Constant envelope space-time modulation trellis code design for Rayleigh flat fading channel

Abstract

A constant envelope space-time modulation seems to be an attractive option especially for very high frequency and mobile applications because of its resistance to nonlinear distortion. The paper first analyzes the mean squared distance of the constant envelope space-time modulated signal in a Rayleigh slowly flat fading spatial diversity channel with independent coefficients. It is shown that the distance evaluation depends on both the modulator trellis and the distance evaluation trellis. The latter has special properties regarding its free paths. These properties, a critical path and the distance increments behavior, are the basis for the space-time trellis code design. The paper identifies the trellis code design rules minimizing the mean squared distance. The critical path is shown to be the determining factor.