To limit the influence of ICI on OFDM systems completely by hardware we would have to have transmitters and receivers with under 0.1ppm frequency stability. This would drastically increase the cost and complexity of hardware.Thus quite a big part of the OFDM software in the receiver deals with frequency correction using the cyclic prefix, but also reference or pilot signals sent with the signal.
The cyclic prefix (CP) consists of the last part of the following symbol. The size of the cyclic prefix field depends on the system and can even vary within one system. Cyclic prefixes are used by all modern OFDM systems and their sizes range from 1/4 to 1/32 of a symbol period. Most receiver structure use the cyclic prefix to make an initial estimation of time and frequency synchronization.
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