## 3 Network Slicing in 5G Networks
### Energy Demand of NSs Provided as Services of Mobile Virtual Network Operators  
In 5G mobile networks, a highly interesting use case of NS implementation is to offer NS as a service. By assigning a network slice as a service, organizations that do not own the infrastructure at all, or do not fully possess the mobile network infrastructure, can operate as mobile operators, and they are referred to as mobile virtual network operators (MVNOs). As illustrated in Figure 5, there are various versions of network slices used as a service, depending on the resources required by the MNO. They are generally defined as **branded reseller**, **light**, **medium**, and **full MVNOs**. However, the level of MNO resource engagementfor the realization of MVNO services will impact the overall energy-consumption footprint of the NS that is realized as an MVNO. Consequently, the MNVO will have a different influence on the energy consumption policies of the corresponding NSs. The **branded reseller** MVNO type is typically the most straightforward for an MNO to accept, as the MNO retains control over the majority of processes (Figure 5). In the case of a brand reseller, the MVNO NS lacks core network elements and is primarily responsible for maintaining contact and relationships with customers through service marketing and tariffing. The advantage of this approach is that it offers a quick service time to market and low startup costs to the MVNO, since there is no need for investment in the MVNO infrastructure as the MNO handles most of these aspects. The disadvantage of this approach to MVNO is the lack of control and subscriber identity modules (SIMs); additionally, the network infrastructure is owned by the MNO, which also sets tariffs for the services offered to the MVNO users. For the control and management of the network energy consumption policy, MNO takes full responsibility, and the energy costs are included in the pricing of the NS service for the MVNO. Thus, light MVNO is not a direct energy consumer, and all network energy consumption is related to the MNO. A **light MVNO** operates using its own brand and is in charge of customer care and billing for the offered service(s), as well as having limited access to network routing (Figure 5). The MVNO introduces an NS service, contains a customer database, and promotes and distributes services which enable the MVNO to differentiate itself from competitors. One of the advantages of light MVNO in comparison with the brand reseller MVNO concept is that it owns branded SIM cards and can independently set tariff packages. However, the realization of the NS service offering incurs a share of the operational expenses (OPEX) and capital expenses (CAPEX) with the MNO. Despite knowing customers' identities and SIMs, the MVNO does not possess the International Mobile Subscriber Identity (IMSI) of the users, which are owned by the MNO. The light MVNO has an impact on the control and management of the energy consumption of the small portion of those network elements it possesses, while the control and management of the energy consumption of most network elements leased from the MNO are in charge of the MNO. Thus, the NS, realized as the light MVNO, is an energy consumer; however, its energy consumption is significantly smaller than NS part of the network energy consumption of the whole MNO. A **medium MVNO** operates as an NS under its own brand with its own proprietary SIM cards and has the potential to obtain its own mobile network code (Figure 5). While not fully independent from the MNO (e.g., MVNO interconnection and IMSI are controlled by the MNO), the medium MVNO has the ability to introduce its own services that enhance the sales of offered services. The advantage of medium MVNO compared to light MVNO lies  
Figure 5: MVNO and MNO infrastructure and services [29]. in its independence from the MNO in creating and offering its own applications and value-added services to users, along with corresponding tariff packages and retail prices.