## 4 Proposed Architectural Approach
### Slice Manager  
The slice manager is responsible for the provisioning of E2E slices in the compute, network, and access network domains. In this respect, it allows several tenants to manage the required resources and to deploy services for different verticals within the slices. To accomplish its role, it monitors the performance of the slice instances and triggers slice reconfiguration actions, possibly taking into account recommendations and alerts provided by the component responsible for the analysis of the system management data. The slice manager is located at the MOA layer, as shown in Figure 4, which depicts the high-level view of this component. Within this layer, the main goal of the slice manager is the creation and management of network slice instances. Such instances are composed of three chunks of resources, namely compute, networking, and radio, as shown in Figure 4.  
Moreover, the slice manager is responsible for the resource partitioning of the slices at three levels, as defined by the Next Generation Mobile Networks (NGMN) Alliance [38]: infrastructure, network slice, and vertical service. To this end, the slice manager interacts with a selected set of components at the MOA layer, as described below.  
At the infrastructure level, based on the received slices requirements, the radio and computing virtualization infrastructure is created and activated through the interaction with the VIM and the non-realtime RAN intelligent controller (non-RT RIC). This operation reserves the resource chunks and associates them under a specific E2E slice ID. At network slice level, the network services required for the communication establishment of the infrastructure are instantiated. In this phase, the CN is activated, and the small cells and Wi-Fi access points start radiating. Moreover, the slice is fully activated by enabling the E2E connectivity along all respective elements. At this moment, the UEs have full interconnectivity. Finally, the vertical service level is optional and allows third-party services to be deployed in the slice through the NFV orchestrator and the VNFM manager. In this specific case, the slice manager offloads the VNFs deployment, monitoring, scaling, and migration operations on the slices to the orchestrator.  
To support cognitive functionalities, the slice manager also includes a native AI component located at the MOA layer. The main goal of this module is to analyze the information from the network data analytics function (NWDAF) included in the system. NWDAF incorporates the proper functionalities to record and offer periodic information  
Figure 4: High-level view of the network slicing system.  
on the status of the infrastructure, the RAN and the CN on a per-slice basis and provide concrete information on the status of the slice resources. The AI extension exploits the NWDAF-gathered data to predict possible scarcities in the resources of the slices in a specific time frame that could prevent the deployment of new services in the slice, or even to put at risk the performance of the running ones. As a result, this component provides valuable information to the slice manager in advance, raising an alarm in the system before reaching a problematic point to prevent any unwanted issue in the slice. The integration of this simple AI extension within the 5G network management platform will pave the way for further enhancements, such as the prediction of events to preempt mitigation measures, dynamic spectrum sharing, etc.