Issue with Airprobe & USRP1/RFX900/52M

nghia phan nghia.phan31 at gmail.com
Wed Sep 21 20:44:38 UTC 2011


Hello everyone,

I'm looking for help.


I have downloaded and built Airprobe (gsm-receiver, gssm, ) on my Ubuntu
machine.

a/ Using the capture file provided on the web site, I could get a first
level of decoding done:

nphan at ubuntu:~/airprobe/gsm-receiver/src/python$ more capture_941.8M_112.log

Key: '0000000000000000'
Configuration: ''
  No configuration set.
configure_receiver
1670173 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670177 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670183 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670187 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670193 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670197 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670204 0: 01 06 07 60 00 25 54 a8 f9 74 05 5e 18 73 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670208 0: 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670214 0: 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670218 0: 01 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670224 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670228 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b
1670234 0: 15 06 21 00 01 00 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
2b

but in wireshark I can't see any decoded info such as BCCH system info
etc...

b/ It looks like my capture isn't working properly either (ie I can't even
get the 1st level of decoding as with capture file provided in the web
site).

nphan at ubuntu:~/airprobe/gsm-receiver/src/python$ ./capture.sh 953.4M
/usr/local/bin/usrp_rx_cfile.py
Capturing for 10 seconds to capture_953.4M_112.cfile (4642850 samples)
Using RX d'board B: Flex 900 Rx
USB sample rate 571.428k
nphan at ubuntu:~/airprobe/gsm-receiver/src/python$ ./go.sh
capture_953.4M_112.cfile
>>> gr_fir_ccc: using SSE
>>> gr_fir_ccf: using SSE
Key: '0000000000000000'
Configuration: ''
  No configuration set.
configure_receiver
gr_buffer::allocate_buffer: warning: tried to allocate
   115 items of size 568. Due to alignment requirements
   512 were allocated.  If this isn't OK, consider padding
   your structure to a power-of-two bytes.
   On this platform, our allocation granularity is 4096 bytes.
nphan at ubuntu:~/airprobe/gsm-receiver/src/python$


I have a USRP1 with 2 RFX900 with a ClockTamer providing 52Mhz clock.

I have changed the various Python scripts so that the RFX daughter on side B
and RX2  are selected. I have also changed the clock rate to 52M to match my
HW.  I have input the frequency of a known BTS (which kal can see and
measure the offset).

Any hints about what is wrong in my set-up or process?

Thanks
Nghia
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