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DECT

DECT. Tom Jongsma. Contents. History of DECT. 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

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DECT

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  1. DECT Tom Jongsma

  2. Contents • History of DECT

  3. 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

  4. 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.

  5. 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

  6. Access methodology • A number of techniques are used: • Frequencydivision multiple access (FDMA) • Time Division Multiple Access (TDMA) • Time Division Duplex (TDD) • Time frames of 10ms • Each frame 24 timeslots • First 12 downlinktransmission • Second 12 usedforuplink • Basic full duplex speech uses 2 pairedtimeslotswith 5ms separation (32 kbps (ADPCM G.726 coded))

  7. ADPCM

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

  9. Average transmission power • Europe • 10 mW (250 mW peak) • US • 4 mW (100 mW peak)

  10. 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. 10000 Erlang/km^2

  11. Questions?

  12. Bibliography • http://www.radio-electronics.com/info/wireless/dect/dect_basics.php • http://einstein.informatik.uni-oldenburg.de/rechnernetze/seite24.htm

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