The car as entertainment console. The car as internet terminal. The car as autonomous travel appliance. Our concept of what a car is and what it does is being turned upside down, and it is advanced communications, sensing and control technology which is causing the disruption.
At the core of the new vision of automotive design is data. In modern vehicles, huge amounts of data move around the car, and between the car and the outside world: movies are streamed to high-definition displays in the rear headrests, radar ranging signals support collision avoidance systems, and surround-view cameras feed multiple images to the driver information display.
Legacy automotive networking technologies, such as CAN, LIN and MOST, simply do not offer the bandwidth and speed to support this huge amount of traffic. So the automotive industry has turned to Ethernet, the same high-speed networking technology which connects PCs and workstations to servers in millions of offices around the world, to carry data around the car.
In a car, safety and quality of service are critical. For instance, the radar signals detecting that a car is approaching the vehicle in front dangerously fast, have to be received with zero latency. And the images from multiple cameras that are stitched together to make a surround-view image must be synchronized with split-second precision. For this reason, automakers are starting to adopt a flavor of Ethernet called Time-Sensitive Networking (TSN). TSN is a set of protocols intended to guarantee the availability, latency and bandwidth of safety- and mission-critical networks. In theory, a network built with elements that conform to the TSN standards will ensure the reliable and timely transmission of data to safety, entertainment and information systems.
Does it do so in practice, though? Car makers and automotive system OEMs have to be sure that the Ethernet TSN networks they design and manufacture conform to the TSN standards, and that – in any foreseeable circumstances – they behave in a way that ensures the safety of the driver, passengers and other road users.
In the automotive industry, the most commonly used form of testing for automotive systems is the drive test. But drive testing only exposes a network system to the limited range of operating conditions encountered in any given drive test scenario.
In the world of enterprise computing, simulation testing is the preferred method for testing and verifying network performance. The benefits of simulation testing with a dedicated network simulation tester apply equally to automotive systems:
- Test conditions can be easily reproduced
- Operating environment is completely controlled – user can choose the types and amounts of data to be transmitted, amount of bandwidth to be allocated to each type, number of nodes, etc.
- Results may be easily viewed and analyzed, and the test set-up modified using an intuitive test configuration tool
Any operating conditions that can be imagined may be tested with the use of a simulation tester such as the Spirent Automotive C1 or Spirent Automotive C50 and their supporting test suites and software. This test equipment allows automotive manufacturers to leave nothing to chance, and to verify in the laboratory network behavior that might be hard or impossible to test on the road.
More on measuring Latency:
TSN specifications are defining ways to enable zero congestion loss of time-critical data flows. But loss due to congestion is only half of the issue, as network designers and architects also must measure worst-case end-to-end latency within the network. Latency measurements must also consider primary and redundant flows during fault recovery conditions. This is to be able to measure normal vs redundant data path flows in a live network because it is extremely critical to industrial motor control applications. Using the Spirent emulated devices, you can quickly check the Best Clock Master Algorithm (BCMA) inside real devices on the network to ensure they recover from faulted conditions.
Testing the network with a mix of real devices and Spirent’s Emulated Devices with gPTP functionality will enable designers to find out what scenarios help them to optimize and check network traffic to ensure no loss of time-critical data flows. This is achieved using Spirent embedded counters and timers, with over 40 measurements tracked in real-time for each received stream including:
- Advanced sequencing: In-order, lost, reordered, late and duplicate
- Latency: Avg, min, max and short-term avg; first/last frame arrival timestamp
- Latency modes: LILO, LIFO and FIFO
- Data integrity: Generate Errors: IP checksum, TCP/UDP checksum, frame CRC, embedded CRC and PRBS bit errors
- Histograms: Jitter, Inter-arrival, Latency, Sequence
Spirent provides a test bed that emulates, measures and impairs gPTP networked devices using industry proven techniques and products to help develop robust products with accurate timing. To learn more about Spirent solutions, visit: www.spirent.com/automotive
Written by Jeff Warra