Cyclic equalization for nonlinear modulations

The paper is focused on the application of cyclic equalization to the received signal sampled prior to demodulation. This technique, particularly, has been proposed for nonlinear modulations, namely FSK, where the nonlinear dependence of the received signal on the modulating sequence precludes the use of conventional equalization, being controlled through data observation. In cyclic equalization, in fact, the particular structure of the training sequence makes it possible to employ a straightforward control of the signal distortion by means of frequency observation. The technique can be particularly suitable for frequency-hopping transmissions since it can provide fast equalizer set up each time a new radio channel is engaged. Simulation analysis, carried out for FSK and linear modulations over the HF radio channel, yields to consider this proposal an attractive solution for all those systems in which the only alternative to compensate for the effects of channel distortion is the complex MLSE.