A Dynamic Rate Uplink Multiple Access Scheme Based on FMT Modulation

For wideband uplink radio communications, we present an adaptive multiuser access scheme based on filtered multitone (FMT) modulation. Users (or groups of users) transmitting at different rates are allocated to different bands (subchannels), not necessarily uniformly distributed, to obtain a dynamic frequency division multiple access scheme. The intersymbol interference generated in each subchannel is compensated at the base station by a decision feedback equalizer (DFE), operating on a per-user basis. The impact of interference among users is limited by the presence of a guard band between adjacent users, and a computationally efficient structure is achieved by imposing that the information bandwidth is a multiple of the guard bandwidth. Overall, the receiver has a modular architecture with a filter bank as frontend implemented with complementary filters and discrete Fourier transforms, and DFEs operating in part in the frequency domain (feedforward) and in part in the time domain (feedback).