Visual language and graph-based structures in conceptual design

The paper deals with using design knowledge encoded in a visual language and graph-based structures to support the conceptual phase of designing. The visual language is based on the design conceptualization and composed of design diagrams being configurations of geometric primitives. A symbolic representation of design structures in terms of objects specified by the conceptualization and relations between them is defined, and then mapped into diagrams by a given realization. Diagrams are automatically transformed into the corresponding graph-based data structures. The knowledge stored in the graph representations of diagrams is translated into first-order logic formulas which describe generated design configurations. A proposed logic-based reasoning mechanism allows the design supporting system to check the compatibility of designs with the given requirements and constraints. The approach is illustrated by examples of designing configurations of transmission truss towers.     

Mean square detectability of LTI systems over finite-state digital block-fading channels

This paper studies the mean square quadratic (MSQ) detectability for multi-output networked systems over finite-state digital block-fading channels. The packet-loss rate of each digital fading channel depends on the channel power gain, as well as packet length and power level used for transmission. A finite-state random process is introduced to model time-varying fading channels, which characterizes various configurations of physical communication environment and/or different channel fading amplitudes. Necessary and sufficient conditions for MSQ detectability over finite-state Markov digital block-fading channels are given in the form of algebraic Riccati equations or linear matrix inequalities (LMIs). The estimation gain is given as a function of estimated/observed channel state. In addition, explicit conditions on network for MSQ detectability over finite-state independent identically distributed (i.i.d.) digital block-fading channels are presented in terms of the unstable poles of the multi-output plant. Finally, an application to Gilbert-Elliott channels (GECs) is provided to demonstrate the derived results.     

基于乱序反馈的差异化多路径并发传输模型数据分配算法

多路径并发传输模型在差异化路径中会出现严重的数据包乱序现象,导致接收端缓冲区阻塞,极大地降低了偶联的整体传输性能。在分析影响路径传输性能因素的基础上,给出了差异化路径性能评估模型,并提出了一种基于乱序反馈的差异化路径并发传输数据分配算法。该算法以乱序反馈来动态调节路径的发送比例,减少了传输性能差的路径对整体吞吐量的影响。分析和实现结果表明,本算法的性能比默认的轮询数据分配算法更好。     

Confidentiality considerations: multimedia signals transmission over different wireless channels utilized efficient secured model

The confidentiality of highly-sensitive multimedia signals is considered in this paper, it can be enhanced by efficient secured model utilizing several-layer security algorithms. The hybrid data hiding and cryptographic techniques are merged for constructing secured model. The Least Significant Bit (LSB) data hiding steganography is utilized with a 2-D Logistic-based map (Model-I) and second Model-II involves data hiding merging within chaotic-Baker-based image encryption security techniques. ?Performance analyzing and comparison have been presented utilizing various images for examining the applicability of the different proposed image security scenarios for securing wireless image transmission over noise-free, and noisy channels. Moreover, the proposed algorithms are applied for transmission over Orthogonal Frequency-Division Multiplexing (OFDM) channels, and their performance is evaluated under different conditions of fading environments with utilizing the powerful error control schemes in the case of SUI-3 model channel and randomizing the packet based on the encryption tools. An equalizer is used to mitigate the impact of composite fading. A multi-layer security model using Discrete Wavelet Transform (DWT) steganography with chaotic Baker encryption is proposed to protect highly-sensitive text based data records. The results reveal that it can be used efficiently for protecting highly-sensitive text message and records (text-based data). The timing analysis and comparative study are considered with respect to the previous related works.

     

Admission control by implicit signaling in support of voice over IP over ADSL

Voice over DSL (VoDSL) is a technology that enables the transport of data and multiple voice calls over a single copper-pair. Voice over ATM (VoATM) and Voice over IP (VoIP) are the two main alternatives for carrying voice over DSL. ATM is currently the preferred technology, since it offers the advantage of ATM’s built-in Quality of Service (QoS) mechanisms. IP QoS mechanisms have been maturing only in recent years. However, if VoIP can achieve comparable performance to that of VoATM in the access networks, it would facilitate end-to-end IP telephony and could result in major cost savings. In this paper, we propose a VoIP-based VoDSL architecture that provides QoS guarantees comparable to those offered by ATM in the DSL access network. Our QoS architecture supports Premium and Regular service categories for voice traffic and the Best-Effort service category for data traffic. The Weighted Fair Queuing algorithm is used to schedule voice and data packets for transmission over the bottleneck link. Fragmentation of large data packets reduces the waiting time for voice packets in the link. We also propose a new admission control mechanism called Admission Control by Implicit Signaling. This mechanism takes advantage of application layer signaling by mapping it to the IP header. We evaluate the performance of our QoS architecture by means of a simulation study. Our results show that our VoIP architecture can provide QoS comparable to that provided by the VoATM architecture.     

CATV over IP 网关系统的设计

提出一种基于用户驻地网接入有线电视的CATV overIP网关系统;叙述了模拟有线电视射频信号的MPEG-2编码压缩和封组播包发送,叙述了数字有线电视射频信号的条件接收、再复用和封组播包发送;给出了系统的硬件组成与各模块功能及系统的实现.     

一种CDMA2000链路层自适应重传算法

TCP协议应用在3G无线网络中时，其传输性能受到了无线网络物理层帧差错率的严重影响。链路层重传技术可以大大改善TCP数据传输性能因无线信道误码率大而下降的情况。主要研究了CDMA2000中链路层重传技术对无线TCP数据传输的影响，并结合TCP层重传超时机制，提出了一种新的自适应链路层重传算法，提高了TCP在无线链路的数据传输性能。最后对该算法进行仿真，验证了此算法可以显著提高TCP吞吐率。     

Improvements and analysis of nonlinear parallel behavioral models

This article performs an analysis of current limitations regarding the extraction of parallel behavioral models to reproduce the power amplifier (PA) nonlinear behavior and its dynamics. To overcome these limitations, a general preprocessing block that clearly improves the identification capabilities shown by classical parallel structures is proposed. It follows the principle of separating both static and dynamic nonlinear behavior of the PA to obtain a better identification performance. A comparison with common parallel configurations using linear estimation is performed, to highlight the benefits of using the preprocessing structure. Furthermore, a new nonlinear parallel structure using sub‐band filtering techniques is also proposed. For the models extraction and comparison, four types of noise‐free simulated data presenting different levels of nonlinearities and memory, as well as a measured signal obtained from a laboratory amplifier have been considered. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

CDMA2000无线网络中的视频数据传输

实时视频业务将是3G无线网络中最主要的无线宽带应用业务之一。文章在分析视频数据在CDMA2000无线网络中的传输机制的基础上,重点研究CDMA2000链路层重传技术对视频数据传输的影响,并通过OPNET仿真平台及相应的视频编解码实现进行仿真,分析比较了无线信道各种帧差错率条件下不同重传方案对视频实时数据传输的性能影响,表明链路层重传在一定程度上能改善CDMA2000无线网络中的视频传输效果。     

低功耗射频微系统时钟动态切换方法

为满足射频微系统芯片的降低功耗要求,使国产射频微系统能够得到更为广泛的应用,提出了一种考虑低功耗的射频微系统时钟动态切换管理方法.考虑芯片功耗设计问题,利用局部位置的系统时钟的自适应动态切换,对芯片运行切入点进行了设计;基于数字时钟对射频微系统的处理加速单元进行晶振替换,并对芯片时钟进行动态自适应调整,降低了芯片运行功耗;仿真分析表明:相对于实测数据,所提方法在芯片运行功耗上具有更优异的表现.     

Coupling between transmission‐line networks and homogeneous media: A semianalytical approach

Electromagnetic devices that incorporate volumetric networks of transmission lines with electrically small periodicity and cross‐sections are extensively used in various applications. Linear tapers can be employed in these configurations to achieve coupling between a homogeneous background medium and the volumetric transmission‐line structure. This is beneficial since various transmission‐line structures (homogenizable dense networks of transmission lines) are widely utilized to realize exotic electromagnetic properties commonly related to metamaterials. However, optimizing the dimensions of such multiparametric and electrically large devices could be computationally cumbersome. In this work, a simple semianalytic technique is proposed to reduce substantially the required simulation cost for an optimized design. The tapers are modeled semianalytically as consecutive coplanar components. On the other hand, the transmission‐line network is considered as a chain of identical unit cells, the response of which is numerically determined. The semianalytical result of the taper is combined with the numerical result of the unit cell by cascading the respective transfer matrices. The agreement of the obtained results with the corresponding full‐wave simulation data of the whole structure is very good. The decreased computational time required for the proposed approach is demonstrated through several numerical examples. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013     

MISO OFDM链路中的IDM空时编码

在链路级别上,分析研究了采用交织复用(IDM)空时编码的多进单出(MISO)正交频分多址(OFDM)系统.介绍了一种达代接收机结构,并在准静态信道条件下通过仿真对其性能进行评估.结果表明,在相似环境下与采用其它空时码的系统比较,采用交织复用空时编码的系统在性能上具有一定的优越性.     

Proposed future Internet

The performance and reliability of a proposed future Internet—wired and wireless—is compared with the present Internet. Models of data transfer and queuing dynamics are used to make the performance comparison. These models consist of logic diagrams that express the sequence of data transfers in the Internet (e.g., local network to local network router) and queuing logic diagrams, supported by queuing equations (e.g., probability of local network queue busy). These models represent the steady state behavior of the present and proposed future Internets. C++ programs are used to simulate the variability in queue behavior. The results are used to identify the major variables in Internet performance (e.g., Internet routing time as a major performance variable). Furthermore, the results are used to compare present Internet and proposed future Internet performance. Reliability analysis is performed by predicting cumulative Internet faults and failures and by analyzing the complexity of present and proposed Internet configurations as an indicator of reliability (i.e., number of points of failure in a configuration). Model results demonstrate significant increases in performance and reliability for the proposed Internet, attributed to the elimination of data transfer overhead (e.g., elimination of Domain Name Service) and simplified network configurations.     

Robust image and video transmission over spectrally shaped channelsusing multicarrier modulation

This paper presents a new parallel transmission framework for reliable multimedia data transmission over spectrally shaped channels using multicarrier modulation. We propose to transmit source data layers of different perceptual importance in parallel, each occupying a number of subchannels. New loading algorithms are developed to efficiently allocate the available resources, e.g., transmitted power and bit rate, to the subchannels according to the source layers they transmit. Instead of making the bit error rate of all the subchannels equal as in most existing loading algorithms, the proposed algorithm assigns different error performance to the subchannels to achieve unequal error protection for different layers. The channel induced distortion in mean-square sense is minimized. We show that the proposed system can be applied nicely to both fixed length coding and variable-length coding. Asymptotic gains with respect to channel distortion are also derived. Numerical examples show that the proposed algorithm achieves significant performance improvement compared to the existing work, especially for spectrally shaped channels commonly used in in ADSL systems     

High isolation microstrip GaN‐HEMT Single‐FET Switch

In this contribution an analytical approach to the design of high‐isolation microwave transmission line‐resonated switches is presented. Simulated and measured performance of a GaN HEMT single‐FET switch cell topology and the one of a complete SPDT using the proposed approach are presented to demonstrate the approach feasibility and effectiveness. The resulting SPDT, operating at X Band, is featured by 1 dB insertion loss, isolation better than 37 dB all over the operating bandwidth and a power handling capability higher than 39 dBm. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Adaptive unequal protection for wireless video transmission over IEEE 802.11e networks

Packet loss of video streams cannot be avoided at wireless links for limited wireless bandwidth and frequently changed environments. To provide differentiated Quality of Service (QoS) guarantees between multimedia and data services, IEEE 802.11e was proposed. However, its performance and flexibility need to be further improved. In this paper, after a survey on various modifications of IEEE 802.11e, we formulate the problem of video transmission over IEEE 802.11e networks to help scheme design and performance analysis. Then accompanied with in-depth analysis, an adaptive unequal protection schema is proposed, which is composed of three mechanisms: (1) Insert each video packet into the access category (AC) with the minimum relative queuing delay; (2) Assign each packet dynamically to a proper AC based on several parameters to guarantee the transmission of high priority frames; (3) Apply fuzzy logic controllers to adjust parameters so as to reply quickly to the variation of video data rate, coding structure and network load. Finally, regarding MPEG-4 codec as the example, we perform extensive evaluations and validate the effectiveness and flexibility of proposed scheme. Simulations are divided into WLAN and multihop parts, involving different video sequences and various traffic modes of data streams. Beside performance comparison between proposed scheme and other ones, influence of parameter setting and combination with routing algorithms are also evaluated.     

Digital neural emulators using tree accumulation and communicationstructures

Three digital artificial neural network processors suitable for the emulation of fully interconnected neural networks are proposed. The processors use N(2) multipliers and an arrangement of tree structures that provide the communication and accumulation function either individually or in a combined manner using communicating adder trees. The performance for the emulation of an N-neuron network for all processors is achieved in 2log(2)N+C time units, where C is a constant equal to the multiplication, neuron activation, and internal fixed delays. The feasibility and characteristics of the proposed configurations to emulate single and/or multiple neural networks simultaneously are discussed, and a comparison with recently proposed neurocomputer architectures is reported.     

提升LoRa网络性能的终端参数动态选择方法研究

针对当前大部分LoRa网络因终端采用静态参数配置而导致的网络灵活性和通信效率不高等问题,提出了一种基于正交遗传算法改善LoRa网络性能的动态参数选择方法。分析了不同参数配置对网络通信性能的影响,针对LoRa网络建立信道冲突和链路预算模型,通过引入基于多目标遗传算法的动态参数选择方法求解该模型,最终获得具有最小冲突概率的参数集。通过对超过10 000台设备的单网关LoRa网络的运行结果表明,所提出的动态参数选择算法可将网络的分组交付率（Packet Delivery Rate,PDR）提高30%,显著提高了网络在不同应用场景下的适应性和扩展能力。     

WSN中利用蚁群路径优化的时隙选择重排算法

针对无线传感器网络(WSN)汇聚传输中的数据传输时间和功耗问题,提出了考虑时间同步和唤醒延迟的汇聚传输时隙选择重排算法。将时分多址接入(TDMA)用作介质访问协议,并允许每个节点在传输时隙期间可以发送或接收数据;设计新的WSN数据收集树模型,将传感器节点生成的数据通过无线链路形成的多跳网络发送到汇聚节点,在数据收集树的每条链路上分析时隙顺序,优化时隙选择,并基于蚁群算法优化路径选择,减少传输能量消耗和均衡簇头能量。实验结果表明,提出的算法可以实现显著的数据传输性能提高和功耗节约。     

Joint power-playout control for media streaming over wireless links

Media streaming applications over wireless links face various challenges, due to both the nature of the wireless channel and the stringent delivery requirements of media traffic. In this paper, we seek to improve the performance of media streaming over an interference-limited wireless link, by using appropriate transmission and playout control. In particular, we choose both the power at the transmitter and the playout scheduling at the receiver, so as to minimize the power consumption and maximize the media playout quality. We formulate the problem using a dynamic programming approach, and study the structural properties of the optimal solution. We further develop a justified, low-complexity heuristic that achieves significant performance gain over benchmark systems. In particular, our joint power-playout heuristic outperforms: 1) the optimal power control policy in the regime where power is most important and 2) the optimal playout control policy in the regime where media (playout) quality is most important; furthermore, this heuristic has only a slight performance loss as compared to the optimal joint power-playout control policy over the entire range of the investigation.