SPECTRAL EFFICIENCY ANALYSIS OF NEW QUADRATURE OVERLAPPED MODULATIONS OVER BAND‐LIMITED NON‐LINEAR CHANNELS

Abstract

In this paper, two new quadrature overlapped modulations, the overlapped minimum shift keying (OMSK) and minimum shift keying triangular cosine (MSKTC), are introduced for their promising spectral efficiency over band-limited non-linear channels. They possess fast power spectral density (PSD) side lobe reduction rates over either a linear or a (band-limited) non-linear channel and their PSD side lobe regeneration caused by channel non-linearity is under much better control than that of the offset QPSK, minimum shift keying (MSK) and staggered quadrature overlapped raised cosine (QORC) modulations (a reported quadrature overlapped modulation). An effective algorithm is introduced to study spectral efficiency for various (both overlapped or non-overlapped) modulations over band-limited non-linear channels. Third-order Butterworth and Chebyshev filters with various cut-off frequencies are considered as band-limiting transmitter filters. It is concluded that the impairment (to signal spectral efficiency) caused by channel non-linearity can be minimized by using the proposed modulations. © 1997 by John Wiley & Sons, Ltd.