Understanding the New Enhanced Multi-Link Single Radio Feature of IEEE 802.11be WLANs

The IEEE 802.11 working group is currently finalizing the 802.11be amendment, which defines the features that will be supported by Wi-Fi 7 devices. A prominent new feature, termed Multi-Link Operations (MLO), is the ability for a device to operate on multiple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">links</i>, i.e., on multiple frequency channels. Among the various MLO modes defined, Enhanced Multi-Link Single Radio (EMLSR) is attracting the interest of many vendors due to its potential for exploiting operations on multiple links through reduced hardware capabilities. In this paper, we first provide an overview of the standard specifications for EMLSR and describe the model underlying its implementation that we have contributed to the ns-3 simulator. The implemented model is rather flexible and enables to simulate various architectures differing for implementation cost, power consumption and performance. Then, we thoroughly evaluate several EMLSR configurations with the goal of shedding light on the possible alternatives that are available. We consider both a scenario of saturated conditions without interfering traffic and a scenario of non-saturated conditions with interfering traffic. Our study shows that the main differences in performance among the various EMLSR configurations are observed in the uplink direction and that EMLSR operations enable to reduce latency with respect to single-link devices at the cost of a slight increase in power consumption.