Third-generation (3G) wireless systems have been made possible by the concerted efforts of research and development organizations, equipment manufacturers, service providers, and above all, standards bodies that took the initiative in coordinating the works of these organizations, harmonizing the specifications coming out of the laboratories, and producing a set of international standards. Many companies are now in the process of manufacturing 3G wireless equipment so that service providers can begin to roll out 3G services to their customers in the near future. NTT DoCoMo of Japan has been actively developing 3G technologies. Lucent Technologies of the United States has developed base station equipment (such as 3G1X and 3G3X) that will provide 3G services for cdma2000, UMTS, and UWC-136, and is currently conducting field trials of their equipment with DoCoMo, Vodafone, Sprint, Bell Atlantic, AT&T, and SBC. NTT DoCoMo had targeted year 2001 for nationwide deployment of a commercial 3G system.

Service providers, equipment manufacturers, and research laboratories have already begun looking beyond 3G. NTT DoCoMo is working on their vision of the fourth-generation (4G) system, and has started defining and developing 4G services and technologies [1]. Many research and development projects in Europe are studying broadband communication issues (such as the air interface standards, cell coverage characteristics, provision of the quality of service [QoS] in all IP networks, and so on) that would be relevant to 4G [2]-[5].