# Handover Management in 5G Vehicular Networks
## 3 Preliminaries
### HO Execution
#### 4.4.1 Proposed Predictive HO Scheme  
In the case of predictive inter-MAG HO execution (Figure 9), the current network initially sends a \(1.MIH\_N2N\_HO\_Commit\_request\) to the selected MAG to reserve the necessary resources for the upcoming handover. Following this, the selected MAG responds with a \(2.MIH\_N2N\_HO\_Commit\_response\) message indicating that the required resources have been reserved. In this case, the current MAG informs the vehicle about the successful resource allocation at the selected network using a \(3.MIH\_Net\_HO\_Commit\_request\) message, while the vehicle acknowledges the reception of the information using a \(4.MIH\_Net\_HO\_Commit\_response\) message. Subsequently, the MAG of the current network sends a \(5.Handover\_Initiate\) message to the MAG of the selected one, which includes the MN Identifier (MN-ID), the Home Network Prefix (HNP), and the MN Logical Link Identifier (MN-LLID). Furthermore, the Proxy (P) and the Buffering (B) flags of the message are set equal to 1 to inform the selected MAG that the buffering of data has been performed at the current MAG. By receiving this message, the MAG of the selected network replies with a \(6.Handover\_Ack\) message, which acknowledges that the aforementioned information has been successfully received, while a bi-directional tunnel is established between the two MAGs. Thereafter, a copy of the buffered packets from the current MAG is transmitted through the tunnel to the selected MAG to be delivered to the vehicle when it connects to the selected network. Subsequently, the new MAG sends a \(7.PBU\) message to the LMA to create a transient record in the binding  
Figure 8: The signaling performed during the network selection. cache. Once the temporal binding is established at the LMA, it sends a \(8.PBA\) message to the MAG of the selected network, and a bi-directional tunnel is established between the two entities. Thus, downlink packets are forwarded from the LMA to the MAG of the selected network where they are buffered to be delivered to the vehicle when it completes its HO to the selected network. Furthermore, the bi-directional tunnel between the current MAG and the LMA remains active until the transient binding becomes permanent. Then, the transient binding introduces a smooth way for performing the handover by gradually changing the current MAG to avoid packet losses and false HOs. Subsequently, the vehicle sends a \(9.MIH\_Link\_up\) message to the selected MAG to enable the communication channel. Furthermore, the vehicle sends a \(10.UNA\) message to the selected network, to complete the establishment of both the Link and Network layers. Thereafter, the MAG of the selected network exchanges the \(11.PBU\) and \(12.PBA\) messages with the LMA to finalize the binding. Finally, the selected network sends a \(13.MIH\_N2N\_Complete\_request\) message to the previous network. By receiving this message, the previous network releases the resources that have been reserved for the vehicle and sends back a \(14.MIH\_N2N\_Complete\_response\) message to finalize the HO execution. Similar to the predictive inter-MAG HO execution, in the case of the predictive intra-MAG HO execution (Figure 10), the current network sends a \(1.MIH\_N2N\_HO\_Commit\_request\) to the selected network to reserve the necessary resources for the upcoming handover. Following this, the selected network responds with a \(2.MIH\_N2N\_HO\_Commit\_response\) message indicating that the required resources have been reserved. In this case, the current network informs the vehicle about the successful resource allocation at the selected network using a \(3.MIH\_Net\_HO\_Commit\_request\) message, while the vehicle acknowledges the reception of the information using a \(4.MIH\_Net\_HO\_Commit\_response\) message. Subsequently, the vehicle sends a \(5.MIH\_Link\_up\) message to the selected network to enable the communication channel. Furthermore, the vehicle sends a \(6.UNA\) message to the selected network, to complete the establishment of both the Link and Network layers.