# Efficient Dissemination of Safety Messages in Vehicle Ad Hoc Network Environments
## 2 Related Work  
Broadcast-based message dissemination generates many duplicate messages, causing packet collisions and transmission delays. Recently, researchers have studied several message dissemination schemes to address these issues.  
The reliable emergency message dissemination (REMD) scheme has been proposed [12], which ensures message dissemination reliability by performing the optimal number of broadcasts. REMD measures the quality of the vehicle's wireless communication reception and uses this to calculate the optimal number of message repetitions. It then selects forwarders based on this information. In REMD, each hop's forwarder performs cooperative communication to improve the network's reliability.  
Position-based emergency message dissemination (PBE), a scheme that disseminates location-based emergency messages by forming clusters, has also been proposed [13]. The proposed environment supports urban areas with high traffic density and bidirectional traffic with multiple lanes. Vehicles form clusters based on their speed and direction of movement. Each cluster consists of one cluster head (CH) and one or more cluster members (CMs). In PBE, the probability of emergency message dissemination between the vehicles is modeled using the Nakagami-m probability distribution.  
A centralized scheduling algorithm within the RSU coverage area and a temporary message dissemination strategy outside the coverage area have also been proposed [14]. This scheme considers the highly dynamic network topology due to the high mobility of vehicles and the limited infrastructure-to-vehicle (I2V) bandwidth. The scheme analyzes how the dynamic network topology and limited bandwidth impact the number of message items vehicles can retrieve.  
Enhanced cooperative load balancing (ECLB) has been proposed [15]. ECLB considers a multi-RSU environment. They emphasized the necessity of RSU scheduling to disseminate messages in a VANET. In addition, they proposed the RSU scheduling scheme using cooperation of multi-RSU. It was shown that when considering the remaining delay tolerance of submitted requests and the knowledge of fixed road layout, the performance of the cooperative load balancing system can be further improved significantly.  
Since the REMD scheme for urban vehicle networks [12] uses a probability-based technique with Nakagami-m distribution, this may cause unacceptable communication delay errors in actual road environments. Location-based emergency message dissemination (PBE) for the Internet of Vehicles [13] does not consider the frequent cluster departures of vehicles due to the various directions of vehicles. Therefore, in PBE, the more frequent the CH's departure from the cluster, the more score comparisons among CMs occur to select the next CH. The message exchanges required for this process result in substantial safety message packet loss. This scheme also does not consider various safety message types. Finally, this scheme does not consider the RSU environment. RSU support-adaptive scheduling for intervehicle message sharing in bidirectional road scenarios [14; 15] focuses on RSUs, lacks detailed operations for message dissemination in environments without RSUs, and does not consider the RSU load. For efficient message distribution, a distribution scheme considering both V2V and V2I environments is required.