On Wed, 6 Feb 2002, Matthew French wrote:
> Have no idea how this relates to trees, which are not particularily good
> conductors if the greying matter is to be believed.
have a search on the internet for fresnel zone.
the upshot is that between 2 nodes you need to have an elliptical
region of clear space between.
so though you might have line of sight to the other node, a building
or trees slightly to either side of the line of sight would impede
the width of the fresnel zone increases with distance between the
> Er, no, maximum available bandwidth is half the frequency.
> (Shannon's law?)
the likes of kenn humborg could quote shannons law with more
authority but /bitrate/ relates to available /bandwidth/. bandwidth
is the range of frequency used.
(from a book):
nyquist's theorem states that for a noiseless channel of bandwidth H
with V discrete levels:
maximum data rate = 2H . log2(V) bits/sec.
so for a noiseless binary channel:
max data rate = 2H . 1
so an x Hz channel has can carry a max of 2x bits/sec under perfect
Shannon adds the concept of signal to noise ratio:
max bits/sec = H . log2 (1 + s/n)
true for any channel subject to gaussian noise, irrespective of
> So you should be able to get gigabits per second at cell phone frequencies.
> The reason you don't is:
> - Bandwidth is shared/sliced between all phones.
and within the band of a channel, the bit rate might further be
divided amongst the phones by time division.
> Anyway, I hope this makes things clearer. If I were not riding an 802.11
> deficient train, I might be able to research the answer on google.
>> - Matthew
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