- EI核心期刊
In order to study the construction of XOR message authentication code (XOR-MAC), we analyse it from the view of universal Hash and pseudo-random function, using shared random funciton model. Firstly, XOR-MAC is splited into two parts: a pseudo-random funtion and an universal Hash. Secondly, this two parts can be proved to have certain properties. Finally, XOR-MAC is regarded as a kind of Carter-Wegman MAC by adopting a new method that applies a pseudo-random functions directly to the output of an universal Hash family. And we give a simple security proof of XOR-MAC based on information theory. The most important thing is that many new MACs can be easily constructed using this idea.
To solve the resource optimization problem in self-organized heterogeneous networks,a resource configuration scheme is proposed. The novel scheme takes energy efficiency and connection stability of the network into account. This scheme includes three steps. Firstly,obtain the available channel resource through exploiting surrounding environment and then put the channels into the spectrum pool. Secondly,design user selection method on the basis of Morse potential which can guarantee network connectivity and reduce the transmission power cost. Finally,utilizing the results from the two former two steps,allocate proper power level to users while optimizing network energy efficiency. In the step of user selection,users are sorted according to the Morse potential and the ones with smaller morse potential value are selected and served with high priority. Power allocation is achieved by Barrier method. Simulation results show the advantage of the proposed scheme which can save transmission cost,guarantee stable network connectivity and gain higher energy efficiency.
The accuracy of the feedback codebook is a key factor for coordinated multi-point transmission/reception (CoMP). A new method of codebook evaluation based on space basis vectors and a method of codebook reconstruction with several preferred space basis vectors are proposed. Furthermore, the residual interference is discussed and its key influencing factors is deduced. Base on the above, this article proposes a new CoMP approach to do further interference cancellation. Simulation shows that, compared to the traditional methods, the new method has better performance in interference cancellation with advantages such as unnecessary to update codebook, flexible trade-off between feedback overhead and interference cancellation effect and good scalability.
In order to construct a most reliable power communication network within minimal construction cost, a path planning method based on immune algorithm is presented, which takes into account economy, reliability and service distribution. In the method, the network reliability function is designed based on cyclization rate, and the path planning model is built by the factors of service distribution. This method will increase the flexibility and completeness of planning result. Simulation results show that the proposed method is capable of providing efficient results under diverse cyclization rate constraint.
To solve the dimension disaster problem from the arbitrariness and complexity of user-relationship topology in distributed wireless network, a dynamic spectrum access algorithm is presented based on graphical game. Relying on information asymmetry environment, the users accessing channel is modeled as a graphical game so as to construct a new internal game in realistic environment. Pure-strategy Nash equilibrium without conflict is obtained by minimizing the regret value of person instead of that of system. Compared to the existing literatures, the algorithm can reduce the computing complexity effectively and meet the real-time communication requirements. Simulation results show that the pure-strategy Nash equilibrium achieves better system performance in terms of capacity and power utilization, specifically in the system with scare resources.
For the problem of misjudgment in the fuzzy data domain, a modified multi-classification algorithm of weighted wavelet support vector data description (WWSVDD) is proposed and applied to the infected pine recognition in remote sensing images. Firstly, utilizing the high resolution images acquired by the double spectrum camera fixed on the unmanned aerial vehicle, the features of ground objects are extracted to construct the corresponding feature vectors. Secondly, each kind of ground objects samples is described by WWSVDD model. Finally, according to the distribution of test samples in the feature space, the methods of minimum relative distance and membership function are respectively used to decide the labels of the samples, so that the infected pines are recognized ultimately. The experiment results show that the proposed method can recognize the infected pines more effectively than the traditional multi-classification methods of K-nearest neighbor (KNN) and support vector data description (SVDD).
Under the circumstances that wireless sensor network (WSN) nodes are deployed in a vast region and the node density is low, the existing node location algorithms are not optimum selections. A WSN node self-locating algorithm which utilized the directivity of smart antenna is proposed. There are two types of nodes in the objective network of the means. The first type is central node that equipped with global position system (GPS) unit and smart antenna. The second type is normal node that equipped with high frequency crystal oscillator. Normal node can support time of arrival (TOA) based ranging. With the help of directional locating signal sent by central node,a normal node can estimate the angle and distance between itself and the central node, and determine its position combining the angle and TOA based ranging result. Analysis and experimental results show that the proposed algorithm can provide fine location accuracy with relative low cost and low complexity.
Gerschgorin disk theorem based optimal user selection algorithm is proposed for cooperative spectrum sensing. The fusion center receives the sensing data from the secondary users and establishes the optimal user selection mechanism by employing Gerschgorin disk theorem. The sensing data of the selected secondary users will subsequently be fused as the global test statistic. Aided by the optimal user selection strategy, the cooperative sensing performance can be ameliorated. Furthermore, the detection performance can also be improved through the proposed iterative thresholding algorithm. Theoretical analysis and simulation results show that the algorithm depends on no a priori knowledge of the primary user signal and the noise power. The proposed method is hence robust against the noise power uncertainty, and can maintain consistent performance when slightly fewer sampling data and users are involved in cooperative sensing.
For the frequency hopping sequence sets with no-hit zone, the values of their Hamming correlation functions in the no-hit zone equal to zero, which can be used to eliminate the mutual interference in a frequency-hopping code-division multiple-access communication system. Based on the matrix permutation, a general construction of frequency hopping sequence sets with no-hit zone and flexible maximum Hamming correlation value is presented in this paper. Using the proposed method, frequency hopping sequence sets with lower hamming correlation and longer no-hit zone can be obtained. In addition, as a special case of the general method, a construction based on cyclic shift is introduced.
Using multi-channel resource assignment increases the stability of wireless network and throughput. A resource assignment algorithm is proposed for static and dynamic large scale wireless sensor networks. According the policy to reusing link, links are assigned to nodes based on routing information. In the simulations, it improves the throughput by 35.7% and 18.4% in different communication ranges compared to packets in pipe (PIP). In dynamic networks, network traffic generated to restore traffic is related to the number of nodes. The proportion of new traffic to total traffic for networking is less than the proportion of network nodes change.
A new multi-layer ring cellular structure for HAPS communication is constructed. The proposed cell structure will increase the width of the beam at the inner circle, reduce the width of the beam at the outer circle, and decrease the difference of signal to noise ratio between the inner and outer cells. The validity of ring cellular structure is verified by analysis and numerical calculation of wireless link budget. Also the complexity of the antenna design for engineering realization and cost are reduced by multi-layer ring cellular structure designed this paper.
In wireless multimedia sensor networks (WMSNs), multimedia data makes both qualitative and quantitative assessment for information quality more complex. Taking various types of data into account, a comprehensive assessment system which combines assessment of network quality and data quality to build a whole assessment model for WMSNs is established. First, the evaluating indicators are clearly defined according to the distinctive service provided by WMSNs. Second, the specific calculation method is analyzed for each parameter in both network domain and data domain according to the assessment of network and data. Finally, the integrated assessment scheme which consists of the evaluating of all indicators is proposed.
The traditional blind symbol synchronization scheme for zero prefix orthogonal frequency division multiplexing (ZP-OFDM) could not acquire accurate symbol synchronization estimation over multipath channels. According to this problem, a new blind symbol synchronization scheme for ZP-OFDM systems was proposed. The proposed scheme is based on zero prefix power collection in the ZP-OFDM symbols whose ZP average power regularly distributes in the two slide windows, and is applied the energy detection method of two unequal length windows to realize the blind symbol synchronization. Simulations show that the proposed symbol synchronization estimation scheme is not only of good estimation precision but also is not influenced by carrier frequency offset over multipath channels.
In order to suppress both the intra-cell interference and the inter-cell interference in the multi-cell system, a user selection method of the distributed beamforming based on zero-forcing algorithm is proposed. The users are selected with the chord distance between channels, and the base station utilizes these users' channels to implement zero-forcing algorithm and achieve beamforming vectors. Simulations show that under condition of different transmitting antenna number and the users' numbers, the throughput rate of the proposed algorithm becomes superior to the traditional ones'.
A multi-relay transmission scheme using fountain codes and adaptive coding and modulation was proposed, also the corresponding multi-relay selection algorithm was proposed. First of all, the throughput of adaptive modulation with fountain codes was analyzed, the optimal modulation scheme was given in different SNR range, and the performance of adaptive modulation in fading channels was analyzed. Furthermore, fountain codes and adaptive modulation was applied in multi-relay transmission scheme, gave a relay selection algorithm, and the performance of transmission time and energy consumption for this scheme were analyzed in detail. At last, did the simulation. The result demonstrates that, comparing with other transmission schemes, this transmission scheme improves the data throughput obviously; decreases the transmission time.
In view of cascading failure problem of scale-free fault tolerant topology in wireless sensor networks, the scale of cascading failure caused from one random fault node is deduced based on the probability generating function. The critical load value of the cascading failure is discovered under the condition of power function load distribution. The research result shows that a random fault node will cause cascading failure of the entire network when the load parameter exceeds its critical value. Simulations verify the correctness of the analytical derivation.
An exclusive-area-based connected dominating set algorithm is proposed for wireless sensor networks. Using exclusive covering and back-off delay rules, each node maintains an exclusive area where at most one dominating node exists so as to reduce the size of connected dominating set. According to node residual energy, the distribution of dominating nodes to enhance energy efficiency and balance network load are optimized. Simulation results demonstrate that the exclusive-area-based connected dominating set can reduce connected dominating set size along with a sparse distribution, and prolongs network lifetime.
Based on an eight antenna double codebook in long term evolution advanced system, the codebook selection strategy is proposed by feedback long term precoding matrix index and short term precoding matrix index separately. The long term precoding matrix indexis calculated by approximating channel capacity and the short term precoding matrix indexis searched by maximizing channel capacities. Simulation shows that the feedback overload and computational complexity are dramatically reduced performance degradation with only about 0.2dB compared with the optimal codebook selection scheme.
To improve the quality of service of handoff users in mobile cloud computing, a handoff mechanism based on mobile agent is investigated. The problems of handoff and access control are analyzed. In access control of priority handoff call model, a cost function is described in terms of benefit differences between different kinds of calls. An access control algorithm based on maximum total benefit is proposed to ensure the reliability of communication for handoff users in mobile cloud computing. Simulation shows that the proposed access control algorithm not only ensures the reliability of communication when handoff occurs, but also maximizes benefits of the system.
With the vigorous development of Chinese Internet industry, Web services are more and more applied to various domains like government, education, finance and telecom to realize services such as e-government affairs, business promotion, online trading. The security threats based on Web services are more than any time before. It is insufficient of the traditional vulnerability scan and defense technology to evaluate the threat trend faced by Web server. Aiming at the analyses on the thread trend of Web server under large-scale complex environment, this paper proposes a method and system based on Web log for security threat analyses. It extracts security threat events from a mass of logs and then makes analyses. With the use of characteristic model of threat behavior, it is able to exactly find all kinds of threats to the Websites. Synthetical comprehensive risk index for this Website is given which could contribute to the Website's aiming at strengthening its integrated defense capability.
In order to solve the problems that the propagation parameters instability of land mobile satellite (LMS) channel caused by large volume, strong flexibility of the space-borne antenna for LMS system, a LMS channel model for antenna pointing inaccuracy is proposed from the reason of vibration of space-borne antenna. The fading statistical properties of complex time series and the influence of the first order of statistics characteristics within threshold of the vibration are presented. Simulations show that the vibration of antenna has no obvious effect on first-order statistics properties, but it has great influence on second-order. Within the threshold, the influence on the statistical properties of first order is negligibly small. Considering accurate synchronization, it has little influence on the bit error rate of LMS system.
In the two-tiered wireless sensor networks, storage nodes collect data from sensor nodes and answer the queries from the sink. However, for their importance, storage nodes are attractive targets of attack and even might be compromised by the adversary. A compromised storage node may disclose sensitive data to the adversary and return juggled or incomplete sensitive data to the sink. A safe verifiable range query scheme is presented. It offers data confidentiality and query result authenticity. More importantly, it allows sink to verify query result completeness with high probability using signature aggregation technology, which greatly reduces communication cost. And based on the above scheme, it is an improvably secure verifiable range query scheme with higher probability of verification that is proposed. The theoretical analysis and simulations illustrate the schemes have high verification probability and low communication cost.
In order to improve the decoding speed of low density parity check code (LDPC) codes, a fast weighted bit flipping algorithm with partially parallel bit-chosen is proposed. In this scheme, all bits are firstly divided into several blocks according to the stochastic error distribution in the received vector. And then one bit is chosen from each block to form the candidate set of flipped bits. Finally, a proper number of bits are chosen from the candidate set and flipped to implement the decoding. Furthermore, the tree sorting and data pool methods are adopted to decrease the computational complexity of the key module of the proposed algorithm. Compared with the multi-bit flippin (MBF) algorithm by simulations, the proposed scheme and the method of hardware implement can achieve significant improvement in the decoding speed.