ork, rather than the user or device, performs handoffs as the user moves from one UAP to another. A UAP stores user, network and device information, capabilities and preferences. Because the UAPs can keep track of the various resources a caller uses, this architecture supports single billing and subscription. Common Access Protocol This becomes viable if wireless networks can support one or two standard access protocols. 5.4.3 Network Planning in 4G Networks Traffic in 3G and 4G networks is going to expand considerably and the growing data/multimedia traffic may lead to an increase in the total load on the PS core network (CN) domain elements, especially Fourth Generation Mobile Networks when the IP multimedia subsystem (IMS) is involved because this subsystem contains a uniform way of maintaining voice over IP (VoIP) calls and offers a platform to multimedia services. The classical teletraffic theory for the performance calculation of the PS CN domain elements can be faulty because of the high variability of burstiness in the traffic; as a result the network parameters can be underestimated. Problems with 3G/4G network planning may arise, in particular: the estimation problem of the potential number of 3G/4G users; the prediction problem of data traffic characteristics; the problem of the performance estimation of PS CN domain elements taking into account the self- similar nature of the multiservice traffic. Another important aspect of an evolution in wireless communications concerns changes in the RAN of 4G systems (4G RAN). There will also be a need to deal with the enormous amount of traffic, the base station radius needs to be small and the 4G RAN must comprise more base stations and more frequent handovers, resulting in a heavy load on the links between the elements of RAN, the remote network controller (RNC) and BSs, thereby suggesting changes to the existing 3G networks. Taking into account the above considerations it can be seen that on the CN side of 4G systems the main purpose is to minimise the change