Cell breathing (telephony)
As cellular respiration in English literature often called cell breathing, the load-dependent increase and decrease the coverage area of a radio cell in which the code division method is used, respectively. Cellular respiration occurs, for example in UMTS mobile networks, but not in GSM networks.
With increasing number of users, the mutual interference rise in a cell that occur only in the quasi-orthogonal scrambling codes of the code division multiple access. This can be compensated by increasing the transmission power of the individual terminals, designated by the required ratio of useful signal to interference signals, as a signal -to-noise ratio (SNR) to recover. Inevitably shall include all devices increase its transmission power within a radio cell, which with increasing distance to the base station (NodeB ) must be increased in any case to compensate the signal attenuation.
The permissible or possible maximum transmit power is limited (in the case of UMTS terminals to 250 mW ), so that already transmitted with maximum power terminals can not further increase the transmission power in case of increasing inferences. Thus, the required ratio of useful signal to noise no longer be achieved and the communication with the base station stops.
This therefore results in a reduction of the range of the base station, since only those devices can further increase the transmission power, which have not yet reached the maximum transmission power due to the lower distance to the base station, shrinking the coverage area of the cell. With decrease in the number of users, the range of the base station then rises again.
Because of its analogy with the change in lung volume during inspiration and expiration, this process is referred to as cell breathing.