A Review on Congestion Control in Vehicular Ad Hoc Network at MAC Layer

Vehicular ad-hoc network (VANET) has been designed to improve traffic safety applications by enabling vehicle-to-vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communication. In VANET, each and every vehicle exchanges the information among them, therefore, a high density of vehicles lead to the problem of congestion. In this context, Medium Access Control (MAC) protocols have been designed to improve the real-time communication between vehicles and roadside components with minimal transmission collision. Due to the VANET characteristics, maintaining communication at the MAC layer are the key challenges in collision control scheme. Therefore, it results in end-to-end delay and packet loss during communication. Towards the solution of these critical challenges, Decentralized Congestion control (DCC) mechanism has been innovated by the European Telecommunication Standard Institute (ETSI). This paper describes the various key challenges involved in congestion control. Also, the available solutions are described in details along with their limitations. This paper focuses on controlling of the channel load measured by DCC mechanism using different transmission parameters such as data transmission, rate transmission, power transmission and sensitive transmission.