I am working on modelling some FM transmitted signals, and I'm trying to figure out how to model the effects of multipath channels. The most obvious method is to delay the signal by some integral number of samples and then add it to itself (with some attenuation factor). But, this is obviously not very realistic, since 1 sample's worth of time is a long time for a radio wave (at least at a reasonable sample rate). It would be nice to be able to delay the signal by a fraction of a sample. However, I don't know how to do this... Can anyone enlighten me? I am fairly new to the DSP field, I'm sure this isn't a particularly challenging task.
Also, is this actually a good method for modelling multipath effects?