UmTRX integration with OpenBTS

This is merely a historical archive of years 2008-2021, before the migration to mailman3.

A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/UmTRX@lists.osmocom.org/.

Alexander Chemeris alexander.chemeris at gmail.com
Wed Jun 20 04:33:52 UTC 2012


On Wed, Jun 20, 2012 at 8:11 AM, Alexander Chemeris
<alexander.chemeris at gmail.com> wrote:
> On Wed, Jun 20, 2012 at 5:33 AM, Thomas Tsou <thomastsou at gmail.com> wrote:
>> On Mon, Jun 18, 2012 at 1:31 AM, Alexander Chemeris
>> <alexander.chemeris at gmail.com> wrote:
>>> Nothing really tested yet. At least you should do this steps:
>>> ./umtrx_lms.py --lms 1 --lms-rx-enable 1
>>> ./umtrx_lms.py --lms 1 --lms-rx-pll-tune 925e6
>>> ./umtrx_lms.py --lms 1 --pll-ref-clock 26e6 --lpf-bandwidth-code 0x0f
>>> --lms-auto-calibration
>>>
>>> Then you need to select Rx input with register 0x75. Should be
>>> something like this:
>>> ./umtrx_lms.py --lms 1 --reg 0x75 --data 0xF0
>>>
>>> There are a lot of other settings for Rx fontend in LMS which I don't
>>> understand, but I guess defaults should be fine for the start. Then we
>>> could tune them with Andrey's help.
>>>
>>> If signal is too low you may need to tune Rx VGA2 gain with the
>>> register 0x65 (refer to the programming guide for the register values
>>> encoding).
>>
>> Connected a call - all seven actually. It's quite stable once setup.
>
> Good job!
>
> How did you setup Rx on LMS?
> And anything else to know before testing?
>
>> 'fairwaves/umtrx' branch with u2plus_umtrx-20120424.bit and following
>> patch.
>
> Now it's time to make this a configure option. :)
>
>> I and Q were swapped.
>
> So I/Q order is different at Rx and Tx?We could fix this in FPGA.
>
> With the multi-ARFCN support, do you think it will be hard to add
> support for the second channel in UmTRX to OpenBTS to get 15 calls?
> Second channel is not fully supported by UmTRX FPGA firmware yet, but
> we should do this soon.

Actually interesting would be to test UmTRX with your multi-ARFCN code
to see how many channels we could fit into.

I wonder how do you select/measure rx_smpl_offset. My guess is that
you write both Tx and Rx I/Q streams to files, plot them and try to
align frame starts. Is that how do you do this?


PS Could you record a short video of making 7 calls through UmTRX? We
should make some noise or people forget what we're doing.

-- 
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru



More information about the UmTRX mailing list