PC5 (direct communication interface): the communication interface between terminals, that is, the short-distance direct communication interface between vehicles, people and road infrastructure; It is characterized by realizing low delay, large capacity and high reliability communication through direct connection, broadcasting and network scheduling.

Uu (cellular communication interface): the communication interface between the terminal and the base station; Its characteristics are: realizing long-distance and wider-range reliable communication; Usage conditions of two communication interfaces: Uu interface: when terminal devices supporting C-V2X (such as vehicle terminals, smart phones, roadside units, etc.) are supported. ) It can be used under the control of the cellular network within the coverage of the base station's cellular network; PC5 interface: No matter whether there is cellular network coverage or not, you can use PC interface for V2X communication. C-V2X combines Uu interface and PC5 interface to support each other, forming effective redundancy and ensuring communication reliability.