APSK长突发信号的动态载波相位跟踪

APSK已被用于宽带数字卫星通信,在采用APSK长突发的卫星通信中,需要对一帧内的载波相位动态变化进行跟踪。针对粗载波同步和符号同步完成后的长突发APSK调制信号,提出一种新的载波跟踪方案,该方案采用一种基于星座分割的NDA鉴相算法,使用两个二阶锁相环,并借助于一个很短的独特码解相位模糊,可在很高的数据传输效率下,克服一般闭环法的捕获时间问题,实现对整帧信号载波相位的顺利跟踪。

PON突发式长发光ONU的防护与检测

PON(无源光网络)中突发式长发光干扰是异常上行光信号干扰的一种,由于其故障发生的随机性以及持续时间的瞬间性,使得故障难以定位。文章针对PON ONU(光网络单元)突发干扰问题,描述了突发长发光的几种表现与可能原因,总结了典型的防护方法,并对比了几种方法的优缺点;对定位故障ONU的方法进行了探讨,给出了彻底消除故障的方法。

长程突发通信量的分数自回归预测

以数据包传输的通信量在不同网络条件下均表现出自相似性,自相似通信量在各时间尺度上均具有长程突发特性,其是以泊松过程为模型所描述的短程相关通信量所无法描述的。近来对自相似通信量的高精度测量与研究证实:网络中广泛存在的重尾特性是通信量自相似产生的原因。同时充分提取通信量的自相似性与重尾特性相关信息,是准确预测长程突发通信量的关键。在一种α-基于平稳过程的自相似通信量模型基础上,提出两种独立的自回归预测方法:FAR(Fractional Auto Regressive)预测、FNAR(Fractional Nonlienar Auto Regressive)预测。对这两种预测值进行不同方案的混合预测得到最终预测结果,进一步提高预测精度。

双选信道下一种基于混沌交织的FBMC系统

高速移动环境下,无线信道具有时频双选性衰落的特性,使得滤波器组多载波(Filter Bank Multi-carrier,FBMC)系统产生长突发差错。将一种基于Baker映射的混沌交织算法应用在滤波器组多载波系统中,根据混沌密钥对发送数据进行分块和重新排列,按照Baker映射规则完成数据交织。此方法可以将长突发差错变为单突发差错,结合卷积编码能有效地纠正双选信道产生的长突发差错。仿真结果表明,在双选择信道中,基于混沌交织的滤波器组多载波系统误比特率性能优于传统基于块交织的滤波器组多载波系统。

移动信道Markov模型的Stateflow仿真技术

针对具有长突发误码特性的无线信道特征,根据移动通信系统的仿真要求,基于简单分群马尔科夫(Markov)信道模型,提出了利用stateflow技术的信道仿真方法,并生成移动信道的差错序列。仿真结果表明,该信道模型能够有效地描述无线移动信道的统计特性,并具有可视化、流程化和层次化的特点,在无线移动通信系统的软件仿真中具有实用性。

Performance analysis of optical burst switching node with limited wavelength conversion capabilities

The systematical and scalable frameworks were provided for estimating the blocking probabilities under asynchronous traffic in optical burst switching(OBS) nodes with limited wavelength conversion capability(LWCC) . The relevant system architectures of limited range and limited number of wavelength converters(WCs) deployed by a share-per-fiber(SPF) mode were developed,and the novel theoretical analysis of node blocking probability was derived by combining the calculation of discouraged arrival rate in a birth-death process and two-dimensional Markov chain model of SPF. The simulation results on single node performance verify the accuracy and effectiveness of the analysis models. Under most scenarios,it is difficult to distinguish the plots generated by the analysis and simulation. As the conversion degree increases,the accuracy of the analysis model worsens slightly. However,the utmost error on burst loss probability is far less than one order of magnitude and hence,still allows for an accurate estimate. Some results are of actual significance to the construction of next-generation commercial OBS backbones.

Implementation of Efficient Burst Assembly Algorithm with Traffic Prediction

This paper reports on the implementation of efficient burst assembly algorithms and traffic prediction. The ultimate goal is to propose a new burst assembly algorithm which is based on time-burst length （hybrid） threshold with traffic prediction to reduce burst assembly delay in OBS （Optical Burst Switching） networks. Research has shown that traffic always change from time to time, hence, any measure that is put in place should be able to adapt to such changes. With our implemented burst assembly algorithm, the traffic rate is predicted and the predicted rate is used to dynamically adjust the burst assembly length. This work further investigates the impact of the proposed algorithm on traffic self similarity.

A novel wavelength assignment scheme in OBS network for contention avoidance

Conventional optical burst switching(OBS)technique adopts purely statistical multiplex mechanismso that the bursts collide with each other very easily.To address this problem,a novel proactive con-tention avoidance scheme is proposed,which assigns dedicated wavelengths to each ingress node,then st-numbering algorithm is used to construct the traffic load balanced spanning trees .In this way,contentioncan be eliminated at ingress nodes,and the amount of bursts that could be accommodated by ingressnodes will be maximized.Further,those unused wavelengths left by traffic load balanced spanning treeare also organized as partial trees to carry bursts,thus the link utilization can be improved effectively.Simulation result shows that our scheme can improve the burst loss performance significantly without thewavelength converters or optical buffers comparing to other popular routing and wavelength assignment(RWA)algorithms.

A burst segmentation-deflection routing contention resolution mechanism in OBS networks

One of the key problems to hinder the realization of optical burst switching(OBS) technology in the core networks is the losses due to the contention among the bursts at the core nodes.Burst segmentation is an effective contention resolution technique used to reduce the number of packets lost due to the burst losses.In our work,a burst segmentation-deflection routing contention resolution mechanism in OBS networks is proposed.When the contention occurs,the bursts are segmented according to the lowest packet loss probability of networks firstly,and then the segmented burst is deflected on the optimum routing.An analytical model is proposed to evaluate the contention resolution mechanism.Simulation results show that high-priority bursts have significantly lower packet loss probability and transmission delay than the low-priority.And the performance of the burst lengths,in which the number of segments per burst distributes geometrically,is more effective than that of the deterministically distributed burst lengths.

A bacterial artificial chromosome transgenic mouse model for visualization of neurite growth

Class Ⅲ β-tubulin （Tubb3） is a component of the microtubules in neurons and contributes to microtubule dynamics that are required for axon outgrowth and guidance during neuronal development. We here report a novel bacterial artificial chromosome （BAC） transgenic mouse line that expresses Class Ⅲ β-tubulin fused to mCherry, an improved monomeric red fluorescent protein, for the visualization of microtubules during neuronal development. A BAC containing Tubb3 gene was modified by insertion of mCherry complementary DNA downstream of Tubb3 coding sequence via homologous recombination, mCherry fusion protein was expressed in the nervous system and testis of the transgenic animal, and the fluorescent signal was observed in the neurons that located in the olfactory bulb, cerebral cortex, hippocampal formation, cerebellum, as well as the retina. Besides, Tubb3-mCherry fusion protein mainly distributed in neurites and colocalized with endogenous Class Ⅲ β-tubulin The fusion protein labels Purkinje cell dendrites during cerebellar circuit formation. Therefore, this transgenic line might be a novel tool for scientific community to study neuronal development both in vitro and in vivo.