V2X: The design challenges
First publishedin ITS International
Image: jamesteohart | shutterstock.com
The connected future throws up a number of enticing possibilities for us all. But, says Houman Zarrinkoub of MathWorks, issues around visualisation, prototyping and model evolution need to be examined carefully.
We are all aware of the huge amount of investment going into driverless car technologies. With the likes of Volvo, Tesla and BMW getting in on the act, soon they will be a common sight on our roads. However, for this to occur, the vehicles must be able to connect with each other and ensure driver safety. Vehicular communications is a shared communication technology, invented to enhance traffic safety, augment autonomous driving – and to move forward the smart city goals. The technology facilitates consistent, dependable, incredibly fast, authenticable interactions between moving transport. Vehicular communications are usually divided into four use cases:
- communications of vehicles to other vehicles (V2V)
- vehicles to the road-side infrastructure (V2I)
- vehicles to pedestrians (V2P)
- vehicles to the cellular network (V2N)
Collectively, these different uses are defined as vehicles to everything (V2X).
We are set to see a significant improvement in transportation safety because of V2X. In fact, a report by the US Department of Transportation’s National Highway Traffic Safety Administration states: “If V2X technologies alone are widely deployed, they have the potential to address 81% of light-vehicle crashes.” Compared to other advanced driver assist systems (ADAS), V2X technology will offer safety features that go far beyond what is currently available. Many of these ADAS systems depend on computer vision, radar or lidar technologies, which can be a significant problem as these technologies are somewhat limited. For example, their signals cannot penetrate through vehicles, and no information is obtainable about vehicles that are beyond the line of sight. Conversely, as long as the vehicles are within a certain communications range, V2X delivers crucial intelligence about vehicles that are both inside and outside the line of sight. As a result, V2X can make both semi-autonomous driver-based systems and fully-automated systems much more situationally aware. By increasing situational awareness, V2X will enable vehicles to co-operate and lower the number of accidents in different driving circumstances.
Vehicle-to-vehicle (V2V) communication improves situational awareness. It can be applied to both driver-assisted or automated driving systems
There is a huge potential market for automotive V2X technology. In fact, Juniper Research has indicated that it is expected to reach $3 billion by 2022 with a 26% annual rate of growth. It is also predicted that 50% of new vehicles will be equipped with V2V hardware by 2022. The market can be divided up into three different areas:
- Cellular infrastructure: manufacturers (Huawei, Nokia and Ericsson) and carriers (AT&T, NTT and Docomo)
- Devices/semiconductors: RF transceivers and V2X chipset makers such as Denso, Continental, Delphi, Qualcomm and Infineon
- Automobiles: manufacturers such as Toyota and Honda (Japan); GM and Ford (US); and BMW, Daimler and Audi (Germany)
Dedicated short-range communications (DSRC) and cellular vehicle-to-any-device (C-V2X) communications are two candidate technologies suggested for the application of V2X technology. Each is intended to function at the 5.9 GHz band and must comply to stringent dependability and delay conditions as follows:
- Communications range: at least 300m
- Communications latency: less-than-100-ms delay
- Supported vehicular speeds: typical highway velocities
DSRC is essentially an offshoot of Wi-Fi technology. In this type of communication, procedures (PHY and MAC layers) are defined by the IEEE 802.11p standard. Advocates of this technology are vehicle companies including Toyota, Honda and GM. DSRC originated in 2009, when work first began on the technology, and its communications protocols were fully developed by 2010. Champions of DSRC state that all elements of its standards, from application layer to PHY layer and all safety matters, have been dealt with over the previous eight years of enhancement. While there are some known constraints to DSRC - including support only for the V2V and V2I applications and an upper bound of reliability for vehicle density and communications range - supporters of this technology claim that it is on the brink of being deployed on a large scale in 2018. Founded on 4G-LTE cellular technology, C-V2X is part of the device-to-device (D2D) communications protocol of the sidelink (proximity server) mode of the LTE-Advanced standard. Consequently, it allows every device to directly detect each other device within its vicinity. In contrast to DSRC, C-V2X reinforces the V2N and V2P vehicular communications use cases. It does this by supporting greater speeds (up to 250km/h) and higher density (thousands) of automobiles. The 5G Automotive Association (5GAA), which includes Audi, BMW, Qualcomm, Denso, Intel, Ericsson and Nokia, is a group of advocates of C-V2X technology. The 5GAA states that the price of developing a DSRC-based solution is far more expensive than that of solutions grounded on C-V2X. In addition, after the introduction of 5G cellular networks the cavity in technology advantages between C-V2X and DRSC is set to expand. At present, neither technological solution has been chosen as authorised V2X technology in any jurisdiction. It is fairly likely both will be implemented, and vehicles will be armed with an intelligent way to understand and decode data transferred and collected by using each of these solutions.
In dedicated short-range communications, procedures are defined by the IEEE 802.11p standard
Requirements and workflows
Practitioners of V2X technology include integrators and service providers, testers and performance monitors, and software and hardware developers. However, there are some challenges in developing V2X technologies – namely visualisation, prototyping and model evolution. To overcome these, practitioners must:
- Trial selection collision avoidance and traffic resolution algorithms on V2X chips. This initiative involves not only wireless modem operations handling transmission and reception of basic safety messages, but also collision avoidance algorithms and traffic control messages that are processed by the vehicle in real time.
- Advance their models and monitor the effect of V2X techniques on overall traffic (overall communications metrics such as delays and throughput, status of collision avoidance manoeuvres, algorithms to reroute traffic and dynamics of V2X nodes to optimise a given set of criteria) and constantly look for more optimised techniques based on a huge amount of actual field data.
- Update, visualise and monitor vehicular dynamics and wireless sensor networks (velocity, position, and acceleration of vehicles in network; vehicles entering and exiting the network; status of links between each vehicle; RF signal strength at each vehicle; and other system elements).
Design verification procedures
For traffic safety, we must be able to guarantee that they work exactly as intended before building safety-critical applications and devices like V2X. By using model-based design tools such as MATLAB and Simulink, we can visualise, analyse and test various traffic scenarios and vehicular dynamics and test that the V2X system provides collision avoidance as expected. By using computer simulations, we can construct a model of the system, its components and its environment - and subject the system to rigorous testing. To produce V2X signals that follow either C-V2X or DSRC standards, we must programme wireless modems which can transmit and receive these types of signals. Tools that offer detailed implementations of C-V2X and DSRC signal processing functions include MATLAB add-on products such as LTE System Toolbox and WLAN System Toolbox. Using these functions, users are assured that each modem component works properly and that the vehicular communications work in representative propagation situations.
Towards future vehicle safety
As we fully immerse ourselves in the digital world, the current environment of vehicular transportation and urban safety is witnessing a transformative change because of automation. Autonomous cars and other such intelligent transportation systems are intended to be conscious of their surroundings. These situationally aware systems can react to movements of other vehicles and pedestrians in real time. Once many cars on our roads implement these kinds of automated driving features - including V2X - the safety and security of driving will be massively improved. Developments in these technologies have the capability to make automotive collisions, and the associated negative consequences that result from them, a distant memory.