We propose a robust multi-mode linear precoder based on minimum bit error rate (MBER) selection criterion for multi-input-multi-output (MIMO) systems when transmitter only acquires the fading correlations of antennas....
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ISBN:
(纸本)9780780393912
We propose a robust multi-mode linear precoder based on minimum bit error rate (MBER) selection criterion for multi-input-multi-output (MIMO) systems when transmitter only acquires the fading correlations of antennas. The key point of the scheme is that the number of substreams and modulation mode change adaptively to minimize the mean of BER by using channel correlation matrix. In addition, we analyze two special cases with very high or low correlation coefficients. Simulation results state that the proposed scheme selects the most powerful spatial mode and improves the system performance significantly.
We consider the problem of practical communication over a doubly selective (DS) channel, i.e., a time and frequency selective channel. The problem is approached in two different ways: coherent communication and noncoh...
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We consider the problem of practical communication over a doubly selective (DS) channel, i.e., a time and frequency selective channel. The problem is approached in two different ways: coherent communication and noncoherent communication, and for each communication scheme we propose practical and near-optimal equalizers and maximum-diversity precoders. Toward these ends, we adopt (1) basis expansion (BE) modeling of the channel, which allows for an efficient and unified way of describing a DS channel in both time and frequency domain; and (2) tree-search algorithms (TSAs), which facilitate near-optimal performance with low complexity.@pqdt@break@For practical coherent communication, we focus on the pulse-shaped (PS) multicarrier modulation (MCM), where controlled inter-symbol-interference (ISI) and intercarrier- interference (ICI) can be leveraged for computationally efficient receiver structures. Then, we propose a novel channel adaptive TSA with a novel fast minimum mean-squared error (MMSE) generalized decision-feedback equalizer (GDFE) preprocessing, and a rank-reduced channel estimation by using the BE channel model. Also, a new finding about optimality of MMSE-GDFE preprocessing is presented, which states that under constant modulus constellation the minimum distance property is preserved by the MMSE-GDFE preprocessing.@pqdt@break@Then, two practically realizable noncoherent equalization schemes are proposed: a sequential algorithm and a Bayesian expectation maximization (EM)-based algorithm. The sequential algorithm is derived from the optimal noncoherent metric, and made practical by a fast algorithm and a TSA to evaluate and search over the metric. The Bayesian EM-based noncoherent algorithm is derived from optimal maximum a posteriori (MAP) estimation of the BE parameters, and efficiently implemented via iteration between soft coherent equalizer and soft channel estimator. Efficient operations are accomplished using fast algorithms whose overall complexitie
In this paper, we investigate the concatenation of the multiple input multiple output (MIMO) max-d_(min) linear precoder with an outer forward error correction (FEC) code at the transmitter. At the receiver side, the ...
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ISBN:
(纸本)9781479959532
In this paper, we investigate the concatenation of the multiple input multiple output (MIMO) max-d_(min) linear precoder with an outer forward error correction (FEC) code at the transmitter. At the receiver side, the turbo equalization is taken into account, which iteratively exchanges the extrinsic information between a minimum mean square error interference canceller (MMSE IC) and a FEC decoder. The analysis done by extrinsic information transfer (EXIT) chart shows that a higher mutual information (MI) at the convergence state of the turbo equalization is observed thanks to the linear precoder. In addition, we exploit this property to propose a new precoder named max-d_(min)-mod. Numerical simulations are in accordance with the theoretical analysis, which exhibits a significant improvement of the error-rate of the turbo equalization as well as a significant gain of max-d_(min)-mod compared to original max-d_(min) precoder.
Fully-synchronous measurements of a massive multi-user multiple-input multiple-output (MU-MIMO) radio propagation channel are presented. We evaluate the ability of a massive MIMO system to spatially separate users loc...
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ISBN:
(纸本)9781467364300
Fully-synchronous measurements of a massive multi-user multiple-input multiple-output (MU-MIMO) radio propagation channel are presented. We evaluate the ability of a massive MIMO system to spatially separate users located close to each other in line-of-sight (LOS) propagation conditions. The system consists of a base-station (BS) antenna array equipped with 64 dual-polarized antenna elements (128 ports) arranged in a cylindrical configuration, and eight single-antenna users. The users are confined to a five-meter diameter circle and move randomly at pedestrian speeds. The BS antenna array is located on top of a 20 m tall building and has LOS to the users. We examine user separability by studying singular value spread of the MU-MIMO channel matrix for several subsets of BS antenna array ports, along with sum-rate capacity and achievable sum-rates with both zero-forcing and matched-filtering linear precoders. We also analyze the performance of the user with the lowest rate. Finally, a comparison between the performance offered by the massive MIMO system and that of a conventional MU-MIMO system is provided. To the best of our knowledge, this is the first report of fully-synchronous dynamic measurements of a massive MIMO system. Our investigation shows that even users located close to each other in LOS propagation conditions can be spatially separated in a massive MIMO system.
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