tetra November 2012

tetra@lists.osmocom.org

6 participants
6 discussions

TETRA test samples
by Dieter Spaar 01 Feb '13

01 Feb '13

Hello, there is now a test sample (bit file) with speech at http://tetra.osmocom.org/trac/wiki/Test_Samples Please only add samples to this page if you have the full agreement for publishing from all involved parties (e.g. operator of the network, people speaking during the capture). This is not the place to share captures which were made from someone else without their knowledge. Best regards, Dieter -- Dieter Spaar, Germany spaar(a)mirider.augusta.de

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Fix some uglyness
by Frank A. Stevenson 01 Dec '12

01 Dec '12

Attached is a patch that fixes some global ugliness. The dependencies are a bit iffy, so you need a make clean after applying this. This fix needs to be in place before you decode multiple carriers. I would like to suggest that tetra-rx.c be changed so that it can receive multiplexed streams of input. Byte values of 0 / 1 will be the primary stream, but other values can be used to encode the multiplexed streams. The easiest method is to use the high order bits of the input as a "stream id", and dynamically create new state structs as they appear in the stream. Does this sound like a decent solution ? f

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Bounce action notification
by mailman＠lists.osmocom.org 25 Nov '12

25 Nov '12

This is a Mailman mailing list bounce action notice: List: tetra Member: jasperkanbier(a)wanadoo.nl Action: Subscription disabled. Reason: Excessive or fatal bounces. The triggering bounce notice is attached below. Questions? Contact the Mailman site administrator at mailman(a)lists.osmocom.org.

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osmotetra java port
by Jack 19 Nov '12

19 Nov '12

Hello, I just started to write a java port of osmotetra and I wonder if there is some people interested who can help me to debug, clean and make documentation (javadoc format) for this code. I want to write a java implementation of codec too, but I don't know if I can distribute the code or if its license forbids it, can you tell me about this? Thanks. Jesús M. Tormo.

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Decoding multiple carriers
by Frank A. Stevenson 18 Nov '12

18 Nov '12

I have gotten some code working now to a proof of concept level. What it does is: A) Capture 2 MHz of spectrum to fifo (1) (gnuradio-companion) B) Frequency shift, filter and decimate fifo(1) -> fifo(2) using GPU C) Demodulate fifo (2) into bits to fifo(3) using my own "dodgy demodulator" D) Running tetra-rx from fifo(3) - for display in wireshark This runs realtime at around 30% CPU load (for a single core) and 30% GPU load on an ATI 5850 card. So I can easily add more carriers to tetra-rx (I have 2 such GPUs), but tetra-rx doesn't seem well prepared for handling such situations, for instance the GSMTAP packets are not tagged by ARFCN - besides I don't have a good understanding of what others would want to do when demodulating multiple carriers. Personally I have to limit myself to traffic analysis on a fully encrypted network. Are there any plans for how to progress tetra-rx that I can follow, or should I just rip the thing apart and make it do what I want it to do ? f

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Strange offset in float_to_bits.c
by Frank A. Stevenson 18 Nov '12

18 Nov '12

I made this change: diff --git a/src/float_to_bits.c b/src/float_to_bits.c index 08fad54..4547ffe 100644 --- a/src/float_to_bits.c +++ b/src/float_to_bits.c @@ -113,7 +113,7 @@ int main(int argc, char **argv) exit(1); } else if (rc == 0) break; - rc = process_sym_fl(0.3f, fl); + rc = process_sym_fl(0.0f, fl); sym_int2bits(rc, bits); //printf("%2d %1u %1u %f\n", rc, bits[0], bits[1], fl); if (opt_verbose) Which improved decoding rate on correctly tuned captures. I think this 0.3 offset is an oversight that will generally increase BER. In other news, I have gotten my own GPU (openCL) assisted demodulator working, I am thinking about decoding multiple carriers concurrently with this code, but I think the gnu_radio demodulator has an edge with regards to BER, especially if the offset is set to 0.0f :-) Cheers, Frank

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tetra November 2012