RE: [RPRWG] How much jitter can voice circuits tolerate?
Post de-regulation established that the responsibility of
echo cancellation fell on a carrier if they exceeded 6.5 msec
for round trip delay. Remember echo cancellation is required
because at some point a single-pair twisted wire carrying full-duplex
telephone call is connected into a two-pairs of twisted wire, full duplex
network called the hybrid.
This was derived on the back of envelope by dividing 21 msec
amongst 3 entities: the call originating ILEC, the long haul carrier
and the call terminating ILEC.
The funning thing is the IXC were penalized by this since the carried
voice over greater distances. As a result if used cheap long distance carriers
during peak periods they would run out of echo cancellers since these
specific and limited resources available on an add-on card
raj
> -----Original Message-----
> From: John Lemon
> Sent: Tuesday, April 15, 2003 2:56 PM
> To: Mike Takefman; 802.17
> Subject: RE: [RPRWG] How much jitter can voice circuits tolerate?
>
>
>
> I recall 28 ms being the magic number at which echo can first
> be detected. Therefore I imagine that echo cancellation is
> turned on for any path that exceeds 28 ms regularly or 30-35
> ms with less frequency.
>
> If anyone really cares, ITU-T G.164, G.165, and G.168
> recommendations cover echo cancellation in excruciating detail.
>
> -----Original Message-----
> From: Mike Takefman [mailto:tak@xxxxxxxxx]
> Sent: Tuesday, April 15, 2003 12:30 PM
> To: 802.17
> Subject: Re: [RPRWG] How much jitter can voice circuits tolerate?
>
>
>
> Bob,
>
> from the user's perspective delay and not jitter is
> the major quality factor. Delay above a certain
> point required echo cancellers or the echo can
> be very disconcerting.
>
> In TDME systems (like ATM for example), the device
> converting packets or cells back into voice has a
> de-jitter buffer to account for delay variation
> in the network. The level of jitter is generally
> much lower than the average delay that the packet
> sees due to propogation. In any case, the worst
> case jitter drives the size of the de-jitter buffer
> and adds a fixed delay to the voice signal in
> addition to the propogation delay.
>
> I will try to find out some from of my old voice
> buddies at what delay the echo-cancellers become
> mandatory. Note: such cancellers are in all
> of the networks anyway due to voice trunk delays
> for longer distance conversations.
>
> mike
>
> > "Robert D. Love" wrote:
> >
> > One of the 802.17 objectives is the propagation of voice
> traffic. Are there
> > any hard requirements or guidelines as to how much jitter
> can be tolerated by
> > the voice traffic without degrading the conversations?
> >
> > Any insights you can provide for this question would be appreciated.
> >
> > Thank you.
> >
> > Best regards,
> >
> > Robert D. Love
> > President, LAN Connect Consultants
> > 7105 Leveret Circle Raleigh, NC 27615
> > Phone: 919 848-6773 Mobile: 919 810-7816
> > email: rdlove@xxxxxxxx Fax: 208 978-1187
>
> --
> Michael Takefman tak@xxxxxxxxx
> Manager of Engineering, Cisco Systems
> Chair IEEE 802.17 Stds WG
> 2000 Innovation Dr, Ottawa, Canada, K2K 3E8
> voice: 613-254-3399 cell:613-220-6991
>