Low-latency communications in Wi-Fi

Real-Time Applications (RTAs), such as virtual and augmented reality, industrial automation, and cloud gaming, typically require high transmission reliability (packet delivery probability at least 99.9–99.999%) and low delay (1–10 ms). Modern Wi-Fi networks often struggle to meet such stringent requirements.

First, Wi-Fi operates in unlicensed spectrum and relies on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol, which can increase delays due to collisions and waiting periods between station transmissions. As a result, devices cannot transmit while the channel is busy with another transmission, which may last several milliseconds. Second, the growing density of Wi-Fi networks increases interference between overlapping networks.

WNL has developed and studied various approaches to address this problem in existing and future generations of Wi-Fi (Wi-Fi 6, 7, 8, …), including within the framework of the RSF grant. One of such approaches is the use of OFDMA and hybrid access (scheduled and random) combined with resource reservation for sporadic traffic. Another approach is the use of scheduled access combined with spatial reuse mechanisms that allow devices from different networks to transmit their frames simultaneously if they limit their transmission power and the resulting interference.

Several approaches are based on resource reservation by the device that plans to transmit an urgent frame. There are many types of reservations enabled by different mechanisms proposed in Wi-Fi: single and periodic reservations, reservations in the channel used for data transmission and in another channel, momentary (such as restricted TWT) and long-term reservations. WNL also studies the preemption mechanism, which allows a device to split its low-priority transmissions into several shorter transmissions between which other devices can transmit their urgent frames. Finally, WNL studies methods to prioritize urgent traffic with modifications of the standard random access, for example using the Prioritized EDCA method proposed for Wi-Fi 8.