码分多址系统中抗远近效应的多用户盲均衡接收方案

针对码多址系统中多径瑞利衰落信息的远近效应，我们提出了用户盲均衡检测方案，并与多极检测法进行了比较研究，数值模拟表明，多用户盲均衡检测方案的抗远近效应能力优于无信道估计误差的二级检测。     

通信中的自适应技术

本文介绍了自适应技术在通信中的几种典型应用,如自适应消噪、自适应均衡等,讨论了它们的基本原理和系统结构.     

Blind Equalization Using a Novel Recurrent Neural Network Training Algorithm

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An Equalizer and Memory Mapping Predistorter for Nonlinearly Amplified Signals Transmitted by Coded OFDM Systems in Multipath Fading Channel

We present an improved channel equalizing scheme to be used inCoded OFDM systems over an ISI channel. The scheme uses TurboTrellis Coded Modulation (TTCM) which retains a powerful errorcorrection capability while elegantly incorporating turbo codinginto the Trellis Coded Modulation (TCM).In OFDM over wireless communications, M-ary Quadrature AmplitudeModulation (M-QAM) schemes have been widely used to achieve highbandwidth efficiency. However, M-QAM signals require linearamplification to avoid spectral regrowth and severe performancedegradation due to their large envelope fluctuations. Moreover,the OFDM transmitter shapes the signal with a linear pulse shapingfilter. The combination of a linear filter with a High PowerAmplifier (HPA) forms a nonlinear system with memory, whichseverely degrades performance.We propose an efficient one-tap-equalizer using a modified LMSalgorithm and a novel adaptive predistortion technique tocompensate for the nonlinear distortion caused by the high poweramplifier cascaded with a linear filter in TTCM-OFDM systems. Theperformance of this method is compared with methods that have beenused previously with OFDM. A computer simulation confirms that theproposed approach is superior to the conventional methods.     

话带信道自适应均衡器

本文阐述了一种适用于模－数－模加密系统的自适应均衡技术。     

非线性系统自适应逆模理论及算法

本文在对输入过程作可分性的假设下,采用描述非线性系统的Block-oriented模型导出了自适应非线性系统应满足的广义Wiener-Hopf方程。由此出发得到了一类非线性系统的逆模理论解。类似于LMS算法提出了一种自适应逆模的实用算法。计算机模拟试验证实该算法以极高的精度收敛于理论解。     

全数字高阶QAM解调系统的设计

给出了一种适合高阶256QAM的全数字QAM解调方案，提出自适应改变环路带宽的极性判决载波恢复算法以及基于CMA算法和SGA算法的盲均衡算法，并且结合内插滤波器对整个解调系统进行了优化。算法用FPGA实现并成功应用到高阶QAM接收机中。     

Performance of receive diversity and LMMSE chip equalization in WCDMA HSDPA network

More advanced receiver structures than the conventional single antenna Rake can be used to improve the signal-to-noise (SNR) ratios, which is especially beneficial in order to utilize the high bit rates provided by the HSDPA concept in Wideband Code Division Multiple Access (WCDMA) network. In WCDMA system, orthogonal Walsh–Hadamard sequences are used as channelization codes. In frequency-selective fading channels the orthogonality of channelization codes disappears and intra-cell multiple access interference (MAI) arises. In order to mitigate the effect of MAI, chip-level equalization has shown to be a simple and effective solution. The effectiveness of chip equalization, however, degrades at the cell borders where the inter-cell interference dominates rather than MAI. Dual antenna reception is a straight-forward solution to mitigate that performance drop. In this paper, we present an analysis of the expected gains of advanced receivers over conventional single antenna Rake receiver in realistic situations by using a dynamic WCDMA system-level tool. Considered advanced receivers include single and dual antenna Linear Minimum Mean Squared Error (LMMSE) chip-level equalizers and dual antenna Rake receiver. The network performance with advanced receivers is studied also from a more practical point of view by assuming that the penetration of advanced HSDPA terminal receivers is gradually increased in the network.     

Blind equalization in spatial multiplexing MIMO-OFDM systems based on vector CMA and decorrelation criteria

In this paper we address the problem of blind recovery of multiple OFDM data streams in a Multiple-Input Multiple-Output (MIMO) system. We propose an equalization algorithm which is based on a combined criterion designed to cancel both inter-symbol interference (ISI) and co-channel interference (CCI). ISI is minimized by using a modified Vector Constant Modulus criterion while CCI is minimized by a decorrelation criterion. We establish conditions for the existence of the stable minima corresponding to the zero forcing receiver which performs the joint blind equalization and the co-channel signal cancellation. The local convergence properties of the algorithm are proved under the assumption that the balance parameter weighting the two criteria is set appropriately. We also provide the optimal value for this parameter. Reliable performance is achieved with relatively fast convergence and small steady-state error. The implementation of the blind equalizer requires low-computational cost, without any matrix inversions or other expensive operations.     

Iterative Equalization using Improved Block DFE for Synchronous CDMA Systems

Iterative equalization using optimal multiuser detector and optimal channel decoder in coded CDMA systems improves the bit error rate (BER) performance tremendously. However, given large number of users employed in the system over multipath channels causing significant multiple-access interference (MAI) and intersymbol interference (ISI), the optimal multiuser detector is thus prohibitively complex. Therefore, the sub-optimal detectors such as low-complexity linear and non-linear equalizers have to be considered. In this paper, a novel low-complexity block decision feedback equalizer (DFE) is proposed for the synchronous CDMA system. Based on the conventional block DFE, the new method is developed by computing the reliable extrinsic log-likelihood ratio (LLR) using two consecutive received samples rather than one received sample in the literature. At each iteration, the estimated symbols by the equalizer is then saved as a priori information for next iteration. Simulation results demonstrate that the proposed low-complexity block DFE algorithm offers good performance gain over the conventional block DFE.