2 Jun
2021
2 Jun
'21
10:06 a.m.
Hi Sylvain,
Thank you for getting back on this.
I will look further into the block as you suggested. It is also possible
that the uplink signal of my initial capture was too strong and somehow
saturated the receiver.
I plan to perform more tests in the coming weeks as the weather is getting
better.
Best regards,
Johann
On Tue, May 25, 2021 at 7:26 PM Sylvain Munaut <246tnt(a)gmail.com> wrote:
Hi,
I have made some captures on the L-band uplink
channels and tried to
decode the RACH messages. All four consecutive TCH channels
(according to
the spot beam) were recorded and a call was made during the recording.
I am using the GRC block gmr_rach_scan.grc. I have removed the IQ swap
from the
graph, as suggested in the mailing list. The sampling rate and
samples-per-symbol values have been set to 93.6k and 4, respectively.
Oops, looks like I complete missed this ... sorry.
That graph was made to scan large bandwidth capture for RACH ... It's
very probable that a bunch of constants and thresholds value are just
not appropriate for a narrow band capture.
It kind of always required tweaking depending on the case. Basically
manually finding a RACH (in frequency and time), then look at all the
intermediate steps of the graphs (and possibly inside the block) to
see if it detects that particular one and tweak it until it does. And
then you can run it to find the other ones.
I don't have any setup any more to capture C-band uplink so I have not
run that graph in years .... but that's all I remember about it.
Cheers,
Sylvain