LOMAS: Latency-driven OFDMA Scheduling Design in Wi-Fi 6 Networks

The IEEE 802.11ax standard, known as Wi-Fi 6, introduces a key feature, OFDMA (Orthogonal Frequency Division Multiple Access), designed for high-efficiency Wi-Fi. It enables concurrent transmissions for multiple clients through channel multiplexing, reducing contention in dense environments and offering low latency (LL) with consistent data streams. However, our experimental study reveals that while OFDMA can reduce latency, dynamic scheduling is required to consistently meet latency requirements. Moreover, it may perform worse than conventional single-user transmissions in terms of throughput. We thus develop LOMAS (Latency-driven OfdMA Scheduling), a practical latency-driven design for OFDMA, specifically aimed at supporting LL clients in downlink transmissions while maximizing transmission efficiency and ensuring client fairness. Implemented and evaluated using a COTS Wi-Fi 6 NIC, LOMAS consistently outperforms other solutions, meeting latency requirements for LL clients while maintaining fairness with only a minor throughput trade-off. Especially for mobile LL clients, LOMAS satisfies 35.4-78.3% more packets with just a 0.8% throughput loss, given a 20 ms latency requirement. These findings confirm the practicality and effectiveness of LOMAS.