From mohamedyehia219 at gmail.com  Mon Sep  9 10:18:01 2019
From: mohamedyehia219 at gmail.com (mohamed yehia)
Date: Mon, 9 Sep 2019 12:18:01 +0200
Subject: RACH intercepting
Message-ID: <CANvc3TnFwW=6Nd-wFjAqwLS4YexNHKQa4S0FGUtdHS1L5vi8VQ@mail.gmail.com>

Dear community members,
I'm interested in intercepting L band up-link RACH channel
I found the BCCH channel of the spot beam I'm currently in then scan the
same ARFCN but in uplink
I had a cfile and I tried to read it using gr-gmr1
<https://github.com/osmocom/osmo-gmr/tree/sylvain/gr/gr-gmr1> in the branch
sylvain/gr <https://github.com/osmocom/osmo-gmr/tree/sylvain/gr>
but i have no results , may be I don't know how to use the read utility in
sylvain/gr <https://github.com/osmocom/osmo-gmr/tree/sylvain/gr>
I also have another question about the file test.pcap in
http://people.osmocom.org/tnt/gmr/
how can I have a file like it and is it l band RACH data or C band.
-- 

*Best Regards , *

*Mohamed Yehia Mohamed *
Mobile : +2 0102 674 5023
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From 246tnt at gmail.com  Wed Sep 11 15:48:37 2019
From: 246tnt at gmail.com (Sylvain Munaut)
Date: Wed, 11 Sep 2019 17:48:37 +0200
Subject: RACH intercepting
In-Reply-To: <CANvc3TnFwW=6Nd-wFjAqwLS4YexNHKQa4S0FGUtdHS1L5vi8VQ@mail.gmail.com>
References: <CANvc3TnFwW=6Nd-wFjAqwLS4YexNHKQa4S0FGUtdHS1L5vi8VQ@mail.gmail.com>
Message-ID: <CAHL+j0_d=xSzSoRp-oJsuofF8KAjHzdxHfSJemfZc+BDDORoKA@mail.gmail.com>

Hi,

> I'm interested in intercepting L band up-link RACH channel
> I found the BCCH channel of the spot beam I'm currently in then scan the same ARFCN but in uplink
> I had a cfile and I tried to read it using gr-gmr1 in the branch sylvain/gr
> but i have no results , may be I don't know how to use the read utility in sylvain/gr

Although the method should work to detect the RACH burst on L-band, it
has only ever been tested on C-band wideband captures, so YMMV.
Note that the example .grc graph that's provided does an IQ swap
because usually when you get samples from a C-band LNB they underwent
a spectrum inversion due to the high-side LO mixing inside the LNB. If
you're working off a direct capture off L-band you need to remove that
swap from the graph.

Also, are you sure you actually _have_ RACH requests in your file and
they don't saturate your receiver ?
If you have an example capture to post, put it online somewhere and
post the link.


> I also have another question about the file test.pcap in http://people.osmocom.org/tnt/gmr/
> how can I have a file like it and is it l band RACH data or C band.

This was captured on C-band.

Cheers,

     Sylvain Munaut