Single Carrier Frequency Division Multiple Access (SC-FDMA) is a frequency-division multiple access scheme used in the uplink of Long-Term Evolution (LTE) networks. It was developed to address the high Peak-to-Average Power Ratio (PAPR) problems associated with Orthogonal Frequency Division Multiple Access (OFDMA).
Types/Categories
Types of SC-FDMA
- Localized SC-FDMA (LFDMA): Allocates contiguous sub-carriers for a user’s signal.
- Interleaved SC-FDMA (IFDMA): Distributes the sub-carriers across the entire spectrum in an interleaved manner.
Key Events
- 2004: Initial development of SC-FDMA as a low PAPR alternative to OFDMA.
- 2008: Adoption of SC-FDMA for LTE uplink in 3GPP Release 8.
Detailed Explanations
SC-FDMA Technical Aspects
SC-FDMA can be viewed as a discrete Fourier transform (DFT)-spread version of OFDMA. The key stages in SC-FDMA processing include:
- Modulation: Input data is modulated using QPSK, 16-QAM, or 64-QAM.
- DFT Spread: The modulated symbols undergo DFT to spread the data.
- Subcarrier Mapping: Transformed data symbols are mapped onto subcarriers.
- IDFT Operation: The subcarriers are transformed back to the time domain using inverse DFT.
- Cyclic Prefix Addition: A cyclic prefix is added to prevent inter-symbol interference.
Mathematical Model
Given an input vector \( x = [x_0, x_1, \ldots, x_{N-1}] \):
- DFT Spread: \( X_k = \sum_{n=0}^{N-1} x_n e^{-j2\pi kn/N} \)
- Subcarrier Mapping: \( Y_m \) where \( Y_m \) is assigned to subcarriers.
- IDFT: \( y_n = \frac{1}{N} \sum_{m=0}^{N-1} Y_m e^{j2\pi mn/N} \)
graph LR
A[Input Data] --> B[Modulation]
B --> C[DFT]
C --> D[Subcarrier Mapping]
D --> E[IDFT]
E --> F[Cyclic Prefix Addition]
F --> G[Transmission]
Importance and Applicability
SC-FDMA is crucial in modern telecommunications for several reasons:
- Lower PAPR: Reduced power consumption in mobile devices.
- Efficiency: Improved spectral efficiency, making it suitable for high data rate applications.
Examples and Considerations
Example Scenario
In an LTE network, user equipment (UE) employing SC-FDMA ensures efficient uplink transmission, preserving battery life and maintaining consistent data rates.
Considerations
- Complexity: SC-FDMA’s processing is more complex due to DFT operations.
- Flexibility: Offers more flexibility in subcarrier allocation compared to OFDMA.
Related Terms
- OFDMA: Orthogonal Frequency Division Multiple Access, used in LTE downlink.
- PAPR: Peak-to-Average Power Ratio, a measure of signal’s power fluctuation.
Comparisons
SC-FDMA vs. OFDMA
- PAPR: SC-FDMA has a lower PAPR compared to OFDMA.
- Application: SC-FDMA is used for uplink, while OFDMA is used for downlink in LTE.
Interesting Facts
- SC-FDMA is also referred to as DFTS-OFDM (Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing).
Inspirational Stories
The adoption of SC-FDMA in LTE uplink significantly improved the efficiency and battery life of mobile devices, directly impacting the user experience and paving the way for future advancements in wireless communication technology.
Famous Quotes
“Innovation distinguishes between a leader and a follower.” - Steve Jobs
Proverbs and Clichés
“Necessity is the mother of invention.”
Expressions
“Paving the way for future innovations.”
Jargon and Slang
- DFT Spread: Distribution of data using discrete Fourier transform.
- Cyclic Prefix: A portion of the transmitted signal added to combat inter-symbol interference.
FAQs
What is SC-FDMA?
Why is SC-FDMA used in LTE uplink?
References
- 3GPP TS 36.211 - Physical channels and modulation.
- 3GPP TS 36.300 - E-UTRA and E-UTRAN overview.
Summary
SC-FDMA plays a crucial role in the efficient operation of LTE uplink channels. Its lower PAPR compared to OFDMA makes it ideal for mobile devices, enhancing battery life and ensuring consistent data transmission rates. The adoption of SC-FDMA is a testament to the continuous innovation in telecommunications, ensuring that networks can handle increasing data demands while maintaining user satisfaction.
