Base Transceiver Station
A base transceiver station ( BTS; German base transceiver station ) is a network element in the base station subsystem of the GSM digital cellular network. It is also referred to as a GSM base station. The correspondence to the BTS in a UMTS network is the Node B.
A BTS supplied at least one radio cell. In practice, most systems are built that combine 3 or 6, but also rarely 4, radio cells in it. In these cases, sector antennas are used, which targeted a mostly between 60 ° and 120 ° wide region, the so-called sector supply.
In a radio cell is usually one to five frequencies are used, often of up to eight. The theoretical, technically related, maximum is at 18 frequencies in a radio cell.
The range of a BTS is under practical conditions, due to the path loss between a few hundred meters and several kilometers. Since the propagation delay between the base station and mobile station by the timing advance parameter must be balanced, is the theoretical maximum range of 35.41 km, with GSM 400 121.73 km. Means of a special configuration, but it has an effect on the cell capacity, the increased range of a GSM cell 400 can also be achieved in the cells of all other GSM standards.
The base station is mainly used for transmission over the air interface; the control and monitoring functions are largely perceived by the Base Station Controller (BSC ).
The tasks of a BTS are:
- Providing signals to terminals to allow synchronization with the station (Frequency correction bursts in FCCH, synchronization bursts in SCH)
- Activation and deactivation of the assigned frequency channels
- Implementation of frequency hopping
- Encryption and decryption of transmission and control channel means A5
- Identification and assignment of timing advance
- Determining the reception level and the reception quality
- Signal adjustment is carried out on the PCM interface, the connection to the BSC and the MSC.