Wireless (802.11) website?

[Matthew Carpenter]

You wanna write a book about it?  I'm learning new stuff, and there's
experience in your words which speaks volumes.

On Tue, 9 Jul 2002 08:52:57 -0500
"David A. Bandel" <david at pananix.com> wrote:

> On Tue, 9 Jul 2002 08:54:57 -0400 (EDT)
> begin  Net Llama! <netllama at linux-sxs.org> spewed forth:
> 
> > On Mon, 8 Jul 2002, David A. Bandel wrote:
> > > On Mon, 08 Jul 2002 20:12:14 -0700
> > > begin  "Net Llama!" <netllama at linux-sxs.org> spewed forth:
> > >
> > > > i guess i'm showing my ignorance.  so a base-station/access-point
> > > > is basically an embedded device that doesn't need an OS based
> > > > driver to work?
> > > >
> > > > i guess i need "wireless for dumbies", cause i don't fully
> > > > understand how it all comes together.
> > > >
> > >
> > > commercial "access points" cannot be used as anything but that, they
> > > can't be used as Master or Repeater stations.  It has to do with
> > > proprietary code in the cards, and the big boys don't want anyone to
> > > muck with their gravy trains.
> > >
> > > In a linux box, however, a wireless card in ad-hoc mode is basically
> > > an ethernet card.  You do need to understand radio signals and how
> > > they work, fresnell zones, and more, but that's not hard either.
> > >
> > > Tell me what you need, I'll give you more than you've ever wanted to
> > > know.
> > 
> > OK, what i attempted to diagram in my previous email was, that i'm
> > getting DSL activated this Friday at home.  My grand plan (excluding
> > the WiFi
> > stuff) is to run a Freesco box box that has 2 NICs, one plugged
> > directly into the DSL router that the DSL provider gives me, and then
> > the other plugged into a 10 port hub (yes, i know switches are better,
> > but this is all i have on hand, and all i can afford right now).  I've
> > got 2 linux boxes that my wife & I use, plus 2 laptops (also linux). 
> > everything is a static (10.x.x.x) IP, and will have the Freesco box as
> > its gateway to the internet.
> > 
> > Now my vision for wireless is to get 1 or 2 wireless cards for the
> > laptops, and a base-station/access-point.  Plug the access-point into
> > the hub, point it to the Freesco box as the gateway (as i'm already
> > doing), and then get the laptops online anywhere in my house.
> > 
> > So, is this possible, or am i completely misunderstanding what
> > wireless can do for me?
> 
> My suggestion for you is the following:
> forget the access point, it's an unnecessary expense.
> In one system that's always on (I suppose, but don't know, that it could
> be the freesco box), put a PCI-PCMCIA bridge card (I recommend one with
> the Ricoh chipset) and a wireless card.  Spend the money you saved on
> the access point to buy something like the Orinoco Extender antenna
> (works with Orinoco/Agere cards, whatever card you use you'll need a
> compatible connector for the card).  Place the extender antenna at
> approx eye-level(when you're standing).
> Install WIFI cards in your laptops. Depending on your distance from the
> desktop, and the geography of your house, you may need small antennas
> for the laptops. The WIFI network will, of course, be a different
> network than your desktops, so make sure your routing is correct if you
> need to talk to your desktops.
> 
> On WIFI cards, antennas, and wireless:
> Most current WIFI cards are 50mW in power with no antenna.  An antenna
> effectively increases the power for both sending and receiving. 
> Outdoors, you can easily go 1/2 mile without antennas.  Newer cars w/
> 100mW and even 200mW can go to almost a mile.  An antenna extends the
> sensitivity and range.
> Wireless is LOS (line of site).  It will pass through glass, but not
> solid objects.  It will work in your house because for the most part
> you'll be inside the "ground plane" (fresnell zone).  An antenna,
> particularly one place up high, increases the ground plane (which size
> is based on antenna height and output power).  So while the signal can't
> see through walls, it can travel around them if the walls are within the
> ground plane.  With overlapping ground planes, you'll always have
> connectivity despite the LOS limitations.
> 
> On amplifiers:
> Some folks (often HAM operators) think amps will increase distance
> through increased power.  While this is true, you run the risk of
> overmodulating stations closer in.  WIFI works on SNR (signal to noise
> ratio).  Amps boost both, signal and noise.  They do little to change
> the SNR very much.
>  Imagine you get 50 e-mails a day, 10 of which are important.  Your SNR
>  is
> -.20.  This is good (actual WIFI calcs are much more complicated, with
> 93/93 being perfect). You can effectively process 100 e-mails per day,
> but no more (limitation on your time).  Suddenly, you find yourself
> getting 500 messages per day, of which 100 are important.  While the SNR
> is the same, you'll probably never see any of the 100 important messages
> because you're drowning in the 400 spams. Same principal applies to
> amp'd signals.
> 
> What haven't I covered?  Lots.  How antennas (typically 3dbi to 24dbi)
> boost effective power (power is measured at the antenna).  Signal
> polarity(must say a word or two here).
> 
> Signal polarity:  If you use something like the Orinoco range extender
> antennas, you'll see that they are similar to an omni.  That is, they
> have a radiation pattern, 360 degrees around, but probably vertically
> about 22 degrees (except within the ground plane).  However, you'll find
> that if you have two spaced out beyond the ground plane and you rotate
> one, even though they are "pointed" at each other (signal-wise,
> meanining they are perpendicular one to the other physically), the
> signal will decay and perhaps even disappear.  
> Note: You can effectively do "df" on a signal in the distance by
> reorienting the antennas to find the lull, do this from different
> places, and you can triangulate lines of bearing to get a df (direction
> finding) on the remote site.
> 
> The above is probably more than you wanted to know, but should give you
> good background to get you started.
> 
> Ciao,
> 
> David A. Bandel
> -- 
> Focus on the dream, not the competition.
> 		-- Nemesis Racing Team motto
> _______________________________________________
> Linux-users mailing list -
> http://linux-sxs.org/mailman/listinfo/linux-users
> Subscribe/Unsubscribe info, Archives,and Digests are located at the
> above URL.