# Channel Model Block in GNU radio

**URL:** <https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234642>\
**Category:** GNU Radio\
**Created:** [March 19, 2015, 6:58am UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234642 "2015-03-19T06:58:00Z")\
**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, 6:58am UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234642/1 "2015-03-19T06:58:00Z")

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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 19, 2015, 1:57pm UTC](https://www.ruby-forum.com/t/channel-model-block-in-gnu-radio/234642/2 "2015-03-19T13:57:00Z")

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Hi Merry,

the taps characterize the channel you want to simulate, so you will need  
to calculate these based on your mathematical channel model. The  
classical multipath channel model is a tapped-delay line-model, and that  
kind of directly maps to the concept of filter taps.

Are you sure you do 4 samples per second? That seems to be incredible  
little, especially when working with channel impulse responses.

Greetings,  
Marcus