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Zhang X.-J.,Beihang University | Zhang X.-J.,National Key Laboratory of CNS ATM | Guan X.-M.,Beihang University | Guan X.-M.,National Key Laboratory of CNS ATM | And 3 more authors.
Communications in Theoretical Physics | Year: 2013

In recent years, the transportation system has been faced by increasing challenge in congestion and inefficiency, and research in traffic network has become a significant area of interest. In this paper, we introduce a dynamic-information-based (DIB) queueing strategy into network traffic model under the efficient routing strategy. DIB makes a packet with higher priority to be delivered if there are less packets travelling along its path from the current node to the destination. It is found that, compared with the traditional first-in-first-out (FIFO) queueing strategy, DIB can effectively balance the traffic load of the system via delaying packets to be delivered to congested nodes. Although the network capacity has no obvious changes, some other indexes which reflect transportation efficiency are efficiently improved in the congestion state. Besides, extensive simulation results and discussions are provided to explain the phenomena. The results may provide novel insights for research on traffic systems. © 2013 Chinese Physical Society and IOP Publishing Ltd.

Bai Y.,Beihang University | Bai Y.,National Key Laboratory of CNS ATM | Zhang X.,Beihang University | Zhang X.,National Key Laboratory of CNS ATM | And 2 more authors.
2014 IEEE China Summit and International Conference on Signal and Information Processing, IEEE ChinaSIP 2014 - Proceedings | Year: 2014

Traditional communication system in the L-band (960-1164 MHz) operates in the frequency gaps between the Distance Measuring Equipment (DME) channels. However, this will lead to a waste of the frequency resources. In this paper, a spectrum spread communication system which is overlapped with the DME is considered. Moreover, it utilizes the extended Complementary Code Keying (CCK) sequence to get a higher bandwidth usage efficiency and balance out the interference from the DME. Simulation results show that the extended CCK encoding system and the DME can share the common channel without degradation in the Bit Error Ratio (BER) performance. © 2014 IEEE.

Wang Y.,National Key Laboratory of CNS ATM | Feng Y.,Queensland University of Technology | Li R.,National Key Laboratory of CNS ATM
24th International Technical Meeting of the Satellite Division of the Institute of Navigation 2011, ION GNSS 2011 | Year: 2011

The paper explores methods and algorithms used to generate, apply and validate covariance matrices of GPS orbits in the context of position solution. In general, the research of satellite orbit error is threefold. The first is covariance matrix generation of satellite orbit error which may include systematic orbit biases or sudden changes in the orbit solution. The next is to determine and test "Bad" satellites which have large orbit error with the highest probability. The third is to validate what integrity benefit can be obtained if orbit covariance matrices are considered in estimation of user positioning solutions. However, the existing integrity studies have not addressed these issues directly yet. The paper starts with a general description of a satellite integrity orbit monitoring problem and computing orbital covariance matrices from different orbital solutions in real time. Next the paper describes covariance propagations in the least square navigation solutions. The method to determine 'bad' satellites is then analyzed preliminarily. Experimental analysis with GPS orbits of several hours and several widely distributed ground GNSS stations are performed to demonstrate the proposed integrity concepts and determination algorithms. The results have shown that the effects of large broadcast orbital errors on the user solutions can indeed be effectively reduced by considering the orbital covariance matrices estimated.

Lei J.,Beihang University | Lei J.,National Key Laboratory of CNS ATM | Zhang X.,Beihang University | Zhang X.,National Key Laboratory of CNS ATM | And 2 more authors.
Advances in Intelligent Systems and Computing | Year: 2014

Airspace congestion has become more and more serious in recent years due to the sharp increase of aircraft which has caused many unsafe factors and economic losses. Hence, how to assign flights to reduce congestion and delay has attracted much more attention. However, the flight assignment problem is very difficult to deal with it because in general has multiple objectives and involves in a large amount of flights. In this paper, we propose a new flight assignment method based on parallel evolution algorithm (PEA), which has great superiority for largescale complicated problem. Besides, a left–right probability migration topology is presented to further improve the optimization capability. Experiments on real data of the national route of China show that our method outperforms the current three flight assignment approaches. Moreover, the congestion and delay are effectively alleviated. © Springer-Verlag Berlin Heidelberg 2014.

Sun X.,Beihang University | Sun X.,National Key Laboratory of CNS ATM | Wandelt S.,Beihang University | Wandelt S.,National Key Laboratory of CNS ATM | And 2 more authors.
Chinese Control Conference, CCC | Year: 2016

In this study, we perform an empirical analysis of air transportation systems as networks of countries. We build three network variants based on worldwide ticket data from the year 2013 and identify patterns of air passenger flow between countries as induced by network centrality metrics. These metrics, understood as observables about countries, are then exploited to estimate the similarity of countries in the global network. We detect community structures and find that communities largely coincide with the continental division of the world. Our research contributes to a better understanding of international air passenger flow patterns and potential control mechanisms against natural or human intended disruptions. © 2016 TCCT.

Wang T.,Beihang University | Wang T.,National Key Laboratory of CNS ATM | Sun X.,Beihang University | Sun X.,National Key Laboratory of CNS ATM | And 2 more authors.
Chinese Control Conference, CCC | Year: 2016

Many real-world systems can be seen as complex networks, where nodes denote elements in the systems and links denote relationships between elements. Since most of the real-world systems are vulnerable under disruptions, it is necessary to perform research on network robustness. However, finding the optimal attack on networks is a NP-hard problem, thus many methods based on ranking certain network metrics are proposed, for their low computational time complexity. Although strategies can be obtained quickly according to the ranking methods, the quality of the strategies is unsatisfying, because no single metric can represent all the properties of a network. In this paper, we propose a ranking-free method to attack networks. The main idea of our method is to identify components, which are likely to be in the final network after attack. Our research targets a trade-off between expensive optimal attacks and fast ranking-based heuristics. The evaluations, both on random networks and real-world networks, show that our method behaves better than popular ranking methods. © 2016 TCCT.

Huaxian L.,Beihang University | Huaxian L.,National Key Laboratory of CNS ATM | Yanbo Z.,Beihang University | Yanbo Z.,National Key Laboratory of CNS ATM | And 3 more authors.
Proceedings of the 2011 IEEE 5th International Conference on Cybernetics and Intelligent Systems, CIS 2011 | Year: 2011

Instead of assigning 3D trajectories of the flights in some sectors under traditional Air Traffic Management (ATM), the Route Network Flow Assignment (RNFA) problem is redefined in the new generation of aviation. It needs to properly assign both the 3D trajectories and the time slots (4D trajectories) for all the flights in the whole airspace, aiming at maximizing the use of airspace and alleviating the air traffic congestion. It is an optimization problem in essence and has to optimize all the flights' 4D trajectories. This problem is challenging because of the large scale of the flights and the relativity among them. To deal with it, this paper puts forward an effective method. The main idea is to introduce a divide-and-conquer strategy to divide this large scale problem into small ones. During which, a dynamic grouping operator is adopted, while considering the relativity among the flights. For the optimization of the subcomponents, a dual coding Differential Evolution (DE) method is proposed to adapt the high efficiency DE to this discrete optimization problem. The experimental results show that our method can solve the RNFA problem both effectively and efficiently and outperforms the current approaches. Moreover, the application of the proposed methodology can also be served as a benchmark application in the fields of the large scale problems' optimization. © 2011 IEEE.

Lei C.,Beihang University | Lei C.,National Key Laboratory of CNS ATM | Zhang J.,Beihang University | Zhang J.,National Key Laboratory of CNS ATM
Chinese Journal of Aeronautics | Year: 2012

The detection of sparse signals against background noise is considered. Detecting signals of such kind is difficult since only a small portion of the signal carries information. Prior knowledge is usually assumed to ease detection. In this paper, we consider the general unknown and arbitrary sparse signal detection problem when no prior knowledge is available. Under a Neyman-Pearson hypothesis-testing framework, a new detection scheme is proposed by combining a generalized likelihood ratio test (GLRT)-like test statistic and convex programming methods which directly exploit sparsity in an underdetermined system of linear equations. We characterize large sample behavior of the proposed method by analyzing its asymptotic performance. Specifically, we give the condition for the Chernoff-consistent detection which shows that the proposed method is very sensitive to the ℓ 2 norm energy of the sparse signals. Both the false alarm rate and the miss rate tend to zero at vanishing signal-to-noise ratio (SNR), as long as the signal energy grows at least logarithmically with the problem dimension. Next we give a large deviation analysis to characterize the error exponent for the Neyman-Pearson detection. We derive the oracle error exponent assuming signal knowledge. Then we explicitly derive the error exponent of the proposed scheme and compare it with the oracle exponent. We complement our study with numerical experiments, showing that the proposed method performs in the vicinity of the likelihood ratio test (LRT) method in the finite sample scenario and the error probability degrades exponentially with the number of observations. © 2012 Elsevier Ltd. All rights reserved.

Zhang X.J.,Beihang University | Zhang X.J.,National Key Laboratory of CNS ATM | Guan X.M.,Beihang University | Guan X.M.,National Key Laboratory of CNS ATM | And 4 more authors.
Science China Information Sciences | Year: 2013

Conflict resolution (CR) plays a crucial role in safe air traffic management (ATM). In this paper, we propose a new hybrid distributed-centralized tactical CR approach based on cooperative co-evolutionary named the CCDG (cooperative co-evolutionary with dynamic grouping) strategy to overcome the drawbacks of the current two types of approaches, the totally centralized approach and distributed approach. Firstly, aircraft are divided into several sub-groups based on their interdependence. Besides, a dynamic grouping strategy is proposed to group the aircraft to better deal with the tight coupling among them. The sub-groups are adjusted dynamically as new conflicts appear after each iteration. Secondly, a fast genetic algorithm (GA) is used by each sub-group to optimize the paths of the aircraft simultaneously. Thirdly, the aircraft's optimal paths are obtained through cooperation among different sub-groups based on cooperative co-evolutionary (CC). An experimental study on two illustrative scenarios is conducted to compare the CCDG method with some other existing approaches and it is shown that CCDG which can get the optimal solution effectively and efficiently in near real time, outperforms most of the existing approaches including Stratway, the fast GA, a general evolutionary path planner, as well as three well-known cooperative co-evolution algorithms. © 2013 Science China Press and Springer-Verlag Berlin Heidelberg.

Su J.,Beihang University | Su J.,National Key Laboratory of CNS ATM | Zhang X.,Beihang University | Zhang X.,National Key Laboratory of CNS ATM | And 2 more authors.
Lecture Notes in Electrical Engineering | Year: 2013

Conflict resolution becomes a worldwide urgent problem to guarantee the airspace safety. The existing approaches are mostly short-term or middle-term which obtain solutions by local adjustment. 4D-Trajectory conflict resolution (4DTCR), as a long-term method, can give better solutions to all flights in a global view. 4DTCR involved with China air route network and thousands of flight plans is a large and complex problem which is hard to be solved by classical approaches. In this paper, the cooperative coevolution (CC) algorithm with random grouping strategy is presented for its advantage in dealing with large and complex problem. Moreover, a fast Genetic Algorithm (GA) is designed for each subcomponent optimization which is effective and efficient to obtain optimal solution. Experimental studies are conducted to compare it to the genetic algorithm in previous approach and CC algorithm with classic grouping strategy. The results show that our algorithm has a better performance. © 2013 Springer-Verlag.

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