For the uplink of the E-UTRA long term evolution (LTE) system, single-carrier frequency-division multiple access (SC-FDMA) transmission has been selected. Frequency-domain linear and decision-feedback equalizers have been already given in the literature for an SC-FDMA transmission over a multiple- input multiple-output (MIMO) intersymbol interference (ISI) channel. In this paper, a soft-output trellis-based equalizer is proposed, taking into account the cyclic ISI structure arising in SC-FDMA, which is especially suited for turbo-encoded transmission over channels with low-to-moderate signal-to-noise ratios (SNRs). A preprocessing stage is necessary for the trellis- based equalizer consisting of a minimum mean-squared error (MMSE) MIMO linear equalizer and a MIMO prediction-error filter, whose design is addressed. Simulation results for an LTE scenario demonstrate that the novel receiver yields significant gains compared to MMSE linear equalization in particular for square MIMO systems.
['Wolfgang H. Gerstacker', 'Patrick Nickel', 'Frank Obernosterer', 'Uyen Ly Dang', 'Peter Gunreben', 'Wolfgang Koch']
Trellis-Based Receivers for SC-FDMA Transmission over MIMO ISI Channels