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Describe the concept of EN-DC (E-UTRAN New Radio – Dual Connectivity).

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EN-DC (E-UTRAN New Radio – Dual Connectivity) is a technology used in 5G networks that enables mobile devices to simultaneously connect to both 4G LTE (Long-Term Evolution) and 5G NR (New Radio) networks. It allows for improved data throughput, lower latency, and enhanced coverage by utilizing resources from both 4G and 5G networks.

Here's a technical breakdown of how EN-DC operates:

  1. Architecture:
    • EN-DC relies on a dual connectivity architecture where the mobile device establishes and maintains connections with both 4G LTE and 5G NR base stations (eNodeBs and gNodeBs respectively).
    • The network orchestrates the simultaneous connections, coordinating data transmission and reception between the two radio access technologies (RATs).
  2. Primary and Secondary Connection:
    • The mobile device has a primary connection to the 5G NR network and a secondary connection to the 4G LTE network. The primary connection handles most of the data traffic, while the secondary connection provides additional resources and support.
  3. Data Transmission:
    • Data transmission occurs through a process called the split bearer concept. Higher-priority data is transmitted via the primary 5G NR connection, taking advantage of the higher data rates and lower latency offered by 5G.
    • Lower-priority or excess data can be transmitted through the secondary 4G LTE connection, ensuring efficient resource utilization across both networks.
  4. Carrier Aggregation and Aggregated Throughput:
    • EN-DC utilizes carrier aggregation techniques, combining multiple carriers from both 4G and 5G networks to increase overall data throughput.
    • The aggregated throughput enhances the user experience by leveraging the combined bandwidth of both networks.
  5. Radio Resource Management (RRM):
    • RRM mechanisms coordinate the allocation and management of radio resources between the primary and secondary connections. This ensures optimal utilization of available spectrum and radio channels.
  6. Seamless Handover:
    • EN-DC allows for seamless handover between 4G and 5G networks, ensuring uninterrupted connectivity as the device moves between coverage areas or as network conditions change.
    • The mobile device maintains connectivity while dynamically adjusting its connection to utilize the most suitable network resources.
  7. UE (User Equipment) Capabilities:
    • Mobile devices need to support EN-DC by having compatible hardware and software capabilities to establish dual connectivity to both 4G and 5G networks.
    • EN-DC capable devices can take advantage of the benefits offered by simultaneous connections to multiple networks.