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.

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 present TeaCP, a prototype toolkit for the evaluation and analysis of collection protocols in both simulation and experimental environments running on TinyOS. Our toolkit consists of a testing system, which runs a collection protocol of choice, and an optional SD card-based logging system, which stores the logs generated by the testing system. The SD card datalogger allows a wireless sensor network (WSN) to be deployed flexibly in various environments, especially where wired transfer of data is difficult. Using the saved logs, TeaCP evaluates a wide range of performance metrics, such as reliability, throughput, and delay. TeaCP further allows visualization of packet routes and the topology evolution of the network, under both static and dynamic conditions, even in the face of transient disconnections. Through simulation of an intra-car WSN and real lab experiments, we demonstrate the functionality of TeaCP for comparing the performance of two prominent collection protocols, the Collection Tree Protocol (CTP) and the Backpressure Collection Protocol (BCP). We also present the usage of TeaCP as a high level diagnosis tool, through which an inconsistency of the BCP implementation for the CC2420 radio chips is identified and resolved.

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.