What is DECT? - Technology Tutorial

- this overview or tutorial looks at the basics of DECT: Digital Enhanced Cordless Telecommunications, outlining its technology, features and the way in which it operates.

DECT (Digital Enhanced Cordless Telecommunications) technology is widely used for residential, and business cordless phone communications. Designed for short-range use as an access mechanism to the main networks, DECT technology offers cordless voice, fax, data and multimedia communications, wireless local area networks and wireless PBX.

With the flexibility offered by cordless phone communications, DECT technology has become the major standard for this application and DECT is now in use in over 100 countries worldwide.

DECT technology development

The standard for DECT or Digital Enhanced Telecommunications system was developed by members of the European Telecommunications Standards Institute (ETSI). The first release of the standard was available in 1992 after which much of the work was focussed on inter-working protocols (DECT / GSM, DECT/ISDN, etc).

As a result of this work, DECT / GSM inter-working has been standardized and the basic GSM services can be provided over the DECT air interface. This enables DECT terminals to inter-work with DECT systems which are connected to the GSM infrastructure. All roaming scenarios based on SIM roaming as described in GSM specifications are applicable.

Along with requirements arising from the growing use of DECT, this work gave rise to a number of extensions to the basic DECT standard. This led to a second release of the standard at the end of 1995. This included facilities including : emergency call procedures, definition of the Wireless Relay Station (WRS), and an optional direct portable to portable communication feature.

DECT codecs

The basic telephony speech quality offered by DECT is very high compared to many other wireless systems. This is the result of the use of the ITU-T Recommendation G.726 codec that is employed. This is a 32 kbit/s ADPCM speech codec and although it uses 32 kbps, the quality it affords is high and there is more than sufficient bandwidth within the system to support it.

TDMA structure

The DECT TDMA structure enables up to 12 simultaneous basic voice connections per transceiver. The system is also able to provide widely varying bandwidths by combining multiple channels into a single bearer. For data transmission purposes error protected net throughput rates of integral multiples of 24 kbps can be achieved. However the DECT standard defines a maximum data rate of 552 kbps with full security.

What is DECT GAP profile?

All DECT systems are based on a main standard that is the Common Interface (CI), which is often used in association with the Generic Access Profile (GAP). The GAP profile ensures interoperability of equipment from different providers for voice applications. The GAP defines the minimum interoperability requirements including mobility management and security features. It has different requirements on public and private systems. This means that the GAP is effectively the industry standard for a basic fall-back speech service with mobility management. This basic service is not always used, but instead it forms the fallback that is always be available, especially when requested by a roaming phone, etc

DECT Summary

Although DECT has been in use for a number of years now, its flexibility and performance have meant that it is still the major technology used for cordless phones. The standard is maintained by ETSI, and this will enable it to move forward as new requirements appear and technology enables further facilities to be added.

DECT Glossary

DECT Digital Enhanced Cordless Telecommunications
DMAP DECT Multimedia Access Profile
DPRS DECT Packet Radio Service
FP Fixed Part - the base station
GAP Generic Access Profile
GSM Global System for Mobile telecommunications
IMT-2000 International Mobile Telecommunications 2000
PP Portable Part - the handset
RES Radio Equipment Systems

By Ian Poole

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