sch burst decoding in gsm

[reda R]

hi every one 

please how i can see the decoded sch burst with grgsm

 i want to get the BCC and NCC and FN

thanks

[Piotr Krysik]

W dniu 23.06.2017 o 19:42, reda R pisze:

> please how i can see the decoded sch burst with grgsm

Currently "GSM Receiver" block decodes SCH bursts internally for its own
needs and sends raw (coded) burst to the output. Decoding SCH would
require adding decoding block.

Decoding BCC, NCC and FN is simple as there is already example in the
Receiver's code how to do this (if you know how to create new GNU Radio
block, if you don't I can instruct you). I don't know (as I didn't need
to) how to form the decoded SCH message so that Wireshark can correctly
interpret it. If you don't need Wireshark I can tell you already how to
write the decoder block.

--
Best Regards,
Piotr Krysik

[reda R]

Hi Piotr;

,thank you for your help I Have already decoded the sch burst in matlab

and i want to do that with gr-gsm to compare the result

Thanks

_________________________________________

[Piotr Krysik]

Hi Reda,

Here SCH packet is decoded by gr-gsm:
https://github.com/ptrkrysik/gr-gsm/blob/master/lib/receiver/receiver_impl.cc#L254

You will need a block that filters out SCH bursts (i.e. by looking at
sub_type field of GSMTAP header that is attached to each burst). Then
you need to add a decoding block that calls the function that I pointed
at the beginning. To add new blocks you can use gr_modtool or look how
other bursts filters and decoders are implemented.

You can also do the easy but not clean solution - you can print SCH
burst content and decoded values here:
https://github.com/ptrkrysik/gr-gsm/blob/master/lib/receiver/receiver_impl.cc#L254

and then compare that with Matlab.

Best Regards,
Piotr Krysik

W dniu 07.07.2017 o 11:21, reda R pisze: