Communication delays in distributed environments is an important and challenging problem that has not been adequately addressed. Communication delays are particularly insidious in air traffic control, and space and military operations, where communication and information sharing are paramount to team success. For the purposes of this research, we define communication delay as the time interval between a team member speaking a message (sender) and when another team member (recipient) hears it. The goal of this research is to better understand the effect of communication delays on team collaboration and team processes to maximize distributed team performance. This paper will explore the issue of communication delays in network-enabled environments, and describe an experiment developed to better understand the effects of communication delays on distributed team member trust, shared understanding, and satisfaction. Research questions are as follows: (1) What effect do audio communication delays have on distributed team trust, shared understanding (task accuracy), satisfaction, and cognitive workload; and (2) What effect does a video channel have on distributed team trust, satisfaction, and team member cognitive workload, when team member communication is delayed. For the purposes of this research, we will focus on synchronous audio and video communication technologies.

关键词：息交流；局域网；语音传输；通信网络

查看摘要 索取原文[37页]

NASA has developed an experimental flight payload (referred to as the Space Communication and Navigation (SCAN) Test Bed) to investigate software defined radio (SDR) communications, networking, and navigation technologies, operationally in the space environment. The payload consists of three software defined radios each compliant to NASAs Space Telecommunications Radio System Architecture, a common software interface description standard for software defined radios. The software defined radios are new technology developments underway by NASA and industry partners launched in 2012. The payload is externally mounted to the International Space Station truss to conduct experiments representative of future mission capability. Experiment operations include in-flight reconfiguration of the SDR waveform functions and payload networking software. The flight system will communicate with NASAs orbiting satellite relay network, the Tracking and Data Relay Satellite System at both S-band and Ka-band and to any Earth-based compatible S-band ground station. The system is available for experiments by industry, academia, and other government agencies to participate in the SDR technology assessments and standards advancements.

关键词：空间通信；通信卫星；无线电通信；试验台；无线电设备

查看摘要 索取原文[35页]

Independent Component Analysis (ICA) has largely been applied to the biomedical field over the past two decades and only recently extended to the processing of complex non-circular sources. The feasibility and performance of complex ICA to extract a weak co-channel interfering communications signal from a television broadcast signal is investigated in this thesis. The performance of three algorithms, complex maximization of non-Gaussianity (CMN) by Novey et al., RobustICA by Zarzoso et al., and complex fixed-point algorithm (CFPA) by Douglas, over varied interference-to-noise ratios (INR) for a fixed signal-to- interference ratio (SIR) is obtained by simulation. The communication signals examined for the weak interferer are binary phase-shift keying (BPSK), four- level rectangular quadrature amplitude modulation (4-QAM), and 16-level rectangular quadrature amplitude modulation (16-QAM), and the television broadcast signals are North American standard, Advanced Television Systems Committee (ATSC) and European standard, Digital Video Broadcasting - Terrestrial (DVB-T). Improved performance and sensitivity to the prewhitening step present in the ICA implementations are shown as the number of sensors increases.

关键词：通信和系统;无线电信号;算法;数字录音系统;提取

查看摘要 索取原文[71页]

When a group of independent actors wish to coordinate their actions with one another, each actor uses internal state information combined with information known about all other actors' states to decide what to do. This generally requires some form of communication to synchronize state information between all actors. Since communication is often costly and not all parts of an actor's state change between synchronization attempts using a method such as rsync can reduce the number of bits transmitted, and thus, the communications cost. However, rsync is designed for pair-wise interactions. In wireless communications, group-wise synchronization which is more e cient than rsync, is possible. This paper describes Dandelion, an algorithm that builds on the ideas of the rsync algorithm to e ciently distribute information to all actors in a group over a shared broadcast medium. The algorithm is described in detail, as well as some experimental results using the algorithm on robots. Finally, theoretical comparisons to rsync and generic multicast trees are provided, as well as experimental comparisons between an implementation and a current version of the rsync program, showing that the costs of transmission are as low as a multicast tree, without the associated cost of building or maintaining a tree.

关键词：信息交流；同步（电子产品）；无线通信算法；通信和无线电系统；通信网络

查看摘要 索取原文[16页]

DOD has invested heavily in its logistics operations, estimating that its overall spending on logistics--including supply chain management--was more than $171 billion in fiscal year 2011. GAO has previously reported that one of the most complex and vital tasks facing DOD is managing its supply chain to effectively and efficiently provide spare parts, food, fuel, and other critical supplies in support of U.S. military forces. GAO has identified DOD's supply chain management as a high-risk area and has previously reported that limitations in asset visibility--including the visibility of assets in transit--make it difficult to obtain timely and accurate information on the assets that are present in the theater of operations. As part of GAO's work to update its high-risk areas, this report assesses the extent to which DOD (1) is aware of its components' efforts to improve in-transit visibility and (2) has a strategy to achieve in-transit visibility that includes the key elements of a comprehensive strategic plan. To conduct these assessments, GAO obtained and analyzed information from the defense components, reviewed and analyzed relevant defense policies, guidance, and plans regarding in-transit visibility, and interviewed officials from DOD and the defense components.

关键词：物流管理；军事战略；资产；通信网络；信息系统

查看摘要 索取原文[32页]

Purpose of the Space Network Ground Segment Sustainment (SGSS) is to implement a new modern ground segment that will enable the NASA Space Network (SN) to deliver high quality services to the SN community for the future The key SGSS Goals: (1) Re-engineer the SN ground segment (2) Enable cost efficiencies in the operability and maintainability of the broader SN.

关键词：空间通信；地面支持系统；系统工程；系统兼容性

查看摘要 索取原文[19页]

Providing long-distance non-line-of-sight control for unmanned ground robots has long been recognized as a problem, considering the nature of the required high-bandwidth radio links. In the early 2000s, the DARPA Mobile Autonomous Robot Software (MARS) program funded the Space and Naval Warfare Systems Center (SSC) Pacific to demonstrate a capability for autonomous mobile communication relaying on a number of Pioneer laboratory robots. This effort also resulted in the development of ad hoc networking radios and software that were later leveraged in the development of a more practical and logistically simpler system, the Automatically Deployed Communication Relays (ADCR). Funded by the Joint Ground Robotics Enterprise and internally by SSC Pacific, several generations of ADCR systems introduced increasingly more capable hardware and software for automatic maintenance of communication links through deployment of static relay nodes from mobile robots. This capability was finally tapped in 2010 to fulfill an urgent need from theater. 243 kits of ruggedized, robot- deployable communication relays were produced and sent to Afghanistan to extend the range of EOD and tactical ground robots in 2012. This paper provides a summary of the evolution of the radio relay technology at SSC Pacific, and then focuses on the latest two stages, the Manually-Deployed Communication Relays and the latest effort to automate the deployment of these ruggedized and fielded relay nodes.

关键词：无线电中继系统；通信和无线电系统；特设网状网络；无线电链路

查看摘要 索取原文[10页]

Road traffic crashes are a global public health problem, contributing to an estimated 1.3 million deaths annually (1). Known risk factors for road traffic crashes and related injuries and deaths include speed, alcohol, nonuse of restraints, and nonuse of helmets. More recently, driver distraction has become an emerging concern (2). To assess the prevalence of mobile device use while driving in Belgium, France, Germany, the Netherlands, Portugal, Spain, the United Kingdom (UK), and the United States, CDC analyzed data from the 2011 EuroPNStyles and HealthStyles surveys. Prevalence estimates for self-reported talking on a cell phone while driving and reading or sending text or e-mail messages while driving were calculated. This report describes the results of that analysis, which indicated that, among drivers ages 1864 years, the prevalence of talking on a cell phone while driving at least once in the past 30 days ranged from 21in the UK to 69in the United States, and the prevalence of drivers who had read or sent text or e-mail messages while driving at least once in the past 30 days ranged from 15in Spain to 31in Portugal and the United States. Lessons learned from successful road safety efforts aimed at reducing other risky driving behaviors, such as seat belt nonuse and alcohol-impaired driving, could be helpful to the United States and other countries in addressing this issue (2,3). Strategies such as legislation combined with high-visibility enforcement and public education campaigns deserve further research to determine their effectiveness in reducing mobile device use while driving. Additionally, the role of emerging vehicle and mobile communication technologies in reducing distracted drivingrelated crashes should be explored.

关键词：移动设备；分心驾驶；交通事故；通信

查看摘要 索取原文[24页]

The Global System for Mobile Communications (GSM) Association predicts that there will be nearly 50 billion connected devices by 2025, nearly ten times the worlds predicted human population. ABI estimates that through 2012, Machine-to-Machine connected devices will grow by 100m units per year by 2012.1 An M2M module uses a device to capture an event (temperature, activation of airbags, etc.), which is relayed through a network, either wireless or wired, to an application, such as a software program, that translates the captured event into meaningful information (e.g., ice warning, crash notification). An M2M device typically converts analog sensor data into internet protocol (IP) packets for transmission over a communications medium. M2M applications are often characterized by the absence of a human decision maker directly controlling communications intensity, frequency and costs, though there are M2M applications in the transportation sector that also require interaction with drivers. M2M devices can be transmitted over a variety of communications mediums including mobile satellite services, cellular networks, and even combinations of carriers and carrier coverage areas across several networks. Hybrid wireless solutions include intermediary devices such as cellular modems connected to an M2M endpoint via wireless local, personal area or near field communications networks such as Wi-Fi, ZigBee, Bluetooth or Radio Frequency Identification (RFID). The most common communications system for M2M in use today in North America is second generation (2G) wireless, using either General Packet Radio Service (GPRS) or Short Message Service (SMS), which uses signaling protocols that set up and tear down voice calls to transmit small amounts of data.

关键词：汽车；通讯；无线通讯；软件程序；移动卫星服务

查看摘要 索取原文[7页]

Today's nuclear power plant (NPP) instrumentation uses current loops and voltage-based communications sometimes compromised by radio frequency interference (RFI), also called electromagnetic interference (EMI). Copper-based communications technology also relies on insulation that may degrade after decades of exposure to NPP environments and can be flammable. Wireless technologies offer the potential for greater expansion in instrumentation in a plant that could augment human performance, provide additional data on plant equipment and component status, and facilitate online assessment of the material condition of plants. Wireless communications capabilities may substantially reduce the cabling cost, but a number of technology and security issues must be resolved. One of the greatest capital cost contribution from I&C systems arises from cable installation. The trend toward more effective, efficient operation and maintenance will require many additional sensors beyond the number of nuclear and process sensors at a conventional NPP. These additional sensors are needed to enable monitoring of real-time process variables, structural components, movable equipment, portable devices, and warehouse/inventory areas, but will exacerbate the cabling complexity and cost. Wireless technologies offer the potential for greater expansion in instrumentation in a plant that could augment human performance, provide additional data on plant equipment and component status, and facilitate online assessment of the material condition of plants.

关键词：电站;通信网络;传感器;费用;电力电缆

查看摘要 索取原文[51页]