Transcript DECT - E.T.S.V. Scintilla

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
– 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. 10000 Erlang/km^2
Questions?
Bibliography
•
http://www.radio-electronics.com/info/wireless/dect/dect_basics.php
•
http://einstein.informatik.uni-oldenburg.de/rechnernetze/seite24.htm