View Full Version : ultra long distance backhaul using Bullet5HP or Bullet2HP
Hello,
One of the issues we have is that VSAT is the only way we can get our bandwidth where we are but there is a city about 350km away that has a fibre backbone to overseas.
I know this may really be pushing the boundaries but what would be a realistic maximum distance we might achieve with a BulletHP and a 30dbi gain parabolic grid antenna. We have plenty of mountains we can use to achieve good line of sight. There are also lots of potential customers along the way.
We would like to get somewhere close to 2-3mbps but we could live with a few minutes of downtime per day. We get lots of downtime on VSAT because of rain anyway, and we would still be keeping the VSAT as a backup.
Could we do it like this:
Bullet5HP<--100km--> Bullet5HP-ethernet-Bullet5HP<--100km-->Bullet5HP-ethernet-Bullet5HP<--100km-->Bullet5HP
If interference is not an issue then would we be better off trying this with Bullet2HP?
If this is simply not realistic at all then please let me know.
For a 100 KM (62 miles) shot at at 2.4 Gig and 24 Mbps (end users will experience a 12 Mbps speed test) using a Bullet 2 at full 30 dBm (1 Watt) with 29 dBi dish antenna at both ends, you'll have like a 28 dB or so fade margin, which is very good. Drop your speed to 6 Mbps (end users will experience a 3 Mbps speed test) and your fade margin jumps to 40 dBm, which is excellent.
At 5.8 Gig and 24 Mbps (end users will experience a 12 Mbps speed test) using a Bullet 5 at full 30 dBm (1 Watt) with 32 dBi dish antenna at both ends, you'll have like a 30 dB or so fade margin, which is very good. Drop your speed to 6 Mbps (end users will experience a 3 Mbps speed test) and your fade margin jumps to 38 dBm, which is excellent.
This may help you
http://www.terabeam.com/support/calculations/som.php
But that's assuming a free and clear Fresnel clearance.
Do you have any GPS numbers of the head and tail end along with some mountains in between?
CharlesA920
12-22-2008, 06:01 AM
have you seen this?
http://www.engadget.com/2007/06/19/venezuelans-set-new-wifi-distance-record-237-miles/
Yes I have seen the Venzuelan studen't world record. It is very interisting but that was a science experiment and I want to gauge what wan be done for a real world production backhaul.
Best Regards
Otto Melzig
Most of these guys are licensed radio operators and can run as much power (antenna gain and amplifiers) to make a connection, and it only requires a few packets to be passed over a short period of time to qualify for a record.
Nothing comparable to a commercial deployment.
two words: earth curvature
Yes, what you want to do will work, but you have to find high enough mountains. It will be easier if you do 50km links instead.
Don't forget to consider your power source.
"two words: earth curvature "
Like the guy that wanted to do a 120 mile link between two islands that were only 400 feet and 10 feet above sea level. He would have needed 3,500 foot towers at both ends.
sitehost
02-16-2011, 01:53 AM
"two words: earth curvature "
Like the guy that wanted to do a 120 mile link between two islands that were only 400 feet and 10 feet above sea level. He would have needed 3,500 foot towers at both ends.
that would only be assuming there was no line of site correct?
and also the tower wouldn't have to be 3500 feet, it would only have to entertain a line of site senerio.. so if the tallest elevation was 400', Plus any infrastructure (trees,buildings) the tower would only have to be taller then the mountain, to create a line of site.
is this thinking correct..
gfinney
02-16-2011, 06:37 AM
that would only be assuming there was no line of site correct?
and also the tower wouldn't have to be 3500 feet, it would only have to entertain a line of site senerio.. so if the tallest elevation was 400', Plus any infrastructure (trees,buildings) the tower would only have to be taller then the mountain, to create a line of site.
is this thinking correct..
It is not about line of site, it is about the clear fresnel zone. You can have situations where you can clearly see the other antena, but with enough obstruction to the fresnel zone, you will not be able to establish or maintain a usable link.
On the water example, don't forget that the signals can bounce off the water and reak all sorts of havock, which would require taller towers.
