Decoding multiple carriers

Frank A. Stevenson frank at hvitehus.no
Sat Nov 17 20:39:28 UTC 2012


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






More information about the tetra mailing list