be available from the operator's marketing department and may be used to dimension the traffic due to a given service. Network Naming and Numbering Plan The network naming and numbering convention is important. It should be considered during the network assessment phase. For an existing network, a study of the existing naming and numbering principles should be done. Network element signalling point codes, engineering numbers (i.e. global title address, roaming numbers, handover numbers, etc.), allocated subscriber number ranges and IMSI number ranges for each HLR should be determined with the operator. This information is important when preparing the detailed design document for preparing network element source data. For a completely new network an elaborate numbering plan is required from the operator. Once a number or number ranges have been allocated and used in the network, any change may cause unforeseen failures in the network. Naming and numbering schemes should leave enough room for future network elements, expansions and addressing requirements. Traffic Model of a Switching Element It is very important to get accurate data concerning network traffic (see Figure 4.2). The operator may provide the latest traffic data from an existing network. It is recommended, however, to generate the repartition matrix (to own network, to other networks, regional) with the help of a planning tool. The main traffic model inputs are: subscriber growth per phase: phase 1, phase 2, phase 3, etc.; subscriber distribution per network site; ratio of 2G to 3G subscribers; traffic per VLR attached subscriber (2G, 3G); mean holding time of calls (voice and video); Network Design Process ratio of CS (transparent and nontransparent) data calls to total number of calls; traffic percentage share: M-L (mobile to land), L-M (land to mobile), M-M (mobile to mobile). It is assumed that MOC + MTC = 100%. Thus either of the two values is needed. Also the percentages of 'subscribers to own network' and 'loop back of incoming' traffic are nee