OFDM system with variable length CP

Abstract EN

Orthogonal Frequency Division Multiplexing (OFDM) is one of recent years multicarrier modulation used in order to combat the Inter Symbol Interference (ISI) introduced by frequency selective radio channel.

The circular extension of the data symbol, commonly referred to as cyclic prefix is one of the key elements in an OFDM transmission scheme.

This paper introduce a study of Variable Length Cyclic Prefix and its influence on the performance of the OFDM system under AWGN channel, flat fading channel and frequency selective channel with different path lengths.

The 64 QAM modulation is used.

The adaptation of CP is done with respect to the delay spread estimation of the channel which is evaluated by means of computer simulation.

The simulation results shows that the performance of the system is increase as the number of path in channel increase, the length of CP must be at least equal to the length of the channel.