Page 185 - From GMS to LTE

Universal Mobile Telecommunications System (UMTS) and High-Speed Packet Access (HSPA) 171

3. SGSN informs 2. A routing area and
former RNC that the SGSN location area update
subscriber has Iu(ps) is performed
changed his location

RNC RNC

Iub Iub 1. Cell update
fails as no Iur
Node-B 1 Node-B 2 interface is
available

Figure 3.33 Cell change in PMM connected state to a cell that cannot communicate with the S‐RNC.

As the SGSN detects during the location and routing area update that there is still a
logical connection to a different RNC, it sends a message to the previous RNC that the
subscriber is no longer under its control. Thus, it is ensured that all resources that are
no longer needed to maintain the connection are released.
From the MM point of view, the Cell‐PCH is almost identical to the Cell‐FACH state.
The only difference is that no data can be transmitted to the mobile device in Cell‐PCH
state. If data is received for the mobile device while it is in Cell‐PCH state, the RNC needs
to page the mobile device first. Once the mobile device responds, the network can then put
the mobile device in Cell‐DCH or Cell‐FACH state and the data transfer can resume.
And, finally, there is the URA‐PCH state, which only requires a Cell Update message to
be sent to the network if the subscriber roams into a new URA. The URA is a new concept
that has been introduced with UMTS. It refines a location area, as shown in Figure 3.34.

Location areas

Routing areas

Service areas
Core network location concept Mapping done by RNC
Radio network location concept
UTRAN
registration
areas

Cells

Figure 3.34 Location concepts of radio and core network.