# Modeling and Performance of the IEEE 802.11p Broadcasting for Intra-Platoon Communication
## 1 Introduction  
With the support of cooperative adaptive cruise control (CACC) for automated driving and the assist of vehicle ad-hoc network (VANETs) for intra-vehicle communication, a series of succeeding vehicles form a platoon [1; 2]. Driving vehicles in platoon patterns brings many benefits [3; 4; 5]. Road capacity can be enhanced while traffic jams can be lessened considerably because each vehicle moves at a constant speed and maintains a constant small intra-vehicle distance ahead. Besides, since the streamlining of a platoon can diminish air drag, the platoon pattern can decrease both energy consumption and exhaust emissions. Furthermore, with the assistance of advanced technologies, it is considered that driving in a platoon pattern is more secure and more comfortable. The Federal Communications Commission allocated 75 MHz of bandwidth in the 5.9-GHz band for Dedicated Short Range Communications (DSRC) to assist intelligent transportation system (ITS), such as platoon. The overall bandwidth is divided into seven 10-MHz channels including one control channel (CCH) and six service channels (SCHs). Safety-related messages (e.g., road warning, vehicle speed, and vehicle acceleration) only are transmitted on CCH, while non-safety information (e.g., weather condition, media access, and mobile Office) are conveyed on SCHs. In present IEEE standards, the only standard medium access protocol for VANETs is IEEE 802.11p. This protocol was presented based on the existing 802.11 standard to meet requirements of Vehicle To Vehicle (V2V) and Vehicle To Infrastructure (V2I) communications in a high mobility VANETs environment. The broadcast communication model is widely applied in V2V communications to notify the neighbor vehicle ofsafety-related messages because of highly dynamic topology and low delay constraints in VANETs. There are many studies focusing on the communication scheme [6; 7; 8; 9]. Those are presented based on IEEE 802.11p and aiming to achieve low dissemination delay and improve the VANETs performance. The core of platoon control is to ensure the stability of platoon, i.e., spacing errors do not amplify as they propagate upstream from one vehicle to another [10]. The preceding vehicle's speed, position, and acceleration sent through intra-platoon communication are adopted as inputs in vehicle controllers to achieve simultaneous stabilization of vehicles of platoon. The primary assumption holding in the previous studies focuses on platoon control is that the vehicle controllers acquire timely and accurate information [11; 12; 13]. However, many published studies have indicated that the communication performance has a significant effect on vehicle control [14; 15; 16; 17]. The increases of communication delay and packet dropping rate lead to a decrease of the safety and comfort of the platoon. Inspired by this, many studies have been conducted on platoon control considering the effect of communication. [PERSON] et al. proposed a novel control and scheduling algorithm considering fixed communication delay [18]. [PERSON] et al. investigated issues of communication and control of a platoon limited by capacity constraint and packet dropping in VANETs environment [19]. [PERSON] et al. introduced independent Bernoulli random losses and analyzed the impact of the packet error rate on the failure rate of the maneuver, proved that packet loss mainly affect the maneuver from a coordinating point of view [20]. However, these approaches are not perfect, because the time-varying delay and packet loss rate are caused by rapid changes in network topology, the condition of communication channels, and the mobility of vehicles in platoon. Therefore, it is necessary to investigate the communication process of platoon and analyze its performance. Our work concentrates on the performance analysis of the IEEE 802.11p broadcast which is used to convey control messages on the CCH for intra-vehicle communication under a VANETs environment. The contributions of our work can be described as follows:  
1.