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ALCATEL LUCENT BTSPrepared By: SAYED QAISAR SHAH BS TELECOM,CWNA,CCNA.
BTS Role in GSM NetworkThe BTS provides two-way radio communicationbetween the PSTN and Mobile Station (MobileSet) located in a single GSM cell. It also providesa similar link between the mobile station andthe rest of the networks. The BTS provides oninterface for the digital baseband signals used bythe land based networks and the GSM radiosignals used by mobile station.
BTS Functions As the principal interface between the PSTN and Mobile Stations, the BTS performs four primary functions. Transmission function: which manage the transfer of traffic and control data between the BTS and BSC. Telecommunication functions: which manage the transfer of traffic and control data between the BTS and Mobile Station. O&M function: which supervise the operation of the BTS. Support function: which provides a logical and physical environment in which the BTS functions can be realized.Communication between the transmission, telecommunication, and O&M functions is managed according to the OSI model. The BTS functions are concerned with layer 1 (Physical), Layer 2 (Data Link), and Layer 3 (Network) of this model.
Transmission Functions To minimize operating costs, all data passed between the BTS and BSC in Time division multiplexed onto a single physical interface. This is the Abis Interface, which carries all the data sent between the BSC and BTS. Logical links between the BSC and BTS handles the following information: Signaling data used for control purposes O&M data for the BTS transmission module O&M data for the BTS entities User data in the form of speech and data traffic.
Transmission FunctionsAbis Interface:For BTS and BSC multiplexing equipment is normally connected using dedicated cabling. Other method of Abis Interface connection can be used for BTS, where the installation of the dedicated cabling in not possible. In this case, control of the transmission medium is in the hands of third party. Microwave Link (used where line of sight radio path is available. Leased Line (Copper Cable or Fiber Optic used where the distance between the BSC and BTS is too great for microwave). Satellite Link (Used where Previous two methods are not possible
Telecommunication Function There are two primary telecommunication functions:Baseband Functions:Based band functions modulate and encode traffic and signaling data from the BSC according to GSM recommendations. This data is then sent to the Mobile Stations using the RF function. Traffic and signaling received from the Mobile Stations is demodulated and decoded to recover the baseband data.
Telecommunication FunctionRF Function: RF functions enable traffic and signaling to be sent and received over the Air Interface as a radio signal. A special link layer protocol ensures the reliable transfer of signaling data over the Air Interface. For antenna Diversity, the telecommunication function uplink path is duplicated. The duplicated functions intend from the antennas, through the RF functions.
O&M Functions O&M functions monitor and control the correct operation of the BTS and its external interfaces. These function are shared between the BTS and BSC. The BSC provides overall control. The O&M function use Layer 2 links for BTS internal communications. A terminal connected via an MMI is used for local operator control of the BTS. There are three categorized of O&M function: Configuration Management Fault Management External Alarm Handling. The O&M function also control the operation of the RF self-tests and manage the actions required by the BTS recovery Strategy
Support FunctionThe support function provides a number of services relevant to the internal working of the BTS are: Internal Power Supplies. Internal Temperature Control. Master Frequency. Clock generation and distribution. External alarm collection. Internal self tests.