teka yemane wrote:
Hi guys,
Does any body has the source code and/or the algorithm for IMBE
vocoder to decode P25 signals?
I am doing a project on P25 software radio receiver and I need the
IMBE vocoder source code.
Thanks,
Teka Yemane
------------------------------------------------------------------------
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Hello,
In the P25 Training guide there is some information on the P25 frame
structure.
http://www.p25.com/resources/P25TrainingGuide.pdf
When it describes the Voice Data (VC1 = VC9) in the frame on Page 48,
the interleaving, error correcting, etc are done by the IMBE Codec.
These are described in TIA-102.BABA. The current Codec chips decode and
encode to baseband so it handles the whole stream.
Chapter 7 gives some overview on how the Codec works. There are some
other patents that describe IMBE used in other services and the error
correcting techniques are similar. I like using the Patent Search in
Google.
Patent 5,805,612 Mechanism for repeater error mitigation Partial
discussion of how the P25 voice frames are encoded.
Patent 5,491,772 Methods for speech transmission The appendix describes
the IMBE codec used in INMARSAT M. Different frame rate but the
techniques are similar.
If you search on IMBE in the Google Patent search there are many other
patents.
73 Eric
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio