Power-Bandwidth Performance of Smoothed Phase Modulation Codes |
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Authors: | Anderson J. Sundberg C.-E. Aulin T. Rydbeck N. |
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Affiliation: | Dept. of Electr. and Computer Eng. and Communications Research Laboratory, McMaster Univ., Hamilton, Ont., Canada; |
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Abstract: | Constant envelope phase varying sinusoids of the formsqrt{2E/T} cos(omega_{c}t + phi(t))are studied, in which the phase functionphi(t)follows some coded pattern in response to data. Power and bandwidth performance are studied for such patterns. The patterns depend on a phase shaping function, a modulation index (h), and a sequence ofM-ary underlying changes in phase which are chosen at random. A cutoff rate-like parameter R0is computed, which guarantees existence of codes at all ratesR < R_{0}bits/T-interval whose error performance varies as exp[-N(R_{0} - R)], whereNis the code word length inT-intervals. Plots of R0are given as a function of interval energyE, the shaping functionhandM. Extensive spectral calculations give the spectra of these phased sinusoids, and their performance is plotted in the power-bandwidth plane. The results give strong evidence that phase codes can approximate any power-bandwidth combination consistent with Shannon's Gaussian channel capacity, and that linear channels are not required for narrow-band transmission. |
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