You would know of SC-OFDM because this is the waveform that we use in current LTE. If you are familiar with SC-FDMA, you can easily understand DFT-s-OFDM(Discrete Fourier Transform spread Orthogonal Frequency Division Multiplexing) . High level view of DFT-s-OFDM waveform generation is illustrated as follows. You would notice that this is almost same as high level SC-OFDM process.

Below is the breakdown and brief description of each of the blocks

• Serial to Parallel Conversion:
• The input data stream (usually modulated symbols such as QPSK, 16-QAM, or 64-QAM) is split into multiple parallel streams.
• This step organizes the data to be processed simultaneously.
• DFT (K-point):
• A K-point Discrete Fourier Transform is applied to the input symbols.
• This step spreads the input symbols across the frequency domain.
• This operation is what gives DFT-s-OFDM its "single-carrier-like" properties because it creates a frequency-domain representation of the signal while retaining low PAPR characteristics.
• Subcarrier Allocation:
• The DFT output is mapped onto a subset of the available subcarriers in the frequency domain.
• The unused subcarriers remain empty (zero-padding) to fit the desired bandwidth and avoid interference.
• This ensures efficient spectral usage and helps in uplink resource allocation.
• IFFT (M-point):
• An Inverse Fast Fourier Transform (IFFT) is applied to the mapped subcarriers, converting the signal back to the time domain.
• This creates the OFDM waveform that is transmitted over the air.
• Here, M is typically larger than K, as only a subset of the subcarriers are occupied.
• Parallel to Serial Conversion:
• The parallel time-domain samples are converted back into a single serial data stream for transmission.

Key Characteristics of DFT-s-OFDM:

DFT-s-OFDM combines the benefits of both single-carrier and multi-carrier techniques. This hybrid approach leverages the efficiency and flexibility of OFDM while addressing its limitations, such as high Peak-to-Average Power Ratio (PAPR), through the integration of a Discrete Fourier Transform (DFT) step. By preserving single-carrier-like characteristics and enabling efficient resource allocation, DFT-s-OFDM ensures optimal performance in power-constrained mobile devices. Additionally, its inherent robustness to multipath fading makes it well-suited for maintaining reliable communication in diverse and dynamic wireless environments.

• Low PAPR:
• Compared to standard OFDM, DFT-s-OFDM has a lower Peak-to-Average Power Ratio, which is crucial for efficient power amplifier operation in the uplink.
• Single-Carrier-like Behavior:
• The DFT step introduces frequency-domain spreading, making the transmitted signal behave similarly to single-carrier transmission, which is beneficial for uplink transmission where mobile devices have limited power.
• Efficient Resource Utilization:
• The subcarrier allocation step allows flexible and efficient assignment of frequency resources, making DFT-s-OFDM ideal for LTE’s uplink scheduling.
• Robustness to Multipath:
• Like standard OFDM, DFT-s-OFDM provides robustness against multipath fading, as the IFFT converts the signal to the time domain while maintaining orthogonality between subcarriers.

Reference

[1]  Frequency-Domain Equalization and Single-Carrier Transmission in OFDM Framework by Markku Renfors