- EI核心期刊
To improve spectrum utility efficiency, a new strategy of dynamic spectrum access is developed in cognitive wireless network. This strategy, based on spectrum pool, has higher access efficiency than instant manners. The optimal capacity and update time of spectrum pool are all studied. It is found that there is quantitative mathematical relationship between optimal capacity and system efficiency. Different update strategies of spectrum pool in licensed and unlicensed frequency bands are also proposed. Simulation manifests that, under the assumed conditions, the update interval will vary within one hour in most cases.
For reasons of low accuracy of traditional leakage, a pipeline leakage diagnosis method based on neural networks and evidence theory is presented by introducing wireless sensor networks and information fusion theory. Two sub-neural networks are established at normal node to simplify network structure. The leakage characteristic parameters of negative pressure wave and acoustic emission signals are used as input eigenvector respectively for primary diagnosis. Through making preliminary fusion results as the basic probability assignment of evidence, the impersonal valuations are realized. Finally, all evidences are aggregated at normal and sink node respectively by using the improved combination rules. The method makes full use of redundant and complementary leakage information. Numerical example shows that the proposed improves the leakage diagnosis accuracy and decreases the recognition uncertainty
Due to the effect of routing strategy and wireless interference on the throughput of wireless Mesh networks, traditional routing protocol based on the shortest path cannot achieve good performance. Thus, a routing protocol of wireless Mesh network based on network coding in unicast communications is presented．By introducing a conditional links costs, the Markovian model is adopted to design the routing metric which models the cost of a path as the cost of the first hop plus the cost of the second hop conditioned on the first hop, and so on．A path with the lowest conditional cost is chosen to transmit the network-coded packets．The simulation results show that the optimized routing metric can take better advantage of network coding while saving the network resource, as well as that the actual network throughput can be increased to about 20%．
A universal mathematical model for path selection to minimize preemption is established. The objective function for minimizing preemption cost is given. And a new method based on the selected path to minimize preemption is proposed. It lets, in priority, the label switched paths（LSPs） share more segments of links with the selected path and, in selecting LSPs to be preempted, also cross through the whole network with fewer segments of links so that the overall preemption cost is less. Simulations show that the proposed can gain less preemption cost along the given path than in only considering single segment of link, it can approximate the optimization of the objective function for minimizing preemption cost simultaneously. It has much less computational complexity and is easier to be implemented by router as well.
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A class of cubic plateaued functions has been investigated. It is shown that they have high nonlinearity without linear structure. A special condition is given that the functions are equivalent to cubic homogenous plateaued functions via the symmetric matrixes. Besides these, a method for constructing cubic homogenous plateaued functions is presented.
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In order to satisfy the application request for target tracking in wireless mobile sensor networks(WMSN), a distributed target tracking algorithm is presented. This algorithm includes two parts, one is using node leading to ensure the dynamic connectivity of WMSN, and the other is combining average consensus filter with traditional distributed data fusion architecture to realize the optimizing distributed data fusion with low cost of communication. Simulations show that target tracking effect of the proposed algorithm is good in WMSN and the performance of data fusion is better than traditional distributed data fusion algorithm.
A dynamic spectrum access algorithm based on probability density estimation is proposed to estimate the probability density of spectrum idle duration with support vector machines and evaluate the channel states, and cognitive radio users access the channel according to the states. This practicable and flexible algorithm can be adjusted adaptively. Simulation shows that the proposed algorithm will significantly reduces disruptions to primary users and improves the throughout as well as the quality of service of cognitive radio users.
A time synchronization method using shift-orthogonal Constant Amplitude Zero Auto Correlation (CAZAC) sequences constructing the time synchronization preamble is designed for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Owning to the unique properties of the designed synchronization preamble, the use of a symmetrical-correlator at the receivers can generate unit pulses for different transmitters to detect the time offsets of each antenna element. The performance of the proposed is compared with traditional methods on the condition of different time offsets in simulations, it can be found that the proposed scheme will provide higher accuracy than that caused by the distributed transmitters when detecting the different time offsets.
In open network, the usage and fuzzy set theory have been used to model the issues of trust management. The definition of trust class and the algorithm of trust-computing are discussed. By presenting the affinities coefficient, the derivation algorithm of trust has a good ability of shielding on malicious nodes. At the same time, the problem of how to define the malicious nodes and how to init the trustworthiness of the nodes are resolved. The cloud model is extended to define the trust model in formation and the parameters are discussed in detail. By proving the time decay coefficient and usage effecting coefficient, the fuzziness and dynamic variation characters are considered and resolved. The experiments are also designed to evaluate the correctness and performances of the proposed algorithm.