Re: [Openbts-discuss] OpenBTS 5.0 + USRP B200

[Pierre B. <agm...@ag...>]

Hello Gerhard, Hello Tom.

I encountered the very same problem today using B200 as well.
As far as I remember, using OpenBTS receiver was fine earlier this year, so
I downgraded UHD back to 003.007.002 and got it working fine.

I can try other UHD releases asap if it can help to get that bug fixed.

2015-10-08 20:22 GMT+02:00 Pierre Baudry <ag...@ag...>:

> Hello Gerhard, Hello Tom.
>
> I encountered the very same problem today using B200 as well.
> As far as I remember, using OpenBTS receiver was fine earlier this year,
> so I downgraded UHD back to 003.007.002 and got it working fine.
>
> I can try other UHD releases asap if it can help to get that bug fixed.
>
> 2015-09-23 17:25 GMT+02:00 Gerhard <ope...@gk...>:
>
>> Hi Tom, Hi all,
>>
>> sorry for not answering earlier. I've just got some spare time and was
>> able to test your suggestions.
>>
>> It worked! By using the OsmoTRX instead of the OpenBTS transceiver my
>> phone was able to register on the network! Thanks for this suggestion"
>> Now there is a follow-up question in my mind: Why did it work? Is
>> OsmoTRX more sensible when it comes to detecting and handling RACH bursts?
>>
>> Furthermore, I would really like to use the "original" transceiver,
>> because my goal was to do some GPRS. Citing from the OsmoTRX page [1]:
>> "OsmoTRX is fully compatible with OpenBTS for voice and SMS services.
>> Due to differences in handing of GPRS, OsmoTRX does not support GPRS
>> when used with OpenBTS, however, GPRS with the Osmocom stack is
>> supported."
>>
>> Any hints on what I can do to get my setup to work with the OpenBTS
>> transceiver? Or is the only solution the hard way (enable DEBUG logging)?
>> ;)
>>
>>
>> As always: any help is welcome.
>>
>> Cheers
>>   Gerhard
>>
>>
>> [1] http://openbsc.osmocom.org/trac/wiki/OsmoTRX#OsmoTRXwithOpenBTS
>>
>>
>>
>> On Sep 11, 2015 at 00:33 AM Tom Tsou wrote:
>> > On Thu, Sep 10, 2015 at 8:02 PM, Gerhard <ope...@gk...> wrote:
>> >> I'm struggling to get OpenBTS 5.0 with an USRP B200 to work. After I
>> >> have build, installed and run OpenBTS, all I get is the network showing
>> >> up on my Android device. When I try to connect to it, it fails (even
>> >> with open registration enabled). There are no hints in the logfiles.
>> The
>> >> "tmsis"-table stays empty.
>> >
>> > Likely case is RACH bursts being missed.
>> >
>> > Can you give OsmoTRX a try as a replacement for OpenBTS transceiver?
>> > Note the section on compatibility with OpenBTS.
>> >
>> > http://openbsc.osmocom.org/trac/wiki/OsmoTRX
>> >
>> >> Another mail said that the internal clock of the B200 is way to bad for
>> >> using it with OpenBTS.[2] Is that so? How can I find out, if the clock
>> >> is causing the issues?
>> >
>> > Typically, but not always, If the handset is able to detect the
>> > network, then clocking is sufficient for test calls other basic
>> > services.
>> >
>> >> The OpenBTS book and several other sources state to set "rxgain" to
>> 0-10
>> >> for USRP devices. However, Matt Ettus said (regarding the gain of a
>> >> B200) via the USRP-users mailing list: "0dB of gain is unusably low.
>> You
>> >> should be using at least 40dB unless there is a very strong signal."
>> >> What value should I use?
>> >
>> > The point of confusion is that gain ranges vary across different USRP
>> > devices. For example, gain range on the RFIC based B200 is roughly
>> > 0-75 dB while the range on X300 with UBX daughterboard is 0-30 dB. The
>> > OpenBTS book assumes a range closer to the latter, which ends up in
>> > the low to middle part of the range.
>> >
>> > 40 dB on RFIC is close to mid-level, which is a reasonable starting
>> > point. With GSM handsets we are dealing high transmit power levels, so
>> > lowering the Rx gain at close range makes sense. Setting gain down to
>> > 0 dB is excessive and typically reserved for directly coupled use
>> > cases (i.e. not OTA).
>> >
>> >> My setup is
>> >> * Ubuntu 12.04.05 LTS Server (32 bit)
>> >> * OpenBTS 5.0 ($ ./switchto.sh 5.0)
>> >> * USRP B200 (no external clock)
>> >> * UHD 003.009.000
>> >> * No Antennas attached (Phone is next to the USRP)
>> >
>> > Nothing abnormal. Attaching antenna(s) with lowered gain settings is
>> > recommended over raw SMA connectors for consistency. Also check
>> > logging for anything unusual; INFO logging level is fine.
>> >
>> >   -TT
>> >
>>
>>
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>
>