Re: [Discuss-gnuradio] Problem with USRP!

[huzaifazafar108]

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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> 
> 
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