Study of Intrusion Detection Systems

Modern network systems have much trouble in security vulnerabilities such as buffer overflow, bugs in Microsoft Internet, sensor network routing protocol too simple, security flaws of applications, and operating systems. Moreover, wireless devices such as smart phones, personal digital assistants （PDAs）, and sensors have become economically feasible because of technological advances in wireless communication and manufacturing of small and low-cost sensors. There are typologies of vulnerabilities to be exploited in these devices. In order to improve securities, many mechanisms are adopted, including authentication, cryptography, access control, and intrusion detection systems （IDS）. In general, intrusion detection techniques can be categorized into two groups： misuse detection and anomaly detection. The misuse detection systems use patterns of weB-known attacks or weak spots of the systems to identify intrusions. The weakness of misuse detection systems is unable to detect any future （unknown） intrusion until corresponding attack signatures are intruded into the signature database. Anomaly detection methods try to determine whether the deviation is from the established normal usage patterns or not. The critical success of anomaly detection relies on the model of normal behaviors.     

Home Energy Management System Using NILM and Low-Cost HAN

Home energy management systems(HEMs) are used to provide comfortable life for consumers as well as to save energy. An essential component of HEMs is a home area network(HAN) that is used to remotely control the electric devices at homes and buildings. Although HAN prices have dropped in recent years but they are still expensive enough to prohibit a mass scale deployments. In this paper, a very low cost alternative to the expensive HANs is presented. We have applied a combination of non-intrusive load monitoring(NILM) and very low cost one-way HAN to develop a HEM. By using NILM and machine learning algorithms we find the status of devices and their energy consumption from a central meter and communicate with devices through the one-way HAN. The evaluations show that the proposed machine learning algorithm for NILM achieves up to 99% accuracy in certain cases. On the other hand our radio frequency(RF)-based one-way HAN achieves a range of 80 feet in all settings.     

Interference Coordination for Secrecy Enhancement in Random Wireless Networks

The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks,where the legitimate nodes and eavesdroppers are randomly distributed.In this paper,a new interference model is proposed from the userdominant perspective.The model can provide a better analytical assessment of secrecy performance with interference coordination for the presence of eavesdroppers.The typical legitimate is assumed to be located at the origin,and chooses the closest base station（BS） as its serving BS.The field of interferers is obtained by excluding the desired BSs（including the serving BS and its cooperative BS（s））.In contract with the exiting interference model,it is assumed that desired BSs and interferers belong to the same Poisson Point Process（PPP）,and eavesdroppers are distributed according to another independent PPP.Based on this model,the average secrecy transmission capacity is derived in simply analytical forms with interference coordination.Analysis and simulation results show that the secrecy performance can be significantly enhanced by exploiting interference coordination.Furthermore,the average secrecy transmission capacity increases with increasing number of cooperative BSs.     

An Energy Balancing Adaptive Routing Strategy Based on Interference Model in 6LoWPANs

IPv6-enabled low-power wireless personal area network （6LoWPAN） is an important part of the Internet of Things which will drastically transform the way our society functions. Designing an efficient routing strategy is crucial for optimizing traffic over 6LoWPAN resources and extending the network lifetime. This paper proposes an energy balancing adaptive routing strategy named EBAR. Considering the dynamic traffic and constrained energy in 6LoWPAN, EBAR adaptively updates paths between different source-destination pairs and balances the energy in 6LoWPAN. Simulation results indicate that EBAR can promote network performance and balance the energy in the network.     

A MultikeyRank Model Based on Ontology for Large-Scale Semantic Data

In order to provide users with intelligent retrieval services over large-scale semantic data, this paper proposes a MultikeyRank model. ORDPATHs is adopted to encode ontology classes defined in TBox and an inverted index is constructed according to the structured charac- teristics and semantic association of RDF data. A new query mode with one primary keyword and several auxil- iary keywords is designed. To reflect the user＇s perference objectively, the membership degree for ontology classes corresponding to the primary keyword is calculated based on the evidence theory and thus the MultikeyRank algo- rithm is formulated by extending the BM25F model accord- ingly. The proposed model was implemented in the self- developed distributed large-scale RDF data server “Jing- wei” and experimental results show that compared with BM25F, the evaluation indexes for P@5, P@10, P@15 and MAP are improved by 27.6%, 24.3%, 18.5% and 3.7% ,re- spectively.     

Golay Sequence Based Time-Domain Compensation ot Frequency-Dependent I/Q Imbalance

A time-domain frequency- dependent I/Q imbalance compensation scheme based on Golay complementary sequence for receiver is presented. By utilizing property of Golay sequence, the signal and its conjugate interference （image interference） in preamble are separated by correlation and used to estimate I/Q imbalance parameters. After that, a Least Square （LS） estimation of compensation filter is obtained and adopted in the compensation structure. Two applications of the presented algorithm are discussed： we could either estimate the channel along with I/Q imbalance or estimate the imbalance parameter only to maintain a lower cost. Both applications are testified by simulation. The results show that the image interference is significantly suppressed even in poor SNR condition, and the computation cost of the algorithms is low.     

A Novel Ship Detection Approach for Polarimetric SAR Images Based on a Foreground/Background Separation Framework

In this paper, we present a novel ship detection approach for Polarimetric synthetic aperture radar （PolSAR） images based on a Foreground/background separation （FBS） framework, which exploits the statistical dissimilarity of PoISAR data to separate desired targets from the background clutter. Since the FBS framework takes the spatial relations between pixels into consideration and the separation process exploits the inherent characteristics of PolSAR data, the proposed detector is stable to speckle. And the detection process is filter-free, thus it can preserve the edge and shape information of the extracted targets. Experimental results and comparisons with the standard polarimetric detector show that the proposed method is promising. Factors that affect the performance of the proposed detector are also analyzed and discussed in this paper.     

传感器网络中节点能量有效均衡的Top-k查询技术

无线传感器网络中top-k查询处理的节点能量高效以及实现各节点的能量消耗均衡,可以有效延长网络的生命周期。该文提出一种基于采样技术和节点空间相关性,来实现节点的能量均衡和高效的查询处理算法,称为能量均衡采样(,)近似top-k算法EBSTopk(,)。首先对传感器网络进行分区处理,利用区域内两两节点间的空间相关性对其建立线性回归预测模型和高斯预测模型;然后根据用户给定的相对误差界和置信水平1-建立节点高相关性预测准则;最后根据上述预测模型和准则,提出基于反复随机采样的能量均衡算法EBSTopk(,)-LR和EBSTopk(,)-MG。实验表明,所提出的EBSTopk(,)算法减少了无线传感器网络中的全局能量消耗,且在多次top-k查询后各节点的能量消耗达到均衡。     

On Minimizing Delay with Probabilistic Splitting of Traffic Flow in Heterogeneous Wireless Networks

In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.     

Virtualized Wireless SDNs： Modelling Delay Through the Use of Stochastic Network Calculus

Software-defined networks(SDN)have attracted much attention recently because of their flexibility in terms of network manage-ment.Increasingly,SDN is being introduced into wireless networks to form wireless SDN.One enabling technology for wirelessSDN is network virtualization,which logically divides one wireless network element,such as a base station,into multiple slices,and each slice serving as a standalone virtual BS.In this way,one physical mobile wireless network can be partitioned into multi-ple virtual networks in a software-defined manner.Wireless virtual networks comprising virtual base stations also need to provideQoS to mobile end-user services in the same context as their physical hosting networks.One key QoS parameter is delay.This pa-per presents a delay model for software-defined wireless virtual networks.Network calculus is used in the modelling.In particu-lar,stochastic network calculus,which describes more realistic models than deterministic network calculus,is used.The model en-ables theoretical investigation of wireless SDN,which is largely dominated by either algorithms or prototype implementations.     

Performance Analysis of WLAN Medium Access Control Protocols in Simulcast Radio-Over-Fiber-Based Distributed Antenna Systems

The performance of three wireless local-area network（WLAN） media access control（MAC） protocols is investigated and compared in the context of simulcast radioover-fiber-based distributed antenna systems（RoF-DASs） where multiple remote antenna units（RAUs） are connected to one access point（AP） with different-length fiber links.The three WLAN MAC protocols under investigation are distributed coordination function（DCF） in basic access mode,DCF in request/clear to send（RTS/CTS） exchange mode,and point coordination function（PCF）.In the analysis,the inter-RAU hidden nodes problems and fiber-length difference effect are both taken into account.Results show that adaptive PCF mechanism has better throughput performances than the other two DCF modes,especially when the inserted fiber length is short.     

Design and Implementation of An Active Multibeam Antenna System with 64 RF Channels and 256 Antenna Elements for Massive MIMO Application in 5G Wireless Communications

This paper focuses on the design and implementation of an active multibeam antenna system for massive MIMO applications in 5G wireless communications. The highly integrated active multibeam antenna system is designed and implemented at 5.8 GHz with 64 RF Channels and 256 antenna elements. The 64-channel highly integrated active multibeam antenna system provides a verification platform for digital beamforming algorithm and massive MIMO channel estimation for next generation wireless communications.     

An Introduction to Transmit Antenna Selection in MIMO Wiretap Channels

This paper is a survey of transmit antenna selection-a low-complexity, energy-efficient method for improving physical layer security in multiple-input multiple-output wiretap channels. With this method, a single antenna out of multiple antennas is selected at the transmitter. We review a general analytical framework for analyzing exact and asymptotic secrecy of transmit antenna selection with receive maximal ratio combining, selection combining, or generalized selection combining. The analytical results prove that secrecy is significantly improved when the number of transmit antennas increases.     

Self-Organization Approaches for Optimization in Cognitive Radio Networks

Cognitive radio （CR） is regarded as a promising technology for providing a high spectral efficiency to mobile users by using heterogeneous wireless network architectures and dynamic spectrum access techniques. However, cognitive radio networks （CRNs） may also impose some challenges due to the ever increasing complexity of network architecture, the increasing complexity with configuration and management of large-scale networks, fluctuating nature of the available spectrum, diverse Quality-of-Service （QoS） requirements of various applications, and the intensifying difficulties of centralized control, etc. Spectrum management functions with self-organization features can be used to address these challenges and realize this new network paradigm. In this paper, fundamentals of CR, including spectrum sensing, spectrum management, spectrum mobility and spectrum sharing, have been surveyed, with their paradigms of self-organization being emphasized. Variant aspects of self- organization paradigms in CRNs, including critical functionalities of Media Access Control （MAC）- and network-layer operations, are surveyed and compared. Furthermore, new directions and open problems in CRNs are also identified in this survey.     

On the Design and Temporal Petri Net Verification of Grid Commerce Architecture

The emergence of Grid Computing settings lays a solid foundation for designing and constructing a next generation E-commerce environment. This work presents a new E-commerce architecture based on a Grid Computing environment, and models and analyzes the architecture using Temporal Petri nets （TPNs）. It can make sufficiently use of the Grid resources to implement various electronic bargains between the geographically dispersed users. By means of its TPN model, some main temporal properties are represented and verified formally.     

Joint Optimization of Subchannel Reassignment and Power Adaptation for Multicarrier Cooperative Systems

An amplify-and-forward multicarrier cooperative system was proposed in this paper. The optimal resource-allocation problem was investigated in terms of improving data rate. An effective resource-allocation algorithm was proposed based on three techniques, adaptive modulation, subchannel reassignment design and transmit power adaptation. The designed subchannel reassignment not only increases the average data rate, but also raises the threshold of ＂water-filling＂ in optimizing power allocation that can further increase data rate. Since the power allocation is based on the designed subchannel reassignment, the complexity of the proposed algorithm is reduced greatly. Simulation results show that the proposed algorithm effectively increases the system＇s average data rate.     

A Probability Driven Quadri-Stage Contention Protocol for Mobile Ad Hoc Networks

The paper proposes a new contention based Time division multiple access （TDMA） Medium access control （MAC） protocol in wireless ad hoc networks, which can be termed Quadri-stage contention protocol （QSCP）. The QSCP protocol is free of both the ＂hidden terminal＂ and the ＂exposed terminal＂ problems. It is distributive and arbitrarily scalable. In the dedicated contention stage, nodes exchange their ＂Normalized accumulation and dissipation rate of payload （NADROP）＂ messages in 2-hop neighborhood, and then run a contention probability calculation algorithm to decide the probability of sending a contention frame. The algorithm guaran- tees that the number of time slot reserved by a node is proportional to its NADROP value, which can remarkably improve the end-to-end throughput when network load is heavy, and is more efficient in energy consumption. The simulation results demonstrate that QSCP performs better than the existing protocols.     

A Novel Surface Treatment Method for Improving the Antenna System Performance of Mobile Phones with Stainless Steel Frame

A novel surface treatment method of plat-ing Cu＋PPS film/coating on a mobile phone＇s stainless steel frame for improving the antenna system efficiencies is proposed. The mobile phone was measured in free space, in a silicon cover, and in the hand and cover si- multaneously. It＇s found that with this surface treat-ment, the total efficiency of the antenna system can be improved in all the four cases respectively by 14.22%, 1.38%, 15.19% and 1.72% at 940MHz （GSM900：880- 960MHz）, 2.59%, 3.21%, 4.81% and 1.43% at 1720MHz （DCS：1710-1880MHz） and 6.34%, 2.85%, 9.83% and 2.32% at 2100 MHz （WCDMA：1920-2170MHz）. This low- cost surface treatment method is an important break- through to improve antenna system performance of mobile phones especially for those with a stainless steel frame, and suitable for mass production.     

Location Verification Systems in Emerging Wireless Networks

As location-based techniques and applications have become ubiquitous in emerging wireless networks, the verification of location information has become more important. In recent years, there has been an explosion of activity related to lo- cation-verification techniques in wireless networks. In particular, there has been a specific focus on intelligent transport systems because of the mission-critical nature of vehicle location verification. In this paper, we review recent research on wireless location verification related to vehicular networks. We focus on location verification systems that rely on for- mal mathematical classification frameworks and show how many systems are either partially or fully encompassed by such frameworks.