Discrete Multi-Tone and Filtered Multi-Tone Architectures for Broadband Asynchronous Multi-User Communications

Multi-carrier systems based on both discrete multi-tone and filtered multi-tone architectures are investigated for application to asynchronous multi-user communications. Multiplexing of users is implemented by assigning a sub-set of the available carriers to each user. Communications are asynchronous, meaning that the signals belonging to distinct users propagate through independent frequency selective fading channels, and experience time and frequency misalignments due to propagation delays and movements (e.g., uplink communications). In this scenario inter-symbol, inter-carrier, and multiple access interference arise. We study the effect of the shape of the filters, as well as of the tones allocation strategy, on the interference components. We devise design guidelines for robust asynchronous multiple access communications based on multi-carrier architectures. Finally, we report performance results from simulations for several uncoded and coded systems.