Bearer Capability in
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than tha ...
is one of the Information Elements (fields) of the
Q.931 SETUP message. It is used by the calling party to specify the kind of
B channel
{{for, Indonesian television network formerly known as B-Channel, RTV (Indonesian TV network)
B channel (bearer) is a telecommunications term which refers to the ISDN channel in which the primary data or voice communication is carried. It has a ...
that is being requested.
Description
For example, if a Bearer Capability of Speech is specified, then the network is free to select a set of facilities that are able to provide this service (including, in this case, analogue trunks and routes involving
echo canceller
Echo suppression and echo cancellation are methods used in telephony to improve voice quality by preventing echo from being created or removing it after it is already present. In addition to improving subjective audio quality, echo suppression i ...
s or
DCME).
If, on the other hand, a Bearer Capability of Unrestricted Digital Information
is specified, then the network is required to set up the call using only end-to-end digital facilities (without the use of robbed-bit signalling, echo cancellers, DCME nor
A-law
An A-law algorithm is a standard companding algorithm, used in European 8-bit PCM digital communications systems to optimize, i.e. modify, the dynamic range of an analog signal for digitizing. It is one of two versions of the G.711 standard ...
to
mu-law conversion), or reject the call if no end-to-end digital circuit is available.
The Bearer Capability is augmented by the Higher Layer Compatibility (HLC) Information Elemen
(another field in the Q.931 SETUP message), which informs the network of the use that the caller intends to make of the channel.
References
External links
ITU-T Recommendation Q.931paragraph 4.5.5.
Integrated Services Digital Network
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