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GSM OSS vs BSS | Difference between OSS and BSS in GSM

This page GSM OSS vs BSS describes difference between OSS and BSS subsystems used in GSM. OSS stands for operation and support system and BSS stands for Base Station Subsystem. Refer GSM tutorial covering following sub topics related to GSM technology:
GSM Tutorial Main Page  Frame  Burst types  PHY  gsm stack  speech processing  ARFCN  Channel types  GSM Security  Network Entry  Mobile basics 

The figure depicts GSM Network Architecture. As shown, GSM system composed of following three main parts:
1. Base Station Subsystem (BSS)
2. OSS (operation and support system) OR NSS (Network Subsystem or Network Switching Subsystem)
3. Mobile Subscriber Station (MS)

GSM is used for cellular communication. Like GSM there are other wireless standards such as CDMA, Mobile WiMAX and LTE which are used for cellular voice and data communication.
Refer Cellular Communication Tutorial➤➤

GSM OSS-Operation and Support System


OSS is also referred by the name CN (Core Network). GSM OSS composed of following subsystems:
• MSC-Mobile Services Switching Center
• VLR-Visitor Location Register
• HLR-Home Location Register
• AUC-Authentication Center
• EIR-Equipment Identity Register
• OMC-Operation and Maintenance Center
• Data communication network

Following are the functions of GSM OSS:

➨Mobility Management

➨Call handling

➨Subscriber data management such as plans, name, address, billing cycle etc.

➨Switching of calls between cellular to cellular, between cellular and PSTN , between CS and PS etc.

➨Authentication and equipment validation

➨It houses MSC and GMSC which take care of switching related functionalities desired on GSM mobile system.

➨In order to perform above functions OSS is divided into databases (or registers) and switches. HLR is the master database which stores parmanent information of subscribes. VLR is temporary database of visiting subscribers in the area. AUC takes care of subscriber authentication. EIR takes care of handset verification.

GSM BSS-Base Station Subsystem

GSM BSS resides between MS and GSM OSS(or NSS). GSM BSS composed of following subsystems:
• BTS-Base Transceiver Station
• BSC-Base Station Controller

Following are the functions of GSM BSS:

➨It performs functions specific to radio access techniques used.

➨Its primary function is to communicate with MS in certain area as covered by Core Network(CN, made of MSC/VLR)

➨Radio equipments in BSS cover one or more cells.

➨BTS part provides services in a cell. BTS works as per commands by the BSC. BTS also performs functions such as channel coding, encryption, decryption on the radio interface as well as transcoding and rate adoption.

➨BSC controls one or more BTS. The primary function of BSC is to control the radio resources of GSM RAN (Radio Access Network). The other functions of BSC include radio resource management, intercell handovers, control of BTS, power control etc.

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