# Comparative Survey of IEEE 802.11p and IEEE 802.11bd for Vehicular Communication

Paul Muhlethaler

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Paul Muhlethaler. Comparative Survey of IEEE 802.11p and IEEE 802.11bd for Vehicular Communication. AIO Inria Paris. 2025. hal-05474903

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# Comparative Survey of IEEE 802.11p and IEEE 802.11bd for Vehicular Communication

Paul Muhlethaler - AIO Inria Paris

20 July 2025

## Abstract

The rapid advancement of intelligent transportation systems (ITS) has created a growing demand for reliable, high-performance wireless communication between vehicles and infrastructure. IEEE 802.11p was introduced as part of the Dedicated Short Range Communications (DSRC) framework to enable basic vehicle-to-everything (V2X) communication. However, its limitations in terms of data rate, latency, scalability, and support for advanced applications prompted the development of IEEE 802.11bd. This new standard, considered the next generation of vehicular Wi-Fi, enhances the capabilities of 802.11p by integrating features from IEEE 802.11ax, such as OFDMA, MU-MIMO, and 256-QAM, while maintaining backward compatibility. This paper presents a comparative analysis of IEEE 802.11p and IEEE 802.11bd, highlighting their architectural differences, performance characteristics, and suitability for emerging V2X use cases such as cooperative driving, platooning, and high-definition sensor sharing. The goal is to provide insights into the transition path from legacy DSRC systems to next-generation vehicular communication platforms.

## 1 Introduction

With the growing deployment of intelligent transportation systems (ITS), reliable and efficient communication between vehicles and infrastructure—referred to as Vehicle-to-Everything (V2X)—has become a key enabler for safer and more efficient road transport. V2X encompasses various communication
types, including Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I),
Vehicle-to-Pedestrian (V2P), and Vehicle-to-Network (V2N). These systems
aim to reduce traffic accidents, improve traffic flow, and support emerging
applications such as autonomous driving and cooperative maneuvers.

The IEEE 802.11p standard, finalized in 2010, was the first wireless com-
munication protocol specifically designed for vehicular environments. Oper-
ating in the 5.9 GHz band, it is a derivative of IEEE 802.11a, modified to
account for high mobility and rapidly changing network topologies. 802.11p
allows vehicles to exchange safety-critical information with low setup over-
head and was the cornerstone of the Dedicated Short Range Communications
(DSRC) technology in the United States.

Despite its early adoption, 802.11p has shown significant limitations, par-
ticularly in terms of spectral efficiency, data throughput, latency, and perfor-
mance under dense traffic conditions. These shortcomings hinder its ability
to support advanced V2X use cases such as high-definition map updates,
real-time sensor sharing, and coordinated driving.

To address these challenges, the IEEE initiated work on the 802.11bd
standard as an evolution of 802.11p. Officially developed under the Next
Generation V2X (NGV) project, 802.11bd incorporates modern PHY and
MAC layer techniques from IEEE 802.11ax (Wi-Fi 6), including Orthogo-
nal Frequency Division Multiple Access (OFDMA), Multi-User MIMO (MU-
MIMO), and 256-QAM modulation. These enhancements aim to significantly
improve throughput, reliability, and efficiency while ensuring backward com-
patibility with existing 802.11p devices.

This paper provides a comprehensive comparative analysis of IEEE 802.11p
and IEEE 802.11bd. It explores their respective technical foundations, per-
formance characteristics, and applicability to current and future vehicular
scenarios. The objective is to understand how 802.11bd overcomes the lim-
itations of 802.11p and how it positions itself as a key technology for next-
generation vehicular communication systems.

## 2 Overview of IEEE 802.11p

IEEE 802.11p is an amendment to the IEEE 802.11 standard, finalized
in 2010, designed specifically for wireless access in vehicular environments
(WAVE), [1]. It was developed to support Dedicated Short Range Commu-
nications (DSRC) in the 5.9 GHz band, enabling Vehicle-to-Vehicle (V2V)
and Vehicle-to-Infrastructure (V2I) communications for applications such as
collision avoidance, emergency braking alerts, and intersection coordination.

**2.1 Technical Foundations**

IEEE 802.11p is based on the physical (PHY) and medium access control (MAC) layers of IEEE 802.11a, using Orthogonal Frequency Division Multiplexing (OFDM) as its modulation scheme. However, to enhance robustness in high-mobility environments, 802.11p uses a reduced channel bandwidth of 10 MHz (as opposed to the 20 MHz used in 802.11a). This choice doubles the OFDM symbol duration, providing increased tolerance to Doppler shifts and delay spreads common in vehicular scenarios.

The standard supports the following modulation and coding schemes (MCS):

* BPSK with rate 1/2 and 3/4

* QPSK with rate 1/2 and 3/4

* 16-QAM with rate 1/2 and 3/4

* 64-QAM with rate 2/3 and 3/4

This allows for data rates ranging from 3 Mbps to 27 Mbps over a 10 MHz channel.

**2.2 MAC Layer Characteristics**

The MAC layer in IEEE 802.11p is based on the Enhanced Distributed Channel Access (EDCA) mechanism from IEEE 802.11e, which supports Quality of Service (QoS) differentiation by assigning different access categories (ACs) to packets. The contention-based medium access relies on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), which introduces a risk of collisions in high-density scenarios.

Additionally, 802.11p introduces a key feature known as the *Wildcard BSSID*, which allows devices to communicate without prior association or authentication. This is essential in vehicular environments, where connectivity must be established quickly and opportunistically as vehicles enter each other's communication range.
## 2.3 Deployment and Use Cases

IEEE 802.11p has been adopted in several large-scale trials and deployments around the world, particularly in the United States under the DSRC framework [2]. Typical use cases include:

* Basic Safety Messages (BSMs) broadcast for awareness

* Forward collision warning

* Emergency vehicle signal priority

* Road hazard and traffic condition warnings

## 2.4 Limitations

Despite being a pioneering standard, IEEE 802.11p suffers from several limitations that affect its scalability and performance in modern vehicular networks:

* **Low spectral efficiency:** the use of fixed 10 MHz channels and limited MCS options constrain data throughput.

* **High latency in dense networks:** CSMA/CA is not deterministic and performs poorly under heavy load.

* **Lack of advanced PHY features:** no support for MIMO, beamforming, or high-order modulation beyond 64-QAM.

* **Limited future extensibility:** the standard does not scale well to support high-data-rate or cooperative autonomous driving applications.

These shortcomings motivated the development of IEEE 802.11bd as a more capable and forward-compatible vehicular communication standard.

# 3 Overview of IEEE 802.11bd

IEEE 802.11bd is the evolutionary successor to IEEE 802.11p, developed by the IEEE 802.11 Next Generation V2X (NGV) Task Group. It addresses the performance limitations of its predecessor by leveraging advanced features
from IEEE 802.11ax (Wi-Fi 6), while maintaining backward compatibility
with legacy 802.11p systems [3]. The primary design goals include increased
data throughput, reduced latency, improved reliability, better support for
high-density vehicular environments, and compatibility with new use cases
such as cooperative sensing and remote driving.

**3.1 Motivation and Objectives**

While IEEE 802.11p enabled the deployment of V2X safety applications, it
was not originally designed to handle the data volume and latency require-
ments of emerging applications like high-definition (HD) sensor sharing, pla-
tooning, or teleoperated driving. IEEE 802.11bd was thus introduced to:

* Improve physical (PHY) and medium access control (MAC) layer performance.

* Support high-throughput communication in high-mobility conditions.

* Provide robust and deterministic access to the channel.

* Remain interoperable with 802.11p devices to ensure deployment continuity.

**3.2 Technical Enhancements**

IEEE 802.11bd brings several key enhancements over 802.11p:

**1. Modulation and Coding**

While 802.11p supports modulation schemes up to 64-QAM, 802.11bd ex-
tends this to 256-QAM, thereby significantly increasing the peak data rate.
It also adopts modern coding techniques that allow for improved error cor-
rection and reliability over longer distances.

**2. Channel Bandwidth and Aggregation**

802.11bd supports not only the 10 MHz channels used in 802.11p but also
wider channels of 20 MHz and 40 MHz, increasing spectral efficiency. It
allows channel bonding and frame aggregation, which were not available in
802.11p, enabling higher throughput and lower overhead. One might wonder how **IEEE 802.11bd**, designed for high-speed vehicular communication (V2X), can reliably use wide bandwidths such as **20 or 40 MHz** without suffering from severe **Doppler effects**. 802.11bd addresses this Doppler challenge through physical-layer and protocol-level enhancements:

1. **Wider subcarrier spacing**: Compared to traditional Wi-Fi, 802.11bd uses a larger subcarrier spacing (e.g., up to 780 kHz), making each subcarrier less sensitive to Doppler shifts.

2. **Shorter OFDM symbol duration**: A shorter symbol time reduces the impact of time-selective fading and helps track channel variations more efficiently.

3. **Adaptive Modulation and Coding (AMC)**: The system dynamically adjusts modulation and coding schemes based on channel conditions, ensuring robust communication even at high vehicle speeds.

4. **Diversity and redundancy mechanisms**:

* Time and frequency interleaving

* Symbol repetition

* MIMO and beamforming

5. **Operation in the ITS 5.9 GHz band**: 802.11bd operates in the same band as DSRC (802.11p), where Doppler profiles are well-characterized for vehicular environments.

**Summary Table**

<table><caption>Table 1: 802.11bd Doppler mitigation strategies</caption><thead><tr><td>Doppler Issue</td><td>802.11bd Solution</td></tr></thead><tbody><tr><td>High Doppler sensitivity</td><td>Increased subcarrier spacing</td></tr><tr><td>Rapidly varying channels</td><td>Shorter OFDM symbols</td></tr><tr><td>Maintaining reliability</td><td>Adaptive MCS and redundancy</td></tr><tr><td>ICI due to mobility</td><td>Robust synchronization and diversity</td></tr></tbody></table>

These mechanisms mitigate, but do not eliminate, Doppler-related impairments in extreme mobility scenarios.
### 3. MIMO and MU-MIMO Support

Multiple Input Multiple Output (MIMO) and Multi-User MIMO (MU-MIMO) are introduced to increase spatial multiplexing, thereby improving throughput and spectral reuse. These techniques are especially useful in dense vehicular scenarios, such as highways or urban intersections.

### 4. MAC Layer Enhancements

The MAC layer integrates features from IEEE 802.11ax, including Orthogonal Frequency Division Multiple Access (OFDMA), which divides the channel into subcarriers allocated to multiple users simultaneously. This reduces contention and improves channel utilization. Additionally, improved scheduling and QoS mechanisms are introduced to prioritize latency-sensitive traffic.

### 5. Range and Reliability Improvements

To support reliable communication over longer distances and in highly dynamic vehicular environments, IEEE 802.11bd introduces several physical layer enhancements. One such technique is *Dual Carrier Modulation* (DCM), which increases transmission robustness by duplicating modulated data symbols across two subcarriers that are spaced apart in frequency. This spatial redundancy makes the transmission more resilient to frequency-selective fading and interference, particularly in multipath-rich or non-line-of-sight (NLOS) scenarios. Additionally, 802.11bd supports *extended cyclic prefixes* in OFDM symbols, which help mitigate inter-symbol interference caused by multipath propagation. The longer cyclic prefix duration allows the receiver to better distinguish overlapping delayed signals, improving decoding accuracy and system reliability in high-speed and urban environments.

## 3.3 Backward Compatibility with IEEE 802.11p

One of the unique features of 802.11bd is its ability to coexist with 802.11p systems. To achieve this, 802.11bd introduces a dual-frame transmission scheme. Devices operating in mixed environments can first transmit a legacy 802.11p-compatible frame, followed by a high-efficiency 802.11bd frame. This ensures that older devices can still interpret the basic message, while newer devices can benefit from enhanced data.
## 3.4 Target Use Cases

IEEE 802.11bd significantly expands the capabilities of V2X communication beyond the transmission of basic safety messages, which were the primary focus of IEEE 802.11p. By supporting higher data rates, lower latency, and enhanced reliability, 802.11bd enables a broader range of advanced vehicular applications that require real-time, high-bandwidth communication. These include:

* **Cooperative Adaptive Cruise Control (C-ACC) and Platooning:** Enabling vehicles to maintain tight, coordinated formations through continuous inter-vehicle communication, reducing aerodynamic drag and improving traffic efficiency.

* **Real-Time Exchange of High-Definition (HD) Sensor Data:** Supporting the transmission of rich sensor data such as LiDAR point clouds, radar information, and high-resolution camera feeds between vehicles to enhance situational awareness and support cooperative perception.

* **Infrastructure-to-Vehicle Media Streaming:** Facilitating the delivery of real-time map updates, localized traffic data, and HD road condition feeds from roadside units (RSUs) to vehicles for improved navigation and decision-making.

* **Emergency Vehicle Coordination and Remote Driving:** Allowing emergency vehicles to communicate their presence and trajectory in real time, while also supporting remote operation scenarios where vehicles may be teleoperated in complex or hazardous environments.

* **Integration with Automated Driving Functions:** Providing the communication infrastructure required for highly automated driving tasks, including collaborative lane changes, intersection coordination, and coordinated obstacle avoidance.

## 3.5 Standardization Status

The IEEE 802.11bd standard was formally initiated by the IEEE 802.11 Next Generation V2X (NGV) Task Group in 2019, with the objective of addressing the performance limitations of IEEE 802.11p while ensuring backward
compatibility. Over the course of several years, the task group developed and refined the specification through multiple draft versions and extensive performance evaluations, culminating in the finalization of the standard in 2022.

IEEE 802.11bd is now positioned as a key next-generation V2X communication technology, designed to coexist and, in some deployments, complement 3GPP's Cellular V2X (C-V2X) solutions. Unlike C-V2X, which requires cellular infrastructure for some of its modes (e.g., Uu interface), IEEE 802.11bd retains the decentralized, infrastructure-free characteristics of DSRC while significantly enhancing its performance capabilities.

The standard has garnered broad support from leading automotive manufacturers, semiconductor vendors, and network equipment providers. Industry stakeholders are currently engaged in interoperability testing, performance validation, and initial deployment planning. These collaborative efforts are essential to ensuring backward compatibility with existing IEEE 802.11p-based systems and to enabling a seamless transition to the new technology in diverse vehicular environments [3].

# 4 Comparative Analysis

The transition from IEEE 802.11p to IEEE 802.11bd [4] represents a significant technological leap in the evolution of V2X communications. While both standards are intended for vehicular environments, their architectures, capabilities, and supported use cases differ substantially. This section provides both a tabular and analytical comparison.

## 4.1 Tabular Comparison

## 4.2 Analysis of Key Differences

**Spectral Efficiency and Data Rate** IEEE 802.11bd significantly increases spectral efficiency by adopting higher-order modulation (up to 256-QAM) and wider channel bandwidths (20/40 MHz). This enables data rates that are several times higher than those of 802.11p, allowing support for bandwidth-intensive applications such as real-time video sharing between vehicles or cooperative sensor fusion.
<table><caption>Table 2: Comparison between IEEE 802.11p and IEEE 802.11bd</caption><thead><tr><td>Feature</td><td>IEEE 802.11p</td><td>IEEE 802.11bd</td></tr></thead><tbody><tr><td>Standard Release</td><td>2010</td><td>2022</td></tr><tr><td>Base Technology</td><td>IEEE 802.11a</td><td>IEEE 802.11ax (Wi-Fi 6)</td></tr><tr><td>Channel Bandwidth</td><td>10 MHz</td><td>10, 20, 40 MHz</td></tr><tr><td>Modulation</td><td>Up to 64-QAM</td><td>Up to 256-QAM</td></tr><tr><td>Max Data Rate</td><td>27 Mbps</td><td>&gt;100 Mbps</td></tr><tr><td>Access Method</td><td>CSMA/CA</td><td>CSMA/CA + OFDMA</td></tr><tr><td>MIMO Support</td><td>No</td><td>Yes (SU/MU-MIMO)</td></tr><tr><td>Latency</td><td>~10 ms</td><td>&lt; 5 ms<sup>1</sup></td></tr><tr><td>Range Support</td><td>Short to medium</td><td>Short to long (range extension mechanisms)</td></tr><tr><td>Backward Compatibility</td><td>Not applicable</td><td>Yes (with 802.11p)</td></tr><tr><td>Use Case Focus</td><td>Basic safety messages</td><td>Advanced V2X and cooperative driving</td></tr><tr><td>MAC QoS Support</td><td>Basic EDCA</td><td>Enhanced QoS and scheduling</td></tr></tbody></table>

**Latency and Reliability** Low-latency communication is essential for safety-critical V2X services. IEEE 802.11bd reduces latency by introducing more efficient medium access mechanisms and PHY-layer enhancements. Techniques such as OFDMA allow multiple users to share the channel in a more structured manner, reducing collision probability and access delays under high network load.

**Scalability and Network Density** IEEE 802.11p struggles in high-density scenarios due to its reliance on CSMA/CA, which leads to high contention and packet collisions. In contrast, 802.11bd addresses this through more deterministic scheduling mechanisms, better interference management, and MU-MIMO support, which allows simultaneous transmission to/from multiple users.

**Backward Compatibility** One of the design objectives of IEEE 802.11bd is to ensure coexistence and interoperability with existing 802.11p devices. This is achieved through dual frame transmission and other cross-compatibility mechanisms, facilitating gradual deployment without making current infrastructure obsolete.
**Application Scope** While IEEE 802.11p focuses mainly on the exchange of periodic safety messages (e.g., Basic Safety Messages - BSM), 802.11bd extends the scope to support cooperative perception, platooning, remote driving, and advanced driver assistance systems (ADAS). This broadens the potential for intelligent vehicle coordination and automation.

## 4.3 Deployment Considerations

Although IEEE 802.11bd offers significant improvements, its adoption depends on several factors:

* **Regulatory support:** Continued allocation of the 5.9 GHz band for V2X applications is critical.

* **Industry alignment:** Automotive OEMs and infrastructure providers must coordinate rollout strategies.

* **Legacy integration:** Mixed environments with both 802.11p and 802.11bd nodes require careful handling to avoid performance degradation.

IEEE 802.11bd is designed to ease these transitions, but real-world performance and adoption will depend on cooperative efforts across the automotive and communications industries.

# 5 Conclusion

IEEE 802.11p marked a pivotal moment in the development of vehicular communication systems by enabling direct, low-latency wireless communication between vehicles and infrastructure. As part of the Dedicated Short Range Communications (DSRC) initiative, it provided the technical foundation for early deployments of safety-critical Vehicle-to-Everything (V2X) applications, such as collision warnings and intersection assistance. However, with the rapid evolution of intelligent transportation systems and the emergence of more demanding use cases—such as cooperative perception, vehicle platooning, and autonomous driving—the limitations of 802.11p became increasingly apparent.

IEEE 802.11bd was developed in direct response to these limitations. By incorporating advanced features from IEEE 802.11ax, including OFDMA,
MU-MIMO, and support for higher-order modulation schemes, 802.11bd delivers significantly improved throughput, reliability, and spectral efficiency. More importantly, it does so while preserving backward compatibility with IEEE 802.11p, ensuring a smooth and cost-effective transition path for manufacturers and infrastructure providers.

The comparative analysis presented in this paper demonstrates that IEEE 802.11bd is not merely a performance upgrade but a strategic evolution. It is designed to future-proof V2X communications against growing data demands, higher mobility requirements, and increasingly dense vehicular environments. Its enhanced MAC and PHY capabilities make it a strong candidate for enabling advanced vehicular scenarios and integrating with next-generation ITS ecosystems.

Looking forward, the successful adoption of IEEE 802.11bd will depend on harmonized efforts among standardization bodies, automotive OEMs, network equipment manufacturers, and regulatory authorities. Its coexistence with complementary technologies such as C-V2X (Cellular V2X) will also play a critical role in shaping the connectivity landscape for connected and autonomous vehicles.

In summary, IEEE 802.11bd stands as a robust, scalable, and backward-compatible evolution of IEEE 802.11p, offering the performance needed to support the next decade of innovation in vehicular communication.

## References

[1] IEEE Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment 6: Wireless Access in Vehicular Environments, IEEE Std. 802.11p-2010, 2010. [Online]. Available: https://standards.ieee.org/ieee/802.11p/3953/

[2] J. B. Kenney, “Dedicated short-range communications (dsrc) standards in the united states,” Proceedings of the IEEE, vol. 99, no. 7, pp. 1162–1182, 2011.

[3] G. Karagiannis et al., “Ieee 802.11bd for v2x communication: Technical aspects and standardization status,” in 2021 IEEE VTC. IEEE, 2021.
[4] IEEE Draft Standard for Information technology—Telecommunications and information exchange between systems—Local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Amendment: Enhancements for Next Generation V2X, IEEE Std. 802.11bd, 2022. [Online]. Available: https://standards.ieee.org/ieee/802.11bd/7451/