Modeling and Analysis of Coexistence Between MLO NSTR-based Wi-Fi 7 and Legacy Wi-Fi

Abstract: Wi-Fi 7 introduces Multi-link operation (MLO) to enhance throughput and latency performance compared to legacy Wi-Fi standards. MLO enables simultaneous transmission and reception through multiple links, departing from conventional single-link operations (SLO). To fully exploit MLO's potential, it is essential to investigate Wi-Fi 7's coexistence performance with legacy Wi-Fi devices. Existing approaches, however, have overlooked some crucial aspects of MLO, necessitating the development of a standards-compliant analytical framework to model the actual channel access mechanism of MLO. Therefore, this paper tries to fill the gap by proposing a set of novel Markov chains (MC) to accurately model the MLO operation aligned with multi-link backoff behaviors specified by the standard. Specifically, we design two separate MCs for AP and non-AP multi-link devices (MLD) respectively, based on which transmit and collision probabilities are derived under the saturated traffic condition. Then, we also derive closed-form expressions for the throughput of various device types in the coexistence scenario between Wi-Fi 7 and legacy Wi-Fi, including AP MLD, non- AP MLD, and legacy devices. To validate the accuracy of our proposed models, we developed an ns-3 based simulator by implementing both STR(simultaneous transmission and reception) and NSTR(non-STR) based MLO operations. Our ns-3 based extensive simulations have demonstrated that the proposed analytic model provides accurate estimates on the per device throughput performance, while also revealing the dynamics of inter-WLAN coexistence scenarios.