Joint design of groupwise STBC and SIC based receiver

In this letter, we propose a simple groupwise space time block code (GSTBC) which can be easily applied to a large number of transmit antennas and be effectively decoded by a low complexity successive interference cancellation (SIC) based receiver. The proposed GSTBC and SIC based receiver are jointly designed and the diversity repetition in GSTBC is used to induce the dimension expansion that can be exploited by the SIC based receiver to suppress interfering signals as well as to obtain diversity gain. Our proposed scheme provides a near maximum likelihood (ML) performance while keeping a reasonably low complexity at the receiver

SIC-based detection with list and lattice reduction for MIMO channels.

To derive low-complexity multiple-input–multiple-output (MIMO) detectors, we combine two complementary approaches, i.e., lattice reduction (LR) and list within the framework of the successive interference cancellation (SIC)-based detection. It is shown that the performance of the proposed detector, which is called the SIC-based detector with list and LR, can approach that of the maximum-likelihood (ML) detector with a short list length. For example, the signal-to-noise ratio (SNR) loss of the proposed detector, compared with that of the ML detector, is less than 1 dB for a 4 × 4 MIMO system with 16-state quadrature amplitude modulation (QAM) at a bit error rate (BER) of 10^−3 with a list length of 8

Decision feedback detection for MIMO-ISI channels: design using fixed and adaptive constraints.

In this correspondence, we investigate the decision-feedback detection for multiple-input multiple-output intersymbol-interference (MIMO-ISI) channels. First, a novel constrained symbol-by-symbol decision-feedback detector (DFD) is proposed, in which a constraint on the feedback filter provides robustness against error propagation and outperforms the conventional DFD. However, we find that an error floor is observed at high signal-to-noise ratios (SNRs) if a fixed constraint is used. To resolve this problem, we then propose an iterative symbol-by-symbol DFD in which an adaptive constraint is implicitly used to update the DFD’s coefficients. Simulation results show that the error-floor problem is overcome and that the performance becomes satisfactory at high SNRs through iterations

Critical evaluation of Jet-A spray combustion using propane chemical kinetics in gas turbine combustion simulated by KIVA-2

Jet-A spray combustion has been evaluated in gas turbine combustion with the use of propane chemical kinetics as the first approximation for the chemical reactions. Here, the numerical solutions are obtained by using the KIVA-2 computer code. The KIVA-2 code is the most developed of the available multidimensional combustion computer programs for application of the in-cylinder combustion dynamics of internal combustion engines. The released version of KIVA-2 assumes that 12 chemical species are present; the code uses an Arrhenius kinetic-controlled combustion model governed by a four-step global chemical reaction and six equilibrium reactions. Researchers efforts involve the addition of Jet-A thermophysical properties and the implementation of detailed reaction mechanisms for propane oxidation. Three different detailed reaction mechanism models are considered. The first model consists of 131 reactions and 45 species. This is considered as the full mechanism which is developed through the study of chemical kinetics of propane combustion in an enclosed chamber. The full mechanism is evaluated by comparing calculated ignition delay times with available shock tube data. However, these detailed reactions occupy too much computer memory and CPU time for the computation. Therefore, it only serves as a benchmark case by which to evaluate other simplified models. Two possible simplified models were tested in the existing computer code KIVA-2 for the same conditions as used with the full mechanism. One model is obtained through a sensitivity analysis using LSENS, the general kinetics and sensitivity analysis program code of D. A. Bittker and K. Radhakrishnan. This model consists of 45 chemical reactions and 27 species. The other model is based on the work published by C. K. Westbrook and F. L. Dryer

Extended Hubbard model for mesoscopic transport in donor arrays in silicon

Arrays of dopants in silicon are promising platforms for the quantum simulation of the Fermi-Hubbard model. We show that the simplest model with only on-site interaction is insufficient to describe the physics of an array of phosphorous donors in silicon due to the strong intersite interaction in the system. We also study the resonant tunneling transport in the array at low temperature as a mean of probing the features of the Hubbard physics, such as the Hubbard bands and the Mott gap. Two mechanisms of localization which suppresses transport in the array are investigated: The first arises from the electron-ion core attraction and is significant at low filling; the second is due to the sharp oscillation in the tunnel coupling caused by the intervalley interference of the donor electron's wavefunction. This disorder in the tunnel coupling leads to a steep exponential decay of conductance with channel length in one-dimensional arrays, but its effect is less prominent in two-dimensional ones. Hence, it is possible to observe resonant tunneling transport in a relatively large array in two dimensions

Iterative (turbo processing) receiver design of OFDM systems in the presence of carrier frequency offset.

In this paper, based on the principle of turbo processing, we propose two iterative receiver schemes for carrier fre- quency offset (CFO) compensation in orthogonal frequency division multiplexing (OFDM) systems. Our CFO compensation designs, one in time domain and the other in frequency domain, are based on joint estimation of time-varying channel and CFO. In our schemes, the random CFO problem, a challenge for conventional pilot-aid methods, can be effectively solved using iter- ative (turbo processing) schemes. Furthermore, our comparative study shows that time domain compensation (TDC) is simpler to implement but frequency domain cancellation consisting of an iterative equalizer (FDC-IE) has better bit error rate (BER) performance

Disorder influences the quantum critical transport at a superconductor-to-insulator transition

We isolated flux disorder effects on the transport at the critical point of the quantum magnetic field tuned superconductor-to-insulator transition (BSIT). The experiments employed films patterned into geometrically disordered hexagonal arrays. Spatial variations in the flux per unit cell, which grow in a perpendicular magnetic field, constitute flux disorder. The growth of flux disorder with magnetic field limited the number of BSITs exhibited by a single film due to flux matching effects. The critical metallic resistance at successive BSITs grew with flux disorder contrary to predictions of its universality. These results open the door for controlled studies of disorder effects on the universality class of an ubiquitous quantum phase transition