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Messages - david.burgess

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There is no database, but capturing the UDP with tcpump and then parsing with Wireshark works well and will give everything you are asking about.

YateBTS / Re: GPRS problem in YateBTS
« on: August 28, 2014, 07:46:36 PM »
Be sure the phone has a defined access point name (APN).  It does not matter what the APN is, as long as it exists.

Rod -

An update - The SI3 decoding error may just be a limitation of Wireshark.  But the SI13 error is probably real.  Since SI13 is the message that essentially announces the presence of GPRS, and since the CRO is a GPRS feature, it is possible that a bad SI13 would prevent the phone from using CRO, although this behavior would depend on the implementation details of the handset.  Have you tried CRO with other handsets?


Rod -

I got a look at your PCAP file and see that both the SI3 and SI13 messages are malformed, which would easily explain the problem.

We will get to work on on fixing these.

I also have a question that would be helpful in debugging: Do GPRS work for you at all, with CRO enabled or disabled?

-- David

I think we need to look at a GSMTAP trace of the beacon.

YateBTS can generate traces at the L1/L2 interface in the [ GSMTAP] format, which is support in Wireshark.  In this mode, each GSMTAP packet carries a single [ LAPDm] frame.

See the “tapping” section in ybts.conf or do "devconfig Control.GSMTAP" from the CLI to see the associated parameters and look at the documentation for each one:

YATE 5.3.0-1 r5826 ( ready on ybts-UNCONFIG.
mbts config GSMTAP
Control.GSMTAP.GPRS no     [default]
Control.GSMTAP.GSM no     [default]
Control.GSMTAP.TargetIP     [default]

You want to turn on GSM tapping (mbts config Control.GSMTAP.GSM yes) and send the packets to the localhost IP (the default).  Then capture the packets on UDP port 4729 into a PCAP file with tcpdump.  You can then look at the GSM activity in Wireshark.

Please collect a PCAP file showing a few seconds of the idle YateBTS and send it to me at  I want to see if the SI3 rest octets are actually there and if SI13 is getting sent.

If you look in mbts/GSM/GSML3RRElements.cpp, you will see that there is a configuration parameter called "GSM.SI3RO.CRO" that sets the CRO.  That value can be changed from the Yate command line with the "mbts rawconfig" command.

Note that the CRO appears in the Sys Info 13 message, which is sent only when GPRs is enabled.

YateBTS / Re: support devices
« on: February 10, 2014, 02:41:44 AM »
YateBTS supports the same radios as the public release of OpenBTS, because it uses the same transceiver module.  To my knowledge, this includes the Ettus USRP-1, along with several other Ettus radios, as well as the Range RAD1.  Very importantly, though, support for the Nuand BladeRF is coming very soon!

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