example of an SA2 meeting (architecture). You need to navigate though SA and then WG2. You then have access to all the past (and some future) meetings on this page.

As I am writing, the latest meeting for which contributions can be accessed is #57 in Beijing.

The agenda is interesting to see all the topics discussed, and more especially the agenda number associated to each of them. In Beijing, most of the meeting was dedicated to the System Architecture Evolution, but you can still find for instance "IMS Emergency" as agenda item 7.3.

The doclist permits to see in a table all the contributions submitted for the meeting, as well as the submitting companies. By screening via the agenda item number, you can find all the contributions submitted for the subject you are interested in.

These contributions are all stored in the Docs subdirectory. Some of the contributions are the ongoing versions of specifications and reports.

Others are Liaison Statements, which are the official way to communicate between 3GPP groups and between 3GPP and other standardization bodies (e.g. OMA, TISPAN, WiMax Forum). Liaison Statements are often interesting to look at.

The most important document to find your way in the meeting is the meeting report. Structured according to the agenda it documents the fate of all contributions (e.g. approved, noted, not addressed), as well as some (limited) feedback on the discussions related to these contributions.

It is not rare that an original contribution undergoes several modifications during the week, before being (hypothetically) approved. You therefore need to track the progress of the one you are interested in, and check which version was finally approved, if any.

More than the minutes themselves, the number and nature of modifications that a particular contribution underwent is the best indication of how disputed it was. And therefore how important it is to the different companies taking part in the discussion. Typically, if a contribution went through 5 successive versions, with the last one changing a single word to the previous, you can assume the discussion was quite tense.

There are some cases where the meeting did not have time to approve the latest version of a contribution. If it is assumed that this one is not contentious (or it is important to progress on this topic) it will be left for email approval.

You may then need to track the status of the contribution in the associated mailing list. Usually, the list of contributions left for email approval is sent out after the meeting, with a deadline. You can then follow email threads to see how it goes.

If you are not familiar with them, you might be surprised by the fact that most 3GPP contributions are short and focused. Often, a coherent idea pushed by a vendor is split in a family of related contributions. The reason is that companies prefer to have parts of a concept accepted in a meeting, rather than seeing everything rejected because of a single contentious aspect.

I hope this information will be of interest to some of you. My experience is that few people are able to efficiently exploit the mine of information accessible from 3GPP. It takes some practice time, but once you got used to it you are a 3GPP master.

The situation is different for OMA. First you need to be a member company to access most of the material. Then, it might the fact that I was formatted by 3GPP, I find the OMA web page very messy and I usually have a hard time finding what I want on it.

Christophe