无人机通信网络的研究

在现代局部战争中,可采用高空长航时无人机作为通信中继平台,实现地面站与各无人机之间的通信(测控信息和任务信息传输)。本文给出了无人机系统(UAVS)通信网仿真系统的组成,设计了通信协议模块的分层呼叫协议与路由选择协议,该软件已用于UAVS通信网仿真系统。     

UAVS通信协议模块的设计与实现

在现代局部战争中,可采用高空长航时无人机作为通信中继平台,实现地面站与各任务机之间的通信(测控信息和任务信息传输)。论文给出了无人机系统(UAVS)通信网仿真模块的组成,设计了通信协议模块的分层呼叫、数据传输和飞行控制命令三个协议流程,该软件已成功地用于UAVS通信网仿真系统。     

中继式无人机自组网安全协议研究

为了提高无人机集群战术通信链路传输的连贯和安全,针对当今无人机自组链路网络的不足,提出了一种中继式无人机自组网安全协议.该协议将无人机集群划分为普通节点和中继节点,中继节点担任空间网络环境信息采集和分析的作用,并作为无人机集群协同化中心通过获得的信息为整个集群规划路径,此时新加入的无人机节点不会影响整个战术通信链路,保...     

6G无人机自组网中基于距离阈值修正的LAR路由改进方法

移动自组织网络作为无线通信的关键技术之一，与无人机结合能够实现高机动广覆盖移动通信，支持辅助地面通信、通感算融合、空天地海一体化等6G应用。路由协议是无人机自组网中的重要环节，传统基于距离的位置辅助路由协议（D-LAR）链路质量较低，路由开销较大。针对此问题，提出基于距离阈值修正的LAR路由改进方法，首先基于链路预算计算可靠通信距离，完成第一层阈值修正，提升链路可靠性，然后引入修正因子并给出路由性能优化策略，自适应减少消息广播，完成第二层阈值修正，降低路由开销。仿真结果表明，在高节点密度情况下，与D-LAR协议相比，所提出改进协议的端到端时延、分组投递率、节省重播率均具有明显的性能优势。     

一种面向小型无人机自组网的路由判据

针对小型无人机自组网节点数量多、位置动态变化、续航时间有限等特点,对经典航空路由协议(The Aeronautical Routing Protocol, AeroRP)中的判据进行改进,设计了一种基于节点生存时间的路由判据,综合考虑网络内无人机节点的剩余飞行时间、当前矢量速度、相关节点间距离和单跳最大传输距离等参数,通过对上述参数的无纲化处理得到判距,进而选取最优的下一跳节点。利用ns-3网络软件对改进判据进行仿真实现和性能分析,结果表明,新的路由判据在AeroRP中应用后,网络的传输吞吐量、准确度和时延等指标都明显好于经典的主动式路由协议——优化链路状态路由协议(Optimized Link State Routing Protocol, OLSR);并且相比经典AeroRP协议中的判据,改进判据在数据传输准确度提高的前提下,当网内节点数量超过70个时网络数据传输的吞吐量明显提升,更适合节点数量较多的应用场合。     

移动IP及其改进技术

为了在移动通信网络中运用IP协议，因特网工程任务组(Internet Engineering Task Force,IETF)制定了Mobile IP协议。Mobile IP是一种简单可扩展的全球Internet移动解决方案，使节点在切换链路时仍可保持正在进行的通信。传统的Mobile IP中要求移动节点移动到异地网络时获得转交地址，数据通过隧道经由家乡代理转发给移动节点。然而当移动节点在微移动条件下频繁移动时，传统的Mobile IP存在着许多不足。本详细介绍了移动IP的工作原理以及移动IP机制中的路由优化策略，并且针对微移动问题，从切换质量、路由更新、位置更新等方面比较了Mobile和Cellular IP、HAWAⅡ、TeleMIP等几种改进方法的性能。     

一种改进的链路容量优化路由策略

设计能够适应高移动环境下的空基自组网路由协议是目前研究的重点方向。提出了基于负载均衡的优化路由协议,该协议在获得位置信息的前提下,首先预测出通信链路的有效时间,然后在满足数据的时延、带宽以及链路有效性等多约束条件下,路由协议以均衡节点负载为优化目标,使得网络节点都能合理承担数据传输任务。仿真结果表明,设计的路由协议能够保证网络节点合理分担传输任务,充分利用链路资源,提高网络的吞吐量。     

一种基于移动IPv6协议的软切换实现方案

移动IPv6协议解决了IPv6网络中移动节点的位置更新和路由可达问题,使移动节点能够在不同IPv6子网间进行切换而不中断当前连接。但是这种切换的时延较长,影响移动IPv6网络的性能。为了减少切换时延,文章在移动IPv6协议中引入软切换技术,提出一种采用绑定更新计时器和路由优先级变换机制的软切换工程实现方案,实验结果表明,该软切换方案可以有效提高移动IPv6网络的性能。     

基于最短路径的无人机自组网改进路由算法

无人机自组网(UAV Ad Hoc Network, UANET)是一种新型的移动自组织网络形式,具有3D空间中高移动性、拓扑结构频繁变化、带宽资源有限等特点,其中路由协议是UANET中一个重要且关键的部分。由于UANET中无人机节点的移动性,不断变化的拓扑结构使得寻找适合应用在UANET中的路由协议的过程比较复杂,网络中的链路中断和无人机节点失效也会导致网络资源的损失,降低了网络的可靠性和稳定性;因此,寻找源节点和目的节点之间的传输路由协议十分必要。结合上述问题,提出了适用于无人机自组网的基于最短路径的改进路由算法,该算法可以实现多路径传输,并且从丢包率、端到端时延和抖动三个方面来评估该算法的性能。仿真结果表明,改进的路由算法在无人机随机分布的高流量场景下,获得了比已有算法更好的性能。     

基于分层代理的MIP方案研究

通过对移动蜂窝网络模型的分析,提出了一种基于IPv6协议的分层网络移动IP切换方案,利用网络层快速切换以及层管理域的适当选取,有效地减少了微移动中的切换时延;在域间切换中,引入对端通信节点与网络外部代理的直达路径,降低了三角路由对切换过程的影响。     

Mobility and connection management in a wireless ATM LAN

This paper proposes algorithms for handoff, location, and connection management in a wireless asynchronous transfer mode (ATM) local-area network (LAN). Fast handoffs while maintaining cell sequence and quality-of-service (QoS) guarantees are achieved by distributing switching functionality to base stations, and using a networking scheme based on provisioned virtual trees. A new distributed location management scheme using a minimal registration procedure and broadcasts on wired links is proposed for this LAN. The detailed signaling procedures that support the algorithms for mobility and connection management are described. Finally, an implementation of these procedures and an analysis of the measured data is presented. Measurements of service times obtained from this implementation indicate that over 100 calls/s. can be handled by each node in 50-node network with a high-percentage of mobiles (75%) relative to fixed endpoints. This is comparable to current wired ATM switch call handling throughputs, in spite of the fact that these nodes perform additional handoff and location management functions. The data also indicates handoff latency times of 1.3 ms. This validates our proposal for maintaining cell sequence while performing handoffs     

基于DNS的代理移动IPv6位置管理机制

Proxy Mobile IPv6 (PMIPv6) is designed to provide a network-based localized mobility management protocol, but it does not handle the global mobility of hosts. In this paper, we propose a location management scheme based on Domain Name System (DNS) for PMIPv6 which can support global mobility by using DNS as a location manager. In addition, to support large numbers of mobile terminals and enhance network scalability a paging extension scheme is introduced to PMIPv6.To evaluate the proposed location management scheme, we establish an analytical model, formulate the location update cost and the paging cost,and analyze the influence of the different factors on the total signaling cost. The performance results show that our proposed scheme outperforms the basic PMIPv6 under various parameters in terms of reducing the signaling overhead and the proposed scheme reduces signaling overhead compared to the basic PMIPv6.     

基于医院网络的交换机配置文件批量备份技术

在数据信息时代中,智能化的数据信息网络成了医院基础信息业务的重要组成部分,随着医院网络化信息建设业务的不断深化,基础数据信息的稳定性变得至关重要。医院的网络信息系统主要由交换机、汇聚交换机以及数台接入层组成,在一线的日常管理中,需要强化对基础数据信息的维护与备份,最大限度地保障医院基础业务的开展。文中首先综述了医院交换机硬件配置备份的场景,其次阐释了交换机数据处理中的SNMPv2c协议与TFTP协议,并从网络拓扑结构设计以及基于WinSock控件的配置备份的代码实现中,总结了医院网络交换机的定期自动备份方法,还给出了控制点发生错误时的应对策略,希望能为医院计算机网络的交换机优化配置与信息化管理提供参考和借鉴。     

大容量光电交换技术研究

高效灵活地利用已有带宽,充分、高效和灵活地调度和控制各种粒度的业务,保证业务的生存性是光交换网络亟需解决的技术问题。为此文章探讨了融合光通路数据单元（ODUk）/分组的新型交换机制、光纤/ODUk/分组混合交换机制。文章认为新的交换机制和多粒度交换结构是超大容量实现和构建的关键,业务多粒度生存性及协调机制、业务适配、带宽分配、管理和控制、损伤监测等是需要研究的重点问题。     

Trading latency for energy in densely deployed wireless ad hoc networks using message ferrying

Wireless mobile ad hoc networks (MANETs) have the potential for use in important application environments, such as remote environmental monitoring, where energy resources are limited. Efficient power management is necessary to allow these networks to operate over a long period of time. One of the key factors affecting the design of power management mechanisms is the routing protocol in use within the network. In this paper, we investigate the Message ferrying (MF) routing paradigm as a means to save energy while trading off data delivery delay. In MF, special nodes called ferries move around the deployment area to deliver messages for nodes. While this routing paradigm has been developed mainly to deliver messages in partitioned networks, here we explore its use in a connected MANET. The reliance on the movement of ferries to deliver messages increases the delivery delay if a network is not partitioned. However, delegating message delivery to ferries provides the opportunity for nodes to save energy by aggressively disabling their radios when ferries are far away. To exploit this feature, we present a power management framework, in which nodes switch their power management modes based on knowledge of ferry location. We evaluate the performance of our scheme using ns-2 simulations and compare it with a multihop routing protocol, dynamic source routing (DSR). Our simulation results show that MF achieves energy savings as high as 95% compared to DSR without power management and still delivers more than 98% of messages. In contrast, a power-managed DSR delivers many fewer messages than MF to achieve similar energy savings. In the scenario of heavy traffic load, the power-managed DSR delivers less than 20% of messages. MF also shows robust performance for highly mobile nodes, while the performance of DSR suffers significantly. Thus, delay tolerant applications can use MF rather than a multihop routing protocol to save energy efficiently when both routing approaches are available.     

The sink tree paradigm: connectionless traffic support on ATM LAN's

Asynchronous transfer mode (ATM) is a connection-oriented technology in which all communication is based on virtual connections established prior to the transfer of data. It is expected that the bulk of traffic carried by the ATM network will be data traffic, e.g., local area network (LAN) internetwork traffic. Hence, a major issue regarding ATM is the support for connectionless (datagram) traffic. A scheme for the efficient support for connectionless traffic in ATM LANs based on trees of virtual connections is proposed. In this scheme, a sink tree is built for every switch in the LAN. Each tree provides an efficient means of routing connectionless traffic from any switch in the network to the sink switch (root) of the tree. The sink tree solution may also be used to broadcast connectionless messages in the reverse direction. The trees can easily be updated to adapt to topological changes or congestion in the network. A protocol for refreshing the tree structure using the ATM switch routing tables is described. An adaptive rate control solution, in conjunction with fast back pressure at the ATM layer, is presented. It is shown that this scheme achieves high utilization of available bandwidth for connectionless traffic, has low cell loss probability, and small overhead     

An Efficient Handover Mechanism Using the General Switch Management Protocol on a Multi‐Protocol Label Switching Network

Using the general switch management protocol on a multi‐protocol label switching network, we present an efficient method for handling handovers. The proposed method directly changes an established path into a new path for supporting a handover. Our investigation reveals the effects of the proposed scheme and demonstrates that this method significantly reduces signaling costs and delays.     

Demonstration of connection-oriented optical burst switching network utilising PLC and MEMS switches

The first demonstration of a connection-oriented optical burst data switching network constructed with PLC and MEMS switches employing GMPLS control is reported. Optical burst data switching in a six-node photonic network using the general switch management protocol (GSMP) is successfully, demonstrated.     

The QPSX MAN

The authors discuss QPSX (queued packet and synchronous switch), a distributed switch/network that will fulfil the requirements of a public metropolitan area network (MAN) and has wide telephone industry support. The dual-bus architecture of QPSX and its extension, the looped-bus architecture, are described. The architecture of the public MAN is examined, particularly with respect to QPSX as a proposal for IEE P802.6 standardization. The distributed queueing protocol, segmentation and reassembly scheme, and reliability features of the QPSX network are discussed.<>     

Management of cognitive radio ad hoc networks using a congestion‐based metric

In this paper, we propose a new network management protocol to address the unique challenges of managing cognitive radio ad hoc networks that have distributed, multihop architectures with dynamic spectrum availability. We focus on performance management for these networks, and address the problem of network congestion for secondary users, because of its significant impact on data throughput. Specifically, we define a performance metric, the average congestion level of the network, and derive it analytically as a function of the primary users’ activities and the secondary users’ strategy. For practical implementation, we further propose a cluster‐based management architecture that utilizes a designated central manager and cluster heads that function as distributed managers. The cluster heads collect information from multiple layers of the protocol stack using new MIB (management information base) variables to capture the characteristics of cognitive radio ad hoc networks, such as the location‐dependent spectrum availability. The objective of the management action is to utilize a network‐level view of the congestion situation in the network by directing the secondary users to select the highest‐quality links available and avoid congested clusters. This hierarchical networkmanagement design allows us to take advantage of its scalability to achieve near‐real‐time management. Numerical results demonstrate the effectiveness of the proposed scheme. Copyright © 2013 John Wiley & Sons, Ltd.