Testing challenges for V2X Devices
The concept of the “connected car” is a relatively new expression that has emerged as cars have gradually increased their ability to communicate. Science fiction has for many years predicted communicative and self-driving vehicles, and developments in connectivity should make them a reality in the near future. The complexity of the modern automobile ecosystem continues to increase as more and more technology is added in areas from communications to safety systems. Adding the numerous features required for driving assistance, followed by those that allow fully autonomous driving, will pose questions of safety and reliability, and the only way to guarantee device performance and coexistence is by performing intensive testing all the way from development up to production, including conformance and interoperability or field testing.
Challenges in V2X device testing
V2X (“vehicle to everything”) devices include not only V2X communication capabilities but also navigation, telematics, infotainment and other security elements. When considering test requirements, interference from other services must also be taken into account.
Satisfying stringent requirements becomes mandatory to guarantee interoperability and performance in these applications. Regulations, conformance test specifications and type approval are constantly evolving, and include security aspects to protect against cyber-attacks.
An ideal test solution for V2X device testing should include the following elements:
- Cost efficiency: Field testing is likely to be prohibitive for time and cost reasons. Developers therefore face a challenge to define how much testing, within budget, is enough.
- Flexibility: Typically, as more test categories need to be filled, the list of test equipment required mounts up and so does the cost. A single and flexible test solution is the ideal approach.
- Long-term adaptability: V2X systems are constantly evolving. Device manufacturers will not want to change a complete test system every 2-3 years to cater for new developments.
Four goals in V2X device testing
The main purpose of testing is to ensure that the design conforms to the design specifications from component-level design to the system level, and from the antenna RF performance to the protocol or security aspects. In general, tests fall into four different categories, each demanding a different approach:
R&D testing
Unlike other technologies, V2X devices involve a high number of protocol implementations, where each device vendor has decided to implement a different stack supporting ETSI, US or Japanese standards. At the early R&D stage, the implementation needs to be tested as well as the radio system for functionality and performance. This means that a complete test solution should include the following capability:
- evaluating response to real-world challenges such as radio channel impairments, obstacles to reception, and both deliberate and accidental cyber attacks
- including other on-board units (OBUs) and roadside units (RSUs) to scale up the complexity of the environment, and see how systems cope with a changing variety of V2X signals at once
- finding failure points by pushing the system beyond its limits, to evaluate its tolerances and discover how it behaves
- capturing how the device under test (DUT) behaves, with clear reporting to enable performance comparisons and confirm whether it responds as expected
- testing at component and system level including both software-in-the-loop (SiL) and hardware-in-the-loop (HiL) systems, as appropriate
With support for all three different protocol stack implementations (US, European and Japanese), the Anritsu V2X Message Analysis Software allows users to perform tests in detail and confirm device compliance to the local regulations. The software supports message decoding functions from the physical layer up to the application layer, displaying in a tree view the details of every packet captured during the test (Fig.1).
The Anritsu MS2830A/MS269xA Vector Signal Generator hardware can be used to generate or replicate live scenarios in the laboratory. Fading test scenarios such as those defined in ETSI TS 103 257 are also supported.
Interoperability and field testing
Interoperability events aim to provide essential feedback to technical committees to help improve the standards and to accelerate the standards-making process, and several events are organised every year in the different regions. These events also enable engineers to get together to test the interoperability of their implementations: a process which can reduce a product’s time-to-market. In addition to interoperability, each commercial device has used a high number of hours of field testing to guarantee that its performance is not affected when the device is taken out of the laboratory or computer simulations, and put into real operation mode involving uncontrollable external factors.
One issue that engineers face in test events or during field testing is the need to record and replicate field situations in the laboratory. A capture and replay system such as that available in the Anritsu MS2830A and MS269xA Signal Analyser series can be used to capture, store and replay data in the laboratory or in the field in a single-box solution. Furthermore, using the Anritsu V2X message viewer, the captured data can be analysed and debugged packet by packet (Fig.2).
Conformance and regulatory testing
V2X devices are designed to communicate with other elements of the road, with other wireless devices coexisting in the same or adjacent spectrum, and most importantly with each other. Device manufacturers therefore need to agreed and conform to a standard set of standards and regulations.
In Europe and the US, the protocol stacks have the same common blocks or functionality, but have completely different implementation (Fig.3).
The main characteristic of conformance test systems is their complexity, but these systems are constantly being updated as the technology evolves. One future use case could be cellular V2X. Under these circumstances, a test solution that does not rely on commercial “golden radio” solutions for the access layers offers benefits as standards are updated or move towards a different radio access technology.
on the MS2830A and MS269xA Signal Analyser Series and
supports all RF transmitter and receiver test cases
for US, Europe and Japan regulations
Production testing
As a manufacturer ramps up to maximum production capacity, fast, reliable and cost-effective test equipment become highly valuable. The Anritsu MT8870A Universal Wireless Test Set makes use of a special operation mode for rapidly testing devices in production lines, the so-called non-signalling mode or test mode. The MT8870A is a modular, flexible and multi-standard platform for RF testing. The modular design cuts down extra costs while at the same time reducing its footprint in production.
Its VSG (Vector Signal Generator) can generate signals from 10 MHz to 6 GHz with 160 MHz bandwidth. Similarly, the VSA (Vector Signal Analyser) can analyse signals within the same frequency range and bandwidth, while the in-built CPU and memory ensures fast capture and analysis of signals. The software provided for manual/R&D testing (Figure 5) and the fully automated software for production testing minimizes time to production.
Conclusion
A large number of car manufacturers, system board makers and service providers in the automotive ecosystem have announced formal plans to develop autonomous driving technology, and it is becoming clear that telecommunications between vehicles will play an important role in the future, changing the concept of “intelligent car” towards “autonomous car”. Trials are currently being conducted in America, Asia and Europe based on IEEE 802.11p or 3GPP Cellular-V2X.
V2X test solutions are now available that can be used for system validation and performance benchmarking up to production line testing, with significant reductions in costs, measurement uncertainty and the time associated with extensive field testing. It is now possible to analyse and replicate real-world traffic scenarios in the laboratory, with full support for Europe, US and Japan protocol stacks. These RF and protocol conformance test solutions are ideal for in-house pre-conformance testing. In production or final device verification, a multi-standard solution for production provides fast and low-cost device testing according to international standards.
Vehicular communications are shifting from one-way to any-way, and the automotive industry must deliver advanced connectivity services to meet customer demand. With a complete range of RF and wireless testing solutions, users can now design and implement sophisticated vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2X) communications services.
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