[MLB-WIRELESS] Whats Faster ??

[Donovan Baarda]

On Tue, 2003-08-12 at 16:49, Steve Smithies wrote:
> MP> I am wondering what is faster for transfering data. ie. Out of Wireless
> MP> (2.4Ghz), Copper (Cat5e etc) and Fibre Optic, which signal travels the
> MP> fastest from point A to point B ??
[...]

The reason radio waves travel at the speed of light is; it is light.

> As a side note, the actual flow of electrons in copper is much much
> slower. I've gone and forgotten the formula, but remember at high
> school calculating that for something carrying like 2 amps through
> 2mm wire, the electrons were only moving about 6cm/second.

The reason electrical signals "travel" through wire at nearly the speed
of light is the electron's don't move that fast, the "voltage
difference" does. With a hose full of water, when you turn on the tap,
water starts coming out the other end almost immediately, you don't have
to wait for the water leaving the tap to arrive at the nozzle before
water starts coming out.

With data signals, the speed of transmission only affects latency. It is
the "speed of transition" that affects data rates. How fast can you
change the signal, not how long does it take to get there. Of course you
need to be able to detect the change in signal at the other end too.

Most of the limitations in data rates are caused by "mooshing" of the
signal transitions. In wireless this comes in the form of multi-path
affects, reflections, and background noise. In copper it is mainly
capacitance, inductance, reflections, and "crosstalk" interference. In
fiber it is mostly multi-path affects.

These all mean that there is a limit to how fast you can transition your
signal before the transitions start to get lost at the receiving.

-- 
Donovan Baarda <abo at minkirri.apana.org.au>


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