What is TAI (tracking area identity)

In the realm of cellular networks, particularly LTE (Long-Term Evolution) and 5G, the Tracking Area Identifier (TAI) acts as a unique identifier for a designated geographical area within the network known as a Tracking Area (TA). It serves as a crucial element in managing user equipment (UE) location and handover procedures.

Understanding Tracking Areas:

• Cellular networks are vast, and for efficient management, they are divided into smaller geographical regions called Tracking Areas (TAs).
• Each TA encompasses a group of neighboring cells and is assigned a unique identifier – the Tracking Area Identifier (TAI).

Components of a TAI:

• The TAI is a three-part code, offering a hierarchical identification structure:
  1. Mobile Country Code (MCC): This three-digit code uniquely identifies the country or geographical region where the network operates. It is assigned by the International Telecommunication Union (ITU).
  2. Mobile Network Code (MNC): This is a unique identifier, typically two or three digits long, that specifies the specific mobile network operator within the country. It is assigned by the national regulatory authority.
  3. Tracking Area Code (TAC): This is a network-specific code, often a four-digit number, that uniquely identifies a particular Tracking Area within the mobile network operator's coverage area.

How TAIs are Used:

• When a UE (smartphone, tablet, etc.) attaches to the network or moves into a new TA, it registers its presence with the network by reporting the associated TAI.
• This registration process allows the network to:
  • Identify the UE's approximate location within the network.
  • Route calls and messages to the UE efficiently.
  • Initiate handover procedures when the UE moves from one TA to another.

Benefits of TAIs:

• Efficient Network Management: TAIs enable the network to manage a large number of UEs efficiently by dividing the network into smaller manageable areas.
• Location Awareness: Knowing the UE's approximate location (based on the registered TAI) is crucial for various network functions like call delivery, emergency services, and location-based services (with user consent).
• Optimized Handovers: When a UE moves between TAs, the network uses the TAI information to initiate a handover procedure, seamlessly transferring the ongoing communication to the new serving cell without call disruption.

Additional Considerations:

• The network constantly monitors cell activity and signal strength to estimate the UE's location even within a TA identified by its TAI. This can be helpful for tasks like call delivery or handover initiation.
• More sophisticated location-based services might employ additional techniques like cell identification or Time of Arrival (TOA) measurements for more precise UE positioning beyond the granularity provided by the TAI.
• In some network architectures, UEs might be assigned a Tracking Area List (TAL) containing multiple TAIs. This allows them to roam freely within the listed TAs without requiring immediate updates to the network as long as they stay within the designated areas.

Future of TAIs:

• As mobile network technologies evolve, the concept of TAIs is likely to remain relevant for managing UE location and ensuring efficient network operation.
• Advancements in UE positioning techniques and network slicing might influence how TAIs are used and managed in future cellular networks.

Conclusion:

The Tracking Area Identifier (TAI) serves as a cornerstone for identifying Tracking Areas within cellular networks. By offering a unique identifier for designated geographical areas, TAIs contribute to efficient network management, optimized handover procedures, and improved overall network performance. Even with advancements in technology, the core principles of TAIs are likely to remain essential for maintaining a robust and well-functioning mobile communication landscape.