Re: Talking with Yahoo Messenger
Mark Allums wries:
> In the US, a 56k dialup running at 53k (max allowed by law, and rarely
> achieved in practice) gives you just about the necessary bandwidth for
> voice over IP, *and nothing else*.
That's 56k downbound. Upbound is 33k max.
> Not a voice-over-IP expert, and yes, I *have* heard of Nyquist.
Good. Now read Shannon. The number of bits per second you can push
through a channel depends on the bandwidth _and_ the signal to noise
ratio.
> What modulation does Skype use? Some type of delta modulation would be
> my guess for dialup, but I have no real idea.
None. Skype surely uses some sort of compression, but the modem handles
the physical layer using complex multitone modulation schemes.
--
John Hasler
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