demodulate.m

回波抵消器中常用的几种自适应滤波算法有LMS, NLMS, RLS等算法。对现有主要算法的性能进行了分析

function y = demodulate(x, b, e, h, s2,s4,s16,s64,s256, c2,c4,c16,c64,c256);
% function y = demodulate(x, b, e, s2,s4,s16,s64,s256, c2,c4,c16,c64,c256);
%
% Finds minimum distance estimate of each received signal and returns the
% corresponding binary codeword.  Use a Zero-Forcing approach for convenience
%
%    y - modulated output, in the form of a row vector
%    x - a vector of input symbols, for all the subcarriers (row vector)
%    h - channel value (in frequency) for all subcarriers (64 elements)
%    b - subcarrier bit allocation (64 elements in this matrix, each one
%        corresponding to the number of bits to be allocated to the subcarrier
%        having the same index)
%    e - energy allocation (64 elements in this matrix)
%    s_ - the encoder for a given constellation size
%    c_ - the codewords as vectors of bits for the indices

y=[];

for i = 1:length(b)
    switch b(i)
    case {1}
        [tmp, index] = min(abs(s2-1/h(i)/sqrt(e(i))*x(i)));
        y = [y c2(index,:)];
    case {2}
        [tmp, index] = min(abs(s4-1/h(i)/sqrt(e(i))*x(i)));
        y = [y c4(index,:)];
    case {4}
        [tmp, index] = min(abs(s16-1/h(i)/sqrt(e(i))*x(i)));
        y = [y c16(index,:)];
    case {6}
        [tmp, index] = min(abs(s64-1/h(i)/sqrt(e(i))*x(i)));
        y = [y c64(index,:)];
   case {8}
        [tmp, index] = min(abs(s256-1/h(i)/sqrt(e(i))*x(i)));
        y = [y c256(index,:)];
   otherwise
        index = 0;
   end
end