# Slicing on the Road: Enabling the Automotive Vertical through 5G Network Softwarization
## 6 Proof-of-Concept Experimental Evaluation
### Reference Scenario 1: Slice Capacity Aggregation  
Figure 5 illustrates a vehicle moving at constant speed (36 km/h) on a straight road (600 m long) connected to a V2X slice for cooperative driving services. The vehicle relies on V2V and V2N connectivity provided by its Telco operator (MNO A). The V2N link is used to connect to the V2X AS, wherever placed as previously discussed.  
Initially (\(t=0\)), the vehicle is connected to an eNodeB (A1) of its home operator (MNO A) and the V2X AS is hosted by the corresponding MEC server. During the journey, the vehicle loses the coverage of its operator and it roams (e.g., due to a territorial crossing or a blind spot coverage) to another operator (MNO B) by attaching to eNodeB B1.  
We assumed that other slices are currently supported by MNO B (e.g., for mMTC services which heavily load the access network), and the penetration of cooperative connected vehicles in the MNO B's subscribers basis is low, thus a V2X slice satisfying the user requirements is not available.  
Figure 5: PoC reference scenario of slice capacity aggregation implemented in Mininet-WiFi.  
Two cases can be explored at this point:  
* Case 1 (No slicing federation). MNO B accepts the roaming vehicle and allocates a _default_ V2X slice with the available resources, without disrupting the customer active slices but at the expenses of poorer quality. Since MNO B does not host the V2X AS in its MEC facilities, the vehicle is forced to connect to a remote V2X AS, and, hence, experiences larger latencies. In particular, the SDN controller handling the subscription information of the roaming vehicle (as tracked by the RADIUS server) applies the corresponding datapath (OF metering) rules to limit the bandwidth to 5 Mbps on the path from the vehicle to remote V2X AS (i.e., across B1 and the core network).
* Case 2 (Slicing federation). MNO B does its best to guarantee to the roaming vehicle the same quality as in the home network by means of a federated network slicing approach including MNO C resources. Multi-connectivity access over the (R)AN is activated to boost the throughput performance by bonding the radio interfaces as triggered by the SDN Controller configuring the corresponding flow tables, when the overlapping coverage areas of B1 and C1 are detected.  
In both cases, after some time, the vehicle returns to its home MNO through A2. Note that, for the sake of implementation simplicity, a single cell in the network of MNO B is traversed by the vehicle before switching back to the coverage of MNO A.  
The benefits of slicing federation in terms of the impact on measured latency and throughput of the vehicle when accessing the V2X AS through different MNOs can be seen in Figure 5(a),b, which presents the results of 10 experiment runs. When slicing federation is in place (Case 2), the vehicle experiences better performance. Federation enables multi-RATs access so that the vehicle also connects to C1 and benefits from higher throughput. Sudden increasing throughput demands by the vehicle may raise to exchange data at an intersection, where the visibility may be obstructed and the MEC server may be particularly helpful to build the 3D-surrounding maps. The measured latency is significantly lower (compared to the non-federation Case 1) and the service disruption is reduced when the vehicle is served through the federated MNO C, also thanks to the pro-active migration of the V2X AS at the edge of MNO C. he viability of the pro-active migration of applications among edge nodes is investigated in [45; 46].  
Figure 5(c) shows the effectiveness of OpenFlow 1.3 metering rules in B1 to drop packets identified as MNO A customer exceeding 5 Mbps in Case 1.