DECT Tom Jongsma

Contents History of DECT

DECT = Digital Enhanced Cordless Telecommunications First release of the standard in 1992 Designed for short-range Access mechanism to main networks Extension to the standard in 1995 – emergency call procedures – optional direct portable to portable communication feature 1880 – 1900 MHz – Outside Europe also 1900 – 1920 MHz – 1910 – 1930 MHz (several countries in Latin America) – Reservation in some countries 2010 MHz – 2025 MHz

Basic Operating Principles The principles as applied in the DECT standard have been designed to meet the following objectives: high capacity cellular structured network access allowing for network wide mobility Flexible and powerful identities and addressing high spectrum efficiency reliable - high quality and secure - radio access robustness even in hostile radio environments speech transmission quality comparable to the wired telephony service enabling cost efficient implementations of system components allowing for implementation of a wide variety of terminals like e.g. small pocketable handsets flexibility towards varying bandwidth needs (which is bandwidth on demand e.g. for ISDN and data applications) Furthermore, the standard reflects a high degree of flexibility in the protocols to enable future extension.

Channels 1880 – 1900  10 channels Modulation GFSK (Gaussian Frequency Shift Keying) BT=0.5 Dynamic channel allocation to reduce interference – all equipment scans for at least 30 seconds as background activity

Access methodology A number of techniques are used: – Frequency division multiple access (FDMA) – Time Division Multiple Access (TDMA) – Time Division Duplex (TDD) Time frames of 10ms – Each frame 24 timeslots First 12 downlink transmission Second 12 used for uplink Basic full duplex speech uses 2 paired timeslots with 5ms separation (32 kbps (ADPCM G.726 coded))

ADPCM

TDMA Serves up to 12 simultaneous basic voice connections per transceiver.

Average transmission power Europe – 10 mW (250 mW peak) US – 4 mW (100 mW peak)

Other features For data transmission purposes error protected net throughput rates of n x 24 kbit/s can be achieved, up to a maximum of 552 kbit/s with full security as applied by the basic DECT standard. Using the MC/TDMA/TDD principle for basic DECT (utilising both frequency and time dimensions) a total spectrum of 120 duplex channels is available to a DECT de-vice at any instant location. Therefore dense packing of DECT base stations (e.g. at a distance of 25 m in an ideal hexagonal coverage model) will allow for a traffic capacity of the basic DECT tech-nology up to approx Erlang/km^2

Questions?

Bibliography