Noncoherent equalization for multipulse modulation

Noncoherent equalization of inter-symbol interference (ISI) channels for nonorthogonal multipulse modulation (NMM) is introduced. Multipulse modulation (a simple example of which is FSK) is usually seen as a nonlinear modulation technique, so that equalization for such modulation schemes is described as being difficult by Lee and Messerschmitt (1994). However, Varanasi (see Proc. IEEE Intl. Conf. Personal Wireless Communications (ICPWC97), Mumbai (Bombay), India, 1997) showed that ISI can indeed be effectively mitigated in baseband channels, such as with the linear and decision feedback, zero-forcing, multi-input, multi-output (MIMO) equalizers proposed in that work. One of the advantages of multipulse modulation is of course the option of noncoherent reception in bandpass communications. In this paper, we obtain a carrier phase-independent MIMO zero-forcing equalizer. Detection at the output of the zero-forcing equalizer is equivalent to M-ary noncoherent one-shot detection of nonorthogonal signals with unequal energies, a problem that was solved previously by the author and Russ (see Proc. IEEE ICC´97, Montreal, Canada, 1997). Any one of the three noncoherent detection rules obtained therein can be used as post-equalizer units depending on whether the energies of the transmitted waveforms are known or unknown at the receiver