Analyses of NSTR Multi-Link Operation in the Presence of Legacy Devices in an IEEE 802.11 be Network

The upcoming IEEE 802.11be standard, aka Wi-Fi 7, introduces native support for the multilink operation. It allows Wi-Fi 7 devices to use several links located at different frequency channels simultaneously. However, in some cases, e.g., when the links operate on the channels close to each other, cross-link interference prevents sensing the channel on one link while transmitting on the other one. Thus, at any moment in time, such a device shall not perform simultaneous transmission and receptions but should only do synchronous transmission or synchronous reception. However, in the presence of legacy devices that support only one link, the channel state on different links is not synchronized, reducing the probability of starting transmission on both links synchronously. Intuitively, to improve performance, the devices shall try to align their transmissions with ongoing ones, which should allow them to start simultaneous transmission on both links next time. With extensive simulation in various scenarios, this paper shows that the performance of multilink devices degrades in the presence of legacy devices and the described intuitive approach only improves the performance of legacy devices rather than multilink devices.