In this thesis, we propose the so-called Modified GLRT demodulator for combined channel estimation and data correction for OFDM signals transmitted over a frequency selective channel with unknown channel coefficients. Simulation results confirm that the Modified GLRT can achieve an evidently better performance than the traditional GLRT. In order to reduce the demodulation complexity, we further derive the recursive metric formula based on the Modified GLRT criterion for use of the priority-first search algorithm. This results in a much lower demodulation complexity in comparison with the exhaustive demodulator.