BT Labs and Nokia Bell Labs on how a 5G core increases the value of a converged network
Making changes in the core network is always done with some apprehension and with 5G it will likely be viewed no differently. There’s a lot at stake with the evolution to a new core architecture, which is why there are some Communications Service Providers (CSPs) that may be apprehensive to evolve from their current Evolved Packet Core (EPC), even as they add 5G New Radio (NR).
From a practical standpoint, it’s easy to understand why CSPs pushed hard to accelerate the standardization of the 5G non-stand-alone (NSA) radio architecture with EPC. This architecture can use the existing 4G EPC as the core and 4G/LTE RAN for network coverage, which allows them to add 5G NR to address network capacity constraints with minimal changes to their infrastructure and operations. Nonetheless, an NSA network isn’t a complete 5G end-to-end network until the core supports the new 5G core (5GC) functions. Upgrading an existing EPC with new 5G NR to expand existing mobile broadband services may be a short-term solution for some CSPs, but it won’t satisfy their long-term objectives.
Upgrading your current EPC won’t be enough
Simply put, CSPs cannot economically, nor technically, support the variety and multitude of devices connecting to the network and meet the broad range of new and varied 5G services requirements by merely upgrading an existing EPC. To meet the scalability, flexibility and performance to cost-effectively deliver 5G services requires a cloud-native, 5G service-based core architecture that includes separate user and control planes (CUPS) and high-bit rate provisioning.
With 4G, a cloud-native core architecture is becoming the preferred option, but with 5G a cloud-native design will be a requirement. Only by redesigning the software architecture and core functions using cloud-native design principles and IT web-based development and methodologies, can CSPs gain the necessary agility to rapidly deliver new services and reduce their time-to-market.
This is what a 5G Core will enable:
Services Based Architecture
For instance, the new 5GC introduces a new Services Based Architecture (SBA) where the 5GC control plane (CP) design is based on services exposed by network functions (NFs) using new service-based interfaces (SBIs). Once a 5GC function registers its services with the new 5G Core Network Functions Repository Function (NRF), it then simply expose services that any authorized consumer can consume, rather than having to define a new point-to-point interface and the procedures between the two network functions as an EPC requires. This offers CSPs greater flexibility and more efficiency by decoupling the service consumer from the service producer.
Improved session management
Session management is improved with a new session and service continuity mode that supports a “make before break” option and the relocation of core network functions while maintaining seamless end-user services. This will be essential for ultra-reliable low-latency communications (uRLLC) use cases with moving UEs (e.g., V2X). It also supports concurrent local and central access to a data network and multi-access edge computing (MEC) where the application at the edge data center (DC) can influence traffic routing to improve its performance.
Flow-based QoS framework
The 5GC supports a more granular, flow-based QoS framework compared to the static bearer based QoS of EPC, which means QoS can be assured on an application basis. For real-time services such as AR/VR, this new QoS framework will ensure the optimal level of user experience.
Flexible end-to-end network slicing
End-to-end network slicing includes the RAN, the core and the transport network. Network resources can be dedicated per slice, thus enabling end-to-end service differentiation. Both vertical and horizontal slicing can be specified within the same service slice enabling different slices per tenant and fulfilling different SLAs. For example, a dedicated slice can be allocated to to separate use case or service such as utilities, healthcare and automotive. Then, the CSP can slice in the same vertical by tenant, for instance in the automotive slice, between different manufacturers, each having its own SLA. Also, end user devices have the ability to simultaneously access more than one slice.
Access agnostic for seamless mobility
The 5GC is also access agnostic by design, with unified registration, authentication, session, mobility and policy management for all access types. Common interfaces for 3GPP and non-3GPP access enables seamless mobility. This will enable CSPs to eventually consolidate all their services, fixed, mobile and hybrid, on the new core. Operators should be able to deploy separate 5G network slices for fixed-only, mobile-only and converged services.
It is the combination of these features that unlocks significant value for CSPs by enabling the economic deployment of services at scale for new applications and verticals. At Nokia Bell Labs, we are exploring jointly, with BT Labs, how a 5G core could increase the value of a converged network. Next week at 5G World, we will demonstrate how fixed and mobile access networks anchored on a 5G core can support telepresence-like applications with resilient end-to-end low latency.
In the near term, CSPs will likely deploy a 5G NSA network (most likely option 3) to roll out the initial set of services and to get familiar with the new radio technology. This “step-by-step” approach minimizes the disruption and change within the network. But the full benefits of 5G cannot be realized until a 5G core is deployed. CSPs that are early adopters to a full 5G end-to-end network will have a competitive advantage in their network by providing the scalability, performance and flexibility needed to economically deliver the broad range of services envisioned. The race for 5G leadership is on.
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