Wireless Communication Basics
Which describes OFDMA (orthogonal frequency-division multiple access)?
- AA scheme in which a single terminal uses all subcarriers in each transmission
- BA scheme in which each terminal is assigned a different spreading code and communicates at the same time on the same frequency
- CA scheme that divides OFDM subcarriers into groups and assigns each time-frequency division to a different terminal, communicating with several terminals at once
Show answer and explanation
Answer: C. A scheme that divides OFDM subcarriers into groups and assigns each time-frequency division to a different terminal, communicating with several terminals at once
OFDMA is a multiple-access scheme that assigns OFDM subcarriers to different terminals in units divided by time and frequency (such as resource blocks in 4G LTE and 5G NR). Terminals with little data can be given few units, and frequencies where a terminal's channel conditions are good can be assigned to it, so many terminals are served efficiently. Besides 4G LTE (downlink) and 5G NR for mobile phones, it has been used in wireless LANs since IEEE 802.11ax.
- A. This describes OFDM used by a single terminal, which is how conventional wireless LANs such as 802.11a/g/n worked.
- B. This describes CDMA.
- C. Correct. Groups of subcarriers are assigned to each terminal.