ice in a secure and auditable way. Both user interfaces and interoperator interfaces have to be clearly defined, and multiple service providers should be able to interoperate under the guidelines of this architecture. The IP-enabled terminals, apart from allowing the users to access, should be able to replicate the voice service environment as in previous generations of networks. 5.6.1 Planning Model All-IP Architecture Network Configuration A layout for a possible 4G network based on the all-IP core network is shown in Figure 5.7. It comprises the core network, which performs the service control, and the radio access network, which performs the All-IP Network PSTN/ 4G RAN Inernet 4G RAN 4G RAN 3G RAN Figure 5.7 All-IP based network radio transmission and radio resource control. Mobility control is performed by the cooperation between the CN and the RAN. Information transportation in 4G systems (CN and RAN) is based on the IPs. Each mobile terminal has its own IP address and therefore the 4G systems connect to the Internet directly but connect to the PSTN or ISDN through gateways (presently also the connection to the Internet is also through the gateways). This type of network can integrate multiple types of RANs, which are based on IPs, with each other and services can be offered through a common CN. RAN Configuration In order to deploy the RAN efficiently, features of distributed base station control and multihop link connections in the new configuration are included. Comparing a 3G RAN with a 4G RAN, it can be seen that a 3G RAN has a vertical tree like structure and multiple BSs are connected to a radio network controller (RNC), which intensively controls those BSs. To enhance the radio signal quality at the cell edges, a diversity handover scheme was introduced in the 3G systems, in which, whenever a mobile terminal can communicate with multiple BSs, i.e. the MT is handed over between adjacent BSs, all layer 1 signals of the uplink (MT to BS) received at each BS are transmitted to the RNC and the RNC combine