A survey on how to solve a decentralized congestion control problem for periodic beacon broadcast in vehicular safety communications

For decades, vehicular industries have made an investment in developing cooperative vehicular systems to satisfy the current and future needs for reducing car accidents and increasing traffic safety and efficiency on the road. To satisfy these requirements, vehicular ad hoc networks (VANETs) based on wireless communications have been emerging as one of the promising solutions in recent years. Several research efforts have been conducted for various applications in VANETs and especially cooperative collision warning (CCW) using vehicular safety communication has been getting the spotlight because this is one of the most important and critical applications in VANETs. To realize CCW, however, the existing technical challenges, such as congestion control of periodic beacon broadcast and reliable dissemination of emergency messages in congested situation, should be solved. In this paper, we present the existing congestion control techniques for CCW in decentralized vehicular environments and point out their limitations and technical challenges. The question about how to solve these problems is also discussed in this paper.