|This page answers some basic questions about broadband Internet connection. Click on any menu item to find that section of the page:|
What is broadband? (includes explanations of the different types of broadband services)
What is wireless broadband?
Who can get it and how? (includes some discussion of the merits of the different methods)
ADSL versus high performance broadband
Some jargon terms explained
What is broadband?
At present there are six main ways that consumers and businesses can access the Internet from their homes:
- Conventional ("dial up") modem running at up to 56 kilobits per second (kbps - see "jargon terms"). This is how the majority of households and many small companies have accessed the Internet prior to the availability of broadband services. Consumer PCs usually come with a built-in 56kbps modem. Whenever you want to use the Internet there is a slow connection process as the computer dials the access number and your computer and the Internet service provider's (ISP's) computer exchange details. The ISP's expectation is that you will 'dial up' from time to time and then disconnect when you have finished a particular task. Although there are 'unmetered' services (with no 'per minute' charge) you are not expected to stay online conintinuously, and most ISPs have a contract clause that allows them to disconnect you if you do stay online for very long periods.
- ISDN - Integrated Services Digital Network . This is used by both consumers (BT's consumer service is called "Home Highway") and companies. It provides two connections, each running at 64kbps. With the appropriate technology and Internet service you can work with both connections together, providing up to 128kbps. Although the 68kbps is not much faster than a 56kbps modem, connection time is reduced and overall better performance is achieved because the connection is "digital" throughout.
- Cable - this generally uses the cable that provides cable TV. Most cable TV providers also offer voice phone service and Internet connection. Their standard Internet connection may not be broadband, you need to enquire specifically about that. You also need to check what is the rated performance of their standard 'broadband' service, since this is not always clear from their main advertising. Cable companies do not necessarily make broadband available throughout their cabled-up areas. NTL provides a consumer broadband service in Andover, and I have used this service in my constituency office since mid-2002.
- ADSL - Asymmetric Digital Subscriber Line - this is the service promoted by most ISPs as 'broadband. It enables your Internet connection to run across an ordinary phone line at much higher speeds. Asymmetric means that the service is faster in downloading (information coming from the Internet to your PC) than uploading (from your PC into the Internet). Standard consumer ADSL runs at 512 kbps "down" and 256 kbps "up". Business ADSL services can be provided at much higher performance levels than this. See the "jargon" section below for more about ADSL. Again you need to check what performance you are being offered, since some ISPs now promote 'introductory' services that run at 256kbps download or even 150 kbps. Although these are advertised as 'up to X times faster than dial up' most people would not regard anything below 512/256 as giving 'the broadband experience', though the 'always on' characteristic will be and feel different from a dial-up service. I've found that some ISPs offering cut-price ADSL make it very difficult to find out exactly what are the performance standards you are signing up for.
- Satellite - you install a satellite dish and the pages you want are sent by satellite to your computer at a faster speed than an ordinary dial up connection. You may also have a conventional landline connection to upload pages and to tell the satellite company what pages to send to you. On an individual basis this costs more than ADSL or cable to install and may cost more to run. Some companies have started to provide "two way" satellite services. At least one company, Amariska, is proposing a community solution that uses satellite to provide the "backhaul" (see "jargon", below), with individual homes and businesses connected by local wired or wireless methods. An issue affecting some types of applications that may not work well with satellite access is "latency" - the time taken for your signal to travel to and from the distant satellite - see "jargon" below.
- "Local wireless", which is becoming available in some areas, and is further explained below, but this is not something an individual user can simply order and install, unless you are in one of the relatively few areas where a community wireles scheme is already in operation. Unless you are in an existing cable TV area the main and most desirable current service is ADSL, which you can order from BT or from many other Internet services providers. Most of these are re-selling the BT service, but there are companies that have installed their own ADSL equipment in BT's exchanges.
- Powerline broadband delivers broadband across the existing electricity distribution network. This is explained further below but is not yet in general use.
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What is wireless broadband?
A few years ago Government auctioned licenses to use some radio frequencies to provide broadband performance to mobile phones, a facility called "third generation" or 3G mobile. The Chancellor of the Exchequer extracted some £20 billions from the mobile phone industry through this auction, an amount that may have seemed reasonable to some people at the height of the "dot com" boom but in retrospect was a damaging tax that slowed down deployment of the technology.
Other parts of the radio spectrum can be used to provide "localised" wireless Internet connection. One part of this can be used within the home to connect your keyboard to your PC; another provides Internet connection around "hot spots" in places like airports and railway stations; a third variation can provide "local community access". Local community wireless is being used in some countries to deliver broadband service in areas out of reach of ADSL and could be a good solution for some of our rural areas. A useful Guide to Wireless Broadband has been published by the UK Broadband Task Force. Though aimed at the public sector the content is very widely applicable. Note that the file is almost 4Mb, since it includes a lot of more general background before getting down to the wireless aspects!
In the UK there are now several communities that have 'pulled in' a community wireless solution, often with some support from Government via the regional development agencies. Notably we have one such model in my own constituency at http://www.kingsclere.net/broadband. Worthy of note is the fact that with ADSL a message from one house to the house next door travels across the wider Internet, while a community wireless network can be configured so that local traffic remains within the community. This offers potential for interesting 'in-the-community' applications. Some people think that our future networking will very widely include local community networks as well as the generic Internet.
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Powerline Communications, also called Broadband over Power Line (BPL) uses the electricity supply lines to provide broadband connections. In principle it could be used to deliver broadband to any home connected to the electricity grid, making it attractive as a solution for rural broadband, since it removes the need to lay additional cables to each home. Trials of this are under way in the UK, notably in some areas supported by Scottish Enterprise, see http://www.hydro.co.uk/broadband/. One of the pilot areas being evaluated by the supplier, (Scottish Hydro-Electric) is Winchester, near my own constituency.
Return to topics listADSL versus high performance broadband
Who can get it and how?
Most if not all homes (and businesses) can get conventional (dial up) modem service using an existing phone line. Line noise is occasionally a problem but in general BT (or your alternative supplier of phone services) can be expected to sort this out. Most - but not all - homes can also get ISDN. If you are in an area that has cable TV service, you can probably get a slow Internet connection (similar to the speed of a dial up modem) from the cable supplier, and you may be able to get their faster "cable modem" service.
Cable is only available if your home or office area are in a Cable TV area, and if the Cable company is offering a cable modem service in your street. It provides a good service at a reasonable cost - if it's available locally. It provides the "always on" facility (see below). There is little chance of new cable networks being laid in villages, small towns and rural areas in the foreseeable future.
ADSL is a different kettle of fish. This is a dramatically better service than either conventional dial up modem or ISDN. First it runs much faster. Second it allows you to have what to all intents and purposes seems like an "always on" Internet connection - it removes the irritating wait while the modem dials the line, the service provider's system answers, user name and password are checked and - dependent on the supplier - there can be a further delay while the network connection is established. ISDN does this a lot quicker than a dial up modem, but even that can entail a quite noticeable delay. In comparison, ADSL is almost instantaneous - in effect you are permanently connected. This can make a big difference to how we use the net. Also, ADSL is provided at a fixed monthly cost. This cost is higher than the charge for an ordinary phone-and-modem connection but is comparably in price to an "unmetered Internet service" using ISDN - good value when the speed and performance are taken into account. The bad news is that we can't all get ADSL. There are two reasons for this:
1. BT has "ADSL-enabled" some of their telephone exchanges, but not all;
2. The ADSL technology means that even if your local exchange is enabled, you still might not be able to get ADSL service dependent on the length and quality of the connection between your home or office and the exchange. Typically ADSL service can be expected to be excellent within 3 kilometres of an exchange but not available at all if you are more than 5 kilometres from the exchange. Between 3km and 5km BT may or may not offer the service based on its technical judgement about the line quality. The distance is determined by the length of the line between you and the exchange, not "as the crow flies".
Satellite broadband can be used anywhere in the UK provided you have "a clear and unobstructed view of the sky to the south". It requires a new satellite dish, which in some cases may require planning consent.
Some suppliers are promoting Wireless broadband in metropolitan areas, where they are competing on a commercial basis with other options, but in rural areas it is typically implemented as 'community wireless', with support from either the local authority or the regional development agency, or both.
All this is most frustrating to those of us who see "broadband" advertised, try to buy it, and then are told they are not able to connect! I am also concerned about the extent to which small local communities have to put so much effort into securing a service the government regards as essential to our future economy, and for which city people and companies get better performance and competing suppliers with no local effort at all.
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One issue that has had too little public discussion is the way ADSL is promoted and marketed as "broadband" without making clear its limitations. When enthusiasts talk about the benefits we will get from broadband, many of the most attractive "applications" will require much higher performance than consumers experience when they sign up for 'broadband'. Some suppliers sell a 'low cost' broadband service that is no faster than can be had from ISDN. Even 'standard' consumer ADSL offers upload speeds at only up to 256 kilobits pers second (see jargon terms below). The Government's main advisory body, the Broadband Stakeholders Group, has warned that "there is a danger of over-promising the speed of [consumer ADSL] broadband, which is inclined to raise expectations and leave adopters disappointed". At present there are no plans to establish a national high performance broadband network for general use in the UK, but this issue should receive wider attention now that ADSL is expected to reach almost all exchanges. The Broadband Stakeholders' Group recently (2004) coined the term "broaderband" as a slicker way of referring to higher performance networking.
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Some jargon terms
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- Connection speeds - kbps, megabits, gigabits etc
- The whole broadband debate is about connection speeds - what kind of performance we now and in the future. A "56 kbps modem" (sometimes shortened to a "56k modem" has a rated speed of 56 kilobits per second - 56,000 bits. The way computers store and transmit data, each character (a, b, 5, H etc) takes one "byte", made up of eight "bits". So if it were running at its full rated speed a 56k modem would transmit 560,000 divided by eight or 7,000 characters per second - around an A4 typed page. The photographs we take with a digital camera can be take one megabyte or more to store and transmit (million bytes) - a one megabyte picture means 8,000,000 bits divided by 56,000 bits or between 2-3 minutes to transmit. However for a moving picture (video) we obviously can't wait several minutes for each frame to arrive so we need very much faster transmission. You will have noticed that most video on web sites today appears in small windows and is of poor quality, since the modems most of us still use would simply present a series of still images one after another if we tried to send a TV channel in good quality and full screen. To give an idea of the speed of transmission links, standard Ethernet, which many offices use to link their computers, has a rated speed of 10 megabits per second, "fast Ethernet" at 100 Mbps - close to two thousand times the speed of that 56kbps modem. Standard consumer ADSL runs at 512kbps download (from the distant website to your desk), 256kbps upload (from your desk to the distant site). My experience suggests that for worthwhile video conferencing (an important application), at least one megabit per second each way is a reasonable start point. To run applications on a remote computer rather than locally (which offers considerable benefits for small firms), 2 megabits would be the start point.
- Elsewhere in these pages I've used "broadband" the way the Government and most suppliers use it - as if it means just "faster Internet service". However "broadband" is more strictly defined in terms of how the data is carried. It contrasts with "baseband" (0ne channel or user at a time) and "narrowband" (what we get with a 56 kbps modem). Broadband implies that a wide band of frequencies allows signals from different users to travel across the same path, so that - for example - when I send a short text message and you concurrently send a large picture file the network can give me more "bandwidth" and you less bandwidth. In principle we get high performance when we need it. But see "contention" below.
- Contention and contention ratios
- With our 56 kbps modem, when we call the Internet, our Internet service provider has to give us access to a modem to which our modem can connect. That's why we sometimes find that we can't get a connection - all the modems are busy. With ADSL, the supplier doesn't provide one "channel" to each user. Rather, the channel is shared among users who "contend" for bandwidth. If the channel has ten users who each want to send a 2 megabyte picture at the same time as each other, they each get one tenth of the channel's capacity. The maximum number of users a supplier will allocate to a channel is called the maximum "contention ratio". The higher the contention ratio the more the chance that you will encounter busy periods and slower performance. BT sets a 50:1 contention ratio for home users of ADSL (consumer service), and 20:1 for basic business services. You can buy a better contention ratio than this or even buy the rights to exclusive use of a channel - what we have known in the past as a leased line. Cable services operate in a similar way.
- Always on
- Because broadband shares one channel among a set of users, there is no need to dial up the connection - the channel simply sends and receives whenever your computer tells it to. This is how ADSL and cable broadband provide an "always on" service. Your computer is continuously connected to the broadband channel so there is no start-up or connection delay when you want to visit a website or send and receive mail. This is a major benefit of broadband.
- Latency is the time it takes for a signal to get from your computer to a distant server (a website say) and back. It's measured in milliseconds (thousandths of a second) and usually varies between less than 100 to several hundred. For many applications this isn't a problem but a high latency can seriously affect some highly interactive applications such as game playing. A satellite connection may well have a latency around 750, making it impractical for some uses.
- Some BT exchanges have had registration targets set that seem high in relations to the number of subscribers and this has sometimes been attributed to "high backhaul costs". Backhaul refers to the connection between your local exchange (or wireless or other network) and the wider Internet. One issue for the future will be the need to expand backhaul capacity as the numbers of local users increase and as we make more intensive use of the Internet. For example with a contention ratio of 50:1, if we all were to start downloading video files concurrently each of us would experience a very poor level of performance. Given the current flat rate approach to pricing and intense price competition we might expect to see new pricing models appear, giving more flexibility that today's rather simplistic (and steep) price point jumps between a notional 256k, 512k etc.
- More about ADSL, SDSL etc
- DSL stands for Digital Subscriber Line. It's a technology that allows transmission at high data speeds across the ordinary copper phone line that brings the normal phone service to most of our homes (unless you are on a cable service). DSL comes in many flavours. The one being promoted by BT and other suppliers, ADSL (Asymmetric Digital Subscriber Line) is so called because it offers a higher speed of connection from the network to our computers and a lower speed from our computers to the network. The rationale is that most of use "receive more than we send" - when we visit a website for example a very small packet of information from our PC causes the network to send a whole set of information from and about the distant site. The DSL forum (http://www.dslforum.org) says that ADSL can deliver "up to six megabits of data per second from the network to the customer", which is how BT and others can offer business ADSL services at quite high speeds. You may hear mention of RADSL - Rate Adaptive ADSL. The performance of DSL depends on two main factors - the quality of the copper wire, and the length of wire over which the signal travels between you and the exchange. RADSL can adapt to different line conditions by varying the data rate, and has enabled BT to extend the distance over which it can provide ADSL from some its exchanges. We are far from the end of the DSL story, which now includes HDSL (high data rate DSL) and SDSL (Synchronous DSL) - symmetric service at to 2.3 Mbps in both directions. Research continues!
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