x Abu Dhabi, UAESunday 23 July 2017

Satellite to pull a fast one on internet

Abu Dhabi's second satellite, scheduled to launch this month, will provide online users in the UAE and the region with superfast connections courtesy of technical trickery.

DUBAI // Sometime this month a rocket will blast off from a launch pad in Kazakhstan, carrying with it Abu Dhabi's second satellite.

Once in place, thousands of miles above the earth, the probe - Yahsat 1B - will spend its days indulging in a cheeky fib designed to deliver superfast internet to the UAE and elsewhere in the region.

The satellite, which at more than six tonnes is the heaviest yet to be built in Europe, has been undergoing testing in Toulouse, France, for more than a year to ensure it withstands the rigours of the launch.

It is currently at the Baikonur Cosmodrome in Kazakhstan, undergoing further testing before being launched on an LS Proton Breeze M rocket.

Unlike most broadband satellites, which tend to be in low-earth orbit, often no more than 620 miles up, Y1B will be released into a geostationary orbit 23,000 miles above the earth - the same altitude as its older brother Y1A, which was launched last April.

That means it will permanently be in the same point in the sky, making it easy for earthbound users to fix on, and so giving a much better data transfer rate than low orbit satellites.

It raises a problem, too.

Low-earth orbit satellites are by definition much closer, so the data they transfer has only a few hundred miles to travel. But put a satellite in a geostationary orbit, and you add more than 64,000 kilometres to the data's journey. And longer journeys take time.

"The laws of physics are still intact," said Soheil Mehrabanzad, the assistant vice president for the Middle East and Africa region at Hughes Network Systems, the US company that will operate Yahsat 1B.

"But we have embedded into the system a number of techniques for accelerating the connection. From a user perspective it doesn't feel at all like it's going over a satellite."

In a typical transfer - the round trip between a home user, the satellite and the remote site, and back again - the data travels something like 92,000 miles.

That journey takes around a second with some older satellites. Mr Mehrabanzad is hoping Yahsat 1B will halve that, with a latency of just 540 milliseconds. That is still far slower even than dial-up modems, which deliver latency of less than a quarter of a second.

Mr Mehrabanzad insists latency will not be an issue for normal users. More important, he said, is the data-transfer rate, which should be well beyond what can be achieved with current terrestrial services.

It will achieve that thanks to a sneaky trick known as TCP spoofing. TCP, or transmission control protocol, is what normally determines how fast data is pulled down the wire.

It is a system of receipts; when a packet of data arrives at its destination, a receipt is generated and sent back to the sender.

That way, the computer server sending data knows it has arrived, and all is well with the connection. If it doesn't get a receipt, it sends the data again, more slowly.

But the system runs into problems when there is a lot of latency. It looks to the server as if it is dealing with a very thin "pipe", and slows the data down accordingly. In reality, the "pipe" is quite fat, but very long. And that means the satellite needs to fool the rest of the internet into sending data faster.

So it sends fake - "spoof" - receipts that arrive back at the server near-instantaneously. They kid the server into "thinking" its data has been received long before it actually has, and so into sending the next packet of data down the pipe much sooner than it otherwise would.

This trick, said Mr Mehrabanzad, has allowed the time lags and silences that have traditionally been the bane of satellite phone calls to be eliminated. "Satellites have been modified and improved," he said. "With voice over IP calls in particular, you don't sense that it's going over satellite."

Hughes has been testing the system on Y1A. The older satellite uses two microwave bands, "Ku" and "Ka".

The Ku band, which is between 12 and 18 gigahertz, is used mostly for television transmissions, while the higher-frequency Ka band, between 26.5 and 40GHz, is used for two-way data - including internet services.

On Y1A, most of the Ka band is used by the military, as one of Y1B's two Ka bands will be. The other will carry the Yahclick broadband internet service, which will be offered to users in 27 countries in the region.

And the signs are promising. "We are very impressed by the quickness of the service we are getting," said Tareq Abdul Raheem Al Hosani, Yahsat's chief executive.

"Now we are ready to make it available commercially."

He expects data speeds of up to 80 megabits a second to be possible - more than twice the speed of the fastest connection currently available to UAE users.

There will be download caps, though, of up to 30 gigabytes a month, which will be split into days to make it easier to manage.

It is hoped the service will provide a lifeline to many in parts of south-west Asia and Africa, as well as areas of the UAE where fibre broadband is not yet available.

"We are targeting emerging markets," Mr Al Hosani said. "Some countries don't have the ground fibre network everywhere. Satellite broadband is a gap filler for them at the moment."

It will also act as a fallback for the UAE if its undersea fibre optic cables are damaged.

"The capacity we can provide is huge," he added.

mcroucher@thenational.ae