IEEE Communications Magazine • January 2015142 0163-6804/15/$25.00 © 2015 IEEE
Fabio Giust and Carlos J.
Bernardos are with University Carlos III of
Luca Cominardi is with
University Carlos III of
Madrid and IMDEA Networks Institute.
The research leading to these results has received funding from the European Community’s Seventh Framework
Program FP7/2007-2013 under grant agreement 317941 — project iJOIN.
The European Union and its agencies are not liable or otherwise responsible for the contents of this document; its content reflects the view of its authors only.
In the recent years, Internet data communications have experienced a paradigm shift from the traditional fixed cable access to the wireless and mobile world. The huge success of powerful handheld devices and the deployment of faster heterogeneous radio access technologies, like
IEEE 802.11n and Long Term Evolution (LTE), have led to the familiar concept of being connected anywhere, anytime. Reports such as  show that mobile traffic growth will not decelerate; conversely, it will increase 11-fold from 2013 to the end of 2018.
Mobile operators, together with industry and research communities, are looking at cheap and effective solutions to cope with this tremendous growth. There are two main issues to tackle: • How to provide enough capacity in the access • How to handle all the traffic in the transport network
For the first issue, reducing the size of cells is the most feasible approach that can provide a significant bandwidth increase. Regarding the second issue, current architectures for mobile and cellular networks are highly centralized and hierarchical, forcing user traffic to traverse all the network parts up to the core, where key entities are deployed to function as border IP gateways and mobility anchors. Following this approach, the general packet radio service (GPRS) Tunneling Protocol (GTP)  and
Proxy Mobile IPv6 (PMIPv6)  have been adopted as two possible choices to operate the
Evolved Packet Core (EPC) of 4G networks.
The advantage of the centralized approach resides in its simplicity, because the central anchor can follow user movements by simply rerouting the packets over tunnels created with the access router where the mobile node (MN) is currently connected. However, the mobility anchor represents a single point of failure, poses scalability issues (i.e., it is the cardinal point for the control and data plane for millions of users), and, in general, leads to suboptimal paths between MNs and their communication peers (also known as correspondent nodes, CNs) .
Therefore, future 5G mobile networks are expected to be more flexible, relaxing the constraint of binding user traffic to a central core entity and allowing Internet services to be located closer to the users. Extremely dense wireless deployments shall benefit from such features by reducing the congestion in the operator’s core infrastructure and providing improved service to users. Another defining characteristic of future 5G networks is that the infrastructure is expected to simultaneously serve very different sets of users and applications. For example, 5G networks are foreseen to share resources to cope with both highly demanding video applications of a few mobile users and low-bit-rate traffic from a large bunch of sensors (the so-called
Internet of Things, IoT). Along with these objectives, distributed mobility management (DMM) has recently emerged as a new paradigm to
The ever-increasing demand of mobile Internet traffic is pushing operators to look for solutions to increase the available bandwidth per user and per unit of area. At the same time, they need to reduce the load in the core network at a reasonable cost in their future 5G deployments. Today’s trend points to the deployment of extremely dense networks in order to provide ubiquitous connectivity at high data rates. However, this is hard to couple with the current mobile networks’ architecture, which is heavily centralized, posing difficult challenges when coping with the foreseen explosion of mobile data. Additionally, future 5G networks will exhibit disparate types of services, posing different connectivity requirements. Distributed mobility management is emerging as a valid framework to design future mobile network architectures, taking into account the requirements for large traffic in the core and the rise of extremely dense wireless access networks. In this article, we discuss the adoption of a distributed mobility management approach for mobile networks, and analyze the operation of the main existing solutions proposed so far, including a first practical evaluation based on experiments with real Linux-based prototype implementations.
EXTREMELY DENSE WIRELESS NETWORKS
Fabio Giust, Luca Cominardi, and Carlos J. Bernardos
Distributed Mobility Management for
Future 5G Networks: Overview and
Analysis of Existing Approaches
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IEEE Communications Magazine • January 2015 143 design a flat and flexible mobility architecture, allowing traffic to be broken out locally closer to the edge (i.e., offloading the network core) and exploiting the use of different gateways for traffic with different connectivity and mobility requirements.
In this article, we argue that DMM approaches are suitable candidates for mobility management in future 5G very dense deployments.
Then we explore the DMM solution space by focusing on the main three families of solutions currently proposed: • A protocol derived from a classical IP mobility management approach, PMIPv6 • A mechanism based on software defined
Nnetworking (SDN) • A routing-based solution
We describe in this article the main characteristics of each of these DMM approaches and then conduct a validation and performance assessment of each of them by implementing the three solutions in a real prototype. Finally, we derive some interesting conclusions from the comparison of the obtained results. In this work we focus on the comparison of DMM-only solutions, but readers interested in a centralized vs. distributed study might consider the analysis reported in .