# Channel Model Block in GNU radio

**URL:** <https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234640>\
**Category:** GNU Radio\
**Created:** [March 19, 2015, 6:57am UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234640 "2015-03-19T06:57:10Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [March 19, 2015, 6:57am UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234640/1 "2015-03-19T06:57:10Z")

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Hi,

I am working on the channel model block in GNU radio. I am confused in  
setting up the taps.I have a random source that undergoes a QPSK  
modulation  
at 4 samples per second.Could you please explain me the concept under  
setting the tap values.

I am supposed to use a polyphase clock synchronizer followed by a CMA  
equalizer for analyzing the channel response.

Looking forward for your reply.

Thanks  
Merry

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**Author:** ![mjm\_11](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ba8739/32.png) [@mjm\_11](https://www.ruby-forum.com/u/mjm_11)\
**Post date:** [March 21, 2015, 3:32am UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234640/2 "2015-03-21T03:32:57Z")

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Hi Merry,

> I want to know how to define the parameter ‘taps’ in the channel model  
> blocks.I am considering a 4 tap system.  
> The taps _define_ what your channel is. We can’t tell you what taps your  
> channel has – that is completely defined by what you want your channel  
> to be.  
> Since you already know that you’re considering a 4-tap system: Take your  
> channel impulse response, and put it in your taps field like  
> [h\_0, h\_1, h\_2, h\_3]  
> with h\_n being the nth coefficient of your tapped delay line channel  
> model.

Greetings,  
Marcus