We started our series, Convergence in the New Service Edge, with a discussion on how 4G and 5G will have to coexist in the same transport network. Convergence goes beyond wireless. Many operators offer both fixed and mobile services. However, wireline and wireless access services have typically been served by completely different aggregation and core networks. This is obviously not optimal in that it does not allow for savings from economies of scale.
5G deployments offer an opportunity for new converged architectures. 3GPP Release 16 allows the convergence of fixed and wireless networks. New architectures allow fixed and mobile broadband access to be supported by a common 5G core network. 3GPP, the Broadband Forum, and CableLabs have collaborated on technical reports and specifications to define the services and systems required to support 5G wireless and wireline convergence. The IETF provides guidance around user plane protocol revisions while the IEEE, ITU-T SG15, and Metro Ethernet Forum (MEF) have been engaged with timing/synchronization requirements and other service specifications.
Since most operators support both access technologies, a migration path to wireless and wireline convergence in the core will simplify provisioning and reduce capital and operations expenditures. Furthermore, 5G fixed wireless access (FWA) can backup or replace wireline connections. Convergence also allows operators to deliver a consistent service experience regardless of how users are connected. The need for a common core is clear.
Operators often compete across traditional boundaries to provide revenue-generating services to their subscribers. Mobile operators are purchasing content and wireline assets while MSOs are launching or expanding mobile services. The ecosystem includes the convergence of services, policy, and networks across wireless and wireline domains. A converged core may be able to avoid overlapping functions within the network and therefore reduce long-term capital expenditures or operating expenses. For example, convergence may also enable operators to more consistently deliver services and execute policy.
We see forms of convergence all the way down to the fronthaul in the 5G transport network. This is greatly facilitated by the use of packet technologies with IP deployed broadly across the transport network. While Telecom Infra Project’s Disaggregated Cell Site Gateway (DCSG) focuses on connecting cell sites, TIP’s vision extends to the consolidation of services.
Fundamentally, a DCSG is a router that runs on white box hardware and provides connectivity from a small number of cell sites to the wireless transport network. TIP has defined key features including IEEE 1588 Precision Timing Protocol (PTP), segment routing, hierarchical Quality-of-Service (QoS) on ingress and egress, traditional routing protocols, and Multiprotocol Label Switching (MPLS). TIP has published this as a specification (available to download here). The DCSG is also expected to facilitate convergence on the network by also supporting broadband (OLT) and enterprise services (CPE) as shown in the diagram.
Given the complexity of services that run on this transport network, routing is critical to ensuring service levels by using features like QoS and segment routing. In our next installment, we will look at how new 5G services will affect the transport network.