Sign in Subscribe

tracking area code in lte

Last updated on 

In LTE (Long-Term Evolution) networks, the Tracking Area (TA) concept plays a crucial role in mobility management. To understand the Tracking Area Code (TAC), let's first break down the LTE network structure and then delve into how the TAC functions.

LTE Network Structure:

  1. LTE Cells: The basic unit of an LTE network is the cell, which can be thought of as a geographical area covered by an LTE base station (eNodeB).
  2. Tracking Area: A Tracking Area is a group of cells. Instead of tracking devices (UE - User Equipment) at the cell level, the network uses the concept of TAs to reduce signaling overhead. When a UE moves from one Tracking Area to another, it sends a Tracking Area Update (TAU) message to the network.

Tracking Area Code (TAC):

  1. Definition: The Tracking Area Code (TAC) is a unique identifier assigned to each Tracking Area within an LTE network.
  2. Purpose:
    • Efficient Mobility Management: Instead of updating the network about the location of a UE every time it moves from one cell to another, the UE informs the network when it moves from one Tracking Area to another. This reduces the frequency of signaling messages.
    • Identification: TAC helps in uniquely identifying a particular Tracking Area. This way, when a UE sends a TAU message, the network can quickly determine which area (or group of cells) the UE is currently in or moving to.
  3. Structure:
    • TAC is a 16-bit value, providing a range of 0 to 65535.
    • Different TAC values identify different Tracking Areas within the LTE network. For instance, a TAC of 1234 might represent one Tracking Area, while a TAC of 5678 might represent another.

How TAC Works in Mobility:

  1. Initial Attach: When a UE powers on or comes into an LTE coverage area, it performs an initial attach procedure. During this process, the UE establishes a connection with the network and registers its location. As part of this procedure, the UE informs the network about its current Tracking Area by sending the TAC value.
  2. Handover: As the UE moves within the LTE coverage area, it may need to handover from one eNodeB to another (or from one cell to another within the same eNodeB). The TAC remains unchanged during this intra-TA handover. If the UE moves to a cell associated with a different TAC, it will need to perform a TAU procedure to update its location with the new TAC.
  3. Tracking Area Update (TAU): If the UE moves out of its current Tracking Area, it sends a TAU message to the network. This message contains various parameters, including the new TAC (if it has changed). The network uses this information to update the UE's location and maintain efficient mobility management.