BROADBAND FOR ALL

With its higher bandwidth and faster data delivery, broadband is the obvious choice for the laptop owner. Leo Waldock reports on how to make the most of the technology and what you’ll need to get started

At first the Internet was regarded as a curiosity, but these days most of us consider it a necessity for email, work, online banking, checking cinema times and generally keeping up with the news. As Internet connection speeds have risen, the way that we use it has changed beyond all recognition. Take the example of checking the films that are showing at your local cinema. It takes about ten minutes to dig out the local newspaper and check the advert and around five minutes to phone the cinema. Alternatively, it takes about five minutes to make a dial-up Internet connection and burrow through the inevitable Flash animations to get the information that you want. By contrast a Broadband connection is permanently connected and will have the information you need in front of you in less than a minute.

In part, the increase in speed is thanks to faster processors that are able to decode web pages more quickly, but mainly it’s down to telephony. The Internet has been built on a telephone system that was only ever intended to carry voice traffic. This is POTS (Plain Old Telephone Service) and as technology goes, it’s very simple. Your telephone converts your voice signal (which is analogue) into an analogue electrical signal, and then passes it down twisted pair copper wire to the exchange. The signal passes through switching equipment to route the call correctly, and at the other end the signal is converted back into an audio signal by a second telephone.

Computers use digital signals of course, so for starters we have to add a modem (MOdulator/DEModulator) at each end to convert the analogue signal into a digital data stream. The modems need to do that awful ‘handshake’ thing to synchronise their signals and then we’re good to go, but we’re left with the question of the speed with which data can be transferred. An analogue signal has its bandwidth (its capacity to carry data) expressed as the difference between the highest and lowest frequency components of the signal. Voice traffic has a bandwidth of 3KHz while analogue TV uses about 6MHz (2000 times as much).

Digital signals are expressed in bits per second, so a 28.8Kbps modem can receive data at up to 28,800 bits per second. There are eight bits in a byte, so that is a maximum theoretical speed of 3.6KBps. Modems seemed to have hit the bandwidth limit of the regular phone line at33.6Kbps, and it was concluded that the absolute speed limit for a copper phone line was 35Kbps. This is called Shannon’s law, as Claude Shannon of AT&T postulated. The problem arises with the analogue conversions, or modulation, which slowed the whole process down. The answer lay in making the connection semi-digital.

At first there were two competing standards; x2 from US Robotics and K56 Flex from Rockwell, and naturally the two standards were incompatible. This was resolved in the V.90 standard for 56Kbps modems, which was updated in 2001 to theV.92 standard. The important thing here is thatV.90 and V.92 only offer increased speed between a modem and an ISP (Internet Service Provider) as the standards depend on the infrastructure that your ISP uses. These days, most of the global telecom system is digital, apart from the connection between subscribers and the telephone exchange, which is known as the ‘last mile’. This means that in most cases the only analogue-digital conversion happens at your modem, instead of the usual two or more conversions.

Most modems operate in full duplex mode, offering the same upload and download speed, and most of us can achieve a reliable 56Kbps connection speed which is usually only limited by the website that you are browsing and its level of traffic. The exception is where bandwidth is limited, and that tends to be in rural areas where a phone line is shared between a number of subscribers. This sharing has no effect on voice traffic as it has such low bandwidth requirements, but you may find that your modem tops out at 33.6Kbps if you live on an isolated moor in Devon. In essence, if the phone companies stopped treating your computer as a pseudo-telephone then we could instantly get away from the analogue part of this equation and move to a fully digital connection.

DIGITAL SWITCH
We have had this option for many years – it’s called ISDN (Integrated Services Digital Network). In the past, it used to cost a small fortune. ISDN is a 64Kbps digital phone line, which offers the advantage of a much faster connect time as you don’t have to suffer the initial analogue handshake. In the past you had to choose between ISDN and double ISDN, but these days you can expect any ISDN service to actually offer you double ISDN, which is two lines that work in tandem, to give a total of128Kbps. The Telcos have had to make this move to give ISDN a chance of remaining attractive compared to DSL (Digital Subscriber Line) or ADSL (Asymmetrical DSL). However, ISDN does have an advantage over DSL as it isn’t too fussy about the quality of the phone line, so it is generally available, unlike DSL.

Both DSL and ISDN require that you live within 5.5km of the telephone exchange. The bandwidth offered by ISDN is split into channels that handle voice, fax and Internet access simultaneously, so it offers a decent service, except that it is relatively slow by modern standards and is also quite expensive. BT Home Highway (double ISDN) has a £75line conversion charge and costs £25 per month, with a UK call charge of 3p per minute and 6p at evenings and weekends. That package is skewed to business users, and the Anytime plan would suit most of us at £47 per month with no further charge for UK calls so long as the call is under one hour. Pay an extra £17 a month (taking the total to £64) and you can surf the Internet for up to 150 hours at a time.

BROADBAND CHOICE
The vast majority of us who want Broadband over a phone line opt for DSL, as it is both cheaper and faster than ISDN. Essentially, DSLi s a super-fast connection over a regular phone line. This is provided your exchange is DSL enabled, your phone line is of suitable quality and you live within 5.5km of the nearest digital exchange. In the UK we talk about ADSL as that is the version of DSL that we are offered. Download speeds can be as high as 1.6Mbps, while upload speeds are limited to 640Kbps, which is less than half of the download speed.

As most of us download files, browse websites and receive emails, this arrangement is quite satisfactory, although it can be a pain when we have to distribute large files, such as photos or movies. The two key features of Broadband are an always-on connection and a high-speed connection. Double ISDN runs at 128Kbps and a typical Broadband connection is faster than500Kbps – so the official definition of Broadband has been accepted as a connection that is faster than 256Kbps. We don’t mind how the Broadband connects your computer to your ISP – so wireless, fibre optic cable or regular copper wire all count as Broadband. Actually, there’s a third feature, which is that Broadband doesn’t hog the entire bandwidth so you can still make phone calls or watch cable TV while you’re connected to the Internet.

This is achieved by dividing the bandwidth into channels to make maximum use of the available spectrum, which is the major strength of digital technology compared to analogue. Converting your analogue phone to ADSL is relatively easy, however, you will run into the power of BT at every turn. Start by visitingwww.btwholesale.com to get an accurate picture of ADSL availability in your area, either by checking your phone number or your postcode. Assuming that ADSL is available for your area, you then need to decide on an ISP, but that strictly depends on your location, although you can find some guidance here:www.adslguide.org.uk. BT owns all the copper phone lines and claims that it releases them to other ISPs just as fast as it can convert them to ADSL. However, it is a fact that the vast majority of ADSL customers in the UK belong to BT. You may recall that BT gutted its exchanges in the late eighties to convert them all to digital, so the most common problem is that subscribers live too far from their exchange for ADSL to work.

Despite that rough rule of thumb, it takes about ten days to process your ADSL order as a series of programs need to run line checks. Then if all is well, an engineer has to visit the exchange to plug in a black box on your line. You receive an ADSL modem and two micro-filters in the mail, which you plug into your computer and phone line sockets respectively, and you’re then connected at ten times your previous dial-up speed. Well, that’s the theory at least.