## 2 Related Work
### Factors Commonly Studied in VANETs  
Most currently available VANET research works rely on simulation. However, we find that most of the experiments made to validate these proposals tend to overlook the most important and representative factors. [PERSON] _et al_. [7] proposed the vehicle-node density parameter to improve the performance of both AODV and OLSR routing protocols under two typical mobile models in VANET. Simulation results showed the performance improvements of routing protocols when increasing the node density around the receiver. In this work, they varied the density of vehicles and the mobility models, while maintaining unaltered other parameters such as the simulation area, the transmission range, the packet size, and the radio propagation model. [PERSON] _et al_. [8] focused on the accuracy of urban propagation models and their impact on vehicular protocol results. They compared the Two Ray model and the Corner model in a city scenario. Moreover, they identified a number of factors that undermine the validity of the Two Ray model, for example, the presence of buildings causing propagation disruption and the heavy weight border effects that incorrectly compensate for the presence of hidden terminals in the networks. In this work, authors varied the transmission range, the map size and the radio propagation model, while maintaining unaltered other parameters such as the density of vehicles, the packet size, _etc_. [PERSON] _et al_. [9] looked at the result of tuning transmission power and its effect on UDP throughput in VANETs. Results showed that the major mitigating factor in VANETs is the number of hops between the source and the destination. They assessed that increasing the transmission range results in decreasing the number of hops between source and destination effectively increasing throughput. Authors also found that the effect of vehicle densities is only important at lower transmission ranges to provide the required connectivity. Regarding warning message dissemination, [PERSON] _et al_. [10] described in detail a vehicular dissemination protocol that allows sharing information such as available parking spaces, accidents or obstacles in the road, _etc_., by using vehicle-to-vehicle communications. In this work, authors varied some factors such as the density of vehicles and the vehicle's speed, while maintaining unaltered other parameters such as the transmission range, the map size, the radio propagation model, the simulated roadmap, _etc_. [PERSON] _et al_. [11] proposed an IEEE-802.11-based multi-hop broadcast protocol to address the issue of warning message dissemination in VANETs. The protocol adopts a binary-partition-based approach to repetitively divide the area inside the transmission range to obtain the furthest possible segment. In this work, authors varied some factors such as the density of vehicles and the vehicles' speed, while maintaining unaltered other parameters such as the periodicity of messages, the radio propagation model, the transmission range, _etc_. The effect of obstacles in warning message dissemination has also been addressed by some works. [PERSON] _et al_. [12] presented an approach where a message propagation function encodes information about target areas and preferred routes for the message dissemination. Selecting different functions produces different routing protocols accounting for connected and disconnected situations between vehicles. These protocols show a remarkable performance in simple grid-like scenarios with low and high density of vehicles, but real maps are not used in their simulations. [PERSON] _et al_. [13] proposed the UV-CAST (Urban Vehicular broadCAST) protocol, which allows reducing the broadcast storm problem while solving disconnected network problems in urban VANETs. However, the density of vehicles studied is relatively low, and the authors did not study its performance when there are more than 50 vehicles per km\({}^{2}\).