In recent years, the next generation of wireless communication (5G) plays a significant role in both industry and academy societies. Cellular Vehicle-to-Everything (C-V2X) communication technology has been one of the prominent services for 5G. For C-V2X transmission mode, there is a newly defined communication channel (sidelink) that can support direct C-V2X communication. Direct C-V2X communication is a technology that allows vehicles to communicate and share safety-related information with other traffic participates directly without going through the cellular network. The C-V2X data packet will be delivered to all traffic Users (UE) in the proximity of the Transmitter (Tx). Some UEs might not successfully receive the data packets during one transmission but the sidelink Tx is not able to check whether the Receivers (Rxs) get the information or not due to the lack of feedback channel. For enabling the strict requirements in terms of reliability and latency for C-V2X communication, we propose and evaluate one retransmission scheme and retransmission with different traffic speed scheme. These schemes try to improve the reliability of the safety-related data by one blind retransmission without requiring feedback. Although this retransmission scheme is essential to C-V2X communication, the scheme has a limitation in the performance aspect because of its redundant retransmission. Since radio resources for CV2X communication are limited, we have to detect the effect of retransmission on the performance of the communication system. To the end, the simulator for evaluating the proposed schemes for the C-V2X communication has been implemented, and the performances of the different communication schemes are shown through the Packet Reception Ratio (PRR).
Stochastic Image Transmission with CoAP for Extreme Environments
极端环境中的通信是包括环境监测在内的各种用例的重要研究课题。一个典型的例子是用于6G移动网络的水声通信。这种环境中的主要挑战是极高的延迟和高出错率。它们使得使用现有通信协议的实时图像传输变得困难。这部分是因为在嘈杂的网络中频繁的重传增加了延迟，导致实时性的严重恶化。为了解决这个问题，本文提出了一种随机图像传输与约束应用协议（CoAP）的极端环境。所提出的想法的目标是实现近似实时的图像传输，而无需使用CoAP通过UDP进行重传。为此，图像被划分为块，并且基于要求为每个块分配值。通过块的随机传输，即使当分组在网络中丢失时，也可以保证接收概率而无需重传。我们使用Raspberry Pi 4实现了所提出的方案，以证明其可行性。实验结果证实了所提出的图像传输的性能。
