How Satellite Phones Work


War zones and disaster areas are a bridge too far for many cell phones. Satellite phones, though, work just about anywhere on the planet.
Courtesy Iridium

Cell phone technology marches relentlessly forward. What were once luggage-sized bricks that made only voice calls are now slender smartphones with capabilities limited only by your imagination. Well, your imagination ... and your signal. Cell phones require cellular towers, which connect with varying (and often disappearing) signal strength. In those places where cell phones dare not wander -- that's where satellite phones prove their mettle.

Satellite phones boldly go where cell phones can't. They let you make phone calls from almost anywhere because their primary infrastructure is literally out of this world. Satellite phones don't rely on a terrestrial cell phone network. Instead, they beam their data directly to and from satellites orbiting Earth.

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That technological leap unleashes satellite phones (or sat phones) from the bonds restricting their Earth-based brethren. Thus, they are the communication devices of choice in areas with minimal or non-existent cell coverage, such as sparsely populated or poor countries, locations where governments restrict cell and Internet access, or where natural disasters wreck ground-based systems.

In satellites systems, phones aren't always referred to as phones. Instead, many people call them terminals. No matter the name, they're the necessary end-user device that you need to connect to a satellite.

As with cell phones, terminals have all basic phone features. Yet, even though they are heavier and bulkier than cell phones, they aren't brimming with the nearly endless capabilities that your smartphone has. Instead, a sat phone is a stripped-down phone that you'll primarily use to place calls or send short text messages.

You might wonder how a satellite phone is different than the GPS (global positioning satellite) capability that's built into so many contemporary smart phones. GPS doesn't let you make calls or send texts; instead, it's simply for determining your location on the planet. Armed with GPS data, your phone can map your way to a distant city or find the closet Chinese restaurant. A sat phone, on the other hand, lets you make calls and transfer data via its satellite connection.

Keep reading and you'll see how satellite systems are sometimes superior to cell networks, and how not all sat phone configurations are the same.

A Satellite by Any Other Name

Satellite phones work with either low earth orbit systems or much higher geosynchronous systems. Each type of network has its plusses and minuses.
Satellite phones work with either low earth orbit systems or much higher geosynchronous systems. Each type of network has its plusses and minuses.
Courtesy Iridium

Satellite phone systems work very differently depending on the technologies each company deploys. Some companies opt for geosynchronous satellites, while others use low Earth orbit (LEO) systems. Each configuration, or constellation, has its pros and cons.

Geosynchronous satellites (also called GEO orbit or high earth orbit satellites) follow the Earth as it spins, meaning that they pretty much remain in a fixed location in the sky. They maintain a high altitude orbit, at around 22,000 miles (35,000 kilometers), and they're always centered above the Earth's equator.

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These are huge, powerful satellites and just one of them can serve a large geographical area on the Earth's surface. With a constellation of only three or four satellites, a company may provide service for most of the globe. As such, these satellites are designed to handle large volumes of data, meaning they'll work not only for voice calls, but also for video streaming, file sharing, texting, television and much more. Inmarsat and Thuraya are two established companies that use geosynchronous configurations.

One downside of geosynchronous satellites is that their high orbits mean significant transmission delays of around 250 milliseconds one way, or a quarter-second round-trip. So when you're speaking to someone, you may have to wait for a few moments before they answer your questions. Or you may hear a disconcerting echo, which can be frustrating.

Also, their small numbers put these networks at somewhat greater risk for outages. When one satellite requires maintenance (or malfunctions), an entire section of the world may lose service until the issue is resolved. Because geosynchronous satellites hover mostly above the equator, they don't provide much coverage for the poles.

One of the biggest caveats to geosynchronous systems is related to size. To make a connection with these satellites you need a device that's roughly the size of a notebook computer; much of that bulk is comprised of a directional antenna. You also may need to calibrate the antenna and then point it towards the satellite in order to receive the best reception.

On the next page you'll read more about the perks and prices of picking a particular sat phone technology.

Leaping into LEO

LEO satellites have much lower orbits, at up to 930 miles (1,500km), and they're operated by companies like Globalstar and Iridium. If geosynchronous satellites are the gorillas of the industry, LEO satellites are the mosquitos. They're much smaller and lighter, and there are a whole lot more of them.

Because LEOs are so low in their orbits, a network might require as many as 60 satellites to provide coverage for most of the Earth. At any one time you may be within range of two or more of these satellites as they zoom around the planet at around 17,000 miles (27,359 kilometers) per hour, completing an entire orbit in around two hours.

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Those low, fast orbits mean reliable service for much of the planet. So, if you're a scientist with an emergency in Antarctica, you'll rely on LEO satellites for communications.

LEOs are known for having superior call quality, lower delays (of only around 50 milliseconds one way) and greater dependability. They also need less battery power, so they don't suck as much juice as a geosynchronous-capable terminal. However, their data transmission speeds (at around only 9,600 bits per second) are much slower than geosynchronous systems. Suffice it to say you won't be watching YouTube if you're on an LEO network.

But LEOs have a major selling point in that they don't require a large antenna on your phone. Instead, these phones might be just a bit bigger than a typical smartphone, meaning they're pocket portable.

Whether you're using a geosynchronous or LEO system, for the best service, your phone needs a line-of-sight view to the satellite. So if you're indoors, you may need to step outside to make a call.

With a geosynchronous constellation, particularly, line of sight can be a problem, especially if you're in a dense forest or mountainous area with limited line of sight. With a LEO constellation, though, you're bound to have repeated opportunities to connect as numerous satellites zip by overhead, although your window of opportunity may be limited to a few minutes at a time.

So what if you're in an area of poor reception and someone on the other side of the planet desperately needs to contact you? In that case, as your signal waxes and wanes, you'll receive a pager alert indicating that someone wants you to call. Then you can move to a location with better reception in order to make the connection.

If you're in a scary, war-riddled country, though, you want to take every precaution and stay alert to danger. Keep reading and you'll see why in some places using a sat phone can be harmful to your health.

Sat Phone Smackdown

In a few countries, just having a sat phone on your person can get you into a whole lot of trouble.
In a few countries, just having a sat phone on your person can get you into a whole lot of trouble.
Courtesy TerreStar

By their very nature, satellite phones adhere to a different set of rules, not just technologically, but politically, too. To that end, governments that prefer to control the communications options of their citizens are not fond of satellite phones.

In peacetime, many government agencies can easily monitor cell phone communications. And in times of strife, those same organizations can power down cell towers to disrupt or destroy wireless communications; the same rules apply to many forms of Internet service.

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But sat phones are different. Because sat phone skip ground-based communications towers, they aren't as easy to manipulate or monitor as cell phones. A determined regime may attempt to jam sat phone signals, but even these efforts may be only temporarily effective.

Thus, oppressive governments actually make it illegal to possess a sat phone. They can't stop the technology. But they can make you afraid to use it.

In Bangladesh, for example, a court sentenced Anup Chetia to prison for possession of a sat phone, which he was using for a range of anti-government activities [source: Hossain]. In North Korea, you can now use a (government-issued, and thus monitored) cell phone, but sat phones are strictly prohibited [source: Lee].

As the Arab Spring spread to Syria, which subsequently sank into civil war, the government severed many cell and Internet communications. This forced rebels and activists to use sat phones. In fact, there was such a large spike in demand for sat phones that the region's main service provider, Thuraya, reported shortages of handsets [source: Hamid].

Using a sat phone might mean free-roaming calling capabilities in a war zone. But it doesn't mean you're invisible. Even if they can't shut down your calls, many governments can track sat phone signal locations unless your system uses signal-scrambling features.

Sat phones aren't vulnerable only to human interruption. They're also subject to the whims of Mother Nature. As with cell phones and other radio-based communications, sat phones may be rendered useless in the face of massive solar flares and other natural phenomena.

On the next page you'll see that solar flares and military juntas might be the last of your sat phone concerns. Instead, these phones might leave your bank account hurting.

Sat Phones Flatten Wallets

Launching and maintaining satellite networks is expensive business. That’s why sat phone airtime costs an arm and leg (and maybe another arm).
Launching and maintaining satellite networks is expensive business. That’s why sat phone airtime costs an arm and leg (and maybe another arm).
Courtesy TerreStar

Compared to their ubiquitous cell phone counterparts, sat phones are a fringe technology. As with so many exceptional devices, they are more costly to use than more pedestrian phones. Prices may vary substantially depending on whether your provider uses geostationary or LEO satellites.

Regardless of provider, the terminals and handsets are always more expensive than cell phones. In a time when many cell phone service providers give phones away for free, sat phones cost a minimum of a few hundred dollars. As of 2013, for a better-than-average LEO handset, you can easily drop around $1,000. For a briefcase-sized geosynchronous-compatible phone, you'll blow spend several thousand dollars.

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Yet that initial investment will likely be a drop in the proverbial bucket. Because to make calls, you'll spend a good chunk of money per minute. Prices vary greatly depending on the provider and who you're calling, but it's not uncommon to spend around $1 per minute and nearly the same for a single text message. Receiving calls is an even pricier proposition, especially if the call originates from a landline. In those situations, you may wind up paying several dollars per minute. That price jumps much, much higher if you're calling a phone in another satellite company's network.

Satellite company operators clearly understand that their services are much more expensive than a typical cell phone plan. That's why they often sell minutes as pre-paid plans. You're less likely to mindlessly run up bankruptcy-inducing bills if you've already spent that money in advance.

You may be able to dodge some calling fees by investing in a dual-mode sat phone. These phones are compatible with regular cell phone networks, and by default, they'll route your communications through them. But in times with you're out of cell tower range, the phone will switch to satellite mode, meaning you'll almost always have service.

Or, instead of jumping in by buying a phone, you can also consider a rental. You'll be able to rent a basic terminal or handset for just a few dollars a day. So, for shorter trips or when you're just trying out the service, rentals are a money-saving option.

Sky-high prices aside, sat phones fill a very noticeable gap in our age of omnipresent communications. Without them, many of the areas of the world would be unreachable by phone. And when you really need to make that call, there's no price too high to pay.

Author's Note

Satellite phone technology is currently red hot in some regions of the world -- most notably, areas of conflict and disaster where regular cell communication isn't possible. Still, the future of sat phones is at best rather murky. Constantly expanding cell coverage means former satellite-only customers have more ground-based (and thus, more affordable) options. Yet as sat phone networks get savvier and the world gets more technologically chaotic, you may find one day that a sat phone is the only thing between you and dead air.

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Sources

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