  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).
