[srslte-users] Problem with decoding SIB2 using cell_measurement example

Tue Apr 17 15:53:46 UTC 2018

Sorry, I cannot help you. I do not know how srsLTE knows the SIB position.

Best regards,
Alejandro

2018-04-17 17:50 GMT+02:00 Laura Flueratoru <flueratorulaura at gmail.com>:

> Hi Alejandro,
>
> Thank you for the advice, I will also try that. But do you know why
> this happens and is this the way it's done in srsue? I find it strange
> to need to go through all of the payloads. I saw that in
> rrc::run_si_acquisition_procedure (srsue/src/upper/rrc.cc) the
> location of the SIBs is still computed, but I couldn't identify the
> physical layer part that is accessing them.
>
> Best,
> Laura
>
> On Tue, Apr 17, 2018 at 5:25 PM, ALEJANDRO BLANCO PIZARRO
> <100283180 at alumnos.uc3m.es> wrote:
> > Hi Laura,
> >
> > I had this issue and I finally realized that the position that it is
> > obtained using the LTE standard could not be the same in real scenarios.
> >
> > My piece of advice: you should program a loop and go over the subframe id
> > and the system frame number  showing all the payloads and the positions.
> > With it, you are going to show all SIB payloads, afterwards, with
> > http://www.marben-products.com/decoder-asn1-lte/ see what is the SIB2
> > payload and see what are the system frame number and the subframe id
> > relative to SIB2, to see if you made a mistake.
> >
> >  if ((srslte_ue_sync_get_sfidx(&ue_sync) == variable_loop1) &&   (sfn %
> > si_loc[0].period) == variable_loop2)
> >
> > I know that this piece of advice is not really smart but is functional.
> >
> > Tell me if you need further information.
> >
> > Best,
> > Alejandro
> >
> > 2018-04-17 17:16 GMT+02:00 Laura Flueratoru <flueratorulaura at gmail.com>:
> >>
> >> Hi Alejandro,
> >>
> >> Yes, I know about the decoder, but my problem is that I don't know how
> >> to find SIB2's location, even given the information from SIB1. The way
> >> I tried to do it (explained in the email before) gives me a payload
> >> for SIB2 that is interpreted by the decoder you mentioned as a SIB1
> >> format. So the location I'm trying to access is clearly not the
> >> location of SIB2.
> >>
> >> So do you know how could I find the correct location of SIB2? Thank you!
> >>
> >> Best,
> >> Laura
> >>
> >> On Tue, Apr 17, 2018 at 4:53 PM, ALEJANDRO BLANCO PIZARRO
> >> <100283180 at alumnos.uc3m.es> wrote:
> >> > Hi Laura,
> >> >
> >> > I do not completely understand your problem, but have you tried to
> >> > decode
> >> > the SIB2 payload by http://www.marben-products.com/decoder-asn1-lte/?
> >> >
> >> > Best!
> >> > Alejandro
> >> >
> >> > 2018-04-17 13:46 GMT+02:00 Laura Flueratoru <
> flueratorulaura at gmail.com>:
> >> >>
> >> >> Hi everyone,
> >> >>
> >> >> I am trying to decode SIB2 using the cell_measurement example. I have
> >> >> already decoded the information regarding the location of the SI
> >> >> messages from SIB1, and the periodicity of SIB2 should be RF8 (same
> as
> >> >> for SIB3) and the SI Window Length is 3.
> >> >>
> >> >> From this, I compute the subframe number, the periodicity and the
> >> >> offset according to 36.331 and try to search for the SIB2 in a loop
> as
> >> >> in the code snippet below:
> >> >>
> >> >>     if ((srslte_ue_sync_get_sfidx(&ue_sync) == si_loc[0].subframe)
> &&
> >> >>          (sfn % si_loc[0].period) == si_loc[0].mod_sfn) {
> >> >>         n = srslte_ue_dl_decode(&ue_dl, data, 0,
> >> >>                   sfn*10+srslte_ue_sync_get_sfidx(&ue_sync), acks);
> >> >>
> >> >> where:
> >> >>     - si_loc[0].subframe is SIB2's subframe number and has the value
> 0
> >> >>     - si_loc[0].period is SIB2's periodicity and has the value 8
> (RF8)
> >> >>     - si_loc[0].mod_sfn is SIB2's offset and has the value 0
> >> >>
> >> >> It does find something at that location and an example payload is
> >> >> [40 48 a0 03 06 50 11 84 60 88 19 31 80 81 84 4c 23 61 23 18 00 00 63
> >> >> 9e 9d 00 00 00 00 00 00 00 65 2b 44 7c ef ]
> >> >> whereas the payload of SIB1 was
> >> >> [40 48 a0 03 06 50 11 84 60 88 19 31 80 81 84 4c 23 61 23 18 00 00 ]
> >> >>
> >> >> So I find it weird that the first part of the payload I get for SIB2
> >> >> would be exactly the same as for SIB1, so I think there's something
> >> >> wrong with the way I try to retrieve SIB2's data.
> >> >>
> >> >> Can you please tell me if there's something wrong with the way I
> >> >> search for the SI message? I tried to look in
> >> >> rrc::run_si_acquisition_procedure which seems to be computing the
> same
> >> >> location, but it seems to me that I'm doing almost the same thing
> here
> >> >> (minus specifying the window length in which to search for the SI
> >> >> message). Any help would be greatly appreciated. Thank you!
> >> >>
> >> >> Best regards,
> >> >> Laura
> >> >> _______________________________________________
> >> >> srslte-users mailing list
> >> >> srslte-users at lists.softwareradiosystems.com
> >> >> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
> >> >
> >> >
> >
> >
>
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