  Orthogonal frequency division multiplexing (OFDM) signals with rectangularly
windowed pulses exhibit low spectral confinement. Two approaches usually
referred to as pulse-shaping and active interference cancellation (AIC) are
classically employed to reduce the out-of-band emission (OOBE) without
affecting the receiver. This paper proposes a spectral shaping method that
generalizes and unifies these two strategies. To this end, the OFDM carriers
are shaped with novel pulses, referred to as generalized pulses, that consist
of the ones used in conventional OFDM systems plus a series of cancellation
terms aimed at reducing the OOBE of the former. Hence, each generalized pulse
embeds all the terms required to reduce its spectrum in the desired bands. This
leads to a data-independent optimization problem that notably simplifies the
implementation complexity and allows the analytical calculation of the
resulting power spectral density (PSD), which in most methods found in the
literature can only be estimated by means of simulations. As an example of its
performance, the proposed technique allows complying with the stringent PSD
mask imposed by the EN 50561-1 with a data carrier loss lower than 4%. By
contrasts, 28% of the data carriers have to be nulled when pulse-shaping is
employed in this scenario.

Signal Processing