Figure 13-4 shows a detailed interworking model when a roamer in a visited WLAN operator accesses HPLMN-based packet data services. The visited WLAN is a WLAN operator that interworks with one of the VPLMNs having a roaming relationship with the roamer’s HPLMN.
Figure 13-5 illustrates the interworking model when a roamer in a visited WLAN operator accesses VPLMN-based packet data services.
In both the cases, the HPLMN is responsible for the access control. The AAA proxy relays access control signaling and control information to the HPLMN’s AAA server.
The WLAN access gateway (WAG) is responsible for enforcing routing of packets through the PDG. In the roaming case, it resides in the VPLMN.
Figure 13-4 PS service access when a roamer in a visited WLAN operator accesses HPLMN-based packet data services.
Figure 13-5 PS service access when a roamer in a visited WLAN operator accesses VPLMN-based packet data services.
The HLR and the home subscriber server (HSS) reside in the HPLMN. These entities contain the authentication and subscription data.
As shown in Figure 13.5, both online and offline charging are supported. The system also provides capability to control a specific ongoing WLAN access session for online charging purposes.
The reference points shown in Figures 13.4 and 13.5 and their purpose are shown in Table 13-1
TABLE 13-1 Reference Points
|
Reference point |
Description |
|
Wa |
Wa is the reference point between WLAN access Network and the 3GPP AAA proxy (roaming case) or AAA Server (non roaming case). |
|
The protocols over Wa transport authentication, authorization and charging-related information in a secure manner. |
|
|
Wd |
Wd is the reference point between 3GPP AAA Server and 3GPP AAA Proxy. The protocols over Wd interface transport authentication, authorization and related information in a secure manner. |
|
Wf |
Wf is the reference point between 3GPP AAA Server/Proxy and 3GPP Offline Charging System. The protocols over Wf transport/forward offline charging information towards 3GPP operator’s Offline Charging System located in the visited network or home network where the subscriber is residing. |
|
Wg |
Wg is the reference point between 3GPPAAA Server/Proxy and the WAG. The protocols over Wg provide information needed by the WAG to perform policy enforcement functions for authorised users. |
|
It is also used to transport per-tunnel based charging information from the WAG to the AAA Proxy for roaming scenario. |
|
|
Wi |
Wi is the reference point between the Packet Data Gateway and a packet data network. The packet data network may be an operator external public or private packet data network or an intra operator packet data network, e.g. the entry point of IMS, RADIUS |
|
Accounting or Authentication, DHCP. This is similar to Gi interface in GPRS network. |
|
|
Wm |
Wm is the reference point between 3GPP AAA Server/3GPP AAA Proxy and Packet Data Gateway. AAA Server uses this interface to retrieve tunneling attributes and WLAN UE’s IP configuration parameters from/via Packet Data Gateway. |
|
Wn |
Wn is the reference point between the WLAN Access Network and the WAG. This interface is used to force traffic on a WLAN UE initiated tunnel to travel via the WAG. |
|
Wp |
This is the reference point between the WAG and PDG. |
|
Wo |
Wo is a reference point used by a 3GPP AAA Server to communicate with 3GPP Online Charging System (OCS). The protocols over |
|
Wo interface transport online charging related information so as to perform credit control for the online charged subscriber. |
|
|
Wu |
Wu is the reference point between the WLAN UE and the Packet Data Gateway. It represents the WLAN UE-initiated tunnel between the WLAN UE and the Packet Data Gateway. Transport for the Wu reference point protocol is provided by the Ww, Wn and |
|
Wp reference points, which ensure that the data are routed via the WLAN Access Gateway where routing enforcement is applied. |
|
|
Ww |
Ww is the reference point between the WLAN UE and the WLAN Access Network. |
|
Wx |
Wx is the reference point between 3GPP AAA Server and HSS. This is used to transport access and authentication related information. |
|
Wy |
Wy is the reference point between PDG and On line charging system. It is used to transport online charging related information about WLAN 3GPP IP Access so as to perform credit control for he online charged subscriber. |
|
Wz |
Wz is the reference point between PDG and Off line Charging System. It is used to transport offline charging related information about WLAN 3GPP IP Access. |
