6 Dec
2011
6 Dec
'11
7:57 a.m.
Hi,
does anybody know when the exact moment in a call is, when the NanoBTS
starts forwarding audio from a MS to OpenBSC?
Is it always when the "Create Connection" RSL message is sent and the
TCP connection was established? (Assuming the channel was set up as
traffic channel)
Or could it be that the BTS waits for the "Connect" message from the MS?
I started thinking about that when I saw that the NanoBTS _never_ sets
the "transparent to the BTS" bit in the first byte of RSL messages...
Regards,
-Tobias
6 Dec
6 Dec
9:43 a.m.
On Tue, Dec 06, 2011 at 08:57:58AM +0100, Tobias Engel wrote:
Hi,
does anybody know when the exact moment in a call is, when the NanoBTS
starts forwarding audio from a MS to OpenBSC?
I guess as soon as
1) a RTP stream is configured, and
2) there are actual audio speech frames received from the phone
Each frame on the TCH can be either audio or FACCH, this is
differentiated in L1 by the use of the stealing flags. So as long as
the phone is sending FACCH frames, they go to the LAPDm implementation
in the BTS. Once it sends voice frames, they go to the RTP socket.
The RSL CHANNEL MODE (speech) might also have an influence on it.
Or could it be that the BTS waits for the
"Connect" message from the MS?
The BTS doesn't have anythin to do with call control.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
10:22 a.m.
I guess as soon as
1) a RTP stream is configured, and
2) there are actual audio speech frames received from the phone
Ok, thanks.
Or could it be
that the BTS waits for the "Connect" message from the MS?
The BTS doesn't have anythin to do with call control.
11:47 a.m.
On Tue, Dec 06, 2011 at 11:22:41AM +0100, Tobias Engel wrote:
Do you know why the BTS then never sets the
"T"-Bit in RSL messages? Is
it just a bug in their implementation?
I guess so.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
6:02 p.m.
And in the general case (beyond the specific OpenBSC implementation) it's even more
complicated than that, depending on the assignment type (early, late, very early) and
whether or not the network uses early media for in-patterns. (In other words, the sound
of the phone ringing at the other end might come over the speech channel before the call
is actually connected.) For most purposes, the receipt of Connect Acknowledge is
considered to be the start of the call, but as Harald points out, that does not happen in
the BTS, which is mostly a layer-2 device. (Unless you are using OpenBTS, which is a
different matter altogether.)
On Dec 6, 2011, at 1:43 AM, Harald Welte wrote:
On Tue, Dec 06, 2011 at 08:57:58AM +0100, Tobias Engel
wrote:
Hi,
does anybody know when the exact moment in a call is, when the NanoBTS
starts forwarding audio from a MS to OpenBSC?
I guess as soon as
1) a RTP stream is configured, and
2) there are actual audio speech frames received from the phone
Each frame on the TCH can be either audio or FACCH, this is
differentiated in L1 by the use of the stealing flags. So as long as
the phone is sending FACCH frames, they go to the LAPDm implementation
in the BTS. Once it sends voice frames, they go to the RTP socket.
The RSL CHANNEL MODE (speech) might also have an influence on it.
Or could it be that the BTS waits for the
"Connect" message from the MS?
The BTS doesn't have anythin to do with call control.
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
5005
days inactive
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days old
4 comments
3 participants
participants (3)
-
David A. Burgess -
Harald Welte -
Tobias Engel