Abstract
A new power efficient technique, that combines
$\boldsymbol{N}$
-level multipulse pulse-position modulation with
$\boldsymbol{L}$
-level quadrature-amplitude modulation, denoted by
$\boldsymbol{N}$
MPPM-
$\boldsymbol{L}$
QAM, is proposed. Its constrained power efficiency is derived and characterized. It is shown that the proposed combination provides a superior technique that is both power and spectral efficient simultaneously. The constrained power efficiencies of variations to this technique are considered and characterized as well. These include combining multilevel pulse-amplitude modulation with
$\boldsymbol{L}$
QAM (
$\boldsymbol{N}$
PAM-
$\boldsymbol{L}$
QAM). The obtained constrained power efficiencies are compared numerically to that of traditional
$\boldsymbol{L}$
QAM and MPPM-
$\boldsymbol{L}$
QAM techniques. Our results disclose that proposed
$\boldsymbol{N}$
MPPM-
$\boldsymbol{L}$
QAM is the most power/spectral efficient technique. For example, at spectral efficiency constraints of
$\boldsymbol{2.5}$
and
$\boldsymbol{4.2}$
bs
$\boldsymbol{^{-1}}$
/Hz/pol, the corresponding constrained power efficiencies of proposed
$\boldsymbol{N}$
MPPM-
$\boldsymbol{L}$
QAM technique are higher by about
$\boldsymbol{4.87}$
and
$\boldsymbol{3.62}$
dB, respectively, than that of traditional
$\boldsymbol{L}$
QAM. In addition, the results reveal that
$\boldsymbol{N}$
PAM-
$\boldsymbol{L}$
QAM scheme has increased power and spectral efficiencies compared to that of traditional
$\boldsymbol{N}$
PAM, but its power efficiency is less than that of traditional
$\boldsymbol{L}$
QAM.
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