topnetwork
% Chan 算法，利用3BS對MS進行定位；
% CHAN_3BS:
% 參數說明：
% Noise: 測距誤差方差.
% R： 小區半徑.
% Also see: Chan_3BS.
% 參數檢測:
if nargout ~=1,
error('Too many output arguments!');
end
if nargin ~= 3,
error('input arguments error!');
end
% 算法開始
MS = R*MSP;
BS = R*NetworkTop(3);
% A矩陣:
X21 = BS(1,2) - BS(1,1);
X31 = BS(1,3) - BS(1,1);
Y21 = BS(2,2) - BS(2,1);
Y31 = BS(2,3) - BS(2,1);
A = inv([X21,Y21;X31,Y31]);
% B矩陣:
R1 = sqrt((BS(1,1) - MS(1))^2 + (BS(2,1) - MS(2))^2);
R2 = sqrt((BS(1,2) - MS(1))^2 + (BS(2,2) - MS(2))^2);
R3 = sqrt((BS(1,3) - MS(1))^2 + (BS(2,3) - MS(2))^2);
R21 = R2 - R1 + MeaNoise(Noise); % 需要加噪聲
R31 = R3 - R1 + MeaNoise(Noise);
B = [R21;R31];
% C矩陣:
K1 = BS(1,1)^2 + BS(2,1)^2;
K2 = BS(1,2)^2 + BS(2,2)^2;
K3 = BS(1,3)^2 + BS(2,3)^2;
C = 0.5*[R21^2 - K2 + K1; R31^2 - K3 + K1];
% 壹元二次方程的系數：
a = B'*A'*A*B - 1;
b = B'*A'*A*C + C'*A'*A*B;
c = C'*A'*A*C;
% 方程的兩個根：
root1 = abs((-b + sqrt(b^2 - 4*a*c))/(2*a));
root2 = abs((-b - sqrt(b^2 - 4*a*c))/(2*a));
% 檢驗方程的根：
if root1 < R,
EMS = -A*(B*root1 + C);
else
EMS = -A*(B*root2 + C);
end
% 輸出結果：
if nargout == 1,
X = EMS;
else
disp(EMS);
end