# Frame delay synchronization issue

**URL:** <https://www.ruby-forum.com/t/frame-delay-synchronization-issue/241221>\
**Category:** GNU Radio\
**Created:** [May 19, 2014, 1:25pm UTC](https://www.ruby-forum.com/t/frame-delay-synchronization-issue/241221 "2014-05-19T13:25:08Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![musicdenotation](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea666f/32.png) [@musicdenotation](https://www.ruby-forum.com/u/musicdenotation)\
**Post date:** [May 19, 2014, 1:25pm UTC](https://www.ruby-forum.com/t/frame-delay-synchronization-issue/241221/1 "2014-05-19T13:25:08Z")

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Hi all,  
I am using QPSK Mod and demod I have issue of how to synchronize  
my  
frame means how to remove delays from my received data in using GRC  
block  
my flow graph is attached with this mail. I am trying to use packet  
encoder  
and decoder for frame synchronization but it is not working with my mod  
and  
demod.  
Regards,  
Irfan U.

---

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**Author:** ![Irfan\_U](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/57b2e6/32.png) [@Irfan\_U](https://www.ruby-forum.com/u/Irfan_U)\
**Post date:** [May 20, 2014, 11:07am UTC](https://www.ruby-forum.com/t/frame-delay-synchronization-issue/241221/2 "2014-05-20T11:07:26Z")

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On 19.05.2014 13:23, Irfan U. wrote:

> Hi all,  
> I am using QPSK Mod and demod I have issue of how to synchronize  
> my frame means how to remove delays from my received data in using GRC  
> block my flow graph is attached with this mail. I am trying to use  
> packet encoder and decoder for frame synchronization but it is not  
> working with my mod and demod.

Hey Irfan,

I’m not sure phase is preserved in your flow graph. I recommend you  
start with a few components and slowly add things until you realize  
where the problem lies. Make use of the GUI sinks to check out signals  
and constellations.

Martin

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<div class="post-metadata">

**Author:** ![Irfan\_U](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/57b2e6/32.png) [@Irfan\_U](https://www.ruby-forum.com/u/Irfan_U)\
**Post date:** [May 20, 2014, 3:16pm UTC](https://www.ruby-forum.com/t/frame-delay-synchronization-issue/241221/3 "2014-05-20T15:16:13Z")

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On Tue, May 20, 2014 at 5:06 AM, Martin B.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)wrote:

> Hey Irfan,
> 
> I’m not sure phase is preserved in your flow graph. I recommend you start  
> with a few components and slowly add things until you realize where the  
> problem lies. Make use of the GUI sinks to check out signals and  
> constellations.
> 
> Martin

Indeed. One of the reasons we often use differential encoding.

Tom