基于简化LSCMA算法的STBCMC—CDMA系统盲多用户检测

在空时分组编码（STBC）的MC—CDMA系统中，根据STBC正交编码的特点，提出了一种简单可行的基于常模（CM）准则的盲多用户检测算法。该算法基于最小二乘常模算法（LSCMA）的盲多用户检测算法，算法大为简化，抽头系数减少了一半，性能略有下降。     

基于线性非冗余预编码的MIMO-OFDM系统信道估计算法

文章针对MIMO-OFDM系统中的信道估计关键技术提出了一种信道估算方法—基于线性非冗余预编码和二阶统计量的信道盲估计算法,该算法利用预编码信号的二阶统计特性消除了调制信号的信息,然后又利用STBC（Space-Time Block Coding空时分组编码）特殊的复正交特性对参考子载波信道矩阵进行变换,将求逆过程转换成简单的线性处理过程,从而实现了低复杂度的信道估计。另外,该算法通过选取合适长度的统计数据,能够较快收敛。     

智能天线MC-CDMA系统中空频联合盲多用户检测算法

提出了智能天线多载波CDMA系统中一种空域和频域联合的盲多用户自适应检测算法,它是将空域波束形成和频域合并检测合二为一,使得检测器在空域和频域两维上同时优化,从而提高了系统的检测性能.对这种空频联合检测算法的误码性能进行了分析,并与先自适应波束形成然后再进行频域合并的分步算法进行了仿真比较,仿真结果表明,提出的空频联合盲多用户自适应检测算法的检测性能优于分步检测算法.     

适用于水声信道的新的盲均衡算法

由于时变水声信道的随机相位失真，常模算法（CMA）的误码性能将严重下降。在文献[1]中双模式盲均衡算法的基础上，提出了一种适用于水声信道的新的盲均衡算法（NCMA）。计算机仿真结果表明在时变水声信道中，该算法性能优于双模式算法，能够达到信号相位失真的恢复．并且收敛性能优于双模式算法。     

CDMA移动通信系统中基于子空间的信号检测

讨论了线性空间中的子空间投影理论及其在CDMA（码分多址）移动通信系统中的应用,提出了已知各用户特征序列条件下基于子空间斜投影的多用户检测技术以及仅知目标用户特征序列条件下基于伪特征分解和子空间正交投影的盲检测技术,并通过计算机仿真进行了比较研究。     

基于ZF-DPC机制的多天线下行系统的自适应调制

以系统总速率最大化为目标，基于迫零污纸编码（ZF-DPC）机制提出了MIMO多用户下行系统的一种保障用户QoS的自适应调制方案。根据这一方案，基站应用空分多址接入（SDMA）同时支持多个用户；针对污纸编码（DPC）的极高复杂度，利用次优的ZF-DPC消除用户间的干扰；在理想信道信息情形下实现可变速率可变功率自适应调制。考虑到最优算法的高复杂度，提出了两种可应用到实际系统的低复杂度次优算法。仿真结果表明，次优算法在极大降低系统复杂度的同时，总速率比较接近最优算法的性能。     

基于改进零树小波的红外图像盲水印算法

提出了一种小波域自适应盲水印算法,采用（7,4）汉明码技术进行纠错编码。基于整数小波变换,在中高频区采用不重复零树小波编码,自适应的量化小波系数,将水印嵌入到重要系数上。水印提取过程不需要原始图像的参与。实验结果表明,算法自适应性强,实现速度快,具有较好的不可见性,对常见的JPEG压缩、滤波、加噪、剪切等攻击具有较强的鲁棒性。     

嵌入式小波图像编码算法的研究

分析了嵌入式零树小波编码（EZW）算法原理和特点。讨论了两个基于EZW算法的改进算法，即多级树集合分裂算法（SPIHT），集合分裂嵌入块编码（SPECK）。最后，对这些算法原理进行了比较和讨论，说明了嵌入式图像编码的研究方向。     

时间分辨力约束下目标检测的波形优化设计

以最大化检测概率为优化准则，采用基于凸优化和随机化方法的具有相似性约束的相位编码算法（Phase Coding Algorithm with Similarity Constrain，PCA-SC）来设计发射波形，解决了主动声呐系统增大探测目标发射功率却不能提高检测概率的问题。同时，为有效降低PCA-SC算法所设计编码自相关函数的整体旁瓣级，提高其检测微弱目标的能力，在PCA-SC算法的基础上，结合新循环算法（Cyclic Algorithm-New，CAN）多相编码技术，提出了基于CAN的PCA-SC波形优化方法（Cyclic algorithm-new Phase Coding Algorithm with Similarity Constrain，CAN-PCA-SC）。仿真实验结果表明，PCA-SC和CAN-PCA-SC两种波形优化方法获得的发射信号均能够在满足系统所需时域分辨能力的要求下，实现检测概率的最大化，提高了目标检测性能，将时域分辨能力和检测性能有效地统一起来。相比PCA-SC波形设计方法，CAN-PCA-SC波形设计方法在保证获得的发射信号的检测概率优化效果一致的情况下，具有更低的积累旁瓣水平和更好的检测微弱目标的能力。     

多环境下卡尔曼滤波多用户算法的性能仿真

盲自适应多用户检测的典型算法主要有:最小均方算法、递归最小二乘算法和卡尔曼滤波算法,而卡尔曼滤波算法的收敛速度快、跟踪性能强,数值稳定性好。本文在同步、异步加性白噪声、用户满载、阵发性强干扰等通信环境下对算法的时间平均信干比(SIR)、平均输出能量(MOE)和误码率(BER)作了仿真测试,对比分析了卡尔曼滤波算法的性能。     

引入支持向量机的小波分数间隔盲均衡算法

针对正交小波变换分数间隔盲均衡算法(FSE-WT-CMA)收敛速度慢且存在局部收敛问题,提出了一种引入支持向量机的正交小波分数间隔盲均衡算法(SVM-FSE-WT-CMA).该算法通过对分数间隔盲均衡器的输入信号进行正交小波变换,以降低信号的自相关性,并且利用支持向量机将盲均衡问题转化为全局最优的支持向量回归问题,采用...     

Increasing capacity of blind mobile system using pre-filtering technique

Increasing mobile system capacity is a hot topic in communication research. A new beamforming technique using a pre-filtering process that decreases noise and interference effects to improve capacity of cellular systems is proposed. Simulation results show significant improvement over the conventional beamforming techniques. The simulation is based on the constant modulus algorithm as a typical blind beamforming technique. This capacity enhancement is achieved with slight increase in computational cost.     

Hardware-assisted initialisation for constant modulus algorithm adaptive antenna

A cost-effective approach for initialisation of an adaptive antenna based on the constant modulus algorithm (CMA) is proposed. The technique utilises 1 bit phase shifters and a power detector, which are normally integrated with a multibeam antenna, to determine the maximum power beam direction. Consequently, the beam is exploited as an initial beam for CMA. Development of hardware-assisted initialisation is discussed. In addition, field programmable gate array implementation of a CMA processor and associated control circuitry is presented. Several simulations are performed to evaluate the performance of the proposed initialisation technique. In addition, the developed prototype is tested with a phase array antenna designed for operation at the IMT2000 frequency of 1.95 GHz. Experimental results confirm superiority of the proposed technique.     

盲均衡算法的发展及其共性思考

引用大量科技文献，阐述了盲均衡算法的发展。从算法的角度，着重介绍了常量模板算法，基于高阶谱的算法，基于神经网络的算法等算法的发展情况，并对其优缺点进行了比较。同时，对各种算法的共性进行了探讨。     

基于信号奇异性分析的轴承故障检测方法

针对轴承振动信号利用小波单奇异点检测无法克服噪声影响的不足,提出利用小波模极大值分析信号奇异性变化进而进行轴承故障检测的方法。实验中对信号的模极大分形指数,模极大分形指数熵,Lipschitz指数以及Lipschitz指数熵等奇异特征进行分析比较,实验结果表明这些特征都能有效克服噪声影响实现故障检测,但模极大曲线数最能体现故障特征且检测效果最好。将该方法同基于小波包能量谱特征和小波单奇异点检测的方法进行比较,结果表明本文建议的方法在检测时间及检测率上都有显著提高。     

Blind adaptive and iterative interference cancellation receiver structures based on the constant modulus criterion in multipath channels

Blind adaptive and iterative interference cancellation (IC) receiver structures for direct sequence code division multiple access systems in multipath channels are proposed. A code-constrained constant modulus design criterion based on constrained optimisation techniques and adaptive algorithms for receiver and channel parameter estimation are described for successive IC (SIC) and parallel IC (PIC) detectors and a new hybrid IC (HIC) scheme in scenarios subject to multipath fading. The proposed HIC structure combines the strengths of linear, SIC and PIC receivers and is shown to outperform the conventional linear, SIC and PIC structures. A novel iterative detection approach that generates different cancellation orders and selects the most likely symbol estimate on the basis of the instantaneous minimum constant modulus criterion is also proposed and combined with the new HIC structure to further enhance performance. Simulation results for an uplink scenario assess the algorithms, the proposed blind adaptive IC detectors against existing receivers and evaluate the effects of error propagation of the new cancellation techniques.     

Various elastic moduli of AA6016 and their application on accurate prediction of springback

First of all, the elastic modulus variation of 6016-T4 aluminum alloy has been investigated by uniaxial tensile experiments. Secondly, a new model to describe the change of elastic modulus has been proposed based on our experimental data. Then Finite Element (FE) simulations with various elastic moduli have been conducted to predict the springback of V bending. The results are shown as follows: the elastic modulus decreases, obviously, with increase of equivalent plastic strain; the proposed model is more suitable to explain our experimental data than the other models considered; and the springback prediction of V bending with various elastic moduli is more precise than with constant modulus.     

Edge preserving filter of side scan sonar images with wavelet modulus maxima shift‐correlative technique

An edge preserving filter algorithm of side scan sonar (SSS) image based on wavelet modulus maxima shift‐correlative (WMMS) technique is proposed in this article. First, the proposed WMMS algorithm decomposes SSS image into multiscale wavelet coefficients. Then the modulus maxima, which are produced by catastrophe points, are extracted from wavelet coefficients. The algorithm matches these maxima across the different scales to identify signal or noise. After correcting the “drifting” phenomenon of modulus maxima, a correlation factor array of wavelet coefficients is constructed by strengthening the maxima dominated by signal and suppressing those maxima dominated by noise. By correlating wavelet coefficients with the correlation factor array, the WMMS strengthens the useful high‐frequency signal and weakens the noise. Finally, the algorithm restores SSS image from revised wavelet coefficients. We apply the WMMS algorithm to filter SSS images of the experimental sea areas. Results show that WMMS has advantages over traditional algorithms in suppressing noise and preserving useful high‐frequency information. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 349–355, 2011     

Reduced complexity detection technique for layered space time block coded multiple-input multiple-output orthogonal frequency division multiplexing

The combination of vertical Bell Labs layered space time (V-BLAST) and space time block coding (STBC), known as a Layered STBC (LSTBC) system, offers high spectral efficiency with a higher order of diversity. The system structure, computational complexity and error performance of the V-BLAST and LSTBC multiple-input multiple-output orthogonal frequency division multiplexing systems are analysed and compared. It is shown that, compared with V-BLAST, the overall diversity order of LSTBC increases two fold. This diversity gain is achieved at the expense of a four?fold increase in the computational complexity of the QR decomposition (QRD) algorithm, required at the receiver of both LSTBC and V-BLAST. The authors propose a modified QRD algorithm which reduces this four-fold complexity to two fold.     

Backcalculation of pavement layer elastic modulus and thickness with measurement errors

This paper presents a backcalculation method for pavement layer elastic modulus and thickness. The effect of deflection measurement errors on the backcalculated results is also considered. The falling weight deflectometer (FWD) data are generated by applying a load to the pavement while calculating deflection at various fixed distances from the load centre. The measurement errors in FWD data are simulated by perturbing the theoretical deflections. Using these data, a backcalculation technique based on the improved genetic algorithm is proposed. In order to deal with the measurement errors, besides the common root mean square, a new objective function called area value with correction factor is introduced to the backcalculation algorithm. Numerical examples for two- and four-layer pavement structures are presented, which show the capability of the proposed method in backcalculation of pavement layer modulus and thickness.