he DC subcarrier is unused in is to support direct conversion receiver architectures. In contrast, nulling DC subcarrier of not the possible in DFT-S-OFDM since it affects the low cubic metric (CM)/PAPR property transmit signal. Direct conversion transmitters and receivers can introduce distortion tor at the carrier frequency (zero frequency or DC subcarrier in baseband) due to local oscilla- rier. leakage. In LTE downlink, this issue is avoided by inclusion of an unused DC subcar- However, for the uplink when using the DFT-S-OFDM waveform, the same solution the may adversely impact the low CM property of the transmitted signal. In order to minimize impact of such distortion on the packet error rate and the CM/PAPR, in LTE, the DC riers subcarrier of the DFT-S-OFDM signal is modulated in the same way as all the other subcar- ing in but the subcarriers are all frequency-shifted by half a subcarrier spacing Af/2, result- the an offset of 7.5 kHz relative to the DC subcarrier. Therefore two subcarriers straddle DC location; hence, the amount of distortion affecting any individual resource block is reduced by half. In LTE, the DC subcarrier was not used because it might be subject to 334 Chapter 3 disproportionally high interference due to local-oscillator leakage and intermodulation pro- ducts. In fact, all LTE devices could receive the full carrier bandwidth, which was centered around the carrier frequency. The NR devices, on the other hand, may not be centered around the carrier frequency and each NR device may have its own DC located at different locations in the carrier, unlike LTE, where all devices typically have their DC coinciding with the center of the carrier. Since special handling of the DC subcarrier would have been difficult in NR, it was decided to exploit the DC subcarrier for data transmission, under- standing that the quality of this subcarrier may be degraded in some conditions. In order to demonstrate the similarities and differences between OFDM and DFT-S-OFDM processing, let's assume that one w