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Re: [Discuss-gnuradio] Using Correlate Estimation with hardware

From: Marcus Müller
Subject: Re: [Discuss-gnuradio] Using Correlate Estimation with hardware
Date: Sat, 26 Aug 2017 18:33:49 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

Hi Sebastian,

well, it would sound like you've discovered the multipath channel!

I don't really understand what you mean with "Modulate vector is called"; what /is/ "Modulate vector"?

You can actually simply attach small files to emails to the list. Such a simple GRC file would certainly not upset us :)

Best regards,

On 26.08.2017 18:10, Sebastian wrote:



Hi all,


i run into trouble using the correlate estimation block.


As far as i understand this blocks is used to search for a praeamble which is modulated and filtered with match filter.

To achieve this i used modulate vector. I used this block like it`s done in the corr_est exapmles provided in  /gnuradio/gr-digital/examples/.


Using no UHD but a channel modell everything works fine having clear correlation peak.

Using it with hardware device it doesn`t work anymore, having more peaks avaiable.


My flowgraph is very simple:


Vector_source (using prae+data as vector tagged with tx_sob and tx_eob) -> constellation Modulator(default-QPSK-object) -> stream mux with null_source for break -> uhd sink(sync = PC_clock)


Uhd source (sync = PC_clock) -> low_pass -> corr_est(modulated_vector, 0.9) -> Pll-clock-sync -> Costas Loop -> constellation-demodulator -> float_to_char -> qt time sink



Modulate vector is called with default-qpsk-object as constellation object and [1] as filter taps which i think is right.

The praeamble i am using is the one provided in the examples, so it should be ok too.


I dont have that much experience in this topic so I hope somebody is able to help me.

I am looking forward to hearing from you and thank you in advance.





PS : I am not sure where and how to provide the flowgraph itself but i´ll try to do it asap.





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