Hi,
Has anyone got a system that automatically points antennas at moving customers working?
Perhaps by using GPS or multiple sector antennas to detect signal strength and make adjustments?
One possible application is providing network access (from a high tower) to a slowly moving crew building a road.
Another application is ship to shore links.
Am I crazy?
Yes
Which question are you responding to? 
I thought of that after I hit submit 
–Be careful what you ask for
Well, since you asked, you are not really crazy, or, crazy as I am, because you are certainly innovatively trying to put wireless to good use. Now in some circles, and I find them all the time, non-traditional connectivity is shunned because of crazy ideas. Might even be considered magic (FM), and therefore, we could all be considered crazy for trying to do some of the things that wireless guys try to do.
Now for the serious side. I was hoping I would get the notification that there was a response from you!
-Had this request before
I had a request for a ‘docking’ application for tugboats pushing barges in to load/unload oil, gas or something critical. Your requirement seems similar.
–Several Solutions Exist
One concept would require an ‘az/el’ rotator. They are typically used for satellite tracking applications. So there is the analog to your ‘slowly moving customers’. Not so crazy after all. The ability to electronically steer antennas up from the horizon, across the sky, and back down to the horizon is available. Amateur radio operators track their LEO satellites and maintain significant operating windows for reliable communications. However, the steering is dependent on knowing the ‘Kepplerian elements’ which define orbits. These are mind boggling concepts that give you an understanding of what astro-physicists do for a living. The language is English, but very hard to interpret. Nevertheless, the concept of having an input stream that would accurately track a moving satellite, with sufficient accuracy to maintain usable signal levels, is amazing that it could work in an ‘amateur’ radio environment. It doesnt take NASA to do it, just an az/el programmable rotator, a PC, a program designed for this application, and those elements. That might be rocket science, but is well within the reach of less than rocket scientists. So, being a ham operator, I didnt want to mention to anyone an idea I had to put an antenna rotator on a panel antenna to accurately zero in on customer azimuth and elevation. Sometimes even the best tower climbers point an antenna in a null, and get a pretty good signal, but possibly 10db less than you expected. This is very common, but few of us consider rotating antennas, but the concept is on the right track.
–You get what you pay for
There are antennas that are inexpensive with very high rated gain figures, and there are expensive antennas with virtually the same or less gain. Ever wonder why a rubber duck antenna could have the same gain as a 12ft long omnidirectional vertical antenna that costs $1000? The front-to-back, side-lobes, down-tilt, elevation plane beamwidth, and accuracy of the pattern really comes into play with any link. Being off by 1-3 degrees could make the difference between running at 18Mbps or 54Mbps due to signal-to-noise ratios (SNR). Rejection of undesirable signals is as important as getting the most signal from the desirable source. Actually, you really should aim to get the best SNR and best modulation rate, and therefore highest bandwidth.
Your application fits the functionality known as beam-steering. I dont know what your level of expertise is, so you will probably have to elaborate on that a little. There are a couple cellular antenna manufacturers that incorporate smart antenna technology, and some of them have models that operate in other bands. Those bands typically are also licensed, like 2.5GHz MMDS, etc., so they will naturally be expensive. However, there are some reasonably prices antenna systems out there.
–The Explanation
That concept fits a technique called ‘null-filling’, and ‘null-steering’ which is a natural companion component of beam-steering. There was a Silicon Valley company called BeamReach that claimed all these concepts, to the point that I dont think anyone believed them. ArrayComm (I think) has a concept called I-Burst (to my best recollection) which had similar characteristics. One of them even claimed exactly what you have described–‘tracks mobile cellular users moving down the highway, while maintaining optimum connectivity while within range’. It claims to also have the side effect of increased capacity for the cell site. Again, hard to fathom, but the 800 pound gorillas effectively use them to their benefit. When radio capacity is maxed out, use the physics of brute force antenna technology to get more out of the system. Another manufacturer claims ‘cosequent squared null filling’! Say What 
I have very high skyscraper based antennas. I am sure I want that. It must ensure extremely even signal levels across the beamwidth, especially in the lower elevation (down-tilt) coverage area.
–Outside the Box Methods
I have used the MT bandwidth test tool, running live during aiming, and aimed for the highest bandwidth. It most definitely worked, and was very interesting to watch. Thats what spawned the idea to put up an az/el rotatable, very narrow beamwidth panel or dish antenna. Seems strange, but you might find less signal with better SNR, yielding highest bitrate. The MT bandwidth test tool will stop and restart on its own during a this type of operation which is very convenient.
–Some reasonable but potentially viable solutions
Conceptually, I have given you an RF engineering example of a solution to the problem. However, it his highly likely you can accomplish your goals with a much more simple, but elegant solution. This depends on quite a few location and network specific parameters. Other simple solutions could incorporate such concepts as:
-High gain sector antennas of the correct polarization, some you might not be aware of. There are cellular antennas that arent vertical, horizontal, or circular! How about 45 degree polarization. Innovative RF engineers correctly deduced that cell phone users holding a cell phone to their ear, hold it at a 45 degree angle…actually totally makes sense.
-Multiple radio installations that incorporate hand-off between radios. These typically use a technology called ‘make before break’. These might be within the realm of a mesh network.
-Simple brute force technique that has a very high ‘processing gain’ and very high link budget. In other words, blast so much signal, and have receive sensitivity so high that the connections are unlikely to break within the coverge area.
–Mantra from the Soapbox
I am getting verrry sleeeepy, but if you have read this far, I hope it has given you some valuable insight and information on consideration. My mantra is: No RF link has ever beat me–I always design the connectivity to be suitable for the particular purpose intended. That always covers everything. No link has beaten me because, calculating the potential for success must be a component of the RF engineering. Getting signal into a lead cage is not feasible, and if I would specify a solution, it would be to get rid of the lead cage 
. Certain unrealistic network owners have asked me to ‘just make it work’. I have agreed based upon the contingency that they either move their building, or increase its height. Sometimes a tower would suffice, but it still might require moving the building. I sometimes wonder why businesses dont check broadband availability before they change location.
–Conclusion and Feedback
Enough for now, but let me know if I have confused you with too many facts, or if I have shed any light on your requirement, or if I have totally misinterpreted your requirement. I really need to know certain parameters such as coverage area, operating frequency, maximum distance requirement for link maintenance, type of equipement you are contemplating to use, and finally, what budget range are you in.
–Crazy Excuse
Sorry for the verbose answer, but it is an area that piqued my interest, and it just struck me to answer ‘Yes’ to elicit a response if you are serious, just forgot to mention ‘yes’ to what. Your quick response indicates you are serious, and dont really want to be considered crazy! Or, you might now think it is a crazy idea due to the nature of the solutions that would be required to implement. I dont remember where you are, but if you are in the US, and answered me now, we both are up in the middle of the nite on forums, and it is crazy that I have the energy to stay awake and respond.
–Topic for a User Meeting
Got to stop…Are you going to MUM?
Going to be too busy setting up crazy links.
I have a simpler solution in mind for ship to shore communication. Setup a GPS, a SBC, a radio, and a 25 dB or so antenna on a ship on a device that can control direction and tilt (like what they use for CCTV cameras or sat dishes). Setup a few APs on shore (more on that later).
Load up the ship computer with the GPS co-ordinates of all the on shore APs. The ship knows where it is, its heading, and where all the APs are so it can point it’s antenna at the closest AP.
On the AP side, two options:
As for your response, it’s quite a bit longer than I expected. I understood all of it, even through you tried to make some concepts and technologies sound more complicated than they really are to use
RK,
Thats why I really needed to understand your level of understanding. I didnt know if I should give a tutorial or just tell you try several nodes with antennas point in the general direction, and collect data.
BTW, the geo-coordination of radios has been around for quite a while. The Metricom Ricochet network used Lat/Long for vectoring traffic, and before that it also had a predecessor product for the electric utility industry that collected data and controlled the power grid with their utilinet product.
Sorry I made a thesis about it, but I must have been in a prolific writing mode. I am developing web content right now, and some of these topics have been rolling around my head for use on the site. Probably can extract a couple phrases from the message, after I read it again.
I am glad you at least understood it. It makes the time writing well spent. On my way to a meeting, and of course late, so later I will read it and analyze your comments. Often, I feel my work is flying over peoples heads, and I am preparing presentations at this time for an audience with a wide range of expertise. I know I hate it when someone explains something ad nauseum because they want to make sure I get the point, when I got it long before 
I can resist mentioning that I have used 900MHz of many flavors successfully when moving at highway speeds. I have even connected on 5GHz at several miles doing 60Mph, so I know its possible to do your project. I was also doing research on these Multi-Polarity antennas that are supposed to perform miracles. The consensus among fellow engineers is that is a broadcast technique used for many years.
So would sure like to know if your project is successful.
Yes. My ideas are certainly not earth shattering.
What I’m trying to find out is whether someone has actually done something similar with wifi.
There is an opportunity to provide inexpensive (as compared to satellite) Internet access to ships near the coasts and in the great lakes.
Sailors will appreciate being able to make some cheap phone calls and do some video conferencing with family while being stuck on a ship for weeks at a time.
This could be a viable business along any popular water shipping route.
Boats and ships pitch and roll, which will mess with a high gain antenna. Many boats have multiple omni antennas for much less finicky VHF stuff; a tall antenna with a narrow pattern doesn’t work in bad weather, but has great range in smooth weather. A small antenna with lower gain has a more forgiving pattern.
I would suggest a roaming based system, because if you track something, that radio/antenna is only good for that one customer. Difficult to justify businesswise when you only have three clean bands of 2.4 for wifi type links. 2.4 and 5ghz also have huge swings in performance based on tide. See that attached file for my 2.4ghz link from the mainland to a small island 2 miles away.
If your links were higher above sea level, say another 100m, would tide still have a large impact?
I may have only 3 clean bands but I can charge for one day of use the same as you charge for a month of use.
Have you seen the kind of prices ships pay for satellite access?
My brother works on ships. He uses a cellular data card very successfully when near the coast or on a river for Internet. You’d have to reach well beyond the range of cellular to be useful.
On my link, my end is about 100’ ASL, the other is 25’ ASL. We also see the same thing at another location where the tower is 600’ ASL.
For the record, motors are not fast enough for beam targeting.
A Multiplex antenna array with a custom designed asic to create latencies in the correct anntennae to steer the signal in a simular way that surround sound works, would be required, for practical steering purposes.
IBM and other companys already clam to have this technology.
What if my target is 20 km away?
I think a motor would be plenty fast enough.
Interesting to see this post.
I am working on such a system. Nothing new here, has been done for years at http://www.mbari.org although not using inexpensive WiFi hardware. But, yes it is possible to track the ship based on reported GPS position, and direct a shore based high gain antenna towards it. That end is relatively simple. Out on the ship it gets more complicated due to the motion. The current solutions mount an az-el actuator on a gyroscopically stabilized gimbal (think heavy spinning wheels). If your az-el actuator is fairly quick (and strong), you can dispense with the gyro, but we are talking expensive electromechanics there…
Best compromise is to use an omni antenna on the ship, and put as much gain as possible into the shoreside antenna. At distances where you will need the additional gain, the angular rate of the ship as seen by the shoreside antenna is low. Close in, you switch to a sector antenna.
See: http://www.mbari.org/twenty/LiveLink.htm
I worked with Gary W6STR (SK) during my time there…
The idea about using camera pan/tilt units as antenna pointing mechanisms is a good one. Market demand allows us to buy a fairly complex electromechanical system for cheap. After that, it’s just a matter of programming…
I’ve developed an external circuit to allow switching between two antennas (omni and directive) under script control. The relay I’m using right now is good to 6GHz.
I did some experiments last summer on the Black Sea off Sevastopol, using RB133/XR2 and H-polarized 13db omnis. Antenna heights were 100’ and 15’. Was able to carry 13Mbps MPEG streams between ships out to over 10 miles on flat calm days. As they say ‘your mileage may vary…’
More as it happens…
_Dave KC6UPS
A gyroscopically stabilized gimbal is indeed heavy, plus you need extra power to keep these wheels spinning.
The point is to make an easy to use system that can be mounted on anything from a yacht to a large cargo ship.
After much searching, I found an affordable device which can move 20 lbs at 50 degrees per second. I think that’s fast enough.
Dave, I’ll contact you on AIM to share ideas.