II. Introduction
Nowadays it is clear that we are approaching a significant change in the field of wireless network technology. Beside the continuos growth of GSM subscribers, the building of 3G UMTS (Universal Mobile Telecommunication Network) networks is started. The great advantage of UMTS is the more efficient use of resources, and the capability to incorporate a multitude of services. Penetration of UMTS networks is expected to be very high, because the 3G mobile terminals can fulfill the user requirements of looking forward a device for all the available services. Because UMTS networks will play at least as significant role in the near future as GSM today, the importance of good network planning methods seem obvious for ensuring the cost–efficient development of UMTS network. The great size and complexity of the network architecture, furthermore the great magnitude of traffic requires algorithmically optimization for the cost–effective planning of the core transport network. There are some algorithms for planning UMTS Terrestrial Radio Access Network (UTRAN), namely connecting the Radio Base Stations (RBS) to the RNC(s) [7], [8]. On the other hand, there is no an existing efficient planning algorithm, which is able to design the core (backbone) layers of the network. The open problem areas are the following: