Earticle

The existence of malicious secondary users will bring damage to the performance of cooperative spectrum sensing and spectrum access in cognitive radio networks, so effectively curbing malicious behavior of secondary users become the key to success for cooperative spectrum sensing mechanism. Inspired by economics of repeated game theory, a trust game model and algorithm of distributed cooperative spectrum sensing oriented to malicious secondary users named FRTrust is proposed. In FRTrust, the reputation status is used to describe the performance of a secondary user in cooperative spectrum sensing process. It encourages secondary users to choose positive and honest behavior strategies for greater and long term benefits. Simultaneously, a ‘differentiation’ punishment mechanism is presented to respond malicious behaviors of secondary users. By this way, the ‘first offender’ secondary users and the ‘recidivist' secondary users can be distinguished effectively. If a secondary user departs from the normal times in its life period, it will be punished superimposed. Simulation results show that the FRTrust algorithm can encourage secondary users to participate in spectrum sensing in a cooperative attitude, improve the transaction success ratio of cooperative spectrum sensing, and guarantee the fairness and spectrum access performance for cognitive radio networks.

In this article, a dual band patch antenna is achieved by introducing T-slot in circular disk with small frequency ratio. It is theoretically investigated using equivalent circuit theory concept. The resonance frequency is found to be 1.84 and 2.02 GHz suitable for DCS-1800, PCS-1900 and IMT-2000 applications. The measured bandwidths at lower and upper resonances are found to be 6.59% and 6.89% respectively for proposed antenna specifications. The effect of slots dimension in the patch is studied. The frequency ratio is found to be 1.09. The maximum gain of the proposed antenna is found to be 6.52 dBi whereas efficiency is found to be 62.17% and 76.42% at lower and upper resonance frequencies respectively. The theoretical results are compared with simulated and measured results and they are in good agreement.

A channel parameter estimation method adapted to a wireless communication system is proposed. The wireless communication system includes a transmitter and a receiver. The proposed method includes following steps. The transmitter transmits a plurality of pilot signals to the receiver by using one of a plurality of preconfigured sparse random pilot patterns. The receiver receives the pilot signals, performs a channel parameter estimation on the pilot signals by using a compressive sensing algorithm to obtain a multipath channel number, and selects a pilot pattern for a next cycle among the preconfigured sparse random pilot patterns according to the multipath channel number and a current pilot number. Additionally, the receiver transmits feedback information associated with the selected pilot pattern to the transmitter.

Weight based clustering has become the mainstream clustering algorithm in low-speed Ad hoc networks because of its excellent cluster stability. However, due to the dynamic topology changing in high-speed Ad hoc network, the cluster stability (network stability) decreased and the cluster maintenance costs increased sharply. To solve the problem, we propose a dynamic entropy based combination weighted clustering approach (DECW). First, according to the history messages of an evaluation node in the network, the upper bound and the lower bound value of each clustering index will be recorded, so the information entropy deviation of the indexes and dynamic entropy weight of each node can be obtained. After, the linear combination weights set of evaluation nodes is modeled as the second-order norm game , and the weight vector deviation is minimized as the optimization goal to get the multi-node dynamic entropy weights. In the cluster maintenance, a new Monte Carlo optimization is proposed to avoid the frequent cluster-heads (CHs) replacement induced of high node mobility of. Simulation results reveal that the proposed approach has the better adaptability in high-speed mobile environment.

In this modern wireless technology Multicarrier communication is one of the more suitable and reliable communication technique. Orthogonal Frequency Division Multiplexing (OFDM) is used as modulation technique in multicarrier communication. The present paper gives an overview of OFDM and the various Channel Estimation techniques used in OFDM. The results implemented in MATLAB gives the performance of LS and the MMSE channel estimators for an OFDM system based on the parameters of BER and MSE. Paper also describes the Delayed feedback MIMO OFDM channel estimation performance of LS and LMMSE and DFT based channel estimation technique for LS-linear and MMSE estimator. BPSK and 16-QAM modulation techniques are used.

To recognize abnormal traffic in network, so as to perceive the illicit behavior in network, carry out scientific and effective management, and ensure the network security, we extracted the abnormal network traffic features and proposed an abnormal network traffic recognition method based on optimized Back Propagation Artificial Neural Networks (BP ANN). The experimental results indicate that, although the training time is longer, but the accuracy rate of BP ANN in abnormal network traffic identification is superior to other methods. And the convergence rate of optimized BP ANN model is significantly faster than traditional BP ANN model.

LTE Advanced has brought revolution in the field of wireless communication technology by providing high data rates of up to 1Gbps. There is a need of increased data rates these days that may support the delivery of richer mobile multimedia contents to the end users. Rate adaptation is one of the key enabling technology in the success of LTE Advanced that has cited attraction of academia and research communities in recent years. Rate adaptation is the determination of the optimal data transmission rate most suitable for current prevailing wireless channel conditions. To maximize the performance of wireless devices, it is important to select the best appropriate rate hence rate adaptation algorithms (RAA’s) are required. This work includes a comprehensive survey on various types of RAA’s in LTE-A for effective resource utilization. Depending on the channel conditions various performance parameters such as throughput, power consumption and latency have been studied. It has been observed from the literature survey that many proposals have been published on LTE-A. Sill there is a need of research to be carried in LTE-A as this technology is not fully matured so open issues and future scope are also raised in this work.

DVB-H is developed to broadcast digital videos to mobile handsets, but data loss is a concern due to the wireless broadcasting nature. In this paper, take WiMAX as an IP-based wireless network to recover the loss packets in DVB-H, and take E-WP based on network coding as the encoding packet selection algorithm. Furthermore, a prioritized scheme EWP-PNC based on E-WP packet selection algorithm is proposed. In this scheme, take a base station in WiMAX as encoding node to encode any two packets that meet the encoding and decoding necessary and sufficient condition into an encoding recovery packet according to the current lost packet distribution, and calculate the benefit of each encoding packet to decide the final priority of all encoding packets. The goals of this scheme are to improve the lost packet recovery ratio and reduce the discarded packet ratio. According to the simulation results, the validity of this scheme is proved.

This paper analyzes several factors affecting the reliability of RS485 fieldbus communication, and then establishes the equivalent circuit model in order to solve bias resistor. The value range of bias resistor on the fieldbus is 556Ω~716Ω, which is determined by using the law of KCL and current limiting method. Furthermore the best value of bias resistor is derived about 670Ω for different unit loads based on the relationship between number of network nodes and the value of bias resistor, and the corresponding maximum network nodes of fieldbus are determined too. The research of this paper provides theoretical basis and engineering design guidance for the application of RS485 fieldbus.

Now-a-days vehicles are one of the most important parts of our life. We need them to cross distances in our everyday life. In this paper we discuss Vehicular Ad-Hoc Network (VANET) technology that can ensure the maintenance of traffic rules and regulation. By applying this technology we can save life, save time, corruption, vehicle security, avoid collision and so on. Vehicular Ad Hoc Network (VANET) is a part of Mobile Ad Hoc Network (MANET). Every node or vehicle can move freely and they will communicate each other by wireless technology in coverage. The main goal of this research is to study the existing routing protocols for ad-hoc network system and compared between AODV (Reactive) and DSDV (Proactive). We have studied different types of routing protocols such as topology based, position based, cluster based, geo-cast based and broadcast based. We have simulated and compared AODV (Reactive) and DSDV (Proactive) to find out their efficiency and detect their flaws.

In first stage of each microwave receiver there is Low Noise Amplifier (LNA) circuit, and this stage has important rule in quality factor of the receiver. This paper presents the design of LNA and development of low bias (VD=3V, ID=20mA), the LNA operating in frequency range 1.8-2.2GHz using a feedback circuit. Design System (ADS) 2012 tool was used for design and simulation, and each design was tuned to get the optimum value for NF, power gain (S21), input return loss (S11) and reverse isolation (S12). Simulation results have indicated that the S21 achieves 33.2515±0.4475dB over the wide frequency band of 1.8-2.2 GHz, the gain was almost flat over the whole band. Noise figure (NF) maintains is 0.4945±0.0565 dB, S12 < -47.089 dB and S11 < -16.126 dB in the entire band.

Cloud computing has firmly installed itself as a highly evolved concept for hosting and providing hardware and software resources across networks and the Internet. With rapidly emerging markets, cloud service providers have come up against a significant hurdle. Aspiring to remain firmly competitive in the long run, cloud service providers have realized that maintaining energy efficient controls in place without compromising performance is an aspect that cannot be ignored. With ever expanding sphere of cloud computing, energy demands for supporting computing resources and networks keep on growing. The high rate of demand for crucial energy needs is the salient point that keeps featuring in the horizon of almost every cloud computing service provider. Servers powering cloud computing services need to be supplied constantly with energy to support end users. To help ensure reduced energy consumption, we have examined the application of dynamic time schedule based server utilization method in our work. In this paper, we have applied this approach to cut back generation of heat by attempting to avoid server overloads. Our method involves different power consumption patterns which help saving energy costs. Consequently, carbon emission rates are kept under control. Thus, achieving a green cloud computing model is possible without additional cooling systems which would, in turn, have required more power to operate.

Opportunistic network realizes the communication between nodes by "storage-carry-forward" mode, the traditional routing algorithms can not be applied to the opportunistic network, to address the problems in opportunistic networks that nodes employing routing algorithms based on epidemic mechanism can't sense their neighboring nodes timely and many redundant data packets permeate through the network. This article proposes network routing algorithm based on an efficient opportunistic network. The algorithm is based on network coding method to solve routing problems, compared with existing routing method. NCRA method can handle dynamic route to improve the transmission success rate and reduce the transmission delay, reduce the routing overhead and short the buffer time, decrease the hops of overall opportunistic network.

This paper proposed a design scheme of wide band monopulse antenna system for the passive radar seeker (PRS) of anti-radiation missile (ARM). To save the installation space of the PRS, the conical conformal log periodic antennas (LPDA) are employed to form the monopulse antenna system. The specific implementation scheme of PRS based on the conically conformal monopulse antennas was designed and analyzed. A practical monopulse antenna system composed of two log periodic antennas was designed and fabricated over the operating frequency range of 1GHz to 8GHz. A loaded resistor with impedance equal to 50Ω is used to reduce the return loss at low frequency. The experimental results demonstrate that acceptable wide band impedance matching and port isolation for each fabricated antenna was achieved. Furthermore, the wide band sum and difference radiation patterns were formed, which validates the proposed conformal monopulse antenna design scheme for the PRS application.

Vehicular Ad hoc network is usually deployed for minimizing hand off latency and reducing packet loss. VANET consist of vehicle to vehicle and vehicle to infrastructure communication. Vehicles form infrastructure network with the access point and infrastructure less within themselves which is called ad-hoc network. The handoff latency and packet loss is reduced with the help of front and rear vehicles. In case of no front or rear vehicles this scenario comes to halt with both handoff latency and packet loss coming into picture. So in order to remove this flaw we create a pool of IP addresses where two access points share a particular group of IP address. This paper deals with this method described in detail.

In order to solve gateway deployment of geometry K center in the wireless network and improve the service quality of network, this paper proposes the gateway deployment solving model and algorithm. This paper transforms center problem of the geometric K into center problem of node K and solves problem. This paper proposes a gateway node alternative selection algorithm combination of network topology properties and maximum cover area related theory, and according to the relevant features select an alternative area, each alternative area abstract for a virtual node and is inserted into the original network topology structure, thus forming the new network topology. Solving new problem of the network topology and looking for the optimal deployment scheme use the improved genetic algorithm. The experimental results show that the model and algorithm proposed in this paper can well solve the wireless network gateway deployment problem of geometric K center and improve the network service quality.

In hierarchical structures determined by traditional routing protocols of wireless sensor networks, clustering is not structured and the networks prone to generate scatters, leading to some nodes die quickly. So this paper presents a cluster head preferred hierarchical clustering routing protocol based on G-Means (GHPHC). It uses G-Means algorithm to detect each clustering structure, so that each cluster is Gaussian distribution and it avoids the generation of scatters. At the same time, the cluster head preferred algorithm proposed in this paper gives the corresponding weight for each node of all clusters, thus select a suitable cluster head node for every cluster. Experimental results show that compared to traditional routing protocols, the death rate of nodes in a wireless sensor network which uses GHPHC protocol is more slow, and has a longer life cycle.

Due to the traditional overlay network QOS routing algorithm fails to consider the effects of the resource bottleneck on the routing selection, it results in the local congestion of the system. Therefore, this paper proposes a fair load-balancing QOS overlay routing F-LBQAR algorithm. The algorithm introduces the resource fairness index, sets up a new load-balancing utility function, and adopts the adaptive weighted method in the system’s load state to correct the weight restriction of QOS. The experimental results show that the algorithm in this paper can reduce the probability of network congestion caused by resources bottleneck and improve the QOS service success rate and the throughput of the system.

Mobile Adhoc network is a unique paradigm, which can be deployed in the environment where traditional wired network cannot be established due to its required features and their limitation. Transmission power is one of the major concern in case of MANETs. In this paper, effect changes in transmission power of the node has been analysed and its impact on network throughput has been investigated. The results achieved by various variations have been used for proposing the possible improvement in the network performance.

As we all know, virtual MIMO technology is an efficient way for energy saving in wireless sensor networks (WSNs). The present virtual MIMO communication strategies in WSNs depend on cluster heads collecting and forwarding source data, which causes big energy consumption. Aiming at this problem, we propose a new virtual-MIMO communication strategy based on cooperative group (CG) in this paper, called Group Collaboration MIMO (GCMIMO). GCMIMO clusters the WSN into several clusters. Each cluster is managed by two cluster heads, master cluster head (MCH) and vice cluster head (VCH). MCH divides the source nodes into several cooperative groups, every two nodes as a group. A CG can constitute a virtual dual-antenna transmitter for sending source data of both nodes directly. VCH and MCH are always seen as a CG, called master cooperative group (MCG), which can receive and forward the data from CGs of other clusters. Unlike the existing virtual MIMO communication strategy, GCMIMO doesn’t require the cluster heads collecting the data of the source nodes, which can reduce the times of source data transmission and improve the energy efficiency. In the simulation, we analyze the energy consumption in each communication phase of GCMIMO. The results indicate that GCMIMO can effectively decrease the energy consumption in data transmission and improve energy efficiency.

Optical network faces increasing challenges with the development of telecommunication demand. The fiber must carry much more transmission channels with higher optical power and transmission rate and it causes higher dispersion. At present, people have proposed some technical solution for this problem, including the dispersion compensation fiber (DCF), midpoint spectral inversion, dispersion managed transmission, chirped fiber grating (FBG), and so on. But algorithm with higher compensating efficiency is still needed. In this paper, we propose a modified algorithm to compensate the dispersion. With the simulation method, we obtained the characteristics of dispersion and dispersion slope with the variation of wavelength λ, and some useful conclusion has been acquired. With the increasing of wavelength λ, dispersion and its slope coefficient have different variation disciplinarian. From the simulation results, we can verify the conclusion that it needs to optimize the design of the structure of optical fiber if we want to compensate the dispersion and dispersion slope simultaneously.

Network coding in Mobile Ad hoc Network (MANET) is well-known in reducing delay, increasing throughput, and improving transmission reliability. While the data throughput capacity of MANETs is unknown, the scaling of capacity with the number of nodes has recently received increasing attention. This paper proposes a Complex Field Network Coding-based Multipath Routing in MANETs (CFNC-MRM). The performance of this routing method is studied using NS2 and evaluated in terms of the packet overhead, packet delivery ratio, and packet loss ratio when a packet is transmitted. Simulation shows that the CFNC-MRM is efficient, providing reliable multipath, promising and applicable in MANETs.

The characteristic of changing topology without a fixed infrastructure and lacking of any centralization is mobile adhoc networking (MANET).The communication between mobile nodes uses multihop wireless links. In the network; nodes act as router and forwarding data packets to other nodes behaving as intermediate node. Routing protocols plays an important role to facilitate communication within the network. In this paper we have compared different transmission power by varying antenna height. Simulation results shown in AODV routing protocol in term of the metrics: Throughput, Average end to end delay, Average jitter. The results are showing various changes due to change in the selected parameters, which are performance parameters of the network.

Integration of high-bandwidth Wi-Fi technology (e.g. 802.11p) and large-scale 4G network (e.g. Long-Term Evolution, shortly for LTE) could offset mutual limitations and provide vehicles ubiquitous Internet available. In this paper, we propose a novel vertical handover algorithm, and a feasible integrated architecture of heterogeneous 802.11p and LTE technologies through comparing Received Signal Strength (RSS) from both interfaces. We perform extensive simulations to investigate and analyze the performance of the proposed architecture using NS3. Results show that the proposed architecture behaves with the high throughput and low round trip time.

Coverage under certain conditions, with minimum sensor nodes to complete the coverage area and connectivity in wireless sensor networks has become a challenging one with the core issues. To this end, we propose a target associated with optimal coverage and connectivity control method using a double square to the target node within the planning area within the square, correlation model obtained by the sensor node and the destination node, for the entire coverage area is the use of probability determined to meet the minimum expectations of sensor nodes under cover conditions, and gives a probability model and the reasoning process connectivity square area outside edge node. Experimental results show that the error theoretical values with the simulation results of the method is less than 7.02%, to verify the effectiveness of the algorithm, reducing the allocation of network resources, you can better assess the performance of network coverage and connectivity.

Aiming at the problem of short lifetime and high cost in the on-orbit Servicing technology, a new type of automatic autonomous probe-cone docking mechanism used for microsatellite docking is proposed which can realize on-orbit special services. The structure of the mini docking mechanism is provided according to the design indices, and a virtual prototype model of the mini-type universal docking system is established by using MATLAB software. The dynamics modeling of the docking process is presented based on the virtual work principle. The simplified dynamic analysis model during the capture process is established. The dynamic characteristic analysis of the catching process is completed to research the influence of the key parameters, and the virtual prototype model of the docking device is established through ADAMS for further verifying the proposed design. The analysis shows that this mechanism has the good capacity of capture and separation process and energy absorption to reduce the impact during the docking process. And the simulation results meet the design demands of mini-type universal autonomous docking mechanism.

As an important indicator of evaluating network performance, network delay can reflect the transmission performance of the current path and also the service level provided by the opposite terminal host. In the paper, analysis is first conducted on the composition of network delay; besides, through Ping measuring method, Ping measuring network delay experiment is conducted on different destination hosts of local area network (LAN) and wide area network (WAN). Besides, the distribution features of network delay as time changes is analyzed, while the influence of data package (in terms of the size) on network delay will be explored in the paper. After the process, the definition, along with the distinguishing method of the self-similarity process is introduced, and self-similarity distinguishing is rendered on network delay through the variance-time plot. According to analysis result, network delay is featured by strong nonlinearity and self-similarity. Compared with LAN, WAN is endowed with higher long-range dependency.