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Since the summer
of 2002 I have been playing around with the idea of a cheap, private,
wireless, high bandwidth, point to point digital radio network and this web
page documents the progress made so far. |
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Why, I hear you ask? ...Well I have
been involved with different wired and wireless networks for quite a few
years and considered that there is a need for just this type of system out
there now. Having been one of the first engineers to be trained and to work
with xDSL Broadband back in 2000 when it was first trailed outside of London
I knew instantly there was going to be a big demand for very fast internet
connections to the home in the near future. The only problem I could see
would be how to make the same systems commercially viable in the sticks, away
from high population areas. Over the next couple of years BT and Cable Co’s
steadily rolled out their Broadband networks and for a while in 2002 rollout
seamed to stop. It looked like I would be in an area considered to be
commercially unviable, which is a bit annoying to say the least when every
day you work with high speed internet access and go home to a ISDN dial up. I
needed to find away to get a fast internet connection (broadband) into my
area as at that point it looked like it would be a very long time before BT
would roll it out in my area. |
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802.11b had passed me by; I didn’t
know anything about it until a customer one day showed me his access point
and PCMCIA cards. I could see it wouldn’t be ideal but as it was fast becoming
a mass market product and getting cheaper by the week I looked into what
could be done with this wireless system. I stumbled across the Consume
project in London, and a more local but inactive group in Brighton. Yes I
know there are better, more suitable systems but every on else is playing the
802.11b game so it made sense to join in, after all I wasn’t going to get
very far on my own. It wasn’t until two of the Brighton Consume node sysop's
got in touch that things started to take off, and as luck would have it we
all had line of sight to each other. Admittedly at that point I didn’t know
just how much I would need to spend on the project or how much time would be
needed just to get it up and running. |
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In summary, It works and I have
learnt a lot about just how far you can push this “off the shelf” kit and how
far you can make it work. Never under estimate the cost of a project like
this, it was never going to be cheaper that wired broadband, but sponsorship
and free advertising has helped keep costs down. Luckily the DDWLAN Node2 is
a local high point with fantastic views over Sussex. Installing two live web
cams and a weather station at the node has given a lot of extra interest to
the project. The site is used by all sorts of people from hang gliders to
hill walkers and pub go-ers. These extra items have allowed people to gauge
the activity and weather on the site before setting out for the day and maybe
what keeps the project going once wired broadband has been fully rolled out
in the area. The knowledge I/we have gained over the last year has been vast
and something no book could have ever got close to....And I will always be
able to boast, that I was the very first to have broadband internet access in
my village, six months before it became available on the local exchange. |
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The big white grid antenna shown in
the photo's is one of two purchased from www.hyperlinktech.com which offer a range of sizes
and Db gain. I went for the biggest one with 24 Db of gain over a
standard dipole. Sunday 14/09/2002: Above are some
photo's taken while out and about doing some WiFi 802.11b point to point
tests from Truleigh Hill. So far the max distance I have tried is 10.1Km from
Truleigh Hill to the wireless ISP Node on the Sussex Heights building on
Brighton seafront, (Note: This has now been removed March 2003). This was a
good test, with a 4meg file transferred in 21 seconds. Signal levels: not
very accurate but 4 out of 5 bars on the Orinoco icon, which is what I get
floor to floor at home from the onboard Antenna.
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Sunday 6/10/2002: I have been working
on finishing off the housing for the Linksys WAP11 v2.2 and getting it ready
for point to point testing. Once I am happy that the AP and antenna are
working okay, I will be putting this kit up on the roof so that it has a line
of sight to Devil's Dyke. I will be able to test the kit (all being well) at
10, 14 and 15km without having to return to move the antenna on the roof,
(Planned for April 2003). The current housing is only a very large sandwich
box, and I don't intend to leave this on the roof longer than a few days. I
have tested it outside for two weeks in the heat and rain and I'm happy that
it will work for the time being. If this kit ends up staying on the roof I
think I will put the AP in the loft for maintaince and weather reasons.
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Sunday 16/03/2003: Winter has gone
and it's time to get the Waif kit out again. Over the last few weeks I have
been in contact with the sysop's Tim (Anyone for Cricket) and Simon (Devils
Dyke) of the Brighton Consume network. Today as the weather was good we went
for it and had a go to see if it would be possible to link the two sites via
WiFi. As it was all very last minute, Tim quickly put his kit together on the
roof at Hove, and Simon and I setup my antenna on the Dyke Hotel roof. The
link is about 6.7km long and only just about line of sight. Ground Affect -
the path of this link could be affected by the ground between as it is very
close, but Yes, we linked up! The signal to noise was around -78dB at best.
Some work will be needed at both end to improve this, but Simon is over the
moon, as this could be the answer to his broadband blues... This work has now
continued into April and is becoming a project in is own right "The
Devil's Dyke Wireless LAN Project". Tests have been carried out at 15.5km
and 13.6km, with very good results when the links are LOS (line of sight).
All the current test have been done with temporary kit put in place just for
a one off test. We are now however in the process of sourcing the correct kit
which includes antennas, Heliax, and Access points to put the longer and more
marginal links under a constant test. Marginal and Long is just what the link
from the Dyke to Washington is going to be. If that will work in bad weather
as well as good then anything is possible...
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Right/Top: Washington to Dyke, and Right/Bottom:
Dyke to Hove "Point to Point" land profiles. These show that there
should be "Line of Sight" between the required locations. Even the
best and most up to date mapping software won't tell you is if there are high
rise buildings or tall trees in the way. Instead of writing war and piece on
this subject myself Solwise.co.uk have a very good page on their web site. so
if you need to know more about Line of Sight, and such matters visit the link
directly below which goes into all the detail you should ever need. Below
also is a animation (done by my son Leigh) which goes some way to explaining
LOS and how it is used in the Devil's Dyke Wireless LAN Project. |
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The first antennas go up. Above One:
"DDWLAN Node2" New antenna &: Two: as it was until July03. The
antenna was installed on a chimney in the middle of the building, only
afterwards did we find out that this was going to be a problem for end user
sites directly North of the Node in Fulking and Poynings. In the end we had
to cut our losses and shift the whole antenna system and Node forward 6
meters. Although a Comet Omni-directional antenna has been used at DDWLAN
Node2, I choose to pay a bit extra and get the -3 degrees down tilt model as
the node was so much higher than anything else likely to connect to it. Using
a Omni-directional antenna is way cheaper than using a sectoristed antenna
which could always be used at a later date. Above Three & Four
:"DDWLAN Node3" at Washington. Only a directional antenna has been
installed at the Washington DDWLAN Node as there are no plans to rebroadcast
the signal from this node at this time. The node will only be used for
testing and admin tasks. It could also be used as a backup back haul
connection if DDWLAN Node1 failed. |
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Above Left: Devil's Dyke -
"DDWLAN Node2", as seen from Washington - "DDWLAN Node3"
a distance of 14.2Km. Above Right: Washington - "DDWLAN Node3" as
seen from Devil's Dyke - "DDWLAN Node2". Well I think the pictures say it
all.. The human eye is no good for spotting a object 14Km away. The way we
first proved the links between Hove, Devil's Dyke and Washington was to use
High power lamps at night. Stand where you are going to place the antenna (or
as close as possible), one person at each end of the link. Shine a torch or
lamp towards the other end and the person there should see it. You will need
mobile phones or 2way radios for this as well. A 500,000+ candle power torch
can be picked up from your local D.I.Y. store for about £20 (you only need
one), just move it from one end of your link to the other to try in reverse.
Point to note here is spotting one single light in a town the size of Hove at
night is not easy unless you know where you are looking. It is better to have
the torch at the rural end first, as the person in the town will be looking
out into a near black horizon. You may even find the remote end isn't quite
where you thought is was.. |
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....Anyone
got a chainsaw ?.... As I was saying, not quite where I thought is was, so
this proved useful as moving the mast to one side improved the signal, when
we got around to installing the kit at the Hove Node. Looking at the red
ring, clearly shows a potential problem. No leaves on the tree now, but come
summer and a lot of head scratching later would have someone looking for the
local tool hire shop (joke). Just as easily the link could have been blocked
by the block of flats in the picture. If it had we would of been knocking on
their door asking about the possibility of using the roof.. Trade you some
bandwidth sir ? |
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Left: Aiming the Washington antenna
with the aid of a small pole mounted camera. It's not a simple task to point
a antenna in the correct direction when it's 4 meters above you and there are
trees in your way. Placing a "pair of eyes" where the antenna is makes
all the difference. Right: First time connection between
DDWLAN Node2 and Node3. The remote test router's admin web page as seen over
the Washington to Devil's Dyke wireless 802.11b link. The other inlay window
is the PCMCIA card's admin software which shows the signal strength and
quality of the link. Long term testing has shown the best setting for this
link to be 5.5Mbps, which gives a useful transfer rate of 3.5Mbps with error
correction. This is due only to the fact that this kit was never designed to
work over this distance and there is a lot of frame timing issues and packet
losses at 14.2Km, still much faster than current fixed broadband offerings
from the major telco's. |
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Above
Left: The "rig" used to test our first point to point link between
"DDWLAN Node2" and "DDWLAN Node1" in Hove. Above Center:
The remote site in Hove that this "rig" was pointing at. The main
idea of this was that it could be left in place for a longer period of time
and the radio kit is located in the weather proof housing at the rear of the
antenna. In practice however even with two sandbags, the high winds at
the time of testing kept blowing the antenna over. Big pain as this meant
that I had to stay with the antenna while someone else sat in the warm with a
laptop to monitor the connection (surf the web more like :). Above Right:
This is my portable test antenna which can be easily transported to end user
addresses for line of sight path testing. It consists of a 6 meters sectional
pole and 15dBi gain directional antenna. This is a more suitable antenna for
end user sites as most wouldn't want or need the bigger 24dBi antenna shown
towards the top of this web page. LRM400 coaxial cable was used for the down
lead. |
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Above:
Four examples of end user antennas |
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·
©2004.
Service specification subject to change at any time without notice. E&OE.
All service usage is subject to the standard service terms.
Trademarks are acknowledged of their respective owners.
