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[EN] Vehicular ad hoc network (VANET) is an emerging and promising technology, which allows vehicles while moving on the road to communicate and share resources. These resources are aimed at improving traffic safety and providing comfort to drivers and passengers. The resources use applications that have to meet high reliability and delay constraints. However, to implement these applications, VANET relies on medium access control (MAC) protocol. Many approaches have been proposed in the literature using time division multiple access (TDMA) scheme to enhance the efficiency of MAC protocol. Nevertheless, this technique has encountered some challenges including access and merging collisions due to inefficient time slot allocation strategy and hidden terminal problem. Despite several attempts to study this class of protocol, issues such as channel access and time slot scheduling strategy have not been given much attention. In this paper, we have relatively examined the most prominent TDMA MAC protocols which were proposed in the literature from 2010 to 2018. These protocols were classified based on scheduling strategy and the technique adopted. Also, we have comparatively analyzed them based on different parameters and performance metrics used. Finally, some open issues are presented for future deployment.

Rapid change in network topology due to mobility is one of the challenges in Mobile Ad hoc Network (MANET) routing, which poses a number of problems. The protocols must be able to adapt to the unpredictable dynamic topology. This study investigates the conventional DSR and DSDV routing protocol with the aim of improving DSR routing protocol using TTL-based scheme. The preliminary investigation showed that DSDV outperformed DSR most especially when the nodes moved at high speed, which was due to inability of the DSR to repair a broken link locally and lack of any mechanism to control the freshness of routes when there are multiple options. A new mechanism, DSR_TTL was proposed in order to improve the performance of conventional DSR. The analysis was based on the small network size with constant and variable speed. The results of the study indicated that a medium number of TTL revealed a high performance for the metrics used for the study. Therefore, with all default parameters unchanged as in conventional DSR protocol, the new TTL value was set for the proposed protocol. The results have shown that the proposed protocol generally improved the network throughput and reduced the total overhead.

The paper presents a model of operation rescue and group vehicle approach to support green vehicle communication for urban operation rescue. Using vehicular technology could benefit operation rescue vehicles by enabling each vehicle spreads the information related before arriving at the incident place. In an effort to understand the operation rescue activities, studies on the case study are briefly discussed. Green vehicle communications requirements are presented to show the significance of using vehicular technology. Experiments using NS-2 to measure the average delay time per trip and average throughput for three different scenarios are presented.