Re: [Discuss-gnuradio] "Error rate" block with USRP

[Tom Rondeau]

On Wed, Apr 16, 2014 at 3:38 PM, Azza <address@hidden> wrote:

Tom Rondeau-2 wrote
> On Wed, Apr 16, 2014 at 2:06 PM, Azza &lt;

> azza.ben.mosbah@

> &gt; wrote:
>
>> Tom Rondeau-2 wrote
>> > On Wed, Apr 16, 2014 at 10:57 AM, Azza &lt;
>>
>> > azza.ben.mosbah@
>>
>> > &gt; wrote:
>> >
>> >> Thank you.
>> >> I have taken out the throttle block and add an AGC block at the
>> receiver.
>> >> To proceed with the synchronization, should I use a Constellation
>> >> Receiver
>> >> block or a Polyphase Clock Sync block ?
>> >>
>> >> Kind regards,
>> >> Azza
>> >>
>> >
>> >
>> > You'll actually need both. AGC -> clock sync -> constellation receiver
>> > (phase/freq recovery and decoding).
>> >
>> > Also, please reply in-line with the rest of the message. By cutting off
>> > the
>> > other part of our conversation makes it difficult for others to follow
>> the
>> > thread.
>> >
>> > Tom
>>
>> Thank you.
>> I have added modifications to my flowgraph:

>> &lt;http://gnuradio.4.n7.nabble.com/file/n47630/gnu-ber-modified.png&gt;

>> But, I am still confused about minimum/maximum frequency deviation in the
>> Constellation Receiver block. How should it be set?
>>
>> Regards,
>> Azza
>>
>
>  Those are settings to keep the frequency sync from walking away, in
> normalized frequency. +1 and -1 should work fine.
>
> Tom
>

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Tom,

I still found BER=0.5, however the error output of the Constellation
Receiver block gives 0.

Regards,
Azza

Azza,

Maybe take a step back from trying to calculate the BER. Make sure you have a transmitting system and receiver system that are working correctly. At the receiver, the first thing to do is make sure you're getting a proper constellation. If so, you should be able to extract the bits to compare them. And by this, I mean make two flowgraphs for the tx and rx sides so you're not confusing yourself by trying to tie everything together.

Also, make sure you are either using differential modulation encoding to correct for unknown phase offsets or that you are somehow correcting for this possibility. Then, you need to make sure you're getting your frames through. There will be a delay between what you transmit over the air and when you receive it. You'll have to account for this, too.

Tom