How do OFDMA and MU-MIMO work together in WiFi 6?

WiFi 6 (802.11ax) combines OFDMA and MU-MIMO for efficient multi-user access. OFDMA divides the channel into Resource Units (RUs): smallest 26 tones (~2 MHz), largest 996 tones (~80 MHz) in 80 MHz channel. Multiple users served simultaneously on different RUs, reducing latency for small packets. MU-MIMO serves up to 8 users (up/down) on the same RU using spatial streams. Combined operation: Channel can be divided into RUs, with MU-MIMO within each RU. Scheduler decides OFDMA vs MU-MIMO based on traffic size, user capabilities, and channel conditions. Trigger-based uplink OFDMA coordinates transmissions. BSS coloring reduces interference from neighboring networks. TWT (Target Wake Time) schedules transmissions for power saving. This combination significantly improves efficiency in dense deployments.