Various defense schemes --- which determine the presence of an attack on the in-vehicle network --- have recently been proposed. However, they fail to identify which Electronic Control Unit (ECU) actually mounted the attack. Clearly, pinpointing the attacker ECU is essential for fast/efficient forensic, isolation, security patch, etc. To meet this need, we propose a novel scheme, called Viden (Voltage-based attacker identification), which can identify the attacker ECU by measuring and utilizing voltages on the in-vehicle network. The first phase of Viden, called ACK learning, determines whether or not the measured voltage signals really originate from the genuine message transmitter. Viden then exploits the voltage measurements to construct and update the transmitter ECUs' voltage profiles as their fingerprints. It finally uses the voltage profiles to identify the attacker ECU. Since Viden adapts its profiles to changes inside/outside of the vehicle, it can pinpoint the attacker ECU under various conditions. Moreover, its efficiency and design-compliance with modern in-vehicle network implementations make Viden practical and easily deployable. Our extensive experimental evaluations on both a CAN bus prototype and two real vehicles have shown that Viden can accurately fingerprint ECUs based solely on voltage measurements and thus identify the attacker ECU with a low false identification rate of 0.2%.

Contemporary vehicles are getting equipped with an increasing number of Electronic Control Units (ECUs) and wireless connectivities. Although these have enhanced vehicle safety and efficiency, they are accompanied with new vulnerabilities. In this paper, we unveil a new important vulnerability applicable to several in-vehicle networks including Control Area Network (CAN), the de facto standard in-vehicle network protocol. Specifically, we propose a new type of Denial-of-Service (DoS), called the bus-off attack, which exploits the error-handling scheme of in-vehicle networks to disconnect or shut down good/uncompromised ECUs. This is an important attack that must be thwarted, since the attack, once an ECU is compromised, is easy to be mounted on safety-critical ECUs while its prevention is very difficult. In addition to the discovery of this new vulnerability, we analyze its feasibility using actual in-vehicle network traffic, and demonstrate the attack on a CAN bus prototype as well as on two real vehicles. Based on our analysis and experimental results, we also propose and evaluate a mechanism to detect and prevent the bus-off attack.

Detecting how a vehicle is steered and then alarming drivers in real time is of utmost importance to the vehicle and the driver's safety, since fatal accidents are often caused by dan- gerous steering. Existing solutions for detecting dangerous maneuvers are implemented either in only high-end vehicles or on smartphones as mobile applications. However, most of them rely on the use of cameras, the performance of which is seriously constrained by their high visibility requirement. Moreover, such an over/sole-reliance on the use of cameras can be a distraction to the driver.

While femtocells provide various advantages for associated users, the occurred interference on the macrocell layer remains a severe problem. To resolve such problems, various methods of femtocell operation has been discussed. One way is to operate a femtocell with a hybrid access mode, which allows not only member users but also non-member users to connect to the femtocell. To differentiate the service level and access priority, hybrid mode femtocells exploits a resource partitioning threshold to provide priority resource regions for different types of users. In this paper, we propose a scheme that sets the appropriate partitioning threshold to enhance the downlink performance of the overall network. The threshold value is numerically derived taking into account of the SINR value. Furthermore, we address the procedures of how the required information are acquired for computing and setting the appropriate threshold. Through simulations, we show that our proposed scheme provides high user throughput and low interference to the underlying macrocell layer.

Due to the limited battery in wireless sensor networks (WSNs), energy efficiency is an important factor when designing a MAC protocol. To minimize energy consumption, most of MAC protocols in WSNs exploit low duty cycling. Among those, RMAC allows a node to transmit a data packet for multiple hops in a single duty cycle, which is made possible by exploiting a control frame named Pioneer (PION) for the path set up. In this paper, we present a MAC protocol called hop extended MAC (HE-MAC) that enables a node to transmit a data packet for more hops in a single duty cycle compared to RMAC. It employs an EXP (Explorer) frame to set up the path for multiple hop transmission, which contains the information about the maximum hop that a packet can travel through in a single duty cycle. Using the information in EXP and an internal state of ready-to-receive (RTR), HE-MAC extends the relay of a packet beyond the termination of the data period by two more hops compared to RMAC. Also along with our proposed adaptive sleeping method, it also reduces power consumption. We analytically obtain the packet latency in HE-MAC and evaluate the performance through ns-2 simulations. Compared to RMAC, HE-MAC shows 42.2% less power consumption and 23.6% less packet delay on average for a random topology of 300 nodes.

In this paper, we propose a new centralized routing protocol named WRP that aims at maximizing the network lifetime. In WRP, the sink node is assumed to be with more capabilities and basically collects each node's estimated wakeup time. This enables the sink node to estimate the wakeup times of all sensor nodes even if some of them are multi-hops away from the sink node. The estimated information is used to find a new route without flooding when some links are broken. Owing to these features, WRP solves the problem of high energy consumption mainly caused by the clock drift in ultra low duty cycled environments. It achieves longer network lifetime independently of the node density because the amount of control traffic does not increase with the node density. We investigate the performance of WRP through extensive simulations and show that WRP increases the network lifetime by more than 10 times against existing routing protocols. WRP can be a very promising routing protocol applicable to the monitoring case like AMR (Automatic Metering Reading) and AMI (Advanced Metering Infrastructure).

The duty cycle of a wireless sensor node is a key factor that determines the life time of a wireless sensor network. In general, sensor medium access control protocols reduce the duty cycle to achieve longer lifetime. However, we found out that their performance improvements substantially decrease under extremely low duty cycles (0.1%). It is with estimation of the relative clock speed between the sender and the receiver, and uses it to minimize energy consumption. It saves energy significantly well compared to the existing schemes in an order of ten times, and the performance gap increases with lowering the duty cycle.