23 Dec
2012
23 Dec
'12
4:25 p.m.
Hi Group,
i'm using the testing/sylvain burst branch.
sometimes i get double frames in the bursts files taken with ccch_scan.
what does this mean?
bad reception?
kind regards
8:58 p.m.
double frame numbers
----- Oorspronkelijk e-mail -----
Van: "Sylvain Munaut" <246tnt(a)gmail.com>
Aan: "g roelant" <g.roelant(a)telenet.be>
Cc: "osmocomBB" <baseband-devel(a)lists.osmocom.org>
Verzonden: Zondag 23 december 2012 18:51:31
Onderwerp: Re: double frames in burst file
Hi,
sometimes i get double frames in the bursts files
taken with ccch_scan.
What do you mean by "double frames" ?
Cheers,
Sylvain
24 Dec
24 Dec
9:45 a.m.
double frame numbers
Just means some are from uplink and some from downlink frequencies.
Some subchannels of SDCCH have uplink and downlink on the same frame
and if the target phone is clone enough you can receive the frames
from the phone as well. The 'arfcn' field should have the ARFCN_UPLINK
flag set (grep libosmocore to know the value).
Cheers,
Sylvain
10:11 a.m.
it's correct. the phenomenon only occurs with my own tests...
so tx gsm is very close to rx gsm...
what should i do in my program that parse the bursts? skip the double frame and read on?
or skip all frames with uplink flag set?
i shall investigate this evening...
cheers,
ps. can i ask you a question about weak frames?
what i noticed: the offset between si5, si5ter, si6 and the first si6 frame after
encryption is not always 204 frames
is this correct?
----- Oorspronkelijk e-mail -----
Van: "Sylvain Munaut" <246tnt(a)gmail.com>
Aan: "g roelant" <g.roelant(a)telenet.be>
Cc: "osmocomBB" <baseband-devel(a)lists.osmocom.org>
Verzonden: Maandag 24 december 2012 09:45:10
Onderwerp: Re: double frames in burst file
double frame numbers
Just means some are from uplink and some from downlink frequencies.
Some subchannels of SDCCH have uplink and downlink on the same frame
and if the target phone is clone enough you can receive the frames
from the phone as well. The 'arfcn' field should have the ARFCN_UPLINK
flag set (grep libosmocore to know the value).
Cheers,
Sylvain
2:47 p.m.
Hi,
what should i do in my program that parse the bursts?
skip the double frame and read on?
or skip all frames with uplink flag set?
Do whatever you want with them depending on what your needs are ...
ps. can i ask you a question about weak frames?
what i noticed: the offset between si5, si5ter, si6 and the first si6 frame after
encryption is not always 204 frames
is this correct?
Yes, there is no specs so operator do what they want and for some of
them it's pseudo-random.
Cheers,
Sylvain
4:23 p.m.
So there will always be a try and guess method involved...?
Are the possible frames always a multitude of 102 apart?
Or are there other offsets?
Is the kraken version which does 4 frames at the same available somewhere?
----- Oorspronkelijk bericht -----
Van: Sylvain Munaut <246tnt(a)gmail.com>
Aan: g roelant <g.roelant(a)telenet.be>
Cc: osmocomBB <baseband-devel(a)lists.osmocom.org>
Verzonden: Mon, 24 Dec 2012 14:47:26 +0100 (CET)
Onderwerp: Re: double frames in burst file
Hi,
what should i do in my program that parse the bursts?
skip the double frame and read on?
or skip all frames with uplink flag set?
Do whatever you want with them depending on what your needs are ...
ps. can i ask you a question about weak frames?
what i noticed: the offset between si5, si5ter, si6 and the first si6 frame after
encryption is not always 204 frames
is this correct?
Yes, there is no specs so operator do what they want and for some of
them it's pseudo-random.
Cheers,
Sylvain
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Sylvain Munaut