%clear all
% close all
% swid = 3;
% pfa = 1e-7;
% np = 1;
% R_1st_frame = 61e3; % Range for first frame
% R0 = 55e3; % range to last frame 
% SNR0 = 9; % SNR at R0
% frame = 0.3e3; % frame size
nfa = log(2) / pfa;
frame
R_1st_frame
range_frame = R_1st_frame:-frame:R0; % Range to each frame
% implement Eq. (2.98)
SNRi = SNR0 + 40 .* log10((R0 ./ range_frame)); 
% calculate the Swerling 5 Pd at each frame
b = sqrt(-2.0 * log(pfa));
if np ==1
    for frame = 1:1:size(SNRi,2)
        a = sqrt(2.0 * 10^(.1*SNRi(frame)));
        pd5(frame) = marcumsq(a,b);
   end
else
   [pd5] = pd_swerling5(pfa, 1, np, SNRi); 
end
% compute additional SNR needed due to fluctuation
for frame = 1:1:size(SNRi,2)
    [Lf(frame),Pd_Sw5] = fluct_loss(pd5(frame), pfa, np, swid); 
end
% adjust SNR at each frame
SNRi = SNRi - Lf;
% compute the farme Pd
for frame = 1:1:size(SNRi,2)
    if(swid==1)
        Pdi(frame) = pd_swerling1 (nfa, np, SNRi(frame));
    end
     if(swid==2)
        Pdi(frame) = pd_swerling2 (nfa, np, SNRi(frame));
    end 
    if(swid==3)
        Pdi(frame) = pd_swerling3 (nfa, np, SNRi(frame));
    end 
    if(swid==4)
        Pdi(frame) = pd_swerling4 (nfa, np, SNRi(frame));
    end
     if(swid==5)
        Pdi(frame) = pd5(frame);
    end
end
Pdc(1:size(SNRi,2)) = 0;
Pdc(1) = 1 - Pdi(1);
%compute the cumulative Pd
for frame = 2:1:size(SNRi,2)
    Pdc(frame) = (1-Pdi(frame)) * Pdc(frame-1);
end
PDC = 1 - Pdc(21)