1 White Paper 5G Non-Standalone to 5G Standalone made real 5G Non-Standalone to 5G Standalone made real New opportunities for Communications Service Providers White Paper Many CSPs are deploying 5G NSA with the aim of evolving to 5G SA as the technology matures. This calls for the transition from 5G NSA to 5G SA to be straightforward for the CSP and transparent to the end user. This paper describes ways to make that transition happen, focusing on the 5G core. 2 White Paper 5G Non-Standalone to 5G Standalone made real Introduction 3 5G core - ready for networks 3 5G NSA deployment 4 5G SA deployment 4 Benefits of 5G SA and new use cases for monetization 4 Bringing the components together 5 5G Non-Standalone to Standalone Made Real 9 Packet Core and Control and User plane separation 9 Data Management 11 Location services 13 Signalling and Routing 14 Operations, administration and management 14 Role of Core Engineered Solution to simplify migration 15 Conclusion 16 Abbreviations 16 Contents 3 White Paper 5G Non-Standalone to 5G Standalone made real Introduction By the end of 2025, Ovum expects there to be 3 bilion 5G subscriptions, which wil be worth USD 800 bilion in anual subscription fes. 3GP has defined several deployment options to hasten the introduction of 5G while supporting a move to fuller 5G services. The industry has aligned on options Non-Standalone (NSA)3X and Standalone (SA)2. Option NSA3X alows Communications Service Providers (CSPs) to quickly deploy 5G enhanced mobile broadband (eMBB) service on top of their existing 4G core and radio networks, using 5G radios to provide high-speed, low-latency data capabilities for their customers. Option SA2 enables CSPs to offer their customers the full capabilities of 5G technology through the addition of a cloud-native 5G core. 5G core - ready for networks Many CSPs have introduced the 5G NSA deployment option 3X, shortly caled NSA3X in the folowing. NSA3x is supported by many smartphones able to alow higher data speeds. As well as smartphones, many different types of device can connect. All devices, from smartphones to data sticks to Internet of Things (IoT) sensors, are referred to by the generic term User Equipment (UE). NSA3x enables 5G radio acess by leveraging the existing 4G core, the Evolved Packet Core (EPC). The 5G core can be introduced in parallel to the existing EPC as an evolutionary step based on deployment options such as SA2, SA5 and NSA7. Currently the industry is mainly using SA2 as the next step. EPC and 5G core wil both continue to exist to provide support existing 4G devices, while 5G core wil be the only core network option for 5G greenfield CSPs. Even then, roaming wil require connectivity to 3G or 4G serving Public Land Mobile Networks (PLMNs). Figure 1. 5G core and Evolved Packet Core EPC LTE 5G NSA 3x UE NR EPC LTE 5G NSA 3x UE NR 5GC 5G SA2 UE NR 5GC 5G SA2 UE 4 White Paper 5G Non-Standalone to 5G Standalone made real 5G NSA deployment 5G NSA Option 3/3A/3X is based on LTE-New Radio (NR) Dual Connectivity (simultaneous connectivity via LTE and NR) with EPC, where LTE becomes the master and NR is secondary. This option enables the use of 5G spectrum and offers services including Fixed Wireless Access (FWA). Moderate enhancements are required for EPC to the MME, S/P-GW, HSS and PCRF. Many initial rolouts use NSA3X to provide enhanced mobile broadband with reliable conectivity. While this alows early 5G deployment, it canot achieve many 5G capabilities such as end-to- end network slicing. A further disadvantage is that dual connectivity shortens UE battery life. 5G SA deployment 5G stand-alone deployment option 2 (SA2) is based on NR connected directly to the 5G Core, bringing several advantages over the NSA3X option: Single radio connectivity, only NR without simultaneous LTE connectivity 5G core can scale quickly to meet changing service demands not seen in traditional broadband and voice. New services like massive cellular IoT, Augmented Reality (AR) and Virtual Reality (VR) wil depend on the 5G cores lower latency, higher data rates, and increased scale. 5G core offers increased security and privacy. 3GPP-defined 5G UE authentication is more secure than 4G to protect the CSP and its customers against increasing cyber- threats. End-to-end network slicing is supported, enabling CSPs to provide tight Service Level Agreements (SLAs) for customer segments. The 5G core is access agnostic, equally handling 3GPP and non-3GPP technologies such as fixed line access. Benefits of 5G SA and new use cases for monetization Distributed cloud Traditional networks are highly centralized and optimized to provide mainly bandwidth and capacity. Different characteristics of a wider range of services and applications require both centralized and distributed network deployment architectures. For example, some mobile services wil require low latency under full mobility conditions, such as autonomous vehicles that need a radio latency of around 1ms. Multi-Access Edge Computing (MEC) resources wil support these low latency use cases with two main features: A new Session and Service Continuity mode called “make before break” allows no interuption of services when a UE transfers from one edge data center to another. This is the only way to serve low latency use cases for moving UEs. Distributed cloud hosts telco functions, additionaly MEC resources can be used to host to a real user aplication. Using MEC APIs, the entire aplication re-allocation can be initiated by the 5G core to keep a users latency within agreed limits. Network slices for diferent industry verticals The 3GPP has defined several network slices profiles: eMBB for mobility and high throughput, massive IoT to handle massive number of devices providing high uplink throughput and URLLC 5 White Paper 5G Non-Standalone to 5G Standalone made real requiring security and reliability. Nevertheless, new 5G services may require further slice definitions. eMBB premium subscriptions (FWA, Enterprise): a CSP may offer a FWA service for home and business users - not simply providing FWA as a high bandwidth, reliable access but defining a slice for this segment to offer enhanced quality and customization to existing services/subscriptions for consumers and business customers. New 5G use cases (Cloud gaming, AR/VR, robotics, etc.): tailored network slice for demanding service requirements for new use cases. Alternative for private network (Industry 4.0 where AI is used in production or public safety communication): a more cost-effective and faster time to market solution than a fuly dedicated private network Special services (IoT, logistics): a network slice is tailored to a use case whose characteristics may be different from MB. Can require less capacity than MB but is business critical. These scenarios show how a 5G core network slice can be adapted to a specific use case. This allows CSPs to meet diferent customer needs with slice definitions. The most important factor is to analyze customer neds and design the service acordingly, with the 5G core providing a flexible and programable platform. Figure 2. 5G deployment waves Bringing the components together 5G Core Service Based Architecture 5G Core architecture is fully based on cloud native concepts and allows easily leveraging all advantages of cloud-native applications like webscale deployments and automation. This new architecture is not restricted to SA2 deployments. Instead of defining peer-to-peer interfaces as in previous mobile network generations, services are defined. Service producers are network functions (NFs) where the service is processed. Service consumers are NFs that use the services provided by CSPs. One NF can be a provider for one service, while also being a consumer of another service. Mass market NSA SA trials FWA/eMBB Migration to SA Rel 16 initial deployments Mass market SA, Rel-16 Industrial IoT Business verticals E2E net work slicing 5G Phase 1 5G Phase 2 5G Phase 3 and beyond 5G coverage 5G performance, capacity, new use cases 6 White Paper 5G Non-Standalone to 5G Standalone made real Service producers provide their services via http-2 Service Based Interfaces (SBI). These consist of a list of operations, divided into functionality groups known as services. Diferent services belonging to the same SBI are independent. Figure 3. The 5G Service Based Architecture Each NF that acts as a service producer reveals its interfaces and corresponding services via a central Network Repository Function (NRF), which is used by NFs (service consumers) to find services. The service producer can run diferent services belonging to the same interface on diferent addresses. The same service can even be run on diferent addresses depending on further parameters, such as slice ID. The service consumer is free to use just some of the services provided on a specific interface. This means that diferent services of the same interface can be requested with diferent performance requirements. As the services have independent functionality, they can be implemented by independent modules in the service producer. This coresponds to a microservice architecture in which each service is implemented by different microservices that can scale independently to meet the needs of a service producer. This helps to ensure optimal use of resources for the 5G system. Diferent models are possible for communication between NFs on service-based interfaces. Nokia recommends the so-called model “B” mainly for small deployments. This model uses direct communication betwen NFs. NRF alows service consumers to dynamicaly discover the addresses of corresponding service producers. Service Communication Proxy (SCP) is recommended for bigger deployments. SCP-based deployment simplifies the network structure and centralizes common functionality like load balancing, monitoring and overload control. SMFAMF SBA Bus NRF NSSF UDM AUSF AF NEFPCF SMSF UDSF UDR NSSAF SCP 7 White Paper 5G Non-Standalone to 5G Standalone made real One of the main principles of 5G is that services have independent functionality and are mostly stateless (decoupled from storage resources), so they can be instantiated and scaled according to network demand. This alows 5G services to be implemented by independent smal modules rather than large servers. This corresponds to a cloud-native architecture in which each service can be implemented by diferent microservices that can scale independently acording to CSP requirements to help ensure the most effective use of resources for the 5G system. Packet Core migration: combo nodes and Control and User Plane Separation (CUPS) Packet core migration is one of the NSA3X deployment options, at least for the control and the user plane of the gateways. Most legacy gateways are not ready for the basic use case of NSA3X for high bit rates because they do not suport the separation of control and user planes, which avoids heavy transport loads by distributing the user plane. This distribution also allows low latency, at least for static UEs, or for UEs moving to certain areas. The interworking of 4G and 5G also requires a combination of Session Management Function (SMF)/ Packet Data Network Gateway-c (PGW-c) and UPF/PGW-u, in other words a combination of HSS/UDM, PCRF/PCF. This is the 3GP standard for suporting IP adres continuity when a UE moves from 5G to 4G coverage or vice-versa. Adopting more use cases than the eMBB can suport requires a move to 5G core. To work with verticals and enterprises, a CSP wil need to support network slicing to ensure security and SLA requirements are handled cost-effectively. Edge data centers must be integrated rapidly with the help of 3GPP features and not treated simply as locations to deploy functions. A new session and service continuity mode ensures no interruption of services when a UE moves between edge data centers. Ultra-reliability requires 5G core features such as redundant user plane paths, with the enhanced resilience offered by functions/services in the control plane acting as a falback for extreme events such as a failure of a complete data center. Subscriber data management As with earlier mobile network architectures, subscription data and the corresponding management functions are esential for the availability of the whole 5G System. This is particularly important during the introductory phase, where stability issues may lead to message storms that are more likely than within mature networks like EPC. Distributed across multiple sites, the Nokia SDM diferentiates strictly between stateful Unified Data Repository (UDR) and state-les aplications, for example Home Subscriber Servers (HS), Unified Data Management (UDM) and Policy Control Function (PCF). The 5G core solution uses proven techniques to handle large overloads, including those caused by unexpected UE behavior, such as toggling between 3G/4G/5G network access registrations to attach to the preferred network. Service continuity, fulfil regulatory requirements Even if the 5G core is introduced for new services and new service architectures like network slicing, subscribers wil stil expect continuity of their existing services, such as voice. Emergency calls must be posible and lawful interception is required for voice cals and canot simply rely on intercepting the “data” to support cases like call forwarding. Multimedia Priority Services must also be available in the 5G core. The 5G NSA solution uses the existing LTE radio and core for all these aspects. Voice in the 3X architecture is either IMS based VoLTE or relies on CS Fallback. In the SA architecture, voice 8 White Paper 5G Non-Standalone to 5G Standalone made real becomes IMS based VoIP, using the EPS Fallback or Voice over New Radio (VoNR). Further details can be found in the Nokia paper (Voice over 5G The options for deployment). This also describes several solutions for emergency calls. During the initial deployment of the 5G Core, the use of emergency fallback is recommended, as it reuses all the cell to emergency-center mapping. Figure 4. 5G voice support in the VoX core Policy and charging The role of policy management has dramatically changed over the last few years, resulting in ever more complex rules and creating a need for a better rules engine. In 5G SA deployment, the 5G cores cloud-native network function PCF is designed to meet these challenges: The access agnostic 5G core must deal with a growing range of devices and the subsequent increase in the number of rules 5G diverse IoT use cases like Long Range (LoRA) IoT or mMTC require a huge number of new rules that may be invoked with different types of trigger. Designed for the 5G era, charging functions must provide real-time rating and charging capabilities to enable new monetization opportunities for digital service providers. They must be tightly integrated with adjacent BSS capabilities such as mediation, billing and a rich set of analytics capabilities.