Comparison of IEEE 802.11p and LTE-V2X: An Evaluation With Periodic and Aperiodic Messages of Constant and Variable Size

Rafael Molina-Masegosa,Javier Gozalvez,Miguel Sepulcre

doi:10.1109/access.2020.3007115

Rafael Molina-Masegosa, Javier Gozalvez + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.3007115

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Abstract

V2X (Vehicle to everything) communications can be currently supported by standards based on IEEE 802.11p (e.g. DSRC or ITS-G5) or LTE-V2X (also known as Cellular V2X or C-V2X) technologies. There has been an intense debate in the community on which technology achieves best performance. However, existing studies do not take into account the variability present in the generation and size of V2X messages. This variability can significantly impact the operation and performance of the Medium Access Control (MAC). This study progresses the state of the art by conducting an in-depth evaluation of both technologies under different message traffic patterns. In particular, we consider aperiodic and periodic messages of constant or variable size based on the standardized ETSI Cooperative Awareness Messages (CAMs). This study considers different scenarios and possible configurations of IEEE 802.11p and LTE-V2X. We demonstrate that IEEE 802.11p can better cope with variations in the size and time interval between messages. We also demonstrate (and characterize) that the LTE-V2X sensing-based semi-persistent scheduling faces certain inefficiencies when transmitting aperiodic messages of variable size. These inefficiencies result in that IEEE 802.11p generally outperforms LTE-V2X when transmitting aperiodic messages of variable size except when the channel load is very low.

Highlights

V2X (Vehicle to Everything) communications are fundamental for generation active traffic safety and management applications
This study focuses on Cooperative Awareness Messages (CAMs) that have been specified by ETSI in [12]
An accurate evaluation of IEEE 802.11p and LTE-V2X requires the use of a CAM generation model that accurately represents the variation in size and time between messages included in the CAM format and generation rules specified by ETSI

Summary

INTRODUCTION

V2X (Vehicle to Everything) communications are fundamental for generation active traffic safety and management applications. The time interval between messages and their size can significantly influence the operation and performance of the MAC in distributed environments where vehicles autonomously select their radio resources In this context, this study advances the state of the art with an in-depth comparison at the system level of IEEE 802.11p and LTE-V2X mode 4 when considering aperiodic messages of variable size that are generated following the ETSI CAM standard. The IEEE 802.11p MAC is not really affected by the size of the messages and whether messages are periodic or aperiodic This is not the case of LTE-V2X since it uses a pre-defined time-frequency structure that conditions the access to the channel as well as the size of packets that can fit in a configured sub-channel. If they do so before TR2 (Fig. 5.b), they will exclude as candidate sub-channels the empty reservation from Va at TR2 since they believe that these sub-channels are going to be used

MESSAGE GENERATION MODELS

SIMULATION ENVIRONMENT

DISCUSSION

Findings

VIII. CONCLUSIONS