Hi

Recently I found a paper, which describes how to model rician multipath
channel. The paper is 'Estimation and equalization of multipath
ricianfading channels with stochastic tap coefficients' - Bor sen chen et
al.

In that paper, the channel is modelled as:

h_k(n)=h_k+s_k(n), where index k is for multipath and n is for time.

where h_k is non zero constant mean and s_k(n) is WSSUS

and s_k(n)=a_k . s_k(n-1)+v_k(n)

where v_k(n) is iid complex gaussian process with zero mean and variance
sigma_v^2. and a_k is arbitary constant clsoe to unity.

My doubt: 

1. Is the value of sigma_v^2 controls the variations i.e. how rapidly the
channel is changing.

2. and why s_k(n) is low pass process?

Your opinion matters a lot.

Thanking you.

Chintan