# Adding channel effects to an input in GNURADIO

**URL:** <https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066>\
**Category:** GNU Radio\
**Created:** [May 11, 2014, 11:42pm UTC](https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066 "2014-05-11T23:42:12Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [May 11, 2014, 11:42pm UTC](https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066/1 "2014-05-11T23:42:12Z")

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Hi all,

(Ubuntu 13.04, GNURADIO 3.7)

I have a question regarding the channel models. As far I know the  
channel function must be convolved (convolution) with the input to get  
the output like this:

out = conv(in,channel)

In GNURADIO I can not find this convolution or any filter to do that. I  
am looking inside this folder: gnuradio/gr-channels/lib.  
How is this process done in GNURADIO?

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**Author:** ![nesazeri](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e19adc/32.png) [@nesazeri](https://www.ruby-forum.com/u/nesazeri)\
**Post date:** [May 12, 2014, 9:55am UTC](https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066/2 "2014-05-12T09:55:17Z")

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On 11.05.2014 23:41, Nasi wrote:

> How is this process done in GNURADIO?  
> Nasi,

there’s all kinds of filtes and channel models in GNU Radio. In GRC, you  
can search for them; in the source tree, they’d be under gr-filter and  
gr-channels, respectively. Also check the corresponding manual pages.

M

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**Author:** ![nesazeri](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e19adc/32.png) [@nesazeri](https://www.ruby-forum.com/u/nesazeri)\
**Post date:** [May 12, 2014, 10:29am UTC](https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066/3 "2014-05-12T10:29:43Z")

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Channel models there do not use any filtering.  
Isnt it like this?  
I did not see any filtering in source files of channels.

Sent from [Mail.Ru](http://Mail.Ru) app for iOS

Montag, 12. Mai 2014 09:53 +0200 from Martin B.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):  
On 11.05.2014 23:41, Nasi wrote:

> How is this process done in GNURADIO?  
> Nasi,

there’s all kinds of filtes and channel models in GNU Radio. In GRC, you  
can search for them; in the source tree, they’d be under gr-filter and  
gr-channels, respectively. Also check the corresponding manual pages.

M

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**Author:** ![nesazeri](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e19adc/32.png) [@nesazeri](https://www.ruby-forum.com/u/nesazeri)\
**Post date:** [May 12, 2014, 10:43am UTC](https://www.ruby-forum.com/t/adding-channel-effects-to-an-input-in-gnuradio/241066/4 "2014-05-12T10:43:18Z")

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On 12.05.2014 10:28, Nasi wrote:

> Channel models there do not use any filtering.  
> Isnt it like this?  
> I did not see any filtering in source files of channels.

Filter == convolution == multipath channels.  
See channel\_model\_impl.cc.

Cheers,  
M