应用于Ad Hoc网络中的密度自适应泛洪广播策略

针对Ad Hoc网络中泛洪广播机制可能带来的大量资源浪费问题,本文提出了一种新型的泛洪广播机制——密度自适应的泛洪广播策略.该策略根据发送节点的邻节点密度,以最密集节点的一次发送将覆盖较多节点为出发点,选取尽可能少的邻节点作为转发节点,减少了分组在网络中的重复传输,大大改善了网络的性能.仿真结果表明,密度自适应泛洪广播策略的性能明显优于普通的泛洪广播策略.     

采用方向性天线的ad hoc网络路由协议研究

为了降低方向性天线扫描路由发现的开销和代价,有效利用方向性天线的高空间复用度和高传输能力,提出一种采用方向性天线的ad hoc网络位置信息辅助的按需距离矢量路由协议DLAODV,协议以按需方式获取网络节点的位置信息,结合泛洪、受限泛洪、路由压缩、位置信息修正的贪婪转发策略以及分区桥接策略,充分利用方向性天线优势,有效提高路由发现效率,路由区分维护策略有效降低了路由维护开销.仿真结果显示,DLAODV能够使得网络获得高吞吐率、低时延和开销性能,相比采用全向天线的AODV协议性能获得了明显提升.     

光网络中基于路径计算单元的路由机制研究

针对大规模多层多域光网络群故障发生时的网络受损情况,提出基于路径计算单元(PCE)架构的跨域路由算法进行快速恢复,并基于OMNet平台对多层多域路由方案进行了性能仿真分析。结果表明,基于PCE架构的路由策略在群故障发生时能够大大减少网络中的路径计算请求泛洪信息,降低路由计算收敛时间,可以提高全网剩余资源的资源利用率,为业务的快速恢复提供了路由基础。     

基于OPNET的改进式泛洪路由仿真

本文概要介绍了改进式泛洪路由和网络仿真工具OPNET。详细讨论了如何利用OPNET工具建立改进式泛洪路由仿真模型的过程,并构建了一个基于WCDMA网络的改进式泛洪路由仿真平台。在此基础上,对改进式泛洪路由的功能和性能进行了分析和验证。     

无线传感器网络中一种高能效低延时的泛洪算法研究

提出了一种新的应用于无线传感器网络的泛洪传播算法——覆盖优先泛洪算法。算法采用覆盖优先策略为相邻节点分配不同的转发优先权，实现泛洪包快速覆盖整个网络；采用节点转发抑制策略和动态延时转发机制，尽可能抑制冗余包和减少冲突重传。仿真结果表明，该算法与同类算法相比，具有更高的能源有效性，更低的延时。     

Ad hoc网络基于信息的调度算法

针对Ad hoc网络提出一种基于信息的调度策略。分组调度时,既考虑队列中剩余信息的多少又考虑原始的信息长度。仿真结果表明,算法改进了整个系统信息端到端的时延性能,并且不影响网络的吞吐量性能,不需要额外的通信开销。     

一种位置信息辅助的Ad Hoc网络按需距离矢量路由协议

 针对Ad Hoc网络中按需距离矢量路由协议路由开销大,以及位置路由中位置信息在获取方式上存在的缺点,提出一种位置信息辅助的按需距离矢量路由协议(LAODV),协议结合AODV以按需的方式获取网络节点的位置信息,并以泛洪、位置信息修正的贪婪转发和局部受限泛洪相结合方式进行路由发现,同时提出了路由维护策略和局部多径备份路由策略。仿真结果表明,LAODV能够获得较好的分组递交率、时延和路由开销性能。     

Ad Hoc移动骨干网分层路由协议的研究

为了解决Ad Hoc网络的可扩充性问题,分级结构在Ad Hoc网络中的应用得到了广泛的研究.文中提出了一种适用于移动Ad Hoc网络中的多频分级结构--移动骨干网的分层路由协议Layered-AODV.该协议结合了网络多频分级的结构特点在各级采用不同的按需路由策略以降低全网冗余路由信息的传播,提高了网络的可扩展性.仿真结果表明,该协议能够有效减少移动Ad Hoc网络中的路由开销,端到端传播时延,并能有效地提高网络业务的性能,在一定程度上能够解决随着Ad Hoc网络规模扩大而网络性能下降的问题.     

基于OPNET的混合关键性网络建模与仿真分析

混合关键性网络是一种新型的通信架构,可以满足非实时性和实时性业务的需求.为分析其网络性能,提出在OPNET网络仿真环境中建模的方法.以开放式系统互联模型为基础,采用层次化建模,构建网络的节点模型和进程模型.该模型考虑了事件触发和时间触发消息的特点,通过设计调度算法和容错方式,实现了仿真实验的灵活配置和端到端延迟抖动等性能指标的验证.对仿真结果的性能分析表明,混合关键性网络能够保证实时业务的确定性以及兼容标准以太网的非实时业务.     

有线网络综合网管监控调度中心的建设

苏州有线“综合网管监控及调度中心”项目实现A/B平台相融合、全程全网可管可控、支持故障动态感知的端到端业务和网络管理调度系统,系统实现全网全覆盖的可视化基础网络资源管理链和运维知识管理体系,大幅度加强了苏州网络的监管能力和运维效率.     

一种改进的基于新一代Gnutella网络的动态搜索算法

新一代的Gnutella网络采用了一种双层拓扑结构,使得P2P节点之间的连接更为稠密。使用早期的洪泛搜索算法在查找频繁资源时会造成网络中查询消息包的不必要的泛滥。动态搜索算法是一种新提出的改进的算法,但搜索所花费的时间较长。针对动态搜索算法的高延时性提出了一种改进的基于贪心策略和分数制TTL的动态搜索算法。实验表明,该算法具有较好的搜索效率。     

车联网网络架构与媒质接入机制研究

车联网旨在实现一体化智能交通体系和无处不在的网络,其关键技术在于全网数据共享和车辆宽带接入。现有车辆网络架构因其不同设计目标而缺少统一的协议栈和数据接口,难以有效进行全网数据共享或协同通信;其多信道机制缺少灵活性,整体网络性能受网络节点密度影响较大。文章提出面向安全应用的车联网无线网络架构及其协同通信协议栈,并对车联网自适应多信道媒质接入协议进行研究。     

Mini‐Slot‐Based Transmission Scheme for Local Customer Internetworking in PONs

We propose a new mini‐slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN‐PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini‐slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN‐PON with a mini‐slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.     

Scheduling Combined Unicast and Multicast Traffic in Broadcast WDM Networks

This paper studies the performance of various strategies for scheduling a combined load of unicast and multicast traffic in a broadcast WDM network. The performance measure of interest is schedule length, which directly affects both aggregate network throughput and average packet delay. Three different scheduling strategies are presented, namely: separate scheduling of unicast and multicast traffic, treating multicast traffic as a number of unicast messages, and treating unicast traffic as multicasts of size one. A lower bound on the schedule length for each strategy is first obtained. Subsequently, the strategies are compared against each other using extensive simulation experiments in order to establish the regions of operation, in terms of a number of relevant system parameters, for which each strategy performs best. Our main conclusions are as follows. Multicast traffic can be treated as unicast traffic, by replicating all multicast packets, under very limited circumstances. On the other hand, treating unicast traffic as a special case of multicast traffic with a group of size 1, produces short schedules in most cases. Alternatively, scheduling and transmitting each traffic component separately is also a good choice.     

Performance Analysis of Adjusted Probabilistic Broadcasting in Mobile Ad Hoc Networks

Broadcasting in Mobile Ad Hoc Networks (MANETs) is a fundamental data dissemination mechanism with a number of important applications in, e.g., route discovery, address resolution. However, broadcasting induces what is known as the “broadcast storm problem” which causes severe degradation in network performance due to excessive redundant retransmission, collision, and contention. Broadcasting in MANETs has traditionally been based on flooding, which simply swamps the network with large number of rebroadcast messages in order to reach all network nodes. Although probabilistic flooding has been one of the earliest suggested schemes to broadcasting, there has not been so far any attempt to analyse its performance behaviour in a MANET environment. In an effort to fill this gap, this paper investigates using extensive ns-2 simulations the effects of a number of important system parameters in a typical MANET, including node speed, pause time, traffic load, and node density on the performance of probabilistic flooding. The results reveal that most of these parameters have a critical impact on the reachability and the number of saved rebroadcast messages achieved by probabilistic flooding.     

Game theoretic approach in routing protocol for wireless ad hoc networks

This paper introduces a game theoretic method, called forwarding dilemma game (FDG), which controls routing overhead in dense multi-hop wireless ad hoc networks. The players of the game are the wireless nodes with set of strategies {Forward, Not forward}. The game is played whenever an arbitrary node in the network receives a flooding packet. In FDG, every player needs to know the number of players of the game. That is why a neighbor discovery protocol (NDP) is introduced. In order for NDP to function, a field is attached to the flooding packets (routing overhead packets). The mixed strategy Nash equilibrium is used as a solution for the FDG. This provides the probability that the flooding packet would be forwarded by the receiver node. FDG with NDP is implemented in AODV protocol in Network Simulator NS-2 to verify its performance with simulations. FDG with NDP improves performance of the AODV compared to the same network with only AODV protocol in moderate and high node densities. FDG can be applied to any routing protocol that uses flooding in the route discovery phase.     

Security upgrade against RREQ flooding attack by using balance index on vehicular ad hoc network

VANET is an ad hoc network that formed between vehicles. Security in VANET plays vital role. AODV routing protocol is a reactive or on-demand routing protocol which means if there is data to be send then the path will create. AODV is the most commonly used topology based routing protocol for VANET. Using of broadcast packets in the AODV route discovery phase caused it is extremely vulnerable against DOS and DDOS flooding attacks. Flooding attack is type of a denial of service attack that causes loss of network bandwidth and imposes high overhead to the network. The method proposed in this paper called Balanced AODV (B-AODV) because it expects all network node behave normally. If network nodes are out of the normal behavior (too much route request) then they identified as malicious node. B-AODV is designed with following feature: (1) The use of adaptive threshold according to network conditions and nodes behavior (balance index) (2) Not using additional routing packets to detect malicious nodes (3) Perform detection and prevention operations independently on each node (4) Perform detection and prevention operations in real time (5) No need for promiscuous mode. This method for detection and prevention flooding attack uses average and standard deviation. In this method each node is employing balance index for acceptation or rejection RREQ packets. The results of the simulation in NS2 indicates B-AODV is resilience against flooding attack and prevent loss of network bandwidth. Comparing between AODV with B-AODV in normal state (non-attacker) shows B-AODV is exactly match with AODV in network performance, this means that the B-AODV algorithm does not impose any overhead and false positive to AODV.     

Performance evaluation of broadcasting strategies in cognitive radio networks

Broadcasting is an important phenomenon, because it serves as simplest mode of communication in a network, via which each node disseminates information to their neighboring nodes simultaneously. Broadcasting is widely used in various kind of networks, such as wireless sensor networks, wireless networks, and ad-hoc networks. Similarly, in cognitive radio networks (CRNs), broadcasting is also used to perform many tasks including neighbor discovery, spectrum mobility, spectrum sharing, and dissemination of message throughout the network. The traditional approach that has been used as broadcasting in CRNs is simple flooding in which a message is disseminated in the network without any strategy check. Simple flooding can cause major setbacks in the network, such as excessive redundant rebroadcasts, and collision drops which collectively are termed as broadcast storm problem. To reduce the effects of broadcast storm problem in wireless networks, we propose and compare four broadcasting strategies for cognitive radio networks in this paper. These four strategies are: (1) probability based, (2) counter based, (3) distance based, and (4) area based. Extensive NS-2 based simulations are carried out on different threshold values for each broadcasting strategy. After experimental evaluation, it is demonstrated that counter based broadcasting surpasses other broadcasting strategies by achieving maximum delivery ratio of 60% and by decreasing redundant rebroadcasts and collision drops up to 44 and 37% respectively.

     

Flooding Strategy for Target Discovery in Wireless Networks

In this paper, we address a fundamental problem concerning the best flooding strategy to minimize cost and latency for target discovery in wireless networks. Should we flood the network only once to search for the target, or should we apply a so-called “expansion ring” mechanism to reduce the cost? If the “expansion ring” mechanism is better in terms of the average cost, how many rings should there be and what should be the radius of each ring? We separate wireless networks based on network scale and explore these questions. We prove that two-ring and three-ring schemes can reduce the cost of flooding compared to a single attempt, and we provide a general formula to determine good parameters for the two-ring and three-ring hop-based flooding schemes. Through simulations, we show that choosing flooding parameters according to our techniques gives performance close to that of ideal flooding schemes. Afterwards, we extend our work from the single target discovery problem to the multi-target discovery problem. We show that a properly chosen searching radius can save much more searching cost than a simple radius selection scheme for multi-target discovery problems.     

基于攻击策略的复杂网络拓扑结构优化模型

针对不考虑攻击策略时以自然连通度作为复杂网络抗毁性测度存在的缺陷,用节点的改进总连通度作为目标函数建立了基于按度攻击策略的复杂网络拓扑结构优化模型,并运用收敛速度较快的自适应局部增强微分进化算法(ADMPDE)对复杂网络的拓扑结构优化进行仿真分析。仿真结果验证了该模型的合理性和算法的适用性,优化后的复杂网络的度大节点比例提高了32%,其抗毁性得到明显改进,并得到一些有意义的结论。相关内容可为该领域的进一步研究提供有价值的参考。