Introduction

As mobile networks evolve, the focus on designing 5G systems to support enhanced mobile broadband (eMBB) services becomes critical. These services are primarily expected to operate within the mainstream 5G frequency range, particularly in band n78 (3.4 GHz to 3.8 GHz). This blog will explore how operators can effectively design their 5G networks and integrate them with existing infrastructure, emphasizing aspects such as redundancy, gateway selection, charging mechanisms, and roaming. So, now let us look into Understanding 5G Design for Evolved Packet Core along with User-friendly LTE RF drive test tools in telecom & Cellular RF drive test equipment and User-friendly Mobile Network Monitoring Tools, Mobile Network Drive Test Tools, Mobile Network Testing Tools in detail.

5G Network Design Basics

To deploy 5G services successfully, operators need to design their networks for eMBB. This means utilizing existing mobility management entities (MMEs) to accommodate the new capabilities defined by the 3rd Generation Partnership Project (3GPP). In the current non-stand-alone (NSA) model, the new radio (NR) technology will connect directly to the serving gateway (S-GW), while the 4G eNodeB will continue to serve as the signaling point for the MME.

Redundancy in Network Design

When it comes to redundancy, 5G networks don’t introduce many new concepts compared to 4G LTE systems. Both LTE and 5G access will share the same pool of MME addresses, which means operators won’t need to set up new address pools on the radio access network (RAN) side. This streamlining is beneficial, particularly for early 5G deployments, as it eliminates the need for a separate dedicated core network (DECOR).

Gateway (GW) redundancy continues to rely on the existing mechanisms. In the Domain Name System (DNS), multiple gateways can be configured to communicate with the MME. The MME will then select a gateway based on a round-robin method or similar selection criteria as currently used.

Gateway Selection Through DNS

For gateway selection, 3GPP has introduced a new suffix, “+nc-nr,” which stands for “Network Capabilities – New Radio.” This addition to the application protocol name in DNS/NAPTR (Name Authority Pointer) records allows the MME to specify that an Access Point Name (APN) should be resolved for 5G access. In this setup, the IP addresses of the 5G Overlay GWs will be configured to support this NC-NR type, ensuring that the MME receives the relevant IP addresses and their capabilities.

If a device capable of dual connectivity with new radio (DCNR) attempts to register with the Serving GPRS Support Node (SGSN), and if all DCNR validations are successful for dynamic gateway selection, the SGSN will prioritize the service parameters from the DNS server over others when selecting a gateway.

This flexibility enables operators to roll out 5G services without needing to have dedicated 5G subscriber profiles in the Home Subscriber Server (HSS). This option can be beneficial for operators facing challenges in upgrading their HSS in time for early service launches.

Gateway Configuration and Charging Mechanisms

For mobile broadband use cases, the same services that apply to 4G access will also apply to 5G. Thus, the configurations for APNs that support 5G will be consistent with those used for 4G.

Regarding throughput, a 5G subscription is expected to support up to 4.2 Gbps. However, the Policy and Charging Rules Function (PCRF) will typically assign an Aggregate Maximum Bit Rate (AMBR) that is less than this value. This ensures that the signaling toward the PCRF/Gx and Online Charging System (OCS/Gy) remains stable and unchanged compared to 4G access.

The introduction of 5G NSA does not bring significant changes to the Charging Data Records (CDRs) structure or attributes. Generally, the evolved Packet Core (ePC) will recognize that a terminal is 5G capable, and the RAB modification process will be used to re-anchor the payload GTP tunnel from eNodeB to 5G NR. This means that all traffic associated with the bearer for GW charging will come from either 5G or 4G.

For offline charging and CDRs, there are two potential options. If the IT system does not recognize new CDRs, a new container for 5G counting may not be activated, and S-GW and P-GW CDRs will count total 4G and 5G traffic without changing the CDR structure. However, if the IT system is capable of handling new 5G CDRs, separate containers can be created to track only 5G traffic, though accuracy may vary.

Roaming Considerations

Initially, operators are advised to disable 5G support for inbound roamers. Similar to the rollout of Voice over LTE (VoLTE), it is anticipated that 5G roaming agreements will be established later. For the time being, the network should permit 5G access based on the Mobile Network Code (MNC) and Network Code (NCC) levels. There are no specific functions for suppressing 5G access for inbound roamers in the initial phase, and MMEs should prevent inbound roamers from using 5G services, regardless of their subscription status.

If the MME lacks a generic switch to manage roamers, a Diameter Routing Agent (DRA)-based solution can be implemented. The DRA routes all diameter messages to the home HSS and modifies the subscriber profile to prevent access to 5G services, ensuring that roamers connect through 4G networks.

For outbound roamers, the visited network will check with the HSS to obtain subscriber information. The DRA will ensure that any requests from foreign MMEs receive the updated access restriction status.

Lawful Interception in 5G Networks

In terms of Lawful Interception (LI), there are no new functional requirements for 5G. Existing interfaces, such as X1, X2, and X3, will continue to be used as they are. If a subscriber is subject to interception, the gateway will report both signaling and user data through these established interfaces. However, as the new throughput classes for 5G are defined, performance expectations for gateways will need to be increased.

During the initial rollout, a maximum bearer capacity of 4.2 Gbps will be available, and terminals are expected to support up to 2 Gbps. Therefore, gateways must be able to handle 2 Gbps towards the X3 interface. Some vendors have proposed throughput capabilities of up to 1.6 Gbps, and discussions are ongoing about potential increases. Other vendors have not indicated any limitations for the X3 interface.

Conclusion

Designing a 5G network for the evolved Packet Core is a complex but achievable goal. By understanding and implementing the right strategies for redundancy, gateway selection, charging mechanisms, roaming, and lawful interception, operators can create a robust framework that supports the next generation of mobile broadband services. As 5G technology continues to develop, the adaptability of existing systems will be vital for maximizing efficiency and enhancing user experiences.

About RantCell

RantCell is a powerful mobile app designed to streamline network testing, monitoring, and reporting. Built for telecom operators and businesses, RantCell’s user-friendly interface and cloud-based platform enhance network quality with ease. Also read similar articles from here.

James Montano