RE: [RPRWG] How much jitter can voice circuits tolerate?
This may be stating the obvious, but it's important to recognize that
the access delay (such as might occur in 802.17 access rings) is only
one component of the end-to-end delay budget. There is coding delay,
propagation delay across the end-to-end path, playout buffer delay
(often equal to the worst case jitter), etc. It is important to keep
the portion of the delay budet consumed by the access network as small
as possible. I don't remember exact figures but less than 5 ms would be
nice; 10 ms would probably be viewed as excessive.
chuck
-----Original Message-----
From: John Lemon [mailto:JLemon@xxxxxxxxxxxx]
Sent: Tuesday, April 15, 2003 5:56 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