Hi Nick,
Thanks for your quick reply!
I have to use a 10M sampling rate in my case, but due to computer
constrain, modes_rx will cause overflow when used directly with -r
10000000. I gauss it's because it's sampling data in float? I am using a
GPSDO with USRP.
So I record data in short at 10M sampling rate, convert from short to float
and then input to modes_rx. The output looks like this:
{{{
(27 0.00000000) Type 0 (short A-A surveillance) from dc2ed9 at 45900ft
(speed 600-1200kt)
(23 0.00000000) Type 4 (short surveillance altitude reply) from 2443b0 at
59800ft (GROUND ALERT)
(24 0.00000000) Type 4 (short surveillance altitude reply) from 3b1fc3 at
3200ft (SPI)
(21 0.00000000) Type 21 link capability report from d5ca0e: ACS: 0xda21,
BCS: 0xc923, ECS: 0xee, continues 8 ident 123e
(22 0.00000000) Type 5 (short surveillance ident reply) from 5ad8b4 with
ident 728 (GROUND ALERT)
(37 0.00000000) Type 17 BDS0,9-1 (track report) from 7805dd with velocity
218kt heading 238 VS -1664
}}}
The timestamp are all zeros.
Another question is that if I use modes_rx, how to save the sampled complex
baseband signal? Is the data saved somewhere that I've missed?
Best regards,
Cheng Chi
On Mon, Jan 27, 2014 at 3:57 PM, Nick Foster <bistrom...@gmail.com> wrote:
> On Sun, Jan 26, 2014 at 11:48 PM, Cheng Chi <ch000...@e.ntu.edu.sg> wrote:
>
>> Hi,
>>
>> I am using gr-air-modes for decoding the air plane signal with USRP. I've
>> successfully used the "modes_rx" and "modes_gui" for decoding the mode-S
>> packets.
>>
>> However, it seems that the modes_rx or modes_gui can't provide the
>> timestamp of the mode-S packets being decoded. Is there any option that I
>> can set to timestamp the mode-S packet? The reason I want this timestamp
>> function is that I want to know the decoded packet data correspond to which
>> part of the raw data (complex baseband data samples).
>>
>
> If you're using a USRP, you should be getting a timestamp. It's the second
> number printed, as in the following:
> (-14 *1.29258827811*) Type 0 (short A-A surveillance) from ab2984 at
> 3000ft
>
> If you are using a GPSDO with your USRP, the printed time will be in UTC
> seconds. Otherwise, it will be in seconds since the application started
> running.
>
> --n
>
>
>
>>
>> Thank you for any help you can provide in this situation.
>>
>> I found that there's a file called "air_modes_preamble.cc" seems to
>> provide the timestamp function. Does anyone know how to use this file
>> separately?
>>
>> Best regards,
>> Cheng Chi
>>
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