Re: [Discuss-gnuradio] Problem with USRP!

[huzaifazafar108]

Dear John,

Waiting for your response...

And the reason for using TX/RX is that we connected the antennas on TX/RX
ports on the daughtercard (in both transmitter and receiver).

Thanks,
Huzaifa


John Malsbury wrote:
> 
> A few more things:
> 
> 1)  You have both the receive and transmit portions assigned to TX/RX.  
> This only works if you run in half-duplex mode and stop streaming to the 
> USRP.  This is not the case.
> 2)  Note the difference between sample rate, symbol rate, and bit rate.
> 
>      symbol_rate = sample_rate / samples_per_symbol
>      bit_rate = sample_rate/bits_per_symbol
> 
> I think there are issues with packing/unpacking of bits.  The 
> requirements for packing and unpacking aren't completely consistent 
> across the mod/demods within GNU Radio.  Let me experiment real quick 
> and get back to you.
> 
> -John
> 
> 
> On 04/08/2012 02:34 PM, huzaifazafar108 wrote:
>> Dear Marcus,
>>
>> I truly appreciate your prompt reply. However, I am not sure what should
>> I
>> put in the 'modulus' field of the block. By hit and trial, wrong outputs
>> are
>> emerging. Please guide.
>>
>> Best Regards,
>> Huzaifa
>>
>>
>>
>> Marcus D. Leech wrote:
>>>> We just removed the throttle blocks and the same problem remains.
>>>> Please
>>>> let
>>>> us know how to achieve symbol synchronization.
>>>>
>>>>
>>> Well, you're using DPSK, but not using a differential encoder on the TX
>>> side, nor a differential decoder on the RX side.
>>>
>>>> huzaifazafar108 wrote:
>>>>> Dear John,
>>>>>
>>>>> Thank you for such a prompt reply. Okay, we will remove the throttle
>>>>> blocks just now. But can you guide us how to achieve symbol
>>>>> synchronization then?
>>>>>
>>>>> Best Regards,
>>>>> Huzaifa
>>>>>
>>>>>
>>>>>
>>>>> John Malsbury wrote:
>>>>>> You do not need to use throttles when using a UHD sink/source,
>>>>>> because
>>>>>> the device provides timing for the flowgraph.
>>>>>>
>>>>>> Remove the throttles and try again.  If you still see the failure I'd
>>>>>> say you are not achieving symbol sync.
>>>>>>
>>>>>> -John
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 04/08/2012 01:58 PM, Huzaifa Zafar wrote:
>>>>>>> Dear all,
>>>>>>>
>>>>>>> I am working with 3 people on a project involving GNU Radio and
>>>>>>> USRP1.
>>>>>>> We have tried to implement a simple point to point digital
>>>>>>> communication system in GRC involving DQPSK modulation. Using a
>>>>>>> vector
>>>>>>> source we are sending a finite stream of zeros and ones (the vector
>>>>>>> source has Repeat set to yes). On the receiver side, what we receive
>>>>>>> is really very strange: The same stream of zeros and ones, but with
>>>>>>> extra zeros in between our actual data. For example, we send three
>>>>>>> ones and three zeros, but what we receive is a one followed by seven
>>>>>>> zeros, another one followed by seven zeros, another one followed by
>>>>>>> seven zeros, and then a zero followed by seven zeros e.t.c. We tried
>>>>>>> to experiment more by using the 'KEEP 1 in N' block and the
>>>>>>> 'DECIMATING FIR FILTER', but things are not working out the way they
>>>>>>> should.
>>>>>>>
>>>>>>> I am also attaching a snapshot of the .grc file for your reference.
>>>>>>> Please tell us the reason why these extra zeros are present between
>>>>>>> our data bits, and the way to combat this effect (remember that the
>>>>>>> decimating fir filter and keep 1 in N block are not showing the
>>>>>>> desired output). Any kind of help is appreciated in advance.
>>>>>>>
>>>>>>> -- 
>>>>>>> Huzaifa Zafar
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>> _______________________________________________
>>>>>> Discuss-gnuradio mailing list
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>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>>>>
>>>>>>
>>>
>>> -- 
>>> Marcus Leech
>>> Principal Investigator
>>> Shirleys Bay Radio Astronomy Consortium
>>> http://www.sbrac.org
>>>
>>>
>>>
>>> _______________________________________________
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>>>
>>>
> 
> 
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