Abstarct: Significant increases in traffic flow increase the demand for modern technologies that can improve the safety and efficiency of transportation systems. This matter led to the emergence of widespread technologies in the field of intelligent transport systems (ITS). Regarding the importance of road safety in recent years, IEEE 802.11a sets international standards for wireless access in vehicle environments. In general, wireless access in vehicle environments involves two different types of networks that are V2V and V2I. Vehicle communications are categorized as part of Intelligent Transportation Systems (ITS). The vehicle communication system is a communication network that connects vehicles and roadside units. Information transmitted in this type of communication is a warning message and traffic information. The main motive for these systems is safety and avoidance of accidents. Hence, research on car-to-vehicle communications (V2V) and vehicle-to-infrastructure (V2I) has increased. However, in addition to providing new services, VANETs face many challenges in terms of technology, protocols, and security, which will increase the need for research. For example, one of the important issues in these communications is the loss of packets containing important traffic information. The IEEE 802.11a standard, known as interconnect communication protocol, has a lot of efficiency in this regard. The reason for this is that the standard supports a data rate of 54 Mbps in the 5.9 GHz band. Therefore, in addition to the lack of frequency interference, it can provide the ultimate speed to users of local networks. However, in recent years, the IEEE 802.11p revised version of this protocol reduces the error rate of incoming packets by reducing bandwidth of IEEE 802.11a bandwidth. The protocol, known as wireless access in vehicle environments, uses a 10-band MHz channel in the 5.9 GHz band. This dissertation attempts to evaluate their performance in terms of packet error ratio and transmitted bits by simulating the physical laxyer of both IEEE 802.11a and IEEE 802.11p protocols in MATLAB simulation environment and applying a variety of modulations and Changing some parameters including Doppler shift frequency. According to what other researchers have found, our prediction is that the packet error rates improve significantly in IEEE 802.11p. Considering the results of the simulations and comparing the results, it has been observed that the PER value in the IEEE 802.11p standard has decreased. This is an acceptable match for the results obtained.