For example: What is the right MMS price level? The relationships for buying and selling content, interconnection and roaming services keep increasing in complexity and values. It is becoming increasingly important for operators to make sure that they can charge and get paid for everything they have delivered to their partners. Another requirement is Understanding Changing Telecommunications - Building a Successful Telecom Business Home PLMN: Sweden Home SN backbone network IVITY MMS roaming settlement Bac bone MMS interconnect Net vork settlement Backbone MMS-C Network Visiting PLMN: Visiting SN Singapore Charge user for MMS Figure 15.20 MMS roaming charging to be able to verify and make sure that the claims from their partners are correct, in order to avoid being overcharged. 15.14 POSSIBLE INTERWORKING UMTS-WLAN This type of interworking might become very common in the future, including roaming. 15.14.1 REQUIREMENTS A cooperation of UMTS-WLAN combines the wide-area benefit of 3G with its unlim- ited roaming and mobility with the additional throughput and capacity by WLAN in hot spots. WLAN surf points are increasing quickly all over the world with a predicted num- ber of 120 000 in 2007 (Source: Gartner-Dataquest). WLAN users can be part of the 3G-operator subscriber base and UMTS-WLAN operators are enabled to offer further 3G packet service expansion with small investment costs. However, UMTS-WLAN inter- working standardization could be limited to a small set of standardization items, allowing reuse of 3G subscriber management mechanism, 3G authentication and security functions and billing functions. See Figure 15.21. Not reusing the 3G-mobility management allows to use WLAN as an IP access net- work complementary to current UMTS packet-switched domains. Thereby the impact on the UMTS systems is minimized and the need for a common 3GPP and WLAN stan- dardization is reduced. A common billing between the systems is already in use. See Figure 15.22. Interconnection Functionality within WRAN and access to UMTS fu