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A convergent gateway to realize full fixed/mobile convergence

Mobile networks are today greatly centralized with a few gateways connecting mobile users to the Internet and referred to as Packet Gateways (PGW). Still today, cellular traffic is much smaller than fixed traffic, with peaks in mobile networks several orders of magnitude smaller than those in fixed networks, and a few PGW are sufficient to handle the whole of cellular traffic. But in the near future it is seems very likely that wireless traffic will steadily grow and reach much higher peak rates because of the massive usage by users of bandwidth greedy services available through the network (notably Over The Top services). Users furthermore tend to massively connect to the Internet via mobile devices (tablets, smartphones, dongles, etc.) through Wi-Fi or cellular (3G/4G) interfaces. They even do not want to care about the type of access and wish to seamlessly use their services wherever they are and whatever the radio access technology be.

While cellular data mobile traffic currently traverses the mobile backhaul and the evolved packet core network (specified in 3GPP standards), Wi-Fi access points (notably those in the home gateway) are connected to the Internet through the fixed access network (specified by the Broadband Forum). However, fixed and cellular networks have today completely distinct architectures, business models (flat rate vs. capped offers) and authentication procedures. This implies that it is currently still difficult to switch from access technology to another without breaking user’s sessions. This is all the more unfortunate as network operators are massively deploying cellular networks based on macro, small and femto cells as well as carrier and private Wi-Fi access points to provide users with an ambient connectivity.

To remedy this problem, it is useful to introduce a new functional element, referred to as Convergent Gateway (see keynote and video) which ensures full wired and wireless Wi-Fi/cellular distributed convergence and collects both types of traffic in line with desired ambient connectivity. This element developed in collaboration with b<>com, the technological research institure located in Rennes, Brest and Lannion,  is based on open source software in the form of modules instantiable in virtualized machines. The Convergent Gateway neatly splits the control and data end points, thus going beyond the state of the art of splitting paths for the control and data planes, in order to transport as soon as possible data packets through the IP collect network and avoid bottlenecks in the network. The data plane component of the Convergent Gateway, which can be collocated with next generation PoP functions, implements tunnel termination (GTP-U, PPP, GRE, VLAN etc.) and packet handling functions (dropping, marking, prioritization, etc.). The control plane functions perform authentication, authorization, mobility management, address allocation, Wi-Fi control, etc. and can be hosted in the cloud and or in the fog (largely distributed cloud), possibly in servers available in next generation PoPs.

Since the Convergent Gateway is a set of open source software modules, such a gateway can be instantiated on the fly on virtualized machines by a network operating system, also known as GlobalOS (see the GlobalOS article). The Convergent Gateway thus becomes a structural component of the GlobalOS to ensure universal access to the network. A next step in the development of both the Convergent Gateway and the GlobalOS is the possibility to instantiate such a gateway in devices (boxes, terminals, etc.), which are today outside the network but which could be used in the future to extend the network in order to build domains, based on device-to-device and device-to-infrastructure communications.

A first prototype of a Convergent Gateway developed by b<>com will be available mid 2016 and will integrate open source software, notably the virtual Evolved Packet Core released by the Open Air Interface consortium and openCapWap as Wi-Fi controller. This prototype has been developed by using the research work performed by Orange Labs Research on the evolution of network control planes, notably for 5G, which is a major issue for Orange Labs Research.

This article has been written in collaboration  Xavier Priem (b<>com).

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