Teleworkers: the pipes are calling

For teleworkers the modem is now old hat as second generation connectivity comes to the mass market. Brian Clegg offers a guide...

For teleworkers the modem is now old hat as second generation connectivity comes to the mass market. Brian Clegg offers a guide to Internet connectivity

The right Internet connection technology has never been more important and, until recently, there was only one choice: a modulator/ demodulator, or modem. This, in case you had forgotten, takes the digital signals from a PC and converts them into the analogue waveforms that telephones use to carry sound. Compression enables modems to operate at a nominal 56 kilobits per second (kbps).

In practice, noise on the line reduces this speed. What is more, the 56kbps rate is only downstream - sending operates at 33.6kbps. However, now the telephone network is largely digital, the downstream mode keeps the incoming signal in this format throughout.

The obvious next step is to extend to a fully-digital connection, bringing in the second generation of connectivity.

The ISDN is a fully digital telephone line. The most common European configuration - ISDN2e - has two 64kbps channels (as well as these "B" channels there is "D" channel, which carries control and signal information). There is also a high-capacity 30 channel version.

Two ISDN channels can be "bonded" to produce a single 128kbps connection, although this is considered to be two separate calls for charging purposes.

While ISDN connection boxes are often called "modems", they are, in fact, closer in functionality to a Lan card. There is no modulation/demodulation, and the 64kbps data rate is consistently achieved.

ISDN operates as a conventional call and is charged by the second, but telephone companies have recently launched unmetered pricing, making ISDN more attractive for the teleworker.

BT's popular ISDN product Highway is a hybrid of ISDN plus two analogue lines, any two of which can be used simultaneously. This means traditional analogue equipment can be used in tandem with ISDN hardware and old phones or faxes don't have to be replaced. This option is fine for home workers or small branch offices, but not for installation in corporate buildings as it will not work through a private exchange and doesn't support Direct Dial In.

Until this year, ISDN was the most widely accessible and best technology available, but an outbreak of new possibilities is pushing potential connection speeds up. Cable operators are now introducing cable modems.

Again these are not true modems, being purely digital, but they operate asymmetrically like standard modems, typically receiving at 512kbps but sending at 128kbps. In the case of NTL, the transport medium is the fibre optic cable that carries the service's TV signals.

Satellites also offer high bandwidth broadcast but, as this is a one-way service requiring a modem for return communication, it is unsuitable for many business uses.

Soon, the most pervasive technology is likely to be Asymmetric Digital Subscriber Line (ADSL). Data can flow in with ADSL at up to 6megabits per second (mbps) but flows out at about 256kbps. The BT service is limiting early installations of ADSL, branded Openworld, to 512kbps, rising in steps to 2mbps.

This isn't as restrictive as it sounds, as most connectivity is asymmetric, with teleworkers pulling down much more information than is pushed up. ADSL is an "always-on" technology - particularly valuable as e-mails and Web updates arrive without the need to go looking for them.

However, the bandwidth is also contended - the resource of an ADSL link is shared between a number of users. If no one else is hitting the "pipe", data flows at the set maximum speed, but as more and more users come on-stream, the likelihood of each getting a full-speed service diminishes.

BT's domestic ADSL offering has up to 50 users sharing a pipe but this isn't too bad. There is still more capacity than any individual can take and this type of working tends to come in bursts, which makes the shared approach effective.

BT also claims that the size of the pipe can be increased to ensure that 512kbps is achievable. The business offering from BT, and that of ISPs offering business ADSL, such as Mistral Internet, has a maximum of 20 sharing.

An alternative that may be attractive if cable and ADSL are not available, or if flexibility of positioning is required, is high bandwidth wireless connectivity.

Tele2 currently covers an area from Reading to west London, and a number of isolated cities in the North and the Midlands. The company provides two modes of connection: a 9in roof-mounted aerial offering wireless DSL that is a contended and a symmetric service that offers guaranteed two-way connection at speeds from 256kbps to 1mbps.

In certain circumstances it is better to avoid the commercial networks and run in a leased line. This involves a considerable set-up charge and much higher running costs than ADSL.

Leased-line products are labelled Kilostream or Megastream (reflecting their capacity) in the UK. In the US, the Bell standard labelling of T1 for about 1.5mbps and T3 for 44mbps is used. In practice, such lines can be split, making it possible to have a "fractional T3", for example, to offer an intermediate rate.

The main advantage of a leased line is that there is no contention, making it sensible for high-flow, one-to-one connections, such as linking a large Lan into the Internet, but it is rarely necessary for the teleworker.

The options for connecting to the Internet have never been richer. Where once a remote connection meant a modem, now the home worker can connect at near-Lan speeds.

In this transition period, careful selection of technology to connect teleworkers is essential. But what's certain is that the least popular choice is likely to be a modem.

Making the connection

Faced with the need to provide a remote connection now, and not wanting to go to the expense of putting in a leased line, there is a simple choice to be made. If ADSL is available in your area, or will be in the next few months, this is the most effective solution.

Current prices, which aren't horrendous at the moment, are likely to drop further, too, but always check the contention rate when choosing a supplier. If ADSL is available in the longer term, it may be worth sticking with existing technology to minimise disruption, temporarily using ISDN along with a business unmetered connection like BT's Surftime. In either case, it is worth comparing the availability and features of cable connection and Tele2's wireless service to get the complete picture.

Sites to visit

www.bt.com

www.ntl.co.uk/cablemodems

www.mistral.co.uk

www.tele2.co.uk

Read more on Voice networking and VoIP

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