802.11a,b,g

**raul** · May 25th, 2004, 10:59 AM

waht is the difference between 802.11a, b,g???

**Archer** · May 25th, 2004, 11:02 AM

http://802.11abg.rtx.dk/

802.11b is currently the most widespread standard, and can transfer data wirelessly at a speed of 5.5 Mbit/s within a range of 50–100 metres.

802.11a is four times faster than 802.11b, providing a speed of 27 Mbit/s and a range of 20–100 metres.

802.11g is the latest standard and is just as fast as 802.11a, but operates on the 2.4 GHz frequency band.

**raul** · May 25th, 2004, 12:09 PM

which do i choose for long range and with obstruction ????

Originally Posted by Archer

http://802.11abg.rtx.dk/

**Archer** · May 25th, 2004, 12:14 PM

How long i.e. are we talking tens of meters or miles and what sort of obstruction i.e. metalised walls can cause problems?

**raul** · May 25th, 2004, 12:18 PM

5km and some power lines ....

Originally Posted by Archer

How long i.e. are we talking tens of meters or miles and what sort of obstruction i.e. metalised walls can cause problems?

**Gollo** · May 25th, 2004, 10:38 PM

I don't trust G yet. It's to new and if I'm not mistaken it is not an official standard yet (almost but not quite). I'd use A if you need bandwith and B if all's you want is to share internet or lite file sharing. Just make sure that when you buy antennas that they are for said standard as A is in the 5ghz range and B,G are in the 2.4ghz range. You will probably have fewer interference problems with A as well as the 2.4ghz range is saturated with other ap's, cordless phones and microwaves etc. Also keep in mind that you will need to keep your fresnal zone open as well as LOS (google the terms if you are not familiar with them). Good luck.

**TechZ** · May 26th, 2004, 02:33 AM

the usrobotics (or 3Com) 802.11g claims 100mbps in ideal situations and from what i've read it can almost reach that speed, at least better than the 54mbps other G models out there

**confus-ed** · May 26th, 2004, 05:43 AM

Originally Posted by raul

5km and some power lines ....

Well none of the above ! All those standards are about 'inside' really .. they've just bumped the figures on b & g class wireless ranges to reflect what you can achieve in ideal/good conditions

The problem over a distance of 5km is the potential interferance on public bands
802.11a operates on the licencefree 5 GHz frequency band, while the others use the 2.4 GHz band. So what you get is just like when you are listening to your favourite local radio show near the edge of its 'hot transmission' area, where you get the local pizza delivery or Taxi firm cutting in ..

At 5km you've got to start thinking satellite & the like & loads more money, unless you have a pair of very tall buildings & not too much in between, & I'd say some high voltage power lines in line of sight will produce some 'interesting' levels of interferance ..

**Stalemate** · May 26th, 2004, 10:31 AM

I'd like to add to what Cnfus-ed responded by sayint that if line of sight is available, then microwave solutions also exist.

The only problem you will have in reaching a 5Km target is quite simply cost.

We're talking a lot of money here, compared to the 802.11x solutions you were looking into.

It may be simpler just to setup a VPN or a dedicated line between the two points.

**TechZ** · May 27th, 2004, 07:41 AM

i read in teh paper, a guy just spent $5 on making his wifi connection go 5km,

**raul** · May 27th, 2004, 08:38 AM

now im confused...

as far i know... i would cost me more than $2000
to buy those smartbridges...that can go 5km

Originally Posted by TechZ

i read in teh paper, a guy just spent $5 on making his wifi connection go 5km,

**TechZ** · May 28th, 2004, 12:05 PM

4km WiFi Range w/ $5 DIY Antenna - This industrious fellow in New Zealand made his own WiFi antenna using a USB WiFi adapter and a Chinese 'spider skimmer mesh scoop.' He got about 17 dB signal improvement for about US $5 in materials.
http://www.stanford.edu/~jstockdl/tm....orcon.net.nz/

**confus-ed** · May 28th, 2004, 01:14 PM

Originally Posted by TechZ

[b]4km WiFi Range w/ $5 DIY Antenna

, but have to have a try though, high voltage cables are a hell of an interference zone in our line of sight, I can't get digital telly at my house because of some well over 500m away.. I reckon though those numbers are still 'ideal' conditions, then you've got waterproofing yada yada

..so in best military tradition we ran a few LOS(Line Of Sight) scouting trials,supporting the USB device on a broom handle tied to the roof,fed by ~5m of regular el cheapo USB cable from an XP laptop running the new NS 0.4 inside. As always LOS means just that at 2.4GHz, & assorted in line trees & buildings caused massive signal losses, so ~100m was all we managed while walking around the house/yard/street with a Dell Axim PDA & a Socket low power CF WiFi card.

The guys on that link are busy stealing other folks open wi-fi signals, so what they call 'connected' & what I call connected reliably will be two different things .. but you never know