Receiver structures for multiple access OFDM

Orthogonal frequency division multiplexing (OFDM) is an attractive technique for future wireless access. A major benefit of OFDM is its ability to support high-speed transmission in highly dispersive fading environments. Multiple access OFDM is based on organizing a wideband OFDM signal into clusters of tones in frequency, as well as a number of time-slots in time, that can be accessed by different users communicating with a base station. One of the main challenges associated with multiple access OFDM is how to effectively separate signals in both the base station and terminal receivers. In this paper, we examine receiver structures for both the downlink and uplink. We show that a single long discrete Fourier transform (DFT) with receiver windowing is attractive for terminals, but a filter-and-decimate structure with multiple short DFTs is more appropriate for base stations