On Spectral Efficiency of OFDM Signals Based on Windowing

摘要

We discuss the spectral efficiency of orthogonal frequencydivisionmultiplexing (OFDM) signals widely adopted in practical systemsfrom a viewpoint of their power spectral density property. Since the conventionalOFDM does not make use of pulse shaping filter, its out-ofband(OOB) spectrum may not be negligible especially when the numberof subcarriers is small. Thus, in practice, windowing is applied to mitigateOOB emission by smoothing the transition of consecutive OFDM symbols,but its effectiveness has not been well investigated. Furthermore, OFDMsignal suffers from nonlinear distortion associated with its high signal peakto-average power ratio (PAPR), which also leads to OOB radiation. Weexamine how power amplifier nonlinearity affects the spectral efficiencybased on the theoretical results developed in the literature.