BSS Description B10 (3FL10473A-ed 2)

1. Evolium BSS Introduction
Situation and Functions
ALCATEL BSS Description 14
BSS functions (1): CALL SETUP
The BSS provides radio coverage (signalling and traffic channels) between
Mobiles and the NSS.
MOBILITY MANAGEMENT
Location updating
SUPPLEMENTARY SERVICES
Short Message Service
USER TRAFFIC
Speech
Data
EVOLIUM
ALCATEL BSS Description
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Call set up is required to establish communication between an MS and the NSS. The NSS is responsible for
establishing the connection with the correspondent. Different types of calls require different
teleservices. These teleservices are defined in the GSM specifications. The type of teleservice and
bearer service to be used is negotiated before the normal assignment procedure.
Mobility Management : These calls, e.g. location update, are used by the system to gather MS
information. The exchanges are protocol messages only; therefore, only a signaling channel is used.
Supplementary Services : These calls, e.g. SMS and SS calls, pass small amounts of information.
Therefore, only a signaling channel is used.
User Traffic : These calls, e.g. speech or data calls to a correspondent, can pass large amounts of
information. Therefore they require greater bandwidth than a signaling channel. These calls use
traffic channels.
The channels used for calls are the SDCCH for signaling and the TCH for user traffic. These channels are
associated with FACCH/SACCH. An SDCCH is always assigned for call set up, even if a TCH is later
required for the call.
The role of the BSS in call set up is to assign the correct channel for the call, and to provide and manage
a communication path between the MS and the MSC.
The phases involved in call set up:
Radio and Link Establishment;
Authentication and Ciphering;
Normal assignment.
All Rights Reserved © 2007, Alcatel-Lucent
3FL10473ADAAWBZZA Edition 02
EVOLIUM ALCATEL BSS Description Page 14