Complete business communications mobility - a utopian vision not all that long ago - seems to be approaching in quantum leaps. The cordless telephone is undoubtedly a key factor in reshaping voice communication patterns. This article answers some basic questions about the world of cordless, particularly in terms of the technologies and standards developed to meet the needs of an increasingly vibrant marketplace.

The telephone's pure magic. It can do the most weird and wonderful things. But there's one thing it cannot do. It has no way of guaranteeing that the person you want to talk to is available to take your call.

If you're ringing privately, in nine cases out of ten this is not going to be all that much of a problem. After all, you can always call back some other time, or leave appropriate instructions on the absent party's answering machine.

If you're calling on business, though, the consequences of not being able to reach someone immediately can be anything from merely frustrating to downright disastrous.

Orders can be lost, deadlines missed, goodwill ravaged.

Instant availability, in other words, can be a critical factor in a business environment.

Bearing this in mind, it's hard to believe that as many as 70 per cent of business calls don't reach the right person at the first attempt. That's right, a whopping 70 per cent!

So what's the answer? You can't tie people to their desks.

No you can't, but you can tie them to their phones, provided the phones are as mobile as their users. Which is where cordless technology comes in.

Cellular or cordless?

But what exactly is a 'cordless telephone'?

Aren't cellular phones 'cordless' too? And, indeed, aren't cordless phones 'cellular'?

The answer to both questions is of course in the affirmative. In the language of telespeak, however, the terms 'cellular' and 'cordless' have come to assume quite distinct and separate meanings, based on their areas of use and the differing technologies developed to meet user requirements.

Briefly, cellular telephones are intended for what is termed 'off-site' use in cars or other forms of transport. The systems are designed for a relatively low density of users. Here, macrocellular technology provides wide-area coverage and the ability to make calls while travelling at high speeds. This form of communications is therefore often referred to as 'mobile communications'.

Cordless telephones, on the other hand, are designed for users whose movements are within a well defined area. The cordless telephony user makes calls from a portable handset linked by radio signals to a fixed base station. The base station is connected either directly or indirectly to the public network.

The 'on-site' restricted area covered by a cordless system can be anything from a private home to a downtown urban district to a business site. Each application has its own specific needs, technology and standards.

In between cellular and cordless we find microcellular technology. This is a form of cellular communications capable of handling higher user densities.

Business cordless users have more advanced needs. These systems must be capable of offering seamless handover between cells, roaming facilities and impeccable reliability. They must also be able to handle the high user densities of a typical office environment. Picocellular technology is best suited to match these requirements.

Cordless began at home

The cordless system standards are referred to as CT0, CT1, CT2, CT3 and DECT.

In an industry famous for its exotic combinations of letters and digits, the cordless business is no exception. The meanings of these abbreviations are, however, not quite so abstruse as they may seem at first glance.

Hardly surprisingly, the letters 'CT' stand for 'Cordless Telecommuni cations'. So CT0 and CT1 were the technologies for first generation analogue cordless telephones.

Comprising base station, charger and handset, and primarily intended for domestic use, they first became widely available in the early 1980's. With a range of 100-200 metres, they use analogue radio transmission on two separate channels, one to transmit and one to receive speech. The downside is that the limited number of frequencies can result in interference between handsets, even with the relatively low density of residential subscribers.

Also targeted at the residential user, CT2 is an improved version of CT0/CT1.

Using an FDMA (Frequency Division Multiple Access) format, the CT2 system creates capacity by splitting bandwidth into radio channels in the frequency domain. In the initial call setup, the handset will scan the available channels and lock onto an unoccupied channel for the duration of the call. Based on TDD (Time Division Duplexing), the call will be split into time blocks that alternate between transmitting and receiving.

European cordless standard

The DECT (Digital European Cordless Telecommunications) standard was instigated by the Council of European PTT's as a European standard for cordless communications, with applications that included residential telephones, Telepoint, the cordless PBX and cordless local loop access to the public network. Primarily, though, it was designed to solve the problem of providing cordless telephones in high-density, high-traffic office and other business environments.

CT3, on the other hand, is a technology developed by Ericsson in advance of the final agreement on the DECT standard and is designed specifically for the cordless PBX application.

Since DECT is essentially based on CT3 technology, the two standards are very similar.

Both enable the user to make and receive calls when within the range of a base station. Depending on the specific conditions, we are talking about a radius of between 50 and 250 metres from the station. To provide service throughout the site, multiple base stations are set up to create a picocellular network. Handover between cells is supported by a radio exchange connected to the host PBX.

Both DECT and CT3 have been designed to cope with the highest-density telephone environments, such as city centre office districts, where user densities can reach 50,000 per square kilometre. An ingenious feature called CDCS (Continuous Dynamic Channel Selection) ensures seamless handover between cells, which is particularly important in a picocellular environment where several handovers may be necessary during a short call. The digital radio links are encrypted to provide absolute call privacy.

The two standards are based on a multi-carrier TMDA/TDD (Time Division Multiple Access/Time Division Duplexing) format. They do not use the same operating frequencies, though, and consequently have different overall bit rates and call-carrying capacity.

In fact, it is the difference in frequencies that governs the commercial availability of DECT and CT3 around the world. Europe is committed to implementing the DECT standard with the frequency range of 1.8-1.9 GHz. Countries in other areas, however, have made frequencies in the 800-1,000 MHz band available for cordless PBX's, thereby paving the way for the introduction of CT3.

First cordless PBX telephone

In 1989 a Memorandum of Understanding was signed by the major players on the market. In this document they pledged to support DECT and manufacture to the DECT standard. The first DECT products are expected to appear in 1993.

However, having pioneered the CT3 technology in advance of DECT, Ericsson announced the world's very first wireless PBX product in 1990. Known as 'Freeset', this digital cordless telephone system was successfully put through its paces in the most hostile of radio communication environments at the 1992 Barcelona Olympics.

A number of countries, including Australia, Brazil, Hong Kong, Malaysia, New Zealand, Sweden and Thailand, have in fact now made spectrum within the bandwidth used by Freeset available for wireless PBX's.

Watershed in voice communications

Business cordless is expected to demonstrate by far the strongest growth of the cordless market segments up to the year 2000.

This is perhaps not all that surprising in view of the significant benefits offered by this technology, allied to the fact that, due to the availability of add-on products and cordless overlay networks, building a wireless office network does not require the replacement of existing equipment.

Many of the problems arising from the non-availability of staff to a wired PBX can of course be avoided with cordless telephones. They are, for instance, ideal for people who by the very nature of their work can be difficult to locate (maintenance engineers, warehouse staff, messengers, and so on), and for those 'white spots' on a company's premises that cannot be effectively covered by a wired PBX (warehouses, factories, refineries, exhibition halls, despatch points, etc).

Initial customer feedback points to reduced problem-response times, shorter decision-making processes and even lower stress levels resulting from the use of cordless systems. Not to mention the goodwill value of the significantly higher availability of company staff.

Another advantage of business cordless is that the amount of telephone wiring is dramatically reduced. Bearing in mind that companies spend between 10 and 20 per cent of the original cost of their PBX on reconfiguring the system, this will obviously have a significant impact on costs.

Then there are also administrative benefits. For example, when moving offices, employees will not need to change their extension numbers, nor will the system need to be reprogrammed.

In terms of the future growth of business cordless systems, a survey prepared for the European Commission has put the total market for DECT products at up to 8 million units by the year 2000, approximately half of which will be wireless PBX equipment. Across the Atlantic, Probe Research has concluded that as early as 1996 almost one-fifth of all office telephones in the USA will be cordless - - more than 14 million handsets. Ericsson's own predictions suggest a worldwide market of more than 30 million handsets by the turn of the century.

It is no exaggeration to say that the development of cordless can be seen as a watershed in the evolution of voice communications in the business domain.

Whichever way you look at it, this is obviously going to be one of the fastest growing segments of the telecommunications industry over the next decade.

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