September 1, 2017
The global automotive industry seems poised on the brink of a brave new world, where connectivity and sensor technologies come together to create systems that all but eliminate life-threatening collisions and enable automobiles that drive themselves. Collectively known as Cooperative Intelligent Transportation Systems, vehicle-to-vehicle (V2V) technologies open the door for vehicles to share information and interact with each other, as well as with the emerging smart infrastructure. These systems promise not only to make transportation safer and to reduce the environmental impact of automobiles, but also to reduce traffic congestion.
Although the automotive industry’s engineers have laid significant groundwork to make V2V technology a reality, they still have to overcome several major hurdles before the technology can hit the road. As with many other manifestations of the Internet of Things (IoT), V2V proponents still argue over which wireless technology will best deliver connectivity for the application. And once the connectivity is in place, design engineers still must map out measures that will adequately manage the security of this new body of data.
How It’s Supposed to Work
Communications represent the keystone of V2V systems. The current technology builds on a wireless standard called Dedicated Short Range Communication (DSRC), which is based on IEEE 802.11p. Transmissions of these systems consist of highly secure, short- to medium-range, high-speed wireless communication channels, which enable vehicles to connect with each other for short periods of time. Using DSRC, two or more vehicles can exchange basic safety messages, which describe each vehicle’s speed, position, heading, acceleration rate, size and braking status. The system sends these messages to the onboard units of surrounding vehicles 10 times per second, where they are interpreted and provide warnings to the driver.
For these communications to prevent collisions, information has to be shared in real time. To achieve this, V2V systems leverage telematics to track vehicles via GPS, monitoring the location, movements, behavior and status of each vehicle.
V2V systems consist of a GPS module, the onboard processing units and RF transceiver modules. Communication between two vehicles requires two sets of components: one that transmits the safety message and another that confirms receipt and interprets the data.
Smart features of V2V systems promise to enhance driver awareness via traffic alerts, providing notifications on congestion, obstacles, lane changing, traffic merging and railway crossing alerts. Additional applications include the following:
- blind spot warnings;
- forward collision warnings;
- sudden braking ahead warnings;
- approaching emergency vehicle warnings;
- rollover warnings; and
- travel condition data to improve maintenance services.
In the future, V2V systems will represent one part of a larger communication system called vehicle to everything, or V2X. In this ecosystem, each vehicle will communicate with any entity that may affect the vehicle, including other vehicles, infrastructure, pedestrians, smart devices and other networks (see video).
Making V2V Connectivity Work
In performing all these tasks, V2V communications will make high demands on whatever wireless standard the industry harnesses to enable connectivity in the transportation ecosystem. To support reliable messaging services, the technology will have to contend with a dynamic operating environment. High relative speeds between transmitters and receivers will mean that the communications system must support low latency to ensure the effectiveness of safety-related applications. The system will also have to tolerate the high message traffic created by transmissions from multiple sources in congested traffic scenarios.
Fortunately, design engineers can help minimize the effects of these conditions with established software tools. High relative vehicle speeds can be addressed by applying advanced reception algorithms. At the same time, high node density can be handled by using distributed congested control algorithms and by varying transmission power, modulation and coding rate.
What’s the Payoff?
To accelerate V2V implementation, the U.S. Department of Transportation (U.S. DOT) has directed the National Highway Traffic Safety Administration (NHTSA) to issue a proposed rule to standardize the development and implementation of vehicle communications technologies in cars and trucks. The goal is to enable new crash-avoidance applications that the NHTSA estimates could eliminate or mitigate the severity of as many as 80% of non-impaired crashes.
The NHTSA rule proposes requiring V2V devices to communicate through standardized messaging technology. Each device would use DSRC communications.
V2V communications would enhance drivers’ abilities in a variety of situations. For example, the system would provide the driver with the information needed to decide whether it is safe to pass on a two-lane road (to avoid potential head-on collisions), turn across the path of oncoming traffic or proceed through an intersection. In these situations, V2V communications can alert drivers of developing threatening situations hundreds of yards away, when the driver and onboard sensors cannot detect the threat. In addition, V2V systems could enhance the performance of vehicles supporting automated driving functions like automatic emergency braking and adaptive cruise control.
The rule would also mandate extensive privacy and security controls. For example, V2V systems would not exchange information linkable to an individual.
What’s the Holdup?
So with this government action and the compelling applications that V2V offers, why hasn’t implementation of the technology progressed further?
“It’s a chicken-and-egg situation for many OEMs,” says Debby Bezzina, managing director of the U.S. DOT Center for Connected and Automated Transportation at the University of Michigan Transportation Research Institute (UMTRI). “Unless U.S. DOT mandates V2V technology on new vehicles, not all OEMs may put it on their new vehicles. If not everyone has the technology, the benefits will be limited.”
Another obstacle is evolving standards. Most of the standards have been updated based on the lessons learned from the Safety Pilot Model Deployment conducted by UMTRI in Ann Arbor and from Safety Pilot activities conducted by other U.S. DOT subcontractors. There is, however, still discussion around spectrum sharing, which could lead to more changes being made in the standards.
“The success of V2V will depend on the penetration rate of the technology,” says Alessio Filippi, technical director, V2V, NXP Semiconductors. “The need for widespread adoption is why you see governments and other interested groups pushing for standards and why the U.S. government has proposed mandating the technology to break the vicious circle and start saving lives. It is essential that there is agreement on the critical functions.”
The Wireless Standards Debate
Many in the industry, including the NHTSA, thought that the DSRC standard had cemented its place as the official wireless technology of V2V communications. Recent events, however, indicate that this decision is still up in the air.
An alliance of automakers and cellular service providers—including Audi, BMW, Daimler, Qualcomm, Ericsson, Intel and Nokia—advocate cellular standards as an alternative. Because the position of DSRC has not been finalized, some interested parties contend that full consideration should be given to other options.
As defined by the Intelligent Transportation Systems program, DSRC occupies 75 MHz of the wireless spectrum, from 5.85 to 5.925 GHz. This segment of the spectrum consists of seven 10 MHz channels. The standard uses 52 subcarrier OFDM modulation to achieve a data rate of 3–27 Mbps, and its range is estimated to be as much as 300 meters.
DSRC advocates see the technology as the only option currently suitable for direct V2V communication because it is the only proven technology available today. In fact, you can even buy a car with this technology. “DSRC is the only technology tested and proven for safety-critical applications,” says Filippi. “There are no field trials or information from field trials with C-V2x in V2V direct communication modes that are available.”
On top of this, DSRC provides robust performance. “DSRC has low latency required for safety applications,” says Bezzina. “It’s very robust, secure and ready for production. You don’t have dropouts with DRSC like you have when using your cellphone.”
Some engineers, however, dispute that DSRC’s latency is up to the job. Those holding this view contend that the standard isn’t fast enough for collision-avoidance actions.
The real stumbling block for DSRC is concern over the potential overlap of the DSRC spectrum and the upper channels of Wi-Fi. If DSRC’s spectrum band is shared, packet loss could reach unacceptable levels.
Not all V2V developers, however, see spectrum overlap as a problem. “The current allocation of Wi-Fi in the 5 GHz is not an issue,” says Filippi. “The 5.9 GHz channels are currently reserved for V2V application, and Wi-Fi can’t use them.” Even so, the U.S. DOT has begun testing spectrum sharing and investigating methodologies to reduce risk of packet loss.
DSRC’s main competitor is known as cellular vehicle-to-everything, or C-V2X. This technology uses existing 4G cellular standards like LTE for both V2V and V2I (vehicle-to-infrastructure). Using LTE, C-V2X is also a well-developed technology, with both hardware and software available on the market. Although, to date, no one has determined what spectrum would be used.
The biggest problem with C-V2X is that its performance in this application is untried. LTE cannot broadcast vehicle to vehicle directly, and there are also limitations in how it could work in absence of a network.
C-V2X also falls short in terms of safety and security. The cellular technology simply doesn’t have security experience in V2V safety critical applications, and it lacks Automotive Safety Integrity Level certification.
Is It Safe?
Like many emerging IoT devices, security is an issue for connected cars. As a result, a lot of V2V development effort focuses on securing these advanced systems.
Security concerns spring from conditions created by both reality and perception. For the connected car, the scale of security risks increased exponentially as soon as it is connected to the internet. Although cars have always been vulnerable to local attacks, internet connectivity exposed them to attacks from anywhere in the world. Compounding the problem is the fact that cyber attacks on connected cars have the potential to cause serious physical damage.
In terms of perception, many still see cars as mechanical devices, overlooking the fact that in many respects automobiles have almost become extensions of consumer electronics. Today’s car relies on many electronic components—chips running countless lines of software. The components and code combined present a tempting target for cyber attacks. This nascent vulnerability becomes greater when V2V system developers integrate connectivity components adjacent to existing systems that were developed with no attention paid to security issues.
As a result, design engineers need to take additional cybersecurity measures. “Design engineers need to implement strong security measures that provide identity while maintaining privacy, manage keys and protect cryptographic operations while using those keys,” says Derek Bouius, security IP product marketing manager at Synopsys. “These [advanced] operations should all be contained within an isolated hardware environment, creating a security perimeter protected from the rest of the system.”
At the same time, security measures should extend all the way to the chip level. “Subsystems—as in multiple chipsets on a board—cannot have effective security without using chipsets designed to address specific security requirements,” says Bouius. “At a minimum, these security measures must include authentication of instruction code—via a secure boot process—and a hardware-based random number generator. Many more advanced technologies exist to mitigate currently known attacks and threats, including side-channel countermeasures against timing and power analysis, as well as detecting targeted injection of faults.”
Unfortunately, determined attackers are continually finding new methods to compromise systems and extract valuable data. It is therefore critical that designers maintain awareness of the newest technologies.
Designers should take advantage of other countermeasures as well. For example, security can be further enhanced with a secure element to store the private keys. Experts also advocate separating safety-critical and entertainment hardware and software.
Still, existing specifications have already laid much of the groundwork to secure V2V systems. “There are already specifications written to address security,” says Bezzina. “A design engineer should adhere to the Security Credential Management System specifications. “The device should also have a hardware security module onboard. Each message broadcast from any DSRC device is signed by a certificate generated by the Security Credential Management System. If a device is broadcasting without a certificate or with an invalid certificate, the other devices will ignore it.”
Not There Yet
The NHTSA is still on track for adopting DSRC-based V2V systems, according to the notice of proposed rulemaking issued last year. If the government agency makes a final decision in 2019 as planned, a two-year phase-in period would kick in to accommodate manufacturers’ production cycles. This would allow initial installations to begin in 2021, with full compliance required in 2023.
That said, if enough industry heavyweights press for consideration of a cellular option, the entire process could go back to the drawing board. This would mean significant work would have to be done not only on the communications side, but also on the security side. The whole course of V2V’s implementation could pivot on whether the interested parties were willing to put off implementation.
Either way, forward movement is certain to occur. The technology simply has too much to offer. Many see advanced vehicle technologies as the silver bullet that promises to save lives on roadways.
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