DECT

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DECT

• Tom Jongsma

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Contents

• History of DECT

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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

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• 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.

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Channels

• 1880 1900 ? 10 channels
• Modulation GFSK (Gaussian Frequency Shift Keying)
  BT0.5
• Dynamic channel allocation to reduce interference
  
• all equipment scans for at least 30 seconds as
  background activity

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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))

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ADPCM
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TDMA

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

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Average transmission power

• Europe
• 10 mW (250 mW peak)
• US
• 4 mW (100 mW peak)

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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/km2

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Questions?
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Bibliography

• http//www.radio-electronics.com/info/wireless/dec
  t/dect_basics.php
• http//einstein.informatik.uni-oldenburg.de/rechne
  rnetze/seite24.htm