求（2，1，7）维特比译码器的matlab程序

function out = sovadec( msg, llr, trl, win )
% SOVADEC is an implementation of the soft input soft output Viterbi
% algorithm. The algorithm can be called using
% DEC = SOVADEC( MSG, LLR, TRELLIS, WIN )
% where MSG is the soft input (codeword), LLR is a priori information
% per bit about the bits (log likelihood ratios), TRELLIS is the
% trellis structure describing the convolutional encoder used to
% encode the original information message.
%
% The output of the function is the vector containing the soft
% estimates of the originally encoded information. The implementation
% is able to perform decoding using any trellis structure compatibile
% with the standard Matlab POLY2TRELLIS function.
%
% WIN describes the size of the trellis buffer used to perform the
% Viterbi algorithm. Thus, the decoder estimates the best path through
% the trellis and searches back within