Abstract: Method and system for allowing abandoning pilot signals use and for increasing the immunity to Doppler Effect influence in OFDMA based wireless mobile communication systems and as a result, make them more efficient. This is carried out by transmitting N orthogonal I and Q values of symbols, N times on N frequencies, where N is a power of two. In order to be able to select the desired signal from a mixture of N signals, signs of symbol of each signal vary according to one of N-order Walsh functions.

Abstract: The present invention is directed to a method for canceling the Doppler shift, multi-path propagation, delays, and long time selective fading influences of phase and/or amplitude modulated signals carried by RF sub-carriers, without requiring pilot signals. The number of m=2n, over which individual datum is transmitted in each communication channel, is determined. Pairs of Walsh functions are selected from a Walsh-Hadamard matrix such that each function is not selected more than once. Each signal is partitioned to its I factor and Q factor and coding each I and Q factors of the signals by the pair functions. A corresponding phase and amplitude is allocated for each sub-carrier wherein the amplitude and phase values are determined by the data that is transmitted, the digital modulation scheme or inverse spectral transformation, and signs of both corresponding elements taken from the pair Walsh functions.