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frequency economy

Frequency economicsis concerned with the effective use of the available frequencies for radio-technological transmissions. Since the resource frequency cannot be duplicated, but at the same time the message content and the number of media using radio technology for message transmissionare rapidly increasing, frequency economics relies on regulations and procedures with which a frequency band and the radio range can be better utilized. The regulations include the frequency utilization plan of the Federal Network Agency, the various modulation methods and coding, the reuse of frequencies, frequency reuse, and other frequency-saving concepts.

A look back illustrates the problems faced by spectrum economics. In the early years of radio technology, long wave, medium wave and short wave were available for message transmission. It was not until later, in the 1950s, that higher frequencies in the VHF band could be used for FM broadcasting and television. For reasons of frequency economy, transmission in the shortwave band, for example, is relatively narrowband with single-sideband modulation.

Examples of frequency economy

If, on the other hand, we look at a television signal, the images in the early years were black and white. If a television picture were transmitted at the theoretical resolution, the black-and-white television picture would require 6.5 MHz of bandwidth, which is calculated as 625 lines x 833 pixels (3:4) x 25 frames. With amplitude modulation, two sidebands would be formed and the entire frequency band would assume a circumference of 13 MHz. This would mean that only four television stations could broadcast in television band III between 174 MHz and 230 MHz. This is where frequency economy kicks in by transmitting the TV signal in the upper sideband with full bandwidth, but in the lower sideband as residual sideband modulation with reduced bandwidth. In addition, the total bandwidth for the video signal is reduced so that the transmission requires a frequency range of 6 MHz. The audio is frequency modulated within the video signal without causing interference between video and audio. The bandwidth requirement is unaffected. The same applies to the insertion of the color difference signal and the stereo sound.

It can be seen from this example that the clever choice of modulation methods and the interleaving of signals are two possible approaches to frequency economy. Others lie in digitization and compression.

More efficient use of frequency through digitization and optimized modulation methods

Thanks to digitization, frequency spectra can be used much more efficiently. This results in higher frequency efficiency. For example, 6 to 8 digital TV channels can be transmitted in one analog TV channel. Thanks to digitization, in the UHF ranges where analog TV was previously transmitted, despite a multiple of TV channels, an extensive frequency range at 700 MHz was freed up and could be used for other transmission services. This frequency range is known as the digital dividend. Another technology that uses dynamic resource adaptation is Cognitive Radio( CR).

Multicarrier modulations have also become established in radio technology, exploiting the spectral, temporal and spatial dimensions of the transmission link and thus contributing to more economical use of frequency ranges. In this context, frequency division multiplexing( FDM), orthogonal frequency division multiplexing( OFDM) with orthogonally aligned subcarriers, spatial multiplexing, and space time block coding( STBC). Antenna technology has also contributed to better utilization of available spectrum resources. Thus with cognitive antenna systems and smart antennas.

Englisch: frequency economy
Updated at: 20.12.2021
#Words: 539
Links: frequency (f), message (MSG), content, media, radio technology
Translations: DE

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