RAC Routing area code

RAC, which stands for Routing Area Code, is a concept used in cellular networks to identify and manage specific geographical areas within a mobile network. It is primarily employed in Global System for Mobile Communications (GSM) networks and is used to optimize network resources and enhance the efficiency of call routing and handover procedures.

In a GSM network, the coverage area is divided into smaller units called Location Areas (LA). Each LA consists of one or more cells, which are the basic coverage units provided by the network. To further organize the network and facilitate efficient call routing and mobility management, LAs are grouped into Routing Areas (RA).

A Routing Area is a collection of one or more LAs. It acts as an administrative unit for mobility management and allows the network to handle signaling and mobility-related procedures within a defined area. By grouping LAs into RAs, the network can minimize the amount of signaling required for mobile devices to communicate with the network, reducing network congestion and optimizing resources.

Now, within each RA, the individual cells are uniquely identified using a combination of two codes: the Cell Global Identity (CGI) and the Location Area Code (LAC). The LAC identifies the LA to which the cell belongs, while the CGI provides a unique identifier for the cell within the LA.

The RA is identified by the Routing Area Code (RAC). It is a numeric value that represents a specific RA within the network. The RAC is used by the network to determine the correct RA for call routing, paging, and handover procedures. When a mobile device moves from one LA to another within the same RA, there is no need for the network to update the RA information. However, when the mobile device moves to a different RA, the network needs to update the RAC information accordingly.

The RAC information is stored and managed by the network's Home Location Register (HLR) and Visitor Location Register (VLR). The HLR contains the subscriber information and the assigned RAC for each subscriber, while the VLR stores temporary information about visiting subscribers within its coverage area.

When a mobile device initiates a call or needs to be paged, the network uses the RAC information to determine the appropriate RA and cell for routing the call or paging request. This ensures that the signaling messages are efficiently directed to the intended destination and avoids unnecessary signaling across the entire network.

In summary, the Routing Area Code (RAC) is a numerical identifier used in GSM networks to group Location Areas (LAs) into Routing Areas (RAs). RAC enables efficient call routing, mobility management, and reduces signaling overhead within specific geographical areas of the network.