Re: What causes the 56kbps limit on dial-up internet connections?

In article <46e471b4$0$17077$4c368faf@xxxxxxxxxxxxxx>, Green Xenon
[Radium] says...
On Sep 9, 9:13 am, Jeff Liebermann <je...@xxxxxxxxxx> wrote
http://groups.google.com/group/sci.electronics.design/msg/0247b0487037bc81?hl=en&;
> Look at a communications channel this way. You can get *ANY* speed
> through a bandwidth limited channel, up to a given error rate. If
> your application requires a very low error rate to function, then you
> have to have a good signal to noise ratio, and your thruput will be
> fairly small. However, if you have a mess of forward error
> correction, small packets, and a very tolerant application, you migtht
> be able to squeeze some more thruput through the same channel.

So if I don't care about the errors, I can get whatever speed I want?
What about getting 1 Gbps on dial-up if I have a baud of
1-symbol-per-second but 1-billion-bits-per-symbol? Is that possible?

Sure, just don't expect them to be correct. And if you don't care about
errors why bother with the link at all? Just use random noise instead
and free up your phone line.

> 56Kbits/sec. The limit is NOT all from the analog part of the line.
> The analog modem glop gets converted to digital at the CO and that's
> limited to 56Kbits/sec. I could easily (well maybe not so easily) get
> more than 56Kbit/sec thruput going between my house and the CO, but
> the digital thruput at the switch will limit thruput to 56Kbits/sec.

Can this be changed so that the digital throughput will go up to
1Gbit/sec instead of just 56Kbits/sec?

There would be no point. It's meant to carry voice, conversations are
not going to significantly benefit from a significantly higher data
rate. If you simply want data you know where to get it. The current
most popular incarnation over phone lines is probably DSL.

Robert

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