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tracking area update in 5g

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In 5G (Fifth Generation) mobile networks, the concept of Tracking Area Update (TAU) is integral to the mobility management procedures. TAU is a process in which a mobile device informs the network about its current tracking area, allowing the network to keep track of the device's location. Let's explore the technical details of Tracking Area Update in 5G:

1. Definition and Purpose:

  • Tracking Area:
    • A tracking area is a group of cells that are managed by the same set of tracking area identity (TAI) parameters.
    • The TAI uniquely identifies a tracking area within the PLMN (Public Land Mobile Network).
  • TAU Procedure:
    • Tracking Area Update is the procedure through which a mobile device informs the network about its presence in a new tracking area.
    • TAU helps the network keep track of the mobile device's location for routing and management purposes.

2. TAI (Tracking Area Identity):

  • TAI Structure:
    • TAI is composed of a PLMN Identifier (PLMN-ID) and a TAC (Tracking Area Code).
    • PLMN-ID uniquely identifies the PLMN, and TAC identifies the specific tracking area within that PLMN.
  • Unique Identification:
    • TAI provides a unique identity for a tracking area within the network.
    • It is used to route incoming calls and messages to the correct location when a mobile device is in the connected state.

3. Events Triggering TAU:

  • Location Area Change:
    • When the mobile device moves to a different tracking area, a TAU is triggered to inform the network of the change in location.
  • Timer Expiry:
    • TAU can be triggered when a timer associated with TAU expires. Periodic TAU updates are performed to keep the network updated about the device's location.
  • Network Command:
    • The network may command the mobile device to perform a TAU, for example, for optimization purposes or due to specific network conditions.

4. TAC and PLMN-ID Update:

  • TAC Update:
    • When a mobile device moves to a new tracking area, the TAC within the TAI changes.
    • The mobile device includes the updated TAI in the TAU procedure.
  • PLMN-ID Update:
    • If the mobile device moves to a different PLMN, the PLMN-ID within the TAI changes.
    • The TAU procedure includes the updated TAI with the new PLMN-ID.

5. TAC and PLMN-ID Verification:

  • Verification by the Network:
    • The network verifies the received TAI to ensure that the mobile device is in the correct tracking area and PLMN.
    • This verification is crucial for accurate routing and management.

6. Security Aspects:

  • Authentication and Encryption:
    • The TAU procedure involves authentication and encryption to ensure the security of signaling messages exchanged between the mobile device and the network.
  • Integrity Protection:
    • Integrity protection mechanisms are employed to prevent unauthorized modifications to TAU signaling messages.

7. TAC and PLMN Update in Core Network:

  • Update in Mobility Management Entity (MME):
    • The MME (Mobility Management Entity) in the core network is responsible for updating the TAC and PLMN information associated with the mobile device.
  • Update in Home Subscriber Server (HSS):
    • The HSS (Home Subscriber Server) may also be updated with the new TAC and PLMN information for the subscriber.

8. User Plane Handling:

  • Routing Considerations:
    • The TAU procedure ensures that the user plane data is correctly routed to the updated location of the mobile device.

9. Optimizations and Configurations:

  • Optimization for Efficiency:
    • The network may optimize TAU procedures to reduce signaling overhead and improve network efficiency.
  • Configurable Parameters:
    • TAU-related timers and parameters are configurable in the network to adapt to specific deployment scenarios and requirements.

10. Impact on Battery Life:

  • Periodic TAU Considerations:
    • The frequency of periodic TAU updates can impact the battery life of mobile devices.
    • Balancing the need for accurate location tracking and minimizing unnecessary signaling is crucial.

Conclusion:

The Tracking Area Update (TAU) procedure in 5G is a vital element of mobility management, ensuring that the network is aware of the mobile device's location for proper routing and management. TAU involves the update of Tracking Area Identity (TAI) parameters, including the Tracking Area Code (TAC) and PLMN Identifier (PLMN-ID), allowing the network to efficiently handle user plane data and maintain accurate subscriber location information. Security measures are embedded in the TAU procedure to protect signaling messages, and the optimization of TAU parameters contributes to the overall efficiency of the 5G network.