What is OFDMA in 802.11ax and what problem does it solve?

• A. Single-User MIMO; increases range.
• B. Orthogonal Frequency Division Multiple Access; partitions channels into resource units to serve multiple users simultaneously, increasing efficiency.
• C. CSMA/CA; reduces contention.
• D. Beamforming; improves signal in one direction.

Answer: (B)

OFDMA in 802.11ax is the technique of dividing a wireless channel into smaller subchannels called resource units, so the access point can send data to several devices at the same time within one transmission window. This is done by allocating different resource units to different users, allowing parallel transmissions instead of one user occupying the entire channel at a time.

This approach solves the problem of contention and wasted airtime in dense environments. When many devices want to transmit, traditional approaches end up waiting their turn and backoffting, which increases latency and reduces overall throughput. With OFDMA, the AP can schedule multiple users in parallel, making more efficient use of the spectrum and improving both throughput and responsiveness, especially for small, frequent transmissions from many devices.

In short, it’s about sharing the channel efficiently by carving it into resource units for multiple users, rather than letting a single user monopolize the whole channel.