Page 292 - From GMS to LTE

278 From GSM to LTE-Advanced Pro and 5G

eNode‐B, which contains a target RAT indicator set to UTRA and an embedded
HandoverToUTRAN command with all parameters required for the mobile to directly
jump to the channel prepared in the UMTS cell.
Once the connection has been handed over, the mobile device has to perform a rout-
●
ing area update procedure to update the core network nodes and the HSS with its
current position.
Depending on the support of network operator voice and SMS service, a location
●
update with the CS core network might have to be performed so that the mobile
remains reachable for these services after the handover.

4.10 Interworking with CDMA2000 Networks

In some countries, for example, the United States, some CDMA2000 network operators
have chosen LTE as their next generation RAT. To allow roaming between the legacy
radio access network and LTE, a functionality similar to that for GSM and UMTS
described in Section 4.9 is required:
cell reselection between LTE and CDMA2000;
●
RRC connection release with redirect from LTE to CDMA2000;
●
inter‐RAT handover between LTE and CDMA2000.
●
To support the seamless roaming in the different access networks, 3GPP TS 23.402
[23] describes a number of new network interfaces to interconnect the two systems.
These are shown in Figure 4.24 and described in the following sections.

SGi
PDN-GW Internet

S2a

CDMA–2000 S101 MME
S103

Serving-GW

CDMA
Base
station
eNode-B
Mobile device
Figure 4.24 Interconnection of LTE and CDMA2000 networks.