Dear all,

I just wrote a simple test to ensure, that the new library
performs valid transcoding. I used a DCCH "LAPDM U, func=UI"
frame for simplicity, and good news is that test passed. See
attachment for details.

In the test I wrote the best signal quality is assumed. So,
ubit 0 is sbit -127 and ubit 1 is 127. But there is no such
things as miracles, and on practice error correction takes
place. So, we need to make sure, that correction works.

I am going to write tests and I have some questions:

1) How can I know the maximum count of bits can be corrected
   for a specific channel type?
2) In case of:
   gsm0503_*_decode(... int *n_errors, int *n_bits_total);
   What do the two last params mean?
3) Can anyone provide me some samples for GPRS and EDGE?
   It will take some time to set up PDCH support in my
   test network.

Thanks in advance!

With best regards,

Vadim Yanitskiy.

2016-09-26 11:05 GMT+07:00 Harald Welte <laforge@gnumonks.org>:

Hi Vadim,

sorry for the late foll-wup.

On Mon, Sep 12, 2016 at 10:56:11PM +0600, Vadim Yanitskiy wrote:
> > I think there's one option that I would prefer: Having a new library
>
> Ok, one may be a separate library in separate repo, or may be included
> into libosmocore as a sub-library, if re-licensing would be successful.
> Let's go this way.

As re-licensing is approved by all authors meahwile, a sub-library
inside libosmocore.git seems the solution.

> > like libosmogsmphy (or libosmogsm-phy or libosmogsm_phy?) which contains
> > the gsm0503 code and has dependencies to libosmocore and libosmocodec.
>
> IMHO, 'phy' may sound a little bit confusing. I would prefer something
> like 'libosmo-coding' or 'libosmocoding', without 'gsm' prefix, because
> there are GPRS and EDGE too.

I wanted the 'gsm' to indicate 2G. Most people speak of "GSM" when they
actually mean GSM+GPRS+EGPRS, i.e. second-generation technologies.

> Also, this may be a potential place for other transcoding things,
> unrelated to GSM at all. We are talking about channel coging, right?
> :)

I would assume most projects would be interested in the coding of one
specific technology, and not all of them at the same time. Yes, there
might be exceptions as a multi-RAT signal analyzer, but that could then
very easily link several libraries.

So my preference would be to have a '2g' specific library, and reflect
that in the name by using either '2g' or 'gsm' as part of the name.

Regards,
Harald
--
- Harald Welte <laforge@gnumonks.org> http://laforge.gnumonks.org/
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