Jayanthi Rao

Prioritized gossip in vehicular networks

We propose using real world mobility traces to identify tractable theoretical models for the study of distributed algorithms in mobile networks. Specifically, we derive a vehicular ad hoc network model from a large corpus of position data generated by San Francisco-area taxicabs. Unlike previous work, our model does not assume global connectivity or eventual stability. Instead, we assume only that some subset of processes might be connected through transient paths (e.g., paths that exist over time). We use this model to study the problem of prioritized gossip, in which processes attempt to disseminate messages of different priority. We present CabChat, a distributed prioritized gossip algorithm that leverages an interesting connection to the classic Tower of Hanoi problem to schedule the broadcast of packets of different priorities. Whereas previous studies of gossip leverage strong connectivity or stabilization assumptions to prove the time complexity of global termination, in our model, with its weak assumptions, we instead analyze CabChat with respect to its ability to deliver a high proportion of high priority messages over the transient paths that happen to exist in a given execution.

Evaluating vehicular ad hoc networks for group applications

This paper identifies a class of potential vehicular network applications that are geographically localized and restricted to groups of vehicles. Applications such as group voice or text chat, periodic location updates and rear-seat gaming require content to be published and consumed by group members. In this framework, content delivery performance is the key metric. In this paper, we study the performance of such applications using the network simulation tool, ns-2 with realistic vehicle mobility traces. In order to mirror real-life vehicle mobility, we use vehicle location traces generated by a micro-traffic simulator that implements sophisticated vehicle mobility models like car-following, lane changing and passing. The goal of the simulations is to understand the impact of using two different MAC technologies, the amount of multi-hop forwarding, the size of the vehicle groups, and network density on the content delivery within the groups. The results are promising and indicate that group applications are feasible and can achieve high content delivery when network parameters are tuned appropriately.

Pulse Switching: Toward a Packet-Less Protocol Paradigm for Event Sensing

This paper presents a novel pulse switching protocol framework for ultra light-weight wireless network applications. The key idea is to abstract a single Ultra Wide Band (UWB) pulse as the information switching granularity. Pulse switching is shown to be sufficient for on-off style event monitoring applications for which a monitored parameter can be modeled using a binary variable. Monitoring such events with conventional packet transport can be prohibitively energy-inefficient due to the communication, processing, and buffering overheads of the large number of bits within a packets data, header, and preambles for synchronization. The paper presents a joint MAC-routing protocol architecture for pulse switching with a novel hop-angular event localization strategy. Through analytical modeling and simulation-based experiments it is shown that pulse switching can be an effective means for event networking, which can potentially replace the traditional packet transport when the information to be transported is binary in nature.

A Multi-Scale Spatiotemporal Perspective of Connected and Automated Vehicles: Applications and Wireless Networking

Wireless communication is a basis of the vision of connected and automated vehicles (CAVs). Given the heterogeneity of both wireless communication technologies and CAV applications, one question that is critical to technology road-mapping and policy making is which communication technology is more suitable for a specific CAV application. Focusing on the technical aspect of this question, we present a multi-scale spatiotemporal perspective of wireless communication technologies as well as canonical CAV applications in active safety, fuel economy and emission control, vehicle automation, and vehicular infotainment. Our analysis shows that CAV applications in the regime of small spatiotemporal scale communication requirements are best supported by V2V communications, applications in the regime of large spatiotemporal scale communication requirements are better supported by cellular communications, and applications in the regime of small spatial scale but medium-to-large temporal scale can be supported by both V2V and cellular communications and provide the opportunity of leveraging heterogeneous communication resources.

Aggregation in Smartphone Sensor Networks

The first wave of sensor network deployments from the early 2000s relied on aggregation-a strategy in which readings are combined locally using low-power radio links before they are communicated to the gateway. Aggregation reduced dependence on battery-draining, long-distance radio links, and reduced redundancy among reported data. We are now experiencing a second wave of sensor network research driven by ubiquitous smartphone usage. In this paper, we study the application of aggregation to the new smartphone sensor network setting, arguing that it can help reduce costs in contexts where existing cost-reduction strategies, such as opportunistic use of Wi-Fi and data piggybacking, do not apply. In more detail, we propose two new aggregation protocols, designed for the challenges of high mobility, that offer trade-offs in terms of bandwidth and energy savings. We then evaluate these protocols using both test bed experimentation (using a collection of 11 Samsung Galaxy Nexus smartphones running a Noise Tube-like application) and trace based simulation (using a large collection of mobility traces from taxi cabs in Singapore). Our experiments demonstrate that our aggregation protocols reduce cellular bandwidth usage by up to 95% while losing less than 5% of the data. Moreover, in many common cases, our protocols also yield significant energy savings.

Exploiting Consistency among Heterogeneous Sensors for Vehicle Anomaly Detection

Modern vehicles house many advanced components; sensors and Electronic Control Units (ECUs) — now numbering in the 100s. These components provide various advanced safety, comfort and infotainment features, but they also introduce additional attack vectors for malicious entities. Attackers can compromise one or more of these sensors and flood the vehicle’s internal network with fake sensor values. Falsified sensor values can confuse the driver, and even cause the vehicle to misbehave. Redundancy can be used to address compromised sensors, but adding redundant sensors will increase the cost per vehicle and is therefore less attractive. To balance the need for security and cost-efficiency, we exploit the natural redundancy found in vehicles. Natural redundancy occurs when the same physical phenomenon causes symptoms in multiple sensors. For instance, pressing the accelerator pedal will cause the engine to pump faster and increase the speed of the vehicle. Engine RPM and vehicle speed are multiple sensors which respond in a related fashion to the same cause of the accelerator pedal. The challenge is identifying the relationship between similar but different sensors under normal operation and detecting anomalous be-havior accurately. In this paper, we develop the tools to capture the relationship between sensors. Specifically, we use the pairwise correlation between key variables, and use cluster-analysis to identify distinct behavior of drivers. Moreover, we show preliminary results of using these tools to detect attacks within a vehicular communication bus.

VLnsight: enabling open innovation in networked vehicle sensing and control

Transforming traditional single-vehicle-based safety and efficiency control, networked VSC is expected to be a basic element of addressing the challenges for safety and sustainability of road transportation. However, vehicles remain largely as black boxes to researchers and application developers, and open source platforms for evaluating networked VSC solutions at high-fidelity and scale are still lacking. To exploit the potential of networked VSC, we develop the research infrastructure VInsight, which provides basic building blocks for gaining insight into vehicle internals and for enabling high-fidelity, at-scale evaluation of networked VSC solutions. More specifically, VInsight integrates the OpenXC vehicular sensing platform into the Global Environment for Network Innovations (GENI). VInsight deploys a WiMAX research network for integrating high-fidelity real-world vehicular sensing with at-scale ns-3 emulation in the GENI cloud computing facilities, and VInsight develops WiMAX measurement tools for understanding WiMAX link characteristics and driving high-fidelity emulation of networked VSC systems.1 The WiMAX network of VInsight also enables immediate applications such as campus safety patrol; this synergy with opt-in users enables the permanent deployment of VInsight for open innovation in networked VSC systems, thus helping develop solutions to address the grand challenges of road transportation today.

Reprint of Prioritized gossip in vehicular networks

We propose using real world mobility traces to identify tractable theoretical models for the study of distributed algorithms in mobile networks. Specifically, we derive a vehicular ad hoc network model from a large corpus of position data generated by San Francisco-area taxicabs. Unlike previous work, our model does not assume global connectivity or eventual stability. Instead, we assume only that some subset of processes might be connected through transient paths (e.g., paths that exist over time). We use this model to study the problem of prioritized gossip, in which processes attempt to disseminate messages of different priority. We present CabChat, a distributed prioritized gossip algorithm that leverages an interesting connection to the classic Tower of Hanoi problem to schedule the broadcast of packets of different priorities. Whereas previous studies of gossip leverage strong connectivity or stabilization assumptions to prove the time complexity of global termination, in our model, with its weak assumptions, we instead analyze CabChat with respect to its ability to deliver a high proportion of high priority messages over the transient paths that happen to exist in a given execution.