Decode error for airprobe

[sk80]

Hi,

I have installed gnuradio 3.7, aiprobe and zmania patch on ubuntu 14.04

I get following errors while running airprobe

---

./gsm_receive_hackrf_3.7.py -s 1e6 -f 937.8e6
linux; GNU C++ version 4.8.2; Boost_105400; UHD_003.008.004-0-unknown

gr-osmosdr v0.1.x-xxx-xunknown (0.1.5git) gnuradio 3.7.5
built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf bladerf rfspace airspy
[bladeRF source] Using nuand LLC bladeRF #0 SN 01ce...8d2e FW v1.8.0 FPGA v0.1.2
[INFO @ bladerf.c:604] Clamping bandwidth to 1500000Hz
sample rate: 1000000
Using Volk machine: sse4_2_64_orc
gr::log :WARN: fractional_interpolator_cc0 - fractional_interpolator is deprecated. Please use fractional_resampler instead.
Key: 'ad6a3ec2b442e400'
Configuration: '0B'
Configuration TS: 0
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.
coarse tuned to: 223364 Hz
sch.c:260 ERR: conv_decode 11
coarse tuned to: 210280 Hz
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 12
sch.c:260 ERR: conv_decode 10
sch.c:260 ERR: conv_decode 12
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 12
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 12
sch.c:260 ERR: conv_decode 9
sch.c:260 ERR: conv_decode 12
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 9
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 11
sch.c:260 ERR: conv_decode 10

------
Any Idea on how to resolve this?

I am newbie to SDRs, any guidance suggestions are appreciated
Many Thanks
-sk80

[jynik]

I know absolutely nothing about airprobe, but a couple items seem suspect to me...

The lowest filter bandwidth setting on the bladeRF (technically, on the LMS6002D transceiver) is 1.5 MHz. This filter rolls off into full rejection at around 2 MHz. Therefore, if you're set your sample rate to be lower than 2e6 (you're using 1e6), you'll likely see aliases and noise folding in. So to start, I suggest using a higher sample rate. You might need to first take a look at the code or flowgraph to ensure nothing is hard-coded for the 1e6 sample rate you're using.

I don't recall what the channel bandwidth is for GSM. If the bladeRF minimum 1.5 MHz is too wide, you might need to plop down a FIR filter into the code.

I realize this isn't much help, but hopefully it gives you something to bring to folks with more knowledge of GSM and airprobe.

- Jon

[sk80]

Thanks Jon,

Sorry for late reply, I was not with my bladeRF for quite a while.
I tried 2e6 and also 3e6, but unfortunately result was the same.

I will update if I am able to solve this.

Thanks again,
Sachin