2 Apr
2015
2 Apr
'15
4:47 p.m.
Dear Osmcom,
I am working on a project, where I am connecting OsmoBTS with OsmocomBB
without hardware.
I am trying to remove l1 on both sides and connect OsmoBTS with BB
application via simple unix sockets. Based on the further recommendations,
I am using osmobts-trx branch. Currently I am able to handle messages
between BTS and TRX driver on clock and control ports, and on BB side I am
in state that phone wants to connect into a cell (so its waiting for BCCH)
. I am now trying to find a possible way how to handle messages on data
port , between BTS – TRX ( TRX is removed, there is my application
instead), and forward these messages to my customized BB l1 interface . The
thing is that I need to send to BB phone (layer23) messages in structures
from gsm_04_08.h (i.e. gsm48_system_information_type_3). I am not sure if I
will be able to get needed from the messages coming on the data port 5702.
I found, that PCU creates unix socket on “/tmp/pcu_bts” , but only in case
sysmoBTS is in use (please correct me if I am wrong), so this will be not
possible due compilation errors without HW. Here I found the
gsm48_system_information_type_3 messages.
So basically I need somehow to get this message structures on my custom l1
BB interface. Do you have any idea how to do this ?
Any advice will be highly appreciated.
Many thanks you for your attention :)
Best regards,
Dominik Tamaskovic.
7 Apr
7 Apr
6:15 p.m.
Hi Dominiq,
I am trying to remove l1 on both sides and connect
OsmoBTS with BB application via simple unix sockets.
...
Currently I am able to handle messages between BTS and
TRX driver on clock and control ports
...
The thing is that I need to send to BB phone (layer23)
messages in structures from gsm_04_08.h (i.e. gsm48_system_information_type_3).
I am not sure if I will be able to get needed from the
messages coming on the data port 5702.
You are correct. The data port UDP messages carry burst data - that is data after
convolutional encoding and interleaving as well as training sequence insertion, padding
etc... You would have to very inefficiently decode all this again to retrieve the CSN
data bits you seek, though you could then stimulate the timing advance and power control
loops.
I found, that PCU creates unix socket on
“/tmp/pcu_bts” , but only in case sysmoBTS is in use (please correct me if I am wrong),
For non-sysmoBTS there is a different socket, TCP or UDP - I forget, but that's why
you don't see the SEQ_PACKET Unix socket in /tmp for the other config. Check
sysmo_sock.cpp vs openbts_sock.cpp.
So basically I need somehow to get this message
structures on my custom l1 BB interface.
Do you have any idea how to do this ?
I'm no expert, but depending on your ultimate goal you may have some luck pulling them
out of the GSMTAP interface. You can view this using Wireshark to quickly see if it is
enough. Check the docs or source on how to set this up and view it.
Alternatively, using the trx branch, you could try implementing a custom l1. Check around
the bts_model/l1sap code for the software interface (which is shared between the code in
osmo-bts-sysmo and osmo-bts-trx). That's probably a fair bit of work but gives you a
lot of flexibility.
Kind Regards,
Mike
11 Apr
11 Apr
5:20 p.m.
Hi Mike,
Thanks for your advice.
For non-sysmoBTS there is a different socket, TCP or
UDP - I forget, but
that's why you don't see the SEQ_PACKET Unix socket in
/tmp for the other
config. Check sysmo_sock.cpp vs openbts_sock.cpp.
- for the openbts, i found UDP channel on 5944 <--->5934 ports. But in case
of the osmo-bts-trx i did not found anything. Even with openBTS i could see
some "activity" of the PCU . I.e. while i started my app with OpenBTS, i
could see at least:
<0001> pcu_l1_if.cpp:330 BTS available
<0001> pcu_l1_if.cpp:80 Sending activate request: trx=0 ts=6
<0001> pcu_l1_if.cpp:456 PDCH: trx=0 ts=6
<0001> pcu_l1_if.cpp:80 Sending activate request: trx=0 ts=7
<0001> pcu_l1_if.cpp:456 PDCH: trx=0 ts=7
but with trx no activity at all. I am doing something wrong ? Do I have
change config somehow ?
I'm no expert, but depending on your ultimate goal
you may have some luck
pulling them out of the GSMTAP interface. You can view this
using
Wireshark to quickly see if it is enough. Check the docs or source on how
to set this up and view it.
Alternatively, using the trx branch, you could try implementing a custom
l1. Check
around the bts_model/l1sap code for the software interface
(which is shared between the code in osmo-bts-sysmo and osmo-bts-trx).
That's probably a fair bit of work but gives you a
lot of flexibility.
- I think i can do it like this: As a "transmit" interface BTS -> osmocomBB
i want to use GSMTAP feature. I thing there is suffient support of this
protocol for my needs. The biggest issue i can see is, how to handle
receive messages GSMTAP messages on my eBTS. I have idea to transform these
messages into l1sap readable format, and send them to l1sap_up() function
(which, if I am not mistaken , is a single point for trasnfer primitives
from the TRX - please correct me). I have currently no idea what willl
happen, and if its even possible to "jump over" the lower parts of the
code...
Thanks.
Dominik
2015-04-07 18:10 GMT+02:00 Mike McTernan (wavemobile) <
mike.mcternan(a)wavemobile.com>gt;:
> Hi Dominiq,
>
> > I am trying to remove l1 on both sides and connect OsmoBTS with BB
> application via simple unix sockets.
> ...
> > Currently I am able to handle messages between BTS and TRX driver on
> clock and control ports
> ...
> > The thing is that I need to send to BB phone (layer23) messages in
> structures from gsm_04_08.h (i.e. gsm48_system_information_type_3).
>
> > I am not sure if I will be able to get needed from the messages coming
> on the data port 5702.
>
> You are correct. The data port UDP messages carry burst data - that is
> data after convolutional encoding and interleaving as well as training
> sequence insertion, padding etc... You would have to very inefficiently
> decode all this again to retrieve the CSN data bits you seek, though you
> could then stimulate the timing advance and power control loops.
>
> > I found, that PCU creates unix socket on “/tmp/pcu_bts” , but only in
> case sysmoBTS is in use (please correct me if I am wrong),
>
For non-sysmoBTS there is a different socket, TCP or
UDP - I forget, but
> that's why you don't see the SEQ_PACKET Unix socket
in /tmp for the other
> config. Check sysmo_sock.cpp vs openbts_sock.cpp.
>
> > So basically I need somehow to get this message structures on my custom
> l1 BB interface.
> > Do you have any idea how to do this ?
>
> I'm no expert, but depending on your ultimate goal you may have some luck
> pulling them out of the GSMTAP interface. You can view this using
> Wireshark to quickly see if it is enough. Check the docs or source on how
> to set this up and view it.
>
> Alternatively, using the trx branch, you could try implementing a custom
> l1. Check around the bts_model/l1sap code for the software interface
> (which is shared between the code in osmo-bts-sysmo and osmo-bts-trx).
> That's probably a fair bit of work but gives you a lot of flexibility.
>
> Kind Regards,
>
> Mike
>
3304
days inactive
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days old
osmocom-net-gprs@lists.osmocom.org
2 comments
2 participants
participants (2)
-
Dominiq T -
Mike McTernan (wavemobile)