  Orthogonal Frequency Division Multiplexing (OFDM) is a transmission technique
that uses several subcarrier frequencies (multicarrier) that are perpendicular
to each other (orthogonal). This OFDM modulation technique effectively
eliminates Intersymbol Interference (ISI) on a channel caused by the effects of
multipath fading. To overcome this weakness, OFDM uses a guard interval (cyclic
prefix) inserted in its transmission. This paper analyses the effect of
different cyclic prefix lengths on OFDM performance on multipath channels using
Matlab. Here, the cyclic prefix length as the main parameter is varied for the
different number of subscribers. Meanwhile, Bit Error Rate (BER) and Signal
Noise Ratio (SNR) values obtained at the receiver are used to see the system's
performance. Based on our simulation results, the best value of BER is obtained
using a cyclic prefix length of 1/4 with a Fast Fourier Transform (FFT) size of
512.
