Cars and trucks are quickly becoming Formula One race cars—at least in terms of data. With more types of onboard devices requiring near-instantaneous data transmission than ever before, engineers and designers are challenged to accommodate the accelerating need for bandwidth and speed.
At the core of just about every innovation today, from advanced driver-assistance systems (ADAS) to collision detection sensors and infotainment systems, is data. Traditional automotive data networking technologies such as controller area networks (CANs), local interconnect networks (LINs), and Media Oriented Systems Transport (MOST) were not designed to support the bandwidth these systems demand. In fact, the need to implement time-sensitive networking (TSN) standards has forced engineers to look outside the automotive arena for alternative transit solutions.
以太网是明显的选择。IT世界的这种主食虽然对汽车并不完全是新的，但由于频率越来越多，出于多种原因而被应用。以太网技术可减少重量的电缆，这不是微不足道的优势。此外，汽车工程师知道，以太网是经过验证的技术，得到了许多设备制造商的支持，并且具有强大的硬件/软件支持生态系统。
然而以太网da不能满足所有要求ta networking performance—which is why there’s also a need for TSN technology. TSN guarantees that high-quality data packets are delivered with low latency, something Ethernet doesn’t natively support. In addition, TSN provides a network-wide clock for packet synchronization across systems, and prioritizes time-sensitive data streams over those of lower priority. Finally, it guarantees a minimum level of availability for emergency transmission.
驱动测试限制
验证用于汽车使用的高速以太网设备是一项复杂的工作。
Automakers, along with in-vehicle device and system OEMs, have stringent requirements for latency, synchronization, conformance, availability, and QoS. These requirements must be met, as consumers must be able to rely on their cars and trucks for safe, reliable performance. The potential cost of failure—not to mention recalls, liability, and damaged reputations—is simply too high.
到目前为止，汽车系统最常用的验证形式是驱动器测试。但是驱动器测试有其局限性。其中最重要的是操作条件的狭窄范围 - 测试数字系统时，现实世界的情况根本不够多样化。
Simulation testing, using a purpose-built testing device, is the better choice for Ethernet-based automotive networks. Simulations offer a greater array of connections, domains, and traffic profiles, giving engineers the ability to create—and repeat, on-demand—virtually any kind of condition they wish. Furthermore, because the operating environment is completely controllable, the user can choose which types and amounts of data to be transmitted, the amount of bandwidth to be allocated to each type, numbers of nodes, and so on. It also allows engineers to reproduce conditions exactly, to determine whether a failure was random or situation-specific.
fo测试模拟器提供现成的测试用例r AUTOSAR, Open Alliance, and Avnu industry compliance, along with European (ETSI ITS-G5) and American (USDoT WAVE-DSRC V2X) government standards. Finally, they ensure that tested components or modules will be interoperable with any other verified hardware or system.
Many types of tests can be conducted with a network simulator, generally falling under two types of methodologies. First is mathematical simulation, a process in which algorithms are applied to calculate and simulate best/worst-case scenarios for packet delays. While mathematical simulation establishes theoretical performance limits, experimental simulation—the second method—delivers practical validation. Experimental simulation uses a combination of hardware and software to simulate real traffic within real networks to determine delays under specific conditions.
Both classes of simulation have their place. Mathematical simulation and analysis can be done virtually, with no network present—while experimental requires an actual network with real devices. Used in concert, they offer the best overall results.
多个测试选项
Within the experimental environment, users have their choice of test conditions. Network simulators support emulation of multiple talkers or listeners on each port, using any combination of TSN and/or non-TSN traffic. In a one-armed setup, the simulator acts as either the talker or listener (used when testing an end point such as an Ethernet transceiver). A two-armed setup, by contrast, is one in which the tester acts as both talker and listener (i.e., testing a switch or bridge). Any number of test scenarios can be staged as well. The following are just a few examples:
在ADAS中模仿听众和说话者：毫无疑问，ADAS设备的性能要求最艰难，因为紧急制动和避免碰撞系统需要紧密限制的延迟。使用网络模拟器，工程师可以可靠地验证这些延迟授权。他们还可以模拟不利网络条件，例如数据超载或多个同时说话者。附加的好处是能够精确记录传输时间和接收时间的能力。
唇部合成的多媒体播放：Media systems often require surround-view images collated from different cameras, or DVD playback on multiple displays, speakers, and headphone ports. Using a simulator, testers can verify a network’s bandwidth reservation, timing, and synchronization for media applications. A simulator can also measure timing variance between one output device and another, in both video and/or audio modes.
Connected car (car-to-X) testing:GPS和其他形式的无线外部车辆信息正在以轻型速度发展。很快，实时的流量数据将成为映射功能的组成部分，使车辆能够自我选择的首选旅行路线。但是，并非所有数据都在重要性上都相等，并且以太网网络必须能够辨别和优先考虑各种流。当存在TSN和非TSN数据时，网络必须能够支持高优先级和最佳实例。同样，当实时功能（例如映射应用程序）与具有QoS要求的音频/视频显示之间进行带宽竞争时，网络必须能够正确响应。模拟器允许测试人员确定网络在这些不同条件下的行为。
模拟器作为长期解决方案
Today, IT and network equipment manufacturers and providers from the aerospace, industrial, and automotive industries are all gearing up to validate higher throughput and worst-case latency for the end-to-end performance of their networks. Whether for plane, train, automotive, or industrial robot applications, test simulators can emulate every kind of network protocol.
TSN希望制定标准以帮助增加基于以太网的系统的确定性，以便工程师可以可靠地验证任何以太网OSI层的系统和设备，从2-3层（符合/性能测试）到4-7层（脆弱性性能）。这些标准将至关重要，因为车辆依靠更多数据来实现可靠的情境意识，并确保任何自主驾驶模式都是安全且平稳的驾驶体验。
拥有正确的测试设备，并选择具有网络验证专业知识的测试合作伙伴，对于应对这些挑战至关重要。随着数据对现代车辆的重要性与过去的石油和汽油一样重要，模拟器将保证每辆车在高峰性能下运行。
Jeff Warra is Senior Technical Marketing Engineer atSpirent Communications。
