48
Glossary
The selection of the codec for the telephone connection therefore influences the voice
quality and, via the available bandwidth, the possible number of usable channels per
base station.
Codecs in
G.722
Excellent voice quality. The G.722 codec works at the same bit rate as G.711 (64 kbit/s
per speech connection) but with a higher sampling rate. This allows higher frequen-
cies to be played back. The speech tone is therefore clearer and better than with the
other codecs and enables a speech tone in High Definition Sound Performance
(
£
).
G.711 a law/G.711 µ law
Excellent voice quality (comparable with ISDN). The necessary bandwidth is 64 kbit/s
per voice connection.
Codecs in
G.726
Good voice quality (inferior to that with G.711 but better than with G.729). The neces-
sary bandwidth is 32 kbit/s per voice connection.
G.729
Average voice quality. The necessary bandwidth is less than or equal to 8 kbit/s per
voice connection.
dBm
Decibel (dB) related to milliwatt (mW)
Unit of measure for the send power.
0 dBm corresponds to a power of 1 mW, larger power values have positive dBm values,
smaller power values have negative dBm values. The ratio of dBm to mW is logarithmic.
An increase of 30 dB corresponds to a thousand fold increase.
Consequently, the power of one microwatt (µW) corresponds to -30 dBm, one nanowatt
(nW) to -60 dBm and one picowatt (pW) to -90 dBm.
DCS
Dynamic Channel Selection
A process for DECT radio networks that base stations can use to flexibly determine and
select the channels with the best availability.
DECT
Digital Enhanced Cordless Telecommunications
Global standard for wireless connection of mobile end devices (handsets) to telephone
base stations.
DECT Manager
Exchange in a DECT multi-cell system. The DECT Manager groups several DECT base sta-
tions together as a DECT network.
VoIPon www.voipon.co.uk [email protected] Tel: +44 (0)1245 808195 Fax: +44 (0)1245 808299
