What's in C-V2X (Cellular Vehicle-to-Everything) (4)?

I. The PC5 interface is a direct communication interface used between terminals in 5G (NR) C-V2X (Cellular Vehicle-to-Everything) technology, allowing direct communication between vehicles, pedestrians, and infrastructure without going through the cellular network. This is crucial for low-latency safety functions in connected cars and autonomous driving (such as collision warning, sensor sharing, and platooning). In the evolution from LTE-V2X to 5G NR-V2X, as shown in the table below, the PC5 interface (based on the network) can provide ultra-reliable, low-latency communication (URLLC) for advanced mobile applications of V2X;

PC5-based C-V2X Mode 4 does not require a cellular network, only two devices are needed: RSU (Roadside Unit) and OBU (On-Board Unit) to deploy C-V2X V2I/V2V/V2P application scenarios, where:

• RSU: The wireless transmission device can provide direct link communication through the PC5 interface without a cellular network. Road signs, traffic lights, and IP camera information within a preset area can be broadcast to vehicles in real time via the RSU. Another practical scenario is that the RSU can be equipped with a SIM card to transmit road information through the cellular network, thus developing more public safety applications.
• OBU: The wireless communication device is installed in the vehicle and enhances the sensor capabilities of autonomous vehicles by communicating directly with RSUs and other OBUs. The OBU is responsible for broadcasting the vehicle's location, direction, and speed information to other preset devices while receiving data from other vehicles as input for its internal algorithms to avoid potential accidents.

II. PC5 supports C-V2X application scenarios. When using C-V2X applications, RSU and OBU devices must be equipped with chipsets compliant with the 3GPP C-V2X standard (such as those from Qualcomm, Intel, Huawei, Datang, and Autotalks).

• PC5-based C-V2X has been field-tested, and many applications have been implemented in commercial deployment scenarios; these application scenarios specifically include:
• SPAT (Signal Phase and Timing Message): A V2I service that integrates traffic signal controllers (light color and remaining time) with remote wireless transmission equipment (RSU), which broadcasts this information to the OBU. The driver or autonomous driving control unit can use this information to decide whether to change routes or accelerate.
• TSP (Traffic Signal Priority): A connected vehicle (V2I) service that allows high-priority vehicles such as ambulances, fire trucks, and police cars to send priority signals when approaching signal-controlled intersections so that they can pass through.
• VRUCW (Vulnerable Road User Collision Warning): A connected vehicle (V2P) service that alerts the driver or autonomous driving control unit when a potential pedestrian collision risk is detected by roadside IP cameras and roadside units (RSUs).
• ICW (Intersection Collision Warning): A connected vehicle (V2V) service that warns the host vehicle of a collision risk when approaching an intersection.
• EBW (Emergency Brake Warning): Another connected vehicle (V2V) service that warns the host vehicle when a remote vehicle ahead performs emergency braking. The host vehicle receives the alert from the vehicle ahead and determines whether a collision will occur.
• DNPW (Do Not Pass Warning): A connected vehicle (V2V) service used when the host vehicle plans to overtake a vehicle ahead from the opposite lane. The host vehicle sends an alert to nearby vehicles traveling in the opposite direction. The host vehicle's on-board unit (OBU) will receive the DNPW message to determine if it is safe to overtake.
• HLW (Hazardous Location Warning): A connected vehicle (V2I) service that warns the host vehicle of potential hazardous situations, such as deep water after heavy rain, potholes on the road, or slippery road surfaces.

All of the above application scenarios are deployed using PC5-based C-V2X direct communication technology; due to performance limitations, 4G (LTE) cellular networks cannot support them. 5G (NR) provides development opportunities for time-sensitive applications.