correlated Rayleigh MIMO channel coefficient

can anyone explain me this code?I am looking for explanation of this code, what it means and how to run it

function hh=channel_coeff(NT,NR,N,Rtx,Rrx,type)
% correlated Rayleigh MIMO channel coefficient
% Inputs:
% NT : number of transmitters
% NR : number of receivers
% N : legnth of channel matrix
% Rtx : correlation vector/matrix of Tx
% e.g.) [1 0.5], [1 0.5;0.5 1]
% Rrx : correlation vecotor/matrix of Rx
% type : correlation type: 'complex' or 'field'
% Outputs:
% hh : NR x NT x N correlated channel

% uncorrelated Rayleigh fading channel, CN(1,0)
h=sqrt(1/2)*(randn(NT*NR,N)+j*randn(NT*NR,N));
if nargin<4, hh=h; return; end % Uncorrelated channel
if isvector(Rtx), Rtx=toeplitz(Rtx); end
if isvector(Rrx), Rrx=toeplitz(Rrx); end
% Narrow band correlation coefficient
if strcmp(type,'complex')
C = chol(kron(Rtx,Rrx))'; % Complex correlation
else
C = sqrtm(sqrt(kron(Rtx,Rrx))); % Power (field) correlation
end
% Apply correlation to channel matrix
hh=zeros(NR,NT,N);
for i=1:N, tmp=C*h,i); hh,:,i)=reshape(tmp,NR,NT); end