www.gusucode.com > LTE基带收发仿真系统matlab源码程序 > LTE baseband simulation/trellis.m

    function [next_out, next_state, last_out, last_state] = trellis(g)
%   函数实现的主要功能: 按照输入的生成矩阵 g 生成trellis
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% NextOut(i,1:2): trellis NextOut (systematic bit; parity bit) when input = 0, state = i; NextOut(i,j) = -1 or 1
% NextOut(i,3:4): trellis NextOut  (systematic bit; parity bit) when input = 1, state = i;
% NextState(i,1): next state when input = 0, state = i; NextState(i,i) = 1,...2^m
% NextState(i,2): next state when input = 1, state = i;
% LastOut(i,1:2): trellis LastOut (systematic bit; parity bit) when input = 0, state = i; LastOut(i,j) = -1 or 1
% LastOut(i,3:4): trellis LastOut  (systematic bit; parity bit) when input = 1, state = i;
% LastState(i,1): previous state that comes to state i when info. bit = 0;
% LastState(i,2): previous state that comes to state i when info. bit = 1;
% 
%  Author:		程式小组（徐萌 张妙 张晓庆）
%  Date:		2010-07-11
%  ==========================================================

[n,K] = size(g);
m = K - 1;
max_state = 2^m;

% set up next_out and next_state matrices for systematic code
for state=1:max_state
   state_vector = bin_state( state-1, m );
   
   % when receive a 0
   d_k = 0;
   a_k = rem( g(1,:)*[0 state_vector]', 2 );
   [out_0, state_0] = encode_bit(g, a_k, state_vector);
   out_0(1) = 0;
  
   % when receive a 1
   d_k = 1;
   a_k = rem( g(1,:)*[1 state_vector]', 2 );
   [out_1, state_1] = encode_bit(g, a_k, state_vector);
   out_1(1) = 1;
   next_out(state,:) = 2*[out_0 out_1]-1;
   next_state(state,:) = [(int_state(state_0)+1) (int_state(state_1)+1)];
end

% find out which two previous states can come to present state
last_state = zeros(max_state,2);
for bit=0:1
   for state=1:max_state
      last_state(next_state(state,bit+1), bit+1)=state;
      last_out(next_state(state, bit+1), bit*2+1:bit*2+2) ...
         = next_out(state, bit*2+1:bit*2+2);
   end 
end