Regarding the use of the DC subcarrier in LTE, I understand that the reason why it is not used for downlink transmission is that it may be subject high interference due to local-oscillator leakage. This means that we add an extra central carrier to our OFDM signal that is unused.
However, in the uplink there is no unused DC, and the strategy to avoid OL leakage is that the center frequency of an uplink carrier is located between two uplink subcarriers. So the signal is shifted 7.5 kHz with respect to the central frequency. This is justified to allow a full bandwidth allocation and enjoy the low PAPR of the DFTS-OFDM modulation (SC-FDMA) used in uplink.
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But, why not using that second strategy in downlink as well?
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Regarding NR, DC subcarriers seems to be used in any case because each NR UE may have its DC located at different locations in the carrier. But then, how is OL leakage avoided?