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How does Non-Standalone (NSA) mode differ from Standalone (SA) mode in 5G deployment?

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Non-Standalone (NSA) and Standalone (SA) are two deployment options for 5G networks, each with distinct technical characteristics and implications. Here's a detailed technical explanation of how NSA and SA modes differ in 5G deployment:

1. Core Network Dependency:

  • NSA (Non-Standalone): In NSA mode, 5G radio access is deployed alongside the existing 4G (LTE) core network. The 5G radio provides enhanced data rates and capacity, but it still relies on the LTE core network for control functions, including authentication, session management, and mobility management.
  • SA (Standalone): In SA mode, 5G operates independently with its own core network (5GC). The 5GC is designed from the ground up to support 5G features and capabilities. It does not rely on 4G for control functions.

2. New Core Network Architecture:

  • NSA: Since NSA mode utilizes the existing LTE core network, it does not require the deployment of a new 5G core network. This can expedite the initial rollout of 5G.
  • SA: SA mode mandates the deployment of a new 5G core network. This core network is designed to fully harness the capabilities of 5G, such as network slicing, low latency, and edge computing.

3. Network Slicing:

  • NSA: While NSA can provide some level of network slicing, it does not offer the full range of capabilities and flexibility that SA provides. Network slicing in NSA may be limited to certain services and may not be as fine-grained.
  • SA: SA mode offers comprehensive support for network slicing. It allows for the creation of multiple virtual networks (slices) with dedicated resources, quality of service (QoS) profiles, and isolation. This is essential for catering to diverse use cases, such as IoT, mission-critical services, and ultra-reliable low-latency communication (URLLC).

4. Latency and Quality of Service:

  • NSA: While NSA can deliver improved data rates and capacity compared to 4G, it may not fully realize the low-latency and stringent quality of service requirements of some 5G applications, as it relies on the LTE core network for certain control functions.
  • SA: SA mode is optimized for low latency and provides the necessary architecture for ultra-reliable, low-latency communication (URLLC) and latency-sensitive applications. It offers end-to-end control, reducing latency and improving QoS.

5. Evolved Packet Core (EPC) vs. 5G Core:

  • NSA: NSA deployments use the existing Evolved Packet Core (EPC), which was originally designed for LTE networks. While enhancements are made to support 5G radio access, the EPC has limitations in fully exploiting 5G's capabilities.
  • SA: SA deployments use the 5G Core (5GC), which is designed to take full advantage of 5G features. The 5GC is architected to support network slicing, edge computing, and the specific requirements of 5G services.

6. Phased Deployment:

  • NSA: NSA mode is often used in the initial phases of 5G deployment to leverage existing infrastructure and provide faster access to 5G services.
  • SA: SA mode is typically deployed after NSA, allowing operators to transition to a full 5G core network and take full advantage of 5G's capabilities.

In summary, Non-Standalone (NSA) mode in 5G deployment relies on the existing LTE core network for control functions, while Standalone (SA) mode introduces a new 5G core network. SA mode offers greater flexibility, lower latency, and full support for 5G features, making it suitable for a wider range of applications and use cases, particularly those that require the highest levels of performance and low latency. However, NSA mode can be a pragmatic first step in rolling out 5G services while utilizing existing infrastructure.