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LTE Interworking (NSA : Non StandAlone)

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LTE Interworking in the context of Non-Standalone (NSA) refers to the integration of 5G (NR - New Radio) with existing LTE (Long-Term Evolution) networks. Non-Standalone mode is one of the deployment options for 5G, where 5G NR is deployed alongside existing LTE infrastructure. This allows for a more gradual migration from LTE to 5G.

Here's a technical explanation of LTE Interworking in NSA mode:

1. Architecture Overview:

  • In NSA mode, the 5G NR radio access is added to the existing LTE network architecture.
  • LTE functions as the anchor for control signaling, and both LTE and 5G NR share the same core network.

2. Dual Connectivity:

  • Dual Connectivity is a key concept in NSA. It involves simultaneous connection to both LTE and 5G NR networks.
  • The user equipment (UE) is connected to both LTE eNB (Evolved NodeB) and 5G NR gNB (Next Generation NodeB).

3. Control Plane Architecture:

  • The LTE eNB is responsible for the control plane signaling and initial access procedures.
  • The 5G NR gNB is used for data transmission and provides additional capacity and higher data rates.

4. Data Plane Architecture:

  • The data plane is where user data is transmitted.
  • Depending on the configuration, user data can be transmitted over both LTE and 5G NR simultaneously to achieve higher data rates.

5. Bearer Setup:

  • The establishment of bearers (logical channels for data transmission) involves both LTE and 5G NR networks.
  • The LTE network establishes the initial bearer, and then secondary bearers can be established in the 5G NR network.

6. Mobility Management:

  • Mobility management is crucial for seamless handovers between LTE and 5G NR cells.
  • The UE can move between LTE and 5G NR coverage areas while maintaining connectivity.

7. Spectrum Sharing:

  • NSA mode typically involves dynamic spectrum sharing, where the same frequency band is used for both LTE and 5G NR.
  • Techniques like EN-DC (E-UTRAN NR Dual Connectivity) enable efficient sharing of spectrum resources.

8. Deployment Scenarios:

  • NSA can be deployed in various scenarios, such as using existing LTE macro cells with the addition of 5G NR, or deploying 5G NR in high-density areas to enhance capacity.

9. Core Network Functions:

  • The LTE Evolved Packet Core (EPC) coexists with the 5G Core (5GC), allowing for interoperability and smooth migration.
  • Control plane functions such as session management are handled by the LTE core, while user plane functions leverage both LTE and 5G NR.

10. End-to-End Latency Reduction:

  • NSA mode aims to reduce end-to-end latency by leveraging the enhanced capabilities of 5G NR while maintaining the existing LTE infrastructure for control signaling.

Conclusion:

LTE Interworking in Non-Standalone mode provides a pragmatic approach to the initial deployment of 5G, leveraging the strengths of both LTE and 5G NR. It allows for a smooth transition to a full 5G Standalone deployment in the future.