Wireless/cordless phones

Cordless telephones first appeared in the late 1970’s and have experienced spectacular growth ever since.

Roughly half of the phones in U.S. homes today are cordless. Cordless phones were originally designed

to provide a low-cost low-mobility wireless connection to the PSTN, i.e. a short wireless link to replace

the cord connecting a telephone base unit and its handset. Since cordless phones compete with wired

handsets, their voice quality must be similar: initial cordless phones had poor voice quality and were

quickly discarded by users. The first cordless systems allowed only one phone handset to connect to each

base unit, and coverage was limited to a few rooms of a house or office. This is still the main premise

behind cordless telephones in the U.S. today, although these phones now use digital technology instead

of analog. In Europe and the Far East digital cordless phone systems have evolved to provide coverage

over much wider areas, both in and away from home, and are similar in many ways to today’s cellular

telephone systems.

Digital cordless phone systems in the U.S. today consist of a wireless handset connected to a single

base unit which in turn is connected to the PSTN. These cordless phones impose no added complexity

on the telephone network, since the cordless base unit acts just like a wireline telephone for networking

purposes. The movement of these cordless handsets is extremely limited: a handset must remain within

range of its base unit. There is no coordination with other cordless phone systems, so a high density of

these systems in a small area, e.g. an apartment building, can result in significant interference between

systems. For this reason cordless phones today have multiple voice channels and scan between these

channels to find the one with minimal interference. Spread spectrum cordless phones have also been

introduced to reduce interference from other systems and narrowband interference.

In Europe and the Far East the second generation of digital cordless phones (CT-2, for cordless

telephone, second generation 2G) have an extended range of use beyond a single residence or office. Within

a home these systems operate as conventional cordless phones. To extend the range beyond the home

base stations, also called phone-points or telepoints, are mounted in places where people congregate, like

shopping malls, busy streets, train stations, and airports. Cordless phones registered with the telepoint

provider can place calls whenever they are in range of a telepoint. Calls cannot be received from the

telepoint since the network has no routing support for mobile users, although some newer CT-2 handsets

have built-in pagers to compensate for this deficiency. These systems also do not handoff calls if a user

moves between different telepoints, so a user must remain within range of the telepoint where his call

was initiated for the duration of the call. Telepoint service was introduced twice in the United Kingdom

and failed both times, but these systems grew rapidly in Hong Kong and Singapore through the mid

1990’s. This rapid growth deteriorated quickly after the first few years, as cellular phone operators cut

prices to compete with telepoint service. The main complaint about telepoint service was the incomplete

radio coverage and lack of handoff. Since cellular systems avoid these problems, as long as prices were

competitive there was little reason for people to use telepoint services. Most of these services have now

disappeared.

Another evolution of the cordless telephone designed primarily for office buildings is the European

DECT system. The main function of DECT is to provide local mobility support for users in an in-building private branch exchange.

Technology has so much advanced in such a way that one can easily leave his phone behind at home and freely move from one geographical location to another and still be in touch with the data communications happening in his phone through several wireless communication systems such as WiFi, Bluetooth and so on.

Modern technological advancement in the area of communication is a welcomed development and we look forward to a world of inexplicable innovations.