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
double frame numbers
----- Oorspronkelijk e-mail ----- Van: "Sylvain Munaut" 246tnt@gmail.com Aan: "g roelant" g.roelant@telenet.be Cc: "osmocomBB" baseband-devel@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
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
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@gmail.com Aan: "g roelant" g.roelant@telenet.be Cc: "osmocomBB" baseband-devel@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
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
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@gmail.com Aan: g roelant g.roelant@telenet.be Cc: osmocomBB baseband-devel@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