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.
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
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@wavemobile.com>:
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
-
Dominiq T -
Mike McTernan (wavemobile)