obile communications. It was developed by the ITU, which called it previously future public land mobile telecommunications system. Many problems have prevented the achievement of mutual understanding among countries regarding this system. Among the problems are frequency alloca- tion in different continents, existing different second generation infrastruc- tures, and different political interests. As a consequence a common understanding about detailed implementation technology was not achieved and IMT-2000 will not be a globally compatible technology; it will instead act as an umbrella for compatible services provided by different underlying technologies. Even though third generation systems will use different technologies, but the development of mobile terminal technology will partly solve the incompatibility problem for users. With the same terminal we will be able use different networks and the services they provide. The most important network technology for 3G is UMTS. 5.4.6.2 UMTS UMTS is a European concept for integrated mobile services and it is based on the GSM and GPRS. Its goal is to provide a wide range of mobile services wherever the user is located. For UMTS cordless (TDD), cellular and satel- lite interfaces are defined. It will provide multimedia service with data rates up to 2 Mbps for steady MSs and up to 384 Kbps for moving MSs. Mobile Communications The cellular radio access method for UMTS approved ETSI is wide- band CDMA (WCDMA). The basic operating principle is the same as in CDMA, which was introduced previously. The new frequency band at the 2-GHz range is allocated for UMTS. The channel bandwidth is 5 MHz, and each channel is used by all cells. The core network of UMTS is based on the core network of GSM and GPRS. The UMTS BSs can be added to the GSM/GPRS network to operate in parallel with GSM base stations. Even handovers between UMTS and GSM/GPRS are supported. 5.4.6.3 CDMA2000 The main 3G technology for the United States is based on second generation IS-95 CDMA. CDMA2000 is specified 