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RA Routing Area

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In the context of mobile telecommunications, a Routing Area (RA) is a geographical area defined within a Public Land Mobile Network (PLMN) where a group of cells are grouped together for routing and tracking purposes. The concept of RA is primarily used in 2G, 3G, and 4G mobile networks, such as GSM, UMTS, and LTE.

A Routing Area serves as an intermediate routing entity between a mobile device (also known as User Equipment or UE) and the core network of a mobile operator. Its purpose is to manage the mobility of UEs within a certain geographic region efficiently. When a UE moves from one cell to another, it needs to update its location information so that incoming calls, messages, or data can be delivered correctly.

Here's how the RA routing process typically works:

  1. Location Area (LA): A mobile network is divided into larger geographic areas called Location Areas. Each Location Area consists of multiple cells and serves as a higher-level routing entity. When a UE moves from one Location Area to another, it needs to perform a Location Area Update to update its location information in the network.
  2. Routing Area (RA): Each Location Area is further divided into smaller Routing Areas. The purpose of a Routing Area is to reduce the signaling overhead when a UE moves between cells within the same Location Area. When a UE moves from one cell to another within the same Routing Area, it does not need to perform a full Location Area Update but only a Routing Area Update.
  3. RA Identity: Each Routing Area is assigned a unique identifier known as the Routing Area Identity (RAI). The RAI is used to identify the Routing Area to which a UE belongs. It is composed of two parts: the Mobile Country Code (MCC) and the Mobile Network Code (MNC), which uniquely identify the mobile operator, and the Routing Area Code (RAC), which identifies the specific Routing Area within the operator's network.
  4. Routing Area Update: When a UE moves from one cell to another within the same Routing Area, it periodically sends Routing Area Update messages to the network. These messages contain the UE's identity and location information, such as the RAI and the Cell Global Identity (CGI) of the serving cell. The network uses this information to update the UE's location and route incoming calls or messages appropriately.
  5. Paging: When an incoming call or message arrives for a UE, the network needs to locate the UE within the network. If the UE is registered in the same Routing Area where the call or message originates, the network can directly page the UE in that Routing Area. This reduces the paging signaling and improves the efficiency of call setup or message delivery.

By dividing the network into Routing Areas, the signaling overhead and processing load on the network are reduced compared to a system where each cell is treated individually. Routing Areas help optimize network performance, reduce signaling traffic, and improve the overall efficiency of mobility management in mobile networks.