| 摘要: | 隨著科技的演變，人們的生活越來越離不開科技帶來的便利，近年來，研究
走勢逐漸導向車聯網，其中車輛與一切事物之間的通訊扮演重要角色。V2X被用來表示車輛對一切(Vehicle-to-Everything)的通訊技術，其中包括了車輛對車輛之通訊(V2V)、車輛對基礎設施之通訊(V2I)、車輛對行人之通訊(V2P)、車輛對網路之通訊(V2N)和其他通訊的場景。
Cellular-V2X (C-V2X)通訊在自動駕駛技術中扮演了舉足輕重的角色，此技術用來支持車輛在Sidelink介面上進行直接的互動。在C-V2X的自主模式(也可稱為mode 2)中，車輛在不需要基站的支持下，可以完全分散式地根據自身需求和環境條件透過基於感測之半持久排程(Sensing-Based Semi-Persistent Scheduling, SB-SPS)來選擇 Sidelink 無線資源。然而在 NR-V2X mode 2 下，這種完全分散式和依靠感測的排程不可能完美，因此資源保留無法完全避免資源碰撞。在 Sidelink 中傳輸的分散式環境通知訊息(Decentralized Environmental Notification Message, DENM)和合作感測訊息(Cooperative Awareness Message,
CAM)因為使用相同頻段，且 DENM 是事件型的訊息，所以會跟週期性傳輸的CAM發生資源碰撞。為了解決這種資源碰撞的情況，C-V2X通訊技術通常會透過經常性的改變資源來做調整，然而這種方式本身就可能導致資源碰撞，進而降低C-V2X通訊的可靠性和效能。
本論文透過三種改變來分別增加CAM和DENM的可靠性和效能，並設置了不同的參數用來比較在不同交通負載下各自的效能。根據模擬結果，可以發現在DENM發起率為0.3時，本論文所提出的方法相較於傳統方法在CAM效能上約有28%的提升，而在DENM方面則約有88%的提升。;With the evolution of technology, people′s lives are becoming more and more inseparable from the convenience brought by technology. In recent years, research has gradually led to the trend of technology related to the vehicle network, which plays an important role in the vehicle network is the communication between the vehicle and
everything. V2X has been used to denote the Vehicle-to-Everything (V2X) communication technology, which includes Vehicle-to-Vehicle communication (V2V), Vehicle-to-Infrastructure communication (V2I), Vehicle-to-Pedestrian communication (V2P), and Vehicle-to-Network communication (V2N) and other communication scenarios.
Cellular-V2X (C-V2X) communication plays a critical role in autonomous driving technology, which is used to support direct vehicle interaction over a Sidelink interface.
In the autonomous mode of C-V2X (also known as mode 2), vehicles can operate in a completely distributed manner without the support of base stations. They can select sidelink wireless resources based on their own needs and environmental conditions through Sensing-Based Semi-Persistent Scheduling (SB-SPS). However, in NR-V2X mode 2, this fully decentralized and sensing-based scheduling cannot be perfect, and thus resource collisions in resource reservation are unavoidable. The Decentralized Environmental Notification Message (DENM) and Cooperative Awareness Message (CAM) transmitted in Sidelink are also subject to resource collisions. In particular, DENM are event-based messages, so they may collision with CAM that are transmitted periodically. In order to solve this resource collision situation, C-V2X communication technology usually adjusts the resources by changing them frequently, however, this way may lead to resource collision, which will reduce the reliability and performance of C-V2X communication.
In this thesis, three changes are made to increase the reliability and performance of CAM and DENM respectively, and different parameters are set to compare their
performance under different traffic loads. According to the simulation results, it can be observed that when the DENM initiation rate is 0.3, the method proposed in this thesis
shows approximately a 28% improvement in CAM performance and about an 88% improvement in DENM performance compared to traditional methods. |
