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4317 discussions

OpenBSC should now have full support for BS-11 with two TRX
by Harald Welte 29 Jul '09

29 Jul '09

Hi! Please note: =========================== commit d46299da00f923b24043aa37fa2bae17ffcc1ff7 make channel allocator policy multi-TRX aware For now, we assume that TRX1 (and higher) all have a TCH/F configuration on all of their timeslots commit 67b4c30a9de972d199830bba5535e934bd47ac0f complete TRX1 support for BS11 * remove old HAVE_TRX1 definition, replace it with '-1' commandline argument * make sure we actually configure the OML TRX attributes with a different ARFCN than TRX0 * make sure we configure timeslot 0 of TRX1 also in TCH/F mode This code is untested, but if you have a dual-trx BS-11, and the second TRX is activated, you should be able to run bsc_hack with the -1 option to enable and use the second trx. It works like this: * TRX1 shares E1 timeslot 0 for signalling * TRX1 RSL link uses TEI2 (TRX0 uses 1) * TRX1 on ARFCN+2, i.e. if you have TRX0 on 122, TRX1 will be 124 =========================== I'm very happy if somebody wans to test this. First of all, it is important to see if there are any error messages during OML and RSL brigup, and if the TEI2 link is actually established from mISDN. If you want to actually use the second TRX, you will either have to make sure all TCH/H on TRX0 are used (establish sufficient simultaneous calls), or hack chan_alloc.c to give a preference to TRX1, or to do round-robin or whatever :) 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: ip.access RTP capture using Version 1 (FR) codec
by Dieter Spaar 29 Jul '09

29 Jul '09

Hello Harald, On Wed, 29 Jul 2009 14:43:12 +0200, "Harald Welte" <laforge(a)gnumonks.org> wrote: > > If you're interested, you can certainly try for yourself with your nanoBTS... > You are joking, right ? How should it work on my Windows machine if it does not work on Linux ;-) ? Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: TDMA frame, Time slot and speech data transfer confusion.
by Dieter Spaar 29 Jul '09

29 Jul '09

Hello Nordin, On Wed, 29 Jul 2009 11:51:59 +0200, "Nordin" <bouchtaoui(a)gmail.com> wrote: > > I can't find a good link about how several MSs on one ARFCN can send and > receive speech data. Have a look at the following, the first is a general introduction with good references to the GSM specification, the second is about speech coding: http://en.wikipedia.org/wiki/Um_Interface http://www.gsmfordummies.com/encoding/encoding.shtml Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: ip.access RTP capture using Version 1 (FR) codec
by Dieter Spaar 29 Jul '09

29 Jul '09

Hello Harald, On Wed, 29 Jul 2009 12:33:59 +0200, "Harald Welte" <laforge(a)gnumonks.org> wrote: > > The FR pcap file is attached to this mail. I'll also put it to the nanoBTS wiki > page, like the EFR capture before. I hope this helps you to decode the voice > samples. Decoding with Toast would work fine but there is the same problem, lots of missing packets. If I look at the capture timestamps, there seem to miss about 0.8 seconds of data at regular intervals (the first disruption is at packet number 681, the next at 710, 742, ...). These are also the positions where the Wireshark RTP analysis complains about wrong sequence numbers. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Re: application TCH support for nanoBTS
by Dieter Spaar 29 Jul '09

29 Jul '09

Hello Harald, On Tue, 28 Jul 2009 20:58:46 CEST, "Dieter Spaar" <spaar(a)mirider.augusta.de> wrote: > > I just took a quick look at the dump with Wireshark, its possible to > safe the raw RTP payload from within Wireshark and it looks OK (31-byte > EFR packages starting with 0xC in the high nibble). However I have > no ready-made EFR decoder available so I can't decode the speech. I did play a little bit with the EFR reference implementation from GSM 06.35. Its possible to convert the data and I can understand a few words (a "Yes" at the beginning and a "Bye" at the end). However it seems that several RTP packages are missing, also the RTP Analysis Tool of Wireshark says so (according to it more than 80% is missing). Anyway, basically EFR decoding seems to work as expected. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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TDMA frame, Time slot and speech data transfer confusion.
by Nordin 29 Jul '09

29 Jul '09

Hi guys, I read Goller's documentation "About the GSM-Dm-Channels", but I'm a bit confused about something. I understand that one TDMA frame has a period of 4.615 ms and consists of 8 Time slots, each of a period of 576.9 us. When a MS registers to the BTS, it gets one Time-slot, but how is speech transfered? Normally the Fs (samplefrequency) is 8 KHz, this means every 128 us one byte sample. If I have one timeslot of let's say 577 us , than there is a gap of 7 other timeslots, which makes a 4 ms gap. Also the speech data is compressed. How is that damn speech data multiplexed with other MSs and finally received on the other side as 8 bit samplevalue at a rate of 128 us (8 KHz). It gets fuzzy to me, cause I wrote a microcontroller project which, among other things, samples audio and than transfered to a GSM module. This is done at 8 KHz samplerate, so how is that done when I have only one TimeSlot of 577 us every 4 ms period? I can't find a good link about how several MSs on one ARFCN can send and receive speech data. Thank you.

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ip.access RTP capture using Version 1 (FR) codec
by Harald Welte 29 Jul '09

29 Jul '09

Hi! Using git version 58ca5b7ae70365c1285b2ea0cb3c3370a8f108a9 of openbsc, plus the patch from the attachment, I was able to do a V1 (FR) call, not only EFR. The FR pcap file is attached to this mail. I'll also put it to the nanoBTS wiki page, like the EFR capture before. I hope this helps you to decode the voice samples. Regards, Harald -- - 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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AW: HAR2009 TODO list
by Andreas.Eversberg 29 Jul '09

29 Jul '09

> If everything works fine at HAR, we can do the bigger/better version at 26C3, > at least if we can somehow find more than the 2-3 nanoBTS1800 that we currently > have - at least for a couple of days. hi harald, i am looking forward to be at 26C3. i doubt that we can get a frequency for a test network on the 900 band, because all frequencies are assigned to GSM operators. therefore only nanoBTS1800 can be run legaly with a test license of "bundesnetzagentur". currently the application interface does not support audio streams of the nanoBTS, so other networks (ISDN/DECT/SIP) cannot be connected yet. i would like to finish audio processing for nanoBTS. can you provide me with some pcap files? a short complete call (few seconds) of one rtp session (including setup, some spoken words, and termination) would help. also the call must be made with full rate codec, so i can test the playload on the GSM codec i have. (not the enhanced full rate codec) regards, andreas

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GSM license approval for HAR2009
by Harald Welte 29 Jul '09

29 Jul '09

Hi! For those who are planning to attend HAR2009 (http://har2009.org/): We have just received regulatory approval for four ARFCN in the GSM900 band during HAR2009. The Power on each ARFCN for BTS and MS is restricted to 100mW. There are also some GSM1800 ARFCN's that we can use with up to 200mW, though I don't yet know their values and how many. I have created a wiki page at https://wiki.har2009.org/page/GSM for further coordination of GSM related activities at HAR2009. It would be great to know which other OpenBSC users/hackers will be present at the event. As there are multiple things that I'm planning to do at HAR2009, I would be happy about any help that I might get from you guys. Basically there will be * A 'stable' GSM network with BS-11 and OpenBSC for people to test their phone interoperability with OpenBSC by making/receiving calls and SMS. * A nanoBTS1800 for use by OpenBSC hackers only to test/fix OpenBSC stuff before putting it on the BS-11 'stable' network * work on airprobe. Especially for the 'stable' network, there is a lot of help required, among others: * physical setup of the BS-11 * registration of mobile phones into the network. It would probably be good to have a setup where people can plug their SIM into a SIM card reader (or phone that can read the IMSI). We can then create the SQL entry with their IMSI and extension. * making sure the network runs and OpenBSC / hfcmulti gets restarted in case something hangs. Please just respond to this mail if you want to help in any way. 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: application TCH support for nanoBTS
by Dieter Spaar 28 Jul '09

28 Jul '09

Hello Harald, On Tue, 28 Jul 2009 19:18:52 +0200, "Harald Welte" <laforge(a)gnumonks.org> wrote: > > Using this mode, I have created a pcap file with OML+RSL bringup, followed by > one call between two MS (extn. 1005 calls 1003) where all RTP/RTCP packets are > visible. The call uses EFR, since that is hardcoded in many places all over > OpenBSC at the moment. > > The pcap file is available from > http://bs11-abis.gnumonks.org/trac/attachment/wiki/nanoBTS/ipaccess-startup… I just took a quick look at the dump with Wireshark, its possible to safe the raw RTP payload from within Wireshark and it looks OK (31-byte EFR packages starting with 0xC in the high nibble). However I have no ready-made EFR decoder available so I can't decode the speech. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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