This book focuses on the design of low-complexity iterative receivers in high spectral efficiency communication systems, especially under frequency-selective fading channels. Specifically, it combines multi-carrier faster-than-Nyquist (MFTN) signaling, spectrally efficient frequency division multiplexing (SEFDM), and index modulation (IM) to study the hybrid message passing based low-complexity iterative receivers, the frequency-domain joint channel estimation and equalization (FDJCEE) alg...