tx_chunk.m

利用QAM调制

% tx_chunk.m
% tx_chunk
data_length = length(data_in_pol); %number of symbols in original input
num_chunks = ceil(data_length/(2*num_carriers)); %2 data on each carrier (real and imaginary)
r = rem(data_length,2*num_carriers);
if r ~= 0
for i = 1:num_carriers*2-r
data_in_pol(data_length+i) = 0; %pad input with zeros to complete last data set
end %speed improve possible
end
% break data into chunks
chunks = zeros(num_chunks,num_carriers); % for speed
for i = 1:num_chunks
% *********************chunk done
for k = 1:num_carriers
chunks(i,k) = data_in_pol(2*num_carriers*(i-1)+k) + data_in_pol(2*num_carriers*(i-1)+k+num_carriers)*j;
end
end
% Padding chunks with zeros so num_carriers and fft_size are compatible
% Once compatible, further spacing is simplified
num_desired_carriers = num_carriers;
num_zeros = 0;
thinking = 1;
while thinking == 1 % Continue if num_carriers and fft_size are not compatible
if rem(fft_size/2,num_desired_carriers) == 0
thinking = 0;
else
num_desired_carriers = num_desired_carriers + 1;
num_zeros = num_zeros + 1;
end
end
padded_chunks = zeros(num_chunks,num_carriers + num_zeros); % for speed
padded_chunks(1:num_chunks,num_zeros + 1:num_carriers + num_zeros) = chunks;
%compute zeros_between
zeros_between = ((fft_size/2) - (num_carriers + num_zeros))/(num_carriers + num_zeros);
spaced_chunks = zeros(num_chunks,fft_size); % for speed - extra room for folding later
%add zeros_between
i = 1;
for k = zeros_between +1:zeros_between +1:fft_size/2
spaced_chunks(1:num_chunks,k) = padded_chunks(1:num_chunks,i);
i = i+1;
end
% folding data to produce an odd function for ifft input
for i = 1:num_chunks
% Note: index = 1 is actually DC freq for ifft -> it does not get copied over y-axis
spaced_chunks(i,fft_size:-1:fft_size/2+2) = conj(spaced_chunks(i,2:fft_size/2));
end