I used some early 802.11 style kit (WaveLAN) in 1992 in a university in
the UK to connect some outlying campus buildings without having to
dig-up-the-road etc.. I suspect that the technology has come a long
way since then... Anyway, at that time these devices could give 2Mbps
links, which was excellent for the price of the cards. So if they're now
$200, faster and have more robust connections...
Field experience showed that the following things upset the connection:
- Double-decker buses interrupting the signal (the system didn't
always recover from this, needing rebooting)
- Snow, hail (not likely to be a problem in Africa). I don't know if
heavy rain might be an issue.
- Trees, when windy and near the line-of-sight (perhaps that's
this Fresnel point issue that George S mentions)
The standard range was 100m - in fact, 100m was pushing it; 80m
was more realistic - the system could go through walls if
you went for much shorter distances, but campus style connections
were really what we wanted. I did discover that there were ways of
increasing the range: Using a directional antenna, instead of the
standard omnidirectional antennae, and increasing the signal power
(I never tried this, but do I understand radio correctly if I suggest that
making your antenna bigger is enough to effectively do this?).
Where you put your antenna had some effect too - where possible,
we liked to put antennae inside a window, but the glass would weaken
the signal slightly, so certainly for one building we chose an external
Anyway, a good technology for some very specific applications. I did
also research around the subject at the time, to discover that this isn't
the only radio technology out there - there are others that work over
*very* long distances, but their speeds are really low (comparable to
old modems, so rates in the Kbps, not Mbps ranges). The latter does
get used for collecting data from e.g. remote weather monitoring
stations, where bandwidth isn't the issue.
And to complete the thoughts in this direction, DAB - digital radio
broadcasting - is now making an appearance in the UK. Apparently
at the same time as broadcasting a radio programme, data can
be broadcast too. I don't know whether there are any plans to
introduce DAB anywhere in Africa yet, but this technology may be
one to watch in the future.
From: George Sadowsky[SMTP:[log in to unmask]]
Sent: 01 February 2001 17:00
To: [log in to unmask]
Subject: Re: Public 802.11 networks?
This is a set of comments on 802.11, not 802.11b, just in the event
that it might be helpful.
802.11 is a pretty well established technology in the United States.
It's an extension of the broadband technology, so that security is a
At New York University, where I used to work, we worked with Lucent
on their PubLan (Public LAN) offering to identify and close security
holes, of which there are many in the basic product. More recently,
AeroNet (Cisco has come up with another approach, using among other
things, VPN technology with a central encrypted authorization process
that seems to solve these problems really well.
We also used 802.11 in a historic building where the costs of wiring
would have been prohibitive because of city regulations applying to
If you're not worried about security all that much, then 802.11 is a
really good alternative for AFrica. Last April Eric Stevance and I
spent several weeks in Madagascar working on a plan to network five
universities. Our recommended solution uses 802.11 extensively for
almost all local loop connectivity between city POPs and campus
locations. You do need line of sight, and you need a little more
around the halfway point to accommodate a Fresnel zone (if you're a
physicist, you understand this).
The technology is being implemented in point to point and point to
multipoint flavors. Initial speeds in the U.S. were 2 mbps but you
can get cards now for less than US $200 that give you 11 (eleven)
mbps. Access points (the wired transponders) that provide the link
to the wired Internet generally consist of a couple of those swame
cards with some additional electronics, and cost less than $1,000.
Range of 802.11 is, in our experience up to 10 km, more or less. I
can't speak about what happens if you jack up the power.
At 5:08 PM +0100 2/1/01, Eric S Johnson wrote:
> > From: African Network of IT Experts and Professionals (ANITEP) List
>by the way, does ANITEP have any incarnation in any way other than this
> > Forgive me if this issue has come up in the past (I must have missed
> > it) but has anyone been thinking about 802.11b technologies in the
> > context of wireless networking / public Internet access?
>i've heard lots of tidbits about 802.11b. it's my understanding, in the US,
>that's considered to be short-range. but in our moscow office the other day
>i saw a demo of a unit that was longer-range--they'd cranked up the power.
>not sure what frequency management regulations were being broken. but they
>got 1mbps working just fine. they are using their system to provide internet
>service in nizhnii novgorod, in russia--they use what you'd normally think
>of as 802.11b clients as their base stations and then run an ethernet cable
>to their 5 or 10 subscribers in that building (can we say security risk?).
>so they've set up a bunch of these base stations around town and the bases
>communicate with their central node via 802.11b. that way the cost of
>connecting a new subscriber, provided the subscriber's near an existing
>base, is very minimal.
>they said when they crank up the power, they would get about 40 km via