Automakers keep introducing new functions to vehicles to entice customers, thus increasing the size/number of in-vehicle buses. As a result, adopting multi-buses with a central gateway is becoming a norm in current and future vehicles. Since adding buses increases production cost, knowing whether or not to add a bus at design time to meet the given requirements is essential to design a cost-optimized in-vehicle network. However, due to the lack of an optimal priority-assignment algorithm for multi-bus systems, it is difficult to determine whether additional buses are needed. To address this difficulty, we propose an optimal priority-assignment algorithm, called OPMB, for multiple CAN/CAN-FD buses with a central gateway. OPMB builds on backtracking, and is thus of exponential time complexity. To reduce the execution time effectively for industry-size problems, we identify several theory-proven search-space reduction conditions. Our in-depth simulation has demonstrated that OPMB outperforms the state-of-art priority-assignment algorithms for multi-bus systems, and is suitable for high-speed systems which represent future automotive systems. Also, OPMB is shown to be feasible for most realistic automotive message sets.

Cellular vehicle-to-everything (C-V2X) features have been standardized in 3GPP Release 14. In particular, the standard introduces a fully-distributed resource-allocation algorithm for Mode 4 configuration, called sensing-based semi-persistent scheduling (SB-SPS). Although SB-SPS is effective for orthogonal radio resource allocation, it could easily suffer consecutive message losses caused by interference or half-duplex transmission since SB-SPS uses a selected resource consecutively (multiple times) for periodic transmissions. To mitigate this problem, we propose a novel Mode 4 resource-allocation algorithm, called SNB (Shake-and-Back). Instead of using a selected resource consecutively, SNB either randomly selects and uses a resource each time or uses a selected resource based on its decoding state to avoid consecutive message losses. We have conducted extensive simulations using NS-3 to evaluate SNB considering its coexistence with SB-SPS. Our evaluation results show that SNB improves the average message reception ratio (MRR) at three or more consecutive message losses significantly.

Switched Ethernet has been, and will also be increasingly common in current and future real-time and embedded systems. The IEEE 802.1 working group has recently developed standards and technologies, commonly referred to as Time-Sensitive Networking (TSN), to enhance switched Ethernet with timeliness and dependability. We address, for the first time, the synthesis problem for the TSN frame preemption standards IEEE 802.3br-2016 and 802.1Qbu-2016 by introducing two new configuration parameters: flow to queue and queue to Express/Preemptable MAC interface assignments. We present an optimization framework to determine these configuration parameters with reliability as the optimization goal. Our proposed framework is shown to outperform commonly used priority-assignment as well as intuitive approaches.

Controller Area Network with Flexible Data-rate (CAN-FD) has been drawing considerable attention as the most promising substitute of Controller Area Network (CAN), thanks to its higher bandwidth, larger payload size, and physical-layer compatibility with CAN. In particular, the physical-layer compatibility allows legacy CAN-based Electronic Control Units (ECUs) to share the same communication bus with CAN-FD-based ECUs. However, CAN-based ECUs always treat a CAN-FD frame as an erroneous frame due to the difference in frame format. This, in turn, makes CAN-FD-based ECUs unable to communicate with each other via CAN-FD frames. A straightforward solution to this problem is to utilize the silent mode of the current CAN controller, in which a CAN node does not transmit any frame including error frames, but can receive CAN frames. However, a non-negligible time overhead is incurred by each mode transition, thus degrading the schedulability of mixed CAN and CAN-FD frame sets significantly. We propose a new algorithm, called Priority Assignment with Mode Transition (PAMT), that minimizes the required number of mode transitions by clustering frame instances based on their frame type. Our evaluation results show that PAMT can schedule about 17% more mixed CAN and CAN-FD frame sets than existing optimal priority assignment algorithms for CAN.

Worst-case-based timing verification for the controller area network (CAN) has been the bottleneck to efficient use of its bandwidth. Especially, this inefficiency comes from the worst-case transmission error rate (WCTER) when transmission errors are accounted for. To alleviate this inefficiency, we propose a runtime adaptation scheme, error-adaptive CAN (EACAN). EACAN observes the behavior of transmission errors at runtime, and reconfigures the message period based on the observation to meet the timing-failure requirement. We experimentally evaluate the bandwidth utilization of both EACAN- and WCTER-based verification, showing that the former improves the bandwidth utilization by 14% over the latter.

Real-time embedded systems are becoming more complex to include multiple functionalities. Sharing a computing platform is a natural and effective solution to reducing the cost of those systems. However, the sharing can cause serious problems in mixed-criticality systems where applications have different levels of criticality. Certifying the mixed-criticality systems requires efficient scheduling algorithms and schedulability tests different from the ones used in single criticality systems.