The use of satellite technology for oceanic air traffic control

The authors discuss the use of satellite technology for communications, navigation, and surveillance within the context of providing air traffic services and control to aircraft operating in US oceanic airspace. Particular emphasis is placed on automatic dependent surveillance, a technique that uses satellite communications channels to relay position data generated by an aircraft's on-board navigation system. Using these same channels, reliable, timely, and direct pilot/controller communications can be provided within the oceanic environment     

Radio resource management across multiple protocol layers in satellite networks: a tutorial overview

Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set‐up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end‐to‐end delay user's requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the system's efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross‐layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright © 2005 John Wiley & Sons, Ltd.     

卫星导航系统数据传输优化技术OPNET仿真

卫星导航系统由空间段、地面段和用户段3部分组成。地面段由主控站、监测站、注入站和与之互联的高性能通信网络组成,承担空间段导航的控制和星座管理,为用户安全可靠地使用整个系统提供保障服务,而高性能的互联通信网络则为地面段的数据传输提供了具有服务质量保证的平台。文中通过OPNET仿真软件,针对地面段中数据传输交换的通信质量管理问题,根据各站发送的各类信息重要性不同的特点,建立基于帧中继技术和基于帧中继甚小地球站卫星通信网络数据传输网络场景,对数据是否采取优先级传输进行仿真测试,通过数据分析,为高性能的卫星通信网络优化部署提供有意义的建议。     

Operation of Current Navigation Aids and Future Prospects

This paper is designed as a survey document to be used as an overview and introduction to the various concepts and levels of complexity of current and future aids to air navigation. Major emphasis will be placed on identifying those technical and operational characteristics of each system concept and/or mechanization that have a significant impact upon both cockpit and ground-based communications and data processing. A representative bibliography is included to provide the reader the ability to pursue the subject further from an operational as well as a technical viewpoint. The object of this paper is to identify the relationship of air navigation aids to the flow and utilization of information in air navigation and air traffic control (ATC). Air navigation aids vary widely in both complexity and performance capability and these factors have a significant impact upon communications, data processing, and display, both in the air and on the ground.     

Next generation satellite systems for aeronautical communications

U.S. airspace is reaching its capacity with the current air traffic control (ATC) system. The number of flights is constantly rising and it is estimated to be over 58 million per year by 2005. The FAA has undertaken several projects to modernize the National Airspace System (NAS) to ensure the safety of the increasing number of flights. Of special importance is the modernization of the air–ground communications infrastructure, which is the heart of the ATC. The current plan in the modernization of the air–ground communications is to migrate from analog voice only system to integrated digital voice and data system. The next generation satellite systems can be an alternative to the terrestrial air–ground systems by their low propagation and transmission delays, global coverage, high capacity and free flight suitable characteristics. In this paper, we give an overview of the current and the future ATC architectures, describe the systems and the communications issues in these systems and develop a framework in which next generation satellite systems can be integrated to the future ATC systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Integration of Voice and Data in the Wideband Packet Satellite Network

The Wideband (packet satellite) network is an experimental 3 Mbit/s communications system developed under sponsorship of the Defense Advanced Research Projects Agency and the Defense Communications Agency. This system is being used to evaluate the use of packet transmission for efficient voice communication, voice conferencing, and integration of voice and data over a satellite channel. Each station in the Wideband network consists of an earth terminal (dedicated 5 m antenna plus associated IF/RF equipment), a burst-modem and codec unit, and a station controller. Station controllers provide interfaces to host computers (including packet speech sources) and manage the allocation of the satellite channel on a TDMA demand-assigned basis. TDMA demand-assignment is implemented using a reservation-based packet-oriented protocol capableof handling traffic at multiple priority levels. The channel protocol provides a reservation-per-message mode of service (datagrams) to support transmission from bursty traffic sources and a reservation-per-call mode of service (streams) to support traffic with more regular arrival statisticS (e.g., vioce). A distributed scheduler running in every station controller eliminates the need for a central control station and minimizes network transit delay for datagram transmission as well as stream creation, modification, and deletion. In this paper we describe the protocols and mechanisms upon which the Wideband packet satellite network is based.     

Clear skies ahead [navigation systems]

Several projects aimed squarely at upgrading airplane travel, either by enhancing navigation or by improving communications between pilots and air traffic controllers, drew closer to full implementation in 2001. In mid-June, the US Federal Aviation Administration (FAA), Washington, DC, outlined its 10-year operational evolution plan to improve air travel by rolling out new technology to air traffic control facilities. All the systemwide projects target congestion in the skies and on the runways. For too long a time, too many airports were scheduling too many takeoffs or landings for any given period, driving the numbers of delays up. After 11 September, safer air travel became the burning issue. But congestion will no doubt return to prominence once airlines resume full schedules. Meantime, the global positioning system (GPS) satellite constellation and improved situational awareness tools are beginning to enhance safety now, and will alleviate congestion when it returns     

Air traffic control: satellites and artificial intelligence promiseimproved safety and efficiency

Longer-term solutions to air traffic management are examined. These include global networks of satellites for communications, navigation, and surveillance,which may upstage ground radars in the next century. Greater capability in the cockpits (including collision avoidance systems and flight computers with extensive libraries), better weather prediction and information transfer, and plans to artificial intelligence in the system are also reviewed     

基于北斗RDSS的通用航空应急通讯监视及救援系统设计

本文介绍了基于北斗 RDSS 的通用航空应急通讯监视及救援系统设计方案和工程示范内容。同时,该系统的应用示范和试运行,将为陕西省的通航飞机提供导航、通信、监视、气象、情报、救援和空中交通管制服务,提高陕西省低空空管部门的紧急事件处理能力,加强北斗系统在通用航空领域的应用。     

Multipath tolerant ranging and data transfer techniques for air-to-ground and ground-to-air links

This work addresses data acquisition problems associated with an improved air traffic control system. A mathematical theory of scattering which describes the multipath process is developed. From this model, the optimum signal structure required for ranging and communicating data through the multipath propagation medium is derived. It is shown that the Reed-Solomon Codes have near optimum properties for ranging and data communications. A baseline data transmission system for air traffic control is designed which will accommodate 4000 aircraft per second at the rate of 100 bits per second in a 60 by 120 mile area. The baseline system combines coding with frequency hopping as the best means of combating severe multipath interference. Several coding systems are compared and curves relating error rate to Eb/N0(signal-to-noise energy per bit) for a channel characterized by Rayleigh fading are presented. This paper concludes that a ground-to-air and air-to-ground high capacity data link at a reasonable cost will be feasible for an improved air traffic control system.     

Satellite communications for manned spacecraft

Future manned spaceflight programs may require continuous real-time communications between the spacecraft and the mission control center. This paper examines the feasibility of relay satellite (RS) systems to meet these requirements. Anticipated requirements range from voice and low-speed data for the Skylab and Space Shuttle to television for the Space Station. Frequencies in S, C, X, and K bands (2, 5, 8, and GHz bands, respectively) are considered. Terrestrial radio-relay links may cause interference in the mission spacecraft (MS) and RS and vice versa. Possible remedies include better control of antenna sidelobes and judicious choice of channel frequencies. It is found that INTELSAT IV offers a technically feasible means of providing voice and data communications but not TV. A new dedicated satellite system can meet the requirements with two geostationary satellites both of which are visible to a single earth station (ES) in the United States. A shared satellite system, catering to other potential users as well as to manned spacecraft, offers the possibility of reduced cost to individual users. Satellite configurations for both dedicated and shared systems are presented. The satellites can be launched by boosters of the Thor-Delta class if the links between satellite and spacecraft operate in K band.     

VOR/DME system improvements

The VOR/DME/TACAN system of short distance navigation in the United States has provided service over the past decade to all civil and military air traffic. Improvements have been incorporated which have been in the nature of refinements, assuring adequate performance for all current aircraft needs. Recent analyses indicate that continued use of VOR/DME to meet increased civil air traffic demands through 1980 will require that the system demonstrate a capability for greater accuracy for terminal area operations, an improvement in signal quality to support area navigation, and the potential for increased traffic handling capacity of the DME component. Development activities now underway indicate that such improvements are feasible. Evaluation results and new techniques are described in support of this conclusion.     

一种开放式卫星导航基带信号处理方法

传统全球导航卫星系统（GNSS）接收机基带处理模块非开放式的实现架构与多源融合导航算法的工程实现需求不够匹配，针对机载、弹载的多源融合导航需求设计提出一种开放式的卫星导航基带信号处理方法。通过将卫星导航基带处理模块的软件实现嵌入到Linux 操作系统中，独立运行信号处理进程和底层驱动调度控制，以实现基础的卫星信号捕获、跟踪、时间同步控制等软件功能。硬件实验表明，搭载所述方法的开放式卫星导航基带信号处理系统，可以通过开放式的卫星导航基带信号处理的软件实现，降低多源融合导航实现复杂度。     

Surveillance aspects of a computer-controlled traffic system

Some streets in the heart of Washington, D. C., are to become a test site for trying new traffic-control strategies. Surveillance (detection of vehicle presence and estimation of traffic conditions from this information) is an important function of this test site. Traffic parameters compatible with existing surveillance equipment and suitable for traffic control and evaluation have been selected, and their characteristics analyzed. These parameters are volume, occupancy, and queue length. Of these, only queue length uses estimation of individual vehicle motion and therefore is characterized by the greatest uncertainty. Its potential usefulness, however, is great enough to warrant considerable analytical and experimental effort. Equipment required for the surveillance task includes the vehicle detectors, communications, and digital computer. Selection of the detector is influenced by local ordinances, as well as the system requirements; the result was the choice of an inductive loop detector. For the selection of the communications several techniques were compared, and a modified tone-multiplexing approach was chosen. The computer requirements for surveillance include handling high detector input rates, performing high-speed computation and bit manipulation, and providing disk and tape storage for the surveillance-derived data.     

Network Synchronization of an Orthogonal CDMA Satellite Communication System

This paper provides the network synchronization of an orthogonal CDMA geostationary satellite system for fixed service communications. It includes the synchronization procedures, the system architecture and the performance evaluation. The main objective is to provide network wide synchronization of all uplink orthogonal CDMA transmissions. This is achieved in steps; first by providing coarse synchronization using the uplink random access channel and then fine sync using innovative tracking control mechanisms. The uplink access channel receiver utilize a parallel/serial search method for rapid code acquisition, while the code tracking of the uplink orthogonal CDMA traffic channel is based on a delay feedback early-late gate in which the sych control resides in the receiver. The proposed system is designed to minimize the onboard complexity and satisfy the performance requirements. As shown in the performance section, the requirement that all uplink transmissions are synchronized to a reference time within 10% of the chip length can be achieved. In addition, the system analysis determines the design parameters values which optimize performance.     

Pointing, acquisition and tracking for optical space communications

Free-space links between satellites provide a means of introducing increased connectivity into a satellite system. This can result in enhanced traffic capacity and extended coverage for telecommunication systems and real-time relay of instrument data to the ground for Earth observation missions. Optical links offer the potential advantages over microwave links of lower mass and power and reduced size so that they can be accommodated more easily on the satellite. However the narrow optical beamwidths involved result in stringent pointing, acquisition and tracking (PAT) requirements. This paper describes a concept for a compact PAT system which employs a passive antivibration mount to filter out high-frequency disturbances from the satellite. This is under development as part of the ESA-funded Small Optical User Terminal (SOUT) programme. The system concept, hardware implementation, and results of breadboarding critical items are presented     

IETM在导航设备可视化培训中的应用

IETM技术对于设备维护保障的信息具有极为重要的意义,尤其是针对空管导航设备信息庞杂、维护要求较高的特点,IETM具有极佳的适用性。为探索IETM在导航设备培训中应用的可行性,对导航设备可视化系统的国内外标准和规范进行了系统性研究,结合仿真模拟等目前主流的技术和成熟的工具,开发了一套用于导航设备可视化培训的软件平台,并对空管设备相关信息进行了全面的再整理。通过模拟维护平台提供了全面的技术支持、设备维修、故障诊断和维护保养等功能,实现了对空管导航类设备可视化管理与培训的总体目标。