Analysis of optimum diversity combining and decision feedback equalization in dispersive Rayleigh fading

IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference

Schober³

2007

Abstract-In this paper, robust transmit beamforming (BF) for transmission over frequency-selective fading channels, taking into account the availability of imperfect channel state information at the transmitter (CSIT), is considered. In a realistic scenario, the CSIT differs from the true channel. The CSIT may be outdated due to channel variations or could be erroneous due to quantization effects and/or transmission errors. Transmit BF with reliable CSIT can improve the system performance significantly. On the other hand, pure space-time coding outperforms transmit BF if the CSIT is unreliable. The optimization criterion of the proposed robust BF scheme takes the reliability of the available CSIT in an optimum way into account. We show that the performance of the proposed robust BF scheme is upper and lower bounded by that of transmit BF with perfect CSIT and generalized delay diversity coding without instantaneous CSIT, respectively.

Section: A Optimization Of Rbf-dfementioning

confidence: 99%

“…At the receiver a multiple-input single-output (MISO-) minimum meansquared error (MMSE-) DFE is employed [13], [14]. Channel estimation has to be performed in order to calculate the feedforward (FF) filters, …”

Section: Introductionmentioning

confidence: 99%

Robust Transmit Beamforming for Frequency-Selective Fading Channels with Imperfect Channel Feedback

Jonietz

IEEE GLOBECOM 2007-2007 IEEE Global Telecommunications Conference

Schober³

2007

“…Instead, the noise correlation can be directly taken into account for equalizer filter design [9]. However, in order to be able to exploit the simple existing expressions for the SNR of the equalizer output given in [8]- [10], it is advantageous to assume the presence of a whitening filter for FIR BF-FF filter design.…”

Section: With Fir Ff-bf Filters Of Length L a At The Relays The Lengtmentioning

confidence: 99%

Cooperative Filter-and-Forward Beamforming with Linear Equalization

Liang

Ikhlef

2010 IEEE Global Telecommunications Conference GLOBECOM 2010

et al. 2010

Abstract-In this paper, we investigate filter-and-forward beamforming (FF-BF) for relay networks employing single-carrier transmission over frequency-selective channels. In contrast to prior work, we assume that the destination node is equipped with a simple linear equalizer. The FF-BF filters at the relays are optimized for maximization of the signal-to-noise ratio at the equalizer output under a joint relay power constraint. For infinite impulse response (IIR) FF-BF filters, we derive a closedform expression for the filter frequency response, and a numerical algorithm with guaranteed convergence is developed for optimization of the power allocation factor included in the expression. We also provide an efficient gradient algorithm for recursive calculation of near-optimal finite impulse response (FIR) FF-BF filters. Simulation results show that, in general, short FIR FF-BF filters are sufficient to closely approach the performance of IIR FF-BF filters even in severely frequency-selective channels and that the proposed FF-BF scheme with equalization at the destination achieves substantial performance gains compared to a previously proposed FF-BF scheme without equalization.

“…The unbiased SNR at the slicer input of an MMSE-DFE with infinite-length FF and FB filter is given by [13] …”

Section: A Optimization Criterionmentioning

confidence: 99%

“…Because of its low complexity and good performance, minimum mean-squared error (MMSE) DFE [12], [13] is employed for equalization of …”

Section: B Transmitter and Receiver Structurementioning

confidence: 99%

Combined Time-Reversal Space-Time Block coding and Transmit Beamforming for Frequency-Selective Fading Channels

Jonietz

2008 IEEE International Conference on Communications

Schober

2008

Abstract-Transmit beamforming (BF) with reliable channel state information at the transmitter (CSIT) can improve the system performance significantly. On the other hand, for unreliable CSIT pure space-time coding outperforms transmit BF. In this paper, the combination of time-reversal space-time block codes (TR-STBCs) and transmit BF for transmission over frequency-selective fading channels is considered. The proposed scheme takes the reliability of the CSIT into account in an optimum way. For unreliable CSIT, the proposed scheme yields the same diversity gains as a TR-STBC, whereas for reliable CSIT significant BF gains can be obtained in addition to the diversity gain of the TR-STBC.