Multiuser detection and turbo multiuser decoding for asynchronous multitone multiple access systems

We consider multicarrier multiple access architectures that are based on combining discrete multitone (DMT) or filtered multitone (FMT) modulation with multiplexing of tones across users. Communications are asynchronous, e.g., uplink cellular communications. Optimum multiuser detection is formulated for demodulation of multitone signals that experience time and frequency asynchronism and propagate through frequency selective fading channels. Channel coding is also considered and practical decoding based on iterative (turbo) multiuser detection and decoding is investigated. Simplified detection schemes are also devised.