[Kamailio-Users] Possible timing/latency related problem ?

[Alex Balashov]

P.S.

Outside of localised, low-activity LAN segments at close proximity, 
running VoIP over 802.11b/g/n-style wireless is generally considered a 
bad idea among serious network engineers.

It's a topic of fierce debate, though, since there are some narrowly 
conceived business models out there that hinge on VoIP framed over small 
802.11g wireless sectors and point-to-point 802.11 backhauls and stuff 
like that.  On the other hand, VoIP over WiMax networks like CLEAR in 
the US has generally received positive appraisals.

On 04/06/2010 08:23 PM, Alex Balashov wrote:

> Latency is not in itself an impediment to a successful VoIP
> conversation;  latency is just uncustomary for humans, and causes them
> to talk over each other not unlike satellite or microwave long-distance
> telephone conversations between hemispheres.
>
> The problem that is often present in connection with the underlying
> causes of high latency but is a different phenomenon than latency is
> jitter. Jitter is the presence of nonlinear temporal deltas between the
> arrival of RTP packets. RTP arrival at non-constant intervals causes
> audio distortion, "drop-outs," static, repetition, and stream
> synchronisation problems.
>
> The bottom line: if there is high but very constant latency, you can
> still have a manageable conversation. However, the same things that
> cause high latency -- for example, link congestion -- often cause
> jitter. The degree of packet queue saturation and/or bandwidth
> exhaustion often varies across time and creates stochastic,
> indeterminate effects that jitter buffers cannot be designed around, and
> certainly not perfectly at any rate.
>
> I would bet that jitter is the cause of your problem, simply because it
> often goes hand-in-hand with latency.
>


-- 
Alex Balashov - Principal
Evariste Systems LLC
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