is due to its own subscribers and traffic coming in from external sources (or local exchange). This is the CORE NETWORK PLANNING PROCESS scenario represented by Figure 4.2(a). Before the dimensioning starts, few parameters need to be understood and defined: Subscribers originating (SO): This is the traffic originated by subscribers of the network. Generally, this input comes from the network (or network operator). Typical values can be 65% for the switch and/or 50% for the LE. Subscribers terminating (ST): This is the traffic that is being terminated in the same mobile network. This value can be calculated as ST = 100% minus SO. Own network (terminating) traffic: This is the traffic that is originated in the network and terminated there also. It is usually a product of subscribers in the network and SO. Loop back of incoming traffic: This is the traffic originating from the external networks and routed back to them. Outgoing and incoming traffic: Traffic going outside the mobile network to an external network is outgoing traffic, while traffic coming from external networks is incoming traffic. These can be calculated as follows: Incoming = (ST - own network traffic), / (I - loop back of incoming traffic) Outgoing = SO - own network traffic + loop back of incoming traffic. Voice-mail system and interactive voice response (IVR) traffic: Traffic related to voice- mail is of two types: forwarded and listen. If the traffic is diverted to voice-mail when the subscriber is not available, it is known as VMS forwarded traffic, while traffic generated to listen to voice messages is the VMS listen traffic. IVR is the traffic generated through interactive responses, when a recorded voice responds rather than a subscriber (e.g. 'Press 1 for Hindi, press 2 for English Inter-switch traffic: This is calculated on the basis of the incoming and outgoing traffic. Generally tools are used for this. An example is shown later in Figure 4.6. Another important parameter related to subscriber behaviour is the 'calling and moving interest