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4G/3G/WiFi

Talking Next-Gen Core Networks

I recently attended the Next-Generation Core Network Summit in London – a primarily mobile-focused event, but with a dose of fixed-line content for good measure.

Over the course of a day and half, it would be hard to identify any one particular theme that emerged, although perhaps the broad topic of quality of service (QoS) and the operational impact of all-IP in mobile data networks came closest. So in lieu of a thematic review, here's a summary of some key points made by various operator and vendor speakers:

Matt Stagg, Senior Manager of Network Strategy at Everything Everywhere. Stagg's primary point was that mobile operator network strategies are now far more device-led than ever before. Adapting to and anticipating the impact of new devices and related applications on the network is therefore critical. Stagg also highlighted the challenge of organizational change when transitioning a network to Evolved Packet Service, as the lines between the well-defined RAN, circuit-switch, packet-switch and transport domains in the classic 3GPP architecture start to blur. "The big challenge is the integration of EPC with the existing PS core," he said. On voice over LTE (VoLTE), Stagg noted that IMS is making reasonable progress, even on the device side. He thinks IMS will probably require a separate "walled-garden APN" for reasons of policy, QoS and IPv6 addressing.

Dirk Kopplin, Senior Marketing Manager at Huawei. Kopplin discussed end-to-end QoS in mobile networks. He noted the complications that arise from the fact that the various QoS domains – Layer 2 (Ethernet, MPLS), Layer 3 (DiffServ) and 3GPP (EPS bearers) – don't overlap perfectly. Nevertheless, he thought a clever vendor and operator could eventually figure it out. He also highlighted a 3GPP initiative to present policy information to third parties over an extended Rx interface – for example, so that a content provider could serve up the right sort of video file for the subscriber's device type, entitlements and network conditions.

Ioannis Vassilopoulos, Head of IP Network Services at OTE. Talking primarily from a fixed-line perspective, Vassilopoulos gave QoS short shrift in terms of its commercial usefulness, at least in the core. "Everyone is using over-provisioning," he said. "Variable delay in normal conditions is unlikely to be perceivable by the user of a voice service. ... Even in a network with 90 percent load, QoS is not needed."

Achiles Petras, Head of Broadband QoS at BT Wholesale. In what could be described as a speculative pitch, Petras discussed the idea of "flow state aware" network equipment that would sit in front of a mobile operator's own equipment and help ensure QoS to mobile broadband users. He said BT had learned a lot about how to ensure consistent end-user data rates through statistical analysis of its DSL lines, and he thought this insight would be applicable in the mobile broadband context. The implication was that BT is thinking about making this "flow state aware" functionality an option in its wholesale transport offers as it seeks to climb the value chain.

Matt McCann, CTO Office at Tekelec. McCann stayed resolutely on corporate message in discussing the dissemination of the Diameter protocol in 3GPP networks. The presentation turned out to be remarkably persuasive. Essentially, the increase in Diameter signaling as more EPC and IMS elements are added to the network creates new and unique operational challenges. "There's not always a coordinated approach to signaling network planning," he noted with some understatement. To address this, McCann made a strong case for the use of Diameter routing agents.

Dietmar Kohnenmergen, Master Expert of System Architecture Network at E-Plus Mobilfunk. Kohnenmergen gave a revealing presentation about the real-world mechanics of transitioning supplementary services from a circuit-switch (SS7/INAP) to IMS/SIP environment. In short, it's much harder than it looks on the architecture diagram, and translating from INAP to SIP will inevitably involve loss of service functionality. He cited a Nokia Siemens study that found about 22 percent of the typical supplementary service use cases need substantial additional work, and that 4 percent remain unsolved. Discussing circuit-switch fallback for VoLTE, he highlighted the potential for misalignment between 2G/3G local areas to LTE traffic areas, and the need to map paging from one to the other if the recipient of an incoming call is to be located and connected in a timely manner.

Adrian Dodd, Senior Director of Managed Services at the GSMA. Dodd talked about progress in setting up a global ENUM registry for VoLTE and other IMS users. So far, the global Tier 0 registries (i.e., the GSMA's "Path Finder" root directory) have been established at IPX peering points, and there's a plan in place to push out regional and national registries over time. ENUM is basically "DNS for phone numbers," so it is expected to be important as operators transition more users from circuit-switch to IMS.

Xiaodong Zhu, West European CTO Marketing at ZTE. Zhu elaborated on ZTE's new mobile core platform, the Integrated Serving Gateway, and the concept of "multiple access binding" – which is where a subscriber is assigned a single user context, regardless of whether s/he is on Wi-Fi, 3G or LTE access. Zhu also said ZTE is restarting discussion with European mobile operators on the use of dual-radio devices as a practical way to address the challenges with VoLTE and the limitations of circuit-switch fallback. Dual-radio devices work well in China and the U.S., he argues, so why not Europe?

Apologies to Mohsen Asadi, VP Business Development at Norconsultant Telematics, and Roberto Minerva, Manager of Long Term Research at Telecom Italia. Both made interesting contributions, but unfortunately my notes are not good enough to accurately immortalize their comments on the Internet.

— Gabriel Brown, Senior Analyst, Heavy Reading

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