1 Mar
2011
1 Mar
'11
2:54 a.m.
I've identified 4 carriers in the 400Mhz band, with a clear 4 state
constellation. Is there an easy way to verify it is indeed tetra? I'm
using grc.
Gr. Sim
4:12 a.m.
On 01-03-11 10:00, Sylvain Munaut wrote:
Thanks. I'm struggling a bit how to get a GSMTAP dissector in wireshark.
I need to recompile wireshark in order to get there, do i?
BTW it looks that idling causes the 4 state diagram, when there is data,
it turns into a 8 sided diamond.
Gr. Sim
I've
identified 4 carriers in the 400Mhz band, with a clear 4 state
constellation. Is there an easy way to verify it is indeed tetra? I'm using
grc.
Try to decode them using osmo-tetra ... (see previous annouce and the
README to know how to). 
4:20 a.m.
On 03/01/2011 10:12 AM, Sim IJskes wrote:
Thanks. I'm struggling a bit how to get a GSMTAP dissector in wireshark. I
need to recompile wireshark in order to get there, do i?
Yes, you will need to compile one of the 1.5 development versions of
wireshark. If you are using Ubuntu there are some PPAs with wireshark 1.5.1.
4:44 a.m.
On 01-03-11 10:20, Holger Hans Peter Freyther wrote:
On 03/01/2011 10:12 AM, Sim IJskes wrote:
Thanks. I've found a PPA @ <https://launchpad.net/~dreibh/+archive/ppa>
it has GSMTAP as a protocol.
I still don't have the right architectual image of GSMTAP i think. Do i
need to direct wireshark to sniff on the same interface that tetra-rx
opens its udp socket on, with a port filter, or is there a pseudo
interface that listens for raw packets on the same UDP port?
Gr. Sim
Thanks. I'm struggling a bit how to get a GSMTAP dissector in wireshark. I
need to recompile wireshark in order to get there, do i?
Yes, you will need to compile one of the 1.5 development versions of
wireshark. If you are using Ubuntu there are some PPAs with wireshark 1.5.1.
4:54 a.m.
On 03/01/2011 10:44 AM, Sim IJskes wrote:
Thanks. I've found a PPA @
<https://launchpad.net/~dreibh/+archive/ppa> it has
GSMTAP as a protocol.
I still don't have the right architectual image of GSMTAP i think. Do i need
to direct wireshark to sniff on the same interface that tetra-rx opens its udp
socket on, with a port filter, or is there a pseudo interface that listens for
raw packets on the same UDP port?
There is no pseudo interface. The tetra decoding program sends UDP packets to
the IANA assigned port for GSMTAP on the specified ip address. E.g we like to
use multicast addresses as this avoid seeing ICMP messages as the destination
is not reachable.
The easiest would be to use wireshark's pseudo interface to scan every
interface and then filter for udp in the trace and select gsmtap in the
filterbar of wireshark.
5:10 a.m.
On 01-03-11 10:54, Holger Hans Peter Freyther wrote:
Ok. I've straced tetra-rx and it opens on 127.0.0.1. So i wiresharked it
on lo with a port filter. That should work. But tetra-rx doesn't do a
write on the udp-socket. That could of course mean there is no tetra
data in the capture.
I've rebuild the usrp1-tetra_demod.py in the latest grc from git trunk,
and the 25Khz lowpass gives me a nasty spike on -22Khz. A 20Khz gives me
a much sharper idle constellation. Do you see any problem with 20Khz
lowpass?
Gr. Sim
I still
don't have the right architectual image of GSMTAP i think. Do i need
to direct wireshark to sniff on the same interface that tetra-rx opens its udp
socket on, with a port filter, or is there a pseudo interface that listens for
raw packets on the same UDP port?
There is no pseudo interface. The tetra decoding program sends UDP packets to
the IANA assigned port for GSMTAP on the specified ip address. E.g we like to
use multicast addresses as this avoid seeing ICMP messages as the destination
is not reachable.
The easiest would be to use wireshark's pseudo interface to scan every
interface and then filter for udp in the trace and select gsmtap in the
filterbar of wireshark.
5258
days inactive
5258
days old
6 comments
3 participants
participants (3)
-
Holger Hans Peter Freyther -
Sim IJskes -
Sylvain Munaut