[Help] Echo on VoIP/SIP Channel


#1

I recently changed my Broadvoice server to a “closer” one. My connections are much more stable now, but now I am getting echo on my end … which I didn’t think should happen in this configuration …

VoIP Phone ---- Asterisk ------- Broadvoice -------- PSTN ------- Caller

The VoIP phone is a cheap Grandstream, but I wasn’t getting echo before so I am relunctant to blame it.


#2

Try comparing some ping times between the two Broadvoice servers. See which one has better latency.

Also try running a traceroute, see how many hops are between you and the each server.

My guess it that it is a network issue.

Dan


#3

I am getting local echo - as in I can hear myself slightly out of sync. The other end does not hear it at all.
Any ideas? I have echocancel=yes, echotraining=800. The echo is a few ms off from the speech, and only happens when I call Phone to * to Voip Provider to PSTN, not on Phone to * to PSTN.


#4

i wonder if the new server you’re connecting to is having echo issues…in other words, the original box you were connecting to wsa set up properly, but this new one isn’t. you might contact broadvoice to see if they have set the tx and rx levels properly and set echo cancellation and echo training to enabled.

that’s the only thing that makes sense to me, anyways, but i’m hardly an expert.


#5

To dmikuser … I did extensive testing of the latency and variation for both the signalling (SIP) gateway as well as the media (RTP) gateway before changing. This is why I changed.

I am re-thinking my reluctance to blame the phone … I made another call using an analog phone through an ATA and it was just fine … hmm.


#6

I concur with whoiswes.

Since I can’t describe it any better, here’s a quote from chapter 8 of Asterisk: The future of Telephony.

[quote]Why Echo Occurs
Before we discuss measures to deal with echo, let’s first take a look at why echo occurs in the analog world. If you hear echo, it’s not your phone that’s causing the problem; it’s the far end of the circuit. Conversely, echo heard on the far end is being generated at your end. Echo is caused by the fact that an analog local loop circuit has to transmit and receive on the same pair of wires. If this circuit is not electrically balanced, or if a low-quality telephone is connected to the end of the circuit, signals it receives can be reflected back, becoming part of the return transmission. When this reflected circuit gets back to you, you will hear the words you spoke just moments before. The human ear will perceive an echo after a delay of roughly 40 milliseconds. In a cheap telephone, it is possible for echo to be generated in the body of the handset.

This is why some cheap IP phones can cause echo even when the entire end-to end connection does not contain an analog circuit.† In the VoIP world, echo is usually introduced either by an analog circuit somewhere in the connection, or by a cheap end point reflecting back some of the signal (e.g., feedback through a hands free or poorly designed handset). A good rule of thumb is to keep latency to less than 250 milliseconds.[/quote]