FRAMES-hybrid multiple access technology

European Research Program ACTS (Advanced Communication Technologies and Services) started at the end of 1995 to support collaborative mobile research and development. Within ACTS the project FRAMES (Future Radio Wideband Multiple Access System) has been set up with an objective to define the UMTS radio access system. The first target of FRAMES is to investigate hybrid multiple access technologies and based on thorough evaluation of several candidate schemes select the best combination as a basis for further detailed development of the UMTS radio access system. The two hybrid multiple access evaluated schemes integrate a range of multiple access techniques that will lead to an optimised selection of the multiple access method for the UMTS. The first hybrid, slotted multiple access (SMA), has basically a TDMA platform. Furthermore, it contains a CDMA component which overcomes the near far problem of conventional CDMA. Also multicarrier techniques are included. Different bit rates can be flexibly provided by assigning different numbers of time slots, of carriers and of CDMA codes to a user. The second hybrid, code and time division multiple access (CATS) has basically a CDMA platform. It also includes an option for OFDM techniques in the downlink. Furthermore, by using multiuser detection CATS eliminates some of the typical CDMA drawbacks; thus has a very good spectral efficiency, just as its SMA counterpart