Showing papers in "Journal of China Institute of Communications in 2004"

Survey of information security risk assessment

Abstract: In the information security engineering, Risk Assessment plays an important part. It is the basis of the information system security systematism. The article discusses in detail the contents of risk assessment, for example: present situation, models, standards, methods, process, then introduces information security test and evaluation system, finally, the paper analyzes the problems existing in Risk Assessment and the future prospect.

Survey on wireless sensors network

Abstract: The architecture, characteristics and application fields of wireless sensors network are briefly introduced. Some hot spots including media access control protocols, power-aware routing schemes and nodes location are presented in detail. Open issues and development intends of sensors network are also discussed.

Evaluation method for node importance in communication networks

Abstract: An evaluation method for node importance in communication networks is proposed, the concise generalized expressions are given. The relative importance of two groups of nodes in the graph can be compared with respect to the number of spanning trees. The most vital nodes are those whose removal with their incident links most drastically decreases the number of spanning trees. Experimental results show that the method is simple and can reflect node importance determined by the network topology more precisely.

Performance analysis of type III HARQ with Turbo codes

Abstract: The performance of type III HARQ with code combing in wireless channel environments is lucubrated through both theoretical research and simulation analysis, and is compared with those of the other two HARQ schemes, viz. type I HARQ and type II HARQ with chase combining. All the research in this paper is carried out on both the AWGN channel and Rayleigh fading channel, respectively. By applying renewal theory and channel coding theorem, we obtained the closed-form solutions to the typeⅠHARQ and type II HARQ. For the type III HARQ, although the closed-form solution is not obtained, we did get the integral solution. Furthermore, using Turbo codes as forward error correction, the throughput and the residual FER of the three HARQ schemes are simulated. It shows that for arbitrary block fading channel, comprising AWGN channel, the performance of type III HARQ is always better than that of type II HARQ, whereas type II HARQ is always better than that of type I HARQ. Especially, the advantage of type III HARQ will be more prominent on Rayleigh fading channel.

Research on intrusion detection techniques: a survey

Abstract: Intrusion detection is one of the critical techniques in information assurance. In this paper we give a survey of the state of the art in the development of intrusion detection systems including basic notions,models, methods, etc. We also document some remaining problems and emerging trends in this area.

Simultaneous estimation of 2-D DOA and polarization of multiple coherent sources using an electromagnetic vector sensor array

Abstract: This paper studies the problem of simultaneous estimation of two-dimensional directions- of-arrival (DOA) and polarizations of multiple coherent sources using redundant spatial coherence structure potentially possessed by an electromagnetic (EM) vector sensor array. This paper shows versatile realizations of spatial smoothing technique through distinct ways of sub-array grouping and dividing by which several MUSIC and ESPRIT variants are presented. The paper further provides sufficient conditions under which the given methods can tackle the coherence problem successfully. Simulation results are also included to verify the efficacy of the proposed methods.

Automatic recognition for common used modulations in satellite communication

Abstract: A novel recognition scheme based on the spectrum feature analysis is proposed A set of robust feature parameters are extracted from signal power spectrum and the power spectrum of the second and fourth power of signal The proposed scheme can recognize many common used modulated signals in the satellite channel without any prior knowledge Simulation results show that the scheme can achieve more than 98% recognition accuracy when SNR is above 5dB This method is feasible and practical

Research on privilege-escalating based vulnerability taxonomy with multidimensional quantitative attribute

Abstract: On the basis of analyzing of research achievements of typical vulnerability taxonomies in the world, a privilege-escalating based vulnerability taxonomy with multidimensional quantitative attribute is presented in this paper Then we give examples of three vulnerabilities to illustrate the characteristics of this taxonomy, and present the risk evaluation formula and ranks of the evaluation level of risk

Edge-preserving image denoising method using Curvelet transform

Abstract: An image denosing algorithm using Curvelet transform is proposed. We not only adopted an improved Curvelet transform free of 搘arp-around?artifacts, but also combined wavelet thresholding with edge preserving approach to retain the sharpness of the images. Experiments show that our method yields denoised images with higher PSNR value and better visual quality. Key words: image processing; image denoising; Curvelet transform

Digital modulation recognition based on constellation diagram

Abstract: A new classification algorithm based on constellation diagram is proposed to overcome the weakness of traditional algorithms by witch few digital modulation types can be recognized. The blind equalization is first used to mitigate effects of multipath and system synchronization errors. Then subtraction-clustering clusters signal spatial distribution and the resulting centers are extracted to match standard constellation patterns. Thus, MASK, MPSK and MQAM signals can be classified. The computer simulations indicate that the constellation diagram is a stable and robust signature.

Research on the detecting algorithm of text document information hiding

Abstract: This paper put emphasis on vulnerability analyses based on semantic algorithm of text document information hiding aiming at popular algorithms of text document information hiding, and then designed a universally detecting algorithm named a detecting algorithm to measure relativity between sentences by the idea of conceptual graph Experimental result shows that the detecting algorithm can achieve a high degree of detecting reliability

Admission control for multimedia traffic in CDMA wireless networks

Abstract: This paper discusses CDMA system performance with multimedia services and analyzes interference-based admission control strategy with multi-dimensional Markov model. Moreover, considering priority of handover users and different QoS requirements, multi-level admission thresholds are set in system for different types of users, which can guarantee the quality of existed links and maximize the system capacity.

Study of communication protocol of distributed sensor network

Abstract: Based on the progress of distributed sensor network, an integrated architecture of distributed sensor network was put forward. The status of research and development was presented in detailed under the architecture. Some applications and research programs were also introduced. Finally, the future research directions of distributed sensor network were pointed out.

A survey of public key cryptography

Abstract: The advent of public key cryptography is a milestone in the development of modern cryptography. A survey of the research and implementation of PKC is presented in this paper, with the emphasis on the attack status of some typical systems such as RS A, ECC and XTR, and also their secure properties, standardization and realization being introduced in detail. Finally, some newly presented public key systems, such as public key cryptosystem based on braid group and quantum cryptosystem, are briefly introduced.

A kind of omni-directional multi-angle structuring elements adaptive morphological filters

Abstract: According to the structure characteristic of the morphological filter and combining the open-closing (close-opening) compound operation with adaptive arithmetic, this paper presents a kind of method that can not only efficiently removed various noise in images which have the complex texture but also preserved the detail better. The results of simulation show that it is superior to the standard median filter, the maximal, minimal morphological filter with onmi-directional structuring elements in the aspect of the noise removal, thereby extending the application of the morphological filters in removing the Gaussian noise. What is the most important is that this algorithm can keep the details of images more effectively.

A quantitative evaluation technique of attack effect of computer network based on network entropy

Abstract: An attack effect evaluation model of computer network based on network entropy was proposed in this paper. The paper put forward the concept of network entropy from the point of view of the security characteristic change of computer network after it was attacked. The calculation technique of network entropy difference was analyzed in detail by analytical hierarchy process (AHP) with the beginning of the choice and simplification of proper network security index set. The implementation idea of the attack effect evaluation system based on network entropy and the corresponding model verification method were presented as well. The elementary test and calculation results show that the model can be in all reason utilized to measure the actual network attack effect.

A multi-object genetic algorithm of QoS routing

Abstract: Formula analysis is given for the network topology and multi-QoS router index. This paper proposes the math model of QoS routing based on multi-object planning method. Then, we present a multi-object genetic algorithm of QoS routing. Simulation results demonstrate the feasibility and efficiency of the proposed algorithm.

Blind source separation of communication signals of different magnitudes

Abstract: The natural gradient algorithm is a very important approach for blind source separation (BSS). The aim of this paper is to investigate the blind source separation of a linear mixture of independent sources of different magnitudes by using the natural gradient algorithm. We compare various activation functions for the algorithm and propose a better one. Simulation results with ten communication signals of different magnitudes show that the algorithm with proposed activation function converges faster than other activation functions.

A novel algorithm for content-based image recognition and filtering

Abstract: This paper presents a novel approach to blocking objection- able images. This system integrates an image filter module into a browser module. Blocking objectionable images is completed by the data interactions between the two modules. In the image filter module, a skin filter is designed to obtain the skin information, and a new Gamma correction method is introduced to reduce the illumination effect. To process an image quickly, we split it into several regions and a voting scheme is adopted to obtain some potential regions that can describe the attributes of the image. From the regions of interest, the contour of the body trunk is finally sketched and the local information is extracted from it. Experimental results show that our algorithm is capable of blocking objectionable images successfully with low computational cost.

Polarity text filtering based on semantic analysis

Abstract: Text filtering technology based on statistics usually is ineffective when it deals with polarity text. The method overlooks the semantic restriction of text, so it isnt good for identifying polarity information. The paper provides a new text filtering method based on semantic analysis, which takes into account semantic relations in text. The experiment results indicate that the method efficiently recognizes and heads off the polarity information.

A new approach to forecasting Internet worms based on netlike association analysis

Abstract: This paper presents a new approach to forecasting the Internet worm infection based on netlike association analysis after analyzing the behavior pattern of Internet worms, and explores their forecast mechanism we design two forecasting algorithms. An Internet worm forecasting model is established and a prototype based on forecasting algorithms is given. At last, we present the related experimental data and analysis results by using our approach. Comparing with the existing methods, our approach becomes more efficient, and has the characteristic of detecting the unknown Internet worms.

Research of using an improved ant colony algorithm to solve TSP

Abstract: An improved ant colony algorithm was proposed, whose cores were that using the genetic algorithm(GA) to optimize the control parameters of the ACA (α、β、ρ、q0) and applying MMAS to routing. The new algorithm (ACAGA) is characterized by good global search capability. We use it to solve TSP (traveling salesman problem). Simulation results show that ACAGA is superior to conventional ACA and GA in quality and efficiency.

Modulation classification of M-QAM signals

Abstract: This paper proposed a modulation recognition algorithm for M-QAM signals This scheme does not require the prior information about baud rate and carry frequency of the received signals These parameters are estimated first, then interpolation, deconvolution, clustering and recognition are performed Computer simulations show that the correct recognition ratio is larger than 95% under the condition that the SNR is higher than 8dB and more than 400 symbols are used So it is suitable for the practical application of signal detection and fast recognition in non-cooperation communication systems

Novel long-period fiber gratings written by high-frequency CO_2 laser pulses and their applications in optical fiber communication

Abstract: It was report that novel long-period fiber gratings (LPFG) fabricated by using a new method for writing technique that was mainly based on the thermal shock effect of focused high-frequency CO2 laser pulses at several kHz. Several unique characteristics of these LPFG, such as bend and transverse-load, were observed by experiments, for the first time, to our knowledge. These unique features of the LPFG were mainly due to the asymmetrical distribution of the refractive index on the cross-section of the LPFG induced by high-frequency CO2 laser pulses. Based on these novel LPFG, an amplified spontaneous emission (ASE) noise filter and a gain equalizer had been demonstrated for the noise figure reduction and the gain spectrum flattening of Er-doped fiber amplifiers (EDFA), respectively. By means of the unique bending and loading features of the LPFG, two tunable gain equalizers had been demonstrated for dynamic gain flattening of EDFA.

Study of congestion control mechanism for wireless networks using expert control

Abstract: The application of TCP over wireless networks is a challenging work due to high bit error rates and fading and handoff This paper presents a congestion control mechanism for wireless networks based on expert control, which makes sure the state of TCP connection and differentiates between wireless link errors and network congestion in terms of the inference Wireless link errors as well as congestion in the wired network are separately controlled The simulation results show that this method can strengthen the congestion and random errors processing capability in real time and improve the throughput of the network, and this control scheme is more robust than normal TCP

Performance evaluation of virtual channel switching system based on discrete time queue

Abstract: The principle of ATM switch virtual channel connection is analyzed, a Geom/G/1 discrete-time queueing model with setup-close delay-close down is built based on the SVCC operating mechanism, SVCC performance measures of response time, connection building(releasing) ratio, running efficiency and idle ratio are studied, the depending relationship that these measures on close delay timer is analyzed ,which has potential applications in SVCC design.

An improved method of enhancing Kerberos protocol security

Abstract: This paper has a detailed analysis of the Kerberos protocol security, and provides an improved method for the Kerberos protocol security according to its defect. After a detailed analysis, the improved Kerberos protocol is more secure, the key management is more proper, and the process of authentication is more secure and more reliable.

Adaptive admission control algorithm and performance analysis in wireless/mobile networks

Abstract: In wireless/mobile networks, new connection blocking probability(CBP) and handoff connection dropping probability(HDP) are important connection level QoS parameters. Forced connection terminations due to handoff connection dropping are generally more objectionable than new connection blocking. In general, most of the previously proposed schemes for reducing handoff connection dropping probability substantially at the expense of increasing the new connection blocking probability and decreasing the utilization of the cells by reserving channels exclusively for handoff connection requests. Recently there is a growing interest in the adaptive multimedia application where the bandwidth of an ongoing multimedia connection can be dynamically adjusted. In this paper, we research multi-priorities services adaptive admission control mechanism, present a adaptive admission control algorithm, and analyze its QoS performance.

A protocol of specific secure two-party computation

Abstract: The research of multi-party computation was a subject of great importance in the international cryptographic circle. Based on the Φ-hiding assumption and public-key cryptosystem of homomprphic encryption, we constructed a protocol of special secure two-party computation--comparing protocol. The protocol could ensure fairness, security, efficiency and robustness. We also proved the security and correctness of the protocol, using the strict definition of the secure multi-party computation. Applications of the protocol included private bidding and auctions, secret ballot elections and so on.

Survey of network attack classification

Abstract: This paper introduces the status quo of network attack classification summarily, and the trend is analysed.