layers higher than PHY. Part I The mismatch between different services in 5G-and-beyond networks leads to inter-carrier interference (ICI) and thus Chapter 1 focuses on ICI. The authors first provide an overview of OFDM, which has been deemed as the signal waveform for both uplink and downlink transmission for the 5G wireless network. The authors then discuss the impact of inter-ICI on the carrier-to-interference power ratio (CIR) performance of OFDM system. The chapter then introduces four effective ICI cancellation schemes without explicitly estimating ICI coefficients based on mirror-mapping rules and their resulting CIR performance. Finally, the chapter concludes by demonstrating the benefits of the four ICI cancellation schemes for OFDM underwater acoustic (UWA) communications that suffers from strong ICI. Chapter 2 describes single subband matrix form for F-OFDM where all the linear con- volution operations are converted into matrix multiplications to derive a well-channelized signal. The chapter presents the analytical derivations of the in-band interference that is generated due to the mismatch between different services, including ICI, forward inter-symbol interference (ISI), and backward ISI. Furthermore, the chapter presents a low-complexity block-wise parallel interference cancellation (BwPIC) algorithm to tackle the issue caused by the filtering operations. Finally, numerical results are included to show the effectiveness of the BwPIC algorithm. In Chapter 3, the authors describe the INI model of W-OFDM system in the context of mixed numerologies. The chapter establishes a theoretical model of the INI, and derives the analytical expression of its power as a function of the channel frequency response of interfering subcarriers, the spectral distance separating the aggressor and the victim sub- carriers, and the overlapping windows generated by the interferer's transmitter window and the victim's receiver window. Furthermore, the chapter presents numerical results to show the signal-to-interference rat