The Wi-Fi drive‑by

Houman Zarrinkoub, of MathWorks, spells out the complexities of the communication systems needed to connect cars and other road transport systems with internet services, safely and securely.

shutterstock imageVehicular communication is a co‑operative communication technology designed to improve traffic safety, enhance autonomous driving, and advance the objectives of the ‘smart city’.

This technology enables continuous, reliable, high-speed, authenticable interactions between moving vehicles.

Vehicular communication is usually divided into four use cases:

  • communication of vehicles to other vehicles (V2V)
  • communication of vehicles to the road-side infrastructure (V2I)
  • communication of vehicles to pedestrians (V2P)
  •  communication of vehicles to the cellular network (V2N).

Together, these use cases are known as vehicles to everything (V2X).

The benefits

V2X technology is projected to significantly improve transport safety.

According to a report by the US Department of Transportation’s National Highway Traffic Safety Administration, “If V2X technologies alone are widely deployed, they have the potential to address 81% of light‑vehicle crashes”.

V2X technology will provide safety features above and beyond what is offered in other advanced driver assistance systems (ADAS) available today.

Most of these systems rely on computer vision, radar, or lidar technologies.

The main limitations of these technologies are that their signals cannot penetrate through vehicles and no information is available about vehicles that are outside the line of sight. V2X, on the other hand, provides critical information about vehicles that are both inside and outside the line of sight, as long as they are within a certain communication range.

V2X makes both semi‑autonomous driver-based systems and fully automated systems much more situationally aware. This will enable vehicles to co‑operate and reduce accidents in various traffic scenarios.

The market

Automotive V2X technology has a large potential market. Juniper Research reports that it is expected to reach $3bn by 2022, with a 26% annual rate of growth.

It is expected that 50% of new vehicles will be equipped with V2V hardware by 2022.

Vehicle to vehicle (V2V) communication enhances situational awareness. It is applicable to both driver-assisted or automated driving systems.

The market consists of three sectors:

  • Devices/semiconductors – RF transceivers and V2X chipset makers such as Denso, Continental, Delphi, Qualcomm, and Infineon
  • Cellular infrastructure – manufacturers (Huawei, Nokia, and Ericsson) and carriers (AT&T, NTT, and Docomo)
  • Cars – manufacturers such as Toyota and Honda (Japan), GM and Ford (US), and BMW, Daimler and Audi (Germany).

The technology

Two candidate technologies are proposed for the implementation of V2X technology – dedicated short range communication (DSRC) and cellular vehicle-to-any-device (C-V2X) communication.

Both are designed to operate at the 5.9GHz band and must adhere to the following strict reliability and delay requirements:

  • Communication latency – less than 100ms delay
  • Communication range – at least 300m
  • Supported vehicular speeds – typical motorway velocities.

In DSRC, which is a derivative of Wi-Fi technology, communications protocols (PHY and MAC layers) are specified by the IEEE 802.11p standard.

Proponents of this technology are automotive companies such as Toyota, Honda, and GM.

The work on DSRC started in 2009, and its communications protocols were fully characterised by 2010.

According to its supporters, all aspects of DSRC standards from application layer to PHY layer and all safety considerations have been addressed in the past eight years of development. They believe the technology is ready to be deployed on a large scale.

DSRC has known limitations, including support only for the V2V and V2I applications and an upper band of reliability for vehicle density and communication range.

C-V2X is based on 4G-LTE cellular technology. It is part of the device‑to‑device (D2D) communication protocol of the sidelink (proximity server) mode of the LTE-Advanced standard. As such, it enables every device to detect every other device within its proximity directly.

Unlike DSRC, LC-V24 supports the V2N and V2P vehicular communication use cases. Compared with DRSC, it supports higher speeds (up to 250Km/h) and a higher density (thousands) of vehicles. The proponents of C-V2X technology are a consortium of automotive and wireless device manufacturers known as the 5G Automotive Association (5GAA), which includes Audi, BMW, Qualcomm, Denso, Intel, Ericsson, and Nokia.

The 5GAA believes that the cost of developing a DSRC-based solution is far more than that of solutions based on C-V2X. Additionally, the gap in technology advantages between C-V2X and DRSC will widen after the introduction of 5G cellular networks.

So far neither of these technologies has been selected as the mandated V2X technology in any country. It seems likely that both will be adopted and vehicles will be equipped with a smart way to understand and decode data transmitted and received via each of these technologies.

Workflows and requirements

V2X technology practitioners include software and hardware developers, integrators and service providers, and testers and performance monitors.

The main pain points in developing V2X technologies are visualisation, prototyping, and model evolution.

Practitioners need to:

  • Visualise, update, and monitor vehicular dynamics and wireless sensor networks (position, velocity, and acceleration of vehicles in a network; vehicles entering and exiting the network; RF signal strength of each vehicle; status of links between each vehicle; and other system elements).
  • Prototype various collision avoidance and traffic resolution algorithms on V2X chips. This effort 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.
  • Evolve their models and monitor the effect of V2X techniques on overall traffic (status of collision avoidance manoeuvres, overall communications metrics such as delays and throughput, 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.

Simulation for design verification

Before building safety-critical applications and devices like V2X for traffic safety, we must ensure that they work exactly as intended.

Through computer simulations, we can build a model of the system, its components, and its environment and subject the system to rigorous testing.

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.

To generate V2X signals that adhere to either DSRC or C-V2X standards, we need to program wireless modems capable of transmitting and receiving these types of signals.

MatLab add-on products, such as LTE System Toolbox and WLan System Toolbox, provide detailed implementations of C-V2X and DSRC signal processing functions.

Using these functions, it is possible to verify that each modem component works correctly and that the vehicular communications work in realistic propagation scenarios.

Race to driving safety of the future

We live in an exciting time. The landscape of vehicular transport and urban safety is undergoing a fundamental change due to automation.
Intelligent transport systems, such as autonomous cars, are designed to be aware of the events happening around them. These situationally aware systems can respond to movements of other vehicles and pedestrians in real time.

After the number of cars on the road using these types of automated driving features, including V2X, reaches a critical mass, the safety and security of driving will be greatly enhanced.

These advances have the potential to make collisions – and the death, injury, and destruction they cause – a thing of the past.

About The Author

Houman Zarrinkoub is senior wireless product manager at MathWorks

 


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