The move to 5G is a long-term transition, not the flip of a switch. Much like 2G networks still exist alongside 3G and 4G networks, Long Term Evolution is expected to be just that: long term.
“5G will not replace LTE,” Rysavy Research concluded in an August report for 5G Americas (pdf). “In most deployments, the two technologies will be tightly integrated and co-exist through at least the late-2020s. Many of the capabilities that will make 5G so effective are appearing in advanced forms of LTE. As Mike Murphy, CTO of North America for Nokia, puts it, there is a general theme that “a main idea starts in 4G and is institutionalized in 5G.”
Those “main ideas” generally fall into three categories:
Radio Access Network technologies including carrier aggregation and higher-order/massive MIMO. What started with two-component-carrier CA, with 20 MHz channels, is evolving to three, four and five component carriers in LTE. In 5G, the channel widths become dramatically wider but the general idea remains the same. Gigabit LTE is often being achieved with the integration of unlicensed frequencies. Likewise, relatively simply 2×2, 4×4 and 8×8 MIMO in LTE scales up in 5G to massive MIMO implementations. MIMO represents a 50% to 5x increase in network capacity, depending on whether it is deployed in an FDD or TDD context, according to Paul Challoner of Ericsson, speaking at the recent Competitive Carriers Association conference.
A focus on a software-centric, automated, virtualized network. The virtualization of the network is well underway, with or without 5G. But the flexibility and automation of 5G essentially assumes a software-defined, virtualized network, said Nokia’s Murphy. Automation is going to be key, he added, but it has many components: SON, SDN, orchestration and analytics, as well as mobile edge computing, all of which are being implemented in LTE. “Network slicing” in 5G aims to fulfill the promise that granular “quality of assurance” was supposed to achieve in LTE, but which has ended up being largely limited to prioritizing voice over LTE traffic. Viavi Solutions CTO Sameh Yamany said that Viavi considers some internet of things deployments to be contributing toward architectural changes via virtualization – some IoT deployments are being done with virtualized Evolved Packet Core elements in order to segment the traffic, which is essentially a network slice, he pointed out. Kalyan Sundhar, VP of mobility, virtualization and applications at Keysight’s Ixia Solutions Group, said that while the move to virtualized networks and MEC is well underway, the devil is in the details of deployment. For example, he said — how easy is it to deploy virtual nodes, with multiple versions? What are the fault tolerances? What happens when one goes down? Those are some of the things operators are figuring out now, as they virtualize portions of their networks.
Access architecture changes, including fiber proliferation and mobile edge computing. As Viavi has talked to its largest operator customers, Yamany said, they are thinking about network splits and architectures for 5G within an LTE Advanced Pro context.
“They understand that 5G or no 5G, how you want to do the densification of some areas of the network to include virtualization as well as maximizing bandwidth at the same time – you’re going to have to do the split anyhow. 5G or no 5G, the split is happening,” Yamany said. “I can tell you that right now, most of the focus, if you talk about the physical network design, is in time synchronization,” Yamany added. When functions are being moved from where they have typically resided in the network, to another place, whether there is aggregation or disaggregation involved, the synchronization is key to proper functionality. “If you don’t do it right, it will destroy the latency of your application,” he said. Forward-looking operators have already started assessing the qualifications of their circuits to see if they can support 5G-level latency. He estimated that the industry is “about 50% there” and that by the end of 2018, he expects to see “more and more qualified networks for 5G.” Right now, he added, the focus is not necessarily on reaching 1 millisecond latencies, but coming close: 2-3 milliseconds as a target. Nokia recently demonstrated 2 millisecond latency between a base station and a handset in an LTE context, with SK Telecom.
Kin-Yip Liu, senior director for systems engineering and segment marketing for Cambium Networks, agreed that operators are thinking hard about their architectures and fronthaul options now, with an eye toward 5G. “This is an area with multiple options for engineering and management, as well as for testing to understand the fronthaul and different split options,” he said. “The real trade-off is, what is the fronthaul available and what kind of services do you plan to support? – and then to see if you can live with that fronthaul.” If it isn’t up to par, he said, operators will have to make different split choices. Sundhar said that the structures that operators are exploring now, in terms of MEC and C-RAN, what they put at the edge and in the core, is “a bit at a time, slowly moving toward the ultimate goal of what they want to do in 5G.”
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