Relational network verification is a new approach for validating network changes. In contrast to traditional network verification, which analyzes specifications for a single network snapshot, it analyzes specifications that capture similarities and differences between two network snapshots (e.g., pre- and post-change snapshots). Relational specifications are compact and precise because they focus on the flows and paths that change between snapshots and then simply mandate that all other network behaviors "stay the same", without enumerating them. To achieve similar guarantees, single-snapshot specifications would need to enumerate all flow and path behaviors that are not expected to change in order to enable checking that nothing has accidentally changed. Such specifications are proportional to network size, which makes them impractical to generate for many real-world networks.

Testing and verification have emerged as key tools in the battle to improve the reliability of networks and the services they provide. However, the success of even the best technology of this sort is limited by how effectively it is applied, and in today's enormously complex industrial networks, it is surprisingly easy to overlook particular interfaces, routes, or flows when creating a test suite. Moreover, network engineers, unlike their software counterparts, have no help to battle this problem—there are no metrics or systems to compute the quality of their test suites or the extent to which their networks have been verified.

We introduce PassiveVLN, a flexible, modular and software-defined platform for visible light backscatter networks. PassiveVLN incorporates a modular hardware design and a full-stack software implementation, enabling convenient and scalable deployment as well as rapid prototyping for testing new protocols and applications.

Vehicle-to-anything (V2X) communications technology is an essential substrate to realize future road intelligence and autonomous driving, especially in the areas where there are no existing (radio) network infrastructure. The emerging visible light backscatter communication technique shows great potentials in enabling the massive on-road retroreflective objects to delivery dynamic information to host vehicles. In this work, we design a polarization-based differential reception scheme to suppress ambient noise and realize long range retroreflective V2X communications.

With the rapid growth of vehicle ownership, parking has become an issue, especially in metropolitan areas -- the extra time for check-ins, check-outs and finding available parking spaces not only causes frustration and potential road rage on the driver side, but also increases the traffic congestion, gasoline waste and air pollution in consequence. In order to address these problems, the concept of "smart parking" is put forward. To make a parking lot "smart", we argue that three basic features, namely Vehicle Identification, Parking Space Detection and Indoor Localization are are critical and should be supported by the infrastructure. Herein, we present LightPark, a Visible Light Communication (VLC) solution to realize the vision of "smart parking". Building on top of the visible light backscatter communication primitive, LightPark is able to leverage the lighting infrastructure to perform scalable visible light communication and networking with the batter-free tag devices instrumented on the vehicles and parking spaces to manage the critical information such as identification and real-time location of vehicles, and status of parking spaces in a centralized and low-cost manner.

This paper investigates the feasibility of practical backscatter communication using visible light for battery-free IoT applications. Based on the idea of modulating the light retroreflection with a commercial LCD shutter, we effectively synthesize these off-the-shelf optical components into a sub- mW low power visible light passive transmitter along with a retroreflecting uplink design dedicated for power constrained mobile/IoT devices. On top of that, we design, implement and evaluate PassiveVLC, a novel visible light backscatter communication system. PassiveVLC system enables a battery-free tag device to perform passive communication with the illuminating LEDs over the same light carrier and thus offers several favorable features including battery-free, sniff-proof, and biologically friendly for human-centric use cases. Experimental results from our prototyped system show that PassiveVLC is flexible with tag orientation, robust to ambient lighting conditions, and can achieve up to 1 kbps uplink speed. Link budget analysis and two proof-of-concept applications are developed to demonstrate PassiveVLC's efficacy and practicality.