MAP Algorithm

Implementation of MAP Algorithm.

Description

This program includes:
[5 7] convolutional code (encoder) + BPSK + AWGN + MAP (decoder). It evaluates Bit Error Rate and plots it versus SNR(signal to Noise Ratio).

• Required Products: Communications System Toolbox
• MATLAB release: MATLAB 6.5 (R13)

[Vu Martin]

How is about in Simulink ?

[Ugo Seux]

Limited, doesn't seem to accept á priori information. Does it work with other than R=1/2 codes?

[h xd]

 

[li lini]

 

[ali sabery]

hello That was very useful for me.Thanks BR

[Hammad Dilpazir]

Dear Bahadir Gedikbey it is a good method but i think it has some mistake, The formula used to compute "gama" in your code is
gama11(k)=exp((-(r(i)-x111)^2-(r(i+1)-x112)^2)/2/sigma);
            gama12(k)=exp((-(r(i)-x121)^2-(r(i+1)-x122)^2)/2/sigma);
            gama23(k)=exp((-(r(i)-x231)^2-(r(i+1)-x232)^2)/2/sigma);
            gama24(k)=exp((-(r(i)-x241)^2-(r(i+1)-x242)^2)/2/sigma);
            gama31(k)=exp((-(r(i)-x311)^2-(r(i+1)-x312)^2)/2/sigma);
            gama32(k)=exp((-(r(i)-x321)^2-(r(i+1)-x322)^2)/2/sigma);
            gama43(k)=exp((-(r(i)-x431)^2-(r(i+1)-x432)^2)/2/sigma);
            gama44(k)=exp((-(r(i)-x441)^2-(r(i+1)-x442)^2)/2/sigma);

but i think it should be like

gama11(k)=exp((-(r(i)-x111)^2-(r(i+1)-x112)^2)/(2*sigma)); %see moons book page 595 equation or eq 14.21
            gama12(k)=exp((-(r(i)-x121)^2-(r(i+1)-x122)^2)/(2*sigma));
            gama23(k)=exp((-(r(i)-x231)^2-(r(i+1)-x232)^2)/(2*sigma));
            gama24(k)=exp((-(r(i)-x241)^2-(r(i+1)-x242)^2)/(2*sigma));
            gama31(k)=exp((-(r(i)-x311)^2-(r(i+1)-x312)^2)/(2*sigma));
            gama32(k)=exp((-(r(i)-x321)^2-(r(i+1)-x322)^2)/(2*sigma));
            gama43(k)=exp((-(r(i)-x431)^2-(r(i+1)-x432)^2)/(2*sigma));
            gama44(k)=exp((-(r(i)-x441)^2-(r(i+1)-x442)^2)/(2*sigma));

the sigma should be divided instead of multiplied
Thanks and to check it
[e-mail]

[Shahriar Rahman]

Dear Bahadir,

I want to implement Systematic encoder like kafes = poly2trellis(3,[7 5], 7). For that your code has to changed. And I changed it accordingly. But the performance is poor. Can you please help me?

[e-mail]

[dragos paslaru]

Hello!I want to introduce a non-recursive and nonsistematic code first, then i want a systematic and nonrecursive code.what should i modify in this : kafes=poly2trellis(3,[5 7]);