[MLB-WIRELESS] Whats Faster ??

[Ben Anderson]

----- Original Message ----- 
From: "Stygen" <stygen at wafreenet.org>
To: <melbwireless at wireless.org.au>
Sent: Tuesday, August 12, 2003 5:30 PM
Subject: Re: [MLB-WIRELESS] Whats Faster ??


> On Tue, 2003-08-12 at 14:24, Matt Pearce wrote:
> > Hi All,
> >
> > I am wondering what is faster for transfering data. ie. Out of
> Wireless
> > (2.4Ghz), Copper (Cat5e etc) and Fibre Optic, which signal travels the
> > fastest from point A to point B ??
> >
> > Matt.
> >
>
> There is two different questions here.
>
> A) What is faster for transferring data?
>
> Both Fiber Optic and Copper wired networks can be 10, 100, or 1000 Mbps
> depending on your hardware. 802.11b runs at 11Mbps half duplex (little
> bit less).  So the cat-5 and fiber optic transfer speed is much faster
> than 2.4GHz networking using currently available hardware.
>
> B) Speed through medium.
>
> It wouldn't surprise you to hear that Fiber Optic data travels at the
> speed of light in plastic (for the sake of argument there is very little
> difference between the speed in air).  2.4GHz also travels at the speed
> of light.  The best way to explain this is to compare it to UV light.
> You understand that UV light travels from the sun at the speed of
> light.. well the waves used by 2.4GHz gear travels at comparable speeds,
> it is the same form of energy, but with a wavelength about a million
> times larger.
>
> Cat5 carries a maximum of 100MHz signal through copper. I could be well
> wrong here, but my assumption is that the signal is carried through the
> copper as per current, which involves electrons.  Since it is being
> transmitted via matter rather than through it, my assumption is that the
> speed would be more like the speed of sound.  Correct me if
> wrong..anyone.
>
> In any case, the latency order from fastest to slowest would probably
> be;
>
> 1) 2.4GHz
> 2) Fiber Optic
> 3) CAT5
>
> If it were a perfect world with congestion and assuming the distance to
> be traversed was identical.
>
> -Stygen


Actually, in real world terms, 2.4ghz has to go through a block
encode/decode process before it goes 'onto the wire' - it is significantly
more complicated, and therefore time consuming than the modulation used over
fibre or copper.

I'd expect bandwidth to be something like:
10Gbits (singlemode) fibre
1Gbit (multimode) fibre
1Gbit cat5
50Mbits 2.4ghz (given lab conditions, this is achievable)

In terms of latency:
Fibre:  5u sec /km is a reasonable ballpark
cat5:  25 - 50usec/100m  (highly dependant on actual network card, some can
push this up to 500usec!)
wireless:  typically in the milliseconds - huge amount of variation due to
uncontrolled prevailing conditions.  Lab conditions would probably bring
this to a reasonable number, but in reality there's still quite large
modulation overhead which is going to keep this well on the bottom of the
list.

Hopefully that answers the question of "faster for transferring" and "signal
travels fastest" origianlly asked :)

Regards,
Ben.



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