um allowed errors (BER). These traffic classes and the QoS associated with them are responsible for handling packet flow (PDP contexts) in the network. The important aspects of PDP contexts include the type of PDP context, associated network elements (e.g. GSN in the case of a PS core network), and the expected QoS of a PDP context. Applications belonging to different traffic classes - WWW, Telnet, video conferencing, FTP, etc. - need different processes to achieve the desired QoS. Whenever a mobile subscriber activates a PDP context, the parameter group can be negotiated both in terms of quality (of service desired) and quantity (number of PDP contexts desired by the user). The network should be optimised SO as to meet the most stringent demands made by the subscriber in terms of quality and quantity. This means that the correct parameters have to be assigned by the network to a given application and to the availability of the necessary resources. This loops back to the initial discussion of optimising the quantity of network elements and the interfaces between them. In the initial phase of optimisation, when the traffic quantities may not be known, mea- surements can be made to observe the quality of the network. For example, for Web-related services, parameters such as the call (session) access rate and call (session) establishment time, dropped call (session) rate, etc., can be observed, which in turn are dependent upon PDP context establishment. Also, data capacities in the uplink and downlink directions can give an estimate of the end-to-end QoS of the network from the WWW perspective. Similarly, the quality of all applications important to the network should be measured, two of which are FTP and WAP file transfers. End-to-end QoS is an area that is still being explored in third-generation networks. It will remain an area of focus for some years because each new application will need a different Fourth-generation Network Planning (OFDM/ALL-IP/WLAN) Fundamentals of Critriar Network Planning di Optimisation A