AT&T Introduces Satellite-Enabled Smart Phone

crimeandpunishment writes "Here's one way to deal with spotty cell phone coverage: backstop the network on a satellite. AT&T is now selling its first satellite-enabled smart phone....which could be invaluable for boaters, forest rangers, and others who regularly leave regular cellular coverage areas. But the TerreStar Genus comes with a hefty price tag: $799.....and the data costs are as sky-high as the satellite....400 times more than a standard plan. It also has to have a clear view of the southern sky, which means it can only be used outdoors."

Re:DirecWay to the rescue!

[Gazoogleheimer]

because Iridium has -- for a bit over a decade.

Re:Texting

[hedwards]

It was for testing purposes, it's just that somebody later had the brilliant idea that people would pay for it.

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Re:DirecWay to the rescue!

[DarthBart]

The links just won't close. I don't have the exact numbers I'd need to do a link budget, but the Direcway links are engineered for a Ku link with a .9m dish on the ground and a 3-4m dish on the spacecraft, with the ground transmitting at 2-4 watts. The TerreStar satellite has an 18m dish on the satellite. That's a crapload more gain. TerreStar also uses a 2Ghz link which is also virtually unaffected by weather.

Also keep in mind that generating sufficient output power at Ku frequencies is extremely inefficient. A Direcway 4W BUC amplifier draws about 50 watts out of its power supply. I doubt your average cell phone's battery can tolerate that.

Re:uh no

[DarthBart]

Irridium has the advantage of being in low earth orbit versus Direcway's geosynchronous orbit. The path loss between a 250ish mile orbit and a 22,500 mile orbit is a hefty number of dB.

Assuming both systems At 2Ghz, it is 150dB at 250 miles and 190db at 22,500 miles. That 40db difference either has to be made up in raw transmit power at both ends or by using a 5.3m dish antenna.

Re:DirecWay to the rescue!

[hpa]

Iridium was more than just a way to market the technology ... they use low-orbit satellites which can provide a stronger signal and less lag. Unfortunately they spend $7,000,000,000 developing the technology, and the market just wasn't big enough for it.

Re:Anyone remember Iridium?

[Animats]

At the prices they pay for service, it might just make sense for them to buy out Iridium.

Essentially, they did. When Iridium was about to go under and the satellites were days from being de-orbited, DoD bought into the system at a bargain price. This turned out to be extremely useful once the US got entangled in Iraq and Afghanistan. Originally, DoD bought unlimited airtime for 10,000 users. Now they're past 100,000 DoD users. Iridium overall has about 360,000 users.

It's the thing to have if you need to communicate from Outer Nowhere. Works anywhere on the planet that you can see the sky. Airtime is about $1 to $2 a minute, and phones are about $1500. A roll-up solar panel is a common accessory. The typical user drives a HUMMV, a yacht, or a dogsled.

Re:uh no

[TheRaven64]

The loss isn't the only problem. There's also the question of latency. A geosynchronous orbit is an altitude of 36,000km above sea level at the equator, meaning that a signal has to go at least 72,000km there and back. To put that in perspective, that's just under 0.25 light seconds. This means that if both endpoints are directly under the satellite, the minimum latency is 0.25 seconds. In practical terms, encoding, decoding, and routing at the other end will add a bit, making it absolutely horrible for bidirectional communication. When you have a minimum of half a second round trip time, you're going to be constantly interrupting each other because you both start talking when you think there is a pause in the conversation and don't find out that there wasn't until half a second later.

Re:Yay this is awsome.

[tibit]

The "clear view" of sourthern sky is not necessarily so. Maybe if you were in a tropical forest, you'd have a problem. A standard pine forest does attenuate things, but pine needles aren't leaves. I've used Iridium for a bit and I've never ever had a situation where a satphone connection wouldn't work on the ground, but would work above the tops of the pines. Terrestar uses way better space segment, with comparatively colossal beamforming, so I'd expect it to work much better than Iridium did.

In the U.S., detached residential construction is basically relatively dry plywood with a wire or a pipe here and there, and with some bitumic shingles on the roof. Unless the shingles are the dealbreaker, I'd expect GENUS to work just fine indoors in a regular home. In commercial buildings -- sure, there will be problems, perhaps a bit more like there are with cellphone reception there.

As for cellphones in forests: assuming that the forest is well within a covered area, the trees should pose no problem. You always get attenuation from something. Trees, walls, rebar -- somehow my cellphone works just fine in a building with extruded corrugated steel roof (big seamless sections), and with reinforced concrete walls, at ground level.

Forests in remote areas simply may suffer from generally poor coverage, where the trees just make a marginal situation unworkable. But the trees aren't the main problem, the coverage is. And that's where GENUS steps in: you have poor land-based coverage, so it'll switch to the space segment.

I've been tracking Terrestar's PR quite closely, and they seem to be quite good at what they do. Their space segment is unique, and so far I have no reason to distrust their engineering. They cover their asses, but from what little experience I have, I'd expect GENUS to pretty much "just work" anywhere within the northern U.S., even in the middle of nowhere, Utah.