We propose an approach to leverage multi-bounce returns of a flash LiDAR on portable smartphones for 3D specular surface reconstruction. Traditional LiDAR systems assume that all returns are one-bounce returns, which can lead to an overestimation of the true mirror surface and cause it to appear as if there is a hole. However, in reality, returns from mirror surfaces follow multi-bounce paths. We operate with a consumer-grade, coarse multi-beam flash LiDAR, enabling real-time mapping on an affordable and portable smartphone. To address the challenges posed by the coarse setup, where the transmitter and receiver are co-located, we propose solving the association problem using the ‘reciprocal pair’ algorithm. This algorithm can distinguish between different types of bounces from multi-bounce returns. We have demonstrated detection over multiple consecutive frames for dense mirror mapping. In addition to 3D reconstruction, we show that multi-bounce returns enhance performance in applications such as segmentation and novel view synthesis. Our method can be integrated with state-of-the-art learned-based models, enhancing their robustness in discerning ambiguous scenarios. Importantly, our approach can map various specular surfaces like mirrors and glasses without assuming specific shapes, and it can operate on non-perpendicular specular-diffuse surface pairs.

With the emergence of connected and autonomous vehicles, sensors are increasingly deployed within cars to support new functionalities. Traffic generated by these sensors congest traditional intra-car networks, such as CAN buses. Furthermore, the large amount of wires needed to connect sensors makes it harder to design cars in a modular way. To alleviate these limitations, we propose, simulate, and implement a hybrid wired/wireless architecture, in which each node is connected to either a wired interface or a wireless interface or both. Specifically, we propose a new protocol, called Hybrid-Backpressure Collection Protocol (Hybrid-BCP), to efficiently collect data from sensors in intra-car networks. Hybrid-BCP is backward-compatible with the CAN bus technology, and builds on the BCP protocol, designed for wireless sensor networks. We theoretically prove that an idealized version of Hybrid-BCP achieves optimal throughput. Our testbed implementation, based on CAN and ZigBee transceivers, demonstrates the load balancing and routing functionalities of Hybrid-BCP and its resilience to DoS attacks and wireless jamming attacks. We further provide simulation results, obtained with the ns-3 simulator and based on real intra-car RSSI traces, that compare between the performance of Hybrid-BCP and a tree-based data collection protocol. Notably, the simulations show that Hybrid-BCP outperforms the tree-based protocol on throughput by 12 percent. The results also show that Hybrid-BCP maintains high packet delivery rate and low packet delay for safety-critical sensors that are directly connected to the sink through wire.

As over-the-air (OTA) vehicle software and firmware updates become a common and frequent practice, Original Equipment Manufacturers (OEMs) seek ways to reduce costs by utilizing opportunistic free wireless links into the vehicle. Unlike previous works that rely on opportunistic direct wireless links between the vehicle and network infrastructure (or other vehicles), our proposed VehiCache system uses trusted mobile devices, e.g., smart phones, as agents, to bridge between the cloud and the vehicle, and seamlessly convey OTA data into the vehicle, in a secure, and a cost effective manner. VehiCache was simulated and analyzed under both the traditional car-ownership, and the popularity-gaining-car-sharing usage models, showing that VehiCache is capable of distributing non-critical OTA content with high probability within a reasonable amount of time. Finally, preliminary observations from a VehiCache proof-of-concept demonstrator are reported.

The Controller Area Network (CAN) is a shared medium, priority-based communication protocol, widely used in the automotive industry for interconnecting electrical components. Although allowing messages to take priority over others in accessing the shared medium is naturally desirable for vehicular applications, it also provides a vulnerability for Denial-of-Service (DoS) attacks. This paper studies the impact of such priority- based DoS attacks and proposes a mitigating scheme. We find that implementation details have a significant impact on the efficiency of priority- based DoS attacks. Nevertheless, with a proper configuration, a single attacker can block an entire CAN network and deem it unusable. To mitigate this problem, we propose integrating a wireless interface and design a hybrid wired/wireless protocol that schedules packet transmissions on the wired and wireless links. Our testbed results show that the hybrid wired/wireless protocol improves the throughput under a two-node DoS attack by a factor of four. Additional experimental results demonstrate that our hybrid wired/wireless protocol is robust to jamming attacks on the wireless link.

We experimentally investigate the benefits of multi- hop networking for intra-car data aggregation under the current state-of-the-art Collection Tree Protocol (CTP). We show how this protocol actively adjusts collection routes according to channel dynamics in various practical car environments, resulting in performance gains over single-hop aggregation. Throughout our experiments, we target traditional performance metrics such as delivery rate, number of transmissions per packet, and delay, and our results confirm, both qualitatively and quantitatively, that multi-hop communication can provide a reliable and robust approach for data collection within a car.

The identifying code problem for a given graph involves finding a minimum set of vertices whose neighborhoods uniquely overlap at any given graph vertex. Initially introduced in 1998, this problem has demonstrated its fundamental nature through a wide variety of applications, such as fault diagnosis, location detection, and environmental monitoring, in addition to deep connections to information theory, superimposed and covering codes, and tilings. This work establishes efficient reductions between the identifying code problem and the well-known set-covering problem, resulting in a tight hardness of approximation result and novel, provably tight polynomial-time approximations. The main results are also extended to$r$-robustidentifying codes and analogousset$(2r+1)$-multicoverproblems. Finally, empirical support is provided for the effectiveness of the proposed approximations, including good constructions for well-known topologies such as infinite two-dimensional grids.

Wireless Sensor Networks (WSNs) provide an important means of monitoring the physical world, but their limitations present challenges to fundamental network services such as routing. In this work we utilize an abstraction of WSNs based on the theory of identifying codes. This abstraction has been useful in recent literature for a number of important monitoring problems, such as localization and contamination detection. In our case, we use it to provide a joint infrastructure for efficient and robust monitoring and routing in WSNs. Specifically, we provide an efficient and distributed algorithm for generating robust identifying codes with a logarithmic performance guarantee based on a novel reduction to the set k-multicover problem; to the best of our knowledge, this is the first such guarantee for the robust identifying codes problem, which is known to be NP-hard. We also show how this same identifying-code infrastructure provides a natural labeling that can be used for near-optimal routing with very small routing tables. We provide experimental results for various topologies that illustrate the superior performance of our approximation algorithms over previous identifying code heuristics.

We propose a peer-to-peer architecture designed to overcome asymmetries in upload/download speeds that are typical in end-user dialup, broadband and cellular wireless Internet connections. Our approach allows users at remote locations to access information stored on their home computers at rates often exceeding their home connection’s upload capacity. The key to this approach is to share file data when communications are idle using random linear coding, so that, when needed, an end-user can download a file from several sources at a higher data rate than his home computer’s upload capacity. We prove that our proposed system is asymptotically fair, in that (even malicious) users are proportionally assigned idle bandwidth depending on how much bandwidth they contribute, and that there is a natural incentive to join and cooperate fairly in the system. In addition, our approach provides cryptographic security and geographic data robustness to the participating peers.

Identifying codes have been used in a variety of applications, including sensor-based wireless location detection in harsh environments. In such applications, a user determines his location through a unique signature (i.e. a codeword in an identifying code) based on sensor transmissions that he can hear. Adding sensors to such a system can increase its robustness at the expense of added signal interference and, consequently, decreased reliability. In this work we propose and develop an alternate approach to maintaining robustness and reliability through the use of "disjoint identifying codes", which reduces inter-sensor interference by dividing a system into physically separate and independent location determining sub-systems. We provide information-theoretic upper and lower bounds on the number of such sub-systems for a given connectivity graph, and we show that these bounds are asymptotically tight for a modification of Hadamard matrices

Objective testing of centerline extraction accuracy in quantitative coronary angiography (QCA) algorithms is a very difficult task. Standard tools for this task are not yet available. We present a simulation tool that generates synthetic angiographic images of a single coronary artery with predetermined centerline and diameter function. This simulation tool was used creating a library of images for the objective comparison and evaluation of QCA algorithms. This technique also provides the means for understanding the relationship between the algorithms' performance and limitations and the vessel's geometrical parameters. In this paper, two algorithms are evaluated and the results are presented.