802.11p: Advantages and Disadvantages Explained

Introduction : 802.11p, also known as Wireless Access in Vehicular Environments (WAVE), is a communication standard designed for vehicle to vehicle (V2V) and vehicle to infrastructure (V2I) communication. It enables low latency data exchange crucial for intelligent transportation systems (ITS) and road safety applications.

What is 802.11p?

This standard is an adaptation of 802.11a standard, modified to address requirements of vehicular networks requiring high speeds and rapidly changing network topologies. It is a key component of Wireless Access in Vehicular Environments (WAVE) and Dedicated Short Range Communications (DSRC) architectures. Following are some of the features of 802.11p.

• Operating band : 5.9 GHz (licensed)
• Channel bandwidth : 5 MHz, 10 MHz, 20 MHz
• Vehicle speed : Supports up to 260 Km/h
• Coverage range : Approx. 1 Km
• Data rates : Up to 27 Mbps (Using 10 MHz), Up to 54 Mbps (20 MHz)
• Modulation : Supports various schemes including BPSK, QPSK, 16QAM etc.
• Network topology : Direct Ad-hoc communication

Advantages of 802.11p

Following are some of the benefits of 802.11p.

1. It offers low latency communication which is critical for safety applications. 802.11p standard is designed to achieve complete multiple data exchanges within 50 ms time frame. This rapid communication is essential for features like collision avoidance, emergency brake light alerts, lane change warnings etc.
2. It offers robustness in high speed environments by designing appropriate physical layer to perform reliably in such scenarios. Use of 10 MHz channel bandwidth by 802.11p physical layer will help signal to become more resilient against doppler effect and multipath fading.
3. 802.11p enables direct V2V and V2I communication without need for centralized access point (AP). This feature allows spontaneous and efficient network formation crucial for transient communication scenarios between moving vehicles.
4. The operation of 802.11p in the dedicated 5.9 GHz band helps to minimize interference from other wireless technologies. This dedicated spectrum is vital for ensuring the reliability of safety critical messages

Disadvantages of 802.11p

Following are some of the limitations of 802.11p.

1. A significant drawback of 802.11p is its limited scalability in scenarios with a high density of vehicles. In congested traffic, the Carrier Sense Multiple Access (CSMA) based MAC protocol can lead to high percentage of packet collisions as many vehicles try to access the channel simultaneously.
2. Compared to cellular technologies like LTE-V2X and 5G, 802.11p has a shorter communication range. While it supports communication up to 1 kilometer, its effectiveness can be significantly reduced in non line of sight (NLOS) conditions, such as in urban environments with buildings and other obstructions.
3. Although designed for mobility, the performance of 802.11p can still degrade at very high relative speeds between vehicles. Reliability of communication link is impacted by rapid changes in network topology and doppler effect.
4. Being an older standard, 802.11p lacks some of the more advanced features found in newer communication technologies. For instance, it does not have the sophisticated resource allocation and interference management mechanisms that are part of cellular V2X standards

Conclusion: While 802.11p offers fast, direct communication and proven interoperability for V2X systems, it also faces limitations such as range constraints and potential interference. Newer technologies such as C-V2X or 5G are being integrated for future automotive communication.