Enhancing Reliability in RT-WiFi Network

With the rising industrial interest in cyber-physical systems (CPSs), there has been growing concern in the application of real-time wireless technologies to CPS applications. We proposed in previous work the RT-WiFi protocol that provides realtime high-speed predictable data delivery and enables designs to meet time-critical industrial needs. However, without explicit reliability enforcement mechanisms, our previous RT-WiFi design is either subject to uncontrolled packet loss due to noise and other interferences, or may suffer from inefficient communication channel usage. In this paper, we explicitly consider interference from both Wi-Fi and non-Wi-Fi based interference sources, and propose two sets of effective solutions for RT-WiFi network management design. To improve reliability against general non-Wi-Fi based interference, we apply rate adaptation and retransmission techniques, and present an optimal real-time rate adaption algorithm together with a communication link scheduler that has low network management overhead. A novel technique called “overbooking” is introduced to further improve the schedulability of the communication link schedulers while maintaining the required communication reliability. For Wi-Fi based interference, we present mechanisms that utilize virtual carrier sensing to provide reliable data transmission while coexisting with regular Wi-Fi networks. We have implemented the proposed algorithms in the RT-WiFi network management framework, and we demonstrate our system performance with a series of experiments.