Biweekly Summary - Mar. 21, 2025

Since our last update, where we explored the metrics for evaluating different protocols and testing methods, we have continued reading more papers to study the performance of different protocols in various scenarios. This time, we focused on researching and summarizing details of the following technologies: Hybrid V2X, 802.11p, LTE-V2X, and NR-V2X.

The goal is to analyze the strengths and weaknesses of these technologies, particularly in terms of latency and packet delivery ratio (PDR), and to explore how they can be applied to real-world scenarios, such as autonomous vehicles and intelligent transportation systems (ITS).

Key Findings from the Papers

• 1. Hybrid V2X

• Paper: “Hybrid V2X Communication Approach using WiFi and 4G Connections”

• Latency: The hybrid approach achieves an average Round Trip Time (RTT) of 31.6 ms, with a median of 2.95 ms when using WiFi 39% of the time and 4G 61% of the time. When 4G usage increases to 85%, the median RTT increases to 20.7 ms.

• PDR: The hybrid approach ensures high reliability by switching between WiFi and 4G based on signal strength and network availability. However, specific PDR values are not explicitly mentioned in the paper.

• Application: This approach is particularly useful in scenarios where network availability fluctuates, such as urban environments with varying WiFi coverage. It ensures continuous communication for intelligent vehicles, even in off-road or rural areas.

2. IEEE 802.11p and LTE-V2X

• Paper: “Performance Comparison of IEEE 802.11p and LTE-V2X Through Field-Tests and Simulations”

• Latency:

• IEEE 802.11p consistently maintains low latency, with an average of 4 ms in Line-of-Sight (LOS) conditions. In Non-Line-of-Sight (NLOS) scenarios, latency increases slightly but remains below 10 ms.

• LTE-V2X exhibits higher latency, ranging from 20 ms to 100 ms, due to its Semi-Persistent Scheduling (SPS) mechanism, which introduces scheduling delays.

• PDR:

  • IEEE 802.11p achieves a PDR of 94% in LOS conditions but drops to 66% in NLOS scenarios when transmission power is reduced.

  • LTE-V2X maintains a high PDR of 89% even in NLOS conditions, demonstrating better reliability over longer distances.

• Application: IEEE 802.11p is better suited for short-range, low-latency applications, such as platooning and collision avoidance, while LTE-V2X is more reliable for longer-range communication, especially in NLOS scenarios.

3. NR V2X

• Paper: “NR V2X: Technologies, Performance, and Standardization” and “NR Sidelink Performance Evaluation for Enhanced 5G-V2X Services”

• Latency:

  • In urban scenarios, NR sidelink latency ranges from 0.5 ms to 1.5 ms, while in highway scenarios, it is lower, ranging from 1 ms to 2 ms.

  • The latency increases with vehicle speed, as higher speeds lead to more frequent resource updates and collisions.

• PDR:

• In urban scenarios, the PDR is around 73% to 88%, while in highway scenarios, it improves to 97% to 99%.

• The PDR is positively correlated with vehicle density up to a certain point, after which it saturates due to increased interference.

• Application: NR V2X is designed for advanced use cases such as platooning, extended sensors, and remote driving, where low latency and high reliability are critical. It is particularly effective in high-speed highway scenarios.

Comparative Analysis

Applications in Real Life

1. Autonomous Vehicles:

• IEEE 802.11p has low latency, so it is suitable for platooning and collision avoidance.

• LTE-V2X and NR V2X are better for long-range communication and advanced driving applications, such as remote driving and extended sensor sharing.

2. Urban Traffic Management:

• NR V2X can be used for real-time traffic updates and cooperative driving in urban environments.

• Hybrid WiFi/4G can ensure continuous communication in areas with fluctuating network coverage, such as tunnels or underground parking.

3. Highway Safety:

• NR V2X and LTE-V2X are better for high-speed highway cases. These two techniques are suitable for long-range communication and they have low latency. These features can ensure safety issues such as emergency braking and lane merging.

4. Public Safety:

• ○ LTE-V2X and NR V2X are good for public safety applications. They can be used for emergency vehicle prioritization and hazard warnings. This is because they have good reliability in NLOS conditions.