tetra

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162 discussions

None
by None 03 Jan '22

03 Jan '22

would permit try transmitting. So if you either find a legal way to = include the ETSI code at build time, or preferable write a GPL compatibl= e audio decoder, I think we would be happy to include it in the git repo= sitory. cheers     holger Hello Pepijn, On Sat, 24 Sep 2011 15:49:37 +0200, "Pepijn van den Berkhof= " <<a ymailto=3D"mailto:vandenberkhof.pepijn@gmail.com" href=3D"mailto:v= andenberkhof.pepijn(a)gmail.com">vandenberkhof.pepijn(a)gmail.com</a>> wrote= : > > But do you actually hear output from a real life network= ? Because I > tried the examples attached to the ETSI document regard= ing the testing > of the codec. They work very nicely, but no luck on= real life networks > so far. (yes, no encryption) I know that= others have used the current code to decode speech, maybe someone can c= onfirm it. I haven't worked with the code for a while and so can't c= onfirm it, but it has worked for me in the past. Maybe I find the= time to try it within the next few weeks, if possible I will also try t= o provide a sample capture from a test TETRA network so everyone can try= the sample. "Test TETRA Network" means from a network under our control run in a faraday cage so that there are no legal issues providi= ng the capture. Best regards,   Dieter -- Dieter Spaa= r, Germany                  &n= bsp;       <a ymailto=3D"mailto:spaar@mirider.augusta.de" h= ref=3D"mailto:spaar@mirider.augusta.de">spaar(a)mirider.augusta.de</a> <br= > <div id=3D"yiv1108789824">is that could help us for voice decoding : ?= <a rel=3D"nofollow" target=3D"_blank" href=3D"http://www.joys99.com= /d-4784.html">http://www.joys99.com/d-4784.html</a> --= =0A</div> _______________________________________________ te= tra mailing list <a ymailto=3D"mailto:tetra@lists.osmocom.org" href=3D"m= ailto:tetra@lists.osmocom.org">tetra(a)lists.osmocom.org</a> <a href=3D"ht= tps://lists.osmocom.org/mailman/listinfo/tetra" target=3D"_blank">https://l= ists.osmocom.org/mailman/listinfo/tetra</a> </div></div></div></= body></html> --1668814050-976982791-1316890565=:17022--

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None
by None 03 Jan '22

03 Jan '22

========= The BCCH is used for two types of broadcast control channel: * BSCH (broadcast sync channel) * Broadcast Network Chanenl (BNCH) These channels, whcih are present only on the downlink, transmit information about the serving base station. The BSCH transmits the SYNC message. This provides physical layer synchronization information, including an extended training sequence for synchronisation and slot alignment, frequency correction bits to set the carrier frequency, along with MAC layer information on frame timing (i.e. the number of the current slot, frame and multiframe) as well as network layer information. Due to the physical layer synchronisation, the BSCH is transmitted on a synchronisation burst rather than a normal downlink burst. The BNCH either carries the ACCESS-DEFINE message or the SYSINFO message. The SYSINFO message fives the main carrier frequency so that mobiles can tune to it after picking up any SYSINFO message infromation on any secondary control channels, power information and network layer information. The broadcast control channels are normally transmitted in frame 18. Each takes up to one block of 216 bits, leaving the other block withing the burst for the corresponding assigned channel or for the base station to send signalling to other mobiles. O each slot, the sequence shon win figure 7.45 is used, and the sequence is offset b yone for each slot in the frame, so that every frame 18 has one BSCH and one BNCH. However, transmitting the network information takes several half-slot BNCH instances, and it will take some time therefore for a mobile to acquire all the information it needs. This is not normally a concern since mobiles will be switched on before they are used and an initial delay can be tolerated. The standards allow the option of transmitting the BNCH in other physical control channels (indicated by the AACH) as neccessary. Mobiles continue to monitor the BCCH after they are switched on and also during transmissions so as to ensure that they receive network information and remain synchronised. Multiframe number 1 2 3 4 DL Frame 18, first half slot BSCH* DL Frame 18, second half slot * BNCH * = Transmitted on a Synchronisation Burst Figure 7.45 BSCH and BNCH transmission sequence. ============== -- - 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: OsmoDevCon 2022 ?
by Harald Welte 06 Nov '21

06 Nov '21

Hi Kevin, On Fri, Nov 05, 2021 at 02:18:14PM +0100, Kévin Redon wrote: > I'm also happy to help with the recording and streaming of the public talks for those not able to join on site. thanks for that, as usual. -- - Harald Welte <laforge(a)osmocom.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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SNR for satellite signals
by Peach Y 13 Nov '20

13 Nov '20

I have worked on several satellite projects, such as SATCOM. Based on my past experience, satellite signals usually have high SNRs (or LOS signals) compared to cellular signals in the city environment, The received satellite signal's SNR would be approximately 10dB ~ 20dB, or even higher. I am currently working on a TETRA project, which would be some low earth orbit signals (terrestrial signals). What could be the range of TETRA signal SNRs? The received signal's SNR plays a very important role on the receiver structure design.

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getting started: python scripts
by Hodges, Jeff 29 Sep '20

29 Sep '20

Hi, I'm just getting started with the osmo-tetra, and following the wiki (https://osmocom.org/projects/tetra/wiki/Osmo-tetra). However, I do not see the python scripts in the git source code. For example, I cannot find: src/demod/python/tetra-demod.py * call demodulator on a 'cfile' containing complex baseband samples src/demod/python/usrp1-tetra_demod.py * use demodulator in realtime with a USRP1 SDR src/demod/python/usrp2-tetra_demod.py * use demodulator in realtime with a USRP2 SDR Jeff

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OsmoDevCon / COVID-19
by Harald Welte 04 Sep '20

04 Sep '20

Dear fellow Osmocom developers, as you all know, we've sadly had to postpone OsmoDevCon 2020 back in April this year. At the time, we discussed to re-visit the situation in October 2020. While legally it is no problem at all to host an event with ~ 20 participants in Berlin/Germany (specific regulations really only start from 50+ participants) - I'm not entirely convinced it would be the smartest move. Legality and public health regulations are only one part of the equation - common sense and profound care for the key members of our community for sure are more relevant considerations to me. I'm not 100% in favour and not 100% against. Hence, I would like to get your input. Should we a) try to get an event organized on-site in Berlin? We'd have to move to a larger venue than IN-Berlin with proper ventilation and sufficient space so we can keep physical distance, but I think that's manageable for sysmocom as organizer. b) simply postpone to 2021? I'm convinced the situation will not change significantly (in a positive way) until late April 2021, so it's not really a "solution" as it will likely mean we have to think of late 2021 or 2022. c) plan some kind of online conference? To be honest, I think this model works fine for events where a single speaker wants to give lectures to hundreds or thousands of participants. But OsmoDevCon is much more interactive. We could record or live-stream some talks or screencasts from home, sure. But that only captures one part of the event. We could also try to set a date for a collaborative mumble, or the like - for the "hallway track". What are your thoughts? Let's avoid cross-posting the discussion to all of the mailing lists and simply have it on openbsc(a)lists.osmocom.org. Regards, Harald -- - Harald Welte <laforge(a)osmocom.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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Osmocom scheduled outage on *2020-07-19 9am CEST*
by Harald Welte 19 Jul '20

19 Jul '20

There is an urgent need to migrate our most important public infrastructure to a new server, and I will be doing that on *Sunday, July 19 2020*, starting about 9am CEST. The migration involves redmine (main osmocom.org website), jenkins, gerrit, git, and cgit. In theory, the migration should be quick. I would expect (significantly) less than one hour of downtime. However, we all know Murphys law. Services not affected are mail (including mailman lists), ftp, dns. So in case of doubt, we can still use mailing lists to communicate. In case anyone urgently needs osmocom source code on Sunday morning during the downtime: There are public mirrors available on github. Regards, Harald -- - Harald Welte <laforge(a)osmocom.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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DQPSK demodulation.
by Kim Mortensen 17 Feb '20

17 Feb '20

Hi, Thanks for the add, I have been hinted this place, and im looking forward to digging deeper into the realm of TETRA / DQPSK. What im trying to do is write a C# program for demodulation of TETRA. and have come so far as to be able to view the IQ vector run around on the unity circle, but it appears a bit distorted. I think its due to a crude low pass filter i used on the I/Q signal causing this. From reading books and sites i find that I should probably used a raised cosine filter to keep the signal form beeing distorted (ISI). am i correct in my assumption? and do you have the open source code i can inspect, regardless if programming language. I know there is tons of programs out there that can decode and even produce audio from TETRA DQPSK signals, and I have one installed, but i want to have an edge to this, i need to understand and learn first hand. It may take time, but thats how it is. I have what is required regarding programming skills and radio knowledge - I am radio Amateur, and 20 years ago i did have Digital communication classes at Engineering college - But thats 20 years ago, and the equations in the books are kind of far away in my head.. but the theory sticks. Please help me get up to speed in decoding DQPSK, im not expecting to do this quickly, but will be in steps when i have time, and will lead to questions. But at some point i could be on your frontier digging into TETRA as a whole. Best Regards Kim Mortensen

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OsmoDevCon 2020 registration
by Harald Welte 01 Dec '19

01 Dec '19

Dear fellow Osmocom developers, I would like to invite all developers and contributors to Osmocom [sub]projects to register for OsmoDevCon 2020 (held on April 24th-27th, 2020 in Berlin). For details known so far, please check http://osmocom.org/projects/osmo-dev-con/wiki/OsmoDevCon2020 Please enter your name at https://osmocom.org/projects/osmo-dev-con/wiki/OsmoDevCon2020#Requested in case you would like to attend. Registering early allows proper planning. Thanks! Looking forward to meeting old and new Osmocom developers in April 2020. Regards, Harald -- - Harald Welte <laforge(a)osmocom.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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Broadcast PDU type 3
by Eric C. 29 Mar '19

29 Mar '19

I was interested in getting involved in some open source development. With a signal processing background, I thought osmo-tetra might be a good project. Looking at some data from the New Jersey Transit Authority I noticed something odd though. Some of the Broadcast PDUs had a type of 3, which in the spec is only listed as "Reserved." What's more, the control channels there seem to be missing SYSINFO messages. I'm guessing that somehow their system does a modified SYSINFO (which is normally broadcast type 0) and labels it 3? Is anyone familiar with the format they use for that message? Thanks.

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