5G is the next step in the evolution of mobile networks but it is shaping up to be much more than a set of specifications for new radio access and a new packet core. It is arriving after many network functions have been virtualized, and as software-defined networking (SDN) capabilities are becoming a must-have. And it is coming at a time of tectonic changes in the radio access network (RAN) and packet core, driven by advances across all networking technologies, including massive cloudification.

The RAN has been steadily evolving from distributed to centralized architectures. With radio functions now split across different network elements, it is evolving further to become a cloud RAN. The packet core has been fully virtualized for some time and has entered the “cloud-native” stage. Content and applications are moving closer to users and devices, service providers are implementing technologies like Multi-access Edge Computing (MEC) in a distributed manner and closer to base stations to help deliver premium content, minimize latency and improve the user experience.

Service providers are already thinking about how they should rearrange, upgrade and integrate new RAN and packet core elements. Many are also starting to see 5G as a major decision point that demands a reexamination of bigger networking topics: which technologies to choose for the future, what network architectures to deploy, and which network and business strategies to embrace.

The transport network is a critical part of the end-to-end 5G solution. It is the unifying network fabric that must deliver new performance levels, reach and capabilities to address demanding new requirements. Service providers will not be able to tackle 5G’s business and technological challenges without first tackling transport. If this layer does not — or cannot—flex to meet all these new demands on the path to 5G, it will compromise quality of service (QoS) and the end-customer experience. This, in turn, may undermine service providers’ revenues, growth potential and ability to innovate.

Leading service providers are already transforming their networks in preparation for 5G. Let’s look at how 5G requirements are driving new transport network capabilities, and what is expected of the transport network in the 5G era.

• Extreme bandwidth for enhanced mobile broadband (eMBB) demands a new generation of terabit-capacity networking products that can support multigigabit cell site connectivity and network-facing interfaces that provide link speeds up to 100 GE. These products must be delivered in a variety of compact form factors and support temperature hardening for outdoor applications.
• Low latency in the transport network is seen as an infrastructure enabler that will facilitate the functional split in the RAN and the evolution to packet-based fronthaul. It is also seen as an enabler of new types of applications, including MEC and AR/VR. The transport network requires a new generation of hardware and software that can support end-to-end delay targets below 10 ms.
• Enhanced QoS is not just another set of QoS levels for 5G. It introduces the need to support parallel business cases for eMBB, ultra-reliable low latency communications (uRLLC) and massive machine-type-communication (mMTC), along with network slicing, a major new 5G capability. To meet these needs, the transport network must be ready to deal with multiservice traffic that may come from several mobile generations at once. It must also allow service providers to customize and optimize services according to demanding service-level agreement (SLA) requirements for a diverse range of new applications. These capabilities exist in many wireline networks but they are quite new in the mobile environment.
• Dynamic interconnectivity refers to new, flexible and agile ways of “stitching” physical and virtualized network functions, and diverse and distributed sets of network parts and domains such as RAN, packet core, mobile cloud data centers and MEC. To support dynamic interconnectivity, the transport network must complement new product capabilities such as programmability with innovative new networking techniques.
• Improved network synchronization capabilities are required to support the more stringent timing, frequency and phase synchronization requirements of 5G. The transport network must provide robust and flexible timing options (e.g. GNSS, SyncE, IEEE1588v2, BITS) that are suitable for many network approaches and topologies.
• Built-in network security capabilities are required as an intrinsic part of the secure-by-design approach to product and network design, not as an afterthought. The network needs to be able to protect and secure its much larger attack surface and surgically filter out harmful traffic at the perimeter.
• Programmability has become an essential network attribute. Networks need to be programmable to support SDN-based control and automation and gain the agility and flexibility required for techniques such as network slicing.

Every service provider has a unique set of network constraints and requirements. Most providers use a mix of transport technologies. That is why it is of paramount importance to have the ability to weave all transport options—microwave, optical, Ethernet/IP and broadband access—into a single network architecture that can be holistically managed and operationalized.

The combination of requirements described above is driving many service providers to consolidate their transport capabilities around one networking paradigm—IP networking, capable of seamlessly weaving all network domains into one, all-IP environment.

Mobile networks have effectively been all-IP networks since the Evolved Packet Core was introduced for LTE. This means that all interfaces in the 4G/LTE/LTE-A architecture are based on IP protocols. Given that an immense number of end-user devices use IP as their communication technology, it is easy to see why centering the transport network around the IP networking paradigm is such a good choice. IP-based mobile transport provides a solid foundation for end-to-end, cost-efficient control of all network resources, along with full operational transparency to all IP services that run in the network.

At the same time, IP networking—which is really a combination of IP, MPLS, and segment routing—can efficiently address many important dimensions, including control plane, data plane, management plane, QoS and traffic management, synchronization and security.

Interest in these new network requirements and network capabilities may extend beyond 5G service providers. For example, converged network operators may also incorporate these new network capabilities and leverage them for their wireline services for enterprise, residential and private networks. Wireline-only operators seeking to remain competitive may be able to use these capabilities to reimagine their networks and address new service frontiers, such as high reliability or low latency.

The mobile transport network will play a critical role in delivering on the full set of 5G promises. The transport layer must match new 5G radio and core capabilities and seamlessly and cost-efficiently interconnect radio access, core and cloud-distributed applications and content. It must also allow for growth and further evolution given than it may take more than a decade for the “next-G” to arrive.

Alex is a senior product marketing manager in Nokia, focused on virtualized routing applications and Nokia’s mobile transport portfolio for the 5G era. Alex started his career working on academic and research projects at the University of Belgrade, followed by harmonization of ITU-related standards and national regulatory activities. During his 20+ years in Newbridge Networks, Alcatel, Alcatel-Lucent, and Nokia, Alex has been with sales support, network design and consulting, network engineering, business development and product/solution marketing teams, covering a wide range of technologies such as IP, NFV, 3G/4G/LTE and now 5G. Additionally, in his consulting role with Nordicity, Alex has worked on projects related to spectrum management and planning, and spectrum auctions.