We are a voip terminating company, we're using Channelbank with FXS modules, Rhino, CAC, etc.. What we're wondering is, is how to would you echo cancel a channelbank. Of course we're realizing that cancel'ing on the T1 (on Ast) does no good (we think?) because the analog conversion is at the channelbank. Suggestions? Lowering the gain helps but we're looking for a real solution to this. Thanks. <PSTN?> -- <VOIP Network> -- <Asterisk> -(T1)- <channel bank> -- <analog> ^echo heard
On Sat, 29 Jan 2005, Matt Schulte wrote:> We are a voip terminating company, we're using Channelbank with FXS > modules, Rhino, CAC, etc.. What we're wondering is, is how to would you > echo cancel a channelbank. Of course we're realizing that cancel'ing on > the T1 (on Ast) does no good (we think?) because the analog conversion > is at the channelbank. Suggestions? Lowering the gain helps but we're > looking for a real solution to this. Thanks. > > <PSTN?> -- <VOIP Network> -- <Asterisk> -(T1)- <channel bank> -- > <analog> > ^echo heardIf you hear the echo at the marked analog endpoint then it is almost certainly far end echo. This is nearly almost present when calling an analog phone at the far end. On short links without VoIP the reflected energy will sound like a nice sidetone. For longer links (e.g. international) and VoIP you need an echo canceler in the call path. Since you have an analog phone attached to an endpoint there may be an echo heared from the pstn as well. Both these echos can be reduced by adding an echo canceler that has its tail (i.e. subtracts the right amount of the slightly delayed transmitted signal from the received signal) into both directions. Asterisk can act as such an echo canceler. Asterisk may not be the very best echo canceler available, but it may be good enough. Try it and see. Peter
Agh, what I meant was the echo is heard from the PSTN side. It seems echo canceling on the T1 (going to channelbank) does nothing, I'm assuming because the T1 is "digital" and the channelbank is the traversal from digital to analog. -----Original Message----- From: Peter Svensson [mailto:psvasterisk@psv.nu] Sent: Saturday, January 29, 2005 12:49 PM To: Asterisk Users Mailing List - Non-Commercial Discussion Subject: Re: [Asterisk-Users] Channel Bank Echo On Sat, 29 Jan 2005, Matt Schulte wrote:> We are a voip terminating company, we're using Channelbank with FXS > modules, Rhino, CAC, etc.. What we're wondering is, is how to would > you echo cancel a channelbank. Of course we're realizing that > cancel'ing on the T1 (on Ast) does no good (we think?) because the > analog conversion is at the channelbank. Suggestions? Lowering the > gain helps but we're looking for a real solution to this. Thanks. > > <PSTN?> -- <VOIP Network> -- <Asterisk> -(T1)- <channel bank> -- > <analog> > ^echo heardIf you hear the echo at the marked analog endpoint then it is almost certainly far end echo. This is nearly almost present when calling an analog phone at the far end. On short links without VoIP the reflected energy will sound like a nice sidetone. For longer links (e.g. international) and VoIP you need an echo canceler in the call path. Since you have an analog phone attached to an endpoint there may be an echo heared from the pstn as well. Both these echos can be reduced by adding an echo canceler that has its tail (i.e. subtracts the right amount of the slightly delayed transmitted signal from the received signal) into both directions. Asterisk can act as such an echo canceler. Asterisk may not be the very best echo canceler available, but it may be good enough. Try it and see. Peter _______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
On January 29, 2005 12:31 pm, Matt Schulte wrote:> We are a voip terminating company, we're using Channelbank with FXS > modules, Rhino, CAC, etc.. What we're wondering is, is how to would you > echo cancel a channelbank. Of course we're realizing that cancel'ing on > the T1 (on Ast) does no good (we think?) because the analog conversion > is at the channelbank. Suggestions? Lowering the gain helps but we're > looking for a real solution to this. Thanks. > > <PSTN?> -- <VOIP Network> -- <Asterisk> -(T1)- <channel bank> -- > <analog> > ^echo heardIf the echo is being heard on the far side then you are generating it at your hybrid. Your diagram is not clear since it was wrapped. I have used the Adit600 and Access Bank 1s with great success -- they do not generate echo (i.e. nobody we've called has heard echo) -- we do, however, hear echo from time to time, even on our PRI. Asterisk's echo cancellation is either getting disabled accidentally or it is not working worth a damn. :-( You can use Tellabs echo cancellation units on T1 and PRI -- these are carrier-grade hardware echo cancellers. I haven't any experience with them yet (waiting for mine to arrive). -A.