DSRC Protocol

In this blog post, we will introduce the DSRC protocol, which stands for Dedicated Short Range Communications. DSRC is a wireless communication technology that enables fast and secure data exchange between vehicles and roadside infrastructure. DSRC can support various applications for road safety, traffic management, toll collection, parking guidance and more.

Introduction to DSRC Protocol

The Dedicated Short Range Communications (DSRC) is an open-source protocol for wireless communication, similar in some respects to WiFi.  While WiFi is used mainly for wireless Local Area Networks, DSRC is intended for highly secure, high-speed wireless communication between vehicles and the infrastructure.

Dedicated Short-Range Communications (DSRC) is a wireless communication protocol designed specifically for short-range, high-speed communication between vehicles and infrastructure. It operates in the 5.9 GHz band and was developed to support Intelligent Transportation Systems (ITS) applications, such as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. The main goal of DSRC is to improve road safety, reduce traffic congestion, and enhance the overall transportation experience.

In 2004, the FCC dedicated 75 MHz of bandwidth at 5.9 GHz to be used for vehicle safety and other mobility applications.  DSRC operates in this band and has been developed for over a decade by a range of stakeholders including automakers, electronics manufacturers, state highway departments, and the federal government.  Most work on DSRC has focused on active safety—crash avoidance using driver alerts based on sophisticated sensing and vehicle communications.

What is DSRC Protocol?

The DSRC Protocol is “a two-way short-to-medium-range wireless communications capability that permits very high data transmission critical in communications-based active safety applications,” according to the U.S. Department of Transportation’s Intelligent Transportation Systems Joint Program Office, which heads up much of the research related to DSRC. The Federal Communications Communications Commission set aside 75 MHz of spectrum around the 5.9 GHz band (5.850-5.925 GHz) band in 1999 to be used for vehicle-related safety and mobility systems.

History and Inventions of DSRC Protocol

  1. 1999: The concept of DSRC emerged from the Intelligent Transportation Systems (ITS) initiative in the United States, which began in the 1990s. The Federal Communications Commission (FCC) allocated a 75 MHz bandwidth within the 5.9 GHz frequency band for DSRC in 1999, aiming to support ITS applications.
  2. Early 2000s: DSRC underwent further development and standardization in the early 2000s. The American Society for Testing and Materials (ASTM) and the Institute of Electrical and Electronics Engineers (IEEE) worked on creating DSRC standards, with the latter releasing the IEEE 802.11p amendment in 2010. This amendment, also known as Wireless Access in Vehicular Environments (WAVE), addressed the specific requirements of vehicular environments for communication protocols.
  3. 2012: The United States Department of Transportation (USDOT) conducted the Connected Vehicle Safety Pilot Model Deployment, which was a significant, real-world test of DSRC technology in Ann Arbor, Michigan. The project involved around 3,000 vehicles equipped with DSRC devices, and the findings supported the potential benefits of V2V and V2I communications in reducing crashes and improving traffic efficiency.
  4. 2014: The USDOT announced its intent to move forward with vehicle-to-vehicle communication technology for light vehicles, including the possibility of mandating DSRC technology in new vehicles. However, this effort faced opposition and was not implemented.
  5. 2017: Cadillac introduced the first production vehicle with DSRC capability, the Cadillac CTS sedan. The CTS featured V2V communication technology based on the DSRC protocol, enabling the exchange of information about speed, location, and direction between similarly equipped vehicles.
  6. 2020s: Although DSRC gained some traction, its widespread adoption has been slowed by competing technologies such as Cellular Vehicle-to-Everything (C-V2X), which leverages existing cellular networks for V2V and V2I communications. This competition has led to debates over the optimal communication protocol for connected vehicles.

DSRC Protocol in OSI Layer

The OSI model is a conceptual framework that defines seven layers of communication functions for data exchange between different systems. The three layers of DSRC protocol are:

  • Physical Layer: This layer defines how data is transmitted and received over the wireless medium using radio frequency (RF) or infrared (IR) signals. The physical layer specifies parameters such as frequency, modulation, coding, power and channel access methods. The physical layer standards for DSRC are EN 12253:2004 for RF and ISO 21210:2008 for IR.
  • Data Link Layer: This layer provides reliable data transfer between two nodes on the same network by detecting and correcting errors, framing data packets and managing medium access control (MAC). The data link layer also supports security features such as encryption and authentication. The data link layer standard for DSRC is EN 12795:2002.
  • Application Layer: This layer defines how data is formatted and interpreted by different applications that use DSRC services. The application layer also provides protocols for service discovery, session management and message exchange. The application layer standards for DSRC are ISO 15628:2013 for generic services and ISO/TS 17419:2014 for specific services.

Architecture of DSRC Protocol

The DSRC protocol supports two modes of operation: continuous mode and burst mode. In continuous mode, the vehicle establishes a permanent connection with a roadside beacon and exchanges periodic messages for status update or payment purposes. In burst mode, the vehicle initiates a short-lived connection with a roadside beacon and exchanges one or more messages for information or service requests. The DSRC protocol also supports two types of transactions: symmetric transactions and asymmetric transactions. In symmetric transactions, both parties exchange equal amounts of data in each direction. In asymmetric transactions, one party sends more data than the other party.

The DSRC protocol has been validated by several research projects in Europe, such as VASCO , which tested the interoperability of different DSRC systems from different manufacturers and countries. The DSRC protocol has also been adopted by other regions in the world, such as Japan (ARIB STD-T75) and USA (IEEE 802.11p) , with some modifications to suit their specific requirements.

The DSRC protocol is an important technology for enabling intelligent transportation systems (ITS), which aim to improve road safety, traffic efficiency, environmental sustainability, and user convenience by using advanced information and communication technologies.

The DSRC protocol can support various ITS applications such as electronic toll collection (ETC), cooperative collision warning (CCW), traffic signal priority (TSP), parking guidance (PG), traveler information service (TIS), etc.

DSRC Protocol Stack

At the physical layer (PHY), IEEE 802.11p defines how data is modulated and transmitted over radio waves using orthogonal frequency division multiplexing (OFDM). IEEE 802.11p supports data rates from 3 Mbps to 27 Mbps depending on modulation scheme (BPSK/QPSK/16QAM/64QAM) and coding rate.

At the medium access control layer (MAC), IEEE 802.11p defines how devices share access to the wireless medium using carrier sense multiple access with collision avoidance (CSMA/CA). IEEE 802.11p also introduces enhancements such as:

  • Enhanced Distributed Channel Access (EDCA): which allows devices to use different priority levels for different types of messages.
  • Wave Announcement Service (WAS): which allows devices to announce their channel switching intentions.
  • Wave Indication Service (WIS): which allows devices to indicate their channel usage status.
  • Wave Coordination Function (WCF): which coordinates channel switching among neighboring devices.
  • Wave Short Message Protocol (WSMP): which provides efficient transmission of short messages without requiring higher layer headers.

At higher layers above MAC layer , there are two main options for implementing DSRC applications: using IPv6-based protocols or using WSMP-based protocols.

How does DSRC Protocol works?

DSRC Protocol is a technology that enables wireless communication between vehicles and roadside infrastructure for various applications related to road safety, traffic management and toll collection. DSRC stands for Dedicated Short Range Communications and it uses channels in the licensed 5.9 GHz band to transmit data at high speeds and low latency.

DSRC Protocol has three main communication layers: physical layer, data link layer and application layer. The physical layer defines the radio frequency characteristics, modulation schemes and channel access methods for DSRC. The data link layer provides medium access control and logical link control functions for DSRC. The application layer defines the message formats, protocols and services for different DSRC applications.

DSRC Frequency Spectrum

One of these channels (CCH) is designated as the control channel, which is used for exchanging basic safety messages (BSMs) between vehicles and infrastructure. BSMs contain information such as vehicle position, speed, direction and status. The other six channels (SCHs) are service channels, which are used for transmitting application-specific messages such as traffic alerts, map updates or payment confirmations.

DSRC devices can switch between different channels according to their needs and priorities. For example, a device can send a BSM on the CCH every 100 ms to announce its presence and then switch to an SCH to receive a parking availability message from a nearby parking lot.

To enable interoperability and compatibility among different devices and applications using DSRC technology, several standards have been developed at different layers of the protocol stack. Figure 2 shows an overview of the main standards involved in DSRC communication.

Applications of DSRC Protocol

Dedicated Short-Range Communications (DSRC) protocol has numerous applications, particularly in the realm of vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. The primary goal of DSRC is to enhance safety, efficiency, and mobility in transportation systems by enabling real-time information exchange among vehicles and infrastructure. Some of the key applications of DSRC include:

  1. Collision Avoidance: DSRC can be used to transmit information about a vehicle’s speed, position, and direction to nearby vehicles, enabling them to anticipate and avoid potential collisions.
  2. Intersection Management: DSRC-based V2I communication can help vehicles and traffic control systems exchange information to improve intersection safety, reduce congestion, and optimize traffic signal timings.
  3. Emergency Vehicle Warning: DSRC allows emergency vehicles to send warnings to other vehicles in their path, prompting drivers to clear the way, reduce speed, or take other necessary actions.
  4. Cooperative Adaptive Cruise Control: DSRC can enable vehicles to communicate their speed and acceleration data, allowing them to maintain a safe and efficient distance from each other while adjusting to changing traffic conditions.
  5. Work Zone Warnings: DSRC can be used to send alerts to vehicles about upcoming work zones, lane closures, or other hazards, allowing drivers to prepare and react accordingly.
  6. Electronic Toll Collection: DSRC can facilitate electronic toll collection by enabling vehicles to communicate with toll booth infrastructure,

Advantages of DSRC Protocol

DSRC (Dedicated Short-Range Communications) protocol offers several advantages for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, including:

  1. Low Latency: DSRC provides extremely low latency, typically in the range of milliseconds. This enables vehicles to exchange real-time information quickly, which is essential for safety-critical applications, such as collision avoidance and emergency braking.
  2. High Reliability: DSRC has been specifically designed for vehicular environments and is more robust to interference and signal degradation compared to other wireless communication protocols. This ensures high reliability for critical safety messages.
  3. Dedicated Frequency Band: The 5.9 GHz frequency band allocated for DSRC ensures that the communication channel is free from congestion caused by other wireless devices. This allows for consistent performance and reduces the likelihood of communication disruptions.
  4. Security: DSRC provides a secure communication platform, with built-in security features for message authentication, integrity, and confidentiality. This is important for protecting the privacy of drivers and ensuring the reliability of safety-critical information.
  5. Interoperability: DSRC standards have been developed with interoperability in mind, allowing different manufacturers’ devices to communicate with each other seamlessly.
  6. No Subscription Cost: Unlike cellular-based communication systems, DSRC does not require a subscription or a connection to a cellular network. This means there are no ongoing costs associated with its use, making it more affordable for both consumers and infrastructure providers.
  7. Scalability: DSRC is a scalable technology that can accommodate a large number of vehicles and roadside infrastructure devices without causing congestion or performance degradation. This makes it suitable for dense traffic environments and large-scale deployments.
  8. Range and Coverage: DSRC has a communication range of up to 1000 meters, which is suitable for many V2V and V2I applications. This range allows vehicles to communicate with each other and infrastructure devices over a wide area, enhancing situational awareness and improving safety.
  9. Support for Multi-Channel Operation: DSRC can operate on multiple channels simultaneously, allowing different types of messages (e.g., safety, traffic, and infotainment) to be transmitted concurrently without interference. This feature enables efficient use of the available spectrum and supports a wide range of applications.
  10. Ad-Hoc Networking Capabilities: DSRC devices can form ad-hoc networks, enabling vehicles to communicate directly with each other without relying on a fixed infrastructure. This feature is particularly useful in areas with limited or no infrastructure coverage.
  11. Despite these advantages, DSRC faces competition from Cellular Vehicle-to-Everything (C-V2X) technology, which leverages existing cellular networks for V2V

Disadvantages of DSRC Protocol

While DSRC (Dedicated Short-Range Communications) has several advantages for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, it also has some drawbacks:

  1. Limited Range: DSRC has a communication range of up to 1000 meters, which might be insufficient for some applications or in situations where vehicles are traveling at high speeds.
  2. Competition from C-V2X: Cellular Vehicle-to-Everything (C-V2X) technology has emerged as a strong competitor to DSRC. C-V2X leverages existing cellular networks for V2V and V2I communications, potentially offering greater coverage and more seamless integration with other connected devices and services. This competition has led to uncertainty regarding the future of DSRC, as some stakeholders may choose to invest in C-V2X instead.
  3. Infrastructure Costs: While DSRC does not have subscription costs like cellular-based systems, it still requires significant investment in roadside infrastructure to enable V2I communication. This could be a barrier to widespread deployment, especially in areas with limited resources.
  4. Line-Of-Sight Dependency: DSRC communication relies on line-of-sight between communicating devices, which can be hindered by obstacles such as buildings or large vehicles. This limitation may reduce the effectiveness of DSRC in certain scenarios.
  5. Spectrum Sharing Concerns (continued): Although DSRC operates on a dedicated frequency band (5.9 GHz), there have been debates about sharing this spectrum with other wireless technologies, such as Wi-Fi. If spectrum sharing is implemented, it could lead to increased interference and reduced performance for DSRC devices.
  6. Slow Adoption: DSRC has faced slow adoption due to the competition with C-V2X and the lack of a clear mandate for its implementation in vehicles. This has resulted in a limited number of vehicles equipped with DSRC devices, reducing the overall effectiveness of the technology.
  7. Standardization Challenges: While efforts have been made to standardize DSRC technology, it still faces some challenges with regard to global harmonization. Different countries may adopt different standards, which could hinder the seamless operation of DSRC devices across borders.
  8. Security and Privacy Concerns: Although DSRC incorporates security features, it still faces potential threats from hackers and malicious actors. Additionally, there are concerns about how the data generated by DSRC devices is stored and used, raising privacy issues for drivers and passengers.

Future Development and Enhancement of DSRC Protocol

Despite the competition from Cellular Vehicle-to-Everything (C-V2X) technology, DSRC (Dedicated Short-Range Communications) still has potential for future development and enhancement. Here are some areas where DSRC can be improved and evolved:

  1. Enhanced Spectrum Efficiency: Future development of DSRC could focus on improving spectrum efficiency through advanced modulation and coding techniques, dynamic spectrum allocation, and better interference management. This would enable DSRC to support more users and applications within the available frequency band.
  2. Improved Reliability and Robustness: Enhancements to the DSRC protocol can be made to improve its reliability and robustness, especially in challenging environments such as urban canyons or during adverse weather conditions. Advanced error-correction algorithms, adaptive transmission techniques, and better network management could help achieve this.
  3. Global Harmonization of Standards: Ensuring global harmonization of DSRC standards would enable seamless cross-border operation and promote wider adoption of the technology. Collaborative efforts among different countries and standardization organizations could help create a unified set of DSRC standards.
  4. Advanced Security and Privacy Features: Addressing security and privacy concerns is crucial for the success of DSRC. Future development should focus on enhancing security features, such as encryption and authentication, and developing robust privacy-preserving mechanisms that protect users’ sensitive information.
  5. Integration with Other Communication Technologies (continued): To leverage the strengths of different communication technologies, future development of DSRC could focus on integrating it with other protocols, such as C-V2X, Wi-Fi, or 5G. This would allow DSRC to be used in conjunction with other systems to provide enhanced connectivity, coverage, and functionality for a wider range of applications.
  6. Expansion of Applications: DSRC could be further developed to support additional use cases beyond safety and traffic efficiency. These might include infotainment, telematics, or fleet management applications. By expanding the range of supported applications, DSRC could become more appealing to automakers and consumers.
  7. Improved Hardware: Future enhancements to DSRC devices could focus on making them smaller, more energy-efficient, and more cost-effective. This would make DSRC more accessible and facilitate wider adoption.
  8. Machine Learning and AI Integration: The integration of machine learning and artificial intelligence (AI) techniques could help improve the performance and functionality of DSRC systems. For example, AI algorithms could be used to optimize spectrum utilization, enhance communication reliability, or predict and mitigate potential safety risks.
  9. Cooperative Intelligent Transportation Systems (C-ITS): DSRC can play a significant role in the development of Cooperative Intelligent Transportation Systems, which involve the collaboration of vehicles, infrastructure, and other road users to create safer, more efficient transportation networks. Further development of DSRC technology and integration with other communication
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