This is matlab code for LTE turbo encoder and log-map based decoder. Simulation result is as above. To run the test, run “turbo_top” in matlab env. Program prompts for some inputs and you can just type return to use default settings. It will take some time to go through several Eb/N0 scenarios and at the end of simulation, BER vs Eb/N0 curve is plotted.
HereĀ is some sample code. Full matlab codeĀ is attached.
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%% TOP % project: TurboCodec % name: Turbo decoder % note: % <Implemention of TurboDecoder under the LTE Standards> % G = [ 1 0 1 1; 1 1 0 1]; % rate = 1/3; % version: v1.0 % %--------------------------------------------------------------------- function [source_code] = lte_turbo_decoder(input_LLR,blocksize,f1,f2,algorithm,iter) %% function description % input_LLR: from demodulater % blocksize: length of interleaver % f1, f2: parameters of interleaver % algorithm: choose a decoding algorithm, % for '1' is Log_Map, % for '2' is Max_Log_Map % iter: number of iteration % % source_code: decoding result %% function initial x = input_LLR(:,1); % z1 = input_LLR(:,2); % z2 = input_LLR(:,3); % %________________________________ if length(x) ~= blocksize+4 disp('ERROR ! length(x) != K+4 '); error('length(x)= %d',length(x)); error('K+4 = %d',blocksize+4); end %%initial values in_s = zeros(blocksize+4,2); in_i = zeros(blocksize+4,2); %SISO_1 in_s(:,1) = x; in_s(:,2) = z1; %SISO_2 % x_i = zeros(blocksize+4,1);% %________________________________________________________ % M = 1; w=blocksize/M; id = M-1; % id from 0 to M-1 id_w = id*w + w -1; init_s = 0; init_i = 0; init_theta = mod( (f1+f2+2*f2*init_s), blocksize); % [adrs_s,adrs_i] = interleaver(init_s,init_i,init_theta,blocksize,id_w,f2); %interleaver outputs two addresses[ adrs_s, adrs_i] %_____________________________________________________________ for i=1:blocksize+4 if i <= blocksize x_i(i) = x( adrs_i(i)+1 ); else x_i(i) = x(i); end end in_i(:,1) = x_i; in_i(:,2) = z2; % %% ____________Call SISO LOG-MAP or MAX-LOG-MAP___________________________ % %_____________________________________________________________ %disp('%_______________go to itel.--------------'); % ex_info = zeros(blocksize+4,1); % ex_info_s = zeros(blocksize+4,1); ex_info_i = zeros(blocksize+4,1); %_____________________________________ for i=1:iter %ex_info_s = zeros(blocksize+4,1); for j=1:blocksize+4 if j <= blocksize % ex_info_s( adrs_i(j)+1 ) = ex_info( adrs_s(j)+1 ); else ex_info_s( j ) = ex_info(j); end end ex_info = ex_info_s; %CALL SISO 1 if algorithm == 2 [soft_out,ex_info]=siso_mlm(in_s,ex_info);%% else [soft_out,ex_info]=siso_lm(in_s,ex_info);% %[soft_out,ex_info] = log_map(in_s,ex_info); end %interleave address: [adrs_s adrs_i ] for j=1:blocksize+4 if j <= blocksize ex_info_i(j) = ex_info( adrs_i(j)+1 ); else ex_info_i(j) = ex_info(j); end end ex_info = ex_info_i; %CALL SISO 2 if algorithm == 2 [soft_out,ex_info]=siso_mlm(in_i,ex_info);%% else [soft_out,ex_info]=siso_lm(in_i,ex_info);% % [soft_out,ex_info] = log_map(in_i,ex_info); end end %.................................... %------------------------------------ %% soft outputs soft_out_s = zeros(blocksize+4,1); % for j=1:blocksize+4 if j <= blocksize % soft_out_s( adrs_i(j)+1 ) = soft_out( adrs_s(j)+1 ); else soft_out_s( j ) = soft_out(j); end end %________________________________________ %% hard decision LLR = soft_out_s; %---------------------------------------- source_code = zeros(blocksize,1); for i=1:blocksize if LLR(i) >= 0 source_code(i) = 1; else source_code(i) = 0; end end % %% ------------end of Decoding--------- |
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