Impact of Out-of-Band Emission in OFDM and in DFT-SOFDM

This paper presents statistical properties and the impact of out-of-band emission in Orthogonal Frequency Division Multiplexing (OFDM) and in Discrete Fourier Transform Spread OFDM (DFT-SOFDM) on the link performance. The analysis on the power spectrum density shows that if the signal distortion by a nonlinear power amplifier is not considered, OFDM has the same average power spectrum density as DFT-SOFDM. Hence, the average out-of-band emission (OOBE) power is equal for both systems. However, the fourth- order moment of frequency-domain symbols of DFT-SOFDM is larger than for the case of OFDM, which leads to larger variance of OOBE power in DFT-SOFDM than in OFDM. The link simulation demonstrates that larger variance of OOBE power in DFT-SOFDM does not degrade the link performance of the victim system compared to OFDM as long as the average OOBE power is same. Furthermore, the impact of the intra-system interference due to nonlinear power amplifiers on the link performance is also investigated both for OFDM and DFT-SOFDM systems.