Performance analysis and optimization of TCP over multi link operation of WiFi 7

Abstract

IEEE 802.11be introduces MLO (Multi-Link Operation) where MLDs (Multi-Link Devices) can take advantage of the multiple links available in the 2.4, 5 and 6 GHz bands without having to associate on each link separately. TCP traffic involves transmission of TCP Data as well as TCP acknowledgements in the reverse direction, both of which can be transmitted on any of the available links. As a result of this bi-directional traffic and distribution flow across links in MLO, there can be some interesting consequences on TCP performance. This work analyzes the interaction of MLO with TCP using the latest 802.11be models in the open-source network simulator NS-3 (version 3.40). As expected, throughput increases with MLO but latency suffers in many cases, specifically the tail latency. This is in contradiction to one of the key objectives of MLO, which is to improve latency. The root cause behind this behavior is an increase in collisions with the number of links. Thus, the work proposes a TID-to-Link mapping solution to reduce the number of collisions and improve both throughput and latency.