Low cost HF receiver using π-constellations, soft convolutional turbo decoder and real channel estimator

In order to define a multicarrier waveform for high frequency military radio communications we analyze new digital techniques. The HF channel is characterized by multipath propagation and Doppler effects which affect the bit error rate. A good way to fight jointly against intersymbol interference and fading environment without increasing the frequency band is to introduce modulation diversity (π constellation) in a multicarrier system. The aim of this paper is to show that such a system associated with a real channel estimator and soft decoder (convolutional turbo decoder) can increase sensitively the transmission performance comparatively to classical modulation. We also demonstrate that a well suited soft decision suboptimal receiver matched to modulation diversity can keep reasonable complexity