Characterizing the intercarrier interference of non-orthogonal Spectrally Efficient FDM system

The proposal of Spectrally Efficient Frequency Division Multiplexing (SEFDM) system has added a new dimension for enhancing spectral utilization. SEFDM systems defy the orthogonality principle defined for Orthogonal Frequency Division Multiplexing (OFDM) systems by employing closely packed overlapped subcarriers to save bandwidth. Nevertheless, the loss of orthogonality results in intercarrier interference (ICI) which impede signal extraction. In this paper, the ICI in the SEFDM system is characterized through mathematical derivations and computer modeling and is shown to rely mainly on the main system parameters in terms of the level of bandwidth savings and number of subcarriers. Closed form formulas for the ICI for the continuous time and discrete time SEFDM system are derived which can be used in designing mitigation techniques, in particular, the design of informed detection algorithms.