 the mobile station, imitating a true GSM handover message. The GSM handover message is encapsulated in a 'container' that is part of the WCDMA handover message Roaming using Roaming Exchange Operator In order to interconnect GPRS and UMTS networks in different countries, one solution is to use intermediate trunking operators. A specification is defined in International Roaming Expert Group Rec. IR 34. It includes a GPRS roaming exchange (GRX). GRX is a centralized and hierarchical solution for the roaming of data traffic in GPRS and UMTS networks. Packet-based data in mobile networks can be seen as an extension of the global Internet. The global Equant IP network is used to interconnect different backbone networks in a safe way. 15.13 CHARGING AND ACCOUNTING See Figure 15.19. Charging interconnect can be illustrated based on messaging. For SMS the interconnection issues were initially not satisfactorily considered. Sites on the Internet appeared where users could send free SMS, not generating any revenues for operators, but taking lots of capacity in their networks. The solution was interconnect settlements for SMS. 15.13.1 MMS INTERCONNECT SETTLEMENTS Getting MMS Interconnect settlements in place enables the users to send MMS to other operators' users. This will bring revenues from MMS that terminates in the operator's network. Interconnection Marketing expenses, Total market Competitors Business pricing (all users) and cooperating roles User needs Revenue User segments (Other operators Market share, churn and service (Regulations) providers, content providers etc.) Service offerings Operating expenses Financial Interconnect calculations, ROCE, NPV ROI, risk Investments Network Accounting Figure 15.19 Charging interconnect - accounting 15.13.2 MMS ROAMING SETTLEMENTS MMS roaming settlements enables the users to send MMS when travelling, and enables the operator to capture revenues from roaming users: its own and others. See Figure 15.20. This will bring revenues from MMS sent by visiting subscribers. Prepaid ro