## 1 Introduction  
In the future, vehicles on the road will need to frequently exchange information with surrounding vehicles, pedestrians, and road traffic infrastructure, which drives the development of Vehicle-to-Everything (V2X) technology. Today's vehicles have transformed from traditional vehicles into intelligent vehicles. Through the V2X network, there is potential to achieve an Advanced Driver Assistance System (ADAS), improving driving safety and comfort. Recently, the latest beyond 5G and 6G standards have introduced new requirements for V2X, including enhanced demands for sensing accuracy, precision, and resolution, alongside the existing communication criteria of latency, reliability, capacity, and coverage [1]. Therefore, the joint communication and sensing (JCS) system that utilizes a signal to simultaneously achieve two functions has attracted much attention. In previous systems, communication and radar sensing were separate systems using different frequencies and hardware resources. However, with increasingly scarce spectrum resources, there is a need for more efficient utilization of spectrum resources by communication and radar systems. As the bandwidth of commercial communication systemsincreases, coexistence with various existing radar systems is anticipated, leading to the development of the JCS concept [2]. JCS can provide integrated and collaborative gains for future systems [3]. On the one hand, sharing spectrum and hardware resources can lead to high resource utilization efficiency. On the other hand, the sensing function can assist communication in obtaining more accurate channel estimation models, which are beneficial for beamforming and spectrum resource management. 3 GPP Release 16 has established standards for vehicle sidelink communication based on the 5G-NR PC5 air interface, enabling vehicles to communicate directly without the assistance of gNB [4], as illustrated in Figure 1. Sidelink is beneficial for reducing latency and improving communication. In addition, sidelink signals can also be used for near-field positioning, range sensing, and distance measurements [5], thereby complementing or enhancing positioning systems that may be limited by obstacles or other factors, such as network-based positioning or the Global Navigation Satellite System (GNSS). Therefore, the V2X sidelink JCS system has significant development potential. However, due to limited available bandwidth, and without the assistance of a base station, there is a conflicting requirement between radar and communication in spectrum resource utilization. Radar accuracy requires large bandwidth occupancy, which reduces available resources in the resource pool, increases the resource collision probability, and thereby affects the performance of communication. The issue of resource collision in the sidelink scenario is related to resource allocation schemes. Therefore, a flexible and robust resource allocation scheme is crucial for mitigating resource pool conflicts. Traditional sidelink resource allocation schemes are divided into dynamic allocation and sensing-based semi-persistent scheduling (SB-SPS). SB-SPS is widely used for sidelink resource allocation due to its better reliability and latency [6]. The SB-SPS scheme firstly senses the channel quality and selects the available candidate resources and does not select a new resource for the next transmission until the retransmission counter (\(RC\)) returns to zero in order to avoid packet collision during the sidelink communication access. There are also numerous studies concerning modified SPS schemes to improve low-latency  
Figure 1: NG-RAN architecture supporting the PC5 interface. communication [7; 8]. However, the existing research has rarely studied the impacts of packet collision on sidelink sensing performance. According to the theoretical model of Cramer-Rao Lower Bound (CRLB), the resultant SINR of the echo due to collisions will significantly impact the sensing performance of the JCS sidelink.