Moving sky networks closer

New technology in the form of medium earth-orbit (MEO) and low earth-orbit (LEO) satellites is opening doors for companies such as Iridium LLC to build sky networks for voice and data.

“The concept of Iridium is to provide the ability for people to roam all over the world and be able to communicate with a handheld device, anywhere, any time,” said Fred Christensen, general manager of operations and business development for Iridium Canada in Mississauga, Ont.

Iridium phones and pagers are targeted at travelling executives as well as sectors where terrestrial infrastructures can’t reach, such as far north logging and mining, maritime communication, or search and rescue operations, Christensen said.

Bob Egan, research director with Gartner Group Inc. in Stamford, Conn., noted when cell phones first came out, because of their size and cost, they were targeted at the same sorts of users.

“Iridium is expensive, but people bought cell phones when they were expensive…[The Iridium phone] is big, it’s bulky, it’s not as sturdy as it could be…They will get smaller, they will get lighter, and they will get more reliable,” Egan said.

Pricing is set by Iridium’s resellers, but Christensen said the phones are approximately $5,000 and the pagers are around $800. Phone usage depends on the location and destination of the call, ranging from $2.50 to $12 per minute, while the pagers have a monthly flat fee of about $180, he said.

But Iridium has advantages over cellular, such as having the same number anywhere on the planet, Christensen said. He explained Iridium and other satellite phone developers have been assigned the country code of 881 and then fourth digits specific to the company — 6 and 7 for Iridium. Then users have an eight-digit number specific to their phones that does not change with current location.

Iridium has a constellation of 66 satellites about 780 kilometres above the earth’s surface, which Christensen said covers every inch of the world. There are six north-south orbiting planes with 11 satellites in each orbit. The earth turns inside the constellation, so there is also an east-west drift. Christensen said it takes about 11 minutes for a satellite to pass overhead and then hand the call off to the next satellite, all of which is done transparently to the user.

“The satellites have switching capabilities onboard that allows them to hand the call off to another satellite in the constellation through inter-satellite links,” Christensen explained.

“If you were in China calling North America, your actual voice path would go up to the satellite nearest you in China, then (be) linked through the other satellites to come over to the North American continent, then brought down to the ground.”

The North American ground point is in Tempe, Ariz. From there, the call is put through the regular phone network to its destination. Calls to Iridium users work the same in reverse, Christensen said. The Iridium paging service follows the same path.

Egan warned that Iridium phone conversations can be tapped into. “Iridium is reasonably secure, but don’t say anything over a cellular phone or put it in e-mail and/or over a satellite system that you don’t want known,” Egan said.