OpenBSC February 2009

openbsc@lists.osmocom.org

11 participants
22 discussions

Re: First successful voice calls
by Harald Welte 18 Feb '09

18 Feb '09

Hi David, hope you don't mind me Cc'in the list, as other people might find this information useful. On Tue, Feb 17, 2009 at 08:31:53PM -0800, David A. Burgess wrote: > Congratulations!! thanks! > So if you need the channel mode modify, does that mean you're doing very > early assignment? yes, it is the most simple option. commit the TCH early and you don't have to do conflict resolval in the middle of the call setup if you first only have a SDCCH and then want to switch to a TCH but don't have a free one. > It took me a few days to figure that out when I decided to try very early > assignment. I was pretty clear that I have to do CHANNEL MODE MODIFY on GSM 04.08 to tell the MS to switch to voice mode. However, what is a bit weird is that in addition you have to send a MODE MODIFY REQUEST (08.58) packet to the BTS. Plus, the actual channel mode values for EFR are different on 04.08 and 08.58 ;) Why is it weird? Because typically in a case like this, you would send one 08.58 packet to the BTS, with the payload for the 04.08 packet. The BTS would then do the local state change, and send the 04.08 packet over the air to cause the MS state change. This is how it works with many other operations, you almost never have to explicitly talk to both sides separately. > For early or late assignment, started call setup on the SDCCH, I didn't > need that channel mode modify step. I was aware of that, but then you need another channel assignment and a more complex resource management, at least that's what I think. So I went for very early assingment for now. > Are you transcoding, or just copying raw vocoder frames from TCH to TCH? No, I'm not transcoding. But in order to route TRAU frames from one TCH to the other, you already need to do quite a bit of parsing and re-encoding. It's just how they stuff the bits in the TRAU frames, not actually touching any of the voice processing. I think what is useful is to 'outsource' this TRAU frame processing into a separate process. Apart from simple commands like 'map this sub-channel to another sub-channel' it doesn't need much interaction with the actual signalling part. In fact, the relatively high data rates clog the debug log and make it hard to strace OpenBSC for further work on the signalling side. On the ip.access nanoBTS it's even easier. You can directly feed the RTP streams over the loopback device on the BTS, so the voice data naver even has to go to the BTS (unless you want to route between multiple BTS, which I haven't done yet but is very easy with nanoBTS too, in fact the code _should_ already work. What will be interesting is to figure out the actual RTP payload of the ip.access. I've already seen they use RTP payload type 127 and the size of the packets looks like it is one 40-byte TRAU frame per RTP packet. If that is true, I would probably work on E1-to-RTP interworking to route calls between traditional E1-based BTS and IP-based ones. Cheers, -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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build-fix for bs11_config
by Michael Gernoth 18 Feb '09

18 Feb '09

Hi, it seems that the last few commits (starting with SVN revision 308) broke the compilation of bs11_config. As I wanted to take a look at the boot process of my newly delivered BS11, I've just fixed bs11_config to build again and it even seems to work. Find attached my (ugly) patch to fix the build problems. Regards, Michael -- Michael Gernoth Department of Computer Science IV Martensstrasse 1 D-91058 Erlangen Germany University of Erlangen-Nuremberg http://www4.informatik.uni-erlangen.de/~gernoth/

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First successful voice calls
by Harald Welte 18 Feb '09

18 Feb '09

Hi all! Like I just wrot in my blog, I have managed to get the first voice calls between two MS on one BTS working. The Q.931 like call control never really was the problem, and paging as well as RR/MM seems to work very stable all the time. Bigger problems were related to the CHANNEL MODIFY that has to be done on the 04.08 level (for the MS side) as well as the 08.58 side for the BTS side - plus many classic programming mistakes in what used to be so-far untested/unused code. In any case, I have succesfully had voice calls through both the BS-11 as well as the ip.access nanoBTS. There are still lots of things left to be done (e.g. the E1 subslot assignments are still static, there is a big yet-to-be-explained lag on E1 based calls, Motorola phones seem to have compatibility issues, you can call yourself and make your own phone ring, etc). But at least the foundation is working. Regards, [... and it's not even two months too late for the originally planned call demo at 25C3] -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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Re: ip.access protocol reverse engineering
by Harald Welte 15 Feb '09

15 Feb '09

Hi Philippe! On Fri, Feb 13, 2009 at 03:31:08PM +0100, Philippe Langlois wrote: > Can you also upload there some raw packet traces of this ip.access > abis-over-ip ? I'm working on a wireshark plugin, and I'll release traces + the plugin soon. The traces will then be traces of OpenBSC talking to the nanoBTS. The traces I currently have are from a test network, but contain things like IMSI/IMEI numbers which I consider confidential information. By the way: There is currently no wireshark plugin for GSM 12.21 (OML) yet, as far as I can tell. Only 08.58 is there. Anyone interested in working on this? Regards, -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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ip.access protocol reverse engineering
by Philip Lansink 14 Feb '09

14 Feb '09

Hallo, How can i login ? Regards, Philip.

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ip.access protocol reverse engineering
by Harald Welte 14 Feb '09

14 Feb '09

Hi! I've started a page documenting the ip.access A-bis over IP protocol at https://bs11-abis.gnumonks.org/trac/wiki/nanoBTS There are no NDA problems with it, since all information was derived from looking at packet traces. I do not have access to any protocol documentation from ip.access. Regards, -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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mISDN/socket API, B channels and select()
by Harald Welte 10 Feb '09

10 Feb '09

Hi! This seems to solve the mystery that zecke and me experienced yesterday working with the B-Channels on mISDN. Regards, -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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Re: L3proc login password
by Dieter Spaar 07 Feb '09

07 Feb '09

Hello Bjoern, > Can't get logged in to the LMT. > It asks for a password (cambio menu). > "L3proc" isn't working... This is not the LMT COM Port, you have plugged the cable into the wrong port. Besides the LMT COM port, which is close to the E1 BNC connectors, there are several other COM ports which are directly routed to the various microcontrollers. There are some simple debug menues active during startup, but on the LMT port you won't get any reply without sending the correct message first. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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L3proc login password
by Bjoern Heller 07 Feb '09

07 Feb '09

Hi, Can't get logged in to the LMT. It asks for a password (cambio menu). “L3proc” isn't working... tec - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Björn Heller Jabber: tec(a)jabber.hellercom.de

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major rework on the misdn / input plugin side
by Harald Welte 04 Feb '09

04 Feb '09

Hi! I was trying to get the data model right for the TRAU mux/demux handling, and discovered it is about time to re-do the entire 'input' side, i.e. the interface towards the actual E1 link. The main objectives are: 1) ability to deal with multiple BTS on one E1 link 2) ability to easily integrate E1 drivers != mISDN, e.g. zaptel while still keeping most of the E1 related functionality in common code 3) ability to easily add things like Abis over IP later So please stay tuned for some potentially quite big committs in that area during the next couple of days. -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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OpenBSC February 2009