Dynamic Control of CCA Thresholds Based on Frame Priority With QoS Color for IEEE 802.11 Wireless LANs

The IEEE 802.11ax amendment defines Spatial Reuse (SR) operation, enabling parallel transmissions in overlapping basic service set (OBSS) scenarios. Adjusting the clear channel assessment (CCA) threshold of the transmitting node for the OBSS signal, assuming that the SINR of the received frame is sufficient, improves the throughput by expanding the transmission opportunities and avoids exposed node problems. However, depending on node deployment, SR makes it impossible to ensure a high signal-to-interference-to-noise ratio (SINR). This is a significant problem, especially for communications requiring high-quality of service. To address this problem, we propose a method to ensure a high SINR for high-priority frames (QoS frames) when SR is applied. First, we label "QoS Color" on individual frames to indicate the priority level (QoS/best-effort). Then the PHY header indicates whether the frame is a QoS frame. The receiver node references this information and dynamically sets the CCA threshold to lower the threshold for protection in the case of a QoS frame. Second, before transmission, both the CCA threshold and the transmission power are higher for QoS frame transmission than for best-effort frame transmission. This ensures the opportunity to transmit QoS frames. We describe a simple indicator for the above control to change the CCA threshold according to the required throughput of QoS frames. We also confirm the effectiveness of the proposed method by computer simulation.