Hyung-Taek Lim

Challenges in a future IP/ethernet-based in-car network for real-time applications

In current vehicles, a large number of control units are connected by several automotive specific communication buses, facilitating innovative distributed applications. At the same time, computers and entertainment devices use IP and commodity communications technology like Ethernet to connect to the Internet, allowing for innovative solutions and maintaining fast innovation cycles. Today, one can see first applications of Ethernet for in-vehicle communication in contemporary cars. In next generation vehicles, many innovative applications could benefit from the increased bandwidth Ethernet can offer. Therefore, a examination of Ethernet usage for additional in-vehicle communication use cases is needed. In this paper, we show simulation results of promising use cases for in-car Ethernet, while looking at different realistic topologies, types of traffic, and configurations.

Tomorrow's In-Car Interconnect? A Competitive Evaluation of IEEE 802.1 AVB and Time-Triggered Ethernet (AS6802)

Ethernet-based in-car communication is currently a hot topic in the automotive industry. Soon Ethernet will start to oust MOST bus in its domain of info- and entertainment applications. However, the full benefit of a technologically integrated in-car network will only become rewarding with the deployment of an Ethernet-based backbone that integrates all automotive domains on a single layer at increased bandwidth, reduced complexity and cost, while opening car intelligence for future innovations. Such backbone must transport critical control data in real-time. Standard Ethernet requires extensions to comply with the strict timing requirements of driver assistance and safety applications while simultaneously supporting broadband multimedia traffic. In this paper, we compare IEEE 802.1 AVB and Time-triggered Ethernet, two competing real-time approaches. While the first fosters over- provisioning and prioritisation, the second is based on a coordinated time-division-multiple-access (TDMA) policy for media access. By simulating a realistic in-car backbone design and traffic model, we reveal the strengths and weaknesses of both protocols and point to the diverging characteristics of event- and time-triggered policies. Our results show that in this in-car network scenario both protocols are able to meet the rigid timing requirements, while each has its unique benefits and disadvantages.

performance study of an in-car switched ethernet network without prioritization

This paper presents the current state of our research in realtime communication of an IP-based in-car network. The Internet Protocol (IP) will serve as convergence layer of different specific in-car network protocols and IEEE 802.3 Ethernet will be the basic technology to transport IP. In this work, we evaluate a legacy switched Ethernet network without any Quality of Service (QoS) mechanisms. While there are arguments for not using QoS mechanisms, we give evidence that communication requirements and service constraints of a more and more streaming intensive in-car network cannot be met without. We argue for a setup with different traffic types: CAN and FlexRay like control messages, camera streaming, video and audio streaming, and bulk traffic. We will also argue for a simple double star topology as a valid assumption where the target architecture of the IP-based in-car network is not yet clear. Setup and simulation will serve as framework and motivation for future work: Analyzing IP-based real-time communication using QoS mechanisms - characterizing traffic classes after IEEE 802.1Q and IEEE 802.1 Audio Video Bridging (AVB).

IEEE 802.1AS time synchronization in a switched Ethernet based in-car network

As of today Ethernet is used in the in-vehicle network mainly for two use cases: connectivity between the head unit and the rear seat entertainment (RSE) as well as faster onboard diagnostics (OBD). With the increasing bandwidth demand in driver assistance and the wish to easier interconnect the driver assistance and infotainment domains additional usage of Ethernet in the vehicle is being examined. The legacy Ethernet does only provide very limited Quality-of-Service (QoS) mechanisms so that demanding real-time in-vehicle applications cannot meet their constraints. The Audio/Video Bridging (AVB) group introduced several IEEE standards to allow audio and video applications with high QoS demands in a switched Ethernet network. Although these mechanisms were not designed for automotive use cases, they are good extensions to switched Ethernet when QoS demands exist. Therefore, an evaluation of AVB for the usage in in-vehicle networks is needed. In this work, we focus on a base mechanism of the IEEE 802.1 AVB standard, the IEEE 802.1AS time synchronization protocol and its usage in the in-vehicle network. The evaluation is performed by simulation with the network simulation tool OMNeT++ and we modifed the INET-framework with the IEEE 802.1AS capability for our purpose.

Performance evaluation of the inter-domain communication in a switched Ethernet based in-car network

Todays premium vehicles are some of the most complex consumer goods-featuring a large number of different functionalities. These functionalities are being implemented by numerous Electronic Control Units (ECUs), which are often interconnected with CAN, FlexRay, LIN, and MOST. However, some car models already use Ethernet for high bandwidth applications, like diagnosis, flash update, and multimedia applications. With the increasing number of Advanced Driver Assistance Systems (ADAS) the network architecture of the vehicle needs to change in order to keep up with the growing demands. In this paper we focus on a domain-based evolution of todays in-vehicle network using switched Ethernet to keep up with ADAS demands. We examine different suitable Ethernet-based topologies and evaluate them based on realistic in-vehicle traffic in different network load situations. In addition, we determine the impact of MAC-Layer prioritization to the provided in-car applications and to the communication between the in-car domains.

Analysis of Medium Access Protocols for Power Line Communication Realizing In-Car Networks

The number of electronic control units in todays vehicles is permanently increasing. The complexity of the in-car communication also increases because of the growing demand for information exchange. In the past decades rising demands have been countered with adding bus-segments. In order to reduce the complexity and the costs for the future in-car communication infrastructure, power line communication (PLC) provides an alternative. In this paper, we focus on PLC which can reduce the cabling to a minimum. After summarizing the requirements for future in-car systems, the HomePlug Green PHY standard, originally designed for Smart Grid applications, is analyzed according to its applicability to the in-car communication. Due to the availability of standard components, also cost reasons motivate the use of the HomePlug Green PHY standard. To cope with the small message size of in-car communication, we propose a concept for data transfer inside the Frame Control to reduce protocol overhead. In addition to CSMA/CA based medium access, we evaluate and compare two further collision-free variants requiring only slight protocol modifications. As one evaluation result, a priority-based access scheme shows the most promising results.

Empirical Evaluation of Overlap Requirements of Adjacent Radio Cells for Zero Delay Handover

Velocity has a non-neglectable influence on the handover delay experienced by a user if the handover is triggered on a radio-signal-measurement (RSM) based handover scheme. Previous publications have theoretically derived the minimal required overlap of adjacent radio cells for a zero delay handover if signal averaging (low-pass filtering) and a hysteresis margin are employed in the handover decision process. This paper presents for the first time a practical verification of those results by employing real world channel traces from a high-speed train scenario and considering the effects of an existing radio front-end due to the latters receiver sensitivity. Also, in addition to related work, we adapt a time-discrete analytical model for comparing theoretical findings with channel trace based results which is closer to an implementation sampling the radio channels quality at distinct time intervals.

Beware of the hidden! How cross-traffic affects quality assurances of competing real-time Ethernet standards for in-car communication

Real-time Ethernet is expected to become the core technology of future in-car communication networks. Following its current adoption in subsystems for info- and entertainment, broadband Ethernet promises new features in the core of upcoming car series. Its full potential will enfold when deploying Ethernet-based backbones that consolidate all automotive domains on a single physical layer at increased bandwidth but reduced complexity and cost. In such a backbone, traffic with a variety of real-time requirements and best-effort characteristics will share the same physical infrastructure. However, certain applications like online diagnosis, data- or firmware updates, and access to off-board backends will introduce bursty high traffic loads to the sensitive core of the cars communication network. In this work, we analyze the robustness against cross-traffic of real-time Ethernet protocols. Based on a realistic in-car scenario, we demonstrate that background cross-traffic can have significant impact on in-car backbone networks-even for real-time protocols with strict prioritization. By comparing the real-time approaches Ethernet AVBs asynchronous credit based shaping with the time-triggered and rate-constrained traffic classes of Time-triggered Ethernet (AS6802) we quantify how different media access policies suffer from low priority bursts of applications such as diagnosis, online updates or backend-based services. Our simulation study of a realistic in-car backbone design and traffic model reveals that in a realistic in-car network design, cross-traffic may increase end-to-end latency by more than 500% while the jitter can become 14 times higher than for a network without background tasks. We discuss ways to mitigate these degrading effects.

Priority-based energy-efficient MAC protocols for the in-car power line communication

An increasing number of electronic control units in todays vehicles leads to rising communication demands. So far, growing demands were countered with adding additional communication buses at the cost of vastly increasing complexity. One possibility to reduce complexity and costs for the future in-car communication infrastructure is the usage of Power Line Communication (PLC). PLC reduces the cabling to the minimum - the power lines. In this paper, after summarizing main requirements for future in-car communication systems, a recently proposed medium access protocol based on the HomePlug and IEEE 1901 standard is discussed. The protocol is based on unique message priorities and shows good performance regarding throughput and flexibility. In order to decrease the energy consumption, in this paper further new protocol variants are evaluated and compared with the pure priority-based medium access protocol. For the comparison, effects on throughput, delay and loss in flexibility are taken into account. As a result, a combination of rotating prefix and additional pending frame indication slot is found most promising.