We are looking to set up a wireless network over a distance of around 5km. unfortunately one end is on an anchored barge which may move around 2-3metres in all directions (wind/tide etc). Is this feasible ?. We don't need high speed 2Mb is fine. looking at Cisco AIR-ANT1949 Yagi Antenna which quotes 10.5km at 2Mbps but not sure if this movement will result in total loss of signal.
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Wireless Networking over 5km
- Thread starter MESBEL
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I cant say for sure but I would think that the whole Line of Sight thing would eliminate the signal when the barge moved.
You might want to contact your local Cisco Rep ... we did that with our wireless questions and they came out (rep and network engineer) and answered all our questions after getting the general site survey to see our needs. That might help. Our Cisco Rep is pretty good about that even tho we are a small fry compared to most places (only 5 APs between our two buildings ... chump change to them). Matt Laski
Sysadmin, Pulsafeeder Inc.
You might want to contact your local Cisco Rep ... we did that with our wireless questions and they came out (rep and network engineer) and answered all our questions after getting the general site survey to see our needs. That might help. Our Cisco Rep is pretty good about that even tho we are a small fry compared to most places (only 5 APs between our two buildings ... chump change to them). Matt Laski
Sysadmin, Pulsafeeder Inc.
You might want to look at the antenna field strength diagram. Several yards at that distance wouldn't be significant. But any change in alignment might be. Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.
You're effectively talking about a radio transmission issue 
<marc puts his radio head on>
The Cisco YAGI is a directional antenna.
Cisco's documentation gives a minimum beam angle of 28 degrees (maximum 80 degrees), so as long as (given rocking motion) the antennaes are within 28 degrees, you should be fine.
The barge will have to be moored fore and aft - it MUST NOT turn with the tide (as the antenna's directional). The only way to avoid this would be to mount the antenna on a gyroscopic system, so it always pointed toward the transmitting antenna.
To give successful transmission, you also need to look at the "Fresnel" zone... There should be a 30ft seperation between the direct line of sight and the nearest (significant) obstacle (i.e. if you tie a piece of string to one antenna, then stretch the other end of string to the other antenna, nothing should come within 30ft of the string). This also means you need to mount the antennae fairly high - 35ft is recommended.
An alternative (if the barge is fairly near the shore) would be to broadcast from your base to a repeater on the shore (using a pair of yagi's) and attach an omnidirectional antenna to the repeater and to the barge.
(see Cisco site - for more info) <marc>[ul]help us help![li]please provide feedback on what works / doesn't[/li][li]not sure where to start? click here: faq581-3339[/li][/sup][/ul][/sup]
<marc puts his radio head on>The Cisco YAGI is a directional antenna.
Cisco's documentation gives a minimum beam angle of 28 degrees (maximum 80 degrees), so as long as (given rocking motion) the antennaes are within 28 degrees, you should be fine.
The barge will have to be moored fore and aft - it MUST NOT turn with the tide (as the antenna's directional). The only way to avoid this would be to mount the antenna on a gyroscopic system, so it always pointed toward the transmitting antenna.
To give successful transmission, you also need to look at the "Fresnel" zone... There should be a 30ft seperation between the direct line of sight and the nearest (significant) obstacle (i.e. if you tie a piece of string to one antenna, then stretch the other end of string to the other antenna, nothing should come within 30ft of the string). This also means you need to mount the antennae fairly high - 35ft is recommended.
An alternative (if the barge is fairly near the shore) would be to broadcast from your base to a repeater on the shore (using a pair of yagi's) and attach an omnidirectional antenna to the repeater and to the barge.
(see Cisco site - for more info) <marc>[ul]help us help![li]please provide feedback on what works / doesn't[/li][li]not sure where to start? click here: faq581-3339[/li][/sup][/ul][/sup]
Also check with a Cisco rep. In looking into Wireless for our company, I keep hearing that wireless transmission over water can sometimes cause an issue. Something with reflections off the water. I don't know any real hard facts, just something that you may want to ask about.
It is all going to depend on your antenna type. If your antenna is very focused the slight movement will definitely effect your signal strength. Use of an omni antenna or one with a little "slop" in it will allow for the movement however it will have less gain therefore lower signal strenght and possibly a lower speed. I know if you phone cisco or a communications company they can input all the data (ie antena height & type, cable type etc.) and run you a path study (there may be costs for this). This will tell you what signal strength to expect.
You are going to have to do the Yagi anyway to shoot 5 kilometers.
So, try it out. Over 5 km. 28 degrees becomes a reasonably broad coverage area.
The worst that can happen is that you have to fix the yagi at the barge end to land (or a handy piling) to bridge the link, and add an access point.
So, try it out. Over 5 km. 28 degrees becomes a reasonably broad coverage area.
The worst that can happen is that you have to fix the yagi at the barge end to land (or a handy piling) to bridge the link, and add an access point.
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