OFDMA (Orthogonal Frequency Division Multiple Access) and SC-FDMA (Single Carrier Frequency Division Multiple Access) are two key modulation schemes used in LTE (Long-Term Evolution). These technologies are crucial for managing how data is transmitted over the air between user devices and the network.

OFDMA

• Definition: OFDMA is a multi-user version of the popular OFDM (Orthogonal Frequency Division Multiplexing) digital modulation scheme.
• Usage: It is used in the downlink of LTE, meaning from the base station to the user equipment (UE).
• Function: OFDMA divides the available spectrum into multiple sub-carriers, which can be assigned to different users, allowing for simultaneous data transmission.
• Benefits:
  • Efficiency: High spectral efficiency due to parallel data transmission.
  • Flexibility: Supports dynamic resource allocation.
  • Robustness: Resistant to frequency-selective fading and interference.

SC-FDMA

• Definition: SC-FDMA is a variant of FDMA (Frequency Division Multiple Access) with a single carrier property.
• Usage: It is used in the uplink of LTE, meaning from the UE to the base station.
• Function: SC-FDMA combines the benefits of single carrier modulation with frequency domain equalization, reducing the peak-to-average power ratio (PAPR).
• Benefits:
  • Power Efficiency: Lower PAPR compared to OFDMA, which is advantageous for battery-operated devices.
  • Performance: Provides similar advantages as OFDMA in terms of spectral efficiency and robustness.

Roles in LTE

• Downlink (OFDMA): Ensures efficient and flexible distribution of data from the base station to multiple users, supporting high data rates and robust performance in varying channel conditions.
• Uplink (SC-FDMA): Enhances power efficiency for user devices, extending battery life while maintaining reliable and efficient data transmission to the base station.

Further Readings

• 4G/LTE PHY Processing - RE Map to Antenna