# Fading channel in GNURadio **URL:** \ **Category:** GNU Radio\ **Created:** [March 21, 2013, 8:46pm UTC](https://www.ruby-forum.com/t/fading-channel-in-gnuradio/227626 "2013-03-21T20:46:32Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\ **Post date:** [March 21, 2013, 8:46pm UTC](https://www.ruby-forum.com/t/fading-channel-in-gnuradio/227626/1 "2013-03-21T20:46:32Z")
I’m trying to make a block for fading channel model using hierarchical block. class channel(gr.hier\_block2): def **init** (self): gr.hier\_block2. **init** (self, “channel”, gr.io\_signature(1, 1, gr.sizeof\_float), gr.io\_signature(1, 1, gr.sizeof\_gr\_complex)) ``` self.taps = generate_taps() self.filt = filter.fir_filter_ccc(1, self.taps) self.connect(self, self.filt, self) def generate_taps(): n_taps = random.randint(1, 10) r_taps = random.rand(n_taps) i_taps = random.rand(n_taps) return r_taps + 1j*i_taps ``` I want the block to be able to update the channel filter taps in run time. Can I do that? Can I define a function in the class so that the filter taps are updated for every 5 seconds? Thank you. ---
**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\ **Post date:** [March 21, 2013, 8:55pm UTC](https://www.ruby-forum.com/t/fading-channel-in-gnuradio/227626/2 "2013-03-21T20:55:53Z")
On 03/21/2013 03:45 PM, Manu T S wrote: > ``` > self.taps = generate_taps() > > ``` > > I want the block to be able to update the channel filter taps in run > time. Can I do that? > Can I define a function in the class so that the filter taps are > updated for every 5 seconds? The set\_taps function gives you access to this from the top\_block level. In that case, your main thread would be updating the block’s taps using a while loop with sleep(5). You could also make a block class that inherits from fir\_filter\_ccc or channel\_model and change the taps within the work function every N seconds: every time (ninput\_items / samp\_rate) % N == 0. I hope that’s enough info to point you in the right direction. > Thank you. > > – > Manu T S > > * * * > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) * * * _Sean M. Nowlan_ Research Engineer I ICL/CNSD Georgia Tech Research Institute 250 14th St NW, Suite 470 Atlanta, GA 30318 404.407.7952 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![Manu\_T\_S](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/ea5d25/32.png) [@Manu\_T\_S](https://www.ruby-forum.com/u/Manu_T_S)\ **Post date:** [March 22, 2013, 10:41am UTC](https://www.ruby-forum.com/t/fading-channel-in-gnuradio/227626/3 "2013-03-22T10:41:15Z")
On Thu, Mar 21, 2013 at 03:54:48PM -0400, Sean Nowlan wrote: > every N seconds: every time (ninput\_items / samp\_rate) % N == 0. I hope that’s > enough info to point you in the right direction. Note that will change taps in wall time, not sample time. MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association