基于社团结构的容迟传感器网络多副本数据传输策略研究

在社团结构网络模型下,建立社团间多副本数据转发策略的传输概率模型,提出一种基于社团结构的多副本数据传输(CMDD)策略。CMDD策略动态计算社团间移动节点的平均相遇间隔时间,并根据传输概率模型估算借助该社团分发副本可获得的成功传输概率。模拟实验表明,CMDD策略能以较低的传输延迟和较低的传输开销获得较高的数据传输成功率。     

Statistical clock skew modeling with data delay variations

Accurate clock skew budgets are important for microprocessor designers to avoid hold-time failures and to properly allocate resources when optimizing global and local paths. Many published clock skew budgets neglect voltage jitter and process variation, which are becoming dominant factors in otherwise balanced H-trees. However, worst-case process variation assumptions are severely pessimistic. This paper describes the major sources of clock skew in a microprocessor using a modified H-tree and applies the model to a second-generation Itanium-M processor family microprocessor currently under design. Monte Carlo simulation is used to develop statistical clock skew budgets for setup and hold time constraints in a four-level skew hierarchy. Voltage jitter through the phase locked loop (PLL) and clock buffers accounts for the majority of skew budgets. We show that taking into account the number of nearly critical paths between clocked elements at each level of the skew hierarchy and variations in the data delays of these paths reduces the difference between global and local skew budgets by more than a factor of two. Another insight is that data path delay variability limits the potential cycle-time benefits of active deskew circuits because the paths with the worst skew are unlikely to also be the paths with the longest data delays     

Neural network modeling of reactive ion etching using optical emission spectroscopy data

Neural networks are employed to model reactive ion etching (RIE) using optical emission spectroscopy (OES) data. While OES is an excellent tool for monitoring plasma emission intensity, a primary issue with its use is the large dimensionality of the spectroscopic data. To alleviate this concern, principal component analysis (PCA) and autoencoder neural networks (AENNs) are implemented as mechanisms for feature extraction to reduce the dimensionality of the OES data. OES data are generated from a 2/sup 4/ factorial experiment designed to characterize RIE process variation during the etching of benzocyclobutene (BCB) in a SF/sub 6//O/sub 2/ plasma, with controllable input factors consisting of the two gas flows, RF power, and chamber pressure. The OES data, consisting of 226 wavelengths sampled every 20 s, are compressed into five principal components using PCA and seven features using AENNs. Each method is subsequently used to establish multilayer perceptron neural networks trained using error back-propagation to model etch rate, uniformity, selectivity, and anisotropy. The neural network models of the etch responses using both methods show excellent agreement, with root-mean-squared errors as low as 0.215% between model predictions and measured data.     

延迟容忍传感器网络中基于移动协助的数据传输

提出了基于移动协助的动态数据传输算法(MAD, movement-assisted adaptive data delivery)。在缓冲区域内设置数据缓存节点,让基站在缓冲区内周期性地移动,数据动态地复制给更有可能到达缓冲区并且剩余能量较高的节点,然后基站在移动中将缓存节点中的数据进行收集。MAD是由数据传输和队列管理2部分组成。前者根据节点的运动趋势和剩余能量计算节点的转发概率,后者通过消息的生存时间和消息的最大复制数确定队列中消息发送的优先级及丢弃方法。仿真结果表明,与其他策略相比,MAD在传输成功率和网络寿命方面具有更好的性能。     

Performance modeling of data transmission by using random linear network coding in DTNs

In Delay Tolerant Networks (DTNs), mobile nodes exploit encounter chances to transmit data via the established opportunistic link between encounter nodes. The transmission capacity between two encounter nodes is constrained by the duration of opportunistic links. How to transmit data efficiently is one of the fundamental and most important issues in DTNs. Recently, Random Linear Network Coding (RLNC) is proposed as a promising approach to improve data transmission efficiency in DTNs. To facilitate the development of deployment of RLNC based routing protocols, it is imperative to quantify the performance gain brought by RLNC in a rigorous and systematic way. In this paper, we develop an analytical model to evaluate the data transmission performance of RLNC based epidemic routing in DTNs. In the model, we consider that multiple unicast communication sessions compete for limited \capacity. Numerical results validate the effectiveness of our analytical model and demonstrate the significant performance improvement for data transmission in DTNs brought by RLNC. Our work of this paper provides a general tool for performance evaluation and useful guidelines for designing RLNC based routing protocols in DTNs. Copyright © 2015 John Wiley & Sons, Ltd.     

基于运动状态的延迟容忍移动传感器网络数据传输策略

针对延迟容忍移动传感器网络(DTMSN, delay tolerant mobile sensor networks)提出一种基于节点运动状态的数据传输(MSD, motion state-based delivery)策略.MSD使用2个通信频率,传感器节点利用基站在频率f1上的广播信号完成自身运动状态和传输概率的计算,并以此作为利用频率f2进行消息转发的依据.为了提高性能,MSD中利用消息生存时间和自身消息优先传输机制来完成消息队列的管理.仿真结果表明,与现有的几种DTMSN数据传输策略相比,MSD能够以较低的通信开销和传输延迟达到较高的数据传输成功率.     

网络数据波动控制器设计与建模

传统的网络数据波动控制器往往运算量大、操作复杂,造成控制器自身对网络非波动数据持有时间过短、通信误差偏大等缺陷。为此,设计一种更加智能化、实用化的网络数据波动控制器。所设计的控制器通过构建网络数据波动控制模型,给出网络数据波动的最优控制方案,并使用AT91SAM9260微处理器对其进行提取。AT91SAM9260微处理器将最优控制方案插入到网络初始数据的相应节点中,对数据波动小、干扰参数少的网络进行聚集控制,对相反类型的网络进行分布控制。实验结果证明,所设计的控制器对非波动数据的持有时间较长,并具有极小的通信误差,与传统控制器相比,其性能更加优异、应用领域更为广泛。     

The use of network delay estimation for multimedia data retrieval

Multimedia data have specific temporal presentation requirements. For example in video conferencing applications the voice and images of the participants must be delivered and presented synchronously. These requirements can be achieved by scheduling or managing system resources. We present a technique called limited a priori scheduling (LAP) to manage the delivery channel from source to destination for digital multimedia data. By using delay estimation a LAP scheduler can retrieve stored digital media spanning arbitrary networks with unspecified delays. The use of delay estimation also facilitates selective degradation of service in bandwidth and buffer limited situations. Such degradation enables the continuous real-time playout and synchronization of various media arriving from different sources. The performance of the LAP scheduler is described based on implementation and experimentation using Ethernet     

Mobile ad hoc network proactive routing with delay prediction using neural network

Existing MANET routing protocols rely heavily on hop count evaluation. Although this is simple and efficient, it sacrifices the potential performance gains obtainable by considering other dynamic routing metrics. In this paper, we propose a delay prediction mechanism and its integration with a MANET proactive routing protocol. We demonstrate our approach of predicting mean queuing delay as a nonstationary time series using appropriate neural network models: Multi-Layer Perceptron or Radial Basis Function. To support MANET proactive routing, our delay prediction mechanism is devised as a distributed, independent, and continuous neural network training and prediction process conducted on individual nodes. We integrated our delay prediction mechanism with a well-known MANET proactive routing protocol—OLSR. The essential part of this integration is our TierUp algorithm, which is a novel node-state routing table computation algorithm. The structure and the key parameters of the resulting extended OLSR, called OLSR_NN, are also discussed. Our simulation shows that because of its capability of balancing the traffic, OLSR_NN is able to increase data packet delivery ratio and reduce average end-to-end delay in scenarios with complex traffic patterns and wide range of node mobility, compared to OLSR.     

FPGA-implementation of dynamic time delay neural network for power amplifier behavioral modeling

In this paper, we propose new architectures for FPGA-implementation of a dynamic neural network power amplifier behavioral modeling. The real-valued time-delay neural network (RVTDNN) and the backpropagation (BP) learning algorithm were implemented on FPGA using Xilinx system generator for DSP and the Virtex-6 FPGA ML605 evaluation kit. Different RVTDNN architectures are proposed for various values of the number of hidden neurons, the activation function resolution, and the fixed-point data format. These architectures are evaluated and compared in terms of modeling performances and resource utilization using 16-QAM modulated test signal.     

最大熵原理在网络延迟测量数据处理中的应用

在计算机软件时钟同步系统中,针对网络延迟测量数据处理中掺杂的主观因素不能准确反映客观现实的问题.采用最大熵方法,根据已有的测量数据求取被测量的概率分布,进而对此概率分布在约束条件下进行估计和评价.测量数据源自网络延迟测量产生的对数正态分布测量数据样本,计算测量结果用MATLAB编程做出仿真图形.仿真结果与计算结果表明:...     

DTN分发网络中基于数据投递概率的拥塞控制机制

针对DTN网络数据编码分发过程中数据拥塞造成投递性能下降的问题,提出了一种基于主题数据投递概率的节点拥塞控制机制(CCM-DP)。综合考虑节点移动模型、主题包投递概率、节点拥塞程度等因素建立数据投递概率模型,从两方面进行拥塞控制,一方面基于数据投递概率动态调节数据分组转发过程,避免节点因收取过多的数据分组造成拥塞,另一方面,通过设计合理的丢弃策略,降低因拥塞造成数据分组丢失产生的影响。最后,将该拥塞控制机制应用在数据分发过程中进行了仿真分析,结果表明,该方法能提升数据拥塞情况下的数据投递性能。     

Nonlinear dynamic system modeling using recurrent wavelet network

A recurrent wavelet network for the dynamic system nonparametric modeling is proposed in this paper. It is noted that the suitable recurrent units are introduced so that the dynamics of the wavelet network has been greatly improved. The recurrent backpropagation identification algorithm is also given. The simulation results show that regress system model with large-dimension can be better constructed and the useful guidelines for initialization of the network parameter are also provided with recurrent wavelet network identification.     

Leaky delayed LMS algorithm: stochastic analysis for Gaussian data and delay modeling error

This paper presents a stochastic analysis of the delayed least-mean-square (DLMS) adaptive algorithm with leakage. This analysis is obtained taking into account that mismatches between the system delay and its estimate may occur. Such an approach is not considered in previous models. In addition, it is shown that the introduction of a leakage factor into the adaptive algorithm keeps the adaptive algorithm stable under an imperfect delay estimate condition. Recursive difference equations for the first and second moments of the adaptive filter weights are derived. An expression for the critical value of the step size is also determined. Results of Monte Carlo simulations present excellent agreement with the proposed model for both white and colored Gaussian inputs.     

Multimedia data broadcasting strategies

Data broadcasting in support of multimedia applications requires efficient use of bandwidth resources in order to maximize the availability of playout content. A broadcast architecture has been specified by the Digital Video Broadcasting consortium to allow service providers to multiplex data, using various protocols, into an MPEG-2 transport stream. This architecture, however, has not specified how to optimize the use of the broadcast channel. This article discusses certain strategies, based on test and measurement, that have been implemented to maximize the use of the broadcast channel (satellite and cable) for supporting multimedia applications     

Resource-efficient delivery of on-demand streaming data using UEP codes

We propose and analyze a new multicast scheme for delivering on-demand streaming data using unequal protection codes. The scheme allows an end user to join only one multicast channel for a data stream at any time to play out the requested data stream from its beginning after a fixed initial playout delay. The scheme tolerates packet loss during transmission, and thus, significantly reduces the cost of implementing a reliable multicast network layer to ensure delivery of all packets. Meanwhile, resource usage of the scheme, including server computing bandwidth, network bandwidth, and client's buffer space, is determined only by the original data stream length and the initial playout delay, but is independent of either the number or the arrival pattern of individual end-user requests. Thus, the scheme is totally scalable with the number of end users, fully utilizing the data delivery efficiency of a multicast network. The scheme also uses resources efficiently, e.g., with an initial playout delays of 30 s and 60 s, multicasting a 2 h video using this scheme needs only about 5.5 and 4.8 times, respectively, the server computing bandwidth and network bandwidth of those for a single unicast delivery of the same original data stream.     

有线电视网络中的多媒体通信

介绍了多媒体通信的发展前景和多媒体通信网络，并探讨了在有线电视网络上实现多媒体通信的问题。