# Seamless Handover Scheme for MEC/SDN-Based Vehicular Networks
## 2 Background and Related Works  
Recently, the VANET has attracted many researchers in the academic and industrial fields [28; 29]. The VANET is one of the main use cases of 5G networks that has been announced, and since the first commercial version of the 5G system was released, the research in the area of VANETs has become more attractive [30; 31]. Many existing works in the literature consider VANETs; however, in this section, we consider only the works that are most relevant to our proposed study in order to highlight the novelty of our work. The handover process is one of the main critical processes in vehicular communication systems, since it should be done in an efficient, seamless way [32]. This is crucial and presents a challenge for designing VANETs, due to the high mobility of vehicles [33; 34]. There are few works that consider the handover process in VANETs or the development of a handover algorithm for VANETs. We considered the recently developed handover schemes for VANETs. In [35], the authors introduced a novel network structure for a VANET based on MEC technology. The proposed structure achieved high system scalability and high latency efficiency. However, the handover mechanism considered was that of a traditional cellular system, essentially the LTE-V handover mechanism. The authors did not consider developing a new handover mechanism for the developed VANET structure. This would affect the overall performance and create conflict, since MEC servers were not considered in the handover process. In our proposed work, the MEC paradigm is deployed in the VANET structure and represents a main part of the suggested handover algorithm. This makes the handover process more seamless and achieves many other benefits, as introduced later, in Section 3. In [36], the authors developed a novel network structure for vehicular communications based on SDN technology. The developed system met the ITS requirements and the specifications that had been announced. The challenge of the handover scheme was addressed by developing a fog-shaped cell that reduced the rate of the handover process among RSUs. The work considered the throughput and latency as the key performance indicators. The developed system achieved a higher latency and throughput than other existing systems. In [37], the authors developed an SDN-based handover scheme for vehicular networks. SDN was used to maintain the transport layer communication during the handover process. The VANET deployed the IEEE 802.11p and enabled V2X communications over an unlicensed spectrum. The simulation results validated the system in terms of throughput. However, our proposed system involves implementing the handover scheme over MEC servers, which achieves less latency. Moreover, the time required to migrate V2X tasks is considered, which reduces the probability of task blocking during the handover process and achieves a higher system availability. In [38], scientists employed mobile edge computing (MEC) and software-defined network (SDN) technologies in the building of the network to modify the overall net work performance under the conditions of high traffic density. They also developed an algorithm of D2D-based clustering to solve the problem of disconnected vehicles in dead zones and offload the network in regions with high traffic. By using the aforementioned technologies, the authors could achieve a performance of up to 74% gains in terms of task-blocking probability. In [22], the authors proposed an advanced handover algorithm by adopting SDN in the building of the network architecture, and they explained the advantages of using SDN in the network control to administer the data transfer in VANETs. Hence, the connection of the transmission layers could be fixed when the handover occurred. This achieved a high-quality improvement based on the vehicle's mobility and link rates. In [39], the authors focused their studies on the latest developments in data-offloading techniques in VANETs.