RT-WiFi: Real-Time High-Speed Communication Protocol for Wireless Cyber-Physical Control Applications

Yi-Hung Wei, Quan Leng, Song Han, Aloysius K. Mok, Wenlong Zhang, Masayoshi Tomizuka
<span title="">2013</span> <i title="IEEE"> <a target="_blank" rel="noopener" href="https://fatcat.wiki/container/v45oxowmzff5lbub4ixtl2tazu" style="color: black;">2013 IEEE 34th Real-Time Systems Symposium</a> </i> &nbsp;
Applying wireless technologies in control systems can significantly enhance the system mobility and reduce the deployment and maintenance cost. Existing wireless technology standards, however either cannot provide real-time guarantee on packet delivery or are not fast enough to support high-speed control systems which typically require 1kHz or higher sampling rate. Nondeterministic packet transmission and insufficiently high sampling rate will severely hurt the control performance. To address
more &raquo; ... is problem, in this paper, we present our design and implementation of a real-time high-speed wireless communication protocol called RT-WiFi. RT-WiFi is a TDMA data link layer protocol based on IEEE 802.11 physical layer to provide deterministic timing guarantee on packet delivery and high sampling rate up to 6kHz. It incorporates configurable components for adjusting design trade-offs including sampling rate, latency variance, reliability, and compatibility to existing Wi-Fi networks, and thus can serve as an ideal communication platform for supporting a wide range of high-speed wireless control systems. We implemented RT-WiFi on commercial off-the-shelf hardware and integrated it into a mobile gait rehabilitation system. Our extensive experiments demonstrate the effectiveness of RT-WiFi in providing deterministic packet delivery in both data link layer and application layer, which further eases the controller design and significantly improve the control performance. Flexible Data Link Layer Configuration: Different control applications have different communication requirements on data delivery, and it is hard to apply a rigid design to a wide range of applications. We envision RT-WiFi as a configurable platform to provide great flexibility to the control designers, who can choose their own design parameters according to the target applications. These design trade-offs include sampling rate, communication reliability, real-time data delivery, and coexistence with existing Wi-Fi networks. Transparent System Design: In order to make RT-WiFi easily available and simple to integrate with existing applications, it should reuse current hardware and make minimum changes on software. Users should be able to use RT-WiFi on commercial off-the-shelf (COTS) IEEE 802.11 network interfaces, and run existing applications on top of RT-WiFi with no or minimum modifications. In addition, the transparent system design allows the users to leverage existing IEEE 802.11 security techniques and build mesh networks easily. Our contributions in this paper are three-fold: • We have designed the RT-WiFi protocol to provide a flexible real-time high-speed wireless communication 2013 IEEE 34th Real-Time Systems Symposium
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