WiROS: A QoS Software Solution for ROS2 in a WiFi Network

Abstract

Robot Operating System (ROS) has played a pivotal role as a communication middleware among different peripherals, including sensors and actuators of robotics and other systems, with the advancement of connected systems around the globe. The development of DDS (Data Distribution Service) based ROS2 has also increased its popularity for applications involving multi-bot communication over the network. The performance of ROS2 communication among the locally connected ROS2-based application endpoints depends mainly upon the system’s computational capabilities. However, when these endpoints are connected over wireless networks, various network-level parameters must be considered. Although there are existing QoS (Quality of Service) options, such as reliability, durability, etc., in the ROS2 framework, they are primarily application-level QoS implemented to verify the authentication and validation of the ROS2 topic stream’s messages. But QoS configurations in ROS2 do not ensure network layer QoS, e.g., IP (Internet Protocol) and MAC (Media Access Control) layer QoS. In a band-limited network, ensuring the network layer QoS becomes essential for the flow of latency-critical messages. In this thesis, we address this shortcoming in the current ROS2 software. First, to present the main problem, we set up ROS2 with the Gazebo simulator. We send latency-sensitive, mission-critical sensory data through a ROS 2 node in the presence of high throughput background image traffic. We observe that this results in traffic confluence at the ROS2 publisher node’s host system’s Network Interface Card (NIC), with large packets enqueued at the NIC buffer ahead of the mission-critical packet even when we change QoS settings of ROS2 appropriately. In particular, we observe that a control task in the Gazebo framework fails in this setting. Our main contribution in this thesis is an add-on to ROS2 communication to mitigate the data traffic confluence problem and allow the integration of network-level QoS guarantees with ROS2. Our solution uses iproute2’s tc (traffic control) tool, an open-source collection of user-space tools for controlling and monitoring various aspects of networking in the Linux kernel. Specifically, we take the priorities and traffic requirements of each topic and implement the necessary prioritization of packets using HTB (Hierarchical Token Bucket) filters of tc. We provide QoS assurance for ROS2-based communication in the form of a software solution called “ROSQOS-PANEL”, which allows the option to set up different schedulers that need to be implemented for the queues associated with traffic flows of various topics. This software can also monitor the queues and ROS2-associated topics statistics in real time, which can be fed back to applications to make them network-aware, and may be of independent interest. We demonstrate the working of ROS-QOS-PANEL software and showcase how it helps achieve the required QoS in a remote driving operation over a Wi-Fi networkbased testbed. The testbed has been prepared using a simulated robotic and a real network environment. We plan on making an open-source contribution to the ROS2 stack based on this software. We conclude with the future scope of this project and discuss the scope for improvement and enhancement for “ROS-QOS-PANEL”.