Locally Incoherent Scattering

Dear all,

I am a research student. I am trying to simulate third example from this
paper "Robust Adaptive Beamforming For General Rank Signal Models". I do
not know how to simulate the recieved data at the sensor elements. Is it
that I just use a some number of angles and obtain the corresponding
direction vectors and multiply with the signal? But that seems like
coherent local scattering from the same paper, second example.

Can anybody explain to me the difference between coherent and incoherent
scattering so that I can do my simulations? 

Thanks in advance.

Rdgs,
Stella