MIMO扩频通信系统矩阵信道估计

为了解决第三代移动通信系统下行链路容量瓶颈问题，在HSDPA的解决方案中，MIMO系统的提案越来越受到重视。本文提出了一种移动深衰落环境下的MIMO系统信道估计方案，并进行了详细的理论推导，给出了独立MIMO深衰落信道环境下的仿真结果。     

一种数字化矿井透地通信系统实现方案

针对矿井通信困难,提出了一种采用扩频技术、可数字化实现的矿井透地通信系统方案,并对该方案进行了理论分析和总体仿真,仿真结果及误码率分析表明了该系统设计方案的可行性,为系统的设计实现奠定了基础。     

DS-CDMA的一种时频二维联合解扩方法

多径环境中传统的DS-CDMA信号接收,一般采用RAKE接收技术.本文提出一种不使用RAKE接收机的DS-CDMA接收算法:基于时频二维扩频的思想,考虑DS-CDMA发射机发射的一个扩频符号对应时间内的信号,在接收机中先将接收到的信号做一个比扩频增益N小的DFT变换,联合对多个DFT变换后的信号进行扩频解扩处理,从而恢复出发射的原始信息比特.本文对比了DS-CDMA传统的RAKE接收算法、基于时频二维扩频的DS-CDMA接收算法(2DSS)、以及Wang等提出的具有信道选择的频域解扩算法的复杂度,并就性能进行了计算机仿真验证.结果表明,在根均方时延较小信道中的性能优于传统RAKE接收算法和具有信道选择的频域解扩算法的性能.     

自适应小波变换的扩频音频数字水印

在分析了自适应小波变换特性的基础上,提出一种基于自适应小波变换的扩频音频数字水印算法.将二值水印图像降维处理转化为一维序列,再将一维序列与m序列做扩频调制,对音频信号进行分段做自适应小波变换,把经过扩频调制的水印信号经过量化处理嵌入到自适应小波变换后的系数中.模拟实验证明,该方法具有较好的不可感知性和鲁棒性.     

直扩信号伪码的盲估计方法的研究

对直接序列扩频通信的信号检测方法进行了综述,重点讨论了自相关域检测方法、四阶累积量方法、谱分析与信号子空间分解法,其中四阶统积量方法和谱分析与信号子空间分解法的最低检测门限远低于相关算法,谱分析与信号子空间分解法在直接序列扩频(DS/SS)信号的伪码周期估计以及伪码序列盲估计中,利用功率谱二次处理结合信号子空间分解的方法可以实现对低信噪比DS/SS信号的估计。     

MIMO Frequency Hopping Spread Spectrum Multi-Carrier Multiple Access: A Novel Uplink System for B3G Cellular Networks

In this paper, we propose and give the performance of a novel uplink system based on the combination of multi-carrier (MC), code division multiple access (CDMA) and multiple input multiple output (MIMO) techniques. First, we describe the interests of spread-spectrum multi-carrier multiple access (SS-MC-MA) scheme for uplink, especially compared to MC-CDMA. Classically, with SS-MC-MA, each user spreads its data symbols on a specific subset of adjacent or multiplexed subcarriers, to facilitate the channel estimation and reduce complexity at the reception. In order to compensate for the lack of frequency diversity of SS-MC-MA with adjacent subcarriers, we first combine it with an orthogonal space-time block code (STBC) and demonstrate the resulting spatial diversity gain. Then, we propose to allocate the subsets to the different users by applying a frequency hopping pattern (FH). In that case, each user benefits from the frequency diversity linked to the total bandwidth as with the multiplexed subcarriers solution, while keeping the advantages of the adjacent subcarriers solution. The gain provided by the use of the frequency hopping is stressed on. Finally, the performance of this scheme is evaluated over realistic MIMO channel with channel turbo coding for systems offering asymptotic spectrum efficiency of 1, 2, 3 and 4.5 bit/s/Hz. Thus, the efficiency of the novel proposed STBC FH SS-MC-MA system as a very promising multiple access and modulation scheme for the uplink of the future wideband wireless networks is successfully demonstrated.     

An advanced monolithic digitalized random carrier frequency spread-spectrum clock generator for EMI suppression

A novel monolithic digitalized random carder frequency modulation spread-spectrum clock generator (RCF-SSCG) is proposed. In this design, the output frequency of the proposed RCF-SSCG changes with the inten-sity of the capacitive charge and discharge current. Its analytical model is induced and the effect of the modulation parameters on the spread spectrum is numerically simulated and discussed. Compared with other works, this design has the advantages of small size, low power consumption and good robustness. The circuit has been fabricated in a 0.5 μmCMOS process and applied to a class D amplifier in which the proposed RCF-SSCG occupies an area of 0.112 mm2and consumes 9 mW. The experimental results confirm the theoretical analyses.     

一种改进的基于二维扩频的WCDMA非Rake接收机

针对WCDMA发射的扩频信号,不同于传统的Rake接收算法,本文采用变换域处理技术,提出了一种充分利用多径能量的二维扩频接收技术。分析了这种充分利用多径能量的二维扩频接收机的算法复杂度。通过计算机仿真,比较了传统的Rake接收算法、充分利用多径能量的二维扩频接收算法的误码率性能。结果表明,在Rake接收机难以精确分辨信道中的每条多径的情况下,使用充分利用多径能量的二维扩频接收机具有更好的误码率性能。     

A Rapid Code Acquisition Scheme for DS/SS Systems

In this paper, we propose a rapid code acquisition scheme for direct-sequence spread-spectrum (DS/SS) system basing on the improved seed accumulation of sequential estimation (ISASE). This method solves the problem that SASE scheme cannot work in the presence of carrier-frequency offset. The mean acquisition time of the ISASE scheme is derived by the generating function flow graph technique, and the tolerance of carrier-frequency offset is obtained in a closed-form expression. The performance of the proposed acquisition scheme is analytically evaluated in terms of the mean acquisition time. Analysis in theory and numerical results show that the proposed scheme yields improvement of the mean acquisition time over the RASE scheme by a factor of 2–15 times for the PN} period more than 255 in normal operating condition. For the important parameter-accumulating number m, we recommend to choose from 5 to 20 through the tradeoff of the tolerance of carrier-frequency offset and acquisition speed. Jiachi Wang was born in September, 1971. He is a Phd candidate in department Electronics and Information Engineering, Huazhong University of Science and Technology. His research areas include spread spectrum and digital communication, and digital signal processing. Xiulin Hu was born in 1945. He is a professor and Phd advisor in department Electronics and Information Engineering, Huazhong University of Science and Technology. His research areas include spread spectrum and digital communication. Yunyu Zhang was born in 1948. She is a professor in department Electronics and Information Engineering, Huazhong University of Science and Technology. Her research areas include software radio and digital communication. Qingyun Dai was born in 1977. She is a Phd candidate in department of Electronics and Information Engineering, Huazhong University of Science and Technology. Her research areas is wireless network.     

划分相位空间的PN码捕获性能分析

频率选择性衰落信道中,接收伪噪声(Pseudo-Noise,PN)码的不确定相位空间中存在多个同相单元。建立检测模型获得了检测过程的检测概率和虚警概率。通过状态转移图结合划分码相位子空间的方法对捕获状态的循环流转进行了描述,获得了捕获性能对信道特性的依赖关系。数值仿真给出了捕获性能随路径数量和接收信噪比等主要参数的变化趋势。