WIDELY LINEAR RLS CONSTANT MODULUS ALGORITHM FOR COMPLEX-VALUED NONCIRCULAR SIGNALS

Based on the constant modulus criterion, a new Widely Linear(WL) blind equalizer and a novel widely linear recursive least square constant modulus algorithm are proposed to improve the blind equalization performance for complex-valued noncircular signals. The new algorithm takes advantage of the WL filtering theory by taking full use of second-order statistical information of the complex-valued noncircular signals. Therefore, the weight vector contains the complete second-order information of the real and imaginary parts to decrease the residual inter-symbol interference effectively. Theoretical analysis and simulation results show that the proposed scheme can significantly improve the equalization performance for complex-valued noncircular signals compared with traditional blind equalization algorithms.

Constant modulus semi-blind space-time equalizer based on structure risk minimum criterion

A new adaptive filtering principle based on capability control and semi-blind method is presented. A new semi-blind space-time equalizer based on constant modulus characteristic and structure risk minimum （SRM） criterion is also proposed. The equalizer sufficiently exploits the learning information of communication signals by using the structure information of filter itself through capability control technique. Namely, it maximizes the amount of learning information to im- prove filter tracking performance. Simulations are carried out and the result is compared with that of typical recursive least squares space-time equalizer （RLS-STE） and constant modulus semi-blind space-time equalizer （ CM-SB-STE ）. The results show that, even if with insufficient training data, the SRM constant modulus semi-blind space-time equalizer （SCM-SB-STE） keeps good tracking per- formance, showing promises in mobile wireless communications.

Widely linear UKF constant modulus algorithm for blind adaptive beamforming

Based on a uniform linear array, a new widely linear unscented Kalman filter-based constant modulus algorithm (WL-UKF-CMA) for blind adaptive beamforming is proposed. The new algorithm is designed according to the constant modulus criterion and takes full advantage of the noncircular property of the signal of interest (SOI), significantly increasing the output signal-to interference-plus-noise ratio (SINR), enhancing the convergence speed and decreasing the steady-state misadjustment. Since it requires no known training data, the proposed algorithm saves a large amount of the available spectrum. Theoretical analysis and simulation results are presented to demonstrate its superiority over the conventional linear least mean square-based CMA (L-LMS-CMA), the conventional linear recursive least square-based CMA (L-RLS-CMA), WL-LMS-CMA, WL-RLS-CMA and L-UKF-CMA.

New multitarget constant modulus array for CDMA systems

A new mulfitarget constant modulus array is proposed for CDMA systems based on least squares constant modulus algorithm. The new algorithm is called pre-despreading decision directed least squares constant modulus algorithm （D-DDLSCMA）. In the new algorithm, the pre-despreading is first applied for multitarget arrays to remove some multiple access signals, then the despreaded signal is processed by the algorithm which united the constant modulus algorithm and decision directed method. Simulation results illustrate the good performance for the proposed algorithm.

A Decorrelation Constant Modulus Algorithm for Multitarget Separation Using Adaptive Arrays

In this paper, an adaptive digital filter algorithm is presented to optimize the signal-to-noise ratio of an antenna array with multiuser signal inputs. These synchronous communication signals have constant envelope property and are transmitted through a Multiple-Input/Multiple-Output （MIMO） linear channel. This Multiuser Constant Modulus Algorithm （MU-CMA） using an antenna array can compensate for both Interuser Interference （IUI） and Intersymbol Interference （ISI）. The method is derived by minimizing the cost function of the constant modulus signals as well as cross-correlations between them. The simulation result in this paper shows the performance of this algorithm.

Robust adaptive beamforming for constant modulus signal of interest

It is required in the diagonally loaded robust adaptive beamforming the automatic determination of the loading level which is practically a challenging problem.A constant modulus restoral method is herein presented to choose the diagonal loading level adaptively for the extraction of a desired signal with constant modulus(a common feature of the phase modulation signals).By introducing the temporal smoothing technique,the proposed constant modulus restoral diagonally loaded robust adaptive beamformer provides increased capability compared with some existing robust adaptive beamformers in rejecting interferences and noise while protecting the signal-of-interest.Simulation results are included to illustrate the performance of the proposed beamformer.

Single-User Blind Channel Equalization Using Modified Constant Modulus Algorithm

A modified constant modulus algorithm (MCMA) for blind channel equalization is proposed by modifying the constant modulus error function. The MCMA is compared with the conventional constant modulus algorithm (CMA) for symbol-spaced equalization of 4PSK signals. The result shows that the performance of the MCMA is superior to that of the CMA in both convergence rate and intersymbol interference for frequency selective channels in noisy environments. Simulation results using 8PSK signals also demonstrate that a fractionally spaced equalizer can preserve performance over variations in symbol-timing phase, whereas a baud-rate equalizer cannot.

Property of the Constant Modulus Algorithm to Capture the Weak Signal

The Constant Modulus Algorithm (CMA) enjoys widespread popularity as methodsfor blind beamform-ing and equalization of communication signals, CMA is straightforward toimplement, robust, and computationally of moderate complexity. Furthermore, it is insensitive toarray imperfection. In an environment containing multiple constant modulus signals, the signalextracted by CMA depends on the relative power of the incident signals. According previous works,the CMA is prone to capture the strongest Constant Modulus (CM) signal at the output of the array.In this paper, we show that the weak CM signal could be recovered by CMA_(1-2) and CMA_(2-1) whensetting special step-size. Simulation examples confirm our remarks.

Recursive Least Squares Semi-blind Beamforming for MIMO Using Decision Directed Adaptation and Constant Modulus Criterion

A new semi-blind adaptive beamforming scheme is proposed for multi-input multi-output （MIMO） induced and spacedivision multiple-access based wireless systems that employ high order phase shift keying signaling. A minimum number of training symbols, very close to the number of receiver antenna elements, are used to provide a rough initial least squares estimate of the beamformer＇s weight vector. A novel cost function combining the constant modulus criterion with decision-directed adaptation is adopted to adapt the beamformer weight vector. This cost function can be approximated as a quadratic form with a closed-form solution, based on which we then derive the recursive least squares （RLS） semi-blind adaptive beamforming algorithm. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study. Our proposed semi-blind RLS beamforming algorithm therefore provides an efficient detection scheme for the future generation of MIMO aided mobile communication systems.

The Capture Analysis of Constant Modulus Approach for Blind Multiuser Detection

This paper analyzes the lock/capture behavior of constant modulus approach (CMA) for blind multiuser detection. Conditions under which CMA locks on the desired signal and when it captures the interferer are derived.

Blind equalization of underwater acoustic channel using a combined constant modulus algorithm

A kind of Combined Constant Modulus Algorithm (CCMA) is presented to compensate the defects of the Constant Modulus Algorithm (CMA) and the Sign Error CMA (SECMA). And CCMA is applied to the equalization of the underwater acoustic channel (UWAC). Based on the decision of the equalizer’s output, its iteration process switches between

Blind Equalization Algorithm Based on MCMA and DSE-CMA

A new blind equalization algorithm based on the modified constant modulus algorithm （MCMA） and dithered signederror constant modulus algorithm （DSE-CMA） is proposed. This dithered signed-error MCMA （DSE-MCMA） can not only reduce the computational complexity, but also recover the phase rotation in the complex channel. Simulation results have verified the analysis and indicated the good property of DSE-MCMA.

Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrayts elements, are first utilised to provide a rough initial least squares estimate of the beamformer＇s weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

Improved DSE-CMA Error Function for Blind Multiuser Interference Suppression in DS/CDMA Systems

This paper presents an improved error function of dithered signed-error constant modulus algorithm （IDSE-CMA） for blind multiuser interference suppression in DS/CDMA systems. It uses a different error function to replace the former one in sign operation of the DSE-CMA and compares their performance in multiple access interference （MAI） suppression ability. Simulations indicate that the new algorithm has better performance than the similar CMA in terms of convergence speed and steady-state performance：

Joint receiving mechanism based on blind equalization with variable step size for M-QAM modulation

The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.

Structural,electronic and elastic properties of YCu from first principles

The structural, electronic and elastic properties of YCu compound in the B2 （CsCl） phase were investigated using the density functional theory （DFT） within the generalized gradient approximation （GGA）. The electronic density of states （DOS） obtained in this way accorded weU with the results of a recent study utilizing the full-potential linearized augmented plane wave （FLAPW） method. We also found that the density of d-states at the Fermi energy was low. The calculated equilibrium properties such as lattice constant, bulk modulus and its first derivative, and the elastic constants were in good agreement with experimental and theoretical results.

Theoretics-directed effect of copper or aluminum content on the ductility characteristics of Al-based(Al_3Ti,AlTi,AlCu,AlTiCu_2)intermetallic compounds

First-principle simulations have been applied to investigate the effect of copper（Cu） or aluminum（Al） content on the ductility of Al3Ti,AlTi,AlCu,and AlTiCu2 alloys.The mechanical stable and elastic properties of Al-based intermetallic compounds are researched by density functional theory with the generalized gradient approximation（DFT-GGA）.The calculated lattice constants are in conformity with the previous experimental and theoretical data.The deduced elastic constants show that the investigated Al_3Ti,AlTi,AlCu,and AlTiCu2 structures are mechanically stable.Shear modulus,Young＇s modulus,Poisson＇s ratio,and the ratio B/G have also been figured out by using reckoned elastic constants.A further analysis of Young＇s modulus and Poisson＇s ratio reveals that the third added element copper content has significant effects on the Al-Ti-based ICs ductile character.

Blind adaptive receiver based on RLS-CMA for TH-UWB system

A novel receiver is proposed in this paper that uses the blind adaptive multi-user detection （MUD） technique to deal with the presence of multiple-access interference （MAI） and inter-symbol interference （ISI） in terms of high speed time-hopping ultra-wideband （TH-UWB） system. The receiver firstly adopts constrained recursive least squares constant modulus algorithm （RLS-CMA） to conduct adaptive decorrelation for eliminating MAI and ISI, and then uses projection approximation subspace tracking with deflation （PASTd） algorithm to launch channel estimation, do maximal ratio combining （MRC） and improve signal to interference plus noise ratio （SINR）. The simulation results show that the proposed receiver can go to convergence rapidly under all four IEEE＇s UWB channel models, the bit error ratio （BER） performance is better than that of the traditional receiver and rake receiver.