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decoder_simple_MAP.asv
资源名称：Turbomatlab.rar　[点击查看]
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上传日期：2013-06-30
资源大小：2149k
文件大小：5k
源码类别：

传真(Fax)编程

开发平台：

Matlab

decoder_simple_MAP.asv：源码内容
  1. % 内容概述：利用硬件化的方式实现MAP译码
  2. % 创 建 人：朱殿荣
  3. % 单    位：南京邮电大学，通信工程系
  4. % 创建时间：2005年7月6日
  5. % 最后改时间：
  6. % 参考文献：《数字通信－－基础与应用》
  8. clear;
  9. x=[1.5 0.5 -0.6];
  10. y=[0.8 0.2 1.2];
  11. alpha=zeros(4,4);   %前向状态量度，4种可能状态，约束长度为3.zeros(S,k)
  12. alpha(1,1)=1;       %前向状态量度初始值为1，其他为0
  13. belta=zeros(4,4);   %后向状态量度，4种可能状态，约束长度为3.zeros(S,k)
  14. belta(1,4)=1;       %后向状态量度末尾值为1，其他为0
  15. gamma0=zeros(4,4); %后向状态量度，4种可能状态，约束长度为3,输入0.zeros(S,k)
  16. gamma1=zeros(4,4); %后向状态量度，4种可能状态，约束长度为3,输入1.zeros(S,k)
  17. pi=0.5;           %先验概率
  19. %k=1---------------------------------------------
  20. k=1;
  21. gamma0(1,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,1)));
  22. gamma1(1,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,1)));
  23. gamma0(2,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,2)));
  24. gamma1(2,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,2)));
  25. gamma0(3,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,3)));
  26. gamma1(3,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,3)));
  27. gamma0(4,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,4)));
  28. gamma1(4,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,4)));
  29. %for s=1:4
  30. %    gamma0(s,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,s)));
  31. %    gamma1(s,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,s)));
  32. %end
  33. %k=2---------------------------------------------
  34. k=2;
  35. gamma0(1,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,1)));
  36. gamma1(1,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,1)));
  37. gamma0(2,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,2)));
  38. gamma1(2,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,2)));
  39. gamma0(3,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,3)));
  40. gamma1(3,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,3)));
  41. gamma0(4,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,4)));
  42. gamma1(4,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,4)));
  43. alpha(1,k)=gamma0(1,k-1)*alpha(1,k-1)+gamma0(3,k-1)*alpha(3,k-1);%后一项为0
  44. alpha(2,k)=gamma1(1,k-1)*alpha(1,k-1)+gamma1(3,k-1)*alpha(3,k-1);%后一项为0
  45. %k=3---------------------------------------------
  46. k=3;
  47. gamma0(1,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,1)));
  48. gamma1(1,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,1)));
  49. gamma0(2,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,2)));
  50. gamma1(2,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,2)));
  51. gamma0(3,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,3)));
  52. gamma1(3,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,3)));
  53. gamma0(4,k)=pi*exp(x(k)*(-1)+y(k)*(trellis_simple(-1,4)));
  54. gamma1(4,k)=pi*exp(x(k)*(1)+y(k)*(trellis_simple(1,4)));
  55. alpha(1,k)=gamma0(1,k-1)*alpha(1,k-1)+gamma0(3,k-1)*alpha(3,k-1);%后一项为0
  56. alpha(2,k)=gamma1(1,k-1)*alpha(1,k-1)+gamma1(3,k-1)*alpha(3,k-1);%后一项为0
  57. alpha(3,k)=gamma0(2,k-1)*alpha(2,k-1)+gamma0(4,k-1)*alpha(4,k-1);%后一项为0
  58. alpha(4,k)=gamma1(2,k-1)*alpha(2,k-1)+gamma1(4,k-1)*alpha(4,k-1);%后一项为0
  59. %k=4---------------------------------------------
  60. k=4;
  61. alpha(1,k)=gamma0(1,k-1)*alpha(1,k-1)+gamma0(3,k-1)*alpha(3,k-1);
  62. alpha(2,k)=gamma1(1,k-1)*alpha(1,k-1)+gamma1(3,k-1)*alpha(3,k-1);
  63. alpha(3,k)=gamma0(2,k-1)*alpha(2,k-1)+gamma0(4,k-1)*alpha(4,k-1);
  64. alpha(4,k)=gamma1(2,k-1)*alpha(2,k-1)+gamma1(4,k-1)*alpha(4,k-1);
  65. % for belta,from k=3------------------------
  66. k=3;
  67. belta(1,k)=gamma0(1,k)*belta(1,k+1)+gamma1(2,k)*belta(2,k+1);%后一项为0
  68. belta(3,k)=gamma0(3,k)*belta(1,k+1)+gamma1(2,k)*belta(2,k+1);%后一项为0
  69. % for belta,from k=2------------------------
  70. k=2;
  71. belta(1,k)=gamma0(1,k)*belta(1,k+1)+gamma1(1,k)*belta(2,k+1);%后一项为0
  72. belta(3,k)=gamma0(3,k)*belta(1,k+1)+gamma1(3,k)*belta(2,k+1);%后一项为0
  73. belta(2,k)=gamma0(2,k)*belta(3,k+1)+gamma1(2,k)*belta(4,k+1);%后一项为0
  74. belta(4,k)=gamma0(4,k)*belta(3,k+1)+gamma1(4,k)*belta(4,k+1);%后一项为0
  75. % for belta,from k=1------------------------
  76. k=1;
  77. belta(1,k)=gamma0(1,k)*belta(1,k+1)+gamma1(1,k)*belta(2,k+1);
  78. belta(3,k)=gamma0(3,k)*belta(1,k+1)+gamma1(3,k)*belta(2,k+1);
  79. belta(2,k)=gamma0(2,k)*belta(3,k+1)+gamma1(2,k)*belta(4,k+1);
  80. belta(4,k)=gamma0(4,k)*belta(3,k+1)+gamma1(4,k)*belta(4,k+1);
  82. %calculate LLR-----------------------------------
  83. k=1;
  84. numerator=0;
  85. denominator=0;
  86. numerator=numerator+alpha(1,k)*gamma1(1,k)*belta(2,k+1);
  87. denominator=denominator+alpha(1,k)*gamma0(1,k)*belta(1,k+1);
  88. llr(k)=log10(numerator/denominator);
  90. %calculate LLR-----------------------------------
  91. k=2;
  92. numerator=0;
  93. denominator=0;
  94. numerator=numerator+alpha(1,k)*gamma1(1,k)*belta(2,k+1);
  95. numerator=numerator+alpha(2,k)*gamma1(2,k)*belta(4,k+1);
  96. denominator=denominator+alpha(1,k)*gamma0(1,k)*belta(1,k+1);
  97. denominator=denominator+alpha(2,k)*gamma0(2,k)*belta(3,k+1);
  98. llr(k)=log10(numerator/denominator);
  100. %calculate LLR-----------------------------------
  101. k=3;
  102. numerator=0;
  103. denominator=0;
  104. numerator=numerator+alpha(1,k)*gamma1(1,k)*belta(2,k+1);
  105. numerator=numerator+alpha(2,k)*gamma1(2,k)*belta(4,k+1);
  106. numerator=numerator+alpha(3,k)*gamma1(3,k)*belta(2,k+1);
  107. numerator=numerator+alpha(4,k)*gamma1(4,k)*belta(4,k+1);
  108. denominator=denominator+alpha(1,k)*gamma0(1,k)*belta(1,k+1);
  109. denominator=denominator+alpha(2,k)*gamma0(2,k)*belta(3,k+1);
  110. denominator=denominator+alpha(3,k)*gamma0(3,k)*belta(1,k+1);
  111. denominator=denominator+alpha(4,k)*gamma0(4,k)*belta(3,k+1);
  112. llr(k)=log10(numerator/denominator);