Long Range Wireless Network
 

I am trying to establish a wireless network for Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

Does anybody has experience/advise with this ?

Long Range Wireless Network
 

On Wed, 10 Oct 2007 07:16:24 -0000, wrote:

I am trying to establish a wireless network for Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

for such application you will need on both sides approx. 80cm (offset
used Sat) dish with properly mounted a proper feed to it; visual line
w/o obstacles in-between is a must ! get some clues:
http://www.seattlewireless.net/DirectionalParabolic

--
Regards , SPAJKY ®
mail addr. @ my site @ http://www.spajky.vze.com
5y - "Tualatin OC-ed / BX-Slot1 / inaudible setup!"

Long Range Wireless Network
 

wrote:
I am trying to establish a wireless network for Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

It's probably illegal. In the U.S., EIRP limits are 1w for portable/mobile
units and 4w for fixed (point to point links). For example, the infamous
Pringles can antenna is at the border of illegal for point to point links,
and is definately illegal for mobile or portable use.

I don't know what the EIRP limits are if you are out of the U,S. here
in Israel it's 100mw, effectivly making gain antennas without a long
(high loss) feed line illegal.

About the only way to do it with such a wide radius is a MESH network and
gain antennas with 10db (10x) gain. Using a transmitter power of 100mW
(which is the standard), you will be just at the limit. The extra gain
of the antenna will also help increase the range of the remote units.

A cheap MESH network can be but together using Linksys WRTG54-L routers
(note the "L" suffix) and third part firmware such as TOMATO
(www.polarcloud.com).

You will need to do some inteligent design of the network, you want to
MESH with the least number of hops to your Internet connection.

20 KM, is an awfully long range for a MESH network anyway. If you
have a reliable range of 150 feet (50m) per node, and place them 300m
apart, a strip 20km long by 100m wide would need 50-60 nodes depending
upon terrain, buildings, etc. With a possible 25 hops between a remote
device and the Internet, latency would be too high (it would take too
long) for VoIP or videoconferencing. Web surfing, email, file transfer,
data telemetry, would probably be ok.

WiMax would be better, if it delivers on promised performance, you
would be able to place your nodes as far as 4 miles apart (2m range).

Meanwhile if you can combine a MESH and fiber optic network, you would
get much better results, but at a much higher cost. You no longer would
be able to use cheap routers and there is the cost of the fiber.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838
Visit my 'blog at http://geoffstechno.livejournal.com/

Long Range Wireless Network
 

In article ,
(Geoffrey S. Mendelson) wrote:

20 KM, is an awfully long range for a MESH network anyway. If you
have a reliable range of 150 feet (50m) per node, and place them 300m
apart, a strip 20km long by 100m wide would need 50-60 nodes depending
upon terrain, buildings, etc. With a possible 25 hops between a remote
device and the Internet, latency would be too high (it would take too
long) for VoIP or videoconferencing. Web surfing, email, file transfer,
data telemetry, would probably be ok.

20Km isn't at all a long distance, IF one uses High Gain antennas on
both ends of the 2.4Ghz link. My T1 Phone link runs 20Km using Part15
Devices (LynxBoxes) and 6 Ft Parabolic Dish Antennas on each end.
We had to install a 6DB Attenuator in the Feedline at both ends of the
Link, just to keep the RSL in the AGC Range of the Receivers. One just
needs to understand the parameters of the Path being used, and the
hardware required to make the Path work with the appropriate Path Losses
involved.

This is an Unlicensed Link owned and operated by ALASCOM, our Longlines
Carrier.

It also is colocated with a WiFi Network of Access Points that
distributes IP Traffic to our local community, which I own and
Operate. It is a matter of RF Engineering. Get that right, and
things can be worked out.

Bruce in alaska
--
add path before @

Long Range Wireless Network
 

Bruce in Alaska wrote:

In article ,
(Geoffrey S. Mendelson) wrote:


20 KM, is an awfully long range for a MESH network anyway.

snip

20Km isn't at all a long distance,

snip

I think the O.P.'s problem is regulatory issues regarding EIRP
in his country preventing him from using hi-gain antennas.

Regards,

Michael

Long Range Wireless Network
 

In article .com,
wrote:

I am trying to establish a wireless network for Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

Does anybody has experience/advise with this ?

As I understand the problem, the network would cover an area with a 20Km
RADIUS. You include a reference to an omnidirectional antenna and a
"powerful" radio, with the base station antenna mounted sufficiently
high to be line-of-sight from the end-users.

My thought is that you are a bit naive, describing a one-way system
similar to a Television or FM Broadcast Station. There are existing
systems used for providing community internet access, and I don't think
that is how they work!

While I'm not familiar with the community systems, there are technical
problems with your proposal. For one, it is a two-way system. If high
power is required at either end, it is required at both ends. Even with
a high gain antenna at the remote end, the gain works on both
transmitting and receiving.

For another, by using a single base station site to cover such a wide
area, the base station receiver will be exposed to various noise sources
over that entire area. The total interference from these sources will
reduce data rates for all users' transmissions toward the base station.

Perhaps Geoff's MESH Network or Bruce's WiFi Network would be a good
approach, but breaking the coverage area down into a more manageable
size and using multiple sites.

Fred
K4DII

Long Range Wireless Network
 

On Oct 11, 4:50 am, Fred McKenzie wrote:
In article .com,

wrote:
I am trying to establish awirelessnetworkfor Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

Does anybody has experience/advise with this ?

As I understand the problem, thenetworkwould cover an area with a 20Km
RADIUS. You include a reference to an omnidirectional antenna and a
"powerful" radio, with the base station antenna mounted sufficiently
high to be line-of-sight from the end-users.

My thought is that you are a bit naive, describing a one-way system
similar to a Television or FM Broadcast Station. There are existing
systems used for providing community internet access, and I don't think
that is how they work!

While I'm not familiar with the community systems, there are technical
problems with your proposal. For one, it is a two-way system. If high
power is required at either end, it is required at both ends. Even with
a high gain antenna at the remote end, the gain works on both
transmitting and receiving.

For another, by using a single base station site to cover such a wide
area, the base station receiver will be exposed to various noise sources
over that entire area. The total interference from these sources will
reduce data rates for all users' transmissions toward the base station.

Perhaps Geoff's MESHNetworkor Bruce's WiFiNetworkwould be a good
approach, but breaking the coverage area down into a more manageable
size and using multiple sites.

Fred
K4DII

Thanks for the responces, the proposal as rightly said is no different
from Wireless networks deployed by ISP in small communities. All I
need is pointers to hardware that can be used to archive this winthin
legal limits. The WiFi Solution seems to me more resonable as braking
the area into chucks means that some sites would be dependent on
others

Long Range Wireless Network
 

In article . com,
wrote:

Thanks for the responces, the proposal as rightly said is no different
from Wireless networks deployed by ISP in small communities.

I think you are zeroing-in on a plan that will work. My point is that a
20Km radius is NOT a small community. While the VSAT link may have
sufficient bandwidth, your wireless distribution system may not.

It would help reduce the load by using a higher bandwidth method such as
fiber, to interconnect the various local wireless base stations to the
VSAT terminal, rather than using the wireless systems themselves for
inter-site distribution.

Remember that a wireless system's bandwidth is divided among all the
users. As more users access the network at any one time, the slower
will be the response.

Fred
K4DII

Long Range Wireless Network
 

On Oct 12, 11:55 am, Fred McKenzie wrote:
In article . com,

wrote:
Thanks for the responces, the proposal as rightly said is no different
from Wireless networks deployed by ISP in small communities.

I think you are zeroing-in on a plan that will work. My point is that a
20Km radius is NOT a small community. While the VSAT link may have
sufficient bandwidth, your wireless distribution system may not.

It would help reduce the load by using a higher bandwidth method such as
fiber, to interconnect the various local wireless base stations to the
VSAT terminal, rather than using the wireless systems themselves for
inter-site distribution.

Remember that a wireless system's bandwidth is divided among all the
users. As more users access the network at any one time, the slower
will be the response.

Fred
K4DII

Just to chime in on this topic, I think some incorrect information was
passed along regarding legality of transmission power - the FCC does
in fact limit unlicensed maximum transmission wattage on the 2.4Ghz
range, however the use of high gain antennas is NOT illegal. You can
use extremely high gain directional antennas to achieve links over a
20+ mile LOS link, and still be within legal limits for unlicensed
operation. Think of it as using as talking thru a funnel - all it is
doing is using that same power more efficiently and more focused. Now
if you are talking about running the signal thru and actual signal
amplifier, then yes, that would be illegal.

2 cents

Long Range Wireless Network
 

wrote:
Just to chime in on this topic, I think some incorrect information was
passed along regarding legality of transmission power - the FCC does
in fact limit unlicensed maximum transmission wattage on the 2.4Ghz
range, however the use of high gain antennas is NOT illegal. You can
use extremely high gain directional antennas to achieve links over a
20+ mile LOS link, and still be within legal limits for unlicensed
operation. Think of it as using as talking thru a funnel - all it is
doing is using that same power more efficiently and more focused. Now
if you are talking about running the signal thru and actual signal
amplifier, then yes, that would be illegal.

Unfortunately, this is also incorrect. The limit is for EIRP. The more focused
the beam, the higher the EIRP.

The exact limit the U.S. is 1 watt EIRP for mobile devices and 4 watts
EIRP for fixed (point to point) links. That's a combination of transmiter
power plus antenna gain plus feed line loss.

Ham radio is limited to transmitter output power, which is quite different.

It could be worse, the limit here is 100mW EIRP.

Geoff.






--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838
Visit my 'blog at http://geoffstechno.livejournal.com/

Long Range Wireless Network
 

On Thu, 18 Oct 2007 04:04:01 +0000 (UTC), (Geoffrey
S. Mendelson) wrote:

wrote:
Just to chime in on this topic, I think some incorrect information was
passed along regarding legality of transmission power - the FCC does
in fact limit unlicensed maximum transmission wattage on the 2.4Ghz
range, however the use of high gain antennas is NOT illegal. You can
use extremely high gain directional antennas to achieve links over a
20+ mile LOS link, and still be within legal limits for unlicensed
operation.

Running a 32 km LOS link is problematic in practice. At least the
first Fresnel zone should be clear of obstacles. At midpoint you
should have about 30 m free space _below_ the direct optical path
(i.e. you would have to add 30 m to the antenna towers), but still you
should have 10-20 dB fade margins for reliable operation.

Think of it as using as talking thru a funnel - all it is
doing is using that same power more efficiently and more focused. Now
if you are talking about running the signal thru and actual signal
amplifier, then yes, that would be illegal.

Unfortunately, this is also incorrect. The limit is for EIRP. The more focused
the beam, the higher the EIRP.

The exact limit the U.S. is 1 watt EIRP for mobile devices and 4 watts
EIRP for fixed (point to point) links. That's a combination of transmiter
power plus antenna gain plus feed line loss.

Assuming ordinary +20 dBm cards with 16 dBi antennas at both ends, you
would end up to the +36 dBm EiRP (4 W) transmit power. The free space
loss at 32 km and 2.45 GHz is 130 dB, so the receiver would get -94
dBm, which is very little for broadband traffic, especially that
figure does not contain the fade margin. In fact using +10 dBm cards
and 26 dBi antennas would give 10 dB more receiving power.

Ham radio is limited to transmitter output power, which is quite different.

It could be worse, the limit here is 100mW EIRP.

If you can find a WLAN card with separate Rx and Tx port, put an
omnidirectional antenna on the Tx port and a 2 m paraboloid (30-33 dBi
gain) on the Rx port and quite long point to point systems could still
be built. Of course any interference within the beam would also be
picked up.

Paul OH3LWR

Long Range Wireless Network
 

Paul Keinanen wrote:
Assuming ordinary +20 dBm cards with 16 dBi antennas at both ends, you
would end up to the +36 dBm EiRP (4 W) transmit power.

Which puts you right at the legal limit for the U.S. If your transmitter
is slightly higher power, or the antenna is more efficent you go over
the limit.

The free space
loss at 32 km and 2.45 GHz is 130 dB, so the receiver would get -94
dBm, which is very little for broadband traffic, especially that
figure does not contain the fade margin. In fact using +10 dBm cards
and 26 dBi antennas would give 10 dB more receiving power.

If I understand you correctly the EIRP would remain the same?

Around 1980 I worked a place that used IR beams for high speed (4800bps),
data and it worked until someone built a hotel in the way. :-)

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838
Visit my 'blog at http://geoffstechno.livejournal.com/

Long Range Wireless Network
 

In article ,
Paul Keinanen wrote:

Running a 32 km LOS link is problematic in practice. At least the
first Fresnel zone should be clear of obstacles. At midpoint you
should have about 30 m free space _below_ the direct optical path
(i.e. you would have to add 30 m to the antenna towers), but still you
should have 10-20 dB fade margins for reliable operation.

I understand that there's another issue with long links which can
cause some problems. 802.11 cards are designed to automatically
acknowledge packets received, and retransmit them if they aren't
acknowledged promptly. This retransmission protocol is done by the
card firmware, and occurs below the level of any operating-system
packet acknowledgement or retransmission (e.g. TCP).

The automatic-retransmission timeouts in the cards are set to a fairly
short time-period, in order to improve throughput under typical usage
conditions.

A 32 km link is going to have a round-trip time of around 200
microseconds. If the transmitting card's timeout value is set to less
than this, it'll start retransmitting the "lost" packet before a
successful acknowledgement can come back. Lather, rinse, repeat.

Traffic will actually get through, I gather... the successfully-
received packets will be forwarded to their destination, even though
the sending card thinks that they haven't been received (and logs them
as "discarded, excessive retransmits"). Throughput suffers badly,
though.

Some cards and/or access points apparently allow the retransmission
timeout value to be changed, to allow for sufficient speed-of-light
travel time.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Long Range Wireless Network
 

On Thu, 18 Oct 2007 11:22:20 -0700, (Dave Platt)
wrote:

In article ,
Paul Keinanen wrote:

Running a 32 km LOS link is problematic in practice. At least the
first Fresnel zone should be clear of obstacles. At midpoint you
should have about 30 m free space _below_ the direct optical path
(i.e. you would have to add 30 m to the antenna towers), but still you
should have 10-20 dB fade margins for reliable operation.

I understand that there's another issue with long links which can
cause some problems. 802.11 cards are designed to automatically
acknowledge packets received, and retransmit them if they aren't
acknowledged promptly. This retransmission protocol is done by the
card firmware, and occurs below the level of any operating-system
packet acknowledgement or retransmission (e.g. TCP).

Fade rates typically vary between a few times a second to several
days, thus resending a frame one millisecond after the initial frame
is not usually going to make a big difference, if the initial frame
was, say 10 dB below the threshold (i.e. deep in the noise).

While COFDM and various spread spectrum systems will help combating
(fast) frequency selective fading, but these do not help in slow fade
due to varying vertical atmospheric temperature and humidity profiles.

You still need the fade margin for slow fading, if reliable
communication is required.

The situation is different in typical amateur radio usage, in which
you are most interested in rare situations, in which the signal
strength increase above the average signal level, thus increasing the
communication range in rare occasions.

Paul OH3LWR

Long Range Wireless Network
 

You can try the Motorola Canopy system. We, at work, use both the 5.7 GHz
and the 900 MHz systems and get a good 20 to 30 KM range. The web site is
http://motorola.canopywireless.com/solutions/

Norman
wrote in message
oups.com...
I am trying to establish a wireless network for Internet Access, Video
Conferencing and Intranet Applications, I though to use either a
2.4GHz Sector or Omni Directional Antenna would do the job but I can
find any product that goes as far the distance I am trying to cover (a
radius of 20Km). My idea is to use a powerful radio with the Antenna
monted on a tall mast at the location of the internet feed (via VSAT),
this location is idea for LOS at the other locations.

Does anybody has experience/advise with this ?

Long Range Wireless Network
 

An ISP in my area has a rather large wireless network established, probably 30 miles from main office to my end of their network. I am at the far end of the network, about 12 access points "deep", meaning my traffic hops through 12 bridges-access points (repeaters) before it reaches the ISP's backbone. It works fairly well for internet browsing, better than I would have thought, but I've never tried internet telephony or video conferencing. That ISP is using 802.11b radios throughout the network, so the network certainly can't handle a lot of internet traffic, but it works.