Phone networks in the sky

However extensively cellular networks manage to roll out their coverage, there will be areas not covered: unpopulated and remote regions, oceans and places where politics or economics rule out normal coverage.

Geostationary base stations

The alternative is satellite phones. These have been available for some years, using base stations built into geostationary satellites. The snags are that they need fairly powerful mobile transmitters to reach the base, and large antennas which have to be accurately aimed at the satellite's position in the sky.

Typically, a satellite phone antenna is something like a large dish, attached to a ship's superstructure or the back of a TV crew's truck, and attached to a steering mechanism which keeps it aligned as the ship rolls, pitches, yaws and turns. If the ship goes a long distance, the dish has to be re-targetted at a different satellite, which normally involves a specialist technician.

Such an arrangement is not really suitable for a handportable phone. Although satellite phones can be built into a briefcase form factor, with the antenna built into the lid, the user has to set it up for a call, aiming it at the correct bit of sky. This means that unexpected incoming calls are unlikely to succeed, but is standard issue to news reporters in remote parts of the globe.

The other problem is the call cost. You are exclusively using a channel in a very expensive system, and you have to pay for it! Typically, you can expect to pay around £5 per minute for calls to or from a satellite phone. Data is available, but not at high speeds. Technological advances are bringing costs down and performance up, but this will never be a mass-market solution

Orbiting base stations

To get around these snags, a new generation of satellite phones was around for a year or two. The big difference is that they used a larger number of satellites in much lower orbit, so that dedicated dish antennas are not needed, and (large-ish) handheld portable phones are available.

This system is called Iridium, the name of an element with a number in the periodic table that matched the number of satellites planned for the system. In fact fewer satellites were used than originally planned, but the name stuck, possibly because Dysprosium was a less appealing name!

Because the satellites are lower, their orbits can't be geostationary (there is only one altitude where you can be geostationary). This means that the satellites have to transfer calls from one another. The handoff system is supposed to work in a similar fashion to GSM.

The snag

Unfortunately, there were technical problems with Iridium, causing poor speech quality and dropped calls, and it proved almost impossible to obtain Iridium handsets, even at £2,000 each. It has not been a financial success, and looks to be one of technology's great flops. It remains alive because the US military find it useful enough to be worth footing the bills.

Another company, backed by Bill Gates (of Microsoft fame), has a similar system called Globalstar. Possibly they will learn from Iridium difficulties. Unfortunately, its coverage is reportedly patchy, and the handsets for it are US-style AMPS/CDMA/Globalstar units, so have little appeal for non-americans.

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