# Handover Management in 5G Vehicular Networks
## 3 Preliminaries
### Network Selection  
During the network selection (Figure 8), the vehicle sends a \(1.M1H\_Get\_Information\_Request\) to the MIIS. This message embeds information about the services and the remaining energy of the vehicle. In the case of predictive HO, the message is transmitted by the current network of the vehicle. However, in the case of reactive HO, the vehicle chooses the network alternative with the higher SINR to transmit the message, since the connection with the current network has been lost. Subsequently, the velocity and network monitoring process considers the mobility state of each vehicle to create a subset \(A^{\prime}\subset A\) of the available networks. Specifically, if the vehicle's velocity has been characterized as Normal, then all the available networks are considered as alternatives, including both Macrocells and Femtocells in the \(A^{\prime}\) subset. On the other hand, if the vehicle's velocity has been characterized as Medium, then some Femtocells are skipped along the vehicle's trajectory and are not included in \(A^{\prime}\). In particular, the Femtocell \(i\) is considered as an alternative if the estimated residence time of the vehicle \(u\) (\(t_{u,i}^{residence}\)) is greater than or equal to the average residence time of the vehicle considering all the available Femtocells in its current location. It has to be noted that the \(t_{u,i}^{residence}\) parameter of vehicle \(u\) for the \(i\)th cell is estimated using Formula (40) [46], where \(r_{f}\) is the cell radius and \(v_{u}\) is the vehicle velocity obtained by Formula (41) [47]. The \(\lambda_{u}\) parameter represents the cell's density in the location of the vehicle, as it is obtained by the Software-Defined Networking (SDN) controller. Finally, if vehicle's velocity has been characterized as High, then only the available Macrocells are included in the \(A^{\prime}\) as alternatives.  
\[t_{u,i}^{residence}=\frac{\pi\cdot r_{i}}{2\cdot v_{u}} \tag{40}\]  
\[v_{u}=\frac{\pi\cdot N_{CRu}}{4\cdot T_{CRmax}\cdot\sqrt{\lambda_{u}}} \tag{41}\]  
Following this, the availability of the resources offered from each network of the subset \(A^{\prime}\) is considered, so that a subset \(A^{\prime\prime}\subset A^{\prime}\) is created. Specifically, the MIIS checks the availability of the resources offered from each network alternative by exchanging \(2.M1H\_N2N\_HO\_Query\_Resource\_Request\) and \(3.M1H\_N2N\_HO\_Query\_Resource\_Response\) messages. Thereafter, networks included in the subset A\" are ranked using the DFT-ACW algorithm. The ranking is performed considering both network characteristics (throughput, latency, jitter, packet loss, and energy consumption) and the operator's policy criteria (service reliability, security, and monetary cost) that each network offers for the services of the vehicle. Since the energy consumption parameter is considered during the ranking process, energy-intensive networks such as LTE-A Pro FD-MIMO, which operates with multiple antennas, obtain a low score for vehicles with low remaining energy of the user equipment. Furthermore, since the decision is made considering the vehicle's velocity,  
Figure 7: The S values range as obtained using the FIS.  
as well as QoS and policy-related parameters, the ping-pong HO effect is eliminated. Following this, the network that obtains the higher score is selected, while the vehicle is informed about the target access network through a \(4.MIH\_Get\_Information\_Response\) message.