  The relationship between the transmitted signal and the noiseless received
signals in correlatively changing fading channels is modeled as a nonlinear
mapping over manifolds of different dimensions. Dimension counting argument
claims that the dimensionality of the neighborhood in which this mapping is
bijective with probability one is achievable as the degrees of freedom of the
system.We call the degrees of freedom achieved by the nonlinear decoding
methods the nonlinear degrees of freedom.
