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leightonmv

join:2004-02-10
Mill Valley, CA

Internet Service to Pilot Boats 9 Miles Offshore

Click for full size
As many know, pilot boats sit offshore in order to board and pilot incoming ships with local pilots familiar with each harbor - in this case San Francisco Bay. The pilot boats will sit 9 miles offshore for up to 4 days per boat and Internet access is very sought after. We have a site on the coast at a 500 foot elevation (130 Mbps bandwidth) with a clear view of the one mile radius area the pilot boats station themselves in. Given a clean spectrum offshore, 2.4 GHz may be preferred due to about 10 dBm less fade over the 9 mile distance than with 5.8 GHz. With an antenna with a 18 degree beamwidth, the width at 9 miles is about one mile, and signal strength is projected to be about -62 dBm.

My question is the type of radio/antenna configuration to be mounted on the pilot boats. Could an array of NanoStations (50 degree beamwidth) work with the boats changing orientation? If I have the cluster of NanoStations feed into an Ethernet switch and then to a wireless router onboard, would there be a handoff from each NanoStation as the signal gets weaker on one radio and stronger on another as the boats change orientation? The boats tend to pick an orientation that lasts for several hours for comfort of the crew especially after hours. Do you see problems with that setup - or know of another setup that should be considered?

The attached picture is of a larger ship being boarded by a pilot boat (not visible).

Thanks, Leighton

raytaylor

join:2009-07-28
kudos:1

If the boats anchor, they will surely swivel around with the wind and water currents.

So this would mean an omni that can go 9 miles would be needed. Thats quite difficult, unless you were to use an array of grid antennas on the shore.
A little impractical.

An old WRT54G or Ubiquiti PowerStation EXT used to have a feature where it was an 802.11g device, but had two antennas and was able to automatically use whichever antenna had/gave the best signal. So one of these hooked up to a pair of 180 degree sectors would work. Unfortunatley, also impractical because its just old.

So next I would look at a dual chain 802.11n device such as a ubiquiti rocket which will do the same thing - though it would only be one chain operating at a time so you wouldnt expect huge speeds. This is the best option I think.

Although you could probably use mikrotik or another brand of radio, I would try out the following.

1) Set up a 5ghz sector using a rocket and use horizontal polarity only. Set the rocket to operate in single chain mode, so it doesnt try to use the vertical polarity.
Aim the sector from your high site out to sea.
If you use the 120 degree high gain rocket antenna, which is really a 90 degree, you could use two and provide 180 degree coverage with two rockets on different channels.

2) On the client end, use 4x 120 degree sectors- could probably use the lower gain ones as they are half the size.
Again you only use the vertical polarity.

3) Connect the back-to-back antennas to a signal splitter such as this one.
»www.l-com.com/bandpass-filter-rf···combiner
It will split the signal coming in/out, and therefore you would need to turn up the power level by an extra 3db to compensate or whatever your local laws allow while staying under your eirp limit.

4) Connect the North+south antennas to the chain 1 output on the rocket via the splitter, and then connect the east+west to the chain 2 output on the rocket via another splitter.

So my theory is, that by also putting the client into single chain mode, it will only use the chain that gives the best signal. Need confirmation on this. So it will use whichever pair has an antenna facing the high site, with the other antenna broadcasting out to sea and not picking up noise from the shore.

Power levels would need to be as such that you are compensating for the splitter.

This means the one client radio will need to be connected to the high site, and you are not trying to use a fancy router with failover mode and 4+ wan ports to try and get a connection from whichever radio has a signal - and not necesarily the best signal as the boat rotates.

The one client radio can stay connected, and maybe have a momentary drop as it needs to switch antenna chains every ten minutes as the boat rotates.

Another option as you suggested is to use an array of nanostations. The problem there is how do the computers within the boat know which one to use to connect to the internet?

Just found a 180 degree sector antenna. Its only 10dbi though.
»www.ebay.com/itm/5-Pack-SP-5-8-G···e28a737c

WHT or someone may want to tell us -
A splitter being fed with a 25db signal, will that mean 22db or 12.5db per output? Less the additional .5db insertion loss?

The answer to that question - I think its 22db per output, will mean that two 90 degree 19dbi antennas split would be still more effective than a single 180 degree 10dbi antenna .

We are also assuming that the sea is rather flat. The CPE antenna beam height may shoot over or under the high site as the waves rock the boat. So in that respect, a lower gain 180 degree antenna would be better than a higher gain one because the higher gain has less beamheight.


raytaylor

join:2009-07-28
kudos:1
reply to leightonmv

Just had another re-read of your post.
The nanostations would be good - they have a 16dbi gain in them.
The problem is at the client end, the nanostations themselves wont have a handoff function.

What you need is some sort of automatic failover router. It will test each WAN port by pinging a server periodically. If the server is not contactable on that WAN port, it starts natting through the secondary WAN port. And so fourth down your list.

The problem there is the boat may rotate to a point where the test server can still be pinged through one nanostation, but the signal is not strong enough to actually surf the internet or push much data through. The router would still use this marginal connection instead of the nanostation that actually has a better signal because failover setups typically have a priority - if WAN 1 can ping 8.8.8.8 then it will use WAN1 even though WAN 2 actually has the stronger signal via its nanostation because WAN1 is listed as the higher priority than WAN2.

You could possibly have the nanostations opposite each other on the mast, so WAN1 is north, WAN2 is south, WAN3 is east, WAN4 is west.
So if south or whatever pirates call the back of the boat starboard? is facing the high site, then there is less chance that WAN1 would get a signal when they are so far out with the WAN1 facing out to sea and so it wouldnt activate the WAN1 output of the router.


raytaylor

join:2009-07-28
kudos:1

1 edit
reply to leightonmv

I was about to make a joke about deploying google loons, but then i got a thinking about buoys. Our local port has a fancy path ships need to line themselves up to get into the trench before they come in - there are undersea mains cables that power lights on some buoys

Could you take my first suggestion of using the rocket with dual 180 degree antennas to talk to the high site, and place them on a solar powered buoy. Use a picostation or omni of some sort to then talk to boats around the buoys.

With the buoy about 4 miles out, so they can act as dual-radio repeaters, or perhaps even WDS repeaters.

Then the signal to the boats at the 9 mile mark will be stronger. They may even only need to use a picostation with an omni to talk to a buoy instead of trying to reach all the way to your high site above the beach.

We used to have cruise ships coming into the port almost every day and the tourists that woudl come into the nearby CBD to do some shopping / tourist attractions would always complain about the crappy 128k satelite link they have for running the hotspot on the boat.
So I put up an airgrid linked to a credit card payment walled garden hotspot on one of the houses on the hill above the port, aimed it at where the cruise ships park up and the tourists who are still on the boat can connect up and buy a $10 wifi ticket and surf for an hour at DSL speed vs $20 for 15 mins at 128k from the hotspot on the boat.




Have taken it down now since the port put their own hotspot system on the lighting towers next to the boats.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to leightonmv

There are two proven solutions for creating very long range ship to shore link at GHz frequencies for high data rates.

a) Gimbal mounted high gain antenna electro-mechanically points to the shore antenna using GPS-based software. Widely available but expensive and could be heavy for small ships. Will work with any wireless system.

b) Fixed circular array of lower gain antennas create a directional beam towards the shore antenna using complex DSP/FPGA algorithm. Elegant solution but has only been developed for custom wireless platforms which use same DSP/FPGA platform.

prairiesky

join:2008-12-08
canada
kudos:2
reply to leightonmv

I've put wireless systems on boats before and got really decent range in harbour, but that's in harbour which is wayyy different than off shore. I'd put a low gain omni on the boat itself, maybe gimble it if possible (can you do 2 dimension gimble?)

The swells and rocking are what's going to cause the biggest issues for you.


raytaylor

join:2009-07-28
kudos:1
reply to leightonmv

Beam forming of course.

Beamforming works by having 3 or more antennas in the same spot transmitting the signal at timed offsets from each other. The timed offset/delay changes so as to reach the client at the exact same time providing a much better signal. The RX i think is also better from the client.

Normally they are a flat base with little omni's on them. The beamforming hotspot in town here reaches a laptop about 1 km away.

Ubiquiti is said to be working on beamforming tech for longer distance stuff but nothing ever came of it.
Bitlomat? was also saying they have designed their CPE's for beamforming in mind.

There may be a crazy expensive other brand you could use?


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

Beamforming with Atheros or Broadcom chipsets will not work at 9 mile range or on a rapidly moving boat in choppy ocean. Maybe 1 mile range is feasible with a slow boat and calm ocean.


raytaylor

join:2009-07-28
kudos:1
reply to leightonmv

bugger



DataRiker
Premium
join:2002-05-19
00000

1 edit
reply to leightonmv

What about 900 Mhz?



John Galt
Forward, March
Premium
join:2004-09-30
Happy Camp
kudos:6
reply to leightonmv

What is the height of the AP at the shore station?


leightonmv

join:2004-02-10
Mill Valley, CA

The height of the AP is 500'. Thanks for the creative ideas. A pilot boat will go out Friday with an 8 dBi omni, that has an 18 degree vertical beamwidth. Since there is a clean spectrum out there we are going to try 2.4 GHz, a 25 dBm Bullet. If that doesn't work, the crew will also have a single NanoStation to point to shore and test out how the rocking affects reception. If that single NanoStation works then we may try an array or something similar. I'll provide an update with some results. Thanks.


bn1221

join:2009-04-29
Cortland, NY
reply to leightonmv

Would a 4G hotpots on the boat reach that far? IIRC on Lake Ontario a cell will work 5 miles out.



DaDawgs
Premium
join:2010-08-02
Deltaville, VA
reply to leightonmv

We have over complicated the problem. Nine miles is an easy shot. You can do it from far less than 500 feet. Yes the boat will be rocking and rolling, so what? Hang a three good 9 dbi Omni's on each port of an 802.11n card in a Mikrotik and orient then such that one of them will always be looking at the horizon.

Stick The highest gain antenna you can on your shore station so that your boat's orbits are covered and start moving data.

People forget about the ducting that happens over the ocean due to super hydrated air just above the ocean's surface.

Try that, refine, and repeat. This is an easy problem.
--
Once we IPv6 enable every device on the Internet we will have toasters, baby monitors, and security cameras joining the bot nets which today are populated only by idiots that can not refrain from clicking, "Yes I would like to see those titties..."



DaDawgs
Premium
join:2010-08-02
Deltaville, VA
reply to leightonmv

yeah you got it... No need for my other post. It will work and if it doesn't some 6 dB omni's will get it done.