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
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
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
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
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
Watershed in voice communications
Business cordless is expected to demonstrate by far the
strongest growth of the cordless market segments up to the year
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
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.