Eutelsat Satellite To Bridge Broadband Digital Divide

KA-SAT – the world’s most advanced multi-spot satellite to date – is due to launch from Kazakhstan towards the end of November this year, aboard a Russian Proton rocket. eWEEK Europe UK travelled to Toulouse to see the final assembly stages of KA-SAT, which promises to go some way to solving Europe’s broadband connectivity problems.

Across Europe, roughly 10 percent of Internet subscribers can either not gain access to a DSL service at all, or are only able to achieve speeds of 1Mbps or less – too slow for decent on-demand quality video. One suggestion for overcoming this problem is to deliver broadband services from space, to help plug the holes in Europe’s Internet provision. However, limitations of bandwidth and broadcast capacity have proved a major stumbling block for engineers in the past.

“DSL-comparable” broadband

The KA-SAT satellite, commissioned by Eutelsat and built by EADS Astrium, has 82 independent beams which cover the UK and Europe with a mosaic of footprints. It is capable of a maximum of 40Mbps downstream and 20Mbps up, and is said to be able to serve Europe with a “DSL-comparable” broadband service, known as Tooway.

KA-SAT is only the second High Throughput broadband Satellite (HTS) in the world. The first – WildBlue, majority owned by ViaSat – serves US customers to very similar specifications. KA-SAT is built on ViaSat’s Surfbeam 2 protocol, and so uses ViaSat dishes, modems, provisioning and management equipment on the ground. However, KA-SAT is a new design, based on EADS Astrium’s existing ‘Eurostar E300s’ platform. Astrium claims this is the most complex satellite the company has ever built.

We got a look at the satellite in its clean room near Toulouse, just before the dishes and solar cells were added. When bolted on, they’ll supply 11kW of power and give the 5.8 tonne (at launch) satellite a ‘wingspan’ of 39 metres. Expressed in standard International satellite size units, without solar panels, it’s about the size of a large minibus.

The satellite’s basic job is to receive radio signals, amplify them and beam them back to the ground. Signals bounce off the four dishes into one of 82 fixed microwave horns, where they travel down an impressively complex mass of “waveguides” – hollow metal tubes that are to microwaves as glass fibres are to light.

KA-SAT’s chemical thruster (the large round object, behind the ring bolted onto the white construction trolley) burns three quarters of the 2.5 tonnes of fuel – Monomethylhydrazine (MMH) plus Nitrous Oxide (N2O) oxidiser – in order to reach geostationary orbit. Four electrically powered ion drive thrusters, (two can be seen sticking out on the right), expel small amounts of xenon plasma travelling extremely fast. They keep the satellite in the correct spot. There’s enough fuel on-board to do so for 16 years, with the remaining MMH/N2O also acting as backup.

Sharing bandwidth

Each of KA-SAT’s 82 beams delivers 250MHz of bandwidth. By reducing the spot size, each of the four frequencies can be re-used 20 times, expanding capacity to a total of 70GB/s of bandwidth, (or 850Mb/s per spot). Each spot supports around 2,500 users at a contention ratio of roughly 300:1 – i.e. every user’s 10Mb of bandwidth is shared with 300 others. For comparison, DSL’s typical contention ratio ranges from business packages at 20:1 to consumers at 50:1.

To bring the ratio closer to 30:1, users will be subject to a rolling one hour limit, in which they can download a maximum of 400MB, rather than the roughly 4GB per hour that a 10Mbps service could deliver. Once that 400MB limit is reached, speed drops to 1Mbps until the last hour’s use total drops below the 400MB threshold. There is also a monthly limit that, once reached, causes speeds to drop to a mere 128kbps until the end of the month, unless the user pays for additional 1GB or 2GB “tokens”.

In order to “commercially test the service and start playing with the tools”, Eutelsat has operated Tooway since January 2008, using four rented transponders on an alternative satellite – HotBird 6. The test service offers speeds of 3.6Mbps down and 512kbps up, and analysts estimate that it has around 25,000 subscribers. However, Eutelsat admits that the test has been operating at a loss.

Triple play service

When Tooway over KA-SAT launches in the second quarter of 2011, the service will initially offer speeds of 10Mbps down and 2Mbps up. Eutelsat is planning a “full” triple play service, including broadband phone and TV. The phone service will operate via VoIP but, with the satellite adding 600ms of latency (mostly due to the time taken for signals to travel to the satellite and back at the speed of light), expect a noticeable delay. Meanwhile, the small size of individual spots provides an interesting opportunity for local TV operators, who will be able to offer their own very localised broadcast and on-demand TV and radio services via IP.

Tooway contracts will range from €30 (£25) – for around 10GB per month – up to €100 for an “almost” all-you-can-eat package. Users will also have to pay a one-off fee of €350 for the self installable modem and dish. Final prices will depend on local operators and equipment subsidies.

It is thought that a single KA-SAT satellite will be able to serve, at maximum, around 5 percent of the section of the market that currently struggles to get DSL. EADS Astrium can build a second identical satellite in two years – substantially faster than the three years it took to design and build the first.

The UK has three spots, with two additional spots for Ireland. Existing TV from existing traditional broadcast satellites can also be incorporated by putting additional components on the user’s dish. Other markets being eyed-up by Eutelsat include mobile terminals, marine, electronic news gathering and mobile phone back-haul.

Although Eutelsat’s description of “DSL Comparable” is rather on the generous side when you consider the effects of 600ms of latency and the rolling download limit, where DSL is marginal or non-existent, KA-SAT is likely to be in demand.

Images courtesy of EADS Astrium and Eutelsat