Trunking vs. conventional radio systems

Correctional Service Canada (CSC) has recently replaced the aging, out-of-date radio communications systems in all major CSC facilities with new conventional digital radio systems. Based on very specific and restrictive operational requirements coupled with developments in digital radio technology and the Associated Public Communications Officers (APCO) Project 25 digital radio standards, it was determined that digital radio communications would best meet CSC's needs. The CSC national radio replacement program was completed in March 2000. Switching to a digital radio communications system gave CSC an opportunity to consider changing the existing radio system from a number of conventional, single-site systems to a trunking system. Areas to be considered when determining the architecture for a radio communication network, whether radio trunking systems or conventional radio systems should be used, are presented, In addition, the paper will also outline the requirements and measures taken to keep the radio communication network active and operational while the equipment was converted from an analog technology to a digital one     

Green UAV communications for 6G: A survey

Unmanned Aerial Vehicles (UAVs) have received a wide range of attention for military and commercial applications. Enhanced with communication capability, UAVs are considered to play important roles in the Sixth Generation (6G) networks due to their low cost and flexible deployment. 6G is supposed to be an all-coverage network to provide ubiquitous connections for space, air, ground and underwater. UAVs are able to provide air-borne wireless coverage flexibly, serving as aerial base stations for ground users, as relays to connect isolated nodes, or as mobile users in cellular networks. However, the onboard energy of small UAVs is extremely limited. Thus, UAVs can be only deployed to establish wireless links temporarily. Prolonging the lifetime and developing green UAV communication with low power consumption becomes a critical challenge. In this article, a comprehensive survey on green UAV communications for 6G is carried out. Specifically, the typical UAVs and their energy consumption models are introduced. Then, the typical trends of green UAV communications are provided. In addition, the typical applications of UAVs and their green designs are discussed. Finally, several promising techniques and open research issues are also pointed out.     

认知无线网络及其频谱管理技术

认知无线网络通过不同种类的无线网络体系结构之间的并存和动态频谱接入技术可以为移动用户提供高带宽的服务。高效的频谱管理技术是这一新型网络面临的主要挑战之一。为了更好的理解认知无线网络,文章简单回顾了认知无线电技术,对认知无线网络的结构及特点进行了深入研究,明确了认知无线网络频谱管理的主要任务,并结合认知无线电当前的发展状况对认知无线网络频谱管理技术进行了总结分析。     

Firewire in modern integrated military avionics

High performance communications, navigation, and identification (CNI) functions on modern military aircraft are increasingly required for mission readiness. The operation of simultaneous waveforms through an integrated avionics rack of shared resources becomes a test in moving data rapidly from one signal processing stage to the next. The IEEE 1394, or Firewire, is a commercial high bandwidth bus whose 64-bit addressing and maximum 400 Mbits/second throughput satisfies this demanding military avionics interconnect need. The challenge in applying this commercial product to integrated avionics is the requirement to seamlessly add message priority encoding. By having message priorities, the slower strategic communications links will not impair the performance of higher data rate tactical communications, thereby avoiding potentially life-threatening bottlenecks. The flight environment imposes additional challenges to ruggedize the cabling between integrated avionics racks and to utilize the full capabilities of the Firewire bus. A discussion of the physical, data link, network, and transport layers, as used in avionics applications will be done. Additionally, the versatility of 1394 in military avionics with its variable channel sizes, bandwidth on demand, hierarchical addressing, and upgrade to 800 and 1600 Mbps with a 64-bit wide data path, is emphasized. Finally, system maintenance advantages of 1394's hot pluggable features are discussed, with an eye toward cost reduction on the flight line and total operational time of the aircraft avionics systems     

Distributed flight control system using fiber distributed datainterface (FDDI)

The design of fault-tolerant distributed control systems is discussed. The application described is a generic flight control system (FCS) for a fighter aircraft. The system is designed for high redundancy and expandability to meet various requirements. The communication network is based on the fiber distributed data interface (FDDI), which provides a high level of electromagnetic interference resistance and reliability. The choice of fiber optic media also provides an extremely high bandwidth and tremendous growth capability for future communications needs. This study is not specific to FDDI or flight control systems. The methods and configurations presented should be applicable to many real-time control implementations     

High speed plastic networks (HSPN): a new technology for today'sapplications

Decades ago, glass fiber promised to be the future of communications offering large bandwidth, low attenuation, and electromagnetic compatibility. For the long haul applications, this promise has been fulfilled. Today, glass fibers have yielded simple, reliable, and economic means of communicating worldwide. However, when it comes to shorter distances and rugged environments, glass fiber optics has not been the answer. Unforeseen rapid developments in software and display technology have enabled communications in the form of multimedia, E-mail, web pages, and video conferencing. These developments are pushing data rates higher and higher in application environments that are more severe, uncontrolled and require shorter connected intensive links. To achieve desired data rates and electromagnetic compatibility (EMC) using copper systems, shielded cable and connectors or parallel links are necessary, driving up cost and complexity. Glass fiber optic systems provide more than adequate bandwidth and superior EMC but cannot offer a cost effective, robust, user-friendly system. Recent developments have poised plastic optical fiber (POF) to fill the physical layer gap. This paper will discuss the recent developments in plastic fiber including appropriate application space, types of plastic optical fiber, ARPA-funded HSPN team, and recent POF developments     

Software radios: Survey, critical evaluation and future directions

A software radio is defined as a set of digital signal processing (DSP) primitives, a metalevel system for combining the primitives into communication system functions (transmitter, channel model, receiver, etc.), and a set of target processors on which the software radio is hosted for real-time communications. The performance of enabling hardware technologies is related to software radio requirements, portending a decade of shift from hardware radios toward software intensive approaches. Computational models and architecture are discussed, stressing the need for topological consistency of radio functions and host architectures. A layered topology-oriented design approach encapsulated in a canonical open architecture software radio model is presented. The model provides a unified mathematical framework for quantitative analysis of algorithm structures, host architectures, and system performance for CAD     

WiMAX dynamnic beamforming antenna

This presents our design and development of an 8-channel adaptive beaniforming antenna for new developments in radio technology: the emergence of chip-based components implementing the recently completed IEEE 802.16d-2004 (WiMAX) radio standard [1-4]. WiMAX offers the potential of long-range (up to 50 miles) and high bandwidth (up to 50 Mb~s) radio links. Although the new WiMAX standard offers the potential for using smart, adaptive antennas, this functionality has not been implemented. Our design will serve as a common platform for testing adaptive array algorithms including direction of arrival (DOA) estimation, beamforming, and adaptive tracking, as well as complete wireless communication with a WiMAX Radio. Heavy emphasis will be placed on ease of implementation in a multi-channel / multi-user environment. In the future, we hope to expand this interface to support dynamic radio channel selection via direct interaction with radio hardware or implementation of a cognitive radio system.     

网络化综合化的天地一体化信息系统探讨

针对天地联网中空间与地面网络节点的信息高效互通、交换及应用需求,利用电子信息综合化技术实现高度综合化的多功能通用平台,构建天基以及地面系统"资源池",结合SDN(Software Defined Network,软件定义网络)架构、网络协议与路由网关,将有效解决网络中由于物理界限造成的信息阻隔,实现物理资源与边界虚拟化、信息流程智能化的天地一体化天基信息系统,提高天基信息资源利用率、信息按需定制及高效共享能力.结合天基信息系统发展趋势,探讨了天地一体化信息系统的网络化、综合化应用建议和研究重点,梳理了天、地节点综合化、网络化的关键技术方向.     

Optimal trajectory and downlink power control for multi-type UAV aerial base stations

Unmanned Aerial Vehicles (UAVs) enabled Aerial Base Stations (UABSs) have been studied widely in future communications. However, there are a series of challenges such as interference management, trajectory design and resource allocation in the scenarios of multi-UAV networks. Besides, different performances among UABSs increase complexity and bring many challenges. In this paper, the joint downlink transmission power control and trajectory design problem in multi-type UABSs communication network is investigated. In order to satisfy the signal to interference plus noise power ratio of users, each UABS needs to adjust its position and transmission power. Based on the interactions among multiple communication links, a non-cooperative Mean-Field-Type Game (MFTG) is proposed to model the joint optimization problem. Then, a Nash equilibrium solution is solved by two steps: first, the users in the given area are clustered to get the initial deployment of the UABSs; second, the Mean-Field Q (MFQ)-learning algorithm is proposed to solve the discrete MFTG problem. Finally, the effectiveness of the approach is verified through the simulations, which simplifies the solution process and effectively reduces the energy consumption of each UABS.     

Hybrid partition- and network-level scheduling design for distributed integrated modular avionics systems

Distributed Integrated Modular Avionics (DIMA) develops from Integrated Modular Avionics (IMA) and realizes distributed integration of multiple sub-function areas. Time-triggered network provides effective support for time synchronization and information coordination in DIMA systems. However, inconsistency between processing resources and communication network destroys the time determinism benefiting from partitions and time-triggered mechanism. To ensure such time determinism and achieve guaranteed real-time performance, system design should collectively provide a global communication scheme for messages in network domain and a corresponding execution scheme for partitions in processing domain. This paper firstly establishes a general DIMA model which coordinates partitioned processing and time-triggered communication, and then proposes a hybrid scheduling algorithm using Mixed Integer Programming to produce feasible system schemes. Furthermore, incrementally integrating new functions causes upgrades or reconfigurations of DIMA systems and will generate integration cost. To control such cost, this paper further develops an optimization algorithm based on Maximum Satisfiability Problem and guarantees that the scheduling design for upgraded DIMA systems inherit their original schemes as much as possible. Finally, two typical cases, including a simple fully connected DIMA system case and an industrial DIMA system case, are constructed to illustrate our DIMA model and validate the effectiveness of our hybrid scheduling algorithms.     

Open systems avionics network to replace MIL-STD-1553

This paper is a proposal for a future method of avionics data communication. The need for this proposal results from the shortcomings in the current avionics architecture, video distribution network, and in the MIL-STD-1553 data communication system. The separately wired video and data communication systems can be combined to save weight, which is especially critical for rotorcraft. Aircraft, once fielded, have limited capacity for modification and improvement due to fixed computer throughput and processing performance, network bandwidth, and space available in the avionics equipment bays. The changes proposed by this paper are to be made in conjunction with the replacement of the redundant computer boxes with open system avionics functions on industry standard circuit cards. This open architecture approach was developed over the last ten years and is now being implemented in many aircraft applications including the F-22 and the RAH-66 programs. The V-22 rotorcraft, which although just entering production, is being modified for joint service customers where modern computer performance and expanded data network bandwidth is needed. The changes of this proposal will fill this need, reduce the weight of upcoming production models, and provide growth or spare capability so that additional video and data components can be added with minimal effect on existing components. This paper examines the current V-22 avionics video and data communication hardware and wiring and propose a new implementation of open system architecture standards with integrated digital video and data communication based on ANSI standard copper fibre channel     

Networks of low-Earth orbit store-and-forward satellites

A slotted multiaccess protocol is proposed for networks of low-Earth orbit store-and-forward communications satellites. Networks of this type would provide communication between low cost geographically distributed Earth stations, and would be particularly attractive in areas where conventional terrestrial communications systems were not available. Applications of this type include data acquisition and remote process monitoring. The proposed protocol incorporates time division multiplexing (TDM) on the downlink, slotted Aloha with collision resolution on the uplink, and an automatic repeat request (ARQ) algorithm. Since the network connectivity is intermittent, analysis of networks of this type is difficult. Nevertheless, relationships among the performance parameters for a general network are deduced, and performance of three particular network configurations is studied via simulation     

下一代数据中继卫星系统发展思考

通过系统阐述中继卫星系统的发展过程,给出了主要国家和组织的中继卫星系统技术体制和现状.再结合卫星、载人航天器和深空探索的未来发展趋势,分析了下一代中继卫星系统的发展需求.在此基础上,从体系结构、卫星平台、链路调制体制、网络协议等方面,探讨并给出了下一代中继卫星系统的发展趋势和技术途径.为满足未来近地、深空航天任务,以及临近、低空快速移动用户的不同要求,节约系统成本,下一代中继卫星系统将向专业化和与其他系统融合的方向发展:星间链路将增加激光链路,数据速率可达到10 Gbit/s以上;多址业务成为主用,同时支持用户数能力将极大提高;对于链路调制体制,在采用CR(Cognitive Radio,认知无线电)和SDR(Software Defined Radio,软件定义无线电)技术的基础上,可实现实时自适应调整和根据需求加载配置;数据传输将采用网络化方式,天地间构成一体化DTN(Delay Tolerant Network,容延迟网络).     

Design and analysis of truss deployable antenna mechanism based on a novel symmetric hexagonal profile division method

As the deployment, supporting, and stability mechanisms of satellite antennas, space-deployable mechanisms play a key role in the field of aerospace. In order to design truss deployable antenna supporting mechanisms with large folding rate, high accuracy, easy deployment and strong stability, aiming at the geometric division of the parabolic reflector, a novel method based on symmetric hexagonal division and its corresponding modular truss deployable antenna mechanism is proposed, and the original method based on asymmetric triangular division and its corresponding mechanisms are presented for comparative analysis. Then, the screw theory is employed to analyze the mobility of different mechanisms. Furthermore, the improved three-dimensional mesh method is used to divide the reflector surface of a large parabolic antenna designed by the two different methods, and the profile accuracy and the type of links are taken as the evaluation indexes to quantitatively analyze the division results. Finally, a three-dimensional model of the modular deployable mechanism based on the symmetric hexagonal design is developed, and the deployable mechanisms with different configurations based on the two design methods are compared and analyzed from the mechanical perspective. The research results provide a good theoretical reference for the design of deployable truss antenna mechanisms and their application in the aerospace field.     

分布式电推进飞机动力系统评估优化方法

以电推进飞机的动力系统作为研究对象,开展了以下研究工作：采用电力系统潮流计算方法,分析了采用高压直流供电体制的分布式电推进飞机电气系统,模拟了其在稳定运行状态与断路故障状态下的能量流动关系,同时分析了直流电压等级对电气系统的影响。搭建了完整的分布式电推进飞机动力系统仿真模型,依据基于时间和基于高度的飞行剖面,对比分析了纯电推进与涡轮电推进架构在推进功率、推进效率与航程3个评价指标上的优劣。建立了动力系统典型部件的参数化模型,并使用符号规划算法对建立的参数化模型进行了优化计算,比较了传统涡轮推进与涡轮电推进架构下动力系统质量与燃油消耗率间的优化权衡关系。研究结果为分布式电推进飞机混合动力系统的设计提供了有价值的正向设计方法。     

面向互联飞机的空天地网络一体化融合研

随着数字化技术的发展，民用飞机会在飞行各阶段产生大量数据，这些数据的利用及处理将提升飞机运营的经济性、安全性与舒适性。为了适应未来互联飞机对海量数据交换与传输的迫切需求，满足民用飞机对无线通信服务质量(QoS)的要求，有必要充分利用并合理分配多种现有和未来的空天地无线通信链路资源。分析了互联飞机的概念、生态系统及其对空天地网络的网络需求，研究了地面异构移动互联网采用的紧耦合和松耦合两种融合方法，采用了网络体系融合、IP网络和非IP网络融合及终端融合等多种融合手段，提出了适应于多种通信链路与网络体系特点的一体化空天地无线通信链路的融合架构，并对网络协议栈、网络安全以及集成验证提出了初步考虑。     

Bandwidth maximization for satellite laser communication

Free space optical communication between satellites networked together can make possible high speed communication between different places on Earth. The basic free space optical communication network includes at least two satellites. In order to communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. The pointing systems for laser satellite communication suffer during tracking from vibration due to electronic noise, background radiation from interstellar objects such as Sun, Moon, Earth, and Stars in the tracking field of view, and mechanical impact from satellite internal and external sources. Due to vibrations the receiver receives less power. This effect limits the system bandwidth for given bit error rate (BER). In this research we derive an algorithm to maximize the communication system bandwidth using the transmitter telescope gain as a free variable based on the vibration statistics model and the system parameters. Our model makes it possible to adapt the bandwidth and transmitter gain to change of vibration amplitude. We also present an example of a practical satellite network which includes a direct detection receiver with an optical amplifier. A bandwidth improvement of three orders of magnitude is achieved in this example for certain conditions, as compared with an unoptimized system     

Capacities of mobile air/ground radio communication systemsemploying cylindrical cells

Cylindrical cells represent actual service volumes used in terminal areas (airports) for air traffic control (ATC) communications between pilots and ground controllers. The channel capacities of simplex and duplex frequency division multiplexing (FDM) mobile air/ground (A/G) radio communication systems employing cylindrical cells are compared assuming a network of identical cylindrical cells and a dedicated radio channel per group of aircraft and its ground controller. The two systems are compared considering both cochannel and adjacent channel interferences for analog and digital modulation. Then, capacities of duplex FDM and code division multiplexing (CDM) are compared under the same assumptions for digital modulation. The capacity of FDM depends mainly on the frequency reuse distance while the capacity of CDM is limited by the self users interference. This work shows that the capacity ratio of duplex and simplex FDM systems depends on the cell dimensions. It also shows that considering ATC requirements, FDM provides a higher capacity than CDM for all the cell dimension ranges considered     

基于P2P的一种负载饱和避免技术研究

在点对点体系结构的分布式虚拟环境系统中,由于客户机节点的计算能力和带宽的异构性,以及发生在客户机程序之间交互信息量的不同,会导致一些客户机出现负载饱和。一台客户机的负载饱和不仅影响本机程序的运行,也会对周围其他的客户机的运行产生影响,这限制了分布式虚拟环境系统的性能。研究提出了一种在点对点体系结构的分布式虚拟环境系统中避免客户机负载饱和的技术,试验结果显示了所提出的方法有效地改进了系统的性能。