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Re: [Discuss-gnuradio] Correlation Estimation Block Oddity

From: Johnathan Corgan
Subject: Re: [Discuss-gnuradio] Correlation Estimation Block Oddity
Date: Tue, 28 Apr 2015 13:41:10 -0700

On Tue, Apr 28, 2015 at 12:48 PM, Richard Bell <address@hidden> wrote:
When you mentioned I should remove leading or trailing zeros from the Correlation Estimator symbols field, how would you go about doing this if you used the modulate vector block as done in the example? I'm stuck on this.

The group delay in the pulse shaping filter (in this case, RRC) causes these leading zeros.  This is something I'd like to figure out a "proper" solution for, but my quick hack that works pretty well is to duplicate the PN sequence as it goes into modulate_vector, then take only the second half of the samples of the output for the correlation block.

This then "pre-fills" the filter with data that is arguably the right spectral shape, and the resulting second-half vector works much better than the original way.

Again, this is a quick hack, but it works well. 

Johnathan Corgan
Corgan Labs - SDR Training and Development Services

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