What is TAC (tracking area code)

Unveiling the TAC (Tracking Area Code) in Cellular Networks

Within the realm of cellular network mobility management, the Tracking Area Code (TAC) serves as a fundamental building block for efficiently tracking the location of User Equipment (UE) like smartphones and tablets. It acts as a unique identifier for a designated area within the network, forming the core element of a larger concept called the Tracking Area (TA).

Understanding the Need for TACs:

• Cellular networks need to know the approximate location of UEs for various reasons, including:
  • Delivering calls and messages efficiently.
  • Initiating handover procedures when a UE moves between cells.
  • Facilitating location-based services.
• Continuously tracking the UE's exact location through frequent location updates can be resource-intensive for both the network and the UE's battery life.

The Role of TACs:

• TACs are essentially identification codes assigned to designated areas within the network, known as Tracking Areas (TAs). A TA typically encompasses a group of neighboring cells.
• When a UE attaches to the network or moves into a new TA, it registers its presence with the network by reporting the associated TAC.
• As long as the UE remains within the boundaries of the registered TA (identified by its TAC), it doesn't need to send frequent location updates to the network.

Benefits of Tracking Area Codes:

• Reduced Signaling Overhead: By minimizing the need for constant location updates, TACs significantly reduce signaling traffic on the network, improving overall network efficiency.
• Battery Conservation: UEs don't need to expend energy on frequent location updates, leading to extended battery life for mobile devices.
• Scalability: The TAC concept allows the network to manage a large number of UEs efficiently without being overwhelmed by constant location updates.

Technical Implementation:

• Each TA is assigned a unique 16-bit TAC value within a specific network. This value ensures no ambiguity when identifying the UE's location area.
• The specific size and configuration of TAs can vary depending on the network operator and the network technology (e.g., GSM, LTE).
• Typically, TAs are designed to cover areas with similar traffic densities. Densely populated urban areas might have smaller TAs with lower TAC values compared to rural areas with lower user concentrations and potentially higher TAC values.
• A UE can be associated with a single TA and its corresponding TAC at a time. When a UE moves from one TA to another, a handover procedure is initiated, informing the network about the new TAC (location area) and updating the relevant routing information.

Tracking Area List (TAL):

• In some network architectures, UEs might be assigned a Tracking Area List (TAL) containing multiple TACs. The UE can then roam freely within the listed TAs without requiring immediate updates to the network as long as it stays within the designated areas.

Additional Points to Consider:

• The network constantly monitors cell activity and signal strength to estimate the UE's location even within a TA identified by its TAC. 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 TAC.

Conclusion:

Tracking Area Codes (TACs) act as the cornerstones for identifying TAs within cellular networks. By establishing designated areas with unique identifiers, TACs offer a balance between network efficiency, battery life for mobile devices, and the ability to manage a large number of UEs. As mobile network technologies evolve, the concept of TACs remains relevant, ensuring efficient communication and seamless service delivery for mobile users.