A concatenated multitone multiple antenna scheme for multiuser uplink communications

In this paper, we describe a transmission technology approach for application in asynchronous multiuser wireless channels, i.e., reverse link. The scheme is based on the concatenation of multitone modulators with transmission over multiple antennas. It implements a form of space-frequency division multiplexing. Its efficient realization can be done via FFT and polyphase low-rate filtering. The design parameters are flexible and are chosen to cope with the users time and frequency offsets, as well as with the time-frequency channel selectivity. We also apply outer direct sequence data spreading and frequency hopping to obtain improved diversity gains and interference averaging benefits. The key aspect of the proposed asynchronous multitone multiple antenna air-interface is its intrinsic robustness to multiple access interference and channel time-frequency selectivity