The mobility management architecture in current generation LTE networks results in high signaling traffic. In this chapter, we present an Evolved Packet Core (EPC) architecture based on Software Defined Networking (SDN) concepts. The proposed EPC architecture centralizes the control plane functionality of the EPC thereby eliminating the use of mobility management protocols and reducing mobility related signaling overheads. The architecture utilizes the global network knowledge with SDN for mobility management. The proposed architecture has been implemented in the ns-3 simulator. A prototype testbed has also been implemented using the Floodlight SDN controller, a Software Defined Radio platform and relevant software.
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It is expected that the number of global mobile 4G connections based on LTE networks will grow from approximately 203 million in 2013 to 1.5 billion by 2018 at a CAGR of 50 percent (Cisco Systems, 2014). It is also expected that more than half of all this traffic will be offloaded from mobile-connected devices (almost 17 exabytes) to the fixed network using WiFi and femtocells (Cisco Systems, 2014). Thus, the network’s data and control planes should be suitably designed. In particular, signaling cost incurred for session establishment and for handover from one network to another (e.g. LTE to WiFi) should be reduced significantly. The objective of this chapter is to design a scalable architecture that incorporates efficient control signaling mechanisms to help meet the future network’s requirements. The proposed architecture is based on software defined networking (SDN) concepts.
The core components of the 3GPP–EPC architecture are the Mobility Management Entity (MME), Serving Gateway (SGW) and Packet Gateway (PGW) (Savic, 2011). The SGW is used for intra-mobility purposes (within the same LTE network) and the PGW for connectivity to the Internet. In 3GPP–EPC, each connection is an EPS bearer that consists of a data radio bearer (DRB), GPRS Tunneling Protocol (GTP) and a Proxy Mobile IPv6 (PMIPv6) tunnel (Oliva, Bernardos, Calderon, Melia, & Zuniga, 2011). The PMIPv6 protocol is standardized by IETF to provide network-based IP mobility support (Oliva, et al., 2011). PMIPv6 is used in 3GPP–EPC to integrate 3GPP with non–3GPP access networks. The GTP protocol is used in 3GPP–EPC to provide intra-network IP mobility. For each EPS Bearer, the maintenance of these tunnels leads to high control plane signaling overheads. Maintenance of these GPRS Tunneling Protocol (GTP) and Proxy Mobile IPv6 (PMIPv6 or PMIP) tunnels are required whenever events such as connection establishment, connection release and handover occur in the network.
An analysis of messaging events in an LTE Evolved Packet Core (EPC, also called 3GPP–EPC in this chapter) showed that main contributors to the signaling overhead are connection establishment/release, handover and tracking area update events (Nowoswiat & MIlliken, 2013). Thus, for next generation networks, an architecture that supports low signaling cost while handling such events (like connection establishment/release, handovers, etc.) is required.
This chapter proposes an EPC architecture that is based on Software Defined Networking (SDN) principles (Open Networking Foundation, 2012), (Kobayashi, 2014). SDN systems operate by separating the data and control planes. It also provides several advantages in terms of network programmability, network virtualization and others. The OpenFlow protocol (Open Networking Foundation, 2014) has emerged as an industry standard for interactions between the SDN controller and the routing/switching hardware elements in the network.