Multiuser Detection/Decoding in Asynchronous Multitone Multiple Access Systems
27 October 2002
We formulate the optimum multicarrier multiuser detector to be deployed in asynchronous multitone multiuser systems. These multiple access systems are based on combining discrete multitone (DMT) or filtered multitone (FMT) modulation with multiplexing of tones across distinct users. Communications are asynchronous, e.g., uplink cellular communications: signals belonging to distinct users experience time and frequency asynchronism and propagate through independent frequency selective fading channels. The optimum detector is a soft-in soft-out module that can be deconcatenated with the channel decoders (when channel coding is deployed). Thus, we also investigate pratical decoding based on iterative (turbo) multicarrier-user detection and decoding. Simplified detection schemes are also devised and their performance evaluated.