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找到报告 44248 篇 当前为第 3629 页 共 4425

所属行业:信息传输、软件和信息技术服务业

  • 36281.模拟全球AeroMACS机场地面站天线的功率传输极限以避免干扰卫星移动业务馈线上行链路

    [信息传输、软件和信息技术服务业,计算机、通信和其他电子设备制造业] [2014-07-28]

    The Aeronautical Mobile Airport Communications System (AeroMACS), which is based upon the IEEE 802.16e mobile wireless standard, is expected to be implemented in the 5091 to 5150 MHz frequency band. As this band is also occupied by Mobile Satellite Service feeder uplinks, AeroMACS must be designed to avoid interference with this incumbent service. The aspects of AeroMACS operation that present potential interference are under analysis in order to enable the definition of standards that assure that such interference will be avoided. In this study, the cumulative interference power distribution at low Earth orbit from transmitters at global airports was simulated with the Visualyse Professional software. The dependence of the interference power on antenna distribution, gain patterns, duty cycle, and antenna tilt was simulated. As a function of these parameters, the simulation results are presented in terms of the limitations on transmitter power from global airports required to maintain the cumulative interference power under the established threshold.
    关键词:电脑程序;机场;地面站;通信;移动通信系统
  • 36282.国土安全办公室国家互操作性现场操作指南应急通信1.4版

    [计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-28]

    The National Interoperability Field Operations Guide (NIFOG) is a technical reference for emergency communications planning and for radio technicians responsible for radios that will be used in disaster response. The NIFOG includes rules and regulations for use of nationwide and other interoperability channels, tables of frequencies and standard channel names, and other reference material, formatted as a pocket-sized guide for radio technicians to carry with them. If you are not familiar with interoperability and mutual aid communications, start with the How to Use the National Interoperability Field Operations Guide section.
    关键词:通信和广播系统;紧急情况;应急计划;互操作性
  • 36283.NASAGRC无人机项目:通信建模与仿真状态

    [信息传输、软件和信息技术服务业,计算机、通信和其他电子设备制造业] [2014-07-28]

    The integration of Unmanned Aircraft Systems (UAS) in the National Airspace represents new operational concepts required in civil aviation. These new concepts are evolving as the nation moves toward the Next Generation Air Transportation System (NextGen) under the leadership of the Joint Planning and Development Office (JPDO), and through ongoing work by the Federal Aviation Administration (FAA). The desire and ability to fly UAS in the National Air Space (NAS) in the near term has increased dramatically, and this multi-agency effort to develop and implement a national plan to successfully address the challenges of UAS access to the NAS in a safe and timely manner is well underway. As part of the effort to integrate UAS in the National Airspace, NASA Glenn Research Center is currently involved with providing research into Communications systems and Communication system operations in order to assist with developing requirements for this implementation. In order to provide data and information regarding communication systems performance that will be necessary, NASA GRC is tasked with developing and executing plans for simulations of candidate future UAS command and control communications, in line with architectures and communications technologies being developed and/or proposed by NASA and relevant aviation organizations (in particular, RTCA SC-203). The simulations and related analyses will provide insight into the ability of proposed communications technologies and system architectures to enable safe operation of UAS, meeting UAS in the NAS project goals (including performance requirements, scalability, and interoperability), and ultimately leading to a determination of the ability of NextGen communication systems to accommodate UAS. This presentation, compiled by the NASA GRC team, will provide a view of the overall planned simulation effort and objectives, a description of the simulation concept and status of the design and development that has occurred to date.
    关键词:飞机通讯;通信网络;无线电通信;无人驾驶飞机系统
  • 36284.卫星控制:长期规划和采用商业实践可以提高国防部的操作

    [信息传输、软件和信息技术服务业] [2014-07-28]

    DOD manages the nation's defense satellites, which are worth at least $13.7 billion, via ground stations located around the world. These ground stations and supporting infrastructure perform three primary functions: monitoring the health of the satellite; ensuring it stays in its proper orbit; (activities collectively known as satellite control operations), and planning, monitoring, and controlling the execution of the overall mission of the satellite. Based on the House Armed Services Committee Report and discussions with defense committee staff, GAO (1) reviewed the Air Force's satellite control operations to assess the potential for fragmentation or duplication, (2) assessed the status of modernization efforts, (3) identified any commercial practices that could improve the Air Force's satellite control operations, and (4) identified any barriers to implementing them. GAO reviewed modernization funding documents, related studies and interviewed DOD and 7 commercial satellite companies, from a nongeneralizable sample selected in part because of their companies' satellite capabilities.
    关键词:军事卫星;卫星网络;通信卫星;国防科;
  • 36285.大规模分布式内存平台实现分层MPI的性能表征

    [计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-28]

    The building blocks of emerging Petascale massively parallel processing (MPP) systems are multi-core processors with four or more cores as a single processing element and a customized network interface. The resulting memory and communication hierarchy of these platforms are now exposed to application developers and end users by creating a hierarchical or multi-core aware message-passing (MPI) programming interface and by providing a handful of runtime, tunable parameters that allows mapping and control of MPI tasks and message handling. We characterize performance of MPI communication patterns and present strategies for optimizing applications performance on Cray XT series systems that are composed of contemporary AMD processors and a proprietary network infrastructure. We highlight dependencies in its memory and network subsystems, which could influence production-level applications performance. We demonstrate that MPI micro-benchmarks could mislead an application developer or end user since these benchmarks often do not expose the interplay between memory allocation and usage in the user space, which depends on the number of tasks or cores and workload characteristics. Our studies show performance improvements compared to the default options for our target scientific benchmarks and production-level applications.
    关键词:通信;并行编程;基准;通讯执行情况;内存
  • 36286.退伍军人事务部:涉嫌通过Internet连接的弗吉尼亚敏感数据的传输回顾

    [计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-28]

    We conducted this review to determine the merits of an allegation that VA was transmitting sensitive data, including Personally Identifiable Information (PII) and internal network routing information, over unencrypted telecommunications carrier networks. The VA Midwest Health Care Network, also known as the Veterans Integrated Service Network (VISN) 23 within the Veterans Health Administration, serves more than 400,000 veterans enrolled to receive medical care residing in Iowa, Minnesota, Nebraska, North Dakota, South Dakota and portions of Illinois, Kansas, Missouri, Wisconsin, and Wyoming. In May 2012, a complainant contacted the VA Office of Inspector General (OIG) Hotline, alleging that certain VA medical centers (VAMCs) were transmitting sensitive information, including PII and internal network routing information, over unencrypted telecommunications carrier networks. More specifically, the complainant indicated that unencrypted data were transmitted among various VAMC networks using the South Dakota Network, which functions as the local telecommunications carrier network.The complainant alleged that these security violations occurred at VAMCs located in Fort Meade, SD; Omaha, NE; and Sioux Falls, SD, which are in VISN 23. To determine the merits of this Hotline allegation, we visited the three VAMCs identified in the complaint letter. We interviewed VA's Office of Information and Technology (OIT) personnel to gain an understanding of existing data transmission practices and associated controls.
    关键词:退伍军人(军事人员);通信网络;计算机通信;数据传输
  • 36287.提高具有非对称极化MIMO的UXS网络可用性

    [信息传输、软件和信息技术服务业,计算机、通信和其他电子设备制造业] [2014-07-28]

    To improve the efficiency of communications among unmanned systems, the research focused on the novel use of asymmetric polarized MIMO and network availability. The dissertation objective was to maintain the highest network availability for a mobile ad hoc network with heterogeneous communication capabilities. Using a hybrid dual-polarized Rayleigh fading channel model, asymmetric antenna configurations were studied in simulation for bit error rate and capacity. For a 1 x 1 configuration, polarization reciprocity was used to exploit the polarized channel knowledge, thereby maximizing received uplink power. The optimum gains to maximize uplink capacity were also derived for varying channel cross-polarization values. Larger configurations of 2 x 1 and 2 x 2 were investigated, including overlays of orthogonal space-time block coding, which improved diversity performance in the polarized channels. Extending these link results to realistic scenarios with unmanned systems, a reference point group mobility model including large-scale propagation was proposed to compute the network availability. Another scenario detailed robot exploration of unknown environments, which included large-scale path loss models. While deploying the network, the factors of exploration strategies, signal thresholds and routing were shown to impact the availability metric. Lastly, four extensible formation models were analyzed for their influence on network availability.
    关键词:无线通信的天线配置;不对称;渠道;通信和无线电系统;配置;
  • 36288.土耳其武装部队卫星优化

    [信息传输、软件和信息技术服务业,计算机、通信和其他电子设备制造业] [2014-07-28]

    Advancing technologies in smallsats provide remote sensing and communications capabilities achievable with a constellation of satellites at a reasonable cost to meet military needs. Like any other nation looking for a cheap but effective solution in that area, Turkey might also benefit from a replacement of its remote sensing assets. Currently, Turkish Armed Forces rely on a limited number of reconnaissance aircraft and Unmanned Aerial Vehicles, which do not provide real-time or near real-time remote sensing capabilities. Near real-time remote sensing needs for the Turkish warfighter dictates that the Turkish Armed Forces reach that capability as soon as possible. Likewise, replacing its conventional communication radios with satellite communication devices would also fulfill its warfighter needs. While current communication devices have physical limitations in Turkey's mountainous terrain and the surrounding seas, satellite communication capability would provide a wider coverage, and for specific frequencies, it might provide better resistance to jamming and interference. For the benefit of the Turkish Armed Forces' communications needs, a satellite constellation must be optimized such that effective coverage will be achieved with the least number of satellites to provide a reasonable cost. In this study, satellite constellation optimization for the Turkish Armed Forces will be achieved using Analytical Graphics, Inc.'s Systems Tool Kit software for simulation and analysis of several possible communications and remote sensing satellite constellations covering Turkish territory and surrounding seas. The Concept of Operations (CONOPS) for a smallsat constellation will be described and an optimized smallsat constellation will be modeled using STK software. The resulting data will be analyzed and discussed in the form of a recommendation that would benefit the Turkish Armed Forces.
    关键词:通信;卫星通讯;计算机程序;计算机模拟
  • 36289.企业移动设备安全管理准则

    [计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-28]

    Mobile devices, such as smart phones and tablets, typically need to support multiple security objectives: confidentiality, integrity, and availability. To achieve these objectives, mobile devices should be secured against a variety of threats. The purpose of this publication is to help organizations centrally manage the security of mobile devices. Laptops are out of the scope of this publication, as are mobile devices with minimal computing capability, such as basic cell phones. This publication provides recommendations for selecting, implementing, and using centralized management technologies, and it explains the security concerns inherent in mobile device use and provides recommendations for securing mobile devices throughout their life cycles. The scope of this publication includes securing both organization-provided and personally-owned (bring your own device, BYOD) mobile devices.
    关键词:信息安全;移动设备;管理计划和控制;可用性;通信安全
  • 36290.用于室内无线通信的数据传输系统

    [计算机、通信和其他电子设备制造业,信息传输、软件和信息技术服务业] [2014-07-28]

    The indoor communications is a new market in the future.This Article introduces one data transmission system based with OFDM signals.The overview of the communication system and synchronization theory background will be introduced.The simulation results shown in this article implies that this OFDM system achieves excellent performance for indoor wireless communication.
    关键词:室内无线通信;数据传输系统;OFDM;同步
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