Earticle

In order to reduce localization error of the sensor node, a novel node localization algorithm (DVHop-Steff) is proposed in this paper based on DV-Hop algorithm and Steffensen iterative method. Firstly, DV-Hop algorithm is used to obtain location position of wireless sensor nodes; and then Steffensen iterative method is used to correct the locate results of DV-Hop algorithm and achieve higher localization precision, finally, the performance of the proposed algorithm is tested by simulation analysis. The results show that the localization precision of the proposed algorithm has been improved significantly and has more wide application scope.

When a radio access network (RAN) environment cannot handle the tremendous mobile data traffic, users may experience degraded or declined services. To help process the large number of user video requests in RANs, a content delivery network (CDN) architecture has been recently introduced, which establishes a number of cache servers outside the source server for users to get the needed data from the nearest cache server. To upgrade the performance of a wireless CDN, this paper presents a new caching strategy based on analytical results of real user video request traces and specific caching considerations for videos with different popularity degrees. The new strategy first caches videos with high popularity to all helpers and then caches those with low popularity to the remaining helper storage to enhance the overall request hits. Performance evaluation exhibits that, when compared with other caching strategies, our new strategy is able to yield better request hits with low complexity and average delay time.

Aiming at different service quality requirements under different circumstances of wireless sensor network (WSN), harmony search (HS) algorithm is used to solve the low-delay and low-energy double-objective optimization problem in wireless sensor networks. First, analyze the low-delay and low-energy model, and establish the objective function. Then, use the priority-based path encoding algorithm to update harmony memory iteratively while searching the optimal path. Finally, simulation of 100-node network is carried out by using Matlab. The results show that sensor network data transmission path can be controlled according to the users’ needs of delay and power.

In order to create the idea of AC switch without electric arc and inrush voltage to the power system, the study of accurately catches AC zero crossing of a mechanical relay is put forward in this paper. It is the key to make the switch act at the right predicted time which realizes switch on or off exactly at the AC zero crossing point. However, the action time of a mechanical switch is affect by many factors such as driving voltage, ambient temperature, age of the mechanic structure. Aim at the discrete measurements of latching relay action time, the Kalman filter mathematic model is introduced in this paper to eliminate the dynamic noise and measurement noise which affects the bias time drift from the zero voltage or zero current point. Simulation result by matlab and group data get from experiments of a realized multichannel switch indicate that Kalman filter algorithm can overcome the discreteness of latching relay action time measurements. Also confirmed by statistical experiments that synchronous switch action precisely and reliably at AC zero point which can ensure the ability of suppress electric arc and high frequency inrush current.

The paper makes a brief introduction of Multiple Carrier- Code Division Multiple Access (MC-CDMA) scheme based on the principles of Orthogonal Frequency Division Multiplexing (OFDM) and CDMA, and a mathematical model of the uplink is established in MC-CDMA system. The simulation research on different multi-user detection methods in MC-CDMA system is implemented by using MATLAB software, and it also compares the impacts to system performance by several different multi-user detection methods, such as De-Correlation (DEC) multi-user detection, Minimum Mean Square Error (MMSE) multi-user detection and Parallel Interference Cancellation (PIC) multi-user detection, based on understanding and analyzing the experimental results. In addition, the paper also focuses on the research of multi level PIC multi-user detection performance in different primary detection methods and different series detections.

Routing protocol is the primary strategy to design any wireless network. In Mobile AdHoc Network many routing protocols are present for sending packets from source to destination. Routing protocols in Mobile AdHoc Networks (MANETs) are reactive routing protocols, proactive routing protocols, hybrid routing protocols. Performance analysis of different routing protocols is the major step before selecting the routing protocol. Routing protocols perform different under different traffic conditions in different environments. In this paper, the TCP and UDP based performance analysis is carried out in reactive routing protocols and proactive routing protocols with different packet size using NS2 simulator under different traffic conditions. The delay, throughput and packet delivery ratio are common measures parameters used for the comparison of performance of reactive protocols and proactive protocols.

In application of wireless sensor network, the position information of sensor node is crucial within life cycle in the whole network. In order to design algorithm of node positioning with high-efficiency, high-precision and low-consumption, this paper puts forward using the encryption algorithm of space control node originally applied in field of engineering measurement, by using SDI algorithm ( space and distance intersection algorithm) as three-dimensional position algorithm used in system to achieve three-dimensional automatic positioning calculation of distributed nodes. Test proves that this kind of algorithm has better positioning nature and higher precision; it is used as three-dimensional positioning because it has good engineering application value.

Nowadays, many network devices have more than one network interface. Meanwhile, many protocols have been proposed to utilize multiple paths simultaneously. MPTCP (Multipath TCP) is a transport layer protocol that transfers data by multiple paths simultaneously, which is designed to improve the throughput and increase robustness of end to end transmission. However, when we use MPTCP, we find that MPTCP can not improve the throughput but even reduce the throughput in some cases. In this paper, we study this issue. Firstly, we study the effects of path characteristics for throughput of MPTCP, and find that path characteristics especially those bad paths have a great impact on the performance of MPTCP. Secondly, we analyze the reasons why the bad path characteristics have a serious impact on throughput of MPTCP, and propose a path selection method based on throughput prediction model and available bandwidth to improve the throughput. Finally, we validate our path selection method by simulations, and the results show that our method can improve the throughput of MPTCP.

In wireless local area networks, management decisions concerning channel selection, rate selection, and power management have a profound impact on the throughput performance, particularly in dense areas. These measurements, however, are too weakly associated with the MAC layer to be able to make such management decisions. Therefore, direct measurements of the channel quality at the MAC layer are necessary to facilitate appropriate decision-making activities. Estimating quantities, such as the probability of collision and the probability of channel-induced errors, will enable the MAC layer to make suitable decisions1. This paper proposes a mechanism to calculate both the channel error probability and collision probability through the methodology of distribution. Some scenarios are discussed to demonstrate the effectiveness of the measurements.

This paper derives the analytical expression of the temporal autocorrelation function (ACF) of the non-stationary three dimensional (3D) multipath scattering channels, in which scatterers move with constant velocities in random directions around transceivers. The analytical expression involves high dimensional integration within finite interval, thus a methodology based on ray-tracing is proposed to carry out its numerical solution. The analytical expression and the corresponding ray-tracing based model serve as the canonical forms for the correlation analysis of non-stationary 3D multipath scattering channels, which include two special cases: two dimensional (2D) multipath scattering and stationary multipath scattering. Numerical results show that: in case of non-stationary 3D multipath scattering, with the increase of the velocity and the density of scatterers, the temporal ACF would attenuate more rapidly. These results would allow engineers more appropriate determination on coherence time and coherence bandwidth for vehicle-to-vehicle communication systems.

TCP congestion control protocols have low performances in high speed wide area networks mainly because their slow response with large congestion windows. This TCP behavior has initiated new design phase of alternative protocols that provide improved traffic utilization in high bandwidth delay product networks. The paper presents survey of various high speed sender side congestion control proposals that preserve the fundamental host to host principle. Solutions focus on variety of problems occurring in high speed environment with intention to eliminate congestion collapses and to ensure effective resource utilization. Internet data transfer does not depend only on that how TCP will utilize the network capacity, we have to stress that TCP must cooperate with existing transmitting data protocols through the same network in order to assure fair resource sharing. Part of the paper scope are state of the art high speed TCP proposals, we explore their congestion control techniques, strengths, weaknesses and we try to detect future TCP development possibilities.

Given the lag of IGS precise ephemeris and complexity of dynamic models, in order to solve the problem of long-term satellite orbit prediction in autonomous orbit determination, a new medium and long term orbit prediction method that based on satellite broadcast ephemeris parameters has been put forward. This method is that forecasting the orbit parameters firstly according to broadcast ephemeris history data, and then calculating satellite position according to the forecast ephemeris parameters. In order to verify the feasibility of this method, using 40 days of broadcast ephemeris data, adopting ARMA model combined with sliding window model to predict broadcast ephemeris orbit parameters value in 25 days. Analyzed the parameters prediction error and the influence of parameters prediction error to satellite orbit accuracy, 25 days of orbit prediction error can be controlled in 150 meters. The results show that the predictability of orbit parameters has certain application value for satellite orbit prediction, the medium and long term orbit prediction that based on the satellite broadcast ephemeris parameters is a new and feasible method of orbit prediction.

Aiming at studying the jamming methods of Link16 system, the anti-jamming techniques adopted by Link16 are studied and a simulation model is established in the paper. Based on the conventional static multi-tone interference which is used frequently at present, a new dynamic jamming method named Frequency Hopping Collision (FHC) interference is put forward. The features and jamming performance of FHC interference in the condition of different frequency hopping rate are analyzed and simulated. According to the analysis and simulation results, the jamming performance, advantages and disadvantages of the two jamming methods are compared in the same conditions. It is concluded that the new FHC interference has advantages over multi-tone interference from the aspects of utilization rate of jamming power and complexity of realization in jammer and also provides a new way for the jamming of Link16 system.

This paper presents a study of a coplanar waveguide (CPW-fed) antenna using a Modified Ground Structure (MGS). The antennas studied are relatively small in size (17 x 20) mm2 and was designed on a low-cost FR-4 substrate. The presented antenna models shows improvements in the impedance bandwidth, the center frequency and operating bands with the stages of modification being introduced in the ground structure. The designed antennas were simulated using Ansoft HFSS, a FEM based simulator and antenna’s characteristics such as Reflection coefficient, Center frequency, Operating frequency bands, Impedance bandwidth, and VSWR are reported in this paper.

Due to the wide use of encrypted protocols and random ports, traditional methods that based on port number or packet payload have gradually lose their effectiveness. To address this issue, new methods that based on machine learning techniques become the research hotspots. With many further studies, some research institutions show that ML-based protocol identification methods can generally achieve over 95% accuracy. However, different from most research studies, industry claims that ML-based techniques are hardly to be deployed for practical use due to their high false positives and false negatives. In this paper, different Machine Learning techniques are evaluated for the actual accuracy under different network environments, and a variety of features are tested on different encrypted protocols. The results show that the identification accuracy will go down due to the changed network scale and network environment while the same ML-based models are used under different network environments, and the choices among different Machine Learning techniques, protocol types or statistical features are not critical.

Due to increasing network threats, it has become imperative to build a system that is meant to protect the network primarily from intrusion. A discipline that is most oblivious is the layer two of the OSI, which opens the network to dangerous assaults and compromises. Nowadays there are various sophisticated offensive tools and technologies that can exploit these vulnerabilities to create havoc in the tech-savvy generation. ARP spoofing assault is among the most hazardous procedures in local discipline networks. This paper discusses poisoning of Address resolution protocol and the most advanced schemes which mitigate such attacks. This attack has been carried out under test environment for illustrations and various preventive methods against it have been tested and compared. This paper has highlighted in the end an ideal strategy to combat ARP attacks at a superior level than the already existing techniques.

Many applications for agricultural information and environment monitoring exploit buried sensors wired-connected to the soil surface for information retrieval. A novel wireless underground sensor networks is a specialized kind of wireless sensor network that communicates through soil. The wireless underground sensor networks (WUSN) consist of wireless devices that are buried completely under dense soil and operate below the ground surface. In this paper, the application research of the wireless underground sensor networks is described. Experimental measurements of the signal strength and packet error rate are presented at the frequency of 433MHz, which show a good agreement with the theoretical studies. The results show the buried depth of the WUSN node and the volumetric water content of the soil are the most important factor to adversely affect the communication.

As we all know, Network communication is essential in network transmission, while the transmission delay of Ethernet’s MAC (Media Access Control) layer will affect the quality of communication networks with the continuous progress and development of Ethernet technology. In this paper, we design and implement the correct receiving and sending of Ethernet MAC protocol layer’s packets with FPGA, through the in-depth analysis of Ethernet MAC packets transceiver. The simulation results of the transceiver module system level were given through the simulation test plat form we built, which shows that Ethernet MAC layer’s packets designed on the FPGA-based platform can receive and send faster, and the low system occupancy rate can meet the requirements of system throughput for real-time communication environment system, which can provide the technical support for the development of Gigabit Ethernet.

In order to reduce the transmission delay of the data packet in the wireless network, so as to improve the performance of the network, this paper proposes CGAR algorithm of the coding gain aware routing protocol. The algorithm uses the network coding gain and expected transmission count of the wireless link, provides the time needed for the node to transmit a data packet from the new flow in the wireless link, and take it as the routing metrics. This metric takes into consideration the factors such as the transmission delay, the time of the node’s contention channel and so on. The experimental results show that this algorithm can reduce the transmission delay of the data packet and improve the performance of the network.

Spectrum is the most valuable and scarce resource for every wireless application. Due to the scarcity of the spectrum other alternatives are also being searched. Cognitive Radio (CR) technology is one such alternative which has gained popularity in the recent times. It has been established from various researches that the allocated band is not in use for all the time by the licensed user or as Primary Users (PUs). The Cognitive Radio users also called as Secondary Users (SUs) communicate using unlicensed band or by using the idle licensed band of primary users opportunistically. This paper evaluates the performance of routing protocols by varying concentration level of PU and SU. We have also investigated the impact of time given by PU’s to SU’s for data transfer. For performing the above task, a simulator is designed in MATLAB-7.01. The results show that the performance of routing protocols improves significantly as the number of PUs and allowable time given by PU’s to SU’s increases.

Due to the broad prospect of Vehicular Ad hoc Networks (VANETS) on road safety, traffic management and entertainment applications, data transmission technology of VANETS has been became the focus of the study. However, dynamic topology changes and vehicle move speed of VANETS results in link break of workshop communication, which reduces the reliability of the link. This paper presents the cooperative communication mechanism to improve the reliability of the communication link and ease the wireless road deterioration caused by vehicle movement. Based on the ADHOC MAC scheme, cooperative ADHOC MAC scheme is proposed referred as COOMACP. In COOMACP, once the data packet unsuccessfully transmitted to the destination node, the neighbor nodes will use the unoccupied slot to offer cooperative pattern and retransmit data. Through the theoretical analysis, the probability of cooperative mode is proposed. Theoretical analysis and simulation results show that COOMACP improves the probability of successful transmission of data packets and improves the system throughput.

The average symbol error probability (ASEP) of a mobile-to-mobile (M2M) system employing maximal ratio combining (MRC) over N-Nakagami fading channels is investigated in this paper. The characteristic function (CF) of the signal-to-noise ratio (SNR) at the MRC output is used to derive exact ASEP expressions for several q-ary modulation schemes, including phase shift keying (PSK) modulation, quadrature amplitude modulation (QAM), and pulse amplitude modulation (PAM). Then the ASEP performance under different channel conditions is evaluated through numerical simulation to verify the analysis. These results show that the performance of the MRC M2M system is improved as the number of diversity branches or the fading coefficient is increased. Conversely, performance is degraded as the number of cascaded components is increased.

Hex-Cell network is one of modern interconnection networks in which the nodes are connected with each other in hexagonal topology. This topology gives its network an attractive characteristic represented by expandability due toits recursive structure. In this paper a new routing algorithm for Hex-Cell network is developed depending on new addressing mode.According to this mode, each node in the Hex-Cell is identified by its level and the node number in that level.Consequently, there is no need to readdress the nodes when extra level or levels are added to the topology.Several experiments were conducted to evaluate the proposed algorithm and compare it with other routing algorithms. The results showed the superiority of the new routing algorithm over the other routing algorithms for Hex-Cell in terms of execution time.

It is necessary to reduce the consumption of network node energy and the network load for solving the query design for routing algorithm in wireless sensor network, thus this article presents query gain routing algorithms and load balancing mechanism. This algorithm selects routing node by querying the routing information of gain matrix according to the successful record of historical query. The load balancing mechanism queries the energy information, which records node in the routing process and transfers load to balance the energy consumption of each node in the query path. This algorithm is able to effectively aware routing load to reduce the network energy consumption and avoid the data collision. The experimental result shows that compared with other query routing strategy, the query gain routing can increase the success rate of query under the condition of reducing the node energy consumption, but the load balancing mechanism can reduce the energy consumption of query gain routing further and prolong the network life cycle more effectively.

With the rapid development of communication technology, mobile communication network integrates with internet constantly and forms mobile internet. The mobile communication system tend to be IP-based, mobile terminals tend to be intelligent, application of APP becomes more and more popular, intelligent applications make people's life more convenient. But, there are huge security threats hidden in current mobile communication, the security of users’ privacy information in mobile communication, such as users’ identity, location information, business routing, arouse more and more widely attention. This paper introduces related researches and problems of users’ privacy protection in current mobile communication, and discusses to apply the idea of active defense to the security mechanism for better protection of users’ privacy information.

This paper analyses service objects and functional positioning of port logistics information service platform firstly. The architecture of port logistics information service platform upon cloud computing is proposed Based on the research of the concept and service mode of cloud computing. The system configuration and function implementation on the basis of Windows Azure Platform is further discussed in detail.

IEEE 802.11 wireless local area networks (WLAN) have been widely deployed, and many applications are implemented on WLAN. As one of the interesting wireless services, wireless voice over internet protocol (VoIP) can provide low-cost real-time voice service to mobile users. But the IEEE 802.11 wireless network cannot satisfy the QoS of VoIP. The delay during handoff process can last up to 1 second. Applications with delay restraint like VoIP will drop the call when the delay is more than 50 ms. Therefore this paper analyzed the delay made by the handoff process, and proposed a pre-scanning fast handoff scheme. This fast handoff scheme is based on selective scanning and caching. It can predict the next AP for STAs and use pre-scanning before the handoff is triggered. Simulations on OPNET show this proposed scheme can reduce the average handoff delay to 23.45 ms and avoid some unnecessary handoffs. The pre-scanning fast handoff scheme is feasible and economical according to its performance in the handoff process.

This paper presents a novel approach for constructing structured regular QC-LDPC codes based on a special type of combinatorial designs,known as the balanced incomplete block design (BIBD).The code design approach based on the technology of block cyclic shift and dispertion (BCSD) for correcting erasure-bursts over the binary bursts erasure channel (BBEC). Furthermore, the Tanner graph of the constructed codes is free of 4-cycles, hence the BCSD-QC-LDPC codes have girth at least 6. The simulation results show that the BCSD-QC-LDPC codes perform well over the BBEC channel with iterative message-passing decoding.

Since wireless sensor networks have limited energy resources, energy efficiency and reliable data transmission rate are key issues in designing the topology. In this paper, a new root protocol NCQ-DD is proposed in order to solve the issue of limited performance of DD in wireless sensor networks. NCQ-DD greatly improves traditional DD protocol by utilizing random linear network coding technology and service quality perception. Experimental results show that the new routing protocol can save network bandwidth resources and sensor node’s energy, improve data transmission rate and ensure reliable transmission, thus increasing the lifetime of sensor networks.