多径衰落信道中导引辅助二维扩频的导引功率优化

Analysis and Optimization of Pilot Symbol Assisted Two Dimensional Spread Spectrum Systems in Multi-path Fading Channels

邵士海 唐友喜 戚骥 李少谦 宋立军

在多径衰落信道中，针对BPSK调制的广义二维扩频系统，该文分析了导引符号与数据符号的功率比对导引辅助相干解调的误码率性能的影响，在系统总的发射功率一定的条件下，优化了导引符号与数据符号的功率比。结果表明，分析结果与仿真结果相吻合，导引符号与数据符号功率比的最优值是由多径信道的信噪比、多普勒频移、多径时延、低通滤波器的特性等因素决定的。[著者文摘]

This paper investigates the bit error rate performance influence due to variation of the power of the pilots in pilot symbol assisted BPSK modulated general two-dimensional spread spectrum systems in Rayleigh fading propagation environments. Under the circumstance, that the system＇s total transmitting power is fixed, the pilot to data power ratio is optimized analytically. Simulation results accord with theoretical conclusions, both of which illuminate that the optimum pilot to data power ratio is determined by the parameters of multipath fading channels such as SNR, Doppler frequency and multipath delay. The characteristic of low pass filter also affects the optimum pilot to data power ratio.[著者文摘]

一种鲁棒的三维运动盲水印检测算法

史烈[1] 叶绿[2] 黄向军[1] 潘志庚[1]

为了对动画序列进行有效的版权保护,提出了一种新的具有抗攻击性的三维运动盲水印算法。算法包括水印嵌入和水印检测两部分,在嵌入过程中,该算法通过Hash变换得到随机数种子,用于伪随机信号的生成,同时对原始运动信号进行离散余弦变换(DCT),把生成的伪随机信号和DCT变换结果叠加进行水印嵌入。在检测过程中,根据对DCT变换系数统计分布的分析,该算法采用符号相关性检测算子来判断水印是否存在。实验结果表明,该算法对Gauss白噪声、重采样、运动光滑、重排列和二次水印等攻击操作有很好的鲁棒性。

基于时频联合估计的短波OFDM的检测算法

阚春荣[1] 王庭昌[2]

针对短波信道的特点，该文提出了一种OFDM同步检测方案。方案采用m序列调制导频符号，利用时频偏移联合估计得到m序列的相关峰来实现同步检测。该文理论分析了方案中判决门限区间的选取。蒙特卡罗仿真表明，该方案在低信噪比(-10dB)下性能良好，有可靠的同步概率和小的虚警概率。

一种新型结构的高速时钟数据恢复电路

A New Architecture High Specd Clock and Data Recovery Circuit

叶国敬 孙曼 郭淦 洪志良

针对高速（Gb／s）串行数据通信应用，提出了一种混合结构的高速时钟数据恢复电路．该电路结构结合鉴频器和半速率二进制鉴相器，实现了频率锁定环路和相位恢复环路的同时工作．电路采用1．8v，0．18μm、CMOS工艺流片验证，面积约0．5mm^2，测试结果显示在2Gb／s伪随机数序列输入情况下，电路能正确恢复出时钟和数据，核心功耗约为53．6mW，输出驱动电路功耗约64．5mW，恢复出的时钟抖动峰峰值为45ps，均方根抖动为9．636ps．[著者文摘]

A new hybrid high speed clock and data recovery circuit suitable for the application in Giga bit/s serial data communication is presented. By adopting a frequency detector in parallel with a half-rate bang-bang phase detector, cooperation of the frequency locked loop and the phase locked loop is realized. Implement in a 1.8 V 0.18/an 1P6M standard CMOS process, the area of the circuit is 0.5 mm^2. Test results show that, with a 2 Gb/s PRBS input, the system can recover the data and clock correctly, the core power dissipation is 53.6 mW, the output buffer consumes 64.5 mW. The recovered clock has a 9. 636 ps and 45 ps RMS jitter and peak-peak jitter respectively.[著者文摘]

多径衰落下多天线CDMA系统信道容量研究

Capacity of Multi-antenna CDMA System under Multipath Fading Channels

王军选 饶文元 李道本

该文对准静态Rayleigh衰落下MIMO-CDMA系统信道容量进行了研究，分析了扩频码为Walsh函数，基于多码检测的极大似然检测器（MLD）和解相关检测器的性能。并和MMSE多用户检洲器（MUD）进行了比较；分析了对不同检测器在一定的信噪比下系统天线数目和信道容量的关系。仿真结果表明；在相同的情况下，基于Walsh码CDMA系统容量按MUD、干扰方差已知的MLD，干扰方差未知的MLD和解相关检测器递减，并且后面的3种检测器在大信噪比的时候均有渐进的平台效应；在信噪比较大且一定时，CDMA系统信道容量与天线数目呈线性关系。[著者文摘]

The performance of Maximum Likelihood Detector （MLD）, decorrelating detector which based on multi-code detections and MMSE Multi-User Detector（MUD） of MIMO CDMA system under Rayleigh fading channels were analyzed in the paper. The relation between the number of antennas and system capacity at a given SNR was also analyzed. The numerical results present that the capacity is degressive for MMSE MUD, MLD with interference covariance known, MLD with interference covariance unknown, and decorrelating detector, furthermore the three latter detectors all have platform as SNR is large; at a given SNR, the relation of system capacity and the number of antenna is linear for a N× N system.[著者文摘]