In Cognitive Radio Network (CRN),where Primary User (PU) and multiple Secondary Users (SUs) wish to communicate with their corresponding receivers simultaneously over fading channels,spectrum utilization and efficient resource allocation are both significant points for CRN.Interference between PU and SUs should be eliminated in order to realize spectrum sharing.Multi-user resource allocation with the target of maximizing the spectral efficiency of SUs and satisfying the proportional rate constraint between SUs are proposed under the conditions of total SU interference constraint.An adaptive low-complexity suboptimal algorithm for subcarrier and power joint allocation is presented based on Rate Adaptive (RA) criterion,where adaptive subcarrier allocation is performed by assuming equal power distribution,while each subcarrier is assigned in accordance with subcarrier efficiency function.Moreover,linear water-filling algorithm for power allocation is applied within each subcarrier.Simulation results indicate that,with the proposed adaptive subcarrier allocation,spectral efficiency of multiple SUs is superior to traditional subcarrier power joint allocation algorithm.Low computational complexity and adaptive features make it available for implementation.

关键词：认知无线电网络;自适应子载波分配;衰落信道;子载波效率

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The current focus of ACAWS is on the needs of the flight controllers. The onboard crew in low-Earth orbit has some of those same needs.

关键词：飞行控制;预警系统;故障;系统健康监测;

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Parallel algorithms for sparse matrix-matrix multiplication typically spend most of their time on inter-processor communication rather than on computation, and hardware trends predict the relative cost of communication will only increase. Thus, sparse matrix multiplication algorithms must minimize communication costs in order to scale to large processor counts. In this paper, we consider multiplying sparse matrices corresponding to Erdos-Renyi random graphs on distributed-memory parallel machines. We prove a new lower bound on the expected communication cost for a wide class of algorithms. Our analysis of existing algorithms shows that, while some are optimal for a limited range of matrix density and number of processors, none is optimal in general. We obtain two new parallel algorithms and prove that they match the expected communication cost lower bound, and hence they are optimal.

关键词：算法;乘法;稀疏矩阵;通信

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The California Department of Transportation (Caltrans) has contracted with the Western Transportation Institute (WTI) at Montana State University (MSU) to develop an Automated Safety Warning Controller. The controller will interface with roadside devices such as sensors and signs. The controller will allow for automated data collection and application of best practice algorithms to analyze sensor data and to actuate related warning messages to motorists. For instance, wind warning messages might be actuated on a changeable message sign (CMS) when wind speed, as read from a sensor, exceeds a given threshold. The controller allows for remote access and administration via standard IP-based connections established through POTS dialup or direct connection to wired access points, but is not dependent on those connections for operation. In other words, the controller will remain locally operable in the event that outside communication is unavailable for whatever reason. Even if a communication link to the outside is unavailable, the controller will continue to monitor and control its associated devices. This functionality is especially important in rural areas where weather conditions make communications services unreliable when the functionality is needed most. The standardized use of such a device would likely result in decreased maintenance costs, improved reliability, and greater flexibility in implementation when compared with one-of-a-kind deployments.

关键词：预警系统;安全设备;流量控制;自动化;算法;通信

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The objective of this research is to explore the technical soundness of a very large, cross-shaped, parabolic, sparse aperture antenna extending 75 m from the bus. Specifically, describing the environment of the satellite, the effect of fabrication error on the structure and the remaining error budget for the system. The methodology involves creation of an ideal truss structure, to which all others are compared. A uniform distribution of proportional errors up to 1e-5 is introduced into the truss members. lengths and the models are subjected to a static Finite Element Analysis. A solution for the surface normal error is addressed using Lagrange multipliers. The goal is to hold the surface normal error for the entire satellite below a root mean square of 15 mm. The analysis yields a surface error of less than 1.53 mm, well within requirements. Despite the enormous size of the antenna reflector, and tight diameter/surface error ratio of 10,000 required for L-band communication, the system seems feasible. The values achieved for truss induced surface errors are in line with established techniques for analyzing full aperture, and strip, mesh antennas. With the mesh reflector and truss largely defined, nearly half of the 15 mm error budget remains.

关键词：空军研究;天线孔径;天线阵列;通信卫星

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Most communication in the modern era takes place over some type of cyber network, to include telecommunications, banking, public utilities, and health systems. Information gained from illegitimate network access can be used to create catastrophic effects at the individual, corporate, national, and even international levels, making cyber security a top priority. Cyber networks frequently encounter amounts of network traffic too large to process real-time threat detection efficiently. Reducing the amount of information necessary for a network monitor to determine the presence of a threat would likely aide in keeping networks more secure. This thesis uses network traffic data captured during the Department of Defense Cyber Defense Exercise to determine which features of network traffic are salient to detecting and classifying threats. After generating a set of 248 features from the capture data, feed-forward artificial neural networks were generated and signal-to-noise ratios were used to prune the feature set to 18 features while still achieving an accuracy ranging from 83- 94. The salient features primarily come from the transport layer section of the network traffic data and involve the client/server connection parameters, size of the initial data sent, and number of segments and/or bytes sent in the flow.

关键词：通信和广播系统;通信网络;数码网络;控制论;特征选择;

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关键词：战略规划;通信;事故预防;干预措施

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Researchers in the area of cognitive radio often investigate the utility of dynamic spectrum access as a means to make more efficient use of the radio frequency spectrum. Many studies have been conducted to nd ways in which a secondary user can occupy spectrum licensed to a primary user in a manner which does not disrupt the primary user's performance. This research investigates the use of opportunistic access in a frequency hopping radio to mitigate the interference caused by other transmitters in a contentious environment such as the unlicensed 2.4 GHz region. Additionally, this work demonstrates how dynamic spectrum access techniques can be used not only to prevent interfering with other users but also improve the robustness of a communication system.

关键词：认知无线电;通讯和广播系统;动态频谱接入;节能检测;

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The global positioning system (GPS) market is a fast changing, highly competitive market. Products change frequently as they try to provide the best customer experience for a service that is based on the need for real-time data. Two major functions of the GPS unit are to correctly report traffic jams on a drivers route and provide an accurate and timely estimated time of arrival (ETA) for the driver whether he/she is in a traffic jam or just following driving directions from a GPS unit. This study measures the accuracy of traffic jam reporting by having Personal Navigational Devices (PNDs) from TomTom and Garmin and phone apps from TomTom, INRIX, and Google in the same vehicle programmed to arrive at the same destination. We found significant differences between the units in terms of their ability to recognize an upcoming traffic jam. We also found differences in how well the devices responded to jams when driving on surface streets versus highways, and whether the jams were shorter or longer in length. We see potential for auto manufacturers to employ real-time traffic in their new vehicles, providing potential growth for real-time traffic providers through access to new vehicles as well as the aftermarket.

关键词：驾驶辅助系统;电子设备;全球定位系统;导航设备

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The U.S. Geological Survey and the National Aeronautics and Space Administration are cooperatively investigating the utility of unmanned vehicles for near-real-time autonomous surveys of geophysical data collection. Initially focused on unmanned ground vehicle collection of magnetic data, this cooperative effort has brought unmanned surveying, precision guidance, near-real-time communication, on-the-fly data processing, and near-real-time data interpretation into the realm of ground geophysical surveying, all of which offer advantages over current methods of manned collection of ground magnetic data. An unmanned ground vehicle mission has demonstrated that these vehicles can successfully complete missions to collect geophysical data, and add advantages in data collection, processing, and interpretation. We view the current experiment as an initial phase in further unmanned vehicle data-collection missions, including aerial surveying.

关键词：航测;数据收集;地球物理数据;地面车辆;磁数据

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