Mobile Packet Core

In 2G and 3G mobile networks, each group of sites are grouped into an area called the 'Routing Area' (RA).

And every group of RAs are grouped into a bigger area called the 'Location Area' (LA).

When the UE moves from one RA to another, it should perform a procedure called the 'Routing Area Update' (RAU).

This way, the network will always be able to track the UE location.

Types of RAU

• intra-SGSN RAU, occurs when the UE moves between two RAs exist under the same SGSN.
• inter-SGSN RAU, occurs when the UE moves between two RAs exist under different SGSNs.
• inter-RAT RAU, occurs when the UE moves between sites under different technologies (as example, from 2G site to 3G site, or vice versa).