Blind channel estimation in OFDM systems

Ayas, Mehmet Akif
In this thesis, we have studied blind channel estimation methods for single-input-multiple-output (SIMO) orthogonal frequency division multiplexing (OFDM) systems in time and frequency domain, in which the cross relation between the channel gains and a single snapshot of the received signal on each subcarrier is utilized. We have performed blind channel estimation for uncorrelated and correlated Rayleigh fading channel pairs using time and frequency methods in OFDM systems with one-transmitting, two-receiving antennas. Using time and frequency methods, blind channel estimation simulations have been run for different channel lengths, different number of subcarriers and different modulation schemes; i.e., QPSK and 16-QAM. Channel estimation results have been used to calculate the normalized root mean squared errors. Besides, using Zero Forcing (ZF) and Minimum Mean Squared Error (MMSE) equalizers with Maximum Likelihood (ML) estimators in receiver side, we have estimated symbols that are used for transmission and bit error probabilities have been calculated with the estimated symbols. These simulations have been repeated with one-transmitting, three-receiving and one-transmitting, four-receiving antennas in order to observe the effect of antenna diversity over the SIMO-OFDM systems.