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Spelling: NodeFOX
Myself:
I am a student at LaTrobe [1] Uni studying a Computer Systems
Engineering degree in my final year. I've been a programmer since I
was wee little tot, back in the old Sinclair Spectrum [2] days when an
upgrade from 16kb to 48kb rocked!
I spend most of my time doodling in Delphi, making PIC micro
controllers smoke, researching this and that on the net and otherwise
feeding my brain with large amounts of technical nitty gritty. I enjoy
hacking stuff apart, forcing stuff to do what its told (not what its
design for) and I usually build instead of buying (even though it
usually cost twice as much in the long run).
The Plan:
I have broken my plan down into several stages, and hope to progress
rapidly (don’t we all).
_Stage 1 - Testing The Water_
A WLAN card, ex-galaxy modified antenna, a Pigtail [3], some
CoaxialCable [4] hooked up in an attempt to connect to anyone/thing in
my area. The oooh wow factor should be enough to keep me interested in
stage 2.
_Stage 2 - Hey, Look At Me_
Using my WLAN with an (homebrew) omni directional antenna to allow
anyone in the area to link up with me as share data about. Ohh look a
network... This should be 24/7 until I hit Stage 3.
_Stage 3 - Keeping The Dream Alive_
Combing previous two stages to create something useful towards the
whole Melbourne wireless scene. An omni to allow ClientNodes [5] to
connect to me, a directional connecting to another Stage3 nodes and
some routing to allow my client cloud to connect to another client
cloud.
This will turn my stage 1 developments into upstream links, I hope to
have two upstream links connecting to different distant nodes at a
similar stage of development.
I have been looking into antenna splitters which would allow one WLAN
card to use two directional antennas to connect to two separate nodes.
There are several issues to this however, such as the problems that
occur with phasing and front-to-back ratios etc.
There is also the issue of noise, if everyone did this then the noise
floor would increase due to the fact that a packet intended for an
individual upstream node gets sent to both nodes anyway.
_Stage 4 - On The Move_
A mobile node in my car. This should be simple enough, I already have
a PC system in my car that I use for MP3 playback but it uses a
character LCD and a hacked keyboard as the faceplate, so running
windows apps is out of the question at the moment.
I picked up a Unisys CWD [6] book style PC system from a swap meet
for around $50. This beast is small and compact, runs a P133, has room
for 1 HDD and 1 expansion slot (PCI/ISA) it even had 10BaseT network
so I just had to part with my cash. The power supply has now died, so
I need to crack out the soldering iron.
This was the basis of my Car MP3 Player, but I think some more horses
might be required, and TV-output is a must, a 6" LCD, a WLAN card,
CD/DVD, etc, etc is on the shopping list.
I am running two batteries in the car, the second battery is in the
boot and runs my PC, AMPS etc and is isolated from my main battery
when the ignition is turned off, so I never have to worry about a flat
battery. A 300W Jaycar inverter runs the PC (my homebrew DC-DC power
supply fried my first PC, and since then its been collecting dust.
It’s probably in good working order, but it was struggling to supply
the amps I needed).
I wrote some custom software to interface with WinAmp [7], a playlist
database, the Character LCD and control everything.
The Hardware:
* 1x Compaq WL200 PCI wireless LAN card (2 cards for stage 3)
* 1x Galaxy modified directional antenna (hopefully a 24dBi baby)
* 1x Omni directional antenna (still looking into homebrews)
* Cable/Connectors/etc
* A Linux PC - maybe P166 or C300 got the mobo and h/w all laying
about so no real drama what ever I decide to do.
Video Feed:
I have got a board video camera that I’m considering sticking on top
of my mast, maybe getting it to rotate (simple motor and gear job) and
posting pics on a web site (probably a wireless one) - I might even
make it interactive, little to the left.. no right.. whoa stop there.
(Anyone know the legality of this)
I've already mounted this baby on a pole and recorded a 360 degree
video of the area to help determine line of sight, but will probably
move soon so it was pointless.
I am also considering sticking a camera in my car, now that would be
cool. Live wireless video feeds at 100km/h.
The Dream:
* 80G HDD Serving as local data dump
* Maybe a game server or two (if there are none around)
* Firewalling (of course)
* A WLAN radio station would be cool, always wanted to impose my
music style on others, doubt it tho
* Several directional links to other omni nodes to provide some
redundancy
* Sat link to USA, UK, etc - when I win the lotto
* Road maps, weather reports, traffic hazards, etc
Status and To Do:
* Research, gotta be done - Currently In Progress
* Get a wireless card - Ordered a Compaq WL200 via TIB [8]
* Get Galaxy antenna - Organized.
* Cabling - No drama, just need the $
* Pigtail, reverse SMA to N
Other Bits:
Anyone using amps? The D-Link card is 30mW, directional is say 20dBi
(including cable/connector losses), that gives us 3W EIRP, if its
legal to have 4W EIRP can we amp it up.
This is not needed for directional, but with Omni's maybe, all
comments welcome.
Omni - to - Omni setup (i.e. base AP to car):
Tx Power = 20dBm (WL200) Tx Antenna Gain = 8dBi (omni) Tx
Cable+Connector Loss = 2dB => Total Tx Gain = 20+8-2=26dB => 400mW
EIRP (well below legal limit)
Rx Antenna Gain = 8dBi (omni) Rx Cable+Connector Loss = 2dB => Total
Rx Gain = 8-2=6dBi
Rx Receive Sensitivity = -84dBm => Total Power Margin = 26+6+84 =
116dBm
Allowing 10dBm Fade Margin => 106dBm
Solving: Path Loss (dB) = 10 log ( ( (4*PI*d) / lambda ) ^ 2 )
Gives us 5223 meters or ~5km LoS [9]
However if we can amp Tx power to 4W EIRP:
=> Total Tx Gain = 36dBm => 4W EIRP => Total Rx Gain = 8-2=6dBi
(unchanged) => Total Power Margin = 36+6+84 = 126dBm Allowing 10dBm
Fade Margin => 116dBm Gives us 16516m or ~16km
Of course there are other issues that need to be considered such as:
* the extra noise floor created by covering a larger area
* is 11mbps really needed in the car? if 1mbps was acceptable the
Receive sensitivity = -95dBm this gives us a range of ~18km without
amplification
* is LoS [10] possible at 16km
* the cost of amps vs. cost of travelling extra 5km
* amps need at both ends for two-way communication
* antenna on car will be more like 5dBi making things even worse
Tit Bits:
Here are some various bits of info I have collected during my many
www's on wireless do hickeys.
* Galaxy antennas come in two sizes (small 18dBi, large 24dBi)
* Galaxy antennas used down converter (2.2Ghz to TV tunable) so
cheap coax could be used
* Common council laws (may differ) allow at max 3m from top of
building or 8m from ground high antenna masts, higher than that
requires permit.
* AphaLink [11] look like releasing commercial wireless network
* 2412-2463 MHz band, 4W EIRP max power. EIRP = antenna gain (dB) *
power (W)
* 4W EIRP = 36dBm
* About 30 clients can connect to a single AP (6-8 is more typical)
* Bandwidth is shared among clients (i.e. individual bandwidth =
11mbps/#clients)
* Driving around looking for antennas IS scary and WILL piss other
drivers off
* Only 3 APs can share same air space before large performance drops
* DWL-520 PCI card (and others) required PCI v2.2 motherboard
* Lucent cards may need firmware upgrade to be 802.11b standard
* Omni antennas have typical gain of 3 to 12dBi
* Directional antennas are anywhere up to around 30dBi
* Very few (if any) cards handle bridging mode
* The following cards are NOT supported by *nix (at least not yet)
* Netware AirSurfer [12]+
* Baystack 650
* RadioLan [13] 10Mbps 5Ghz
* WebGear [14] Aviator 900Mhz
* IBM Wireless LAN Entry
* Cards with TI chipset (22Mbps)
* Prism II/II.5/III (2/2.5/3) have host AP linux drivers (with
others it is possible, maybe?)
* Card must support infrastructure mode to be used as an access
point
* There are only three non-overlapping ISM channels, 1,6,11
* radomes should have a drain hole to allow condensation to drain
(?)
* dont use spray/brush on weatherproofing sealant, very hard to
remove
* glue type heat shrink is good for weatherproofing connectors
* be care with spray painting antennas, use non-rf absorbing paint
* Avoid setting up links in Autumn as when foliage returns signal
will be lost/degraded
* use a flashlight to help determine LoS [15]
Useful Stuff:
* WirelessMathematics [16]
Comments From Others:
TysonClugg [17]> Why would you want to go all the way to 4W EIRP? If
600mW EIRP gets you connected, then using an amplifier would be
excessive. There are lots of other things aside from power output that
will affect how far you can link, such as LoS [18], ReceiveSensitivity
[19] and FresnelZone [20] to name but a few.
SirFlakey [21]>20dB on a 30mW card is 3W isn't it ? .. a 20dB power
ratio is a multiplication by 100.?
Links:
------
[1] http://melbournewireless.org.au/?LaTrobe
[2] http://www.nvg.ntnu.no/sinclair/
[3] http://melbournewireless.org.au/?Pigtail
[4] http://melbournewireless.org.au/?CoaxialCable
[5] http://melbournewireless.org.au/?ClientNodes
[6] http://mule.sworks.com/keng/unisys.shtml
[7] http://melbournewireless.org.au/?WinAmp
[8] http://melbourne.wireless.org.au/tib
[9] http://melbournewireless.org.au/?LoS
[10] http://melbournewireless.org.au/?LoS
[11] http://melbournewireless.org.au/?AphaLink
[12] http://melbournewireless.org.au/?AirSurfer
[13] http://melbournewireless.org.au/?RadioLan
[14] http://melbournewireless.org.au/?WebGear
[15] http://melbournewireless.org.au/?LoS
[16] http://melbournewireless.org.au/?WirelessMathematics
[17] http://melbournewireless.org.au/?TysonClugg
[18] http://melbournewireless.org.au/?LoS
[19] http://melbournewireless.org.au/?ReceiveSensitivity
[20] http://melbournewireless.org.au/?FresnelZone
[21] http://melbournewireless.org.au/?SirFlakey
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