QoS on LEO satellites

This paper discusses the role played by wireless network infrastructure in mobile commerce applications. The user's perception of service quality depends on the available resources and capabilities of the network. The new generation of low earth orbit (LEO) mobile satellite networks, deployed at altitudes ranging from 500 km to 2000 km, are well suited to handle multimedia traffic and to offer end-users equipped with hand-held devices at low cost-per minute access to network services. A wide range of multimedia services and applications are expected to provide users with QoS based asynchronous transfer mode (ATM) technology. LEO satellite networks provide significant wide area coverage, unique broadcast capability, ability to meet different QoS requirements, the ability to communicate with hand-held devices and low cost access. The main resources in the LEO networks are satellite radio bandwidth and the buffer capacity of the onboard ATM switch. The most important ATM resource management function is connection and call admission control. The real objective of this article is to introduce the general framework of resource reservation in multimedia LEO satellite networks which offers a unified approach to handle all the important aspects of resource reservation and radio-resource management functions required by E-commerce and mobile commerce applications.     

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources. It provides the network with better quality-of-service (QoS) guarantees, such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks. Simulation results show that, compared with other bandwidth allocation schemes, the proposed scheme offers very low call dropping probability for real-time connections while, at the same time, keeping resource utilization high. Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods. Translated from Journal on Communications, 2006, 27(8): 10–17 [译自: 通信学报]     

应急情况下最少转发节点的传感器网络组播路由树算法

在抢险救灾等应急情况下,传感器网络的节点能量更为有限。为减少无用转发的能量消耗,利用无线信道的广播特性,根据广播子树删除思想,提出一种基于最短路由树、具有最少转发节点的组播路由树生成算法。对该算法进了证明和详细分析,并针对实际需要,给出使用范围更广泛的分布式实现方法。仿真分析说明,算法的分布式实现方法可减少ODMRP的转发节点数,大大降低数据发送次数,接收成员节点较多时尤为明显。最少转发节点的组播路由树的网络总开销最小,是延长网络生存时间的有效方法。     

Performance analysis of low earth orbit satellites for power system communication

In this paper the main performances of communication services based on low earth orbit satellites (LEOs) have been analyzed in order to evaluate their suitability for a typical set of power system monitoring functionalities. As an experimental test bed, an intelligent electronic device (IED) for remote monitoring and protection of power components equipped with a bi-directional communication system based on the LEO satellites of the Globalstar^® consortium has been prototyped. Thanks to the adoption of this facility the main parameters characterizing the performance of the satellite TCP/IP services have been evaluated. They comprise in particular the connection time, the degradation of service and data latency for both packet and asynchronous data services. The experimental results obtained show that the application of LEO satellites based communication technologies exhibits a set of intrinsic advantages that could be particularly useful in several fields of power system communication.     

吸氧辅助电极的应用——用于低轨道卫星全密封镉镍蓄电池

在镉镍全密封蓄电池内部增加吸氧辅助电极———Ag Hg电极 ,同时采取两阶段充电控制等措施 ,从而成功地将地球同步轨道卫星镉镍蓄电池的第三电极信号电压充电控制方法应用于低轨道卫星上 ,不仅避免了低轨道卫星镉镍蓄电池大电流充电后期造成的极化对充电控制信号的影响 ,而且改善了充电后期效率 ,减少热量的产生     

Resource management in LEO satellite networks

To provide truly global coverage needed by increased Personal Communication Services (PCS), a new generation of mobile satellite networks has been proposed. These low Earth orbit (LEO) mobile satellite networks handle multimedia traffic and can be used for non-real-time as well as real-time service to remote areas. Due to the many handoffs, resource management and connection admission control are important tasks for fair bandwidth sharing and QoS guarantees. Because the total link capacity has to be divided among several carriers and given the limited buffer capacity of the ATM switch, resource management is vital. It ensures the ability of the network to provide users with their negotiated QoS while protecting the network and the end-systems from congestion. We introduced a simple connection admission control (CAC) priority policy based on the delay and cell loss requirements for the investigated types of traffic. We took into account the handoff status of the satellite beams involved. Thus, we propose an onboard buffer architecture with separated buffers for new calls and intra-satellite handoff calls. The priority scheme applied is as follows: highest priority is given to CBR, followed by rt-VBR, nrtVBR and ABR.     

低轨道微小卫星电源系统研究

低轨道微小卫星目前应用广泛,其体积小、质量轻、成本低、应用最新技术等特点使其具有广阔的发展空间。电源系统是卫星的几大核心系统之一,结合目前电源系统特点对低轨道微小卫星电源系统开展研究分析,提出了一种典型的系统拓扑设计方案,并结合工程化应用开展了可靠性、安全性分析。     

ASAR: An ant-based service-aware routing algorithm for multimedia sensor networks

Aimed at three basic services (event-driven, data query and stream query), the paper presents a QoS routing model for multimedia sensor networks. Moreover, based on the traditional ant-based algorithm, we propose an ant-based service-aware routing (ASAR) algorithm. The ASAR chooses suitable paths to meet diverse QoS requirements from different kinds of services, thus maximizing network utilization and improving network performance. Finally, extensive simulation is conducted to verify the effectiveness of our solution and we give a detailed discussion on the effects of different system parameters. Compared to the typical routing algorithm in sensor networks and the traditional ant-based algorithm, our ASAR algorithm has better convergence and significantly provides better QoS for multiple types of services in the multimedia sensor networks. __________ Translated from Acta Electronica Sinica, 2007, 35(4): 705–711 [译自: 电子学报]     

基于多目标多智能体强化学习的低轨卫星切换策略

针对低轨卫星通信系统(LSM) 中地面用户流量需求分布不均衡和用户并发切换过多等挑战,提出了一种基于多目标 多智能体协同深度强化学习的低轨卫星切换策略,以地面小区用户流量需求满意度、切换时延、用户冲突为优化目标,采用多 智能体协同深度学习算法对目标进行优化,其中每个智能体仅负责一个小区用户的卫星切换策略,智能体之间通过共享奖励 实现协作,从而达到多目标优化的效果。仿真结果表明,所提的切换策略的平均用户流量满意度为73.1%,平均切换时延为 343 ms,对比启发式算法能够更好满足地面小区用户的流量需求、平衡卫星网络的负载。     

基于改进VECMP的电力通信网络路由优化算法研究

在电力通信网络中,负载均衡可降低瓶颈节点的过载,提高网络资源的利用率以及系统可靠性.针对电力通信网络路由算法效率较低的问题,文中在传统等价多路径ECMP算法和遗传算法的基础上,结合可变等价多路径算法VECMP与改进的遗传算法IGA用于电力网络中的路由优化.通过优化三种遗传算子,提高了 VECMP算法的效率,并通过算例与...     

低压电力线通信网络特性模型与组网算法

由于低压电力线载波通信网络具有物理拓扑复杂和电力线信道时变的特征,在实际应用中存在着通信可靠性较低的问题。为了提高低压配电网电力线载波通信系统可靠性,在总结前人提高电力线通信可靠性的研究基础上,分析电力线通信网络的拓扑结构和组网模型,并提出组网的优化目标函数;进而提出一种基于信道状态和服务需求的电力线通信组网算法。分析了网络拓扑结构,信道特性和通信误码率、传输延时之间的关系,并提出估算方法。仿真试验结果表明,所提算法可根据信道和通信链路的动态变化以及不同的服务需求而动态地建立并优化电力线通信网络路由,保证通信网络的有效性,为后续的工程应用提供参考。     

无线自组网在变电站综自系统中的应用探讨

剖析了多种变电站自动化系统的通信网络,明确了各自的适用范围,并指出随着电力系统和通信技术的发展,无线通信将在变电站自动化系统中崭露头脚.提出了变电站无线自组网方案,根据变电站具体情况和对目前主流的路由控制和MAC协议的分析,选择了适合变电站自组网的路由算法和MAC协议.     

Contact modeling and prediction-based routing in sparse mobile networks

Mobile ad-hoc networks (MANETs) provide highly robust and self-configuring network capacity required in many critical applications, such as battlefields, disaster relief, and wild life tracking. In this paper, we focus on efficient message forwarding in sparse MANETs, which suffers from frequent and long-duration partitions. Asynchronous contacts become the basic way of communication in such kind of network instead of data links in traditional ad-hoc networks. Current approaches are primarily based on estimation with pure probability calculation. Stochastic forwarding decisions from statistic results can lead to disastrous routing performance when wrong choices are made. This paper introduces a new routing protocol, based on contact modeling and contact prediction, to address the problem. Our contact model focuses on the periodic contact pattern of nodes with actual inter-contact time involved, in order to get an accurate realization of network cooperation and connectivity status. The corresponding contact prediction algorithm makes use of both statistic and time sequence information of contacts and allows choosing the relay that has the earliest contact to the destination, which results in low average latency. Simulation is used to compare the routing performance of our algorithm with three other categories of forwarding algorithm proposed already. The results demonstrate that our scheme is more efficient in both data delivery and energy consumption than previously proposed schemes.     

An efficient method for network topology identification based on an SOM algorithm

In this paper we consider a large number of wireless terminals that are interconnected by a multihop wireless network called an ad hoc network. Design of routing protocols is a crucial problem in ad hoc networks. Location information of wireless terminals is an effective measure for ad hoc network routing. This paper presents a method to identify network topology implying terminal location and connections among terminals. A modified Self‐Organizing Map (SOM) algorithm is proposed to apply to the network topology identification. This method exploits information of the received power levels of the signals that are transmitted by other terminals. This paper has evaluated how network topology is identified by means of an example graph made by random numbers. The results show that only one bit information about the received power level in each terminal can identify network topology accurately with a mean error of about 10% for more terminals than a certain value. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 34–44, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10100     

Application layer multicast routing solution based on genetic algorithms

Application layer multicast routing is a multiobjective optimization problem. Three routing constraints, tree’s cost, tree’s balance and network layer load distribution are analyzed in this paper. The three fitness functions are used to evaluate a multicast tree on the three indexes respectively and one general fitness function is generated. A novel approach based on genetic algorithms is proposed. Numerical simulations show that, compared with geometrical routing rules, the proposed algorithm improve all three indexes, especially on cost and network layer load distribution indexes. __________ Translated from Control and Decision, 2006, 21(4): 381–384 [译自:控制与决策]     

一种用于复杂地理环境的无线智能中继组网技术

分析了现有230 M无线专网及GPRS公网无线信道通信特点,针对重庆市复杂地形条件下普遍存在的通信盲区问题,提出一种基于230 M无线专网的无线智能中继组网技术。该技术采用了230 M无线专网单工微蜂窝组网设计,提出了终端多级中继选择的判据和路由优化算法,在实际应用中融合了高速率调制解调器、时序优化等技术。在地理环境比较复杂的重庆北部地区的应用,取得了验证数据和实际运行效果。     

A distributed routing algorithm for data aggregation in wireless sensor networks

Considering the impact of aggregation cost on the performance of aggregation routes in wireless sensor networks, an aggregation-decision-based distributed routing algorithm for data aggregation is proposed. When source nodes arrive or leave, the algorithm can calculate the aggregation benefit according to data correlation, aggregation cost and transmission cost. Then the algorithm will adaptively make aggregation and routing decisions based on aggregation benefit. Therefore, it can jointly optimize the aggregation and transmission costs and reduce the energy consumption for data gathering. This distributed algorithm makes all the decisions only relying on the local information. Hence, the routing maintenance cost is limited. Simulation results show that the energy consumption difference between this distributed online algorithm and the previous offline one is within 17% under any network conditions. __________ Translated from Journal of Beijing University of Posts and Telecommunications, 2007, 30(1): 9–13 [译自: 北京邮电大学学报]     

基于社会活性和副本限制的DTN路由算法

容忍延迟网络(DTN)为提高消息传输成功率,往往采用多副本策略,导致网络消息泛洪现象,需要对消息副本进行限制。提出了一种基于社会活性和副本限制的DTN路由算法(social activity and copy-limited based DTN routing algorithm,SACRA),该算法基于节点运动历史轨迹和相邻节点特性定义社会活性,根据社会活性和可用缓冲区大小合理分配相遇节点携带消息的份额和交换消息类型,使消息加速扩散,能尽快到达目标节点。仿真结果表明,与典型的多副本DTN路由算法相比,SACRA能够有效降低了消息转发数和负载比率,当时间在1 000 s后成功率在50%以上,从而降低了网络开销,并获得较高的消息递交成功率。     

MANET多路径路由算法综述

相对于单路径路由而言,多路径路由在容错、路由可靠性、QoS路由等方面具有很多优势。因此,为了进一步提高移动自组网MANET的路由质量,多路径路由问题逐渐成为了近年来的一个研究热点。文章对多路径路由和单路径路由的性能进行比较的基础上,分析了多路径路由的基本概念及其分类,介绍了移动Ad hoc网络中多路径路由技术的最新研究进展,并对有关多径路由协议进行了评述。     

基于PRIME标准的低压电力线载波通信组网方案

在阐述低压配电网电力线载波通信网络拓扑和特征的基础上,结合PRIME标准中媒体访问控制(MAC)层的帧结构、类型,深入归纳、分析和总结了PRIME标准中的电力线载波通信组网初始化算法、网络维护与重构算法。通过采用电力线载波芯片ST7590T,应用PRIME标准协议,在某一厂区搭建96节点的现场测试环境,实例分析该组网方案的初始化和网络重构过程,并针对现场可能出现的状况,验证了该组网方案的灵活性、抗毁性和现场可应用性。