bandwidth efficiency

The fire-width efficiency, also referred to as spectral efficiency, is an important telecommunications parameter that indicates how many units of information are transmitted per hertz in the available bandwidth. It is thus the ratio of the data transmission rateto the occupied bandwidth, which is specified in bit/s/ Hz.

Spectral efficiency depends on the modulation method and coding used. Since the available bandwidths cannot be increased arbitrarily, the frequency economy and the modulation method used are decisive for the spectral efficiency. One only has to think of single-sideband mod ulation with which the frequency economy is improved and of coding methods in which the code elements are represented by several levels or by extended bit combinations.

Spectral efficiency is limited by the signal-to- noise ratio( SNR). The relationship between bandwidth and signal-to-noise ratio is defined in the Shannon-Hartley law. According to this law, channel capacity increases linearly with bandwidth and is affected by the signal-to-noise ratio to a logarithmic degree. With modern modulation techniques, such as Orthogonal Frequency Division Multiplex( OFDM) and elaborate antenna constellations, such as Multiple Input Multiple Output( MIMO), the S/N ratio and thus the bandwidth efficiency can be improved.

For network operators, spectral efficiency is an important parameter because it allows them to transmit more data over the same frequency range. Spectral efficiency plays an important role in all message and radio transmissions, and it must be improved. In mobile radio systems, bandwidth efficiency values range from 1 bit/s/Hz to 15 bit/s/Hz. The specifications in mobile communications networks often refer to a radio range or a radio cell.