ofdm_block_generation.m

OFDM block code generation using MATLAB

function [ofdm_block,f] = ofdm_block_generation(code_block)

global H

% get N, AMP and M
s = get(H.edit8,'String');
N = st2de(s);
N = round(N);

s = get(H.edit18,'String');
AMP = st2de(s);
AMP = round(AMP);

% get B
s = get(H.edit21,'String');
B = st2de(s);
B = round(B);

s = get(H.edit12,'String');
M = st2de(s);
M = round(M);

% create blank frequency domain
f = zeros(1,N);

% create dc(direct current) and fc(carrier frequency) information
dc = 1;
fc = length(f) + 1;

% will be used for frequency assignments
% the frequencies that will be used are (n * 5) where n is 1, 2, 3, 4, etc.
n = 1;

% assign 8 bits to frequency domain 2 bits at a time
for k = 1:2:7,
   
   % [0 0] is represented by a sine wave
	if code_block(k:k + 1) == [0 0]
   	f(dc + (n * M)) = AMP - j * AMP;
   	f(fc - (n * M)) = AMP + j * AMP;
	end
   
   % [0 1] is represented by a -sine wave
	if code_block(k:k + 1) == [0 1]
   	f(dc + (n * M)) = -AMP - j * AMP;
   	f(fc - (n * M)) = -AMP + j * AMP;
	end

	% [1 0] is represented by a cosine wave
	if code_block(k:k + 1) == [1 0]
   	f(dc + (n * M)) = -AMP + j * AMP;
   	f(fc - (n * M)) = -AMP - j * AMP;
	end
   
   % % [1 1] is represented by a -cosine wave
	if code_block(k:k + 1) == [1 1]
   	f(dc + (n * M)) = AMP + j * AMP;
   	f(fc - (n * M)) = AMP - j * AMP;
   end
   
   % increase frequency assinment
   n = n + 1;
end

% create adjacent frequencies to our frequencies for use in phase shift
% compensation at receiving end
for k = 1:4,
   f(dc + (k * M) + B) = AMP/3;
   f(fc - (k * M) - B) = AMP/3;
end
   

% create ofdm_block from frequency information
ofdm_block = ifft(f);