The first commercial service of the 3rd generation (3G) mobile communication system, IMT-2000 (International Mobile Telecommunications), was launched in October 2001 in Japan. This is the first 3G service employing Wideband Code Division Multiple Access (W-CDMA) as its air interface between mobile terminals and base stations. This new system, 3G, is expected to accelerate the deployment of future mobile multimedia services, which substantially got started with the "i-mode" service in February 1999 in Japan. Research activities into future mobile communication systems capable of supporting a vastly expanded market for mobile multimedia services are underway worldwide. This paper describes the vision, service trends, and technical challenges of such future systems. Broadband packet wireless access, Variable Spreading Factor Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM), are promising candidates for realizing future mobile communication systems that provide higher transmission rates and capacity than 3G systems.
Capacity improvement in CDMA and FDMA cellular mobile communication systems using adaptive antennas