The signalling transported on the SDCCH channel is aimed at
reaching the service requested by the Mobile Station; in some cases this
represents only the setup of the service, in other cases the service is
completely performed on the SDCCH channel.
Considering a call for example, the SDCCH signalling contains the
messages for the setup of the service required, that is the exchange of
information between the Mobile Station and the network in order to create
the call scenario; considering a SMS, all the signalling during the service is
transported on the SDCCH channel. In both of the cases the initial signalling
for accessing the network by a Mobile Station requiring a service is
transported on the SDCCH channel.
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