Decoding Dedicated Short Range Communication (DSRC), the foundation of autonomous driving is here!

Connected Car is one of the hottest research topics in intelligent transportation in various countries in recent years. Its development goal is to create safer, smarter and more environmentally friendly means of transportation.

Among all the conditions required for building a connected car, connectivity is one of the important elements for its realization. Connected cars can provide more convenient driving functions and increase safety during the journey through vehicle-to-vehicle, vehicle-to-roadside unit (VRU) such as traffic signs, vehicle-to-smartphone or other devices.

Connectivity applications for connected cars can be roughly divided into the following three categories:

1. Vehicle-to-Vehicle (V2V) connectivity

Through mutual communication and assistance between vehicles, traffic accidents can be prevented and casualties from traffic accidents can be reduced.

2. Linking Vehicle to Roadside (V2R) and Infrastructure (V2I)

It can provide car owners with real-time and regional traffic information, making the journey convenient and fast.

3. Linkage between cars and other intelligent devices/systems

Connect with other user systems to provide real-time and uninterrupted services, making the riding environment and journey safer and more comfortable.

Currently, the number of new cars equipped with Internet of Vehicles is gradually increasing, but most application services only contact the car manufacturer's back-end system to seek help, or provide navigation and various voice services during driving; but if it involves a higher level, such as application functions related to safe driving, they are still rare.

WAVE/DSRC will become standard equipment in new cars

Regarding vehicle-to-vehicle communication, the United States plans to use Dedicated Short Range Communications (DSRC) technology to achieve it. Although NHTSA has not clearly stated which DSRC communication technology will be used, based on previous research and development and field tests in the United States, the DSRC communication technology it will use should be 5.9GHz Wireless Access for Vehicular Environments (WAVE)/DSRC, including IEEE1609 related protocols and IEEE802.11p technology.

The effective communication distance of DSRC is several hundred meters. Vehicles use DSRC to send information such as location, speed, and direction to other vehicles on the road at a frequency of ten times per second. When a vehicle receives a signal from another vehicle, when necessary (for example, when another vehicle turns at a corner, or when the vehicle in front suddenly brakes or changes lanes), the in-vehicle device will alert the driver with flashing signals, voice reminders, or seat or steering wheel vibrations (Figure 1).

Figure 1 The car computer can provide driver safety warning information through DSRC

To this end, General Motors (GM) has applied for a patent for car seat vibration technology, and Ford has also developed steering wheel vibration technology to cooperate with the vehicle interconnection communication system that may be mandatory.

In addition, if highway facilities such as traffic management signs use DSRC communication technology, they can also communicate with vehicles on the road and inform vehicle drivers of relevant road conditions (such as road congestion, construction, potholes, etc.) so that drivers can change routes or pay attention in advance.

DSRC establishes the foundation for autonomous driving

In 2011, the Michigan Department of Transportation (MDOT) conducted a real-vehicle demonstration test in Oakland County, Michigan. In this real-vehicle demonstration test, nearly 3,000 cars, buses, trucks and motorcycles equipped with DSRC communication devices participated in the test to test the effectiveness of V2V and V2I communications.

The test first connected the vehicle to the roadside device of the traffic light control equipment at the intersection. Through DSRC communication technology, the traffic light at the intersection transmitted the Signal Phase and Timing (SPAT) information to the vehicle. The vehicle then accurately positioned itself based on the Differential Global Positioning System (DGPS)/Global Navigation Satellite System (GNSS). Based on its driving information (vehicle speed, direction of travel, stop line distance) and environmental information (road section length, road speed limit), it estimated and provided the vehicle driver with driving speed recommendations to achieve an application that emphasizes both driving safety and efficiency (Figure 2).

Figure 2 Schematic diagram of broadcasting SPaT information via DSRC

At the International Consumer Electronics Show (CES) held in the United States in January 2014, Ford, General Motors and other major automakers showcased their most advanced V2V communication technologies. According to relevant R&D personnel, the functions of this system are far greater than those of automotive radar, infrared transmission sensing and other technologies, and will become the basis of future self-driving cars; and when the technology enters the commercialization stage, the installation of this system on new cars will only cost more than $100.

Although DSRC is supported by many automakers, including Ford, GM, Honda, Hyundai, Mercedes-Benz, Nissan, and Toyota, officials from the United States Department of Transportation (USDOT) said that it will take at least 10 years for the new technology to be widely used. In addition, although this technology is expected to reduce traffic accidents, it may also cause controversy over the violation of personal privacy. Automotive automation experts said that through the DSRC system, automakers and other related organizations will be able to understand the owner's every move, and the subsequent application and regulation of this technology is still worth observing.

In addition to the United States, European countries and Australia have also begun to research and test DSRC communication technology and develop new application areas. For example, Portugal uses more than 500 vehicles and road side units (RSU) to build a vehicle mesh network covering the entire city, which is used for data transmission in port terminal management systems.

Combined with remote services, the Internet of Vehicles optimizes vehicle management

The aforementioned DSRC connected car applications mainly reduce the occurrence of traffic accidents and casualties by providing mutual driving safety warnings and road condition information. The equipment must have a car machine that supports DSRC communication functions and a roadside unit deployed by the government. In addition, it also relies on government-established regulations for support.

Because most vehicles are not yet equipped with DSRC communication function, and the government has not deployed roadside units in large numbers, major car manufacturers have only begun to connect smartphones, car computers and 3G/4G networks to provide their own Internet of Vehicles services, such as General Motors' OnStar and Volkswagen's Car-Net (Figure 3).

Figure 3 Car-Net service provided by Volkswagen

Taking Volkswagen as an example, some of its vehicles are currently equipped with Car-Net car networking services, which can be roughly divided into several categories, such as Remote Vehicle Access, Safe & Secure, Family Guardian, and Diagnostics & Maintenance.

In terms of "safety protection", when a traffic collision occurs, once the airbag in the car is inflated and popped out, the vehicle will automatically connect to the service center and the customer service staff will immediately notify the relevant emergency units to go for rescue; and when the vehicle breaks down and requires assistance, the owner only needs to press the emergency call button in the car to connect to the service center and obtain appropriate assistance; and when the vehicle is stolen, the service center can also learn the current location of the vehicle and continue to track the vehicle's movements to help the owner find the vehicle as quickly as possible (Figure 4).

Figure 4 Schematic diagram of security guard application

If the car owner lends the vehicle to friends or family members (for example, parents lend the car to their children), the vehicle speed alert (Speed ​​Alert) and boundary alert (BoundaryAlert) can be set to continuously track the vehicle's behavior; when a family member drives over the speed limit or exceeds the boundary, the vehicle will send a warning notification to the owner, allowing the owner to contact the driving family member to pay attention to safety, thereby achieving the "family monitoring" function (Figure 5).

Figure 5 Schematic diagram of family guardianship service

Sometimes the car owner forgets to take the car key with him after parking the car, so he cannot open the door. At this time, the car owner can open the door through the smart phone. Or after leaving the car, he forgets whether the door and lights are closed. At this time, the car owner can use the smart phone to check the vehicle's fuel level, doors, lights, hood, trunk and other vehicle conditions. He can also use the smart phone to check the last parking location and even control the horn, turn on the flash light and other "remote vehicle access" functions (Figure 6).

Figure 6: Mobile phone can query vehicle status through remote vehicle access service

In terms of the "diagnostic maintenance" service, car owners can use the system to check the location of repair shops and make online appointments for maintenance and repairs. They can also use the system to perform remote vehicle diagnosis. The system will regularly send diagnostic reports to car owners via email to ensure driving safety (Figure 7).

Figure 7 Schematic diagram of remote diagnosis and maintenance

Afterword

V2V mode can reduce the accident rate of cars, which is more effective than simply using sensors, radars and cameras. But the principle of using 5.9GHz is the same as using WiFi, and there will be interference. In 2015, a foreign organization published an article to denounce this type of technology, which roughly stated that this technology is very suitable for future driving, but the interference problem is currently unavoidable. Keeping the 5.9GHz band free of interference is a crucial link in vehicle communication. The Automobile Manufacturers Association believes that this band can only be allowed to be open for use when it is proven that V2V and V2I system communications will not be interfered with.

In fact, as early as 1999, the 5.9GHz frequency band was allocated by the Federal Communications Commission (FCC) to ensure public transportation safety. Therefore, this frequency band is not actually reserved by the federal government, but has always been used as a technology for deploying intelligent transportation.

As for car manufacturers, they have the following views:

1. Car manufacturers, universities, and governments are working together to develop V2V and V2I (vehicle-to-infrastructure) technologies, which can allow our so-called "connected cars" to have dedicated frequency bands for instantaneous or continuous communication. The automotive industry has always planned to use a relatively niche, valuable, and efficient frequency band for V2V and V2I, and create a system that can coordinate the operation of tens of millions of vehicles.

2. The automotive industry can support the efficient use of the frequency band and will test whether the 5.9GHz band can be safely shared among unauthorized users.

3. The National Highway Traffic Safety Administration (NHTSA) estimates that V2V and V2I technologies can reduce traffic accident casualties by up to 80%.

4. Connected cars can reduce traffic congestion, saving passengers time and money, while also reducing exhaust emissions when vehicles are idling.

Furthermore, from the above we can know that DSRC must be equipped with two things, a positioning GPS and a car computer with prompt and display functions. We have previously posted about the "God's perspective" problem. V2I (vehicle to infrastructure) uses surrounding construction to make up for problems such as GPS in high-rise buildings or underground passages.

Because the current positioning technology can still have a difference of 5 to 6 meters even in an open area, and on the road it will be the distance of three lanes. Judging from various traffic accidents, many traffic accidents are close-range bumps and collisions. At this time, millimeter-wave radar, infrared and cameras are still needed to solve close-range problems. Therefore, having a variety of technologies to pave the way for car safety will definitely greatly reduce the occurrence of accidents and increase the chance of survival.