uploaded code and data files

awgn_channel.m

@@ -0,0 +1,9 @@
+function received = awgn_channel(modulated, snr)
+% INPUT: 
+% modulated: transmitted modulated signal
+% snr: value of the signal to noise ratio 
+% OUTPUT: 
+% received: noise added modulated signal that appears at the receiver
+
+received = awgn(modulated, snr, 'measured'); 
+end

convolutional_coding.m

@@ -0,0 +1,12 @@
+function y = convolutional_coding(bit_stream, G)
+% INPUT: 
+% bit_stream = uncoded bit stream vector 
+% G = generator matrix 
+% OUTPUT: 
+% y = channel coded bit stream 
+
+y = conv2(bit_stream, G);
+y = rem(y, 2);
+[row, col] = size(y);
+y = reshape (y, 1, row * col);
+end

demodulation.m

@@ -0,0 +1,65 @@
+function bit_stream = demodulation(modulation_name, received, Rb, k, amp, freq)
+% INPUT: 
+% modulation_name: can be 'BASK', 'BPSK', 'QPSK'
+% received: modulated signal received from channel 
+% Rb = bit rate 
+% k = samples per bit
+% amp = amplitude of the modulated signal
+% scaler for BPSK and QPSK, vector ([max min]) for BASK
+% freq = carrier frequency of the modulated signal 
+% OUTPUT: 
+% bit_stream = demodulated bit stream 
+
+n = length(received) / k; % n = number of bits 
+Tb = 1/Rb; 
+Fs = k * Rb; 
+Ts = 1/Fs; 
+t = 0 : Ts : n*Tb-Ts;
+bit_stream = []; 
+
+switch modulation_name
+ case 'BASK'
+ a0 = amp(1); 
+ a1 = amp(2);
+ r = received .* sin(2*pi*freq(1)*t);
+ r = reshape(r, k, n); 
+ yd = mean(r); 
+ threshold = (a0 + a1) / 4; 
+ bit_stream = (yd >= threshold);
+
+ case 'BPSK'
+ r = received .* sin(2*pi*freq(1)*t); 
+ r = reshape(r, k, n); 
+ yd = mean(r); 
+ threshold = 0;
+ bit_stream = (yd >= threshold);
+
+ case 'QPSK'
+ M = 4; 
+ bn = log2(M);
+ t = 0 : Ts : bn*Tb-Ts;
+ A = amp(1); 
+ f = freq(1); 
+ space = length(t);
+ for i = 1:space:length(received)
+ sig = received(i:(i-1)+space); 
+ r1 = sig .* sin(2*pi*f*t); 
+ r2 = sig .* cos(2*pi*f*t); 
+ ai = mean(r1); 
+ aq = mean(r2); 
+ phi = (0:M-1) * 2 * pi ./ M; 
+ distance = (A*cos(phi) - 2*ai).^2 + (A*sin(phi) - 2*aq).^2; 
+ [~, min_ind] = min(distance);
+ min_ind = min_ind - 1; 
+ sym = de2bi(min_ind, bn); 
+ bit_stream = [bit_stream sym];
+ end
+
+ otherwise
+ disp('WARNINGS [ :( ] . . . '); 
+ disp(['"', modulation_name, '" : Modulation is not supported! ONLY BASK, BPSK, QPSK are supported.']);
+end
+
+% converting logical array to double vector array
+bit_stream = double(bit_stream); 
+end

huffman_decoding.m

@@ -0,0 +1,24 @@
+function decoded_msg = huffman_decoding(unique_symbol, code_word, bit_stream)
+% INPUT: 
+% unique_symbol: string of the unique symbols 
+% code_word: cell array of code to represent each probability of the symbols 
+% bit_stream: message bit stream that has to be decoded 
+% OUTPUT: 
+% decoded_msg = decoded message 
+
+decoded_msg = []; 
+
+% minimum code word length 
+i_min = min(cellfun('length', code_word));
+
+% bit stream pointer 
+ptr = 1; 
+for i = i_min:length(bit_stream)
+ if isempty(find(strcmp(code_word, char(bit_stream(ptr:i) + '0')), 1)) ~= 1
+ ind = find(strcmp(code_word, char(bit_stream(ptr:i) + '0')), 1); 
+ decoded_msg = [decoded_msg char(unique_symbol(ind))]; 
+ ptr = i + 1; 
+ i = i + i_min; 
+ end
+end
+end

huffman_encoding.m

@@ -0,0 +1,38 @@
+function code_word = huffman_encoding(prob)
+% INPUT: 
+% prob = a vector of probability of the unique symbols 
+% OUTPUT: 
+% code_word = cell array of huffman code word for each unique symbol
+
+n = length(prob); 
+code_word = cell(1, n);
+
+% from descending order to ascending order 
+prob = fliplr(prob); 
+
+% initializing code word for n = 1 case 
+if n == 1
+ code_word{1} = '1'; 
+end
+x = zeros(n, n); 
+x(:, 1) = (1:n)'; 
+
+for i = 1:n-1
+ temp = prob; 
+ [~, min1] = min(temp); 
+ temp(min1) = 1; 
+ [~, min2] = min(temp); 
+ prob(min1) = prob(min1) + prob(min2); 
+ prob(min2) = 1; 
+ x(:, i+1) = x(:, i); 
+ for j = 1:n
+ if x(j, i+1) == min1
+ code_word(j) = strcat('0', code_word(j)); 
+ elseif x(j, i+1) == min2
+ x(j, i+1) = min1; 
+ code_word(j) = strcat('1', code_word(j));
+ end
+ end
+end
+code_word = fliplr(code_word); 
+end

main_code.m

@@ -0,0 +1,131 @@
+clc, clear, close all; 
+start = tic; 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "System Properties" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+modulation_name = 'BASK'; 
+samples_per_bit = 40; 
+Rb = 1000; 
+amp = [1 0];
+freq = 1000; 
+snr = 10; 
+Generator = [1 1 1; 1 0 1]; 
+shift = 1; 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Reading Text Data File" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Reading data: '); 
+file = fopen('Data/source_data.txt');
+text = fread(file, '*char')';
+fclose(file);
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Source Statistics" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+fprintf('Source statistics: '); 
+tic
+[unique_symbol, probability] = source_statistics(text); 
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Huffman Encoding" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+fprintf('Huffman encoding: '); 
+tic 
+code_word = huffman_encoding(probability); 
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Stream Generator" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Stream generator: '); 
+bit_stream = stream_generator(unique_symbol, code_word, text);
+input = bit_stream;
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Channel Coding" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Channel coding: '); 
+
+channel_coded = convolutional_coding(bit_stream, Generator);
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Modulation" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Modulation: ');
+modulated = modulation(modulation_name, channel_coded, Rb, samples_per_bit, amp, freq); 
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Channel" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Channel: ');
+received = awgn_channel(modulated, snr); 
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Demodulation" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Demodulation: ');
+bit_stream = demodulation(modulation_name, received, Rb, samples_per_bit, amp, freq);
+toc
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Channel Decoding" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Channel decoding: ');
+bit_stream = viterbi_decoder(bit_stream, Generator, shift); 
+output = bit_stream; 
+toc
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Huffman Decoding" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Huffman decoding: ');
+decoded_msg = huffman_decoding(unique_symbol, code_word, bit_stream); 
+toc 
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Writting the Received Data" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+tic
+fprintf('Writing data: ');
+f = fopen('Data/received.txt','w+');
+fprintf(f, decoded_msg);
+fclose(f);
+toc
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%% "Time & Error Calculation" %%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+fprintf('Total execution time: ');
+toc(start); 
+
+Error = sum(abs(input - output)); 
+disp(['Total Bit Error: ' num2str(Error)]); 

modulation.m

@@ -0,0 +1,63 @@
+function modulated = modulation(modulation_name, bit_stream, Rb, k, amp, freq)
+% INPUT: 
+% modulation_name = can be 'BASK', 'BPSK', 'QPSK'
+% bit_stream = string of bits 
+% Rb = bit rate 
+% k = samples per bit
+% amp = amplitude of the modulated signal
+% scaler for BPSK and QPSK, vector ([max min]) for BASK
+% freq = carrier frequency of the modulated signal 
+% OUTPUT: 
+% modulated = modulated signal of the bit stream 
+
+modulated = []; 
+
+% converting string to vector 
+N = length(bit_stream); 
+
+% line coding 
+line_code = repelem(bit_stream, k); 
+
+Tb = 1/Rb; % bit duration 
+Fs = k * Rb; % sampling frequency 
+Ts = 1 / Fs;
+time = 0 : Ts : N*Tb-Ts;
+
+switch modulation_name
+ case 'BASK'
+ carrier = sin(2*pi*freq*time); 
+ a1 = amp(1); 
+ a0 = amp(2);
+ line_code = a1 * line_code + a0 .* (line_code==0); 
+ modulated = line_code .* carrier;
+
+ case 'BPSK'
+ a = amp(1);
+ carrier = sin(2*pi*freq*time); 
+ line_code = a .* (line_code == 1) + (-a) .* (line_code == 0); 
+ modulated = line_code .* carrier;
+
+ case 'QPSK'
+ M = 4; 
+ bn = log2(M); 
+ t = 0 : Ts : bn*Tb-Ts;
+
+ % Gray code generation 
+ x = 0 : M-1; 
+ code = bin2gray(x, 'psk', M); 
+ gray_code = de2bi(code, bn, 'left-msb'); 
+
+ for i = 1:bn:length(bit_stream)
+ sym = bit_stream(i:i+bn-1);
+ index = find(ismember(gray_code, sym, 'rows'), 1); 
+ val = bi2de(gray_code(index, :)); 
+ phi = 2 * pi * val / M; 
+ modulated = [modulated amp(1)*sin(2*pi*freq*t + phi)];
+ end
+
+ otherwise
+ fprintf('\n'); 
+ warning(['"', modulation_name, '" Modulation is not supported! ONLY BASK, BPSK, QPSK are supported.']);
+ return; 
+end
+end

source_statistics.m

@@ -0,0 +1,17 @@
+function [unique_symbol, probability]=source_statistics(text)
+% INPUT: 
+% text = input text data string 
+% OUTPUT: 
+% unique_symbol = string of unique symbols 
+% probability = probability of each unique symbols 
+
+unique_symbol = unique(text); 
+count_symbol = histc(text, unique_symbol);
+
+% calculating each symbol probability 
+probability = count_symbol / length(text); 
+
+% sorting probability in descending order 
+[probability, index] = sort(probability, 'descend'); 
+unique_symbol = unique_symbol(index);
+end

stream_generator.m

@@ -0,0 +1,17 @@
+function bit_stream = stream_generator(unique_symbol, code_word, msg)
+% INPUT: 
+% unique_symbol = a string of unique symbols 
+% code_word = cell array of code to represent each probability of the symbols
+% OUTPUT: 
+% msg = message that has to be converted into bit stream 
+
+bit_stream = '';
+increment = length(char(unique_symbol(1))); 
+for i = 1:increment:length(msg)
+ index = strfind(unique_symbol, msg(i:i+increment-1)); 
+ bit_stream = [bit_stream char(code_word(index))];
+end
+
+% converting string bit stream to double vector array 
+bit_stream = double(bit_stream - double('0')); 
+end