We have 2 buildings up north, one gets internet connection through
satellite, the other nothing...
My bosses now have decided that the other building needs to be
connected, which means I need to figure out a way to connect them....
One guy is telling me that you can get small dishes, since the
buildings are about 2 km away from each other and "in line of sight",
that will "beam" the signal over....
Basically, and the easiest way to put it..... Building 1 has server,
building 2 has internet. Building 1 needs access to server, then
eventually building 3 (which is FAR AWAY from both these buildings)
will also need access to the server in building 1. On another note,
when they go to trade shows and such to sell products they will want to
be able to access the server at building 1 to set up new accounts.....
All I can think of is using netscreens...... but having very little
knowledg about netscreens Im very hesitant on using them.... THERES
gotta be a different way!!!
Please help me out, as this needs to happen in the very near future!!!
Currently Im looking into Yagi antennas.....Trying to get any
information from suppliers is a nightmare, nobody really seems to know
anything about this stuff....
ryan2044@yahoo.ca wrote:
> Currently Im looking into Yagi antennas.....Trying to get any
> information from suppliers is a nightmare, nobody really seems to know
> anything about this stuff....
>
>
> PLEASE HELP ME!!!
>
Thats why you often need to hire someone specialized. Since it is a
commercial application with some apparent urgency why not tell the
bosses that a outside company needs to be hired just as if a new roof or
conveyor line had to be installed?
ryan2044@yahoo.ca wrote:
> My bosses now have decided that the other building needs to be
> connected, which means I need to figure out a way to connect them....
Put a commercial grade access point ($500) on a 20 or 40 foot mast
with omni antenna ($150) at one end and outside mounted subscriber
units ($250 each) at the other ends.
> One guy is telling me that you can get small dishes, since the
> buildings are about 2 km away from each other and "in line of sight",
> that will "beam" the signal over....
I don't know how small small is (but then Clinton didn't know what is was),
but a 3 ft. grill dish will run you about $400 and have same gain as a
$1,000 solid dish. Or a $100 flat panel antenna good for half the range.
> Basically, and the easiest way to put it..... Building 1 has server,
> building 2 has internet. Building 1 needs access to server, then
> eventually building 3 (which is FAR AWAY from both these buildings)
> will also need access to the server in building 1.
How far is far? Twenty miles?
> On another note,
> when they go to trade shows and such to sell products they will want to
> be able to access the server at building 1 to set up new accounts.....
> All I can think of is using netscreens...... but having very little
> knowledg about netscreens Im very hesitant on using them.... THERES
> gotta be a different way!!!
You have two options here, virtual network computing or virtual
desktopping.
However, these apps talk to the remote computer's IP address and if its
behind a router, its no trivial task to set them up.
Or you can use a Citrix based Remote Desktop app. The most well known
is the GoToMyPC that allows one PC to connect to another. Since its a
tunneling technology using the http protocol, it can see through the IT
infrastructure and not worry about port forwarding, firewalls, etc.
For distances like that you will need point to point Microwave transcievers,
not 802.11 access point hardware. You did indicate what country you are
located, if in the USA you will need a radio licensed contractor who can
survey and get clearance from the FCC as other terrestrial microwave users
may interfere with you (or them) if the signals paths parallel each other on
the same frequency. Also Microwave signals must be line of sight, otherwise
repeaters or passive reflectors must be placed where the signals can be
pointed to go around obstacles. Microwave instalations require licensing in
the US also. Bandwidth can be huge if needed- a single T-1 up to a T-3 (28
T-1s) is possible with the right hardware. Another possiblility is optical
transcievers.
<ryan2044@yahoo.ca> wrote in message
news:1162832271.902500.48800@f16g2000cwb.googlegro ups.com...
> Hey Guys,
>
> I really need some help with this one.....
>
>
> We have 2 buildings up north, one gets internet connection through
> satellite, the other nothing...
>
>
> My bosses now have decided that the other building needs to be
> connected, which means I need to figure out a way to connect them....
>
>
> One guy is telling me that you can get small dishes, since the
> buildings are about 2 km away from each other and "in line of sight",
> that will "beam" the signal over....
>
>
> Basically, and the easiest way to put it..... Building 1 has server,
> building 2 has internet. Building 1 needs access to server, then
> eventually building 3 (which is FAR AWAY from both these buildings)
> will also need access to the server in building 1. On another note,
> when they go to trade shows and such to sell products they will want to
>
> be able to access the server at building 1 to set up new accounts.....
>
>
> All I can think of is using netscreens...... but having very little
> knowledg about netscreens Im very hesitant on using them.... THERES
> gotta be a different way!!!
>
>
> Please help me out, as this needs to happen in the very near future!!!
>
>
> Thanks!
>
>
FYI, unlicensed 802.11 Wi-Fi can handle 2km with line of sight,
sufficient clearance/height to keep the Fresnel zone
<http://en.wikipedia.org/wiki/Fresnel_zone> clear, and the right
equipment.
On Fri, 17 Nov 2006 22:00:47 GMT, "lk" <lmkorenchan@ameritech.net> wrote
in <jiq7h.7925$6t.3006@newssvr11.news.prodigy.com>:
>For distances like that you will need point to point Microwave transcievers,
>not 802.11 access point hardware. You did indicate what country you are
>located, if in the USA you will need a radio licensed contractor who can
>survey and get clearance from the FCC as other terrestrial microwave users
>may interfere with you (or them) if the signals paths parallel each other on
>the same frequency. Also Microwave signals must be line of sight, otherwise
>repeaters or passive reflectors must be placed where the signals can be
>pointed to go around obstacles. Microwave instalations require licensing in
>the US also. Bandwidth can be huge if needed- a single T-1 up to a T-3 (28
>T-1s) is possible with the right hardware. Another possiblility is optical
>transcievers.
><ryan2044@yahoo.ca> wrote in message
>news:1162832271.902500.48800@f16g2000cwb.googlegr oups.com...
>> Hey Guys,
>>
>> I really need some help with this one.....
>>
>>
>> We have 2 buildings up north, one gets internet connection through
>> satellite, the other nothing...
>>
>>
>> My bosses now have decided that the other building needs to be
>> connected, which means I need to figure out a way to connect them....
>>
>>
>> One guy is telling me that you can get small dishes, since the
>> buildings are about 2 km away from each other and "in line of sight",
>> that will "beam" the signal over....
>>
>>
>> Basically, and the easiest way to put it..... Building 1 has server,
>> building 2 has internet. Building 1 needs access to server, then
>> eventually building 3 (which is FAR AWAY from both these buildings)
>> will also need access to the server in building 1. On another note,
>> when they go to trade shows and such to sell products they will want to
>>
>> be able to access the server at building 1 to set up new accounts.....
>>
>>
>> All I can think of is using netscreens...... but having very little
>> knowledg about netscreens Im very hesitant on using them.... THERES
>> gotta be a different way!!!
>>
>>
>> Please help me out, as this needs to happen in the very near future!!!
>>
>>
>> Thanks!
>>
>>
>
--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>
On 6 Nov 2006 08:57:52 -0800, ryan2044@yahoo.ca wrote in
<1162832271.902500.48800@f16g2000cwb.googlegroups. com>:
>I really need some help with this one.....
>
>
>We have 2 buildings up north, one gets internet connection through
>satellite, the other nothing...
>
>My bosses now have decided that the other building needs to be
>connected, which means I need to figure out a way to connect them....
>
>One guy is telling me that you can get small dishes, since the
>buildings are about 2 km away from each other and "in line of sight",
>that will "beam" the signal over....
802.11 Wi-Fi can handle 2km with line of sight, sufficient
clearance/height to keep the Fresnel zone
<http://en.wikipedia.org/wiki/Fresnel_zone> clear, and the right
equipment.
>Basically, and the easiest way to put it..... Building 1 has server,
>building 2 has internet. Building 1 needs access to server, then
>eventually building 3 (which is FAR AWAY from both these buildings)
>will also need access to the server in building 1. On another note,
>when they go to trade shows and such to sell products they will want to
The maximum range to building 3 will be on the order of a few miles *if*
you satisfy the conditions above. The radios will need to be pretty
high to keep the Fresnel zone clear.
>be able to access the server at building 1 to set up new accounts.....
>
>All I can think of is using netscreens...... but having very little
>knowledg about netscreens Im very hesitant on using them.... THERES
>gotta be a different way!!!
Use VNC <http://www.realvnc.com/>.
--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>
802.11 can certainly be used for distances of 2 km and well beyond, although
I don't whether it can be used for communications to building 1 (which is
FAR AWAY in capital letters.)
~ For distances like that you will need point to point Microwave transcievers,
~ not 802.11 access point hardware. You did indicate what country you are
~ located, if in the USA you will need a radio licensed contractor who can
~ survey and get clearance from the FCC as other terrestrial microwave users
~ may interfere with you (or them) if the signals paths parallel each other on
~ the same frequency. Also Microwave signals must be line of sight, otherwise
~ repeaters or passive reflectors must be placed where the signals can be
~ pointed to go around obstacles. Microwave instalations require licensing in
~ the US also. Bandwidth can be huge if needed- a single T-1 up to a T-3 (28
~ T-1s) is possible with the right hardware. Another possiblility is optical
~ transcievers.
~ <ryan2044@yahoo.ca> wrote in message
~ news:1162832271.902500.48800@f16g2000cwb.googlegro ups.com...
~ > Hey Guys,
~ >
~ > I really need some help with this one.....
~ >
~ >
~ > We have 2 buildings up north, one gets internet connection through
~ > satellite, the other nothing...
~ >
~ >
~ > My bosses now have decided that the other building needs to be
~ > connected, which means I need to figure out a way to connect them....
~ >
~ >
~ > One guy is telling me that you can get small dishes, since the
~ > buildings are about 2 km away from each other and "in line of sight",
~ > that will "beam" the signal over....
~ >
~ >
~ > Basically, and the easiest way to put it..... Building 1 has server,
~ > building 2 has internet. Building 1 needs access to server, then
~ > eventually building 3 (which is FAR AWAY from both these buildings)
~ > will also need access to the server in building 1. On another note,
~ > when they go to trade shows and such to sell products they will want to
~ >
~ > be able to access the server at building 1 to set up new accounts.....
~ >
~ >
~ > All I can think of is using netscreens...... but having very little
~ > knowledg about netscreens Im very hesitant on using them.... THERES
~ > gotta be a different way!!!
~ >
~ >
~ > Please help me out, as this needs to happen in the very near future!!!
~ >
~ >
~ > Thanks!
~ >
~ >
~
lk wrote:
> For distances like that you will need point to point Microwave transcievers,
> not 802.11 access point hardware.
For 2 KM? That's only just over a mile. Off the shelf WiFi gear
will work just fine as long as you don't have obstructions. Two
antennas at 20 feet should give you .3 Fresnel factor (70%
encroachment of the path midway) with only about five foot
variations in the ground elevations. Around 25-30 dB link budget,
so with a 15 dB fade margin, you'll have room to play with.
Most likely you d want to run 802.11g 54 Mbps gear for the
OFDM and turn it down to only 6 Mbps.
> Another possiblility is optical transcievers.
2 KM might be really pushing it for optical gear.
Proxim's TeraOpti 4221 is rated at 20 meters to 1,000 meters
for a mere $17,000 for a pair of units.
Other brands might be better.
On Sat, 18 Nov 2006 01:01:17 GMT, decaturtxcowboy
<nope_none_@nowayspam.com> wrote:
>lk wrote:
>> For distances like that you will need point to point Microwave transcievers,
>> not 802.11 access point hardware.
>
>For 2 KM? That's only just over a mile. Off the shelf WiFi gear
>will work just fine as long as you don't have obstructions. Two
>antennas at 20 feet should give you .3 Fresnel factor (70%
>encroachment of the path midway) with only about five foot
>variations in the ground elevations. Around 25-30 dB link budget,
>so with a 15 dB fade margin, you'll have room to play with.
>Most likely you d want to run 802.11g 54 Mbps gear for the
>OFDM and turn it down to only 6 Mbps.
At typical 802.11g system, with radios mounted near the antennas and
using panel or dish antennas:
TX power = +15dBm
TX coax loss = 2dB (some LMR240 plus connectors)
TX ant gain = +17dBi (typical panel or small dish)
Distance = 2km (1.25 miles)
RX ant gain = +17dBi (typical panel or small dish)
RX coax loss = 2dB (some LMR240 plus connectors)
RX sens = -84dBm (at 12Mbits/sec OFDM)
Fade margin = unknown
Plugging into:
| http://www.terabeam.com/support/calculations/som.php
Oh crap. Looks like Proxim didn't bother to renew the domain. Nice
work Proxim. Finding an alternative site for a simple path loss
calculation:
| http://www.zytrax.com/tech/wireless/calc.htm
(under System Performance):
which yields 23dB fade margin. Good enough it should work.
As for Fresnel Zone, it needs 4.8 meters clearance at midpoint, which
sets the minimum mounting height of the antennas.
>> Another possiblility is optical transcievers.
>2 KM might be really pushing it for optical gear.
>Proxim's TeraOpti 4221 is rated at 20 meters to 1,000 meters
>for a mere $17,000 for a pair of units.
>Other brands might be better.
Plaintree is slightly cheaper. The WB500 series is rates to 2,000
meters. I can't find my price list but I'll guess about $15,000 per
pair. The problem with FSO is fog, heat shimmer, solar interference,
dust, condensation in the morning, and dirt on the optics. Kinda
difficult to justify FSO costs when commodity wireless is 50 times
cheaper.
That's a rather narrow view of the current state of wireless backhaul.
There are some very good "non line of site" (NLOS) point-to-point solutions
which operate in the non-licensed 5.0 GHz spectrum.
I have personal experience with Orthogonal Systems' (now owned by Motorola)
product and have looked at similar offerings from Solectek and Alvarion.
Depending on your physical topology, this type of product may offer a cost
effective solutions for connecting your two buildings together.
"lk" <lmkorenchan@ameritech.net> wrote in message
news:jiq7h.7925$6t.3006@newssvr11.news.prodigy.com ...
> For distances like that you will need point to point Microwave
> transcievers, not 802.11 access point hardware. You did indicate what
> country you are located, if in the USA you will need a radio licensed
> contractor who can survey and get clearance from the FCC as other
> terrestrial microwave users may interfere with you (or them) if the
> signals paths parallel each other on the same frequency. Also Microwave
> signals must be line of sight, otherwise repeaters or passive reflectors
> must be placed where the signals can be pointed to go around obstacles.
> Microwave instalations require licensing in the US also. Bandwidth can be
> huge if needed- a single T-1 up to a T-3 (28 T-1s) is possible with the
> right hardware. Another possiblility is optical transcievers.
> <ryan2044@yahoo.ca> wrote in message
> news:1162832271.902500.48800@f16g2000cwb.googlegro ups.com...
>> Hey Guys,
>>
>> I really need some help with this one.....
>>
>>
>> We have 2 buildings up north, one gets internet connection through
>> satellite, the other nothing...
>>
>>
>> My bosses now have decided that the other building needs to be
>> connected, which means I need to figure out a way to connect them....
>>
>>
>> One guy is telling me that you can get small dishes, since the
>> buildings are about 2 km away from each other and "in line of sight",
>> that will "beam" the signal over....
>>
>>
>> Basically, and the easiest way to put it..... Building 1 has server,
>> building 2 has internet. Building 1 needs access to server, then
>> eventually building 3 (which is FAR AWAY from both these buildings)
>> will also need access to the server in building 1. On another note,
>> when they go to trade shows and such to sell products they will want to
>>
>> be able to access the server at building 1 to set up new accounts.....
>>
>>
>> All I can think of is using netscreens...... but having very little
>> knowledg about netscreens Im very hesitant on using them.... THERES
>> gotta be a different way!!!
>>
>>
>> Please help me out, as this needs to happen in the very near future!!!
>>
>>
>> Thanks!
>>
>>
>
>
Jeff Liebermann wrote:
> On Sat, 18 Nov 2006 01:01:17 GMT, decaturtxcowboy
> <nope_none_@nowayspam.com> wrote:
>
>> lk wrote:
>>> For distances like that you will need point to point Microwave transcievers,
>>> not 802.11 access point hardware.
>> For 2 KM? That's only just over a mile. Off the shelf WiFi gear
>> will work just fine as long as you don't have obstructions. Two
>> antennas at 20 feet should give you .3 Fresnel factor (70%
>> encroachment of the path midway) with only about five foot
>> variations in the ground elevations. Around 25-30 dB link budget,
>> so with a 15 dB fade margin, you'll have room to play with.
>> Most likely you d want to run 802.11g 54 Mbps gear for the
>> OFDM and turn it down to only 6 Mbps.
>
> You left out the antenna gains.
>
> Let's do the numbers my way. See:
> | http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations
>
> At typical 802.11g system, with radios mounted near the antennas and
> using panel or dish antennas:
> TX power = +15dBm
> TX coax loss = 2dB (some LMR240 plus connectors)
> TX ant gain = +17dBi (typical panel or small dish)
> Distance = 2km (1.25 miles)
> RX ant gain = +17dBi (typical panel or small dish)
> RX coax loss = 2dB (some LMR240 plus connectors)
> RX sens = -84dBm (at 12Mbits/sec OFDM)
> Fade margin = unknown
Here's my empirical (real life, non-calculated) measurements.
I have two 60 ft. towers 2.12 KM (1.32 miles) apart. Test gear
can be located at any height on the tower.
TX power = +17dBm
TX coax loss = 1.2dB (measured with wattmeter)
TX ant gain = +15dBi (omni)
Distance = 2.1 km (1.3 miles)
RX ant gain = +18dBi (patch antenna)
RX coax loss = 0dB (built in antenna)
RX sens = -88dBm (at 6Mbits/sec OFDM)
Fade margin = -15dB
> As for Fresnel Zone, it needs 4.8 meters clearance at midpoint, which
> sets the minimum mounting height of the antennas.
Further more, just because you have clear LOS and
clear the first Fresnel zone, you will hit null spots
at certain SU antenna heights. Notice the drop in
signal at 28 feet and the peaks at 10-20 feet and
again at 46'.
I can place two SU units almost the exact same distance
from the AP tower, and both at same elevation and only
a thousand feet apart, but with slightly different
interfering terrain figures. One SU will work great at
40 feet and nearly dead at 32 feet, but gets better at
26 feet. The other SU was optimum at 22 feet.
Information gathered from several SUs around -
* Seasonal variations and time of day can vary signal as
much as 10 dB from what I have noticed. Possible factors
are morning dew on the leaves, temperature inversions
from sun warmed earth on a cool morning, warm sundown
evening with suddenly cooling in low lying areas.
* Some locations never seem to have any significant fading
under the same variations.
* ODFM appears more robust and works with marginal paths where
DQPSK and DBPSK were unusable.
On Sat, 18 Nov 2006 22:38:48 GMT, decaturtxcowboy
<nope_none_@nowayspam.com> wrote:
Some general comments and questions:
>Here's my empirical (real life, non-calculated) measurements.
Nobody in the computer business has a "real life". Maybe a
"Half-Life" or worse.
>I have two 60 ft. towers 2.12 KM (1.32 miles) apart. Test gear
>can be located at any height on the tower.
Nice. A real test range. Does it have an elevator platform for the
test equipment?
> Fade margin = -15dB
How did you measure the fade margin? I previously had a BER
generator. I would introduce attenuation until the BER hit 10^-5. I
guess it can be done without the BER using guesswork, but it seems
difficult.
>> As for Fresnel Zone, it needs 4.8 meters clearance at midpoint, which
>> sets the minimum mounting height of the antennas.
>
>AP SU RX sig. 1st Fresnel zone
> level Clearance
>10' 10' 22.3dB .4 (60% encroachment)
>12' 12' 24.9 .4
>14' 14' 27.2 .5
>16' 16' 29.4 .6
>18' 18' 31.5 .7
>20' 20' 32.7 .7
>22' 22' 32.3 .8
>24' 34' 32.4 .9
>26' 26' 32.5 1.0
Nice plot. My guess of 4.8meters (15.7ft) seems a bit low. Looks
like 20ft is the minimum height.
>AP SU RX sig. 1st Fresnel zone
> level Clearance
>26' 10' 30.7dB .6 (40% encroachment)
>26' 12' 31.4 .7
>26' 14' 31.8 .7
>26' 16' 32.1 .8
>26' 18' 32.2 .8
>26' 20' 32.4 .9
>26' 22' 32.4 .9
>26' 24' 32.5 .9
>26' 26' 32.5 1.0
>
>Further more, just because you have clear LOS and
>clear the first Fresnel zone, you will hit null spots
>at certain SU antenna heights. Notice the drop in
>signal at 28 feet and the peaks at 10-20 feet and
>again at 46'.
I noticed the nulls. I usually ignore those unless I'm shooting
across water, airport runway, or a parking lot. The surface scatter
of most soils and surfaces is anything but perfectly reflective and
will only cause problems if smooth or reflective. I've seen far more
reflection problems with objects (buildings) at the antenna elevation
than ground bounce. What do you have for ground surface between the
antennas?
Also, having both ends of the link at identical heights is asking for
reflection problems. If the ground in between is flat, the angle of
incidence equals the angle of reflection and you get multipath.
However, if the endpoints are at different altitudes, then the chances
of finding a slightly tilted reflector is less. The point at which
the incident and reflected angles are identical is moved towards the
lower antenna, thus moving it further outside the beam pattern as it
would be in the equal height model.
>AP SU RX sig. 1st Fresnel zone
> level Clearance
>50' 10' 32.3dB .8 (40% encroachment)
>50' 12' 32.5 .9
>50' 14' 32.5 1.0
>50' 16' 32.1 1.1
>50' 18' 32.4 1.1
>50' 20' 32.1 1.2
>50' 22' 31.5 1.2
>50' 24' 29.5 1.3
>50' 26' 24.4 1.4
>50' 28' 7.9 1.4
>50' 30' 21.4 1.5
>50' 32' 28.1 1.5
>50' 34' 31.6 1.6
>50' 36' 32.0 1.6
>50' 38' 32.3 1.6
>50' 40' 32.5 1.7
>50' 42' 32.5 1.7
>50' 44' 32.5 1.7
>50' 46' 34.4 1.8
>50' 48' 32.1 1.8
>50' 50' 31.6 1.9
>
>I can place two SU units almost the exact same distance
>from the AP tower, and both at same elevation and only
>a thousand feet apart, but with slightly different
>interfering terrain figures. One SU will work great at
>40 feet and nearly dead at 32 feet, but gets better at
>26 feet. The other SU was optimum at 22 feet.
Yep. I have several over the water links that literally die when the
water is smooth and the tide is exactly the right height. The
standard solution is either spatial or frequency diversity, which is
generally beyond the means of most users. If in a fixed location,
it's easy enough to move the antennas up and down slightly to check if
they're in a null and to find an optimized location.
>Information gathered from several SUs around -
>* Seasonal variations and time of day can vary signal as
>much as 10 dB from what I have noticed. Possible factors
>are morning dew on the leaves, temperature inversions
>from sun warmed earth on a cool morning, warm sundown
>evening with suddenly cooling in low lying areas.
Temperature inversion layers, condensation inside the antenna feed,
hygroscopic coax cable, fog, coastal zone effects, etc. I haven't
seen 10dB signal strength variations in short links except those over
water or near the water. On long links, the inversion layer seems to
be the predominant source of signal variations.
>* Some locations never seem to have any significant fading
>under the same variations.
Yep. Especially those with 40dB fade margins and diversity systems.
>* ODFM appears more robust and works with marginal paths where
>DQPSK and DBPSK were unusable.
Agreed. OFDM is far more tolerant of reflections than 802.11b.
On Sat, 18 Nov 2006 13:37:49 -0700, "NoSpam" <nospam@comcast.net>
wrote:
>There are some very good "non line of site" (NLOS) point-to-point solutions
>which operate in the non-licensed 5.0 GHz spectrum.
>I have personal experience with Orthogonal Systems' (now owned by Motorola)
>product and have looked at similar offerings from Solectek and Alvarion.
>Depending on your physical topology, this type of product may offer a cost
>effective solutions for connecting your two buildings together.
Cost effective? The cheapest wireless bridge from Orthogon is the
Gemini Lite 5.8GHz 21Mbits/sec for $6,000 per endpoint. The nLOS
Gemini (not Lite) version is about $10,000 per end. That may be "cost
effective" if you need the reliability.
Also, Orthogon and others have backed away from NLOS (non-line of
sight) and are now calling it nLOS (near line of sight) primarily due
to the number of disappointed customers that expect it to work with no
visibility or Fresnel Zone clearance. The latest literature mumbles
one line for nLOS and goes on to expound on "spectrum efficiency".
Alvarion (Breezecom) sells 900MHz as their NLOS solution because it
will drill through foliage far better than 2.4 or 5.8GHz. Some early
literature mumbled something about OFDM offering NLOS capeabilities,
but that was dropped years ago.
Solectek offers 5.8Ghz as their NLOS solution, also using foliage
attenuation and Fresnel clearances. However, they at least offer a
detailed explaination of what they're selling as NLOS.
| http://www.solectek.com/files/pdf/te...est-010104.pdf
In my never humble opinion, NLOS is an open invitation to get sued by
my customers for overselling the performance, range, and reliability.
Jeff Liebermann wrote:
> On Sat, 18 Nov 2006 22:38:48 GMT, decaturtxcowboy
> <nope_none_@nowayspam.com> wrote:
>
> Some general comments and questions:
>
>> Here's my empirical (real life, non-calculated) measurements.
>
> Nobody in the computer business has a "real life". Maybe a
> "Half-Life" or worse.
My other half of life is bareback bronc riding - gave up bull riding as
too much liability.
>> I have two 60 ft. towers 2.12 KM (1.32 miles) apart. Test gear
>> can be located at any height on the tower.
>
> Nice. A real test range. Does it have an elevator platform for the
> test equipment?
50 ft. climbable Rohn 25 with 10 ft. mast
>> Fade margin = -15dB
>
> How did you measure the fade margin? I previously had a BER
> generator. I would introduce attenuation until the BER hit 10^-5. I
> guess it can be done without the BER using guesswork, but it seems
> difficult.
Sorry, I shouldn't have implied it was a measured value - its actually
a fade margin that I use in my plots that I'm comfortable with.
> What do you have for ground surface between the antennas?
Scrub brush, weeds, and cow paddies.
> Temperature inversion layers, condensation inside the antenna feed,
> hygroscopic coax cable, fog, coastal zone effects, etc. I haven't
> seen 10dB signal strength variations in short links except those over
> water or near the water. On long links, the inversion layer seems to
> be the predominant source of signal variations.
Most hops are less than five miles due to terrain. We ran an experiment
once from two points on either side of a 10 mile valley with remote
monitoring thermometers at ten and twenty feet above the ground. We
could see the path follow the temperature inversion. Seasonal praire
grass has some effect.
>> * Some locations never seem to have any significant fading
>> under the same variations.
>
> Yep. Especially those with 40dB fade margins and diversity systems.
The hill top to hill top ones are the most stable.
>> * ODFM appears more robust and works with marginal paths where
>> DQPSK and DBPSK were unusable.
>
> Agreed. OFDM is far more tolerant of reflections than 802.11b.
And it doesn't deplete D, P, S and K letters from my alphabet soup can.
"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:il54m25cd815harhal5be4a9ume7j1t42p@4ax.com...
> On Sat, 18 Nov 2006 22:38:48 GMT, decaturtxcowboy
> <nope_none_@nowayspam.com> wrote:
>
> Some general comments and questions:
>
> >Here's my empirical (real life, non-calculated) measurements.
> >I have two 60 ft. towers 2.12 KM (1.32 miles) apart. Test gear
> >can be located at any height on the tower.
>
> Nice. A real test range. Does it have an elevator platform for the
> test equipment?
Do not need an elevator for a 60 foot tower.
>
> > Fade margin = -15dB
>
> How did you measure the fade margin? I previously had a BER
> generator. I would introduce attenuation until the BER hit 10^-5. I
> guess it can be done without the BER using guesswork, but it seems
> difficult.
Yuck. I really don't like the welded rod cross members. It hurts my
feet when I'm hanging on for dear life trying to work. The 12.5"
centers is also too small for me. (Yeah, I know... I'm spoiled).
>Sorry, I shouldn't have implied it was a measured value - its actually
>a fade margin that I use in my plots that I'm comfortable with.
I was hoping you had a useful way to measure fade margin in an
installed system. The attenuator trick is the best I can do with bad
guesswork for the BER reference level. Another trick I've used is on
links where the radios have SNMP, I can usually find the OID for
retransmissions or errors. 8% PER (packet error rate) is about a BER
of 10^-5.
-15 dB fade margin is good enough in a fairly clean environment. I
consider -20dB to be a better target value for urban links.
>> What do you have for ground surface between the antennas?
>
>Scrub brush, weeds, and cow paddies.
Hmmm... I would not expect much in the way of ground reflections. The
foliage should be absorptive rather than reflective.
>Most hops are less than five miles due to terrain. We ran an experiment
>once from two points on either side of a 10 mile valley with remote
>monitoring thermometers at ten and twenty feet above the ground. We
>could see the path follow the temperature inversion. Seasonal praire
>grass has some effect.
Yep. Valleys seem good for stable paths. I have a 5 or 6 mile shot
from my house on a hillside, to a nearby peaks (Loma Prieta) that has
some Wi-Fi stuff on top. I use the path to measure antenna gain
(against a reference antenna). Not as accurate as a proper antenna
range, but good enough.
I had a real nightmare shooting across a freeway. Range was about
2000 ft. I started with an FSO (free space optical) link. Every
morning, the heat from the cars would rise to meet the cold marine
air, creating an inversion layer. The light just wouldn't penetrate
the layer, prefering to diffract along the boundary. There was a 15
to 30 minutes outage every morning. So, I switched to 2.4GHz
wireless. Same problem, but to a much lesser degree. Maybe a 5
minute outage. I've seen similar problems shooting through the marine
air boundary near the coast and the smog inversion layer during the
summer.
>> >Test gear
>> >can be located at any height on the tower.
>>
>> Nice. A real test range. Does it have an elevator platform for the
>> test equipment?
>
>Do not need an elevator for a 60 foot tower.
Read the original comment. "Test gear can be located at any height on
the tower". I read that to mean that a spectrum analyzer, signal
generator, BER tester, and an operator can function at any level on
the tower. That's quite a bit of hardware which usually requires a
platform and/or elevator.
>> > Fade margin = -15dB
>>
>> How did you measure the fade margin? I previously had a BER
>> generator. I would introduce attenuation until the BER hit 10^-5. I
>> guess it can be done without the BER using guesswork, but it seems
>> difficult.
>
>It is calculated very easily
The original comments implied that it was measured, not calculated. I
agree that it is easily calculated. I wish it were as easily
measured.
Jeff Liebermann wrote:
> "Dana" <raff242@yahoo.com> hath wroth:
>
>>>> Test gear
>>>> can be located at any height on the tower.
>>> Nice. A real test range. Does it have an elevator platform for the
>>> test equipment?
>> Do not need an elevator for a 60 foot tower.
>
> Read the original comment. "Test gear can be located at any height on
> the tower". I read that to mean that a spectrum analyzer, signal
> generator, BER tester, and an operator can function at any level on
> the tower. That's quite a bit of hardware which usually requires a
> platform and/or elevator.
Sheesh...Its only 50 ft. climb. But we have a steel cable that carries
up a padded frame for equipment. Hang a laptop with a Cognito card and
CAT5 down and remote access the laptop from another laptop.
Wireless connecting 2 buildings 
Linear Mode
