A radio cell is the area that can be received in the transmitted signal from a transmitting device of a mobile radio network and decoded correctly. Each radio cell has a cell ID.
The size of a cell is dependent on meteorological and geographical conditions, structure height and type of antenna used, the transmission power and the mobile radio standard used. It is only a few meters in diameter for a UMTS femtocell, 35 km for an ordinary GSM cell and the double for sparsely populated areas ( coastal waters). A diameter of 170 km with an area of 91992 km 2, the theoretically achievable maximum surface of a GSM400 cell, which is already not covered due to the geometry of a conventional antenna mast.
Depending on the mobile phone standard used, the size of the cells with the capacity to change. One refers to this effect as cellular respiration.
The potential capacity of a cell depends largely on the mobile radio standard used, and can be between four simultaneous calls ( in one radio cell of the TETRA standard ) over seven simultaneous calls ( in a GSM radio cell with a used carrier frequency ) over 260 simultaneous calls ( in a UMTS radio cell with two frequencies used ) up to 860 simultaneous calls are ( technically conditional maximum in a GSM radio cell).
Adjacent radio cells, regardless of standards, usually overlap. This has two reasons:
- Devices that have no active connection to the network, the opportunity should be given to select a new cell at deteriorating supply. The process of selecting a new radio cell is called cell reselection.
- Devices that have an active connection to the network, a new cell can be assigned for further communication from the network, without interrupting the communication process. The operation of the uninterrupted handover of a communication link from one cell to another is called handover.