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New Waveform Candidate : DFT-s-OFDM

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DFT-s-OFDM (Discrete Fourier Transform spread Orthogonal Frequency Division Multiplexing) is a novel modulation scheme designed to overcome some of the limitations of traditional OFDM (Orthogonal Frequency Division Multiplexing). Let's dive into the technical details:

1. Traditional OFDM:

Firstly, let's briefly discuss traditional OFDM:

  • OFDM is a modulation technique widely used in modern wireless communication systems, including 4G LTE, Wi-Fi, and digital broadcasting. In OFDM, data is transmitted over multiple subcarriers that are orthogonal to each other.
  • Each subcarrier is modulated using a symbol, and these symbols are combined to form the OFDM signal. The orthogonality between subcarriers helps in reducing interference among them.

2. Limitations of Traditional OFDM:

  • Peak-to-Average Power Ratio (PAPR): One of the significant challenges with OFDM is the high PAPR, which requires power amplifiers to operate inefficiently, leading to increased costs and reduced battery life in mobile devices.
  • Inter-symbol Interference (ISI) and Inter-Carrier Interference (ICI): In some scenarios, especially in mobile environments with frequency-selective fading, ISI and ICI can degrade the performance of OFDM systems.

3. DFT-s-OFDM:

DFT-s-OFDM introduces modifications to the traditional OFDM to address its limitations:

  • Spread Transform: Instead of using a standard Fourier transform (as in OFDM), DFT-s-OFDM employs a spread transform. This transform helps in reducing the PAPR by spreading the energy of each subcarrier across multiple subcarriers.
  • Reduced PAPR: By spreading the energy across multiple subcarriers using the spread transform, DFT-s-OFDM can achieve a lower PAPR compared to traditional OFDM. This reduces the complexity and cost of power amplifiers.
  • Robustness to ISI and ICI: The use of a spread transform can also make the system more resilient to ISI and ICI, especially in challenging propagation environments.

4. Technical Aspects:

  • Spread Transform: The exact nature of the spread transform can vary depending on the specific implementation of DFT-s-OFDM. It could involve spreading the data symbols in the frequency or time domain, or both, depending on the requirements.
  • Processing Complexity: While DFT-s-OFDM offers advantages in terms of PAPR reduction and robustness, it may introduce additional processing complexity due to the spread transform. Efficient algorithms and hardware implementations are essential to ensure that the benefits outweigh the complexity.

Conclusion:

DFT-s-OFDM is a promising modulation scheme designed to address some of the limitations associated with traditional OFDM, such as high PAPR and susceptibility to ISI and ICI. By introducing a spread transform, DFT-s-OFDM aims to achieve lower PAPR, improved spectral efficiency, and enhanced robustness in challenging communication environments. As with any modulation scheme, the practical implementation, performance evaluation, and standardization play crucial roles in determining its widespread adoption in real-world applications.