Virtual driving: testing telematics services over cellular networks
01 October 2020
Let’s face it: modern cars have become mobile computing devices on wheels. Many of the services provided by smartphones have been ported or tethered to the infotainment interfaces on board.
This article was originally featured in the October 2020 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.
And as François Ortolan, Lead Solution Architect for Wireless at telecommunications & electronic equipment T&M specialist, Anritsu tells us, in recent years, the industry has moved beyond smartphones and started to build tailored applications and services directly for the automotive industry. These are usually referred to as ‘telematics services’.
Up to present day, vehicles are using applications to exchange the data with the cloud, via a mobile radio network, sharing their position and getting valuable information such as hazard warnings, traffic information or available parking spaces. This allows novel usage of cars, such as car sharing or live carpooling.
The next generation of these applications will provide vehicles with the latest software updates and up-to-date and accurate HD map data for autonomous driving in real time. The applications are now integrated more closely with the vehicle and place high demands on data throughput, latency and reliability of the mobile radio interface.
Telematics services assist the decision-making of the driver, or of algorithms controlling the autonomous vehicle, such as advanced driver-assistance systems (ADAS) systems, which rely on various sensors to make safety decisions. ADAS systems initially began by using sensors such as radar for distance and object sensing. To improve their understanding and representation of the world, they then started to fuse information coming from additional sensors, such as video and LiDAR.
This enables the building of a 3D model of the world surrounding the vehicle. However, one main limitation is its inability to see beyond the line-of-sight. This is where wireless networking can help, as it communicates to infrastructure or between cars. Vehicle connectivity is now becoming an essential addition to safety and the user experience.
Road testing & virtual testing
One approach for testing ADAS and telematics services is to take the vehicle on the road. Road testing requires millions of miles to validate implementations, even though not every situation can be encountered. Reproducibility to test a given scenario is difficult – and testing a given scenario for wireless communication in particular is challenging. The cellular network can fluctuate with the weather, user load and the availability of the required network (LTE, 5G and so on…).
Simulating the world in a lab is one solution to obtain reproducible results. It also cuts the cost and time required to validate releases before going to the road. Road testing is seen as essential, but is often now considered the final step of testing.
Open loop vs close loop
Traditionally, connected cars have been tested in labs, in the same way as a smartphone: building a suite of predefined test cases that can be played sequentially, providing a known input and ensuring that results fall within the expected range or follow the expected behaviour. This is referred to as open loop testing.
However, considering the life cycle and exigence in term of reliability, security and longevity, it has become apparent that this is not enough. A better representation of the real world is needed, moving away from predefined test cases and user scenarios.
This is why virtual driving is becoming an essential tool for pre-validation. In a virtual world scenario, there is a need to replicate the same initial conditions, but the decision made by the vehicle would impact the inputs in real time. This is referred to as closed loop testing.
Software-in-the-Loop and Hardware-in-the-Loop
This methodology – from the automotive world – is named ‘Software-in-the-Loop’ (SiL) or ‘Hardware-in-the-Loop’ (HiL). In both cases, a 3D world is created and scenarios used.
• Software-in-the-Loop provides only a means to test the sensor fusion algorithm in a simulation.
• Hardware-in-the-Loop goes a step beyond the simulation by providing actual emulated stimulus to the sensors hardware platform running the algorithm.
Example of virtual world used in SiL & HiL (dSPACE)
Currently, ‘Software-in-the-Loop’ represent 95% of the virtual driving for autonomous cars. Only 5% is done with ‘Hardware-in-the-Loop’. Trends in the testing industry indicate that more validation is needed when hardware is used.
Testing telematics connectivity to the cloud in HiL
The closed loop approach for telematics testing proposed in this article is new to the industry.
The approach is to equip the HiL with a mobile radio network emulator that provides a realistic test network, consisting of base stations (radio access network) and a mobile radio core network. The HIL simulation can be used to validate the entire chain of effects, from the application in the vehicle to the realistic communication to the cloud service. This article presents a use case from collaboration between two industry leaders, dSPACE for the HiL system and Anritsu for the simulator (2G/3G/LTE/5G).
The Anritsu emulator can be connected directly to the Internet or to a back-end server, and exchanges data between the cloud service and the tested application in the vehicle. Wires or antennas can connect the emulator to the communication unit. With antennas, the radio signals must be appropriately shielded.
It is possible to control the mobile network emulator from the HIL simulator using a Simulink blockset. It allows reconfiguration of the mobile network to manipulate data throughput and latency, for example. It also supports mobility scenarios such as handover (changing from one cell site to another). During a virtual test drive, the radio link is transferred from one base station to the next without losing the data link. Another frequent test case is path loss, where the radio signal becomes increasingly weaker, or even breaks off completely during a drive. The blockset supports the Anritsu MD8475B Signalling Tester (2G/3G/LTE) and is 5G-ready, for use in combination with the 5G communication tester (Anritsu MT8000).
Virtual driving paving the way for type approval
The virtual driving community is actively defining the scenarios needed to validate autonomous cars. Reducing the infinite situations encountered on the road to a subset of essential scenarios is a crucial job. This subset will pave the way for legislators to build a framework to validate the safety of ADAS systems and autonomous vehicles. For now, scenarios focus on environmental conditions that would impact the current sensor inputs such as radar/video/LiDAR.
However, it is expected telecommunications will play an increasing role in the sensor fusion decision-making of autonomous cars in the future. With the evolution of wireless communication in 5G tailored to the automotive needs, more and more features such as Vehicle-to-Everything (C-V2X) will become safety critical. Environmental conditions such as radio coverage will play a key role in defining the scenarios.
One of the most exciting use cases for 5G is sensor sharing and remote driving. A ‘Hardware-in-the-Loop’ system with cellular connectivity is the perfect test bed for research, prototyping and validating 5G features.
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