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eps fallback in 5g

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Here's a technical breakdown of how EPS fallback works in 5G:

  1. Dual Connectivity: One of the primary methods for ensuring a smooth transition between 5G and 4G networks is through dual connectivity. In this approach, a device can simultaneously connect to both 5G New Radio (NR) and LTE radio access networks (RANs). This allows for seamless handovers between the two technologies.
  2. NAS (Non-Access Stratum) Signaling: The EPS fallback procedure involves NAS signaling between the 5G core network (5GC) and the 4G core network (EPC - Evolved Packet Core). When a device attempts to establish a 5G connection but fails (e.g., due to lack of 5G coverage), it sends a NAS request to the 5GC. The 5GC, recognizing the need for fallback, triggers the appropriate procedures to establish a 4G connection via the EPC.
  3. Redirection or Re-selection: Once the 5GC determines that the device needs to fall back to 4G, it instructs the device to redirect or re-select a suitable LTE cell for connection. This involves evaluating available 4G cells in the vicinity and selecting the most appropriate one based on factors like signal strength, quality, load, etc.
  4. Bearer Context Activation: In the EPS fallback scenario, the bearer context, which defines the data path and associated Quality of Service (QoS) parameters, is activated in the 4G network. This ensures that data sessions, ongoing calls, or any other active services are seamlessly transferred from the 5G to the 4G network without disruption.
  5. QoS Mapping: When transitioning from 5G to 4G, it's essential to ensure that the Quality of Service parameters are maintained or appropriately mapped. The 5G QoS profiles might have to be translated or mapped to corresponding LTE QoS parameters to ensure that applications and services continue to function optimally.
  6. Fallback Trigger Conditions: The decision to initiate EPS fallback can be based on various conditions such as:
    • Unavailability of 5G coverage in the current location.
    • Signal strength or quality metrics falling below a certain threshold.
    • Network congestion or other operational constraints in the 5G network.
    • Specific service requirements that can't be met in the absence of 5G connectivity.
  7. Fallback Procedure Optimization: Network operators and equipment vendors continually optimize the EPS fallback procedure to minimize latency, ensure efficient use of network resources, and provide users with a seamless experience. This optimization might involve fine-tuning parameters, implementing intelligent algorithms, or leveraging advanced network functionalities.

EPS fallback in 5G is a critical mechanism that ensures uninterrupted connectivity for devices by allowing them to switch to the 4G LTE network when 5G connectivity is unavailable or not feasible. This involves a combination of signaling procedures, network configurations, and optimization techniques to ensure a smooth transition and consistent user experience.