Blind equalization of an HF channel for a passive listening system

Wireless channels often distort a signal beyond the point of reliable demodulation. To account for this problem receivers incorporate an equalizer whose objective is to remove the distortion introduced by the medium of transmission. Typically, the equalizer requires knowledge of the transmitted signal to adequately adapt to remove this distortion. This introduces overhead into the signal effectively reducing the data throughput rate. Blind equalizers do not require this prior knowledge of the transmitted signal allowing for the removal of information that is known by the receiver a priori.

In most of the research in blind equalizers simulated signals and test channels are used. Little to no attention is paid to using real world transmissions in the algorithms analysis. While modeling is a crucial step in the development of an effcient algorithm it is not the only step. Accurate models accounting for all the disturbances and noise in the real world are to complex to be effcient. One particular case of this is the HF channel. The high frequency (HF) channel is particularly diffcult to blindly equalize because of its noisy environments and it long path delays. This work looks into the use of blind equalizers for HF signals and focuses a large amount of the analysis on real world HF transmissions.