System engineering practices for complex systems and networks now require that requirement, architecture, and concept of operations product development teams, simultaneously harmonize their activities to provide timely, useful and cost-effective products. When dealing with complex systems of systems, traditional systems engineering methodology quickly falls short of achieving project objectives. This approach is encumbered by the use of a number of disparate hardware and software tools, spreadsheets and documents to grasp the concept of the network design and operation. In case of NASA's space communication networks, since the networks are geographically distributed, and so are its subject matter experts, the team is challenged to create a common language and tools to produce its products. Using Model Based Systems Engineering methods and tools allows for a unified representation of the system in a model that enables a highly related level of detail. To date, Program System Engineering (PSE) team has been able to model each network from their top-level operational activities and system functions down to the atomic level through relational modeling decomposition. These models allow for a better understanding of the relationships between NASA's stakeholders, internal organizations, and impacts to all related entities due to integration and sustainment of existing systems. Understanding the existing systems is essential to accurate and detailed study of integration options being considered. In this paper, we identify the challenges the PSE team faced in its quest to unify complex legacy space communications networks and their operational processes. We describe the initial approaches undertaken and the evolution toward model based system engineering applied to produce Space Communication and Navigation (SCaN) PSE products. We will demonstrate the practice of Model Based System Engineering applied to integrating space communication networks and the summary of its results and impact. We will highlight the insights gained by applying the Model Based System Engineering and provide recommendations for its applications and improvements.

关键词：航天通信，通信网络;系统工程;数据集成;系统集成;体系结构

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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;天线配置;不对称;通道;通信和广播系统;配置

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关键词：通讯和广播系统；报警系统；信息传播；移动设备

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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

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关键词：指挥和控制系统；通信网络；联合军事行动；时间序列分析

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We validate through simulation and experiment that artificial magnetic conductors (AMC s) can be well characterized by a transmission line model. The theoretical bandwidth limit of the in-phase reflection can be expressed in terms of the effective RLC parameters from the surface patch and the properties of the substrate. It is found that the existence of effective inductive components will reduce the in-phase reflection bandwidth of the AMC. Furthermore, we propose design strategies to optimize AMC structures with an in-phase reflection bandwidth closer to the theoretical limit.

关键词：带宽;导线；卫星通信；空间通信；基材

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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

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Breakthroughs in satellite and fiber-optic telecommunication networks and related technologies currently enable almost instantaneous transmission of information across the globe. Many private and public organizations have become used to depending on the global information grid to perform their daily operations. A firm with headquarters in the United States can interact with multiple affiliates and customers located on the other side of the globe in real time. With such technological advances, the need has arisen for virtual collaboration means that allow personnel at geographically diverse sites to interact and communicate effectively. Having the most effective means of virtual collaboration and ensuring they are used in the most effective way are paramount to achieving error-free, real-time communication, a goal that is particularly important for military operations. In this report we address the virtual collaboration needs of organizations whose components have wide geographic distribution, such as U.S. military intelligence organizations or U.S. military operational units.

关键词：音频会议；协作技术；电脑媒介通讯；会议（通讯）

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The introductory chapter begins with the basic definitions of virtual reality, virtual presence and related concepts. It provides an overview of the history of virtual reality, from its origins in the 1950s to the present day. It also covers some of the most important applications, from flight simulators to biomedical uses. Finally, it briefly describes the main feedback loops used in virtual reality and the human biological systems used to interpret and act on information from the virtual world.

关键词：虚拟现实；生物医学；人体生物系统

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This research develops a feature-based MAP classification system and applies it to classify several common pulse compression radar and communication modulations. All signal parameters are treated as unknown to the classifier system except SNR and the signal carrier frequency. The features are derived from estimated duty cycle, cyclic spectral correlation, and cyclic cumulants. The modulations considered in this research are BPSK, QPSK, 16-QAM, 64-QAM, 8- PSK, and 16-PSK communication modulations, as well as Barker coded, Barker coded, Barker coded, Frank coded, Px49 coded, and LFM pulse compression modulations. Simulations show that average correct signal modulation type classificationC > 90is achieved for SNR > 9dB, average signal modulation family classificationC > 90is achieved for SNR > 1dB, and an average communication versus pulse compression radar modulation classificationC > 90is achieved for SNR > -4dB. Also, it is shown that the classification cation performance using selected input features is sensitive to signal bandwidth but not to carrier frequency. Mismatched bandwidth between training and testing signals caused degraded classification cation ofC 10- 14over the simulated SNR range.

关键词：自动调制分类阳离子;自动化;通信

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