[Hidden-tech] Security and coverage for shared WiFi

[ussailis at shaysnet.com]

Here's a few more tricks that impact WiFi coverage.

I mentioned transmit power, now lets look at the other side of the coin.
All WiFi units are radio transmitters and receivers. The receiver "system"
is often more important than the transmitter in achieving range.

All radio receivers receive signal (hopefully) and noise. The important
part is the signal-to-noise ratio, S/N. From the processing standpoint
there are acceptable minimums for a S/N which depend on the type of
transmission.

Many "types" exist, common ones are AM and FM. FM offers immunity to noise
bursts (lightning) and operates down to a low S/N. On the minus side is
hopelessly fails below a certain minimum S/N.

AM is still useful at low values of S/N, but receives every lightning crash
for many miles around.

WiFi uses a mix of signal "types." The mix changes for every increase in
"bandwidth," so a higher S/N is required for each greater bandwidth. This
reduction in S/N can be more than any change of transmit power on the other
end.

---
The WiFi band is wide in the US, 2400 to almost 2490 MHz in the US.
Originally many WiFi channels were allotted to this space, which worked
fine until version 802.11G came by. This version uses 22 MHz / channel,
limiting the number available to 4.

The upshot is there are fewer channels, each requiring a higher S/N to
properly work.

Trick 1.

Use a lower bandwidth. Here I have 3 Mb DSL. 11 MHz bandwidth makes no
sense, as all I so is email & look up stuff on the web. A lower bandwidth
lowers the S/N requirement.

Trick 2.

Neighbors are a problem. They also have WiFi. But they might not be on one
particular channel, and your access point might be able to select a
specific channel. Select the less used one.

Trick 3.

There is another WiFi band. It is designed for campus systems. It operates
in the 5 GHz region, goes by 802.11A. You will read in places that it is
old. Hardly, but there have been some advances lately. 

This looks good as most of your neighbors use the lower frequency band.

Caveat: I haven't tried 802.11A yet, but will soon. In the meantime I have
gone to plain old ethernet. Yes a pain to string a wire about, as I have
right now. On the plus side, no competition from other WiFi systems. Much
faster!


Jim Ussailis



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