54
V
e
rsio
n 2,
06
.0
8.
201
0 / M
o
d
u
leV
e
rs
io
n 1.
0
Glossary
Gigaset N870 IP PRO / LUG IE-UK_IM en / A31008-XXXXX-XXXX-X-XX / glossary.fm / 8/24/18
Glossary
Bandwidth
The bandwidth defines the size or transmission capacity of a transmission channel or, more
precisely, the difference between the lowest and highest possible frequency on a transmission
channel. The bandwidth is specified in Hz. For digital data transmission, the bandwidth
determines the data volume that can pass through a transmission channel in a specified
period, i.e., the transmission speed (specified in bit/s).
The bandwidth used to transmit analogue voice data via a digital transmission medium, e.g.,
the Internet for VoIP, determines the number of channels that can be used simultaneously
and the quality of the voice transmission. How the available bandwidth is used to transmit
voice data is determined by the selection of a
. Codecs are available for broadband
transmission up to 64 Kbit/s (
) or narrowband transmission up to 32
Kbit/s (
£
).
Broadband mode
For VoIP (digital transmission medium), voice data is transmitted in broadband mode or in
£
. In broadband mode, a transmission rate or
£
of 64 Kbit/s
is available.
The bandwidth used for the transmission is determined by the selection of a
£
Cluster
Subdivision of a DECT network into groups (subnets) by a central management station
(DECT Manager). All telephones in the network use the central functions of the PABX
(VoIP configuration, directories, etc.). However, the base stations only synchronise within
a cluster, meaning that a handover of a handset from one cluster to a neighbouring cluster
is not possible.
Codec
Codec is a procedure that digitalises and compresses analogue voice before it is sent via the
Internet, and decodes – i.e. translates into analogue voice – digital data when voice packets
are received. There are different codecs that vary, for instance, in the level of compression.
Both parties involved in the telephone connection (caller/sender and recipient) must use
the same codec. This is negotiated between the sender and the recipient when establishing
a connection.
The choice of codec is a compromise between voice quality, transmission speed and the
necessary
£
. A high level of compression, for example, means that the bandwidth
required for each voice connection is low. However, it also means that the time needed to
compress/decompress the data is greater, which increases execution time for data in the
network and thus impairs voice quality. The time required increases the delay between
the sender speaking and the recipient hearing what has been said.
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