# BSS

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Descriptions

The BSS is composed of two parts:

•The Base Transceiver Station (BTS)

•The Base Station Controller (BSC)

The Base Station Controller (BSC) manages the radio resources for one or more BTSs. It handles radio channel setup, frequency hopping, and handovers. The BSC is the connection between the mobile and the MSC. The BSC also translates the 13 Kbps voice channel used over the radio link to the standard 64 Kbps channel used by the Public Switched Telephone Network.

It assigns and releases frequencies and time slots for the MS. The BSC also handles intercell handover. It controls the power transmission of the BSS and MS in its area. The function of the BSC is to allocate the necessary time slots between the BTS and the MSC. It is a switching device that handles the radio resources. Additional functions include:

•Control of frequency hopping

•Performing traffic concentration to reduce the number of lines from the MSC

•Providing an interface to the Operations and Maintenance Center for the BSS

•Reallocation of frequencies among BTSs

•Time and frequency synchronization

•Power management

•Time-delay measurements of received signals from the MS

The Base Transceiver Station (BTS) houses the radio transceivers that define a cell and handles the radio link protocols with the MS. In a large urban area, a large number of BTSs may be deployed.

The BTS corresponds to the transceivers and antennas used in each cell of the network. A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell. Each BTS has between 1 and 16 transceivers, depending on the density of users in the cell. Each BTS serves a single cell. It also includes the following functions:

•Encoding, encrypting, multiplexing, modulating, and feeding the RF signals to the antenna.

•Transcoding and rate adaptation

•Time and frequency synchronizing

•Voice through full- or half-rate services

•Decoding, decrypting, and equalizing received signals

•Random access detection

•Timing advances

•Uplink channel measurements

Please note that before you can create a BSC object, you must have a physical BSC installed and connected to the MSC. The BSC to EMS connection is over ethernet. The MSC to BSC connection, which is called the A interface, is over one or more E1 or T1 links. To install the BSC hardware, please refer to the BSC Installation and Commissioning Guide.

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