Power spectral density in LTE?

Question

I am trying to simulate an OFDM signal with LTE specifications. After taking ifft of the modulated symbols I want to plot the power specteral density of the signal. Somehow the power spectral density is not correct if I take directly the ifft output. My question is what needs to be done to the output of ifft samples to get the correct PSD.

Answer 1

You can plot the absolute value after taking the IFFT of modulated data (may be 1200 for 100 RB or less for other configuration)with Nfft=2048. Always take care for placing data about the DC subcarrier which is Zero at the 1024th location and place 600 modulated data symbol just before and other 600 just after the DC subcarrier, and place simply zeros to other locations to make total length 2048.And for making the power normalised you should multiply this array by (2048/sqrt(1200)).