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TA (tracking area)

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Introduction

In cellular networks, such as GSM (Global System for Mobile Communications) and LTE (Long-Term Evolution), the concept of a Tracking Area (TA) is used to manage the mobility of mobile devices. A Tracking Area represents a geographic area within the network where a mobile device can move without requiring an update of its location information. TAs play a crucial role in optimizing network resources and facilitating seamless handovers during mobility.

Functionality

The primary function of a Tracking Area is to reduce the signaling overhead and network congestion caused by frequent location updates of mobile devices. By grouping together a set of cells into a single Tracking Area, the network can minimize the number of location updates that need to be processed when a mobile device moves within that area. This results in more efficient utilization of network resources and improved overall system performance.

Tracking Area Identity (TAI)

Each Tracking Area is uniquely identified by a Tracking Area Identity (TAI). The TAI consists of two components:

  1. Mobile Country Code (MCC) and Mobile Network Code (MNC): These are international codes that identify the country and mobile network operator to which the Tracking Area belongs. The MCC is a three-digit code, while the MNC is typically a two- or three-digit code.
  2. Tracking Area Code (TAC): The Tracking Area Code is a unique identifier within the mobile network operator's domain. It distinguishes one Tracking Area from another within the same network.

Together, the MCC, MNC, and TAC form a globally unique identifier for a specific Tracking Area.

Tracking Area Update (TAU)

When a mobile device moves from one Tracking Area to another, it needs to perform a Tracking Area Update (TAU). The TAU is a signaling procedure between the mobile device and the network that updates the device's location information and informs the network about the new Tracking Area where the device is currently located.

During a TAU, the mobile device sends a TAU Request message to the network, including its identity and the new Tracking Area's TAI. The network updates its records and acknowledges the TAU by sending a TAU Accept message back to the mobile device. The TAU procedure also involves updating the network's Mobility Management Entity (MME) and Home Location Register (HLR) with the new location information.

Benefits of Tracking Areas

The use of Tracking Areas provides several benefits in cellular networks:

  1. Reduced Signaling Overhead: By grouping cells into TAs, the frequency of location updates from mobile devices is reduced, resulting in lower signaling traffic on the network.
  2. Optimized Network Resources: TAs allow network operators to optimize their resource allocation based on the mobility patterns of mobile devices. By defining TAs appropriately, operators can allocate network resources more efficiently to meet the demand in different areas.
  3. Seamless Handovers: When a mobile device moves between cells within the same Tracking Area, handovers can be performed more seamlessly since the location update is not required. This results in improved call quality and user experience during mobility.
  4. Efficient Paging: Paging is the process of locating a mobile device when there is an incoming call or message. With TAs, the network only needs to page devices within the relevant Tracking Area, reducing the paging overhead and improving paging efficiency.

Conclusion

Tracking Areas (TAs) are an essential concept in cellular networks for managing the mobility of mobile devices. By grouping cells into TAs and assigning unique identifiers, TAs help optimize network resources, reduce signaling overhead, and facilitate seamless handovers during mobility. The Tracking Area Update (TAU) procedure ensures that the network stays informed about the location of mobile devices, enabling efficient call routing and resource allocation. Overall, TAs play a crucial role in improving the performance and efficiency of cellular networks.