FDMA

FDMA:

FDMA is the process of dividing a channel bandwidth or more separate bands , each for use by a single user (Fig. 1). Each individual band or channel is wide enough to accommodate the spread spectra transmissions. The transmitted data is modulated on each sub- carrier, and all of them.

 

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FDMA divides the shared medium bandwidth of individual channels. Subcarriers modulated by transmitting the information occupy each sub channel.

The best example of this is the cable television system. medium coaxial cable that is used to broadcast hundreds of channels of video / audio programming houses. The coaxial cable has a useful bandwidth of about 4 MHz to 1 GHz. bandwidth is divided into 6-MHz wide channels. First, a station or channel created by a single 6 MHz band. However, with digital techniques, a number of TV channels can now share a single band due to compression and multiplexing techniques that are used in each channel.

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This technique is also used in glass fiber communication systems. A single optical fiber has a huge bandwidth that can be divided to provide FDMA. Various data or information are each assigned to a different light frequencies to transmit. Light generally not determined by the frequency, but by the wavelength (λ). As a result, glass fiber is called FDMA wavelength division multiple access (WDMA), or simply wavelength division multiplexing (WDM).

One older FDMA system is the original analog phone system, which uses a frequency-division multiplex hierarchy of methods to place multiple calls on one line. The analogue 300 Hz to 3400 Hz voice signal is used to modulate sub-carriers 12 channels of 60 kHz to 108 kHz. Modulator / mixers made single sideband (SSB) signals, both the upper and lower sidebands. The sub-carriers are then further sub-carriers frequency multiplexed in 312-kHz to 552 kHz range with the same modulation technique. On the receiving end of the apparatus, the signals are sorted and recovered with filters and demodulators.

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Original space telemetry system that uses a FDMA system to have multiple data sensor suitable for a radio channel. Early satellite shared individual 36-MHz bandwidth transponders to 4 GHz to 6 GHz with multiple voice, video or data signals by FDMA.

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Posted by on Jul 22 2016. Filed under Latest Updates, FDMA, Mobile Communication, TECHNOLOGY. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

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