High-Speed Downlink Access in 3G Systems: A Portent for the Evolution of 4G Systems?
01 June 2001
Due tot he need of operators to protect the high levels of investment in third generation (3G) wireless systems, it seems likely that the path to fourth generation (4G) wireless sytems will be evolutionary rather than revolutionary. Currently there are a number of proposals before standardisation bodies such as 3GPP and 3GPP2 for extending the relevant 3G systems to handle asymmetrical, packet-orientated services with very high downlink capacities. These proposals (HDR, 1XTREME, and LAS-CDMA), may represent the first steps in the emergence of true 4G systems. This paper outlines some of the innovative features of HDR, 1XTREME, and LAS-CDMA: adaptive modulation, hybrid ARQ, new fast access control schemes, new spreading codes, etc.,. On the basis of the trends inherent in these proposals, some possible directions for the development of 4G systems are discussed.