Joint time-frequency linear equalization for OFDM signals

Within the context of high-data rate transmissions over time varying multipath fading channels, this article presents a new receiver design for orthogonal frequency division multiplexing (OFDM) systems. The received signal is processed jointly in time and frequency domains. A Discrete Wavelet Transform is applied to the received signal before equalization which is based on the minimum mean square error (MMSE) principle. The paper shows that the proposed receiver is able to work also in highly time-variant channels where a traditional frequency domain equalizer gets very bad performance. Moreover, it is shown that this joint time-frequency equalization is able to exploit time diversity without coding. The performance of the proposed equalizer are shown both in case of perfect channel estimation and in presence of a MMSE linear channel estimator.