LTE Routing Area Update (RAU) Procedure

This document describes the Routing Area Update (RAU) procedure in an LTE system. RAU stands for Routing Area Update within the LTE network. We’ll cover both scenarios: RAU without a Serving Gateway (S-GW) change and RAU with an S-GW change.

RAU Procedure Without S-GW Change

Figure 1: RAU Procedure without S-GW change

Figure 1 illustrates the message flow between the different entities within the E-UTRAN (Evolved Universal Terrestrial Radio Access Network) during a Routing Area Update procedure where the Serving Gateway remains the same.

RAU Procedure With S-GW Change

Figure 2: RAU Procedure with S-GW change

Figure 2 depicts the message flow between E-UTRAN entities during an RAU procedure when the Serving Gateway is changed.

REFERENCE: 3GPP TS 23.401 version 11.3.0 Release 11