warning('MATLAB:NumPathsChangedPdp',['Using fixed PDP, scmpar.NumPaths changed to ' num2str(scmpar.NumPaths) '.'])
elseif (strcmpi(FixedAnglesUsed,'yes')==1 && N~=6)  % if fixed AoD/AoAs are used, NumPaths must be six
    scmpar.NumPaths=6; N=6;
    warning('MATLAB:NumPathsChangedAoa',['Using fixed AoD/AoAs, scmpar.NumPaths changed to ' num2str(scmpar.NumPaths) '.'])
end



% GENERATION OF RANDOM "BULK" PARAMETERS FOR ALL LINKS
switch (ni)    %%%ni 是什么？？%%%
        
    case (3)    % do the basic thing
        
        % check that M=20
        if (M ~= 20)
            scmpar.NumSubPathsPerPath=20; M=20;
            warning('MATLAB:NumSubPathsChanged','NumSubPathsPerPath is not 20! Using NumSubPathsPerPath=20 instead.')
        end
        
    
        % generate bulk parameters for all links
        bulkpar=generate_bulk_par(scmpar,linkpar,antpar);
        
        % for interpolation
        aods=bulkpar.aods;
        aoas=bulkpar.aoas;
                
        
    case (4)    % do not generate random link parameters, use initial values
        
        % take bulk parameters from input struct
        bulkpar=initvalues;
        
        % for interpolation
        aods=bulkpar.aods;
        aoas=bulkpar.aoas;
        
        
end     



% ANTENNA FIELD PATTERN INTERPOLATION
% Interpolation is computationally intensive, so avoid it if possible.
% Since SCM does not support elevation, dismiss the elevation dimension (for now)
% NOTE: aods/aoas should be given in degrees.
BsGainIsScalar=0;
MsGainIsScalar=0;
if numel(BsGainPattern)>1
    if (strcmp(ScmOptions,'polarized')==1)
        BsGainPatternInterpolated = zeros([2 S size(aods)]); % [polarizations(2) elements links N(6) M(20)] %%%AoDs,defined in scmpars,size[K,N,M]%%%
        BsGainPatternInterpolated(1,:,:,:,:)=feval(InterpFunction,squeeze(BsGainPattern(:,1,1,:)),BsGainAnglesAz,aods, InterpMethod); % V
        BsGainPatternInterpolated(2,:,:,:,:)=feval(InterpFunction,squeeze(BsGainPattern(:,2,1,:)),BsGainAnglesAz,aods, InterpMethod); % H
        BsGainPatternInterpolated=permute(BsGainPatternInterpolated,[3 2 1 4 5]); % [link rx_element polarization path subpath]
    else
        BsGainPatternInterpolated=feval(InterpFunction,squeeze(BsGainPattern(:,1,1,:)),BsGainAnglesAz,aods, InterpMethod); % V only
        BsGainPatternInterpolated=permute(BsGainPatternInterpolated,[2 1 3 4]);
    end
else    % if BsGainPattern is scalar
    if (strcmp(ScmOptions,'polarized')==1)
        BsGainPatternInterpolated=repmat(BsGainPattern, [NumLinks S 2 N M]);    % [link rx_element polarization path subpath]
        BsGainIsScalar=1;        
    else
        BsGainPatternInterpolated=repmat(BsGainPattern, [NumLinks S N M]);
        BsGainIsScalar=1;
    end
end

if numel(MsGainPattern)>1
    if (strcmp(ScmOptions,'polarized')==1)
        MsGainPatternInterpolated=zeros([2 U size(aoas)]);% [polarizations(2) elements links N(6) M(20)]
        MsGainPatternInterpolated(1,:,:,:,:)=feval(InterpFunction,squeeze(MsGainPattern(:,1,1,:)),MsGainAnglesAz,aoas, InterpMethod); % V
        MsGainPatternInterpolated(2,:,:,:,:)=feval(InterpFunction,squeeze(MsGainPattern(:,2,1,:)),MsGainAnglesAz,aoas, InterpMethod); % H
        MsGainPatternInterpolated=permute(MsGainPatternInterpolated,[3 2 1 4 5]); % [link Ms_element polarization path subpath]
    else
        MsGainPatternInterpolated=feval(InterpFunction,squeeze(MsGainPattern(:,1,1,:)),MsGainAnglesAz,aoas, InterpMethod); % V only
        MsGainPatternInterpolated=permute(MsGainPatternInterpolated,[2 1 3 4]);
    end
else    % if MsGainPattern is scalar
    if (strcmp(ScmOptions,'polarized')==1)
        MsGainPatternInterpolated=repmat(MsGainPattern, [NumLinks U 2 N M]);    % [link rx_element polarization path subpath]
        MsGainIsScalar=1;
    else
        MsGainPatternInterpolated=repmat(MsGainPattern, [NumLinks U N M]);
        MsGainIsScalar=1;
    end
end

% Note: The gain patterns at this point have size(MsGainPatternInterpolated) = [link rx_element path subpath]
%  OR
% size(MsGainPatternInterpolated) = [link rx_element polarization path subpath]
% (the same for BsGainPatternInterpolated)

% Do antenna field pattern interpolation for the LOS path
if (strcmpi(ScmOptions,'los')==1)
    if numel(BsGainPattern)>1
        BsGain_Theta_BS= feval(InterpFunction,squeeze(BsGainPattern(:,1,1,:)),BsGainAnglesAz,ThetaBs(:), InterpMethod); % V only
        BsGain_Theta_BS= BsGain_Theta_BS.'; % size()= [NumLinks S]
    else
        BsGain_Theta_BS=repmat(BsGainPattern,[NumLinks S]);
    end
    
    if numel(MsGainPattern)>1
        MsGain_Theta_MS= feval(InterpFunction,squeeze(MsGainPattern(:,1,1,:)),MsGainAnglesAz,ThetaMs(:), InterpMethod); % V only 
        MsGain_Theta_MS= MsGain_Theta_MS.'; % size()= [NumLinks U]
    else
        MsGain_Theta_MS= repmat(MsGainPattern,[NumLinks U]);
    end
else 
    % Set dummy values in case LOS option is not used
    BsGain_Theta_BS=NaN;
    MsGain_Theta_MS=NaN;
    
end





% CHANNEL MATRIX GENERATION
[H delta_t FinalPhases FinalPhases_LOS] = scm_core( scmpar,...
                                                    linkpar,...
                                                    antpar,...
                                                    bulkpar,...
                                                    BsGainPatternInterpolated,...
                                                    BsGain_Theta_BS,...             % gain of LOS path
                                                    MsGainPatternInterpolated,...
                                                    MsGain_Theta_MS,...             % gain of LOS path
                                                    0,...                            % offset time (not used typically)
                                                    BsGainIsScalar,...      
                                                    MsGainIsScalar);

% final phases
bulkpar.subpath_phases=FinalPhases;

% time sampling grid
bulkpar.delta_t=delta_t;


% If path loss and shadowing are to be multiplied into the output
if ( (strcmpi(PathLossModelUsed,'yes')==1) || strcmpi(ShadowingModelUsed,'yes')==1 )
    
    if (size(H,5)==1) % only one link
        if (strcmpi(PathLossModelUsed,'yes')==1)
            H=sqrt(bulkpar.path_losses).*H;   % path loss in linear scale
        end
        
        if (strcmpi(ShadowingModelUsed,'yes')==1)
            H=H*sqrt(bulkpar.shadow_fading);           % shadow fading in linear scale
        end
    else    % if more than one link
        
        siz_H=size(H);
        Hmat=reshape(H,prod(siz_H(1:end-1)),siz_H(end));  % a matrix with NumLinks cols
        if (strcmpi(PathLossModelUsed,'yes')==1)
            pl_mat=diag(sparse(sqrt(bulkpar.path_losses))); 
            Hmat=Hmat*pl_mat;           % multiply path loss into each link
        end
        
        if (strcmpi(ShadowingModelUsed,'yes')==1)
            sf_mat=diag(sparse(sqrt(bulkpar.shadow_fading)));    % shadow fading is in linear scale 
            Hmat=Hmat*sf_mat;           % multiply shadow fading into each link
        end
        
        H=reshape(Hmat,siz_H);      % put back to original size
        
    end
end


% GENERATE OUTPUT
no=nargout;
if (no>1)
    delays=bulkpar.delays;
end

if (no>2)
    switch lower(ScmOptions)
        case {'none','urban_canyon','polarized'}
            full_output=bulkpar;
            
        case ('los')
            bulkpar.Phi_LOS=FinalPhases_LOS;
            full_output=bulkpar;
            
    end
end
    






%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% A function that maps inputs from (-inf,inf) to (-180,180)
function y=prin_value(x)
y=mod(x,360);
y=y-360*floor(y/180);





% %%%%%%%%%%%%%%%%
% %%%%%%%%%%%
% %%%%%%%%
% %%%%%        That's all folks !!!
% %%
% %