Tier_Flat:P2P网络并行模拟器(HiFiP2P)的一种路由算法

为了给P2P网络并行模拟器HiFiP2P提供正确高效的路由,使其能够高效地执行大规模P2P网络并行模拟,基于互联网中的层次路由模型和Flat本地静态路由计算和查找算法,采取边界路由最小化的并行网络拓扑划分机制,设计了Tier_Flat路由算法,用以实现HiFiP2P的远程和本地静态路由,它以最低O((N~4)~(1/3))的空间开销,取得了O(1)的查找效率。结果表明,Tier_Flat路由算法路由计算时间短,路由表内存占用小,路由查询速度快,为HiFiP2P平台的大规模P2P网络并行模拟提供了高效的路由服务。     

自组网中一种基于跨层负载感知的蚁群优化路由协议

将蚁群优化和跨层优化方法结合起来,提出了一种基于跨层负载感知和蚁群优化的路由协议(CLAOR)。协议将整个路径中各节点MAC层的总平均估计时延和节点队列缓存的占用情况结合起来,共同作为路由选择和路由调整的重要度量标准进行按需路由发现和维护,通过拥塞节点丢弃蚂蚁分组以及借助部分兼具蚂蚁功能的数据分组实现正常路由表的维护等方法,减少了控制开销,增加了算法的可扩展性,较好地解决了自组网中现有基于蚁群优化的路由协议中普遍存在的拥塞问题、捷径问题和引入的路由开销问题。仿真结果表明,CLAOR在分组成功递交率、路由开销以及端到端平均时延等方面具有优良性能,能很好地实现网络中的业务流负载均衡。     

基于路径到达率和动态广播时延的汇聚树协议

汇聚树路由协议(CTP)是目前无线传感器网络(WSN)中常用的数据采集路由协议。它是基于期望传输次数(ETX)的树型路由协议。但对多跳路径的衡量,简单的ETX相加往往无法良好刻画实际路径质量,致使该协议很难选出最优路径。本文提出了基于端到端的数据到达率(PDR)的CTP改进协议,能更好地衡量多跳路径的网络质量。据此选出的最优路径能构建更优的汇聚树,提高端到端数据传递的成功率,减少平均传递次数和平均传递时间,这样可以节省能耗,提高网络生存时间。同时,本文提出在建树过程中采取动态时延广播策略,可以有效减少建路由树时的广播次数,节省开销。     

间断连通移动有组织网络中延时有界的概率路由策略

针对间断连通移动自组织网络(ICMAN)实际应用中对消息的送达率、发送延时及开销三项重要指标的要求,本文借助于发送延时的概率模型,分析了这三项指标的相互关系,进而提出了一种综合考虑这三种指标的延时有界的概率路由策略(BDPBR),其特点是重视精确的延时指标,而非现有算法关注的消息的平均传输延时,能以给定概率保证消息的端到端发送延时.仿真结果表明,该策略能够通过调整必需发送概率(RDP)和必需传输延时(RDD)来控制消息的实际发送率和发送延时,同时可根据RDP和RDD来调整系统开销,可按用户设定的送达率与延时指标以相应的代价发送消息,适应不同的服务要求.     

基于消息调度和喷射等待的车载容迟网络路由算法

车载容迟网络具有间歇性、快速移动的特点,其拓扑结构复杂.车载容迟网络路由协议中,消息在节点间如何有序高效地传输是一个重要问题.根据节点间的传递方式和传递依据,提出了一种基于消息调度和喷射等待的车载容迟网络路由算法MSSW(Vehicle Delay-tolerant Network Routing Algorithm Based on Message Schedule and Spray Wait):采用增量平均的方法,改进投递预测概率的相遇更新公式;采用增强型的方法,改进投递预测概率的衰减更新公式;采用消息调度为动态阈值区分的跳数优先级排序和开销优先级排序机制;传递方式为基于副本控制的喷射和等待两个阶段,喷射阶段采用二叉树的方式传递,以实现多路径转发,等待阶段采用直接传输路由的方式传递;同时加入ACK确认机制.仿真结果表明,本算法能提高投递率,降低网络开销,有效地控制平均时延.     

低时延能耗均衡的水声传感器网络簇间路由算法

针对水声传感器网络的簇间路由选择问题,提出了一种基于前向网关的低时延能耗均衡路由算法,该算法采用最优方向角原则和能耗均衡原则选择中继簇头和中继网关,以减小长延迟和高能耗对水声通信的影响。仿真结果表明该算法在网络平均能耗、端到端时延和网络生命周期等方面具有较好的性能。     

基于链路动态特征的自组网路由选择方法

针对在动态的移动ad hoc网络环境中失效路由的频繁重建和维护操作造成大量控制负载开销以及能量消耗的问题,提出了一种基于无线逻辑链路信息熵度量的路由稳定性计算方法.此算法通过网络运行过程中无线链路状态变化所表现出的不确定性特征来刻画网络节点的稳定程度,并在路由建立过程中选择相对稳定的无线移动节点作为数据传输的参与节点....     

一种基于HLA/RTI的卫星组网仿真系统

设计了一种基于HLA/RTI的卫星组网仿真系统,在该系统中卫星节点、星间链路、卫星轨道和通信节点路由被划分为功能独立的联邦成员.这种结构具有良好的可扩展性,可适用于不同的卫星星座结构,同时可以适应不同的路由策略和各类空间通信链路模型.最后通过统计卫星组网网管报文响应时间验证了该仿真系统的可行性.卫星组网仿真系统为卫星组网的其他研究提供了仿真验证平台.     

自组网中一种可靠的层次路由协议

针对自组网中基于多层有中心分级结构(MCHS)的分级状态路由(HSR)协议存在结构稳定性差、结构维护开销大、可靠性不高和丢包问题严重等问题,提出一种可靠的层次路由协议(RHRP)。它基于一种新的多层无中心分级结构(MCLHS),该结构采用无中心策略,有利于提高结构稳定性和降低结构维护开销,并能进一步提高可靠性和降低路由开销。RHRP采用"高层虚拟链路以群为构成元素"的策略,使高层虚拟链路更稳定,有利于提高可靠性。更稳定的结构和高层虚拟链路可以减少丢包数目和重路由次数,从而降低传输时延和路由开销。通过分析路由可靠度,从理论上证明了RHRP的可靠性较高。通过仿真评价RHRP和HSR的性能,结果表明,RHRP在投递率、平均端到端时延和路由开销等指标上都优于HSR。     

一种改进的同构网络虚拟骨干形成算法与时钟同步应用

基于连通支配集构造无线传感器网络虚拟骨干,可以简化路由操作,并可提高广播效率。对Stojmenovic等学者提出的连通支配集分布式构造算法进行改进,大幅度降低了支配集尺寸和计算复杂度,并将之应用于DTMS时钟同步算法中,降低广播开销达60%以上。     

Dynamic Resource Pricing and Allocation in Multilayer Satellite Network

The goal of delivering high-quality service has spurred research of 6G satellite communication networks. The limited resource-allocation problem has been addressed by next-generation satellite communication networks, especially multilayer networks with multiple low-Earth-orbit (LEO) and non-low-Earth-orbit (NLEO) satellites. In this study, the resource-allocation problem of a multilayer satellite network consisting of one NLEO and multiple LEO satellites is solved. The NLEO satellite is the authorized user of spectrum resources and the LEO satellites are unauthorized users. The resource allocation and dynamic pricing problems are combined, and a dynamic game-based resource pricing and allocation model is proposed to maximize the market advantage of LEO satellites and reduce interference between LEO and NLEO satellites. In the proposed model, the resource price is formulated as the dynamic state of the LEO satellites, using the resource allocation strategy as the control variable. Based on the proposed dynamic game model, an open-loop Nash equilibrium is analyzed, and an algorithm is proposed for the resource pricing and allocation problem. Numerical simulations validate the model and algorithm.     

A Safe and Reliable Routing Mechanism of LEO Satellite Based on SDN

Satellite networks have high requirements for security and data processing speed. In order to improve the reliability of the network, software-defined network (SDN) technology is introduced and a central controller is set in the network. Due to the characteristics of global perspective, control data separation, and centralized control of SDN, the idea of SDN is introduced to the design of the satellite network model. As a result, satellite nodes are only responsible for data transmission, while the maintenance of the links and the calculation of routes are implemented by the controller. For the massive LEO satellite network based on SDN, a state evaluation decision routing mechanism is proposed. The designed mechanism monitors the status of the entire network effectively and reduces the on-board load on the satellite network. The best routing decision is made under the comprehensive consideration of the current and historical status of each intersatellite link between Low Earth Orbit (LEO) satellite network nodes. The calculation and storage requirements are controlled within a reasonable range. Based on the curve parameter transmission fuzzy encryption algorithm, a safe and reliable condition assessment decision routing mechanism (CADRM) is designed. It ensures that the personal information of the LEO satellite network can be transmitted safely and effectively. The experimental simulation results show the improvement of network throughput, the reduction of packet loss rate and the enhancing of network reliability.     

低轨卫星移动通信系统移动性管理策略研究

低轨卫星移动通信系统是当前通信领域研究的一个热点，它的移动性管理策略对整个系统的性能有着至关重要的作用，本文从位置管理和切换管理两个方面介绍了目前国内外较为先进的策略，并且重点介绍了目前处理低轨卫星通信系统独有的多星覆盖问题效果最好的仰角和覆盖时间加权策略和把切换和路由有机结合的最小跳数切换策略，它们都很大的提高了系统的性能。     

改进的蚁群算法及其在卫星网络路由计算中的应用

介绍了蚁群算法的原理，然后对现有蚁群算法进行了一些改进，使它能够快速地收敛以满足高速变化的卫星网络拓扑结构．采用改进的虚拟拓扑策略解决了卫星网络拓扑高速变换的问题．将改进的蚁群算法应用于其上，并给出了相应的性能评估．所提出的改进的虚拟拓扑策略，能够大大减少一个系统周期内卫星网的时间片个数．应用于此基础上的改进的蚁群算法也体现了较好的性能．     

Prophet_TD Routing Algorithm Based on Historical Throughput and Encounter Duration

Opportunistic networks are self-organizing networks that do not require a complete path between the source node and the destination node as it uses encounter opportunities brought by nodes movement to achieve network communication. Opportunistic networks routing algorithms are numerous and can be roughly divided into four categories based on different forwarding strategies. The Prophet routing algorithm is an important routing algorithm in opportunistic networks. It forwards messages based on the encounter probability between nodes, and has good innovation significance and optimization potential. However, the Prophet routing algorithm does not consider the impact of the historical throughput of the node on message transmission, nor does it consider the impact of the encounter duration between nodes on message transmission. Therefore, to improve the transmission efficiency of opportunistic networks, this paper based on the Prophet routing algorithm, fuses the impact of the historical throughput of the node and the encounter duration between nodes on message transmission at the same time, and proposes the Prophet_TD routing algorithm based on the historical throughput and the encounter duration. This paper uses the Opportunistic Networks Environment v1.6.0 (the ONE v1.6.0) as the simulation platform, controls the change of running time and the number of nodes respectively, conducts simulation experiments on the Prophet_TD routing algorithm. The simulation results show that compared to the traditional Prophet routing algorithm, on the whole, the Prophet_TD routing algorithm has a higher message delivery rate and a lower network overhead rate, and its average latency is also lower when node density is large.     

Efficient Routing Protection Algorithm in Large-Scale Networks

With an increasing urgent demand for fast recovery routing mechanisms in large-scale networks, minimizing network disruption caused by network failure has become critical. However, a large number of relevant studies have shown that network failures occur on the Internet inevitably and frequently. The current routing protocols deployed on the Internet adopt the reconvergence mechanism to cope with network failures. During the reconvergence process, the packets may be lost because of inconsistent routing information, which reduces the network’s availability greatly and affects the Internet service provider’s (ISP’s) service quality and reputation seriously. Therefore, improving network availability has become an urgent problem. As such, the Internet Engineering Task Force suggests the use of downstream path criterion (DC) to address all single-link failure scenarios. However, existing methods for implementing DC schemes are time consuming, require a large amount of router CPU resources, and may deteriorate router capability. Thus, the computation overhead introduced by existing DC schemes is significant, especially in large-scale networks. Therefore, this study proposes an efficient intra-domain routing protection algorithm (ERPA) in large-scale networks. Theoretical analysis indicates that the time complexity of ERPA is less than that of constructing a shortest path tree. Experimental results show that ERPA can reduce the computation overhead significantly compared with the existing algorithms while offering the same network availability as DC.     

多波长光网络的动态路由等效算法

针对多波长光网络的特点，提出了一种动态路由和波长分配的等效算法。采用波长图、增加虚拟源节点和目的节点等技术，把多波长网络转化为等效的单波长网络，避免了求解路由和波长分配两个复杂子问题，简化了算法的程序设计。利用最短径算法进行路由和波长分配可以求得问题的最优解，从而有效地降低了网络阻塞率。仿真结果表明：与FAR-2D算法相比，在4和8波长的全波长转换网络中，采用等效算法阻塞率最大降幅分别达到0．02、0．025。     

卫星图像码率控制方法的改进

JPEG2000存在大量计算冗余和消耗较大内存资源的缺陷.为了适应实时性要求高和资源有限的卫星图像的传输,提出一种新的基于率失真斜率的卫星图像码率控制算法.本方法是根据编码块的有效位平面数大致呈下降趋势和率失真斜率的三个属性提出一个简单的公式,通过此公式求得的率失真斜率作为层1编码的门限值,丢掉小于此门限值的编码通道,然后在该值基础上层2计算最优率失真斜率和截断点以实现码率控制,因而不需要编码所有的编码通道.实验结果表明,在0.125 bpp 时,本算法的存储量约占 PCRD 存储量的33%,而信噪比保持不变.因此,本方法可以有效地提高卫星图像的编码效率.     

基于GDOP的最优定位星座性能研究

利用ＧＤＯＰ定义,提出了最优定位星座的问题。为选择合适的星座,基于ｍ序列设计了组合计数法,并针对四星,五星以及所有可见星定位算法分别计算了ＧＤＯＰ。对不同定位星数的ＧＤＯＰ变化规律进行了分析、总结和归纳,最后给出了结论。     

SIMULATED ANNEALING AND GENETIC ALGORITHM APPROACHES FOR DISCONTINUOUS COVERAGE SATELLITE CONSTELLATION DESIGN

Constellations of Earth orbiting satellites are used to perform many tasks. If the constellation's coverage need not be continuous in time, the number of satellites and, therefore, the cost of the constellation may be decreased. Finding constellations that minimize revisit times for discontinuous coverage is posed as an optimization problem. Practical limits on coverage analysis provide objective functions that are not differentiable, so non-gradient-based optimization methods are necessary. Simulated annealing and a genetic algorithm were applied to discontinuous coverage problems for various numbers of satellites and Earth central angles, providing both whole Earth and zonal coverage. Results are presented and compared to constellation designs from a traditional approach. Simulated annealing appears to provide answers with less computational effort, but the genetic algorithm is capable of simultaneously generating different de signs with the same revisit times. Additional conclusions about these approaches for discontinuous coverage satellite constellation design are made.