ificantly larger than that of OFDM. The reason is that the smooth transition edges of overlapping windows in W-OFDM system lead to more rapid decrease of INI compared to OFDM. However, we can find that the SIR in edge subcarriers of W-OFDM and OFDM is almost the same, which reveals that in small GB cases, the spectral distance is the dominant factor of the INI level compared with the roll-off length of the window. It was mentioned in [18, 23] that a larger transmitter window roll-off portion offers better spectral containment, and a larger receiver window roll-off portion brings benefit 3 Windowed OFDM for Mixed-Numerology 5G and Beyond Systems Mean SIR of subband 1 with Af(1) = 15 kHz (up) Mean SIR of subband 2 with Af (2) = 30 kHz (down) Mean SIR of subband 1 with Af(1) = 15 kHz (up) Mean SIR of subband 2 with Af(2) = 60 kHz (down) Figure 3.10 SIR for different transmit window roll-off lengths and receiver window roll-off lengths. (a) Af(1) = 15 kHz, Af(2) = 30 kHz and (b) Af(1) = 15 kHz, Af(2) = 60 kHz. for reducing ACI. Nevertheless, to avoid ISI and keep a fixed CP overhead, increasing the roll-off length of a transmit window leads to a decrease in receiver window roll-off length. In Figure 3.10, we evaluate the average SIR of two numerologies with different values of MTX (1) and Mrx, (2) in order to find how Tx and Rx roll-off lengths will affect the INI level. In this study, GB = 60 kHz is considered, and MTX + MRX = 7% is set for numerology 1 and 2. In Figure 3.10a, we set Af(1) = 15 kHz, Af(2) = 30 kHz, while Af(1) = 15 kHz, Af(2) = 60 kHz are adopted in Figure 3.10b. As shown in Figure 3.10, both larger MOX for interferer and larger MRX for victim offer SIR gain for numerology 1. In Figure 3.10a, when =0 in subband 2, increasing Max you from 0% to 7% (i.e. decreasing MTX (1) from 7% 3.A Appendix to 0%) brings 1.2 dB SIR gain for numerology 1 whereas when MRX (1) = 0% in subband 1, increasing from 0% to 7% leads to a 0.4 dB gain for the average SIR of numerology 1. A similar phenomenon can be observed in