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Electronics

Satellite communications in 2012

High Beams

Learn to think differently about satellite communications.
After all, they’re changing fast.

Globalstar’s GSP-1700
Globalstar’s GSP-1700
offers both voice and data
capabilities on the company’s
expanding satellite system.
 

Think about this: While AT&T charges cell-phone users $2.29 per minute to phone home from the Bahamas, one satcom company charges only $1.49 per minute from anywhere in the world. Another is offering unlimited free airtime as part of $20-per-month package. Of course per-minute airtime charges don’t tell the whole story, but satellite communication is no longer restricted to the very rich or to ocean voyagers.

For most of the 20th century, conventional radio provided worldwide communications by bouncing signals off electrically charged layers in the earth’s atmosphere. Satcom systems replace atmospheric reflection by using satellites to receive and retransmit the radio signals. This produces cleaner, stronger signals, and lets the systems use higher frequencies that are much better at handling high-speed data.

There are lots of different satcom systems, but only a handful that are of practical interest to American boaters—namely, Globalstar, Iridium, Inmarsat, and VSAT. Globalstar and Iridium use satellites in “low earth orbits” (LEOs). It’s relatively cheap and easy to launch a satellite into a low orbit, but one big snag is that the area covered by a satellite (its “footprint”) depends on its altitude. For an Iridium satellite at an altitude of 484 miles, the footprint is less than 3,000 miles in diameter. So LEO systems need lots of satellites (Globalstar has 32, Iridium has 66).

Iridium OpenPort
Iridium OpenPort
uses 66 satellites in low earth orbit
to combine coverage and quality.

Globalstar is a relatively simple system in which each satellite behaves like a bent pipe, receiving a call from a mobile terminal, and retransmitting it down to one of the system’s 24 gateways that connect the satellites to the terrestrial telephone network. Calls can be connected only if the satellite can see the mobile unit and the gateway at the same time, so if you are more than about 1,500 miles from a gateway, you’ll be out of Globalstar’s coverage.

Iridium uses a larger constellation of lower, faster-flying satellites that are able to pass calls from one to another—even rerouting a call while it is in progress—so it can offer continuous worldwide coverage through just two gateways. 

 

Intellian  compact dome
Intellian makes this compact dome
to work with Inmarsat’s
FleetBroadband system.
 

Inmarsat’s satellites are in much higher orbits—22,236 miles above the equator. At that altitude, each satellite takes exactly 24 hours to complete an orbit, so it appears to hover in one place. Being so high means that the theoretical footprint of each satellite covers well over 40 percent of the earth’s surface. Inmarsat has 11 of them, so the only places that aren’t covered by at least two Inmarsat satellites are those within about 1,500 miles of the poles. But getting radio signals to and from a satellite that is 22,000 miles away requires either a lot of power or a highly directional (and accurately targeted) aerial. Inmarsat’s latest satellites however, have huge reflector dishes that focus their transmitter power into highly concentrated “spot beams” and collect even the weak signals from handheld phones. 

All three systems can handle data too, but for users who have gotten used to broadband speeds measured in megabits per second (Mbps) at prices we don’t have to think about, their performance may come as a disappointment. Inmarsat’s FleetBroadband offers a range of Internet services at speeds of up to 432kbps (kilobytes per second) through compact domes that start at about $5,000 for the 150kbps, FleetBroadband 150 service. 

About 20 percent slower but 20 percent less expensive at less than $10 per MB, Iridium’s OpenPort is a close competitor.

For serious Internet junkies or those who want to run their businesses from their boats, VSAT could be the way to go. The initials stand for Very Small Aperture Terminal, but that’s a rather unhelpful description of a system that requires a fairly substantial dome. The key thing about VSAT is that you don’t buy airtime. What you pay for is the right to use a particular satellite. Think of it as renting a private parking space for a year rather than buying a ticket to leave your car in a public parking lot for an hour. 

VSAT terminals are technically more sophisticated than those used for Inmarsat or satellite TV so prices are relatively high, with typical two-foot domes starting at about $25,000, and service plans priced at hundreds of dollars per month—but with wide variations depending on the data speed and geographical limits.

A very recent innovation promises to open up VSAT to a whole swath of recreational boaters who would previously have been put off by its price: KVH has introduced a new kind of VSAT and a new way of selling it. Metered VSAT is available through 14-inch domes that retail at around $15,000 and combine VSAT performance and an always-on Internet connection with only-pay-for-what-you-use pricing with plans starting at $49 per month including 50MB of data. 

And you can do a lot with 50MB: 5,000 e-mails, 150 Web sites, or more than an hour of MPEG music. While we can’t yet say that there’s something for every need and every budget, the options are definitely improving and may be worth a look.

Globalstar
(877) 452-5782.

Inmarsat
(202) 248-5150.

Iridium
(480) 752-5155.

This article originally appeared in the January 2012 issue of Power & Motoryacht magazine.

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