Blind Channel Estimation Using Maximum Likelihood in OFDM Systems
new blind channel estimation scheme for OFDM systems is based on the Maximum Likelihood (ML) principle. The approach combines different modulation schemes on adjacent subcarriers, such as BPSK and QPSK, to resolve phase ambiguity. By avoiding the use of second- and higher-order statistics, a very fast convergence rate is achieved. In this paper the Maximum Likelihood (ML) is used for symbol-time and carrier-frequency offset estimator in Orthogonal Frequency-Division Multiplexing (OFDM) systems. It also shows the results for bit error rate and signal to noise ratio. In the uplink of such systems users must be aligned in time and frequency to maintain the orthogonality of the subcarriers.