PSK Real Time Voice Tx/Rx

GNU Radio
1

Hello, I am working on a real time voice Tx/Rx using GNU Radio as
software
and a USRP E110. I’m trying to do a QPSK Modulation and I have consulted
several models and forums and it seems everything is okay, however at
the
moment of receiving signal, the audio on the receiver is breaking up,
and I
want the audio sounds good. I thought it might be because of some errors
in
synchronism and carrier recovery, so I added the block MPSK Reciever,
without any changes in the audio output. Is anything I am missing? or Is
any calculation or number wrong?

Could it be because of lack in processing? because I’ve tried the same
model with GMSK mod/demod blocks and the voice sounds good. I’ve
attached
the flowgraphs of the Tx and Rx side for a better understanding.

I really appreciate your help and I look forward your reply.
Regards.
Marqo

P.S. I’ve also read that at the moment of involving blocks that work
with
hardware (USRP Sink/Source) I have to skip the Throttle blocks, is that
true?

2

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3

On 01/13/2014 03:31 PM, Marqo Torres wrote:

model with GMSK mod/demod blocks and the voice sounds good. I’ve attached
the flowgraphs of the Tx and Rx side for a better understanding.

Do you see any O/U’s from the flowgraphs? If so which flowgraph?

Philip

4

On 01/13/2014 04:38 PM, Marqo Torres wrote:

I’ve attached the flowgraphs of the Tx and Rx models.

Regards
Marqo.

Those UUUUU mean that your graph isn’t able to to keep up with the
notional sample-rate, either because of computational sluggishness, or
because you aren’t resampling appropriately within your flow-graph so
that the hardware is receiving samples at the correct rate.