Cyclic Prefix (CP)

Cyclic Prefix (CP)

Cyclic prefix (CP) mitigates multipath fading and inter-symbol interference (ISI) at the price of increasing bandwidth.


Delay spread exceeds symbol time. ISI is the result.

Separate the symbols in time by adding a gap.

Transmission must be continuous. To “fill” the gap, append data from the end of the symbol
to the beginning of the symbol.

CP allows the system to ignore the initial part of each symbol thus avoiding the area that would be
most likely impacted by multipath delay. Data in the CP region of the signal is discarded. CP is set
to 4-6 times the delay spread. WiMAX Forum profiles use a CP of 1/8, meaning that a section of
data equal to 1/8 of the original symbol is used.