By Mike Locke
Evolution of satellite systems
Networks and businesses have been using satellites for data for as long as there has been an internet. In fact, the first ever internet connection into the UK was carried over the Atlantic by satellite – albeit at only 9kbps.
Several things have changed in the intervening four decades: speeds have increased to tens and hundreds of megabits per second, and costs have come down dramatically. Today, it’s possible to buy your own two-way satellite connection for less than £300 and subscribe for £25 per month. That means that “proper” broadband is now accessible to everyone in the UK no matter how remote from their telephone exchange or fibre backbone.
The frequencies used by satellite, both for data and for television, have also risen from C-band to Ku-band and some now in Ka-band. (Definitions vary but in a satellite context, C-band is around 3.6-7GHz, Ku in Europe is usually taken as 10.6GHz – 12.75GHz and Ka is above 26.5GHz). The higher frequencies are made available as technology develops and they are needed because services soon fill up frequency bands as they are made available.
The move to digital systems for television saw a whole new set of standards developed under the umbrella of Digital Video Broadcasting (DVB). Digital TV is, obviously, a digital transmission system and DVB technology has been adapted to carry internet data as well as digital TV data. This means a satellite broadband can share much of the same infrastructure as a satellite TV system and also the customer equipment can share many of the same components and software.
The commonality of technologies has enabled a much lower cost base for many satellite internet networks and hence today most satellite broadband systems aimed at consumers will be largely based on DVB.
A satellite network has two main components: the satellite itself in orbit and the dishes and systems back on earth – the so-called “space segment” and “ground segment”. For a TV system, the ground segment will consist of the operations systems, which control the satellites in flight, the uplinks that send the TV signals up to the satellites and the various links to receive the TV broadcasts from the broadcasters; plus, of course, the dish and satellite TV receiver at the viewer’s house.
Add the ability for the customer to transmit as well as receive, driven by a suitable satmodem, and link the operations hub to the internet backbone and that, in simple terms, is a satellite broadband network.
Until the advent of DVB-based systems, the customer premise equipment (CPE) was quite expensive and needed a 1 or 2-metre dish, relatively high power transmitter and a specialist satmodem. Usually, it would take a two-person team half a day or more to install and setup. These expensive installations are still used in certain applications, but most consumer satellite broadband systems nowadays use a low power (no more than 2W) transmitter and a dish no more than 75cm in diameter. The CPE is easy to install by a single person and quick to get going with automatic commissioning and a simple Ethernet connection to the computer or router.
The main advantage of satellite broadband is that it is available just about anywhere you can see the southern sky (it has to be the southern sky as geo-stationary satellites orbit the Earth around the Equator). That being the case, satellites have long been used for communications in remote locations such as oil rigs where running cables was simply impractical or prohibitively expensive. Other networks use satellites where they want direct connections or just don’t want to share infrastructure, perhaps for security: National Lottery terminals or car dealerships being common examples.
There is still a trade-off between price and availability as the space segment, and hence the bandwidth carried by it, is relatively expensive. Terrestrial broadband is cheaper to use once the cable or phone line has been laid. However, since laying new cable can cost the operator up to £100 per metre, a satellite installation may have a lower upfront cost, plus it’s quicker to install.
Speeds over satellite are typically 4–10Mbps, but can be up to 100Mbps. At one of the mature satellite positions such as ASTRA 3 at 28.2ªE, there is more than 4GBs of aggregate capacity available, with more to come as compression technology continues to improve.
Because of the economics of satellite, it will never be as cheap as a connection to an existing network a few kilometres away from the exchange. However, recent advances mean that a perfectly reasonable speed of 1–10Mbps can be had for around £20–£25 per month.
The fundamental advantage of satellite broadband is that you can have it installed within a few days and get online with reasonable speeds just a little more expensive than the UK average. If you’re in a location where terrestrial broadband still hasn’t arrived, satellite can connect you straight away.
Broadband is not the only service that can be delivered by satellite; the obvious service that can be received on the same dish, as long as your dish is pointed at the right satellite, is digital TV like BSkyB and Freesat. Some providers can also offer a VOIP service with a UK phone number.
All internet services have issues with contention and resource restrictions. That’s in the nature of shared access services and can only be avoided by guaranteed – and expensive – committed information rate or leased line services. Satellite broadband usually has tighter restrictions than terrestrial services simply because of the higher cost of providing the bandwidth.
However, users have the choice of different packages to match their requirements as closely and as economically as possible. For example, there are packages with unlimited data but a gradual throttle for overuse; packages with no throttle and a set amount of data each month; packages with a limit during the day but unlimited overnight downloads and so on. The important point is that the user needs to take a little more care to choose and make effective use of the package that’s right for them.
Satellite services are based in different countries and so it is important to check that the service you choose has a UK IP address. That means you will automatically get the UK version of websites such as Google.co.uk and not be excluded from country-specific services such as BBC iPlayer.
And, of course, there is latency. Latency is the “round-trip” time for a packet of data to go from the user over the connection to the computer being visited and then back to the user again. Since the satellite is in orbit some 36,000km high, the signal takes just over one tenth of a second to reach it and another tenth to come back to earth again. Even at the speed of light this introduces a minimum time of 440 milliseconds into any satellite connection.
Some satellite systems use acceleration techniques which wait for all the webpage to be assembled and sent across as a single transmission rather than requesting one file at a time – so it takes longer to start the download but finishes sooner.
For most applications, latency is not a major issue. But for applications such as real-time gaming where half a second is the difference between being shot and diving into cover, then satellite will suffer because of the latency. Some virtual private network (VPN) systems can also have problems. The VPN prevents satellite system software from altering the private data, so a VPN cannot benefit from satellite system acceleration.
Other satellite systems
This brief article has restricted itself to services carried on geostationary satellites direct to the consumer. There are other services on low Earth orbit (LEO) systems but these are significantly more expensive both for the equipment and the data.
In the past, due to the cost of the satellite terminal, it used to be economic to install a single terminal in a community to act as a hub and then use local connectivity such as Wi-Fi to share the satellite connection to homes and businesses. However, now that the CPE is so cheap and easy to install, the benefits of the communal approach are outweighed by the complexity. It is much simpler and cheaper to have a dish and satmodem each with no need to share any connection.
Satellite broadband services delivered by geostationary satellites have truly now come of age. They offer a good solution, ubiquitous and reasonably priced. They make no claim for the latest superfast 100MBs speeds at a rock-bottom price: for that you will either have to wait a while for a new technology to deliver or move house. On the other hand, if you like where you live or work and want to get connected today, then satellite will deliver.