Doppler spread estimation for OFDM systems using Phase Difference method in Rayleigh fading channels

A method of estimating the Doppler spread in Orthogonal Frequency Division Multiplexing (OFDM) systems, known as Phase Difference method, is described. Channel estimation is performed in time domain over several OFDM symbols, which popularly performed in frequency domain. Channel frequency responses are affected by AWGN and propagation delay, and Rayleigh fading distributed. As a result, Doppler spread estimation is useful to improve Channel Impulse Response (CIR) performance. Furthermore, estimation bias is analyzed and error correcting modified method is advised to reduce estimation precision. From simulation results, it can be concluded that the greater Doppler spread is, the smaller number of pilot symbols are needed to form a circle on the constellation diagram, and conversely. The range of normalized Doppler shift that can be estimated is 0.0117-0.2997. For SNR = 10-30 dB, the error is ± 64.72%, whereas for SNR = 40-80 dB SNR, the error is ± 35.81%.