Rayleigh fading in simulink
You're forgetting the most basic truth of baseband signal processing: Any causal, stable, linear channel $h$ can be just as well represented as baseband system as it can be represented as RF passband system. That is a direct result of both the Fourier transform and the Convolution being a linear operation. 

That's the reason why we can do any sensible Software Defined Radio, and baseband signal processing, in general.