Older blog entries for LaForge (starting at number 227)

Update on what I've been doing

For the better part of a year, this blog has failed to provide you with a lot of updates what I've been doing. This is somewhat relate to a shift from doing freelance work on mainline / FOSS projects like the Linux kernel.

In April 2011, Holger and I started a new company here in Berlin (sysmocom - systems for mobile communications GmbH). This company, among other things, attempts to provide products and services surrounding the various mobile communications related FOSS projects, particularly OpenBSC, OsmoSGSN, OpenGGSN, but also OsmocomBB, and now also OsmoBTS + OsmoPCU, two integral components of our own BTS product called sysmoBTS.

Aside from the usual software development, this entails a variety of other tasks, technical and non-technical. First of all, I did more electrical engineering than I did in the years since Openmoko. And even there, I was only leading the hardware architecture, and didn't actually have to capture schematics or route PCBs myself. So now there are some general-purpose and some customer-specific circuits that had to be done. I really enjoy that work, sometimes even more than software development. Particularly the early/initial design phase can be quite exciting. Selecting components, figuring out how to interconnect them, whether you can fit all of them together in the given amount of GPIOs and other resource of your main CPU, etc. But then even the hand-soldering the first couple of boards is fun, too.

Of all the things I so far had least exposure to is casing and mechanical issues. Luckily we have a contractor working on that for us, but still there are all kinds of issues that can go wrong, where unpopulated PCB footprints can suddenly make contact with a case, or all kinds of issues related to manufacturing tolerances. Another topic is packaging. After all, you want the products to end up in the hands of the customer in a neat, proper and form-fitting package.

On the other hand, there is a lot of administrative work. Sourcing components can sometimes be a PITA, particularly if even distributors like Digikey conspire against you and don't even carry those low quantities of a component that we need for our 100-board low quantity runs. EMC and other measurements for CE approval are a fun topic, too. I've never been involved personally in those, and it has been an interesting venture. Luckily, at least for sysmoBTS, things are looking quite promising now. Customs paperwork, Import/Export related buerocracy (both in Germany as well as other countries) always have new surprises, despite me having experience in dealing with customs for more than 10 years now.

Also significant amount of time is spent on evaluating suppliers and their products, e.g. items like SIM/USIM cards, cavity duplexers, antennas, cables, adapters, power amplifiers and other RF related accessories for our products.

The thing that really caught me off-guard are the German laws on inventory accounting. Basically there is no threshold for low-quantity goods, so as a company on capital (GmbH/AG) you have to account for each and every fscking SMD resistor or capacitor. And then you don't only have to count all those parts, but also put a value at them. Depending on the type of item, you have to use either the purchasing price, or the current market price if you were to buy it again, or the price you expect to sell the item for. Furthermore, the trade law requirements on inventory accounting are different than the tax laws, not often with contradictory aims ;)

In the end it seems the best possible strategy is to put a lot of the low-value inventory into the garbage bin before the end of the financial year, as the value of the product (e.g. 130 SMD resistors in 0402 worth fractions of cents) is so much lower than the cost of counting it. Now that's of course an environmental sin, especially if you consider lots and lots of small and medium-sized companies ending up at that conclusion :(

So all in all, this should give you somewhat of an explanation why there might have been less activity on this blog about exciting technical things. On the one hand, they might relate to customer related projects which are of confidential nature. On the other hand, they might simply be boring things like dealing with transport damage of cavity duplexers from china, or with FedEx billing customs/import fees to the wrong address...

Overall I still have the feeling that I was writing a decent amount of code in 2012 - although there can never be enough :) Most of it was probably either related to OsmoBTS, OpenBSC/OsmoNITB or the various Erlang SS7/TCAP/MAP related projects. The list of more community-oriented projects with long TODO lists is growing, though. I'd like to work on SIMtrace MITM / card emulation support, the CC32RS512 based smartcard OS, libosmosim (there's a first branch in libosmocore.git). Let's hope I can find a bit more time for that kind of stuff this year. You should never give up hope, they say ;)

Syndicated 2013-02-08 01:00:00 from Harald Welte's blog

Back from FOSDEM 2013

As (almost) every year, I attended the annual incarnation of FOSDEM. It is undoubtedly (one of?) the most remarkable events about Free Software in existence. No registration, no fees, 24 tracks in parallel, an estimated 5000 number of attendees. I also like that it brings together people from so many different communities, not _just_ the Linux or Gnome or KDE or Telephony or Legal people, but a good mixture of everything.

I have to congratulate the organizers, who manage to pull this off, year after year again. And as opposed to many other events, they do so quietly and without much recognition, I feel. I'd also like to thank the many volunteers working tirelessly before, at and after the event. Last, but not least, I'd like to thank the local university (ULB Solbosch) hosting the event.

What made me truly sad though, is the amount of littering that surprisingly many of the attendees did. This was particularly visible in the Cafeteria. Imagine an event run by volunteers, who put in a lot of time and effort. Imagine an event where food and drinks are sold by volunteers at such low prices that there can barely be any profit at all. And then imagine people eating there and leaving all their rubbish around, as if they were in some kind of restaurant where they are being served and where somebody is cleaning up after them. It really makes me feel very bitter to see this. Don't people realize that those very volunteers who are creating the event will then have to put in _their_ spare time just because those who just enjoyed their coffee or lunch didn't have the extra 30 seconds of bringing their trash to the trashcan? I feel ashamed for members of our community who behave this way. Please think next time before acting and show your respect to the people behind FOSDEM.

Syndicated 2013-02-04 01:00:00 from Harald Welte's blog

Why I hate phone calls so much

The fact that I have more than 20 missed phone calls on my land line telephone after only half a day has passed triggers me to write this blog post.

It is simply impossible to get any productive work done if there are synchronous interruptions. If I'm doing any even remotely complex task such as analyzing code, designing electronics or whatever else, then the interruption of the flow of thoughts, and the context switch to whatever the phone call might be about is costing me an insurmountable amount of my productive efficiency. I doubt that I am the only one having that feeling / experience.

So why on earth does everybody think they are entitled to interrupt my work at any given point in time they desire? Why do they think whatever issue they have rectifies an immediate interruption in what I am doing? To me, an unscheduled phone call almost always feels like an insult. It is a severe intrusion into my work-flow, and has a very high cost to me in terms of loss of productivity.

Sure, there are exceptional absolute emergencies (like, a medical emergency of a family member). But just about anything else can be put in an e-mail, which I can respond to at a time of my choosing, i.e. at a time I am not deeply buried into some other task that requires expensive context switching and the associated loss of productivity. And yes, a response might be the same day, some days later, or even a week or more later. There are literally hundreds of mails of dozens of people that need to be responded to. I can never even remotely answer all of them in a timely manner, even if I'm working 12-14 hours a day up to 7 days a week.

Right now I'm doing the only reasonable thing that is left: Switch off all phones. And to anyone out there intending to contact me: Please think twice before calling me on the phone. Almost anything can be put in an e-mail. And if you really want to have a phone call, please request a scheduled phone call in an e-mail containing a very detailed agenda and explanation of the topic.

Syndicated 2013-01-16 01:00:00 from Harald Welte's blog

Strain of bad luck

From roughly September to December 2012 I seem to have had a quite unusual strain of bad luck and set-backs. I don't want to go into the details here, as most of the issues are of quite private nature.

This has kept me quite distracted from a lot of my other activity. Projects like the various Osmocom sub-projects, gpl-violations.org are in desperate need of attention, and I have severely neglected my responsibilities in the Chaos Computer Club Berlin e.V. :(

I don't even want to talk about actual paid work, where customers also had to put up with repeated schedule slips and lack of availability.

I let down friends and colleagues at a number of occasions, as I was unable to keep up with anything that remotely resembles my typical work schedule.

Last but not least, I regrettably have also not felt much of an urge to write many blog posts here.

My sincere hope and expectation is that things are going to improve quickly in 2013. At least most of issues from the last half year have been resolved. Now I need to work through a considerable back-log of work and find more time for my volunteer projects in the FOSS and hacker worlds. However, this will need some time and I would like to ask for some patience. I do intend to be up to speed with things just like before.

In this spirit, I am looking forward to a productive and exciting 2013. Happy hacking und Viel Spass am Gerät

Syndicated 2013-01-02 01:00:00 from Harald Welte's blog

29C3. The end of an era?

When I first heard that the annual CCC congress was moved to Hamburg, my immediate reaction was: Fine, but I wouldn't want to be involved in it. For the last 15 years I've been attending the CCC congress every year, in most years as a speaker, and in many years in some (small) contributing role, first in the team doing the video recordings, and in the last couple of years setting up a GSM network. Contributing to an event is easy if your home/lab is within 20minutes, so if you need another strange cable/adapter/tool/whatever, you can just go and grab it. Doing that at an event that's multiple hours of driving away, in a new/unknown venue is an entirely different story. I have more than enough stress already with (paid) work and the various FOSS projects that I'm leading or involved in.

I have no interest in "just" attending the event. That never was a primary reason for me. In all those years, I've probably attended an average of one talk each year. The event for me was about being able to contribute something actively.

Now, months after those thoughts and my decision not to attend, there is a schedule for the 29C3 available. And to say the least, I am shocked. The entire event seems to have turned into a SIGINT, rather than an xxC3. Lots of talks on politics and society, and lots of German talks.

The debate on implications of technology on society, culture, politics, etc. is an important debate, there is no doubt. And so far I always had the feeling that the xxC3 had a pretty good balance between hard-core technical talks and those non-technical talks. But if I look at the schedule this year, it really looks like an incarnation of the SIGINT conference. With too many German talks you are scaring off the international community. And with focussing on non technical topics, you scare away the die-hard technical hackers. So why move to a larger venue, if you at the same time seem to limit the scope of the event?

Meanwhile I have heard of a number of friends and colleagues who seem to share this view. A number of people who have attended in previous years are not interested in attending this year due to the issues mentioned above.

It's sad to see, but I somehow have the feeling that 29C3 might be the end of an era. The end of a highly successful series of events with exceptionally strong technical talks. To me, xxC3 has always been unique and special. No other event would ever compare to it. Who will fill the gap for the die-hard technical topics? I am feeling quite sad, up to the point that I want to start mourning about "the good old times".

I'm not writing this to put blame on anyone. It just reflects my personal and highly subjective view. Let's see what people will say after 29C3 has actually happened. Let's see how successful it is in terms of number of attendees, and in terms of feedback from participants.

Syndicated 2012-12-18 01:00:00 from Harald Welte's blog

Inside a cavity duplexer

In many cellular systems (GSM or otherwise) there is a frequency duplex between the uplink and downlink frequency band. If you use a single antenna to serve a BTS, then somehow you need to split the frequency band between the Rx and Tx side by means of a Duplexer.

The most common technology for this is the so-called Cavity Duplexer. I've used those devices (and seen them in use) for a long time, but never really opened one so far. The problem is that they are finely tuned, and each mechanical change can severely impact performance. As I had to repair a broken SMA socket on one of them recently, I took the chance to take a picture

In the first picture you can see the bottom side. This consists of a milled aluminum block, with a series of circular cavities. The Tx output of the BTS is connected to the SMA socket on the bottom right, the antenna to the SMA socket on the top side, and the Rx port to the SMA socket on the bottom left of the picture:

The small cylindrical objects in the center of the cavities are not milled from the same part, but they are separate pieces mounted by screws from the bottom of the unit.

The second picture shows the top section of the duplexer:

You can see a ~ 4mm aluminum plate with lots of (now empty) holes which are for the ~ 117 screws with which the top plate is screwed against the bottom part shown in the first picture.

The important part, however, are the screws that you can see sticking out of the top part. Those are used for tuning and present "obstacles" in the path of the waves as they pass through the cavities.

The big miracle for me is not that there are some resonances which build up a filter, but that you can actually transfer as much as 100W of RF power from the Tx input through to the antenna output.

Syndicated 2012-11-22 01:00:00 from Harald Welte's blog

Short report on the first Osmocom User Group meeting in Bavaria

It's already one week in the past, but I'm only now finding some time to report on the first Osmocom User Group meeting in Bavaria.

All-in-all, there were 6 people attending, some people already known in the community, but also two completely new faces, which is great.

Dieter gave us a tour of his large BTS equipment, including a Nokia Ultrasite and an Ericsson RBS 2206. We had an introduction round where the participants could get to know each other a bit. Finally, we spoke about a variety of topics, from OsmocomBB to SIMtrace, SIM/SAT/STK security, the CC32RS512 and of course OpenBSC and the sysmoBTS.

On the day after the meeting I also had the pleasure of attempting to get the RBS2206 working with OpenBSC. Unfortunately there was no success, but still a number of bugs in the OM2000 / RBS2000 code in OpenBSC that had been found and fixed.

I'd like to thank Dieter Spaar for organizing and hosting the event, taking care of the Bavarian sausage + cheese platter for lunch.

Syndicated 2012-09-08 02:00:00 from Harald Welte's blog

I did not create rtl-sdr / librtlsdr

In recent weeks, the number of private e-mails I receive about rtl-sdr has increased significantly. This is odd for at least two reasons:

First, I didn't create rtl-sdr and was not involved in its creation with the tiny exception of writing an e4k tuner driver for osmo-sdr, which was then used in a variety of rtl-sdr software.

Second, you should never contact the (presumed) software author in a private e-mail, but use the respective project mailing list. There is a community of developers, contributors and users out there, and it is a waste of everyone's time if you communicate by 1:1 private e-mail rather than enlightening the mailing list.

Syndicated 2012-09-07 02:00:00 from Harald Welte's blog

We're now working on a UMA/GAN controller

We've pondered it a couple of times in the past whether we should implement an UMA/GAN controller (UNC/GANC). GAN (formerly called UMA) is a method by which you can tunnel GSM/3GPP Layer3 signalling (Mobility Management, SMS, Call Control) over an IP based bearer such as 802.11 (WiFi).

The idea was that mobile phones that support both a GSM/3G radio as well as WiFi could then simply use WiFi to connect to their mobile operator. This has been deployed around 2007/2008 by some operators such as T-Mobile USA as well as Orange UK. Today it seems that not many operators have caught up and UMA/GAN is mostly a legacy technology, last but not least due to very few phones actually implementing it.

Nonetheless, there are some markets and applications where UMA/GAN is useful. We (Dieter and I) now have managed to secure a contract for an Osmocom implementation based on OpenBSC (and libosmogsm, libosmo-sccp, ...). The beauty is that from L3 up, it is just regular GSM, no change needed at all. Only the transport layer is different: IPsec with TCP + GAN is the bearer, instead of LAPDm/RSL in classic GSM networks.

Another good part unrelated to UMA/GAN is: This will finally force us to clean up the separation between the MSC and BSC part in OsmoNITB (in order to replace the BSC part with the GANC).

Progress has been good so far, the SEGW (IPsec with EAP-SIM) has been configured, and a simplistic start of a GAN protocol implementation gets us through DISCOVERY, REGISTRATION and up to the point where the MS is sending the LOCATION UPDATE message. If you are curious how the protocol actually looks like, I've attached a sample pcap file to the WRTU54G-TM page in the OpenBSC wiki. The source code can be found in the laforge/ganc branch of openbsc.git.

Syndicated 2012-06-24 02:00:00 from Harald Welte's blog

First month of running the openmoko.org USB Product ID registry

One month ago, I had announced the availability of USB Product IDs under the Openmoko USB Vendor ID. By now, there have been 37 registrations, and the List of assigned USB Product IDs in the openmoko.org wiki is turning into something like a directory of really cool projects with Open Hardware or at least Free Software device firmware.

So actually, I enjoy a lot seeing so much activity in this field, and being able to contribute a tiny bit by enabling people to get a unique USB Product ID that they can use.

Syndicated 2012-06-21 02:00:00 from Harald Welte's blog

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