Multi-carrier modulation scheme used for LTE downlink transmission.
Description
Orthogonal Frequency Division Multiple Access (OFDMA) is the multi-carrier transmission scheme used for the LTE downlink. It divides the available bandwidth into many narrow orthogonal subcarriers (15 kHz each).
OFDMA provides high spectral efficiency, resistance to multipath fading, and flexible resource allocation. Resources are allocated in time-frequency blocks called Resource Blocks (RBs).
Purpose & Motivation
OFDMA was chosen for LTE to achieve:
- High spectral efficiency needed for 4G speeds - Robustness against frequency-selective fading - Flexible bandwidth allocation (1.4 to 20 MHz) - Simple frequency-domain equalization - Easy integration with MIMO
Key Features
- ✓15 kHz subcarrier spacing
- ✓Cyclic prefix for ISI mitigation
- ✓Resource Block allocation
- ✓Support for QPSK/16QAM/64QAM
- ✓Frequency-domain scheduling