Digital Enhanced Cordless Telecommunications - Application

Application

The DECT standard fully specifies a means for a portable unit, such as a cordless telephone, to access a fixed telecoms network via radio. But, unlike the GSM standards, does not specify any internal aspects of the fixed network itself. Connectivity to the fixed network (which may be of many different kinds) is done through a base station or "Radio Fixed Part" to terminate the radio link, and a gateway to connect calls to the fixed network. In most cases the gateway connection is to the public switched telephone network or telephone jack, although connectivity with newer technologies such as Voice over IP has become available. There are also other devices such as some baby monitors utilizing DECT, and in these devices there is no gateway functionality.

The DECT standard originally envisaged three major areas of application:

• Domestic cordless telephony, using a single base station to connect one or more handsets to the public telecoms network.
• Enterprise premises cordless PABXs and wireless LANs, using many base stations for coverage. Calls continue as users move between different coverage cells, through a mechanism called handover. Calls can be both within the system and to the public telecoms network.
• Public access, using large numbers of base stations to provide high capacity building or urban area coverage as part of a public telecoms network.

Of these, the domestic application (cordless home telephones) has been extremely successful. The enterprise PABX market had some success, and all the major PABX vendors have offered DECT access options. The public access application did not succeed, since public cellular networks rapidly out-competed DECT by coupling their ubiquitous coverage with large increases in capacity and continuously falling costs. There has been only one major installation of DECT for public access: in early 1998 Telecom Italia launched a DECT network known as "Fido" after much regulatory delay, covering major cities in Italy. The service was promoted for only a few months and, having peaked at 142,000 subscribers, was shut down in 2001.

DECT has also been used for Fixed Wireless Access as a substitute for copper pairs in the "last mile" in countries such as India and South Africa. By using directional antennas and sacrificing some traffic capacity, cell coverage could extend to over 10 km. In Europe the power limit laid down for use of the DECT spectrum (250 mW peak) was expressed in ERP, rather than the more commonly used EIRP, permitting the use of high-gain directional antennas to produce much higher EIRP and hence long ranges.

The standard is also used in electronic cash terminals, traffic lights, and remote door openers.