SDR_PHY question

Adrian Musceac kantooon at gmail.com
Wed Sep 6 15:40:51 UTC 2017


Hi Vadim,

>
> In general, trxcon should be able to 'speak' with OsmoTRX,
> because one do use classical transceiver UDP interfaces. But
> there are some CTRL commands, which aren't implemented in OsmoTRX
> yet (such as ECHO and MEASURE).
>

Yes, I implemented both commands, I can share the code with you. My
problem is that Gnuradio (distro version) is built against an
incompatible ABI version of libuhd, so I have to jump through major
hoops just to get both osmo-trx and gnuradio working. So currently all
my tests are using osmo-trx only.

>
> The order of bursts should be consistent, I mean frame-by-frame.
> You need to make sure that a frame number from SCH burst is being
> decoded correctly by OsmoTRX. Every burst coming from OsmoTRX
> has a header with frame number, which is used by trxcon to
> determine a current frame position within a multiframe.
> Probably, the problem is due to incorrect / consistent
> frame number values. The internal clock counter (sched_clck.c)
> is only used to schedule the UL bursts transmission.
>

Yes, the SCH burst has a correct frame number. But the BCCH and CCCH
bursts fail to be decoded. CRC fails in
libosmocore/coding/gsm0503_coding.c
Is your gr-gsm fake-trx able to decode correctly BCCH and CCCH? I
double checked the osmo-trx code and besides some major differences
between the MS branch and master, everything looks correct.

>
> You can also join the development process, feel free to mail me.
> I will create the wiki page as soon as possible.
>

Yes, I'd like that, but for now I just want to get BCCH and CCCH
working and the mobile syncing with the BTS. Then I will be able to
test.

Cheers,
Adrian


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