# A Next-Generation Core Network Architecture for Mobile Networks
## 1 Introduction  
Over the years, the cellular network has evolved from providing basic wireless and mobile phone service to a complex system providing not only phone service but also Internet connectivity and interworking with other technologies (i.e., WiFi)--all of this while guaranteeing a seamless user experience. We can identify two parts in a cellular network: the access network and the core network. Over time, the performance of the air interface, included in the _access network_, has increased drastically, providing high throughput and low latency. This helped keeping up with consumers' expectations in terms of \"raw speed\". Changes in the core network, on the other hand, have been much slower and incremental. Furthermore, its complexity drastically increased due to the business necessity of guaranteeing support of older technologies such as 2G (i.e., GSM) and 2.5G (GPRS). Because of this, today's core network architecture resembles what we show in Figure 1: the union of multiple core networks from different technologies (i.e., 2G, 3G and LTE). The overall architecture has not significantly changed over the years. In LTE, for example, signaling and data planes have been decoupled from one another, but the overall architecture has remained unchanged:a monolithic architecture with a limited number of databases, servers and gateways that serve all User Equipment (UE). Recently, with the introduction of Software-Defined Networking (SDN) and Network Function Virtualization (NFV), many proposals in both academia and industry suggest to move from a hardware-centric architecture to a software-centric architecture. In particular, this would be achieved by deploying generic hardware used to run Virtual Machines (VMs) implementing, in software, different functions of the core network. We show an example of a 4G LTE virtualized core network in Figure 2. In such a network, it is possible to run single and multiple instances of core network elements as deemed necessary by the congestion state of the network at any given time. Such an approach is a significant step forward in terms of innovation in the core network, making the whole network more cost-effective with additional flexibility and control over the resources spent at any given time. However, it does not represent a paradigm shift in the core network architecture, but it continues mimicking, in software, the thirty-year-old architecture discussed earlier. As we have preliminarily shown in [1], by leveraging the flexibility of SDN and NFV, one can propose a different virtualized architecture of the core network. In this architecture, each UE gets its own \"private\" virtual copy of the Enhanced Packet Core (EPC) which we call Virtual Core Network (VCN). In particular, as we show in Figure 3, the proposed core network is a P2P network of VMs. Each VM functions as either a SuperNode (SN) or a VCN. By leveraging NFV, SNs and VCNs implement all the typical functions of an EPC (e.g., Mobility Management Entity (MME), Serving Gateway (S-GW), PDN Gateway (P-GW), Home Subscriber Server (HSS)). In particular, a VCN serves a single UE and typically has a short lifetime, while an SN serving a group of UEs is responsible for assigning VCNs to UEs and has a very long lifetime. In this paper, we present and discuss the VCN architecture shown in Figure 3. This new architecture presents many challenges, but, at the same time, has many significant advantages over the  
Figure 1: A typical cellular network architecture. Figure 2: VM-based LTE cellular network architecture with multiple virtualized MMEs and HSSs. current architecture. Thanks to its highly distributed and personalized nature, the new architecture can, for example, disable cellular botnets from performing Distributed Denial of Service (DDoS) attacks. In addition, it allows the implementation of per-UE custom security and services.