ETHERNET AS AN EMERGING TREND IN VEHICLE NETWORK TECHNOLOGY PART II

Transcription

1 ETHERNET AS AN EMERGING TREND IN VEHICLE NETWORK TECHNOLOGY PART II In the second part of this paper on Ethernet as an emerging trend in vehicle network technology, we look at the challenges and the progress made in automotive Ethernet technology. It must be noted that there is significant difference in the desired behaviour of the controlled object of automotive and industrial networks, and it needs fine tuning to meet the real time requirement of various critical automotive applications. 18

2 authors MUKTI PRASAD is Scientist 'C' at TIFAC, Department of Science & Technology, Government of India. RAKESH KUMAR DEY is Project Associate at TIFAC, Department of Science & Technology, Government of India. ARGHYA SARDAR is Scientist E & Head, Transportation Division at TIFAC, Department of Science & Technology, Government of India. Inter sub-system communication for invehicle networks will require safe, efficient and structured communication, which can be possible through a backbone network. Ethernet can change invehicle networks from decentralised domain-specific architectures to hierarchical network architectures, which connects application domains and sub-networks that require higher bandwidth. A comparison between the present and future domain architectures is illustrated in 1 [11]. Ethernet allows for reuse and exchangeability on the different protocol levels. The topology need not be predefined by the technology but can be chosen to suit the specific situation whether the application is diagnostics, driver assistance, infotainment, or something else. Since Ethernet is IP-based protocol, many existing car applications that use TCP/IP can easily be ported on Ethernet. Diagnostics, in-car internet access, smart charging for electric vehicles are some of the applications supported by Internet protocol. As a common networking technology for control units in the car, IP enables reduction of the complexity of the electronic architecture as mentioned above. Some of the other important technologies of Ethernet protocol, which supports automotive Ethernet include IEEE Audio Video Bridging (AVB) standard, Time Triggered Ethernet (TT Ethernet) and Event Triggered Ethernet. IEEE Audio Video Bridging (AVB): IEEE AVB is a potential in-vehicle network technology for multimedia infotainment and driver assistance. It enhances quality of service and provides the specifications for time synchronised low-latency streaming services through IEEE 802 networks. It includes three specifications: :: IEEE 802.1AS Timing and Synchronisation for Time-Sensitive applications, has accuracy better than 1µs; :: IEEE 802.1Qat Stream Reservation Protocol that specifies reservation of resources within switches; :: IEEE 802.1Qav Forwarding and Queuing Enhancements for Time- Sensitive Streams. These specifications extend the IEEE 802.1Q standard splitting traffic into two classes, i.e., the time-sensitive AVB traffic and autotechreview January 2015 Volume 4 Issue 1 19

3 for real-time applications, such as IEEE AVB standard and TT Ethernet, are not suitable for delivery guarantee within 100 μs. Whereas Ethernet brings with it promise for very high bandwidth, gigabit Ethernet requires very expensive shielding. Another point for consideration is that most of the current ECUs used are not able to handle high data rate. PROGRESS IN AUTOMOTIVE ETHERNET TECHNOLOGY 1 Domain architecture of today and in future the non-avb best-effort traffic. TT Ethernet: This enables deterministic time-triggered communications, rate constrained and event- triggered communications over the same network. It supports three different traffic types: time-triggered (TT), rate-constrained (RC) and best-effort (BE). Time-triggered (TT) messages are transmitted at predefined points in time and have precedence over the other traffic classes. They are suitable for safety critical and highly time sensitive applications such as X-by-wire. While RC messages are suitable for multimedia or safety critical automotive aerospace applications that need highly reliable communications, BE messages use remaining bandwidth and have less priority than TT and RC messages. Here, the lower priority messages are interrupted and stored in the switch buffer to allow time-triggered messages to take priority. CHALLENGES However, application of Ethernet in automotive network applications requires some special considerations. There is significant difference in the desired behaviour of the controlled object of automotive and industrial networks, and needs fine tuning to meet the real time requirement of various critical automotive applications, with respect to flexibility, scalability, complexity, huge traffic, bandwidth and quality of service (QoS). Specific requirements for automotive use include meeting stringent robustness demands like operation of networks under high temperature and high electromagnetic radiation across network protocol, bandwidth, latency, synchronisation, and network management requirements. In spite of its existence for over 20 years, several limitations of the Ethernet technology have posed challenges in automobiles. Ethernet did not meet the OEM Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) requirements for the automotive market. EMI requirement demanded by the car manufacturer, when the car is running, is very stringent. Ethernet is not designed to withstand such stringent demand of EMI for cars. 100 mbps (and above) Ethernet have too much RF noise, and Ethernet is also susceptible to alien noise from other devices in a car. Even the Ethernet protocols modified Application Higher Layer Protocols Data Link Layer Physical Layer 1st Generation Independent Subsystems and Diagnostics, ECU Flashing, Rear-view Cameras Diagnostics over IP (ISO 13400) 100 Base Tx Fast Ethernet (IEEE 802.3u) It has been suggested that application of Ethernet in automobiles will go through a gradual evolution, as depicted in 2 [11]. Generation 1: Diagnostics Over IP On-Board Diagnostics (OBD) and the update of ECU flash memories were the first Ethernet applications for the automotive industry. Ethernet 100BASE-TX was chosen to connect vehicle and diagnostics test (service) equipment and for the reading of diagnostics data and updating of software within a given time frame. Generation 2: Driver Assistance Systems and Infotainment The 2nd generation automotive Ethernet addresses infotainment and camera systems for surround view applications, 3. Future vehicles will consist of more cameras fused with sensor data for higher bandwidth and lower latency. Ethernet based Energy-Efficient Ethernet (IEEE 802.3az) introduces a Low Power Idle (LPI) mode and wake-up 2nd Generation Infotainment and Driver Assistance Systems Energy-Efficient Ethernet (IEEE 802.3az) A/V Bridging Gen 1 Video Communication Interface (ISO 17215) BroadR-Reach (OPEN Alliance) Generations of Ethernet [11] 3rd Generation Ethernet as network backbone Partial Networking A/V Bridging Gen 2 Time-Triggered Ethernet Reduced Pair 1 Gigabit (IEEE...) 20

4 3 Camera and radar for driver assistance system [11] functionality to save energy, when the cameras are not being used. Power over Ethernet (PoE) is also preferred to further reduce wiring harness. Generation 3: Ethernet as Network Backbone While previous generations focus on a certain application domain, Generation 3 of automotive Ethernet will introduce the backbone of the in-vehicle network. A typical backbone is illustrated in 4. This structure represents a scalable solution as each port of a switch can be implemented as 10 Mbps, 100 Mbps, or 1 Gbps without any change in higher protocol layers. A further characteristic of the Ethernet architectures is the usage of backbone network technology, which has to accommodate different data communication classes like diagnostics, video/ audio streaming, and highly dependable control data. BroadR-Reach TECHNOLOGY Initiatives for automotive application of Ethernet have already gained momentum. Broadcom Corp, for instance, has invented an automotive technology known as BroadR-Reach Ethernet, 5. The company has helped set-up the OPEN (One-Pair Ether-Net) Alliance special interest group (SIG) to promote BroadR- Reach as a de facto automotive Ethernet standard. The OPEN Alliance now has over 200 members after being founded in 2010 by BMW, Broadcom, Freescale, HAR- MAN and Hyundai. BroadR-Reach technology uses an unshielded single twisted pair cable and enables multiple in-vehicle systems to simultaneously access information adopting bi-directional communication scheme over a single unshielded twisted pair cable allowing 100 Mbps Ethernet to connect its Driver Assistance Systems cost effectively. It also meets the automotive requirement in terms of EMC, robustness and environmental conditions. Elimination of the need for expensive, cumbersome shielded cabling is expected to help manufacturers to significantly reduce connectivity costs as well as weight. It makes it much easier for the different systems in the car (and outside of the car) to cooperate. German carmaker BMW became the first to apply this technology in a vehicle, Comfort Gateway 1 ECU 1 GW ECU 2 Ethernet in partnership with Freescale Semiconductor and licensee the BroadR-Reach Ethernet technology. The technology was first used in the 360 Camera Parking Assist System of the BMW X5 SUV. The benefits were visible: while the 4th generation BMW 7 Series took 10 hours to upload 81 Mb of data using traditional vehicle network [15], it took just 20 minutes to upload 1 Gb of data to the 5th generation BMW 7 series. Hyundai is another OEM, who has started using BroadR-Reach Ethernet technology in some high-end cars. Fiat is also in line to start using multimedia network on their products. This indicates a trend that is expected to be stronger with time. Ethernet nodes is expected to rise to more than 100 in luxury cars and in Backbone Switch a b c d Gateway 2 Gateway 3 Gateway 4 ECU 1 ECU 1 ECU 1 ECU 1 Chassis CAN LIN FlexRay FlexRay Most 4 Ethernet backbone structure [11] Powertrain ECU 2 ECU 2 ECU 2 Infotainment ECU 2 autotechreview January 2015 Volume 4 Issue 1 21

5 5 BroadR-Reach TECHNOLOGY cars sold in the mass market by Even for entry level cars, the projected number of Ethernet nodes is up to 10. The projections also indicate that the global market for Ethernet ports is expected to reach 300 million by 2020, with North America and Europe contributing the most to the total revenue [13]. CONCLUSION Ethernet is an enabling technology for introducing advanced features into the automotive domain. Major driving force for the use of Ethernet in automotive networks is its higher bandwidth, low cost, scalable and flexible technology that is suitable for both quickly changing platform and different car series. It also reduces complexity due to its hierarchical architecture and backbone bus system. For future technologies like autonomous vehicles, there may be even stronger need for Ethernet, since they would require organisation of millions of lines of data. It is quite natural that demand for invehicle network technologies will keep growing. In fact, it s not possible to set limits for the data rates needed in connected cars of the future. Even today there are specific applications in cars for which the transmitted data rate exceeds 100 Mbps. That is why it is expected that viability of automotive Ethernet will become more and more evident. With the deployment of low-cost automotive Ethernet, it may be possible to offer high-end features like infotainment and ADAS features such as surround-view parking and lane departure warning, which may not be only limited to highend cars. However, many issues need to be addressed for widespread use of Ethernet in automobiles. One important aspect is design of process & tools capable of handling dynamic communication paradigms. Effective filtering strategies to process high data rates (transmission rates are in the Gbps range) and integration of Ethernet in a clear domain architecture with backbone implementation, as a switched network with multiple full duplex connections with established technologies in the automotive industry such as CAN, FlexRay, LIN, and MOST are the other aspects. References [1] This Car Runs on Code; IEEE Spectrum; Read this article on Technology Information, Forecasting and Assessment Council (TIFAC) is an autonomous organisation set up in 1988 under the Department of Science & Technology to look ahead in technologies, assess the technology trajectories, and support technology innovation by network actions in select technology areas of national importance. Send in your feedback to technologyforesight@autotechreview.com spectrum.ieee.org/green-tech/advanced-cars/thiscar-runs-on-code [2] IXia; Automotive Ethernet: An Overview; whitepaper/ixia-automotive-ethernet-primer-whitepaper_1.pdf [3] Eugen Mayer; Serial Bus Systems in Automobiles; PTR/SerialBusSystems_Part2_ElektronikAutomotive_200612_PressArticle_EN.pdf [4] Dearborn Group: [5] SSP_238.pdf [6] Mike Jones; Time is Right for Automotive Ethernet; [7] The case for Ethernet in automotive Communications [8] In-vehicle Networking com/files/microcontrollers/doc/brochure/brinve HICLENET.pdf [9] Challenges in future IP/ Ethernet-based In Car Network for real time Applications [10] Evolution of Ethernet in automotive realm, by- Peter Hank, Thomas Suermann and Steffin Muller, NXP Semiconductors Germany, GmbH [11] Ethernet Technologies; [12] Source Frost and Sullivan: Major OEMs and Tier I Suppliers Work Towards Making Ethernet A Backbone of In-Vehicle Networks [13] Ethernet A Survey on its Filed of Application jsp?arnumber= [14] The case for Ethernet in Automotive communications by Lucia Lo Bello, Italy., seas.upenn.edu/archives/ /keynote.pdf [15] Comparison of FieldBus Systems, CAN, TT CAN, FlexRay and LIN in Passenger Vehicles, of_fieldbus_systems_can_ttcan_flexray_and_ LIN_in_Passenger_Vehicles.pdf 22