## 3 Cooperative Perception Information-Sharing
### The Effect of Network Performance on Cooperative Perception
#### 3.3.3 Congestion Control
When the data packet loss in the communication network reached 5%, broadcasting and receiving messages one time per second, the accuracy of data fusion was about 37% lower than normal. [PERSON] et al. [104] analyzed the impact of packet loss and delay on the blind-spot pedestrian collision system. Under a certain initial longitudinal distance, the higher the PLR, the lower the security, and the higher the initial speed, and the smaller the limit delay. In addition, the performance of V2X communication is highly affected by the communication load, and high channel load levels increase the risk of packet collisions. The vehicle network integrates congestion control algorithms to control the channel load andavoid congestion, mainly including reactive and adaptive methods [105]. These protocols can modify the rate or power of information transmission or even drop packets, changing the transmission of V2X messages, which, in turn, affects the effectiveness of cooperative perception. [PERSON] et al. [106] analyzed the impact of the ETSI ITS G5 network on cooperative perception, including the generation rules of cooperative perception information [84] and the influence of broadcast frequency on communication channels. They evaluated the impact of DCC on cooperative perception by defining a constrained environment for hundreds of vehicles. That is to say, the amount of data generated by cooperative perception can easily lead to the congestion of communication channels, resulting in too much old perception information and reducing the accuracy of perception information [107; 108]. [PERSON] et al. [108] adjusted the network load and optimized the transmission of perceptual objects by filtering the number of objects in the message, including the information about the object itself and low-dynamic objects. However, at the same time, there will be a negative impact on the accuracy of cooperative perception. [PERSON] et al. [109] demonstrated for the first time that incorporating congestion control functions at the access and facility layers can improve perception through cooperative perception and ensure the timely transmission of information. The combination of the DCC access layer and the facility layer in the simulation scene with a market penetration rate of 100% and high traffic density (180 veh/km), whether using the reactive method or the adaptive method, has significantly improved the object perception rate. [PERSON] et al. [110] evaluated the impact of DCC on cooperative perception in dense scenes and compared the two methods of transmitting environmental CPM using only cooperative awareness messages. They pointed out that a high channel load increases the risk of data packet collision, resulting in low data packet transmission efficiency, increased communication delay, and the reduced accuracy and timeliness of vehicle cooperative perception. [PERSON] et al. [111] improved the method of dynamically adjusting the sensor transmission data rate based on the vehicle position relationship and road structure [112]. By autonomously selecting high-probability vehicles to broadcast sensor data, the data of other vehicles' blind spots covered by sensors can be preferentially transmitted. The method reduces radio traffic and enhances real-time situational awareness of other vehicles. Research on transmission power control has a great effect on the improvement of communication performance. Table 8 describes the possible impact of network performance (delay, packet loss, channel congestion, etc.) on cooperative perception.