I'm trying to simulate a multipath channel to see how it would affect my signal. So considering my channel is LTI, I can model it as an FIR filter. I've been reading Telecommunication Breakdown and looking at some examples and there's one thing I don't quite understand in page 183 (Chapter 9: Stuff happens, Section 9.4: Other Impairments: "More What Ifs")
if cdi < 0.5, % channel ISI mc=[1 0 0 ] ; % distortion−free channel elseif cdi<1.5 , % mild multipath channel mc=[1 zeros (1 ,M) 0.28 zeros (1, 2.3*M) 0.11 ] ; el se % harsh multipath channel mc=[1 zeros (1, M) 0.28 zeros (1, 1.8*M) 0.44 ] ; end
cdi is a parameter to choose between distortion-free, mild or harsh multipath channel and
mc is the resulting FIR filter. What I don't understand is:
- What's the point on inserting zeros in between?
- How does that make it mild or harsh?
Would you mind explaining that to me? Thanks