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Cyber-physical systems consist of several wirelessly connected components such as sensors that monitor physical phenomena, computational entities that make decisions based on sensed information and actuators that interact with physical processes. Connecting cyber-physical systems to the Internet using IP protocols increases interoperability by avoiding the need for protocol translation gateways. Unfortunately, in this context TCP has been disregarded since it is known to perform poorly in wireless scenarios as it treats packet loss as an indicator for network congestion rather than poor link quality. In this paper, we use the Low-power Wireless Bus (LWB) as a link layer for TCP/IP, taking advantage of its reliability and its routing-free communication. We design a system that integrates LWB with a low-power IP stack and includes TCP-aware schedulers for LWB. We evaluate our system with experiments on real hardware using uIP, a popular embedded Internet protocol stack. Our results demonstrate high TCP throughput in mobile and static scenarios and, furthermore, show that mobility does not decrease TCP performance.

Glossy is a flooding-based communication primitive for low-power wireless networks that leverages constructive interference to achieve high reliability. The Low-power Wireless Bus (LWB) uses Glossy to abstract an entire wireless network into a shared bus like topology. As Glossy is not designed as a secure communication protocol, Glossy and hence LWB are vulnerable to unauthorised eavesdropping and packet injection attacks. In this paper, we propose several security mechanisms to protect Glossy and LWB communication and evaluate their effectiveness in real-world settings. The evaluation of the proposed security mechanisms shows that we can confine the effect of the packet injection attacks on Glossy networks into single hop nodes from the attacker.

High-speed visible light communication (VLC) is a complementary technology to conventional radio frequency communication in wireless networks. One of the essential traits of VLC systems is the ability to provide wireless communication and illumination seamlessly. High-speed VLC systems use high-power LEDs as transmitters in their access points (APs). In real-world deployments, overlapping light beams from multiple APs are necessary to avoid unlit areas. However, overlapping light beams could cause interference in each other's communication at the receiver; hence APs must synchronise their communication. This paper presents Harmony, a time synchronisation system for VLC APs to synchronise their transmissions. Internally, Harmony uses synchronous transmissions in the infrared frequency spectrum to reach nodes over multiple hops. The evaluation of a prototype implementation of Harmony on a small-scale testbed shows that it can synchronise nodes up to nine hops with a maximum error of a few 100s of nanoseconds. While the enduring work on high-speed VLC systems primarily focuses on improving the performance of individual APs, Harmony provides an infrastructure for enhancing system-wide performance.