Earticle

Nowadays, Internet privacy becomes more and more important and sensitive, and has been one of the latest buzz words to hit the Internet world. In response to protect the privacy of Internet users, a variety of privacy enhancing technologies (PETs) have emerged. As one of privacy enhancing technologies, anonymous communication has been extensively studied from various aspects by researchers. Node churn is frequent in anonymous network, which make it difficult to maintain a stable network topology, therefore it is necessary to get more insight into the overall anonymous network topology. In this work, in order to better grasp the present situation of research, we investigate existing organizations and universities which study anonymous communication from the perspective of network topology, and related projects. Then we survey related papers to anonymous communication published in recent years, which focus on the analysis of node selection (especially in the Tor). In addition, we present a framework of anonymous communication network topology, and a visual illustration of this analysis that shows the progression of the research of network topology and node discovery in anonymous communication. Finally, some related problems and follow-up study are presented to be studied deeply in future.

Optical burst switching (OBS) has attracted interest of many from researchers to industries as a transport network architecture for the future optical Internet. OBS acts as a backbone to the Internet by providing long distance and large bandwidth links. In this work, we study the OBS networks in a very well-known network simulator tool “NCTUns” along-with the study of its performance evaluation. NCTUns is a high fidelity network simulator which can be used for simulating both wired and wireless networks. The simulation setup and evaluation results have been generated in NCTUns 6.0 running on Fedora 12 with kernel version 2.6.31.6.

To meet the higher data rate requirement of encoder, an encoder structure suitable for both two rates(1/2,2/3B) in WIMAX standard is proposed, combined with the method of Design Space Exploration. According to the quasi cyclic characteristics of sparse parity check matrix, the traditional RU algorithm is simplified and optimized to reduce the complexity of the system. Simultaneously we introduce a barrel shifter, and use the method that two rows of the base matrix be restored in one ROM to reduce resource consumption. The simulation results show that the encoder for two rates not only runs successfully, but also reduces the utilization of hardware resources. The encoder architecture has broad application prospects with high flexibility.

Correlation of wireless sensor network data is the foundation and premise of using compressive sensing theory to reconstruct the network data as well as the main basis for the design of network data reconstruction algorithm. However, various interferences of network data in practical transmission would result in consistent changes of correlation, thus lead to sharply aggravation of reconstruction performances in the existing compressive sensing theory. In order to improve the reliability and efficiency of compressive sensing of wireless sensor network data, a correlation adaptive reconstruction algorithm for network data is proposed. This algorithm first estimates the correlation of data to be reconstructed through iteration and then restores the data to be restructured using the two-step correlation test method of support elements. Compared to the previous reconstruction methods, correlation adaptive reconstruction method can greatly improve the reconstruction accuracy when the correlation of network data is changing.

Cooperative communication has been proposed recently in wireless communication systems because of its producing high network reliability and considerable error rate decrease with an extension in the coverage area in wireless networks without need for an increase in the infrastructure. The most challenging problem in implementing cooperation protocols in cooperative wireless networks is the relay selection. This paper proposes a relay selection technique based on Decode-and-Forward (DF) relaying protocol, using the available channel state information (CSI) at the source and the relays. We first establish a closed form symbol error rate (SER) by using the concept of moment generating function (MGF) for both M phase shift keying (MPSK) and M quadrature amplitude modulation (MQAM) signals. By finding the cumulative density function (CDF) and the probability density function (PDF); this facilitated the derivation of a new SER and can propose an optimal power method with relay selection (RS) technique where only the best relay is selected that maximizes the signal-to-noise ratio (SNR) to achieve the transmission process and develop the performance of the system. Finally, simulation results provided good confirmation of the theoretical analysis.

Time synchronization is critical for most distributed systems, especially for low-duty-cycle Wireless Sensor Networks(WSNs). Low-duty-cycle WSNs make use of time synchronization in many contexts(scheduling and sleeping, TDMA, Event Identification, data fusion, etc). A novel adaptive source time synchronization algorithm designed for low-duty-cycle WSNs, namely ASTS, is presented in the paper. The algorithm can be used for a small Low-Duty-Cycle WSN to be synchronized to a common clock, or used for a giant Low-Duty-Cycle WSN to be synchronized distributed. To improve the synchronization accuracy, all nodes estimate their time drifts relative to their neighbors using Maximum Likelihood Estimation, and get be synchronized to a common clock or their heads based on a vector of time drifts carried by the reference packet sent by the reference node. Simulation shows that the algorithm drastically improves the synchronization accuracy and scalability, and is much more applicable for low-duty-cycle WSNs than other synchronization algorithms.

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.

Wireless sensor network is a collection of sensor nodes with limited processor and limited memory unit embedded in it. Sensor networks are used in wide range of applications such as Environment monitoring, health, industrial control units, military applications and many more. This paper defines the security requirements and various attacks on sensor network. This paper also review proposed security mechanisms for WSN.

Biaxially oriented polyester film (BOPET) defect is an important factor affecting the quality of the film. In view of identification of defects in the conventional film production process, this mathod resulted in the identification of defects inaccurate. and low labor efficiency and machine vision recognition on identification of specific defect. This paper presents a LVQ neural network-based BOPET film of defects detection and identification methods. In this algorithm, the film images were processed and the outlines of the membrane defects were obtained. Through extracting the aspect ration, circularity, complexity and elongation , projection histogram central moment and so on, the characteristic values of membrane defects, which from the image of film images after image processing, and then input to the defects recognition system based on LVQ neural network that had been trained, in order to achieve the film defects identification, classification and localization. Through the study of features of the defects in BOPET and extracted some quantities as character input of the LVQ neural network, then input some characteristic values as training value into the LVQ neural network to achieve the learning and prediction purpose, and the LVQ neural network was designed. The experiments show that, the proposed method can meet the requirements analysis of air defects in transparent film.

In modern wireless networks, multicast is a very important technique to improve network performance, including throughput, delay, energy efficiency, loss monitoring, etc. The quality of wireless links in wireless networks is affected by many factors like collisions, fading, packet loss problem and noise. Multicast techniques and reliable multicast protocol are used to resolve these negative factors and improve throughput and reduce delay in lossy wireless networks. Point-to-multipoint data transmission over wireless IP networks occurs in multicast technology. Bandwidth of network saved and load on the network is reduced with the use of multicast technique. In this paper, the four key techniques named as LP-based opportunistic routing structure, opportunistic feeding, fast batch moving and inter-batch coding, are reviewed.

Delay Tolerant Network (referred to as DTN), tend to have a high latency , low transmission rate , intermittent connections, nodes frequently move , delay tolerance, fault tolerance , limited storage and communication features harsh environment , the traditional TCP-based / IP Internet technology to-end communications cannot provide good service . This article aims to delay proposed opportunistic routing algorithm performance based on energy (EROD) tolerant network environment , solve network in extremely harsh environments , end to end path does not exist , the message routing and forwarding problems. Under the premise to ensure reliable transmission of messages , minimize transmission delay and reduce the messaging process of resource consumption.

The actual demand for network applications, the paper discusses the data backup, real-time data synchronization knowledge; On this basis, considering the multi-user concurrency, the case of multi-user collaboration, to achieve a multi-machine real-time synchronization, proposed a network synchronization system model, describes its design ideas and development methods. The results show that: the system update for the relatively low intensity operations with relatively good efficiency of backup and synchronization synergy.

A wireless sensor network (WSN) is a network consisting of wireless computing devices called sensors that sense environmental conditions like motion, sound, etc in an area. These networks collect the information from the environment and send it to the sink node. The main constraint in these networks is the energy of the nodes. As these sensors have limited battery life, routing protocol should be designed appropriately so that minimal energy is used. Long communication distances between the sensors and the sink in the WSN drain the energy of the sensors and reduce the lifetime of the network. Clustering reduces energy consumption. By clustering a sensor network we can help minimize the total communication distance, thus increasing the network lifetime. In this paper, we an algorithm based on LEACH (Low Energy Adaptive Clustering Hierarchy protocol) using genetic algorithm has been proposed in order to achieve increased lifetime of the network and energy efficiency in WSN. The genetic algorithm is used to select the cluster heads for the WSN and hence create the energy efficient clusters for transmission of data in the wireless sensor network. The fitness function proposed in this algorithm considers both the distance of the nodes from the sink and their energies. The simulation results show that the proposed protocol results in prolonged network lifetime and optimal energy consumption of the wireless sensor network.

Vertical handoff is the mutual fused result of heterogeneous wireless network.In the process of vertical handoff, switching decision is a very important link which determines handoff function directly. For the increasing sensor network characteristics,in this paper, it will quote heterogeneous networks which consist of WSN and WLAN as samples to analyze present vertical handoff relative algorithms, by analyzing node moving speed to propose relative vertical handoff algorithms. During the selection procedure of target networks, it analyzed the relative factors in detail which affected network selection. As the residence time of mobile terminals is different in various covered area,it brought in concept of speed thresholds and made improvements for selection algorithm of combined vertical handoff network. The simulation result shows that improved selection algorithm of combined vertical handoff network can choose the best network to access according to mobile terminals moving speed.

Mobile ad-hoc networks (MANET) they can be deploy simply in a few environment without any determination. A major point that affectssuch a networks that characterize by dynamic change in topologyis the performance where routing worth forcefulperformance is one of the key challenges in deploying MANET. Black hole attacks node false advertises that they have secured path source to destination. In this paper the performance of proactive routing protocols Destination-Sequenced Distance Vector (DSDV) and Improved Destination-Sequenced Distance Vector (I-DSDV) evaluated under Ipv6 environment using black hole attack under different performance metrics Packet delivery Fraction (PDF), Delay, Routing Overhead (RO). The study in MANET is done with network simulator version 2 simulator.

Due to the cost, reliability and quality of communication equilibrium of the traditional FM radio network optimization algorithms during the construction , hierarchical multi-objective optimization algorithm is put forth.First, increasee FM wireless networks mobile node and select new-adding link waypoints’ optimal vector set, then design a hierarchical optimization model, and then use hierarchical multi-objective optimization algorithm to solve the problems of VHF wireless networks.Finally, compared simulation experiment of stratified multi-objective optimization algorithm and Glid algorithm and violent search algorithm is conducted, and the experiment shows that: stratified multi-objective optimization algorithm is smaller than traditional optimization algorithms in areas such in the network nodes, the average communication jump and the average attenuation of communication after running 50 times, i.e. lower cost, better network reliability and communication quality.

In order to reduce business latency and packet loss rate, to improve the throughput of integration of heterogeneous wireless network, to achieve load diversification and to improve end quality of service, while there are many problems on the dropout rate of the traditional load balancing algorithm in processing throughput, delay and business, therefore, gateway load balancing algorithm is proposed in this paper. All terminals in the access network can reflect the effectiveness of the average network load level of the network, this algorithm will gain weight of the load in the network of small business terminal to switch to the network load which is light. First, it defines the heterogeneous networks and network terminal payoff function utility function, which are used to characterize the experience and network QOS terminal load situation, and then presents the specific processes of the gateway load balancing algorithm. Finally, switching decisional load balancing algorithm, proposed by Yan X, etc. is compared with simulation experiments and it shows that: the proposed gateway load balancing algorithm has strong robustness to achieve network load balancing and to achieve a balanced use of network resource.

OFDM (Orthogonal Frequency Division Multiplexing) is a promising technique for 4G and 3GPP LTE system in terms of providing the higher data rate and efficient use of bandwidth. But OFDM suffers from ISI and ICI interferences in wireless and fading environment. There is a loss of certain amount of data because of these interferences, thus synchronization is required. It is important to estimate and correct the start of OFDM symbol efficiently to reduce timing and frequency offset errors. The paper mainly focus on the CFO problem present in OFDM system, describes the effect of CFO in OFDM system and provides the estimation techniques for CFO in time domain and frequency domain. The simulation results are performed for the CFO estimation technique with different values of CFO and then results has been compared.

Address resolution is an important process in network communications. The primary function of address resolution is to determine the correspondence of a target network address to a physical address. The traditional address resolution process assumes that all the nodes on a network are honest and credible, and these nodes directly broadcast the resolution target address on the network. This process enables malicious nodes to easily mount attacks. We propose a reverse address resolution process with variable length prefix (called Re-AR) that obviates such attacks. According to the revelation principle, a node’s <IP, MAC> mapping can be viewed as a private type in the address resolution process. In our proposed process, after a node receives an address resolution request broadcast, it unicasts the private type to a positive resolve node that assigns the communication to the correct node according to a predetermined mechanism. Based on simulation results, when the destination address is hidden in the broadcast packets, malicious nodes cannot easily conduct spoofing attacks according to the destination addresses. This phenomenon effectively prevents spoofing and significantly reduces the pollution rate of address cache tables.

Synchronization of chaotic system is meaningful and widely used in secure communication. A kind of robust adaptive synchronization method was proposed to solve a special chaotic synchronization problem that both response system and driven system have unknown parameters and uncertain nonlinear functions. And the difficulty is also caused by the different structures between master chaotic system and slave chaotic system. A kind of update law of estimation of unknown parameters were designed by choose a proper Lyapunov energy function. And the stability of the whole system is guaranteed by Lyapunov stability theorem. At last, detailed numerical simulation was done to show the rightness of the proposed method.

This paper presents Long Reach Wavelength Division Multiplexing Passive Optical Network (WDM-PON) system capable of delivering downstream 40 Gbit/s data and upstream 40 Gbit/s data on a single wavelength. The optical source for downstream data and upstream data is mode locked laser at central office and reflective semiconductor optical amplifier (RSOA) at each optical network unit. We use four RSOAs at each optical network unit for the 40-Gb/s upstream transmission. The operating wavelengths of these RSOAs are separated by the free-spectral range of the optical demultiplexer at the central office and remote node (RN) for demultiplexing the WDM channels. We extend the maximum reach of this WDM PON to be 117 km by using Erbium-doped fiber amplifiers at the RN. Bit error rate, were measured to demonstrate the proposed scheme. In this paper Long reach and large data service aspects of a WDM-PON is presented. The results show that the error-free transmission can be achieved for all WDM channels with sufficient power margins.

Regional Logistics Information Platform is the core and key development factor of modern logistics industry. Through the construction of logistics information platform, it can greatly promote the information-oriented for modern logistics development. The concept, characteristic and requirements of regional logistics information platform are defined. The function and operation mechanism of it have been analyzed. Based on the analysis, the frame of the information platform has been designed.

The mobile Adhoc network is deployed in the environment where traditional wired network cannot be established due to its required features and their limitation. Use of directional antenna is one of the most promising technique for the high speed wireless network such as IEEE 802.11.Proposed a new directional MAC protocol to address the Directional Hidden terminal problem and Directional Exposed Terminal Problem.

Particle swarm optimization (POS) algorithm is a reference to the mechanism of the biological predation community of a random search algorithm, the validity of its search, got extensive application in many ways.But the particle swarm algorithm has poor local search ability and easy early faults.So on the basis of it, combined with the genetic algorithm is proposed based on a mixed particle swarm algorithm.The new algorithm USES the similar to the mutation and crossover operation of genetic algorithm, speed and position update formula easier to express.To primary respectively after the particle group division evolution, global optimization to the formation of new species.Applied in the IP network quality of service routing optimization mixed POS algorithm, both meet the requirement of quality of service and will choose the path cost minimum as the optimization index.Through a series of simulation experiments of network routing, the improved algorithm has good effect.

To deal with the issues like existing generation of congestion nodes and redundancy transmission in the traditional load balancing algorithm, this paper puts forward the load balance multicast routing and spectrum allocation algorithm based on QOS constraints. The algorithm adopts LBWC algorithm to calculate the wireless link weight, and carries out the structure of the load balancing multicast tree. Then, the QOS constraints spectrum allocation algorithm is adopted based on wireless channel broadcast feature to conduct channel allocation of wireless link. Algorithm in this paper is under the condition of wireless multicast QOS constraints satisfactions, which balance the node load, minimize the transmission times of the wireless multicast business and reduce the consumption of network resources. Finally, simulation experiments are carried out, such as the influence of wireless multicast business number on the performance of the algorithm, the influence of the number of multicast destination node on the performance of the algorithm, the influence of the number of available channel on the performance of the algorithm and the influence of the control parameter β on the performance of algorithm, etc. Experimental results show that in the case of wireless multicast service constraint, the algorithm avoids the congestion nodes and reduces the times of transmission.

A method for bitwise energy optimization of turbo codes with large size is developed. Unlike earlier methods, which relied on searching for minimum-weight codewords, the proposed method finds the required parameters using two bit error rate (BER) distributions obtained via simulation. Therefore, this method can be used not only for the codes with small codeword length, but also for the codes with large codeword length. Simulation results show BER improvements for turbo codes. Though the method is applied to turbo codes in this letter for concreteness, it can also be used for other kinds of error control codes because it does not rely on the code’s structure.

Since both video compressing rate and network bandwidth keep increasing continuously, more and more video applications emerged. Although DiffServ (Differentiated services) is a simple and effective architecture to ensure quality of service for simultaneously transmitted video and data streams, it is not suitable for multiple video streaming. In this paper we evaluate the performance of multiple video streaming using standard DiffServ architecture and two priority based enhanced schemes (named IP based scheme and CCP based scheme). Simulation results show that (1) IP based scheme outperforms CCP based scheme and standard DiffServ. (2) WRR and WIRR scheduling modes are suggested to be adopted. The higher the data rate of a video is, the larger the weight of that video should be set to. (3) RED parameters for different queues should be carefully set according to the available bandwidth for video streams, and the data rates and coding structures of different videos.

In past few years, mobile ad hoc network has gaining more attention of researchers. Mobile Adhoc Network (MANET) are most widely used all over the world, due to its ability to communicate each other without the use of any fixed network. It applications used in military network, disaster relief operations and also in commercial environments. Due to open, dynamic and infrastructure-less nature, the ad hoc networks are vulnerable to various attacks. The black hole and grayhole attack is one of them in MANET. Security is an necessary requirement in MANET. Without any proper security solution, the malicious node in the network will act as a normal node which causes eaves dropping and selective forwarding attack generally known as Gray Hole attack. In this paper we survey on MANET applications, routing protocols, different types of attacks and also the review of researchers.

Data fusion in wireless sensor network is a effective method to reduce the network energy consumption. In order to build high performance of data fusion system, a data fusion algorithm using BP neural network to optimize fuzzy prediction and train the membership degree of collecting data is presented, which is used to determine which kind of dividing fusion mechanism is belonged for the sensor’s data collected at a given moment. First the fuzzy prediction is used for acquisition of knowledge which data is simplified to remove redundant properties and samples. The BP neural network is used to process fuzzy prediction and finally the patterns of muli-sensed-data(temperature as an example) fusion distribution are formed. Two kinds of different BP neural network are proposed and compared for more precision of the fuzzy prediction result. Second data fusion based on the fuzzy prediction will be implemented to reduce the number of data transmission in the network. Simulation results show that the algorithm has good precision and applicability.

Opportunistic network is an evolution of MANETs to delivery messages in intermittent-ly connected or completely disconnected wireless networks. Message ferrying is an effec-tive routing mode in opportunistic networks. However, the single message ferry routing scheme leads a much higher delay as the increasing of the network scale, comparing with that in small scale opportunistic networks. It has been proved that multiple message fer-ries routing scheme can improve the performance of large scale networks, but the prob-lems of synchronization and coordinate between ferries have a bad effect on the routing efficiency. To solve these problems, a Hybrid Message Ferrying Scheme (HMFS) for clus-tered opportunistic networks is proposed. In HMFS, we divide the communication area into multiple regions based on clustering results and several cross zones containing the regions. A local ferry is deployed in each region to deliver messages in the region, and several global ferries are deployed according to horizontal and vertical zones to commu-nicate among the regions. Moreover, each region has a ferry relay node in it, which is used to orchestrate the local ferry and global ferries. Through the theoretical analysis and simulation results, we can see that HMFS can improve the effect of routing in oppor-tunistic networks in terms of network latency and delivery ratio.