Theoretical analysis of the pilot tones assisted COFDM system over fast multipath fading channels

Fast fading is the commonly encountered phenomenon for an OFDM system which has a long symbol duration (equivalent to the system having a large number of subcarriers under a certain data rate). It introduces the interchannel interference (ICI) which leads to the loss of orthogonality between subcarriers. This gives rise to an irreducible error floor of the system´s bit error rate (BER). We analyze the statistical properties of ICI caused by the fast fading and derive the BER formula of the system assisted by the pilot tones over a time-varying multipath fading channel. In order to minimize the variance of the estimation error samples taken from the pilots were filtered using a narrow band filter whose bandwidth equals to the maximum Doppler frequency. The channel estimation method using pilots allow us to calculate the values of the ICI and serve as a good reference for performing coherent demodulation of each subcarrier