What is nnrm28 and How Does It Work?

Introduction

The NNRM28 interface stands out as a critical element that bridges policy control and charging functions within the 5G core network. This information is about the NNRM28 interface, functionality, use cases, and significance in supporting policy-based decisions. We also discuss how this interface integrates with other network elements to enable seamless communication and efficient resource management in the 5G ecosystem.

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What is the NNRM28 5G Band?

Before we dive into the specifics of the NNRM28 interface, it’s essential to grasp the concept of the NNRM28 5G band, which shares the same nomenclature but serves a different purpose.

Overview of the NNRM28 5G Band

The NNRM28 band, also known as Band NNRM28, operates at a frequency of 700 MHz within the 5G spectrum. This low-frequency band plays a crucial role in providing extensive network coverage, particularly in remote and densely populated areas. Some key characteristics of the NNRM28 band include:

1. Superior coverage and penetration compared to higher frequency bands
2. Support for channels up to 20 MHz wide, similar to LTE
3. Limited bandwidth, which affects its ability to deliver very high speeds

Global Adoption of the NNRM28 Band

Interestingly, the NNRM28 band has gained traction worldwide. In India, for instance, most telecom operators and smartphones support this band, recognizing its importance in delivering 5G services to rural and hard-to-reach locations. Similarly, countries like the UK and South Korea have embraced the NNRM28 band to enhance their 5G network capabilities, especially for improving indoor coverage.

The NNRM28 Interface: Connecting Policy and Charging

Now that we’ve distinguished the NNRM28 band from the NNRM28 interface, let’s focus on the latter’s role in the 5G core network architecture.

Integration with the Charging Function (CHF)

The NNRM28 interface serves as a vital link between the Policy Control Function (PCF) and the Charging Function (CHF) within the 5G core network. This integration is crucial for managing both online and offline charging processes, enabling service providers to effectively monetize their network services.

Key Functions of the NNRM28 Interface

1. Spending Limit Control: The NNRM28 interface facilitates the exchange of spending limit information between the CHF and PCF, allowing for effective management and enforcement of user spending limits based on their subscription plans.
2. Communication Protocol: Utilizing HTTP/2, the NNRM28 interface ensures efficient and low-latency communication between the CHF and other network functions, thereby enhancing the overall performance of the charging system.
3. Quota Management: When a user initiates a service requiring charging, the CHF retrieves the spending limit from the PCF via the NNRM28 interface, verifying whether the user has sufficient balance to proceed.
4. Dynamic Adjustments: The CHF can make real-time adjustments to spending limits based on usage data and policy updates received from the PCF, ensuring accurate charging according to service consumption.

Main Use Cases for the NNRM28 Interface

The NNRM28 interface supports several critical use cases within the 5G core network:

1. Policy Control: By enabling communication between the PCF and CHF, the NNRM28 interface allows for the retrieval and subscription of policy counter information, crucial for making informed policy decisions.
2. Charging and Quota Management: It supports various charging scenarios, including online charging and quota handling, allowing the PCF to subscribe to specific or all counters related to user sessions.
3. Notification of Policy Changes: The NNRM28 interface enables the PCF to receive notifications about changes in policy counter information from the CHF, facilitating real-time adaptation to changing user needs and service conditions.
4. Service-Based Architecture Support: Designed to work within a service-based architecture (SBA), the NNRM28 interface allows for flexible interactions between network functions, supporting initial subscriptions during session creation and notifications upon session termination.
5. Integration with Legacy Systems: In hybrid core network configurations, the NNRM28 interface supports the integration of legacy 4G and 5G non-standalone (NSA) devices, ensuring interoperability during the transition to 5G networks.

Counter Subscription and Retrieval Process

One of the primary functions of the NNRM28 interface is to handle counter subscription and retrieval. This process involves several steps:

1. Subscribing to Counters: The PCF initiates counter subscription based on the presence of SpendingLimitRequest service configuration. It sends an HTTP POST request to the CHF to create a subscription for retrieving policy counter status and spending limit reporting.
2. Retrieving Counter Status: When needed, the PCF sends an HTTP PUT request to the CHF to modify the existing subscription, adding or removing policy counters to retrieve their status.
3. Unsubscribing from Counters: If spending limit reporting is no longer required, the PCF can unsubscribe by sending an HTTP DELETE request to the CHF, effectively deleting the subscription.

Configurations Required for the NNRM28 Interface

To ensure proper functionality of the NNRM28 interface, several key configurations must be addressed:

1. Spending Limit Subscription: This configuration allows the PCF to subscribe to spending limit notifications from the CHF, defining subscriber identifiers and specifying counter IDs to monitor.
2. Request Policy Counters: Used to add counters to the subscription list during the NNRM28 Subscribe request, this configuration can have multiple instances to create a comprehensive list of counter IDs.
3. AVP Service Configuration: This involves setting parameters for the Attribute-Value Pair service, essential for managing data exchanged over the NNRM28 interface.

Additionally, operational considerations such as notification mechanisms, endpoint configuration, and counter management must be taken into account for optimal performance.

Supporting Policy-Based Decisions

The NNRM28 interface plays a crucial role in enabling policy-based decisions within the 5G core network. Here’s how it contributes to this process:

1. Real-Time Data Access: By allowing the PCF to access and utilize real-time counter data from the CHF, the NNRM28 interface enables dynamic policy adjustments based on current network conditions and user behavior.
2. Virtual Services Integration: The retrieved counter information is integrated with Virtual Services in the PCF, facilitating policy decisions based on the current status of network resources and user activity.
3. Efficient Resource Management: The real-time data exchange supported by the NNRM28 interface allows for better management of network resources, ensuring optimal allocation and utilization.
4. Enhanced User Experience: By enabling rapid policy adjustments based on current usage patterns and network conditions, the NNRM28 interface contributes to an improved overall user experience in the 5G environment.

Comparative Analysis: NNRM28 Interface vs. Other 5G Interfaces

To better understand the significance of the NNRM28 interface, let’s compare it with other key interfaces in the 5G core network:

Interface	Primary Function	Connected Network Elements	Key Characteristics
NNRM28	Policy counter information exchange	PCF and CHF	Supports spending limit control and dynamic policy adjustments
N4	Control plane/user plane separation	SMF and UPF	Enables flexible deployment of control and user plane functions
N6	Data network connectivity	UPF and Data Network	Provides access to external data networks and services
N2	Radio access network signaling	gNB and AMF	Facilitates communication between RAN and core network
N11	Session management	AMF and SMF	Manages user sessions and bearer establishment

This comparison highlights the unique role of the NNRM28 interface in policy control and charging functions, distinguishing it from interfaces focused on other aspects of network management and connectivity.

At Last

The NNRM28 interface emerges as a critical component in the 5G core network architecture, bridging the gap between policy control and charging functions. By facilitating real-time communication between the PCF and CHF, it enables dynamic policy adjustments, efficient resource management, and enhanced user experiences. As 5G networks continue to evolve, the importance of interfaces like NNRM28 in supporting flexible, responsive, and efficient network operations cannot be overstated.

From enabling spending limit control to supporting policy-based decisions, the NNRM28 interface plays a multifaceted role in the 5G ecosystem. Its integration with other network elements and support for service-based architecture underscores its significance in the broader context of 5G technology advancement.

As we look to the future of telecommunications, the continued development and optimization of interfaces like NNRM28 will be crucial in realizing the full potential of 5G networks. By understanding and leveraging the capabilities of such interfaces, network operators and service providers can deliver innovative, reliable, and high-performance 5G services to users across diverse environments and use cases.