Abstract-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 multipleinput 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 trellisbased 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.
In this paper, orthogonal frequency-division multiplexing (OFDM) based wireless systems with cochannel interference are considered. Interference from transmitters in neighboring cells with synchronized symbol time is assumed. Due to differences in the carrier frequencies of desired user signal and interferer signal, each interferer subchannel signal is spread over many subcarriers of the receive signal (receiver synchronized on the desired user signal). Therefore, intercarrier interference (ICI) arises and common interference cancellation approaches based on prefiltering are unfavorable. We propose a detection approach, where the interferer signal is jointly detected with the desired user signal by a sequential decoding algorithm. Simulation results reveal large performance improvements for a binary phase-shift keying (BPSK) modulated 64-point discrete Fourier transform (DFT) OFDM signal with moderate-to-strong interference for realistic channels and ideal channel state information. By using additional windowing of the receive signal in time domain, further improvements may be achieved.
For conventional orthogonal frequency-division multiplexing (OFDM) systems, the guard interval is disregarded in the receiver and rectangular shaped windows are used implicitly due to the discrete Fourier transform (DFT). We consider a Nyquist-shaped window in the receiver, so that the transmit signal does not need to be modified, and optimize the window shape in order to suppress interference from non-orthogonal single carrier interferer signals. For the window coefficients, a closed form solution is derived. This type of interference usually occurs in OFDM radio systems like Digital Radio Mondiale (DRM) that are operating in low frequency bands. (Disturbance is given for instance by harmonics of switched-mode power supplies.)
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