This paper investigates various pulseshaping techniques aimed at increasing the spectral efficiency of a Q'PSK system. It will be shown that, other that matched fdter based schemes, time orthogonal modulation schemes can also be used to increase the spectral efficiency of the modulation schemes. Expressions for the spectra and impulse responses of the different pulse shapes used in the various techniques will be presented. The spectral efficiency of the different pulse shaping techniques will be compared using the percentage power captured as a function of bandwidth. Further numerical results will include the maximum intersymbol interference @SI) and cross-symbol interference (CSI) experienced for the different techniques. It is concluded that there exists a large number of pulse shaping techniques which can be used to increase the spectral efficiency of multidimensional modulation schemes.
In this paper, a novel family of root-of-unity tiltered complex spreading sequences is introduced. The new sequences, called Constant-Envelope Root-ofUnity filtered Zero-Cross-Correlatiou (CE-RU-ZCC) sequences, are a non-linear derivative of a family of polyphase sequences originally proposed by Suehiro et al. CE-RU-ZCC sequences can be shown to exhibit superior properties compared to the former, with little correspondence with the original Suehiro source sequences. apart from their desirable autocorrelation properties, which are perfectly retained despite the RU-filtering employed. The sequences are shown to be unique in several ways. Firstly, the unique filtering method results in sequences with perfectly constant envelope when modulated onto quadrature carriers, resulting in superior power efficiency compared to Nyquist-filtered sequences. The sequences secondly exhibit zero cross-correlation amongst the members of a family, and are therefore of particular iuterest in multi-user cellular environments, such as wireless CDMA, where, thirdly, their use results in a significant reduction in multi-user interference (MUI). The new sequences finally have excellent spectral efficiency, their power spectral distributions (densities) being practically equivalent to Nyquist-filtered sequences with sharp spectral roll-off. The paper includes results to verify the various claims made, and compares the CE-RU-ZCC sequences to several of the more commonly known spreading sequence families, such as the hinary Gold family and the family of so-called generalised chirp-like (GCL) sequences originally proposed by Popovif.
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