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blosxom


Contact/Impressum

       
Sun, 24 Jun 2012
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.

[ /osmocom | permanent link ]

Thu, 21 Jun 2012
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.

[ /electronics | permanent link ]

Sun, 10 Jun 2012
Back from a 3-day motorbike ride to the central Taiwan mountains

I've wanted to do this for many years, but somehow never managed to do this even back while I was spending a lot of time in Taiwan: A motorbike ride crossing the mountainous center of the island using the Central Cross-Island Highway. This highway is probably not what most people imagine a highway would be like: A narrow road consisting almost entirely only of serpentines with a speed limit of typically 40 km/h. In other words, a motorbiking paradise.

You can enter that highway from the east by starting from Taroko Gorge. In order to get there by motorbike, you take the famous Provincial Highway No. 9 from XinDian via Pinglin to Yilan, which is frequented a lot by Taipei motorbike riders on weekends. The No. 9 further leads along the cliffs of the coast to Xincheng, from where No. 8 starts.

The trip from Taipei to Xincheng is only about 200km, but still you need at least something like 5.30 hours if you want to ride safely. This is once again due to the mountain roads. You can barely see 100m at any given time to the next turn in the road all the way between XinDian and Yilan.

So I stayed one night at the entrance of Taroko Gorge.

Upon arrival I was greeted by the hotel owner with the news that No. 8 had been closed temporarily due to rock fall at km 150.9. That was pretty devastating to my plan, as this road is the only connection in the northern two thirds of the entire island. There is no alternative, except for No. 20, which would have been probably three times the amount of distance (and thus time). However, as it later turned out, the road would be opened for 30 minutes between 6am and 6.30am. So I had to leave at 5.00am in order to safely ride the first 30 km up to the road block. This turned out to be the best thing that could have happened:

  • There was absolutely zero traffic in either direction (the first 25km to Tienshang that are normally full of tourist busses).
  • I was able to witness the sunrise at about 5.40am in the mountains
  • very clear sight, which at other times is not clear at all

So I reached the road block even ahead of schedule and was able to pass as intended.

I continued along the road, and due to the fact that the road was closed again after 30mins, there was close to zero traffic all day on the entire road.

At Dayuling, you can either continue the 8 towards Lishan (but not much further due to repeated subsequent earthquake and typhoon damage), or you an continue along No. 14 A towards Hehuanshan (Mt. Hehuan). I first went to Lishan (a major tea planting region) and back, as due to my early morning start I had lots of time left for detours, to continue towards Mount Hehuan , where the road reaches an altitude of more than 3100m.

I spent the second night in Renai, where I arrived just in time: The first rain drops of a heavy afternoon thunderstorm were falling. In the morning, I was greeted by the following view from my hotel room:

I left again in the early morning, drove through Puli and headed for the Sun Moon Lake. It really is beautiful, as you can see in the following picture. However, it is also over-developed to care for tourists of all sorts, including lots of concrete directly at the lake, and bus-loads full of tourists, Starbucks coffee shops and everything that comes with it.
After two days in remote mountains with little buildings and almost no people, the experience was so shocking that I decided not to circle the whole lake but instead continue down south along No. 16 until it meets No. 3, which I then drove more or less all the way back to Taipei.

The first sixty-or-so kilometers are painful, as they lead through heavily populated areas around Nantou and Taichung. This means that there's lots of traffic, and very frequent traffic lights that make you stop. Later on, the road leads through less populated mountainous regions, and driving is more relaxed again.

Having managed this trip without any problems (nor getting lost even once), I'm hoping to find some time in the future to ride No. 7 from Yilan to Lishan, and particularly Provincial Highway No. 20, crossing the mountains much more south.

And if there's one part for me to remember: Always avoid the densely populated regions in the west of the island. If I wanted to ride stop-and-go all day long, I don't have to leave Taipei or New Taipei City in the first place ;)

[ /personal/taiwan | permanent link ]

Getting woken up by an earthquake...

...is a good adrenaline rush to start your day. Happened to me this morning at 5am in Taipei, caused by a Magnitude 6.5 earthquake 70 km off Yilan on Taiwans east coast. If it happened two days earlier, it would have caught me on the motorbike ride, possibly causing even some more road blocks due to rubble coming down from mountains.

[ /personal/taiwan | permanent link ]