摘要:This paper deals with modulation classification under the alpha-stable noise condition. Our goal is to discriminate orthogonal frequency division multiplexing (OFDM) modulation type from single carrier linear digital (SCLD) modulations in this scenario. Based on the new results concerning the generalized cyclostationarity of these signals in alpha-stable noise which are presented in this paper, we construct new modulation classification features without any priori information of carrier frequency and timing offset of the received signals, and use support vector machine (SVM) as classifier to discriminate OFDM from SCLD. Simulation results show that the recognition accuracy of the proposed algorithm can be up to 95% when the mix signal to noise ratio (MSNR) is up to ?1 dB.
摘要:In satellite communication systems, there are high power multichannel transmitters and wideband receivers that have shared RF antenna transmission lines because of: 1) large power level difference between the transmitted and received signal;2) limited frequency channels. The harmonics and Passive Intermodulation (PIM) Interference will be generated due to passive non-linearities in the high power transmission path. This can be a serious problem. This paper describes how to determine the signal levels and dominant mechanisms that are associated with non-linear dielectric behavior in this context. A novel measurement system for testing dielectric samples is described and measurement results are provided for commonly used microwave dielectrics.
摘要:Hierarchical Cellular Networks (HCN) offer more efficient channel utilization and better quality of service (QoS) under the high tele-traffic condition compared to the single-tier system. One of the important measures of QoS in HCN as in any single-tier system is the handoff dropping rate. Although the existing approaches such as guard channel and queuing can reduce forced termination probability, they also result in higher new call blocking probability. The channel sub-rating strategy has found to be an effective technique to reduce the handoff force termination probability while preserving the new call blocking probability in a single-tier system. In this paper, we propose a new call admission control scheme for HCN based on the channel sub-rating. Analytic models based on 1-D Markov process in microcell and 2-D Markov process in macrocell are developed. Experimental results show that our scheme achieves lower blocking and forced termination probabilities compared to the traditional guard channel scheme. The effect of channel sub-rating on the voice quality degradation is also studied. Results demonstrate that we can establish a good balance between the forced termination probability and the voice quality degradation by varying the number of sub-ratable full-rate channels.
摘要:This paper proposes a generation method of dithering signal based on Discrete Fourier Transform (DFT), which is not only independent with the input signal but also can decrease the quantization error of the Analog-to-Digital Converter (ADC). A detailed investigation of three typical dithering effects on the quantization error in ADC has been also presented in this paper, to highlight the advantages of the proposed reconstructed dithering signal. The simulation experiment and theoretical analysis illustrate that the reconstructed dithering signal based on DFT can improve the performance of ADC in comparison with traditional typical dithering signal.
摘要:Urinary incontinence is the most common health problem in aged people. Leaving incontinence events unmanaged will make a negative influence on the aged and the patient both mentally and physically. This paper presents a design and implementation of a real time wireless monitor system for urinary incontinence, which has been applied in two nursing homes in Beijing and Shanghai. We collect real time moisture information by using non-contact humidity sensor designed and manufactured by us. When urinary incontinence, the sensor will send alert to mobile device via Bluetooth. If got the alert, the mobile device will send the alert to relatives of the aged or disabled people and cloud computing platform, through which we can make this information managed and displayed and the paramedic can be informed about the alarm. This paper gives a brief introduction to the framework of this system, the design of the non-contact sensor, the transmission of wireless data and the results of tests.
摘要:Recently, there has been a rapid growing interest in new applications requiring quality of service (QoS) guarantees through wireless local area networks (WLAN). These demands have led to the introduction of new 802.11 standard series to enhance access medium supporting QoS for multimedia applications. However, some applications such as variable bit rate (VBR) traffic address some challenges in the hybrid coordination function (HCF) nominated to provide QoS. This paper presents a novel priority queuing model to analyze a medium access in the HCF controlled channel access (HCCA) mode. This model makes use of a MAP (Markovian Arrival Process)/PH (Phase Type)/1 queue with two types of jobs which are suitable to support VBR traffic. Using a MAP for traffic arrival process and PH distribution for service process, the inclusion of vacation period makes our analysis very general and comprehensive to support various types of practical traffic streams. The proposed priority queuing model is very useful to evaluate and enhance the performance of the scheduler and the admission controller in the HCCA mechanism.
摘要:The Biological Communication Behavior of the Left and the Right Brains have been constructed through the explanation of the phenomena of their specific part activities encompassing: Prefrontal, Frontal, Parietal, Central, Occipital and Parasagital which have been significantly tested in terms of their impacts in learning acceleration starting from Elementary School to University levels. This study is conducted by means of constructive approach and it employs both the quantitative and qualitative techniques. The result of the study shows that the biological communication of the left and the right brains are reliably tested scientifically from the viewpoint of science. The Problem Based Learning start from elementary school to university level of both social and science groups.
摘要:In this paper, performance of space-time trellis-code (STTC), space-time block code (STBC), and space-time trellis-code concatenated with space-time block code (STTC-STBC) for multi-carrier code-division multiple-access (MC-CDMA) system are studied. These schemes are considered by employing different detection techniques with various multi input multi output (MIMO) antenna diversity for different number of states in multi-path fading channel. The corresponding bit error rate (BER) is obtained using simulation for minimum mean-square error (MMSE), maximum-ratio combining (MRC), and equal-gain combining (EGC) receivers employing Viterbi decoder. The simulation results show that the STTC-STBC MC-CDMA system perform better compared to other schemes considered in this paper using MMSE detection and it is also observed that the performance can also be enhanced by increasing diversity using more transmitter and receiver antennas. However, this improvement in performance comes at the cost of increased computational complexity, which is calculated for different transmitting and receiving antennas.
摘要:It’s important for mobile operators to recommend new services. Traditional method is sending advertising messages to all mobile users. But most of users who are not interested in these services treat the messages as Spam. This paper presents a method to find potential customers who are likely to accept the services. This method searchs the maximum frequent itemsets which indicate potential customers’ features from a large data set of users’ information, then find potential customers from those maximum frequent itemsets by using a bayesian network classifier. Experimental results demonstrate this method can select users with higher accuracy.
摘要:Based on ServiceBSP model, a hierarchical resource load balancing algorithm with Multi-Agent is put forward in this paper which achieves the goal of dynamic load balancing and favorable Fault-tolerant. The algorithm calculates the load value according to the attributes of resource and scheduling tasks relies on the load value, while updating the load information dynamically depending on Multi-Agent. The method avoids frequent communications on load information. Furthermore, the paper introduces the function of agents, relations and communications among agents in details. Finally, by comparing response time and distribution of load using proposed method with other available methods such as without no load balancing and load balancing only giving regards to CPU, the experimental simulation shows that the load balancing based on Multi-Agent possesses superior performance on response time and load balancing.
摘要:This paper presents a novel algorithm for the gateway placement problem in Backbone Wireless Mesh Networks (BWMNs). Different from existing algorithms, the new algorithm incrementally identifies gateways and assigns mesh routers to identified gateways. The new algorithm can guarantee to find a feasible gateway placement satisfying Quality-of-Service (QoS) constraints, including delay constraint, relay load constraint and gateway capacity constraint. Experimental results show that its performance is as good as that of the best of existing algorithms for the gateway placement problem. But, the new algorithm can be used for BWMNs that do not form one connected component, and it is easy to implement and use.
摘要:The deployment of smart metering provides an immense amount of data for power grid operators and energy providers. By using this data, a more efficient and flexible power grid can be realized. However, this data also raises privacy concerns since it contains very sensitive information about customers. In this paper, we present a security and privacy-preserving metering scheme for the community customers, by utilizing the password authenticated key exchange (PAKE) protocol and Elliptic Curve Cryptosystem (ECC). The proposed scheme will protect the community network from possible malicious behavior, and security analysis is also given in the paper.
摘要:In this paper, we analyse the deployment of middlebox. For a given network information and policy requirements, an attempt is made to determine the optimal location of middlebox to achieve the best performance. In terms of the end-to-end delay as a performance optimization index, a distributed middlebox placement algorithm based on potential game is proposed. Through extensive simulations, it demonstrates that the proposed algorithm achieves the near-optimal solution, and the end-to-end delay decreases significantly.
摘要:Most countries have allocated 3G spectrum and are in the process of allocating advanced wireless services and 4G spectrum, both of which promise subscribers significantly faster broadband speeds. Operators anticipate that subscribers will adopt these services swiftly thereby justifying the large investments. Yet, why is it the case that only two countries in the world have more 3G than 2G subscribers? This study examines the drivers behind 3G diffusion using linear probability models and qualitative choice (logit) analysis. Time series diffusion models show that diffusion patterns follow an s-curve pattern, favoring the Gompertz curve.
摘要:We introduce a model for provable data possession (PDP) which allows a client that has stored data at an untrusted server to verify that the server possesses the original data without retrieving it. In a previous work, Ateniese et al. proposed a remote data integrity checking protocol that supports data partial dynamics. In this paper, we present a new remote data possession checking protocol which allows an unlimited number of file integrity verifications and efficiently supports dynamic operations, such as data modification, deletion, insertion and append. The proposed protocol supports public verifiability. In addition, the proposed protocol does not leak any private information to third-party verifiers. Through a specific analysis, we show the correctness and security of the protocol. After that, we demonstrate the proposed protocol has a good performance.
摘要:A simple on-chip automatic frequency tuning circuit is proposed. The tuning circuit is modified from voltage-controlled filter (VCF) frequency tuning circuit. We utilize an operational transconductance amplifier and a capacitor to from a single-time constant (STC) circuit which can produce a controllable delay time clock to tune the frequency of the filter. It can efficiently reduce the deviations in the 3 dB bandwidth from the variations of PVT (Process, Voltage and Temperature). The design of the STC circuit is simpler than VCF and it has less chip area. The chip has been implanted using TCMC 0.35 μm CMOS technology and the power consumption is less than 9.05 mW.
摘要:To fully utilize the diversity of multi-radio, a new parallel transmission method for wireless mesh network is proposed. Compared with conventional packet transmission which follows “one flow on one radio”, it uses the radio diversity to transmit the packets on different radios simultaneously. Three components are presented to achieve parallel-transmission, which are control module, selection module and schedule module. A localized selecting algorithm selects the right radios based on the quality of wireless links. Two kinds of distributed scheduling algorithms are implemented to transmit packets on the selected radios. Finally, a parallel-adaptive routing metric is presented. Simulation results by NS2 show that this parallel-transmission scheme could enhance the average throughput of network by more than 10%.
摘要:Vehicle to grid technology allows bidirectional energy exchange between electric vehicles and the power grid for achieving many known benefits. However, V2G networks suffer from certain security threats, such as EV’s privacy and authentication problem. In this paper, we propose an anonymous group authentication scheme for V2G communications. This scheme realizes dynamic joining and revocation of EVs, and greatly reduces the overhead of EV revocation. Through the theoretical analysis, this scheme can ensure identity privacy of EV user and security of data transmission in the process of charging and discharging.
摘要:Network congestion, one of the challenging tasks in communication networks, leads to queuing delays, packet loss, or the blocking of new connections. In this study, a data portal is considered as an application-based network, and a cognitive method is proposed to deal with congestion in this kind of network. Unlike previous methods for congestion control, the proposed method is an effective approach for congestion control when the link capacity and information inquiries are unknown or variable. Using sufficient training samples and the current value of the network parameters, available bandwidth is adjusted to distribute the bandwidth among the active flows. The proposed cognitive method was tested under such situations as unexpected variations in link capacity and oscillatory behavior of the bandwidth. Based on simulation results, the proposed method is capable of adjusting the available bandwidth by tuning the queue length, and provides a stable queue in the network.
摘要:Providing reliable multicast service is very challenging in Ad Hoc networks. In this paper, we propose an efficient loss recovery scheme for reliable multicast (CoreRM). Our basic idea is to apply the notion of cooperative communications to support local loss recovery in multicast. A receiver node experiencing a packet loss tries to recover the lost packet through progressively cooperating with neighboring nodes, upstream nodes or even source node. In order to reduce recovery latency and retransmission overhead, CoreRM caches not only data packets but also the path which could be used for future possible use to expedite the loss recovery process. Both analytical and simulation results reveal that CoreRM significantly improves the reliable multicast performance in terms of delivery ratio, throughput and recovery latency compared with UDP and PGM.
摘要:In this paper, a dynamic robust multiple watermarking algorithm is proposed based on Discrete Wavelet Transform (DWT) and Human Visual System (HVS). Watermark image is transformed by Arnold transform. Original image is divided into blocks with 8 by 8 and each block is transformed by DWT. By adopting the Just Noticeable Difference (JND) of HVS and changing low frequency coefficients, binary string message can be embedded into the decomposed original image. Watermark can be extracted blindly. Experimental results have shown that the proposed watermarking has robust against many attacks such as JPEG compressing, cropping, additive noise, line removal, median filter and related attacks with sinStirMark.
摘要:In this paper, we carry out QoE (Quality of Experience) assessment of fairness between players in a networked balloon bursting game with olfactory and haptic senses. We also make a comparison of the fairness among different types of networked games with olfactory and haptic senses in the assessment. Then, we clarify the differences owing to usage of olfactory and haptic senses among the games. As a result, we illustrate that the fairness is largely affected by the delay difference, and we also demonstrate that the allowable range depends on the type of games, type of senses which are employed in the games, and the play methods.
摘要:The rapid increasing demands of multi-media applications have busted the improvement of video transmission. By the increase of multimedia transmission, quality of experience (QoE) has become the hot topic of the wireless networks’ research. This paper proposes a QoE-aware resource allocation algorithm in MIMO-OFDM Networks. The power allocation estimation is formulated to maximize according to QoE by considering the video transmission rate and the subcarrier schemes under the constraint of minimum power. In this paper, we will analyses the the performance of video transmission from transmission rate at the application layer to the power allocation at the physical layer. From simulation results, we can see that the proposed subcarrier allocation algorithm maximizes the video QoE by minimizing the sum distortion of multi-users in MIMO networks with power constraints.
摘要:Ignoring the generality in the design of Wireless Sensor Networks (WSNs) applications limits their benefits. Furthermore, the possibilities of future extension and adaptation are also restricted. In this paper, several methods to enhance the generality in WSNs are explained. We have further evaluated the suitability of these methods in centralized and de-centralized management scenarios.
摘要:In this paper, aiming to improve the quality of multimedia transmission while satisfying the quality of service (QoS) requirements, we propose an optimal subcarrier allocation by jointly considering the video coding rate and the available power resource. We jointly analyses the effects on the performance of multimedia transmission from video coding rate at the application layer as well as the power control at the physical layer. This proposed joint power and subcarrier allocation algorithm in MIMO OFDM systems enables us both to overcome the challenge of full CSI (channel state information) with RD (the rate-distortion) to make minimum of the distortion of each users under delay and power constraints. Simulation results show that the proposed optimal subcarrier allocation algorithm improves the multimedia transmission quality considerably through the comparison with the resource allocation algorithms only use a single layer of information.
摘要:Code dissemination is one of the important services of wireless sensor networks (WSNs). Securing the process of code dissemination is essential in some certain WSNs applications, state-of-the-art secure code dissemination protocols for WSNs aim for the efficient source authentication and integrity verification of code image, however, due to the resource constrains of WSNs and the epidemic behavior of the code dissemination system, existing secure code dissemination protocols are vulnerable to Denial of Service (DoS) attacks when sensor nodes can be compromised (insider DoS attacks). In this paper, we identify five different basic types of DoS attacks exploiting the epidemic propagation strategies used by Deluge. They are (1) Higher-version Advertisement attack, (2) False Request attack, (3) Larger-numbered Page attack, (4) Lower-version Adv attack, and (5) Same-version Adv attack. Simulation shows these susceptibilities caused by above insider DoS attacks. Some simple models are also proposed which promote understanding the problem of insider DoS attacks and attempt to quantify the severity of these attacks in the course of code dissemination in WSNs.
摘要:File and data distribution can be easily classified as one of the basic uses of networks. With uses ranging from Short Message Service (SMS) to program updates, from micro-blogging to social networking, every network today must support some type of file and data dissemination method. Infrastructure networks have already implemented these services using well known communication protocols. Ad hoc networks pose a greater challenge due to their sporadic network set-up. At a given time we do not know who is connected to the network, and whether the intended recipient of the data can be reached. In this paper we introduce Serval MeshMS, a protocol for ad hoc file and data distribution, enabling the diffusing of data through an ad hoc mesh network. It is based on a single-hop, store and disseminate opportunistic architecture, and has been shown to work over great distances. Preliminary implementations are encouraging, with surprising results achieved.
摘要:In disaster situations, people need to evacuate from dangerous areas to safe ones. In particular, they must formulate an evacuation plan for themselves when they cannot obtain support. Communicating with other evacuees to obtain information is useful in formulating an evacuation plan, and some studies have used a mobile ad hoc network (MANET) for this purpose, because such a network can be constructed using only wireless devices even when a fatal situation arises. However, we cannot treat a MANET in the same manner as other networks (such as a carrier network or Wi-Fi), and MANETs have several shortcomings in regard to information exchange. It is necessary to investigate the effects of these limitations on creating evacuation support systems on a MANET. We evaluated whether the limited information exchange available using a MANET is sufficient to create evacuation support systems through the use of a multi-agent evacuation simulator. As a result, our simulator showed that limited communication in which people communicate only with neighbors provides substantial efficiency for evacuation. People can continue to evacuate effectively even if they cannot obtain all of the desired information owing to MANET limitations.
摘要:In this paper, the design of a 9.1 GHz Low Noise Amplifier (LNA) of a RADAR receiver that is used in the Navy is presented. For the design of the LNA, we used GaAs Field-Effect Transistors (FETs) from Agilent ADS component library. In order to keep the cost of the circuit in low prices and the performance high, we design a two-stage LNA.
摘要:Traditional products working independently are no longer sufficient, since threats are continually gaining in complexity, diversity and performance;In order to proactively block such threats we need more integrated information security solution. To achieve this objective, we will analyze a real-world security platform, and focus on some key components Like, NAC, Firewall, and IPS/IDS then study their interaction in the perspective to propose a new security posture that coordinate and share security information between different network security components, using a central policy server that will be the NAC server or the PDP (the Policy Decision Point), playing an orchestration role as a central point of control. Finally we will conclude with potential research paths that will impact NAC technology evolution.
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