Johnathan Corgan wrote:
> On Tue, Dec 16, 2008 at 8:26 AM, Bruhtesfa Ebrahim
> <li...@ruby-forum.com> wrote:
>> 1. I tried to monitor the impulse response of the room for 5 sec. So,
>> according to the discussion above(i.e since the FPGA computes impulse
>> response of length 4095,32MHZ in 0.5sec), I will have 10 impulse
>> response vectors in 5sec. But when i set { samples = 10 *
>> self._length**2 in usrp_sounder_rx.py } and run the code, it takes about
>> 160 seconds to complete. So, I am confused. Does the recorded impulse
>> response correspond to 5sec or 160sec?
>
> I don't understand how you've modified the script to collect 5 seconds
> of data.
In the python code usrp_sounder_rx.py the number of impulse response
vectors is set to 100 by default. I have seen that from the statement (
samples = 100 * self._length**2) in class usrp_sounder_rx(gr.top_block).
I have also experiment with it.Then,I see by reading the file in matlab
that it really records 100 impulse response vectors or 100*4095 sampled
values.
In my case, I want to use PN code of degree 12 and 32MHZ chip rate.And
this takes 4095*4095/32MHZ=0.5sec to record a single impulse response
vector (according to our previous discussion). Now, If I want to monitor
the room for 5sec, I need 5sec/0.5sec=10 impulse response vectors.
So, I modified the PN code degree, chip rate and number of impulse
response vectors in usrp_sounder_rx.py. To change the number of impulse
response vectors to 10, I just used (samples = 10 * self._length**2)
instead of the default (samples = 100 * self._length**2)in the code.
But, When I run the code, it takes about 160sec to complete instead of
the expected 5sec.
So, I get confused? Is there a mistake I made ?
or, is there any factor that can delays the computation and recording of
a single impulse response vector slower than 4095*4095/32MHZ?
>> 2. As, expected there is frequency offset on the received impulse
>> response. what can i do to synchronize transmitter and receiver
>> daughter boards? Thanks!
>
> You will need to use a stable time reference like a GPSDO on both the
> transmitter and receiver.
Is there any method of synchronization by just wiring the transmit and
receive daughter boards together?
Thanks for your help!
Bruhtesfa
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