modem.oqpskmod - converting array of different values to array of 1s and 0s
hi i was doing the following in matlab
values = [0;1;0;0;1;0;1;0]; % can contain only 0s and 1s
h = modem.oqpskmod;
y = modulate(h, values);
g = modem.oqpskdemod(h);
z = demodulate(g,y);
BER = sum(logical(values(:)-z(:)))/numel(values); % thanks to gnovice!
before calculating the BER, do you think that i have to convert the array z into array of 1s and 0s only... for example, my z may consist of 3s and 0s, then do i have to convert all numbers bigger than 0 to 1s and all 0s unc开发者_JS百科hanged. so that at the end i get the correct comparison for the BER?
This depends on how you want to do the comparison of the input and output. The code I gave you for computing the BER will count any difference between the input and output as an error. So, a value of 3 for an output and a corresponding 1 for an input are counted as different.
If you want to compute the BER in another way, here are a couple more options you could use. Each of these assumes values
contains only zeroes and ones:
Count any non-zero output value as a 1: In this case, you would use the function LOGICAL to convert any non-zero value of
z
(i.e. the values 3, 0.5, -1, etc.) to a 1, leaving the values that are exactly zero unchanged:BER = sum(values(:)-logical(z(:)))/numel(values);
Count positive values as 1 and negative values as 0: This solution just uses a comparison operator instead of LOGICAL:
BER = sum(values(:)-(z(:) > 0))/numel(values);
You may also want to try setting the 'OutputType'
property of the modem.oqpskdemod
object to 'bit'
to ensure a binary output. Then you shouldn't have to do anything to z
:
...
g = modem.oqpskdemod(h,'OutputType','bit');
z = demodulate(g,y);
BER = sum(values(:)-z(:))/numel(values);
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