that two new concepts are added: MSC and MGW (media gateway). These are briefly explained below (see Figure 9.1). According to 3GPP Rel'4, the control and user-plane traffic is separated, with MSC and MGW handling the control plane and user-plane traffic respectively. The MSC (also called an MSC server in 3GPP Rel'4) handles the call and mobility control function for CS traffic generated by registered subscribers, incoming calls from other networks, mobile-originated calls, and mobile-terminated calls. Apart from this, it is also responsible for signalling conversion (user-to-network signalling converted to network- to-network signalling). The MSC is also responsible for controlling the MGW. The MSC Fundamentals of Cellular Network Planning & Optimisation A.R. Mishra. © 2004 John Wiley & Sons, Ltd. ISBN: 0-470-86267-X 3G CORE NETWORK PLANNING AND OPTIMISATION Iu-cs Iu-ps Iu-cs Internet Iu-ps Figure 9.1 Scope of core network planning in a third-generation system (WCDMA) server, as in GSM, contains the VLR as well as other elements such as a group switch (GSW), etc. The MGW is responsible for user-plane traffic handling. The main function is switching voice and data towards the required destinations, converting the ATM traffic into time- division mode and vice versa. It is able to handle/switch both the switch and data traffic. I-cs signalling termination also takes place on the MGW. Both the versions of IP (4.0 and 6.0) are supported by the MGW. 9.2 CORE NETWORK PLANNING PROCESS The processes of network planning for both the CS core and PS core essentially remain the same as described in earlier chapters (see Figure 9.2). However, since there are changes in the radio network elements, transmission network elements and interfaces, core network planning is affected. Network elements, interfaces and signalling plans are the main areas of focus in the core network plan. In the following sections, we will go through the process and changes in the CS and PS cores in turn. 9.2.1 Circuit Switch - Core Network Planning Alt