Earticle

With the development of the telecommunication, optical fiber has been widely used. It has the characteristics of long distance transmission and large capacity, but it also has dispersion exists. The dispersion can be divided into some types. Mode dispersion plays a major role in multimode fiber, while chromatic dispersion or intramodal dispersion are the main mechanism in single mode fiber. Generally, it is quite important to test the dispersion and know the dispersion characteristics. The theoretical basis and experimental device, which are both based on the interference principle, have been introduced in detail. The device is used to measure the fiber dispersion characteristics of optical fiber and the results shows the validity of the theory and the designed test device.

With the rapid development of network and information technology, there is a wealth of huge amounts of data on the internet. But it’s a major problem faced by the majority of researchers how to effectively filter out a particular subject or field of information from these data. In this paper, we try to builder a focused crawler based on vector space model and TF-IDF text correlation analysis. We take the seed URL as a collection entrance and fetch web pages from internet. Then analysis page information though technological like web content extraction, page link analysis technology and get the main content of one page. By the correlation analysis method based on VSM and TF-IDF text, we calculation the correlation between pages and the topics what have been defined, so we can achieve the purpose of the focus areas of the web.

Heterogeneous networks are composed of different access technology together to provide Always Best Connected services in anywhere at any time. In such environment mobility is the major issue. Existing mobility support protocols like MIPv6, HMIPv6 and FMIPv6 are performing low during vertical handoff process. To improve QoS performances and to interconnect different networks, an agent called NIA (network interworking agent) and multiple IGMA (interworking gateway mobility agent) has been deployed. The UDP and TCP simulation results are obtained using NS2 environment and compared with an existing macro mobility protocols.

Transforming the convolution to the (+,-) in legend domain is proposed in this paper. Based on the transformation, the Legend Transformation of service curve and arrive curve is given in the case of independent cross traffic, and the closed expression of stochastic delay and stochastic backlog is obtained. In the paper, we analyze influence of the dynamic of traffic and network to QoS parameter. Based on the analysis result, the QoS analysis in Legend domain is given, and the upper bound of delay and backlog in Legend domain. For the case of non-independent cross traffic, the relationship expression of different traffic is got. And simulation proves that the route optimization algorithm is correct.

Mobile Ad-hoc Network (MANET) is referred as continuously self configuring and infrastructure-less network of mobile devices connected without wires. The Wireless Sensor Network (WSN) is an emerging area and some of the studies came out with association of MANET, which is referred as MASNET. This paper evaluates the performance of Adaptive Secured Multipath Routing (ASMR) when it is associated with QRS and RZLSR proposals. Multipath routing is an efficient technique in handling failovers and it improves the Quality of Service (QOS). Increasing the number of vulnerabilities imposed us to use the secured multipath routing. The proposed technique is adaptable for MANET and WSN, when they deal with unreliable data communications. ASMR is desperately outperforming when it is associated with RZLSR compared to QRS scheme and it is assisting for secure data transmission.

There are 10 sets of CNC equipment in a numerical controlled workshop, and set up the CAD/CAPP/CAM center, there is a problem that each production unit is an information island, which can not implement informatization management. This paper takes ZNE-100TL module realized the embedded Ethernet and RS-232C data transfer function as the hardware platform, takes VC++ as software platform, applied Ethernet technology to realize communication the CNC equipment with CAD/CAPP/CAM center. This is good for production management and data transmission in numerical controlled workshop, which can improve the production efficiency.

Mobile ad hoc network (MANET) is a type of ad hoc network that MANET nodes can change their locations and configure by themselves on the fly. Because of mobility the MANET nodes, the management of a large MANET is difficult, therefore, clustering in a MANET is an important technique. A large network is divided into several sub networks applying clustering method. When the topology of the network is dynamic and ad hoc, the process of clustering is very complicated. In this paper, we propose a Probabilistic Algorithm for MANET Clustering (PAMC) to improve the performance of this wireless technology. We simulate our algorithm and evaluate it based on two criteria: the average number of clusters and the average re-affiliation.

Cognitive Radio (CR) is a novel technology that can improve the utilization efficiency of the radio spectrum and also address the spectrum scarcity problem by opportunistically using the unused channels (spectrum holes / white spaces) in the Licensed Spectrum of Primary Users. Spectrum sensing is the primary function of CR which determines the spectrum holes for opportunistic usage by Secondary Users. Spectrum sensing plays a critical role in Cognitive Radio. The development of a reliable and accurate spectrum sensing is very essential to propound quick and accurate detection of white spaces for better throughput of Secondary User network under the constraint of the specified Primary System protection. In this paper, a Cooperative Spectrum Sensing using Wavelet Denoising along with Soften Hard Decision technique has been proposed to improve the performance of spectrum sensing. Simulation result shows an improvement of nearly 15% in the Probability of Missed Detection for a target Probability of False Alarm of 0.1 and SNR of -10 dB. Also 50% improvement in error probability has been achieved with 1-D one level wavelet denoising.

Dispersion is widely existed in the optical fiber. The reason is various, such as material dispersion, waveguide dispersion, mode dispersion, and so on. It will lead to the signal waveform distortion and pulse broadening and then limit the transmission capacity and bandwidth in the optical fiber. With the rapid development, transmission rate can reach even hundreds of Gb/s, and it may lead to many problems. Correspondingly, compensation methods have been paid much attention, and there are also many methods proposed for the compensation. However, we should know the characteristics of the dispersion in order to get compensation algorithms with much higher efficiency. Optical fiber systems with better performance will be designed and manufactured. In this paper, appropriate methods are adopted to analyze the photonic crystal fiber. With the adjusting of the structure parameters, we can design a highly nonlinear photonic crystal fiber with different dispersion characteristics. We study the characteristics of the dispersion of optical fiber communication. According to the analysis to obtain the dispersion characteristics of optical fiber under different parameters.

Now-a-days, wireless networks are playing vital role for facilitating communication between different entities for different purposes. In case of wireless networks, security aspect has now becomes a very major concern and most of the current researches are focusing in the same direction. This paper addresses the important problems relating to Black hole attack in adhoc network. During the research, a new and robust routing mechanism has been developed. Firstly, on the basis of Trust value and Credential value detection and prevention of Black hole attack has been performed. For assessing the performance of developed routing mechanism, experimentation has been done using NS2 simulator. Comparisons have been performed with AODV, Black hole AODV and results are as per the expectations.

Energy limited become a key and hot point problems of wireless sensor networks. This paper proposes a Coverage Strategy Based on probability-aware Model in Wireless Sensor Networks. The strategy using the probability-aware Model, Combining with the node coverage situation, eliminate redundant nodes, establish the optimal work node set, designed to reduce the network energy consumption, set a reasonable number of working nodes. The simulation results show that the new strategy not only to improve the network coverage, but also effectively prolong the network lifetime, improve the quality of network ,Meanwhile network coverage optimization control is realized.

We investigate the effects of antenna parameters on the radiation characteristics of a compact size Rectangular Microstrip Antenna suitable for mobile application. In the calculations of antenna parameters, resonant frequency is set at 3 GHz. In our investigations three low cost substrate materials, namely: (a) irradiated poly-guide with relative dielectric constant and loss tangent as Er=2.32, tanδ = 0.0005, (b) Glass-Epoxy with Er=3.7, tanδ = 0.02 and (c) R03006 with Er=6.15, tanδ = 0.0013 are used to simulate the antenna parameters obtained from various models. The simulation results predict that the BW increases with the increase in substrate thickness and decrease in dielectric constant, while directivity strongly depends on width of the patch. Here we will present in details the antenna model, its simulation and the results of our analysis.

Both in academic and industrial research, building a green energy-saving network has become a hot topic. Combined with hardware division and adaptive algorithm, this paper proposes an adaptive frequency control mechanism based on traffic to reduce power consumption. By calculating real-time traffic, the network device can adjust its operating frequency. On the premise of maintaining network performance, this mechanism could reduce the power consumption significantly. Besides, the adaptive frequency mechanism has been verified and realized in the NetFPGA Reference Router. Experimental data show that under different ranges of traffic loads and without affect its performance, the Router embedded this mechanism can reduce power consumption by more than 20%.

In recent years, with the further development and more applications emerging, WSNs is no longer confined to the traditional area. Because WSNs is dynamic, distribution, resource constrained, uncertainty, complexity and heterogeneity, meanwhile distinct WSNs applications have distinct characteristics and requirements in the respective field, which both urge us to further research, especially performance evaluation of WSNs. In this paper, we expand the range of performance index which exceeds time delay, packet loss rate, and throughput. Meanwhile, put forward a non-equilibrium statistical mechanics model for integrated WSNs performance evaluation from an evolutionary perspective. A non-linear information dynamics mode is introduced based on the maximum flux principle during the modeling process. The integrated performance evaluation of WSNs can be done by giving reasonable weights of each evaluation index to stabilize the system. The new model reveals the formation pattern and the dynamics law of evolution. The proposed method has been serviced in complex simulation, and the results have indicated that the model is objective and effective.

HTTP-based Adaptive Streaming (HAS) has emerged as the prominent technology for the delivery of audiovisual content over the Internet in recent years and has a major impact on network traffic. Although traditional stateful session-based streaming solution based on UDP was used initially for media content delivery, researchers and practitioners soon realize that HAS technology, due to get through firewalls friendly ,transfer NAT easily ,effectively utilize the existing networking infrastructure and provide uninterrupted video streaming service to users with dynamic network conditions and heterogeneous devices, has the potential to improve the Quality of Experiments compared with traditional streaming technologies. Consequently, various HAS media streaming solutions have been proposed and deployed successfully. This paper reviews the state-of-the-art of HAS technology and discoveries achieved by numerous researchers. We describe the basic taxonomy of HTTP adaptive streaming systems and summarize the major issues associated with HAS systems’ design. Then we outline the key challenges and open problems and highlight possible avenues for future directions.

In cognitive radio Ad Hoc networks, the events of node failure and link failure maybe happen frequently, especially the primary users will access the authorized channel whenever possible. In order to maintain the connection between cognitive users and resume their communication as soon as possible when the current route is invalid, a reliable routing mechanism CARC is proposed, which employs primary and candidate route to communicate under differential cases. Meanwhile, how to choose candidate route, maintain or rebuild route are also elaborated. Numerical simulations show that the proposed CARC protocol has a higher performance compared with other typical protocols.

This paper focuses on the optimal relay selection and power allocation issue, which studies the communication between SS (Secondary Source) and two SDs (Secondary Destinations) through single relay in CR （cooperative cognitive communication） system. Sufficiently takes the multi-antenna relay, primary-secondary users coexisting, and AF (Amplify and Forward) relay mode as the researching background, and takes the constraints caused by the primary user’s interference and the max transmission power into account, the author proposes to maximize the system throughput by the selection of cooperative relay and the allocation of optimal power. Furthermore, the author also puts forward the approximate expressions of the optimal power allocation, and figures out the optimal solution by the Lagrange multiplier, whose property can be manifested by the simulation and comparison results.

Network coding is a new paradigm in data transport and promises to change many aspects of wireless sensor network (WSN). Thanks to the recently developed network coding techniques, a high-throughput low-complexity hierarchical protocol can be facilitated due to the multiple-source relay-based data transmissions built on the network coding schemes, especially for the data communications between the source node and destination node. In this paper, we propose an Energy efficient that carefully couples Network coding and Multipath routing algorithm in Wireless Sensor Networks (ENM-WSN). Through an analytical study, we provide guidance on how to choose parameters in our scheme and demonstrate that the scheme is efficient in both multipath and energy consumption. We also present an algorithm for deciding the network coding scheme for a node to further reduce energy consumption by minimizing redundant packet transmissions. Simulation results show that, with the proposed energy efficient with network coding in WSN multipath routing protocol (ENM-WSN), energy consumption, packet delivery ratio, and network lifetime can be improved in most of cases. It is an available approach to multipath routing decision.

Differing from the physical connectivity of the topology structure, the logical connectivity of VANET considers both the interior network configuration and the external communication environment. Hence, the traditional mathematical analysis and modeling methods which are usually used in physical connectivity research are no longer suitable for the logical connectivity prediction. Taking the AODV protocol as an example, this paper simulates the effects of different road traffic parameters on logical connectivity probability and selects three main effect factors, roadway length, vehicle number and vehicle speed. Furthermore, the inner relation between the logical connectivity and the three road traffic parameters is studied based on data mining technique and then two logical connectivity prediction models are presented, the nonlinear regression-based model and the extreme learning machine-based model. Simulation results show that the two models are both with high accuracy in predicting the network logical connectivity under different road traffic environments.

Vehicular ad hoc networks or VANET that establishes wireless connections between cars have recently received considerable attention. VANET are used in Intelligent Transportation Systems (ITS) that are designed to offer passengers and vehicles services like warning of accidents, driver assistance, Internet access, etc. The evaluation of VANET routing protocols often involves simulators since management and operation of a large number of real vehicular nodes is expensive. We study the behavior of routing protocols in VANETs by using mobility information obtained from a microscopic vehicular traffic simulator that is based on the real road maps of Tangier in Morocco. In this paper, we evaluate AODV, DSR and OLSR performance in urban scenarios case study. We study those protocols under varying metrics such as node mobility, vehicle density, and with varying traffic rates. We show that clustering effects created by cars aggregating at intersections have remarkable impacts on evaluation and performance metrics. Our objective is to provide a qualitative assessment of the applicability of the protocols in different vehicular scenarios. The results show that OLSR performs best in most of the simulated traffic situations

Picture archiving and communication systems (PACS) require high-speed networks to transmit large image files between components. Image-data transmission from one site to another through public network is usually characterized in term of privacy, authenticity, and integrity. However, public network’s security issues had always been the significant problems. Recent years, IPv6 brings significant improvements in mechanisms for assuring a higher level of security and confidentiality of the transmitted information. Thus, it is still necessary to take care of some particular aspects. In this paper, we first analyzes how actual security threats and different types of attacks affect IPv6 networks while transmitting Digital Imaging and Communications in Medicine (DICOM) files through the public Internet. Second, illustrate some shortcomings of IPv6 and IPv6’s traffic loads. Finally, some possible solutions against a number of security threats in IPv6 DICOM files transmitting networks have been given.