Multiple Access Technologies for Next Generation Mobile Communications: Fid-Bau Portal

Multiple Access Technologies for Next Generation Mobile Communications

Fan, Pingzhi

The next generation mobile communication systems will need to support multiple services ubiquitously in different types of environments, different levels of data rates, and different mobility and traffic management techniques. Multiple access technology is a key issue to efficiently share the available scarce bandwidth among a large number of users. The choice of multiple access technique could significantly enhance or lower the service quality delivered to end users. In this talk, major multiple access technologies in the first, second and third-generation wireless cellular systems are reviewed, and possible directions for the development of appropriate multiple access technologies for next-generation mobile networks, the so-called 4G or beyond 3G (B3G), are investigated. Analogue first generation cellular communication systems made use of FDMA as a basic multiple access scheme. In digital 2G systems, TDMA is predominant. CDMA is the most commonly used form of multiple access for the third generation (3G) systems, in some cases complemented by a hybrid CDMA/TDMA scheme. To sustain a bi-directional communication between a mobile terminal and a base station, transmission resources must be provided both in the uplink and downlink directions through frequency-division duplex (FDD) or through time-division duplex (TDD). Both methods can be applied in conjunction with any of the above-described multiple access schemes. 1G and 2G systems apply FDD. In IMT2000 (3G system), both FDD and TDD modes are supported, where TD-SCDMA is a Chinese self-developed 3G standard supporting TDD mode.