摘要：The Mobile Commerce (m-commerce) becomes very powerful tool in the competitive business markets. Companies started to use this technology to attract their customers and catch their attention. Usage of Mobile commerce applications spreaded around different countries and became very popular. Different communication protocols and security techniques are designed for business use of m-commerce. Mobile Commerce, likewise the e-commerce brought significant difference in the market. People start to use this technology by feeling the freedom of having transactions at anywhere and anytime. However, consumers face lot of difficulties while using this technology which is consumer-based or service provider based. This research exposes the impact of determinants that influences mobile commerce application users’ attitudes by classifying and investigating the internal and external variables in a case study of Cyprus Research Centre.
摘要：Many wireless applications are deployed and available to customers via their mobile phones. Variety of these applications and services are based on determination of the current or future location of mobile user. Location based services (LBS) are one of the vital applications which are subdivided into two main categories: economical category and public category. Economic applications include mobile marketing, entertainment and tracking applications. Whereas, emergency cases, safety, traffic management, Muslims’ applications and public information applications are sort of public applications. The first part of the paper presents a new proposed system with developed procedure to recreate public and economic applications with high positioning accuracy and good authentication of users’ data. The developed system is created to enhance both location based services and network allocation resources within mobile network platform using either normal or GPS supported mobile equipment. The second part of the paper introduces future location prediction of mobile user dependent applications. New algorithm is developed depending on utilizing both intra-cell Movement Pattern algorithm (ICMP) [1] and hybrid uplink time Difference of Arrival and Assisted GPS technique (UTDOA_AGPS) [2]. It has been noticed that ICMP algorithm outperforms other future location prediction algorithms with high precision and within suitable time (less than 220) msec. However, UTDOA_AGPS guarantees high precession of mobile user independent of the surrounding environment. The proposed technique is used to enhance reliability and efficiency of location based services using cellular network platform.
摘要：A non web based rainfall data base of the South Western Nigeria was designed with the objective of providing user friendly source of data for the region. The study used the rainfall data obtained from the Institute of Agricultural Research and Training, Ibadan and it covers from year 1985 to 2007. The study uses Microsoft Access (2003) for data base creation as well as Visual Basic 6.0 (VB 6.0) for interface creation. The program developed could dynamically accommodate regular and new user of the data and could be upgraded for regular update of the data. The results of the programme evaluation showed that the data obtained from the database and the manual ones are the same.
摘要：Mobile ad hoc networks have a wide range of application usage today, due to its great services, easy installation and configuration, and its other distinctive characteristics. In contrast, the attackers also have developed their own way to disrupt MANET normal operations. Many techniques, approaches and protocols have proposed to support Mobile Ad hoc Network (MANET) survivability in adversarial environment. Survivable of routing operations is the key aspects of the challenge in MANETs because most of destructive attacks classified as active attacks and all are intent to attack MANET routing operation to prevent it from providing it services in a right time. In this paper, we will discuss the most effective and practical initiatives have designed to keep MANET survive in an adversarial environment and how it supporting MANET availability.
摘要：In WLANs, stations sharing a common wireless channel are governed by IEEE 802.11 protocol. Many conscious studies have been conducted to utilize this precious medium efficiently. However, most of these studies have been done either under assumption of idealistic channel condition or with unlimited retransmitting number. This paper is devoted to investigate influence of limited retransmissions and error level in the utilizing channel on the network throughput, probability of packet dropping and time to drop a packet. The results show that for networks using basic access mechanism the throughput is suppressed with increasing amount of errors in the transmitting channel over all the range of the retry limit. It is also quite sensitive to the size of the network. On the other side, the networks using four-way handshaking mechanism has a good immunity against the error over the available range of retry limits. Also the throughput is unchangeable with size of the network over the range of retransmission limits. However, the throughput does not change with retry limits when it exceeds the maximum number of the backoff stage in both DCF’s mechanisms. In both mechanisms the probability of dropping a packet is a decreasing function with number of retransmissions and the time to drop a packet in the queue of a station is a strong function to the number of retry limit, size of the network, the utilizing medium access mechanism and amount of errors in the channel.
摘要：To protect the systems exposed to the Internet against attacks, a security system with the capability to engage with the attacker is needed. There have been attempts to model the engagement/interactions between users, both benign and malicious, and network administrators as games. Building on such works, we present a game model which is generic enough to capture various modes of such interactions. The model facilitates stochastic games with imperfect information. The information is imperfect due to erroneous sensors leading to incorrect perception of the current state by the players. To model this error in perception distributed over other multiple states, we use Euclidean distances between the outputs of the sensors. We build a 5-state game to represent the interaction of the administrator with the user. The states correspond to 1) the user being out of the system in the Internet, and after logging in to the system;2) having low privileges;3) having high privileges;4) when he successfully attacks and 5) gets trapped in a honeypot by the administrator. Each state has its own action set. We present the game with a distinct perceived action set corresponding to each distinct information set of these states. The model facilitates stochastic games with imperfect information. The imperfect information is due to erroneous sensors leading to incorrect perception of the current state by the players. To model this error in perception distributed over the states, we use Euclidean distances between outputs of the sensors. A numerical simulation of an example game is presented to show the evaluation of rewards to the players and the preferred strategies. We also present the conditions for formulating the strategies when dealing with more than one attacker and making collaborations.
摘要：The paper analyzes power spectral density (PSD) of orthogonal pulse-based signals for time hopping ultra wideband (TH-UWB) systems. Our extensive studies show that the PSD of these signals not only depends on the time dithering code and the modulation schemes, but also on the energy spectral density (ESD) of orthogonal pulses. The different order orthogonal pulses provide different ESD which changes the shape of continuous spectral component with symbols. We show that orthogonal pulse-based signals reduce the dynamic range of amplitude of discrete spectral components. Further, we reduce the dynamic range by adopting longer TH code over orthogonal pulse-based signals. As a result, UWB system performance improves with average transmitted power. The theoretical analysis of PSD of orthogonal pulse-based TH-UWB signal is provided in details and verified through simulation results.
摘要：The fundamental operating principle of a Class F power amplifier and the factors aiding or affecting Class F performance were explicated previously. A Class F power amplifier design which satisfies WCDMA specifications is explained in this paper. The Class F amplifier was designed by employing Motorola’s LDMOS (Laterally Diffused Metal Oxide Semiconductor) transistor models and we simulated its performance by means of ADS. A variety of procedures were applied in the process of designing Class F amplifier, namely, DC simulation, bias point selection, source-pull and load-pull characterization, input and output matching circuit design and the design of suitable harmonic traps, which are explained here.
摘要：Energy efficiency and enhanced backbone capacity is obtained by exploiting the geometric orientation of cooperative nodes in wireless sensor network. The cooperative communication in wireless sensor networks (WSN) gives us leverage to get the inherent advantages of its random node’s locations and the direction of the data flow. Depending on the channel conditions and the transmission distance, the number of cooperative nodes is selected, that participate in an energy efficient transmission/reception. Simulation results show that increasing the cooperative receive diversity, decreases the energy consumption per bit in cooperative communications. It has also been shown that the network backbone capacity can be increased by controlled displacement of antennas at base station at the expense of energy per bit.
摘要：In this paper is demonstrated a method for reduction of integer factorization problem to an analysis of a sequence of modular elliptic equations. As a result, the paper provides a non-deterministic algorithm that computes a factor of a semi-prime integer n=pq, where prime factors p and q are unknown. The proposed algorithm is based on counting points on a sequence of at least four elliptic curves y2=x(x2+b2)(modn) , where b is a control parameter. Although in the worst case, for some n the number of required values of parameter b that must be considered (the number of basic steps of the algorithm) substantially exceeds four, hundreds of computer experiments indicate that the average number of the basic steps does not exceed six. These experiments also confirm all important facts discussed in this paper.
摘要：Topological design of service networks is studied in the paper. Quantitative model and algorithm minimizing cost of processing and delivery is described. Algorithm solving combinatorial problem of optimal design based on binary partitioning, a parametric search and dynamic programming optimization of a binary tree is described and demonstrated in numeric example.
摘要：Protecting networks against different types of attacks is one of most important posed issue into the network and information security domains. This problem on Wireless Sensor Networks (WSNs), in attention to their special properties, has more importance. Now, there are some of proposed solutions to protect Wireless Sensor Networks (WSNs) against different types of intrusions;but no one of them has a comprehensive view to this problem and they are usually designed in single-purpose;but, the proposed design in this paper has been a comprehensive view to this issue by presenting a complete architecture of Intrusion Detection System (IDS). The main contribution of this architecture is its modularity and flexibility;i.e. it is designed and applicable, in four steps on intrusion detection process, consistent to the application domain and its required security level. Focus of this paper is on the heterogeneous WSNs and network-based IDS, by designing and deploying the Wireless Sensor Network wide level Intrusion Detection System (WSNIDS) on the base station (sink). Finally, this paper has been designed a questionnaire to verify its idea, by using the acquired results from analyzing the questionnaires.
摘要：A fractal model containing n-series of spheres and ellipses with corresponding radii, and surrounded by a thin film of adsorbed water has been developed. This model is more suitable to real sedimentary rocks because it not only allows for varying grain sizes and number of fractions, but also takes into consideration the influence of double electrical layers on the physical properties of sediments. Ellipsoid fractal models provide mathematical proof of the phenomenon of supercapillary conductivity observed in laboratory measurements. Using the parameters of the fractal models several petrophysical parameters can be calculated, namely resistivity porosity, and permeability. In a case study, layers with different resistivity were identified on a section taken from a TDEM survey, and porosity and salinity of water bearing layers were estimated using the fractal model. Estimated permeability using the fractal model showed good agreement with other methods.
摘要：In this paper, we propose extraction of signals correlated with noise in which they are buried. Proposed extraction method uses no a-priori information on the buried signal and works independently of the nature of noise, correlated or not with the signal, colored or white, Gaussian or not, and locations of its spectral extent. Extraction of buried correlated signals is achieved without averaging in the time or frequency domain.
摘要：This paper analyzes mathematically the crucial aspects of signal processing in a Multi-Band (MB) Orthogonal Frequency Division Multiplexing (OFDM) based system considering Ultra-Wideband (UWB) channel environment. In the process of analysis, it emphasizes the significant features of UWB receiver design in comparison with ‘conventional’ narrow-band system. The analysis shows that the high dispersive nature of a frequency selective UWB channel effects the design of different signal processing blocks like pre-select filter, low noise amplifier (LNA) and analog-to-digital (A/D) converter in the receiver front end. The characteristic functions of each of these stages are now dominated by the channel characteristics and it needs to be modified accordingly. This analysis is extended further with the study of frequency offset error and its correction. The unbiased Cramer Rao Lower Bound (CRLB) of estimation error is calculated and supported by computer simulation. The performance of an MB-OFDM system with frequency offset correction in terms of Bit-Error-Rate (BER) is also reported.
摘要：This paper presents virtual clusters based proportional fairness and resource allocation scheme for Localized Single Carrier Frequency Division Multiple Access (L-SC-FDMA). L-SC-FDMA has been selected as the uplink transmission scheme in 3GPP Long Term Evolution (LTE) due to its low Peak to Average Power Ratio (PAPR) over OFDMA in general and high rate-sum capacity over Interleaved SC-FDMA in particular. Virtual cluster-based proportional fairness (VCPF) scheduler exploits the link adaptation information available at MAC layer to form virtual clusters. The distributed proportional fairness scheduler ensures a minimum throughput for all users in the coverage area by assigning contiguous RBs, proportional to the throughput and the number of users in a particular cluster or group. Simulations have been performed using practical scenario of uniformly distributed users in Rayleigh faded coverage area and design formulas have been devised for network planning to get the best possible fairness with promising level of quality of service (QoS).
摘要：Compared with the flat architecture in the design of sensor networks, the hierarchical architecture gains much attractive for the reason of scalability, management and energy efficiency. In order to distribute the energy evenly, nodes act the cluster head in some orders. The existing approaches don’t pay a critical attention to the overhead during the role rotations. And the duration of a round is a priori, which is very application-specific. An energy-aware hierarchical architecture design scheme is put forward in this paper, namely, Adaptive Minimum Rotational Cost (AMRC) cluster formation scheme. The decision of beginning a new round is made adaptively by the cluster head itself. It combines the dynamic and static advantages in the clustering architecture. The simulation results demonstrate AMRC outperforms some other clustering protocols in many aspects.
摘要：In this paper, we present drive test results for mobile WiMAX system for desert and cosmopolitan terrains where there are few studies reported in the literature. The extensive measurement is performed in the framework of the physical performance of the WiMAX technology which is often considered as a 4G system. Path loss model is fitted for the collected data. The work is unique in the sense that most empirical channel models are produced in regions where the environments (weather, buildings, vegetation, among others) are quite different from the desert terrains that are considered in this study. We also show that shadowing is truly lognormal in dB and the standard deviation values are calculated for the desert terrain from the measurement data. The measurements are collected using WiMAX BS station, with greenpacket dongle, and NEMO versatile outdoor drive test equipment to evaluate and characterize the performance of the system. The received signal strength indicators measured, are analyzed to complement network design and network optimization for regions where the popular models may not be accurate.
摘要：The use of technology has increased vastly and today computer systems are interconnected via different communication medium. The use of distributed systems in our day to day activities has solely improved with data distributions. This is because distributed systems enable nodes to organise and allow their resources to be used among the connected systems or devices that make people to be integrated with geographically distributed computing facilities. The distributed systems may lead to lack of service availability due to multiple system failures on multiple failure points. This article highlights the different fault tolerance mechanism in distributed systems used to prevent multiple system failures on multiple failure points by considering replication, high redundancy and high availability of the distributed services.
摘要：Optical Packet Switching (OPS) and transmission networks based on Wavelength Division Multiplexing (WDM) have been increasingly deployed in the Internet infrastructure over the last decade in order to meet the huge increasing demand for bandwidth. Several different technologies have been developed for optical packet switching such as space switches, broadcast-and-select, input buffered switches and output buffered switches. These architectures vary based on several parameters such as the way of optical buffering, the placement of optical buffers, the way of solving the external blocking inherited from switching technologies in general and the components used to implement the WDM. This study surveys most of the exiting optical packet switching architectures. A simulation-based comparison of input buffered and output buffered architectures is presented. The performance analysis of the selected two architectures is derived using simulation program and compared at different scenarios. We found that the output buffered architectures give better performance than input buffered architectures. The simulation results show that the-broadcast-and-select architecture is attractive in terms that it has lees number of components compared to other switches.
摘要：This paper presents a scheduling scheme for packet transmission in OFDM wireless system with adaptive techniques.The concept of efficient transmission capacity is introduced to make scheduling decisions based on channel conditions.We present a mathematical technique for determining the optimum transmission rate, packet size, Forward Error Correction and constellation size in wireless system that have multi-carriers for OFDM modulation in downlink transmission. The throughput is defined as the number of bits per second correctly received. Trade-offs between the throughput and the operation range are observed, and equations are derived for the optimal choice of the design variables. These parameters are SNR dependent and can be adapted dynamically in response to the mobility of a wireless data terminal. We also look at the joint optimization problem involving all the design parameters together. In the low SNR region it is achieved by adapting the symbol rate so that the received SNR per symbol stays at some preferred value. Finally, we give a characterization of the optimal parameter values as functions of received SNR Simulation results are given to demonstrate efficiency of the scheme.
摘要：Optimal resource allocation with an objective of maximizing the system capacity is an NP-hard problem in multihop cellular networks. Hence, different heuristic algorithms have been developed over the years that would improve the network system capacity. In this paper, a novel cluster-based architecture is proposed for a two-hop cellular network whereby the transmission distance between any communicating pair is restricted to half the cell radius. In this design, a given radio resource is used by two simultaneously communicating pairs in every hexagonal cell, but for only half the time slot period. The characteristic feature of this cluster-based design is that it enables a frequency reuse ratio of one. The proposed hierarchical system is analyzed and tested under realistic propagation conditions including lognormal shadowing. It has been observed that the system capacity of a cluster-based design is 2.5 times that obtained from the single-hop cellular system with no relaying. In addition, the cluster-based design achieves higher capacity compared to state-of-the-art two-hop algorithms. This is an important finding since the hierarchical cluster-based approach has fewer degrees of freedom in the selection of the routing path for the end-to-end connection. Practical routing algorithms should be able to benefit from this.
摘要：In multimedia cellular networks, when a Mobile Host requests multimedia services, it may experience hand-offs to several cells before the request is completely served. If a target cell cannot provide adequate bandwidth for a service request, instead of directly dropping the request, the MH is put into the handoff queue and hopefully the requested bandwidth can be satisfied by later released bandwidth. Obviously, it is important to properly assign priorities for queued handoff of MHs based on their inborn dynamics to avoid unnecessary dropping. In this paper, we present a dynamic handoff priority adjustment scheme which applied a handoff queuing scheme to dynamically adjust handoff priority based on receiving signal strength, service class, and mobility of Mobile Hosts. In addition, idle bandwidth reserved by inactive MHs is reallocated to urgent handoff MHs to reduce the call dropping probability. The goal of the proposed dynamic handoff priority adjustment scheme is to further reduce call dropping probability while still maintaining high bandwidth utilization and acceptable call blocking probability on multimedia cellular networks.
摘要：Channel measurement and modeling is an important issue when designing ultra wideband (UWB) communication systems. A Precise model of the channel response is inevitable for designing an ultra wideband telecommunication system. In this article signal propagation in indoor environment and LOS condition is evaluated and the appropriate model of this scenario is presented. Parameters such as the power delay profile, mean excess delay, delay spread, “NP10dB” are analyzed and simulated. Based on analysis results, the proposed model is presented. This model is based on Two-cluster approach but its average power delay profile is described with power function and cluster time of arrival is modeled by the modified exponential distribution. Finally UWB channel parameters of proposed model, Saleh and Valenzuela (S-V) and Two-cluster models are compared. Measurement and simulation results show that considerable improvement for mean excess delay, delay spread and “NP10dB” of proposed model comparing with S-V and Two-cluster model, this means the channel is better described, which mean the channel is described more precisely.
摘要：Data security in wireless network has posed as a threat that has stuck to the core of data communication from point A to point B. There have been a variety of security issues raised in wired and wireless networks and security specialists proposed a variety of solutions. The proposed security solutions in wired networks could not be successfully implemented in wireless networks to identify, authenticate and authorize users due to infrastructural and working principles of wireless networks. Data on wireless network are much exposed to threats because the network is been broadcasted unlike a wired network. Researchers have proposed WEP and WPA to provide security in wireless networks. This research is going to compare the WEP and WPA mechanism for better understanding of their working principles and security bugs.
摘要：This paper presents an effective way to enhance power analysis attacks on AES hardware implementations. The proposed attack adopts hamming difference of intermediate results as power mode. It arranges plaintext inputs to differentiate power traces to the maximal probability. A simulation-based AES ASIC implementation and experimental platform are built. Various power attacks are conducted on our AES hardware implementation. Unlike on software implementations, conventional power attacks on hardware implementations may not succeed or require more computations. However, the method we proposed effectively improves the success rate using acceptable number of power traces and fewer computations. Furthermore from experimental data, the correlation factor between the hamming distance of key guesses and the difference of DPA traces has the value 0.9233 to validate power model and attack results.
摘要：In this paper, a two step secure spectrum sensing algorithm is proposed for cognitive radio networks. In this algorithm, the sensing results of secondary users are pre-filtered and applying fuzzy logic, so, the overall sensing performance of the network is improved. To determine pre-filter parameters, statistical parameters of the sensing results are used to remove those sensing results which are far from the majority sensing results. However, to obtain a better performance in the spectrum sensing, we propose a fuzzy logic to nullify the effects of malicious users who transmit false sensing data to the fusion center. We further propose a Fuzzy Trust Level for each user as to weight the sensing result of the corresponding user before combining all sensing results in the fusion center. Simulation results demonstrate that our proposed algorithm yield significant improvement in the performance of the spectrum sensing and identifying malicious users.
摘要：Energy consumption in data centers has grown out of proportion in regard to the state of energy that’s available in the universe. Technology has improved services and its application. The need for eco-friendly energy and increase in data centers performance brought about Green Computing into the energy consumption of data centers. Information technology has grown and eaten deep into the society that almost all the sectors if not all are dependent on information technology to move on. The consumption of power has increased greatly. In this research paper the techniques for optimizing energy in data centers for Green Computing would be discussed. This study intends to expose the limitations of existing security solutions for securing data centers by taking into consideration of limitations of existing security frameworks that cannot enhance the security of data centers.
摘要：As the development of web service (WS), applications based on web services (WS), which are convent and platform-independent, have become increasingly popular in recent years. However, how to identify, generate and compose services has become an open issue recently. This paper proposes a method based on program slicing to realize the generation and composition of web services. This paper introduces the method about how to generate a WSDL file and a SOAP message from source codes as well as the theory of function dependence graph (FDG). In addition, this paper gives the way to generate a proxy service for each service, which allows users to easily call a service. The results of experiments show that our generation and composition methods of WS are feasible and flexible.
摘要：Ad hoc network (MANET) is a collection of mobile nodes that can communicate with each other without using any fixed infrastructure. To support multimedia applications such as video and voice MANETs require an efficient routing protocol and quality of service (QoS) mechanism. Node-Disjoint Multipath Routing Protocol (NDMR) is a practical protocol in MANETs: it reduces routing overhead dramatically and achieves multiple node-disjoint routing paths. QoS support in MANETs is an important issue as best-effort routing is not efficient for supporting multimedia applications. This paper presents a novel adaptation of NDMR, QoS enabled NDMR, which introduces agent-based SLA management. This enhancement allows for the intelligent selection of node-disjoint routes based on network conditions, thus fulfilling the QoS requirements of Service Level Agreements (SLAs).
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