我用MATLAB的simulink做无线信道建模，求误码率出了问题

zhouyou10086

建模完成后，程序源代码出错，如下，关键是我没用到sum函数啊，求高手指点
for i=1:length(x)
       SNR=x(i);
       sim('jiawu');
          y(i)=mean(BitErrorRate);
end
semilogy(x,y);
??? Function 'sum' is not defined for values of class 'struct'.

Error in ==> sum at 41
  [varargout{1:nargout}] = builtin('sum', varargin{:});

Error in ==> mean at 29
  y = sum(x)/size(x,dim);