decoding voice on hopping channel

[lab.accesssolution]

Hi List,

I'm trying to decoding voice on hopping channel, my hardware is hack-rf.

From system information 1 i can find that the bandwidth of the observed channel is 6M, Max ARFCN 809 = 1858.8 MHz and max ARFCN 809 = 1864.6 MHz. I'm using the following command to capture the GSM packet:

1. grgsm_capture.py -s 10e6 -f 1861.6e6 -c tsel794_090617.cfile -T 60 (I'm capturing at BCCH frequency)

After capturing the packet, i continue with decoding SDCCH packet and find the TCH, with the following command:

2. grgsm_decode -s 10e6 -f 1861.6e6 -c tsel794_090617.cfile -m SDCCH8 -t 2 -e 1 -k 'XXXXXXXX'

and it shows some TCH traffic at hopping channel (please take a look at the attachment files). After that, i try to channelize the captured packet with the following command:

3. grgsm_channelize.py -s 10e6 -f 1861.6e6 780 786 809 -i tsel794_090617.cfile -b DCS1800
Input sample rate: 10M
Output sample rate: 1M
==> using resample rate of 0.1
Extracting channels [780, 786, 809], given that the center frequency is at 1.8616G
ARFCN 780 is at 1.8616GHz -2.8MHz
Using Volk machine: avx2_64_mmx_orc
ARFCN 786 is at 1.8616GHz -1.6MHz
ARFCN 809 is at 1.8616GHz +3MHz
Done!

and it produces the following files: out_780.cfile  out_786.cfile  out_809.cfile

but when i try to decode each files, it shows no output. i did it with the following commands:
grgsm_decode -s 1e6 -f 1861.6e6 -c out_780.cfile -v

(please also take a look at the attachment files).

Can anyone help to solve this problem?

Thanks & Regards,

Erik

[Tomcsányi, Domonkos]

You need to use the hopping GRC flowgraph that can use all channel files together to recreate voice.

Cheers,

Domi

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<Hopping_voice_call.png>

<decode hopping.png>