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Echo cancellation known impulse response

Started by sigmonde January 28, 2014
I've implemented a conventional echo cancellation solution using  LMS ,
however my application has a known impulse response which is static. Am I
missing a trick here?

Any suggestions great fully received.

	 

_____________________________		
Posted through www.DSPRelated.com
On Tue, 28 Jan 2014 14:50:26 -0600, "sigmonde" <10104@dsprelated>
wrote:

>I've implemented a conventional echo cancellation solution using LMS , >however my application has a known impulse response which is static. Am I >missing a trick here? > >Any suggestions great fully received.
Potentially. If the response is known and static for all time, then you don't really need an adaptive algorithm; you can set the taps and forget them. An adaptive system won't necessarily hurt anything, other than the burden of the additional complexity and some retraining time whenever it wakes up. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
>On Tue, 28 Jan 2014 14:50:26 -0600, "sigmonde" <10104@dsprelated> >wrote: > >>I've implemented a conventional echo cancellation solution using LMS , >>however my application has a known impulse response which is static. Am
I
>>missing a trick here? >> >>Any suggestions great fully received. > >Potentially. If the response is known and static for all time, then >you don't really need an adaptive algorithm; you can set the taps and >forget them. An adaptive system won't necessarily hurt anything, >other than the burden of the additional complexity and some retraining >time whenever it wakes up. > > >Eric Jacobsen >Anchor Hill Communications >http://www.anchorhill.com >
Thanks Eric that's what I'd hoped for. However, I was wondering if there was some clever way of generating the taps directly from the. Impulse response? _____________________________ Posted through www.DSPRelated.com
Is the echo path acoustic? If so, it's unlikely to be truly static. Acoustic paths have a funny way of not being LTI even though we like to think of them that way. Also the speaker will be affected by temperature, aging, etc. 

Bob
>Is the echo path acoustic? If so, it's unlikely to be truly static.
Acoustic paths have a funny way of not being LTI even though we like to think of them that way. Also the speaker will be affected by temperature, aging, etc.
> >Bob >
The path is a steel conduit, it's impulse response is measured every wake up cycle. C _____________________________ Posted through www.DSPRelated.com
>>Is the echo path acoustic? If so, it's unlikely to be truly static. >Acoustic paths have a funny way of not being LTI even though we like to >think of them that way. Also the speaker will be affected by temperature, >aging, etc. >> >>Bob >> >The path is a steel conduit, it's impulse response is measured every
wake
>up cycle. >C > >_____________________________ >Posted through www.DSPRelated.com >
Sorry should have added that it is an acoustic transmission system C _____________________________ Posted through www.DSPRelated.com
On Wed, 29 Jan 2014 04:53:49 -0600, "sigmonde" <10104@dsprelated>
wrote:

>>>Is the echo path acoustic? If so, it's unlikely to be truly static. >>Acoustic paths have a funny way of not being LTI even though we like to >>think of them that way. Also the speaker will be affected by temperature, >>aging, etc. >>> >>>Bob >>> >>The path is a steel conduit, it's impulse response is measured every >wake >>up cycle. >>C >> >>_____________________________ >>Posted through www.DSPRelated.com >> >Sorry should have added that it is an acoustic transmission system >C
Is the signal transmitted through the air in the pipe or through the pipe itself? Not that it matters, but I'm curious. Also, if you measure the IPR whenever the systems wakes up, it may benefit from an adaptive algorithm, and then just freeze the taps once you're confident that it's trained. This is a fairly common thing to do. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
>On Wed, 29 Jan 2014 04:53:49 -0600, "sigmonde" <10104@dsprelated> >wrote: > >>>>Is the echo path acoustic? If so, it's unlikely to be truly static. >>>Acoustic paths have a funny way of not being LTI even though we like to >>>think of them that way. Also the speaker will be affected by
temperature,
>>>aging, etc. >>>> >>>>Bob >>>> >>>The path is a steel conduit, it's impulse response is measured every >>wake >>>up cycle. >>>C >>> >>>_____________________________ >>>Posted through www.DSPRelated.com >>> >>Sorry should have added that it is an acoustic transmission system >>C > >Is the signal transmitted through the air in the pipe or through the >pipe itself? Not that it matters, but I'm curious. > >Also, if you measure the IPR whenever the systems wakes up, it may >benefit from an adaptive algorithm, and then just freeze the taps once >you're confident that it's trained. This is a fairly common thing to >do. > > > > >Eric Jacobsen >Anchor Hill Communications >http://www.anchorhill.com >
Thanks Eric Yes I'll try locking the taps It's a through steel communications system where the channel has a transfer function very similair in structure to a comb filter. Colin _____________________________ Posted through www.DSPRelated.com
On Thu, 30 Jan 2014 19:19:01 -0600, "sigmonde" <10104@dsprelated>
wrote:

>>On Wed, 29 Jan 2014 04:53:49 -0600, "sigmonde" <10104@dsprelated> >>wrote: >> >>>>>Is the echo path acoustic? If so, it's unlikely to be truly static. >>>>Acoustic paths have a funny way of not being LTI even though we like to >>>>think of them that way. Also the speaker will be affected by >temperature, >>>>aging, etc. >>>>> >>>>>Bob >>>>> >>>>The path is a steel conduit, it's impulse response is measured every >>>wake >>>>up cycle. >>>>C >>>> >>>>_____________________________ >>>>Posted through www.DSPRelated.com >>>> >>>Sorry should have added that it is an acoustic transmission system >>>C >> >>Is the signal transmitted through the air in the pipe or through the >>pipe itself? Not that it matters, but I'm curious. >> >>Also, if you measure the IPR whenever the systems wakes up, it may >>benefit from an adaptive algorithm, and then just freeze the taps once >>you're confident that it's trained. This is a fairly common thing to >>do. >> >> >> >> >>Eric Jacobsen >>Anchor Hill Communications >>http://www.anchorhill.com >> >Thanks Eric > >Yes I'll try locking the taps > >It's a through steel communications system where the channel has a >transfer function very similair in structure to a comb filter. > >Colin
Ah, interesting. Sounds like a fun application. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
On Thursday, January 30, 2014 8:19:01 PM UTC-5, sigmonde wrote:
> >On Wed, 29 Jan 2014 04:53:49 -0600, "sigmonde" <10104@dsprelated> > > >wrote: > > > > > >>>>Is the echo path acoustic? If so, it's unlikely to be truly static. > > >>>Acoustic paths have a funny way of not being LTI even though we like to > > >>>think of them that way. Also the speaker will be affected by > > temperature, > > >>>aging, etc. > > >>>> > > >>>>Bob > > >>>> > > >>>The path is a steel conduit, it's impulse response is measured every > > >>wake > > >>>up cycle. > > >>>C > > >>> > > >>>_____________________________ > > >>>Posted through www.DSPRelated.com > > >>> > > >>Sorry should have added that it is an acoustic transmission system > > >>C > > > > > >Is the signal transmitted through the air in the pipe or through the > > >pipe itself? Not that it matters, but I'm curious. > > > > > >Also, if you measure the IPR whenever the systems wakes up, it may > > >benefit from an adaptive algorithm, and then just freeze the taps once > > >you're confident that it's trained. This is a fairly common thing to > > >do. > > > > > > > > > > > > > > >Eric Jacobsen > > >Anchor Hill Communications > > >http://www.anchorhill.com > > > > > Thanks Eric > > > > Yes I'll try locking the taps > > > > It's a through steel communications system where the channel has a > > transfer function very similair in structure to a comb filter. > > > > Colin > > > > _____________________________ > > Posted through www.DSPRelated.com
You can use the last locked values as the starting point for the next training session. You should be able to see how much it (the filter) varies from session to session, and then you will know if adaptation is warranted. Clay