An airliner mesh network over the oceans
A friend (Larry P.) once suggested to me that he thought you could build a rural mobile phone much cheaper than Iridium network by putting nodes in all the airliners flying over the country. The airliners have power, and have line of sight to ground stations, and to a circle of about 200 miles radius around them. That's pretty big (125,000 square miles) and in fact most locations will be within sight of an airliner most of the time. Indeed, the airlines already would like to have high speed data links to their planes to sell to the passengers, and relaying to people on the ground makes sense. It would not be a 100% on network, but that's OK for many users. Phones would be able to warn about outages with plenty of advance notice to handle conversations, and indeed based on live computerized data from the air traffic control system, phones could even display a list of the times they would be connected.
I was thinking more about this in the context of InMarSat, which provides satellite services to ships and planes in the deep ocean. It uses geosynchronous satellites and auto-aiming dishes, but is quite expensive. Few people launch satellites to have footprints over the ocean.
Airliners fly so often these days, spaced often just 40 miles apart along the oceanic routes. It should be possible with modern technology to produce a mesh network that transmits data from plane to plane using line of sight. Two planes should in theory be able to get line of sight at 30,000 feet if they are up to 400 nautical miles apart. The planes could provide data and voice service for passengers at a reasonable price, and also could relay for ships at sea and even remote locations.
One can also use lower bands that can go further, since there is no spectrum competition over the the open ocean, but I suspect planes don't spend too much time more than 400 miles from any other airliner (or 200 miles from any land station.) In the high bands many megabits of data bandwidth are available, and in theory spectrum allocation is not an issue when out of sight of land, so even hundreds of megabits would be possible. (We would of course not transmit on any band actually in use out there, and could even make a cognitive radio system which detects other users and avoids those bands.) An airline could offer just this service, or at a higher price switch to satellite in the few dead zones -- which again, it should be able to predict with some accuracy. Aiming should be easy, since the aircraft all transmit their GPS coordinates regularly on transponder frequencies and can also do so in the data network. In fact, you would be able to know where a new mesh partner will be approaching, and where to point, before you could ever detect it with an omnidirectional antenna. And people could be given enough bandwidth for real internet, including voice. (Though that still means they should perhaps go to a phone lounge to have long conversations.)
Of course, I often find transoceanic flights one of the rare times I get work done without the distraction of the internet, so this could also be a terrible idea.
Some technical notes: Jim Thompson points out that doppler effects make this particularly challenging, which is an issue. I believe that since we know the exact vector of ourselves and the other aircraft, and we have many more bands at our disposal, this should be a tractable problem.
Comments
rjh
Fri, 2007-04-06 09:33
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Can the financial and contractual issues be solved?
The technology should work. For noise and interference reasons higher frequencies are preferable. The hard part is persuading airlines to cooperate. It needs to be something like 80% participation before the density is high enough to work. Below that and the inevitable mesh gaps will be too common and will interfere too often. (If you look at the studies of aircraft contrails you find that mesh is a misnomer. There are heavily traveled bands and huge empty areas. This makes it hard to route around an oceanic gap.) Right now airlines are desperate to cut weight to save fuel costs, and they have higher priorities to spend what little money they have. That's a big problem. Who will pay for the communications package and its fuel use?
I fly too often and find that the current success at filling airplanes (over 85% total load factor) means that there is no longer physical room to use a computer on most flights. It's one reason that I use Amtrak on the NEC. My cell phone works there, although the TCP implementations can't deal with the rapid and dramatic variations in network delay and capacity as the trains speed in and out of individual cells. Voice mostly works, data mostly doesn't. Verizon is the exception because they made a deal with Amtrak to put repeaters on the train itself. It seems like there are a dozen people per car on their cell at any given time, and almost half the passengers are using a computer. Having a free standard 110v AC outlet for every seat makes a difference.
There are several companies trying to use aircraft to provide metropolitan service, and if they can manage the operational cost issue it is a good competitor to towers. They get one thing that your mesh would lack. They can use conformal antennae to create ground looking spot beams. This gives tremendous benefits for capacity and data bandwidth. The primary barrier for them is finding an affordable way to keep one or two aircraft overhead on a continuous basis.
The leading candidates are very high altitude UAVs. Right now, the FAA is examining how to change the flight safety rules to permit safe operation of UAVs. If that can be solved, there is then the fuel cost problem. At lower latitudes, e.g., in the tropics, the stratospheric winds are slow enough that a solar/battery combination might be able to hold position over a city for weeks. At higher latitudes the winds are too strong, and a conventional fuel is needed. This means regular up and down shuttling of the UAV and all the attendant fuel costs. IEEE Communications had a good overview of these systems some time last year.
brad
Fri, 2007-04-06 12:17
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Yes the UAVs are cool
I have also seen proposals with blimps and even kites which make use of the wind for power and to stay up.
The mesh would have gaps, though in many cases planes go the same places ships want to, though the wind patterns at sea level are of course different from those at 30,000'. For many, intermittent connectivity, especially with a known schedule, can be very useful, if not of course as useful as full time connectivity. Combined with satellite, it can also be useful -- low bandwidth use like e-mail with no attachments and text-based surfing via satellite, and high bandwidth usages when the mesh is up. And for those for whom satellite is just too pricey, intermittent connectivity is much better than no connectivity. You just know when to make your phone calls and do your sessions. It's how we used to live in the old days.
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