STA.m

function [H_STA, Equalized_OFDM_Symbols] = STA(he_LS_Preamble ,y_r, Kset,mod, nUSC, nSym, ppositions, alpha, w, lambda)

%[subcarriers, OFDM_Symbols] = size(y_r(Kset,:));
% H_STA0 = he_LS_Preamble;
% Received_OFDM_Symbols = y_r(Kset,:);
H_STA = zeros(nUSC, nSym);
%H_STA_step4 = zeros(subcarriers, OFDM_Symbols);
Equalized_OFDM_Symbols = zeros(nUSC, nSym);
%ppositions = [7,21, 32,46].';

for i = 1:nSym
    if(i == 1)
        % Step 1: First, the ith received symbol, Received_OFDM_Symbols(i,k) is equalized by the channel estimate, 
        % of the previous symbol. For i = 1, STA(0) is the LS estimate at
        % the preamble.
        Equalized_OFDM_Symbol = y_r(Kset,i)./ he_LS_Preamble;
        Equalized_OFDM_Symbols(:,i) = Equalized_OFDM_Symbol;
        % Step 2.1: Equalized_OFDM_Symbol is demodulated to obtain
        % De_Equalized_OFDM_Symbol.
        % De_Equalized_OFDM_Symbol = qamdemod(sqrt(10) * Equalized_OFDM_Symbol ,16);
        De_Equalized_OFDM_Symbol = wlanClosestReferenceSymbol(Equalized_OFDM_Symbol,mod);
        De_Equalized_OFDM_Symbol(ppositions,:) = [1;1;1;-1]; 
        % Step 2.2: the ith received symbol is divided by
        % De_Equalized_OFDM_Symbol to obtain the initial channel estimate
        Initial_Channel_Estimate = y_r(Kset,i)./ De_Equalized_OFDM_Symbol;
        
        % Step 3: Frequency doamin Averging
        STA_FA = zeros(nUSC,1);
        STA_FA(1,1) = Initial_Channel_Estimate(1,1);
        STA_FA(2,1) = Initial_Channel_Estimate(2,1);
        STA_FA(51,1) = Initial_Channel_Estimate(51,1);
        STA_FA(52,1) = Initial_Channel_Estimate(52,1);
%         alpha = 2;
%         Beta = 2;
%         w = 1 / (2*Beta +1);
%         lambda = -Beta:Beta;
        for j = 3:nUSC -2
           for l = 1: size(lambda,2)
               STA_FA(j,1) = STA_FA(j,1) + (w * Initial_Channel_Estimate(j + lambda(1,l), 1)); 
           end 
        end
        
        %H_STA_step4(:,i) = STA_FA;
       
        % Step 4: Time domain Averging
        STA_TA = (1 - (1/alpha)) .* he_LS_Preamble + (1/alpha).* STA_FA;
        
        % Update H_STA Matrix
        H_STA(:,i) = STA_TA; 
        
    elseif (i > 1)
        % Step 1: First, the ith received symbol, Received_OFDM_Symbols(i,k) is equalized by the channel estimate, 
        % of the previous symbol. 
        Equalized_OFDM_Symbol = y_r(Kset,i)./ H_STA(:,i-1);
        Equalized_OFDM_Symbols(:,i) = Equalized_OFDM_Symbol;
        % Step 2.1: Equalized_OFDM_Symbol is demodulated to obtain
        % De_Equalized_OFDM_Symbol.
        De_Equalized_OFDM_Symbol = wlanClosestReferenceSymbol(Equalized_OFDM_Symbol,mod);
        De_Equalized_OFDM_Symbol(ppositions,:) = [1;1;1;-1]; 
        %De_Equalized_OFDM_Symbol(ppositions,:) = Received_OFDM_Symbols(ppositions,i) ./ [1;1;1;-1]; 
        
        % Step 2.2: the ith received symbol is divided by
        % De_Equalized_OFDM_Symbol to obtain the initial channel estimate
        Initial_Channel_Estimate = y_r(Kset,i)./ De_Equalized_OFDM_Symbol;
        
        % Step 3: Frequency doamin Averging
        STA_FA = zeros(nUSC,1);
        STA_FA(1,1) = Initial_Channel_Estimate(1,1);
        STA_FA(2,1) = Initial_Channel_Estimate(2,1);
        STA_FA(51,1) = Initial_Channel_Estimate(51,1);
        STA_FA(52,1) = Initial_Channel_Estimate(52,1);
%         alpha = 2;
%         Beta = 2;
%         w = 1 / (2*Beta +1);
%         lambda = -Beta:Beta;
        for j = 3:nUSC -2
           for l = 1: size(lambda,2)
               STA_FA(j,1) = STA_FA(j,1) + (w * Initial_Channel_Estimate(j + lambda(1,l), 1)); 
           end 
        end
        
         %H_STA_step4(:,i) = STA_FA;
        
        % Step 4: Time domain Averging
        STA_TA = (1 - (1/alpha)) .*  H_STA(:,i-1) + (1/alpha).* STA_FA;
        
        % Update H_STA Matrix
        H_STA(:,i) = STA_TA;  
    end
end

end