阵列通道不一致条件下波达方向估计及其校正

现有的基于特征分解类的角度超分辨算法在理想阵列条件下,其估计性能良好,但当信号模型与实际信号环境不匹配,即存在系统误差时,算法的估计性能会严重下降,甚至失效.针对此问题,提出了一种波达方向估计和通道误差校正的新算法,先对各子阵接收信号预处理,使得通道误差对每个子阵的影响一致,这样阵列旋转因子就与通道误差无关,再利用阵列旋转不变性,实现波达方向估计和阵列通道误差的校正.无需校正源,也不需要知道通道误差的先验信息,无需多维搜索寻优和迭代.理论分析和计算机仿真都表明新算法的优越性.     

室内多径环境下降低UWB接收机采样率的Turbo均衡方法

为改善UWB多用户接收机高速采样的困难和由此带来的大量数据的数字化处理,提出一种基于Turbo原理的UWB接收机联合优化方法。该方法首先根据室内信道特点设定均衡器长度,达到多径能量的合理捕获,其二通过计算编码数值自身的软信息,获得迭代所需的对数似然比,用于联合迭代优化均衡器的权值。仿真结果表明,在同样的误码率要求下,可以降低对UWB接收信号采样率的要求。     

Purine and pyrimidine receptors

Adenosine 5′-triphosphate (ATP), in addition to its intracellular roles, acts as an extracellular signalling molecule via a rich array of receptors, which have been cloned and characterised. P1 receptors are selective for adenosine, a breakdown product of ATP, produced after degradation by ectonucleotidases. Four subtypes have been identified, A₁, A_2A, A_2B and A₃ receptors. P2 receptors are activated by purines and some subtypes also by pyrimidines. P2X receptors are ligand-gated ion channel receptors and seven subunits have been identified, which form both homomultimers and heteromultimers. P2Y receptors are G protein-coupled receptors, and eight subtypes have been cloned and characterised to date. Received 22 November 2006; received after revision 11 January 2007; accepted 27 February 2007     

多径衰落分群子载波MIMO-OFDM系统的性能

在分群空时频MIMO-OFDM系统中使用群化分组各子载波策略,将信道估计的导频序列离散于各独立子群中,由空频两域扩展到空时频域,降低系统编解码以及导频序列设计的复杂度,并推导非精确信道信息下分群空时频MIMO-OFDM系统的成对错误概率上界的闭合表达式.理论分析和计算仿真表明,在衰落信道下等间隔的子载波分群策略,可通过减少运算矩阵的规模降低算法复杂度,且具良好的性能.     

浙江省拓展民间资本投资渠道的对策研究

据调查,浙江民间资本数量可观,借贷活跃,地下钱庄发展迅速,民间炒房现象较严重,其危害性应引起有关部门高度重视.为达到引导民间资本的投资流向,疏导其投资渠道,避免投资失误和投资渠道阻塞不畅,减少炒房现象,抑制房地产价格上扬,为解决民营企业资金缺乏等目的,应采取相应的对策.     

Deconvolution techniques for characterizing indoor UWB wireless channel

A deconvolution algorithm is proposed to account for the distortions of impulse shape introduced by propagation process.By finding the best correlation of the received waveform with the multiple templates,the number of multipath components is reduced as the result of eliminating the"phantom paths",and the captured energy increases.Moreover,it needs only a single reference measurement in real measurement environment(do not need the anechoic chamber),which by far simplifies the templates acquiring procedure.     

基于同一训练序列的OFDM系统联合高效算法的研究

针对高速无线数据通信系统中的关键技术——正交频分复用,提出一种高效联合算法,即用同一组训练序列同时实现系统整数倍频偏同步、信道估计和降低峰均比。其主要方法是用训练序列实现系统的整数倍频偏同步和信道估计,同时用训练序列中的数据构成PTS算法的加权系数,以降低峰均比。仿真结果表明,该系统能用同一训练序列同时实现系统同步、信道估计和降低峰均比,与独立实现各功能相比,该算法不仅能够同时实现以上三种功能,而且由于利用一组训练序列,节省了资源,提高了系统的有效性。     

利用时域相关的MIMO-OFDM信道估计算法

提出了一种适用于多入多出正交频分复用(MIMO-OFDM)系统的信道估计算法,详细说明了导频符号的特殊设计算法以及信道估计算法的原理,并对该算法的均方误差性能以及复杂度进行分析;该算法能够在信道多径时延信息准确已知或不准确时带来良好的估计精度,从而保证系统性能。将该算法应用于超三代-时分双工(B3G-TDD)系统中并在室外和室内环境下仿真,均方误差和系统误码率性能结果说明了该算法的有效性;该算法能够大大增强系统的鲁棒性。     

基于随机点过程的IEEE802.15.3a超宽带信道模型研究

基于随机点过程理论分析了IEEE802.15.3a超宽带信道模型,提出了信道模型的数学模型来解决其易于计算机仿真而难于理论分析的问题。得到的数学模型分成四个统计独立的部分,包括一个确定值、两个有限二维泊松过程以及一个有限二维泊松簇生过程。利用该数学模型求出了IEEE802.15.3a信道模型在一定时间窗内到达的平均多径数、平均多径数密度分布以及功率延迟分布,得到了闭合的表达式。表达式的计算结果和计算机仿真结果相吻合,从而验证了该数学模型的有效性。     

Simple, High-Performance Fusion Rule for Censored Decisions in Wireless Sensor Networks

Data selection-based summation fusion （DSSF） was developed to overcome the shortcomings ot previously developed likelihood ratio tests based on channel statistics （LRT-CS） for the problem of fusing censored binary decisions transmitted over Nakagami fading channels in a wireless sensor network （WSN）. The LRT-CS relies on detection probabilities of the local sensors, while the detection probabilities are a priori unknown for uncooperative targets. Also, for Nakagami fading channels, the LRT-CS involves an infinite series, which is cumbersome for real-time application. In contrast, the DSSF only involves data comparisons and additions and does not require the detection probabilities of local sensors. Furthermore, the performance of DSSF is only slightly degraded in comparison with the LRT-CS when the detection probabilities of local sensors are a priori unknown. Therefore, the DSSF should be used in a WSN with limited resources.