- EI核心期刊
Triggered update is a common mechanism of Distance Vector (DV) algorithm to accelerate network convergence and alleviate routing loops. To effectively avoid the frequent and meaningless triggers around the trigger boundary or threshold and correctly reflect dynamic characteristics of state fluctuations which tightly associate with network quality of service (QoS), differing from the triggered update based on variety of absolute value of state, a state stability-based triggered routing update mechanism for DV algorithm (SSB-TU，state stability-based triggered routing update mechanism) is presented. SSB-TU acquires the stability variety of delay state according to second-moment–based function of statistical parameters and decides the generation and transfer of triggered update. Computer simulation and analysis indicate that, SSB-TU can clearly reflect state fluctuation and guarantee important network performances like network throughput etc., meanwhile, timely update network state that varies distinctively and efficiently mitigate routing loops.
A new type of numerical mode-matching (NMM) theory is applied into numerical simulation of common resistivity logs. In analytical section, by the continuity of interface between the adjacent layers in electromagnetic field, the traditional reflection and transmission matrixes is improved, and relationship between up-going and down-going wave is derived. A new transition formula is firstly presented. The improved NMM method, avoiding complicated matrix inverse, is easy to understand and has concise physical meaning. Furthermore, according to reciprocal theory, the calculating speed for B-A-M is one time faster than that for A-M-N. By the experiments for two-layer and three-layer homogeneous media, this method is verified to be highly precise and effective comparing with FEM method and the previous NMM method. The core concept of new NMM is helpful to 3-dimension NMM and other geophysics method in stratum media.
Some of current available QoS(quality of service) enhancement mechanisms for home network are too simple to provide parameterized QoS features, and the others adopt central polling mechanism which may result in single-point fault and performance bottleneck. Aiming at this situation, a new MAC(media access control) mechanism based on multiple token-rings was proposed. The complex token-scheduling algorithm as well as the corresponding resource allocation and admission control algorithms was designed. The distributed parameterized QoS control was realized. The proposed complex token-scheduling algorithm radically overcomes the drawbacks of simple token-scheduling and has stronger resource-scheduling and service-differentiation capabilities. Simulation results showed that the proposed method can effectively improve utilization efficiency of network bandwidth.
It is known in conference [1] that the construction and enumeration of symmetric balanced Boolean functions is equivalent to the solution of the knapsack equation and enumeration of the solutions. In this paper, we first find out a set of solutions of this equation when is odd and the number of the elements in is given, then we obtain the necessary and sufficient condition under which there exists other solutions of the equation out of the set .We also show a method for finding out the solutions out of the set . At last some solutions of the equation is given when .
Based on Butler Matrix, a novel simple-structured hybrid smart antenna system applicable in Ad Hoc network terminals is designed. A super-resolution beamforming algorithm is also presented by combining with the direction of arrival (DOA) estimation algorithm of digital signal processing (DSP). By this algorithm, it is deduced the shift value formula of the variable phase shifter when the antenna array switches to the direction of the desired signal. Simulation results show that the system facilitates the implementation by use of the simple system structure and easy beamforming feature. And it can drive the antenna to follow the input signal, which can greatly improve the signal quality and suppress the electromagnetic interference..
Through deep discussing the worms, the proportional relation between the propagation speed of worms and the scale of network is found. On this condition, an approach to decrease the scale of network by division and block the worm on the border of network to efficiently repress the worm in large-scale network is proposed in this paper. The graph-based model of network division is created, an algorithm fit for worm spread restraint is brought forward, and the theoretic analyze and simulations prove the efficiency of this approach.
Certification path construction of cross domain is a very complicated process, yet, to this day it is not a quite efficient certification path construction algorithm. To the above problem, this paper proposes a high efficiency certification path construction algorithm, comparing with other algorithms, this algorithm makes certification path construction the more simple and higher efficiency and better expansibility. Besides the algorithm is applicable to other trust models.
The compressed video data is easily disturbed or lost in error prone channel, and the error not only affects the current frame but also propagates to the subsequent frames especially when it occurs in Intra frames. To address this question, we improved a spatial error concealment algorithm, which can be called texture prediction interpolation, based on the research of the video coding standard H.264. It has been demonstrated that this method achieves good perceptual quality.
A charging policy supposing the modification of negotiation policy according to the Real QoS (RQoS), which the services actually obtain, is proposed in order to realize the QoS-based charging in next generation network. During the charging process of RQoS policy, the user’s satisfaction and the utilization efficiency of network resource are taken into account. Simulation results show that the policy is superior to the traditional flat-rate and ToS-based charging policy on the utilization of the networks and the satisfaction of the users.
After analyzing the problem of the Web services matchmaking methods which based on description logic reasoner, a simple and efficient semantic distance calculation method is proposed. Based on this method, a new Web services matchmaking method with enhanced semantic precision is proposed. On the basis of the result from the description logic reasoner, proposed method adds the semantic distance calculation of concepts in ontology to enhance the precision of matchmaker. The experimental research results show the feasibility and effectiveness of the proposed method.
A new evaluation approach for the in-band nonlinear distortion, which is formed by the orthogonal frequency division multiplex (OFDM) signal passing through the high power amplifier, is presented. Comparing with widely used nonlinear additive Gaussian noise models, the new approach is based on the properties of the large deviations of a stationary Gaussian process and shot noise theories, which offer important insights into the true nature of clipping distortion as well as detail information on clipping induced impulse noise and its impacts on the system when the OFDM signal is transferred and processed. The methodology can also be extended to be used in many communications systems with high peak-average-ratio and peak-limited nonlinearities, and the downlink performance analysis of large capacity code division multiple access (CDMA) systems.
An iterative list branch and bound algorithm is proposed in MIMO detection, which adopts candidate list to compute soft information and reduces computation complexity. Furthermore, an improved algorithm is proposed .It uses a prior information form the preceding iteration and has advantage from recalculating the candidate list. Simulation results show that the proposed iterative algorithm can achieve near-capacity performance and the improved algorithm reduces the required candidate list size without performance degradation.
Based on the research of multiparty-communication and IP multicast, a new IPv6 addressing method is proposed to support multiparty-communication applications with small-scale group. This algorithm utilizes the extension header of IPv6, an extension header called destination address extension header is designed. The new method is between unicast and multicast, which is similar to multicast on the performance and similar to unicast on the route. This method avoids the deficiency of the unicast and the multicast on the multiparty-communication with small-scale group. The new addressing method can support many multiparty-communication applications very well, but change the current protocol little.
By the analysis of the development of key technologies and QoS (Quality of Service) requirements of the real-time traffic in mobile communication systems, a simple and efficient random access scheme which is suitable for TD-OFDMA systems is proposed. In this scheme, the network terminals adopt different random access processing methods by utilizing the special FRRACH (First Refusal Random Access Channel) according to the delay sensitivity of the traffic. The new scheme efficiently avoids the packet collision and guarantees QoS requirements for the real-time traffic. Theoretical analysis and simulation results show the new scheme is superior to current random access schemes with respect to resource efficiency in random access process, successful access probability and average delay.
Electronic commerce is a main trend in Internet applications ,which should be based on fair exchange. A new fair exchange protocol with semi-trusted third party is proposed on the basis of a new convertible authenticated encryption scheme. Compared to the optimistic fair exchange protocols, the new protocol has a simpler structure and a lower communication overhead and the properties of privacy, faireness, non-repudiation and timeliness are satisfied.
When mobile station (MS) accesses into IP Multimedia Core Network Subsystem (IMS) through General Packet Radio Service (GPRS), the MS should perform authentication and key distribution operations in protocol Authentication and Key Agreement (AKA) at both GPRS and IMS level. The two operations are very similar, so it is very inefficient to perform twice independently. To solve the problem, an optimized integrated scheme based on some previous work is proposed, in which only GPRS AKA operation is performed and IMS can authenticate MS using the result of GPRS authentication. At the same time, the scheme can meet the requirements of MS authenticating IMS and key distribution. Feasibility and performance is analyzed.
Multiple input multiple output architecture is one of the most promising techniques to improve the quality and capacity of future wireless communication systems. In this paper we proposed an improved layered space-frequency scheme for the broadband MIMO-CDMA systems. The proposed scheme opens the way of detecting multi-antenna signals in the frequency domain. Simulation results show that the proposed layered space-frequency scheme can obtain better tradeoff between performance and complexity than conventional ones.
To meet the engineering requirement, a 2.45GHz RFID tag antenna and its minimization design are described. The antenna is presented with 450MHz bandwidth under the condition of VSWR less than 1.5, 1.4dB gain, and with the dimension of 37mm×45.8mm. After the minimization, the antenna shows a dimension of 31.8 mm×28.5mm, around 47% reduction of area compared to the original one. Its bandwidth is about 220MHz under the condition of VSWR less than 1.5, and 1.2dB gain. The measured results are compared with the simulated results, and good agreement is obtained.
A new method of automatic entity relation extraction is proposed. Based on the Bootstrapping algorithm, the hierarchy knowledge extraction model can be designed. The inner specific word extraction model and outer pattern extraction model can be nested each other to extract automatically knowledge, so that the specific dictionary and pattern rules used for the entity relation extraction is achieved. Combined with the Comprehensive Information Theory, the semantic and pragmatic information can be added into the relation extraction patterns to generate the Comprehensive Information Knowledge-Base (CIKB). Both the experiments of relation extraction and the evaluation have been done.
Most of the commercial DBMS products are lower in the security class ratings. Considering facts, a scheme to strengthen the security of database by a security enhanced system is proposed. The design of security enhanced system is specified on the base of discussing the security aspects of database and this system is also taken to an anti-attack analysis. This system ensures the security of database server by certificating authority and tuple-level mandatory access control on the basis of network isolation. Using this system to strengthen the security of database is practical and feasible.
Market demand for intercommunication between PSTN and IP networks impels the TWAC service, a voice service based on PSTN and IP networks to provide multiple service features for the users. Compared with traditional WAC service, TWAC works on the integrated IN platform, employs INAP CS2 and SIP protocols to realize the service integration of PSTN and IP networks and provides users to communicate between different networks. This paper mainly introduces the network framework of TWAC and its service integration solution.
USSD(unstructured supplementary service data) is a new data service defined by ETSI for use within the GSM. Aiming at providing evaluation means for the service performance of USSD service platform, this paper presents the performance model based on Queueing Network. With the analysis of the Pre-Paid Replenish service deployed on the USSD service platform, we have obtained some performance metrics through using the approximate Mean Value Analysis algorithm. These metrics help to find the bottleneck of the system and improve the quality of service. Finally, OPNET is used to simulate the system, and verified the accuracy of this model.
After considering actual needs for digital rights manager and security rask, a new watermark and cryptography based model for digital rights management (DRM) is proposed, which includes seven objects, three of them are authenticity. The copyright registering, online transactions, watermarking detecting and dispute resolutions of this model are studied. This DRM model is designed to be flexible and support various business and using cases. In the DRM model, the author’s ID, distributor’s ID and the consumer’s ID are regard as some of watermarks information, which can be used for binding information for digital content, some of the cryptographic solutions, protocols and watermarks protocols are also adopted to prevent from algorithm and protocol attack. This DRM model has good security and practicability.
Security of broadcast communication is the key challenge in wireless sensor networks. The characteristic, key security issues and design goal for achieving the security of broadcast communication in wireless sensor network are analyzed firstly in this paper, and then global broadcast authentication based on public key algorithm and local broadcast authentication based on one-way key chain are proposed separately as well, as a consequence, reliability, integrity, freshness of broadcast were acquired effectively. The performance analysis showed our method was efficient in communication, energy consume and storage.
The performance of squaring algorithm is restricted by observation interval. Furthermore, the influence becomes more complex when the frequency offset is considered. Due to above problems, the Kalman filter was introduced. Then influences of frequency offset and observation interval on symbol timing recovery system under this circumstance were studied. The design of configuration and parameter for the second-order Kalman filter was analyzed and discussed. Simulation results show that the estimation accuracy is observably improved by joining the second-order Kalman filter when the observation interval is short. Consequently, the contradiction between the calculating precision and speed is effectively solved. Comprehensively considering precision, processing speed and computation complexity, the second-order Kalman filter is better than the first-order. It is more suitable for an all-digital symbol timing recovery system.
Adding a new firewall rule often conflicts with the existed ones, which leads to security vulnerabilities. In order to avoid such vulnerabilities, firewall administrators have to determine an appropriate position in the firewall rule set to be inserted, and identify all the rules conflicting with the new rule in advance. The time complexity of the current conflicts detection algorithm for firewall rule set is O(dN), which makes its performance very poor. A new algorithm for detecting firewall rule set conflicts based on tuple space search is presented not only to find all the rules conflicting with the new rule, but also reduce the time complexity as O(logN+N/w). So it can efficiently help administrators determine an appropriate insertion position of the new rule to avoid vulnerabilities.
A novel type of spreading access codes with set-wise zero correlation window (ZCW) is proposed for minimum orthogonal frequency shift multi-carrier direct spread code division multiple access (CDMA) system in which the carrier gap is half of the reciprocal of the chip cycle. The proposed codes are constructed through the direct product of some ZCW complementary codes and certain extend matrix. That is, each complementary code is extended to a set of codes. The access codes correlation property of the codes in one set lies on the extend matrix, nevertheless the ZCW still exists between any two codes in any different code sets. The receiver adopts joint detection only for a code-set rather than for all the codes. Simulation results show that data transmission rate can be improved by several times at the cost of 1-2 dB signal to noise ratio loss in multi-path fading channels.
The integrated routing algorithm in IP over WDM networks under the self-similar traffic is studied, and a new integrated on-line routing algorithm, min_influence algorithm, is proposed. It can model the state of the whole network more accurately after assigning resource than other algorithms, and facilitate the distribution of
network resource more reasonably, which consequently improves the Network performance. Extensive simulations in three respective network topologies show that min_influence algorithm performs better in terms of connection blocking probability (CBP) and bandwidth blocking ratio (BBR) than other existing approaches under the parameters of self-similar traffic(hurst, mean and variance).
An iterative multi-user detection receiver structure is proposed for multiple input multiple output interleave division multiple access (MIMO-IDMA) systems. Different chip-level interleaving signatures distinguish users. A novel mean-based soft decision multi-user detection (SoD) algorithm is applied in multi-user detector. Simulation results show that the proposed SoD detection scheme improves the performance in SNR around 2dB compared to MMSE, 1dB superior to SoIC, and has lower bit error rate and complexity.
Existing single sign-on (SSO) schemes are built on centralized user information storage mechanism and single authentication mode, and it’s hard to meet the requirement of business operations in the dynamic and loose-coupled environment. To solve above problems, the ticket technology, agent mechanism and digital signature are studied, a new better SSO scheme is presented that uses cookie transmission carrier and ticket technology to support multiple authentications SSO, in addition, it establishes a authentication trust chain to support cross-domain SSO based on certificate trust chain. The results show the new scheme provides higher security and wider usage range, while it overcomes the shortcomings of the existing.
To simplify the problem of multiple lognormal random interferences, an equivalent method is proposed to approximate the sum of correlated random variables to the sum of uncorrelated ones. With this approximation, the theories based on uncorrelated shadowing model can be used to analyze and simulate the system performance in the presence of multiple correlated lognormal interferers by simply modifying the standard deviation of lognormal shadowing. The formula to modify the standard deviation is derived. The modified standard deviation is generally larger than the original one and increases with the correlation coefficient between lognormal interferers and with the number of interferers. With the Sørensen correlation model, the validity of the approximation method has been verified by simulation of both the cumulative distribution function of the total interference and the outage probability.