Abstract: The orthogonal frequency division multiplexing (OFDM) modulation technique is widely used in digital transmission systems because of its good performance in withstanding multi-path disturbances and its efficient use of frequency bandwidths. In this article, an OFDM system based on local trigonometric transform (LTT) is proposed in which the spectral density out of the bandwidths decreases rapidly and the adjacent symbols of OFDM remain orthnormal. The fast algorithm based on discrete cosine transform (DCT) and its complexity are obtained and the selection of the best basis is discussed. Theoretical analysis and computer simulation results show that the biterror and anti-Dopplerfrequencyoffset capability of the proposed method outperform the conventional fast Fourier transform (FFT)based system. It can effectively utilize the frequency resources and greatly improve system performance.

Key words: orthogonal frequency division multiplexing, local trigonometric transform, best basis, spectum analysis, Doppler effect