Efficient joint OFDMA and MU-MIMO user scheduling in IEEE 802.11ax

Determine computationally efficient, standard-compliant algorithms for user scheduling under joint OFDMA and MU-MIMO in IEEE 802.11ax WiFi, where the optimal user set varies across resource units due to frequency selectivity and each user may be assigned to at most one resource unit.

Background

IEEE 802.11ax enables concurrent transmissions via both OFDMA and MU-MIMO, which introduces a combinatorial user-group and resource-unit allocation problem. Frequency selectivity causes the optimal MU-MIMO user set to vary across resource units, and standard constraints (e.g., each user assigned to at most one RU; MU-MIMO permitted only on sufficiently large RUs) couple decisions across frequency.

The search space for MU-MIMO user selection is exponential, and evaluating zero-forcing beamforming rates per subcarrier is computationally demanding. These factors make the design of scalable, near-optimal schedulers a core unresolved challenge.