qammod() and fft() function resizing problem

Hi guys, I encountered a problem while using qammod(x,32) function (and higher, like 64 or 256). In fact, the received signal that I get is not in the same scale as the original one, thus making my decoding insufficient (my ber ratio is 0.25 so I guess that he gets like a half of the points correctly, the other half wrong). What can I do to resize the plot?

The received signal is after using the fft() function. The fft function makes my signal not as "stretched" as it should be.

Answer 1

[Arthi Sathyamurthi]

Hello Marcin,QAM modulation modulates input signal by the specified modulation order, combining bits of input, mapping and modulating it. Thus, the length of input data will be log2(Modulation order) smaller than the modulated bits. Hence at the receiver make sure to demodulate the signal using qamdemod and then try to decode the data.