Why cyclic prefix

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It does not store any personal data. Functional Functional. Multipath Propagation and its Effect on Audio. Toggle navigation DSP Illustrations. Home About Tutorials. The CP turns the linear convolution with the channel into a circular convolution. Only with a circular convolution, we can use the single-tap equalization OFDM is so famous for.

Let us have a more detailed look at the OFDM signal structure:. This article is part of the fundamentals of my real-world tutorial on OFDM using a cheap soundcard as the radio. If this notebook is interesting to you, check out the full tutorial! Your browser does not support the video tag. It turns linear convolution into circular convolution with the FFT window. Only circular convolution allows to apply the convolution theorem and use the single-tap equalizer.

The CP only works correctly, if it is longer than the channel impulse response. There are several advantages and disadvantages attached to the use for the cyclic prefix within OFDM. The data that is retransmitted can be used if required. Reduces inter-symbol interference: The guard interval introduced by the cyclic prefix enables the effects of inter-symbol interference to be reduced.

Disadvantages Reduces data capacity: As the cyclic prefix re-transmits data that is already being transmitted, it takes up system capacity and reduces the overall data rate. The use of a cyclic prefix is standard within OFDM and it enables the performance to be maintaiend even under conditions when levels of reflections and multipath propagation are high.

The cyclic prefix provides a guard interval to eliminate intersymbol interference from the previous symbol.