一种改进的井下无线传感器网络广播算法

针对现有的井下无线传感器网络广播算法能耗较高的问题,提出了一种改进的无线传感器网络前向广播算法。该算法中,转发节点可根据自身位置,选择优先节点转发信息,大大减少了无线传感器网络中需要转发的冗余信息量,从而降低了网络能耗。仿真结果表明,该算法在网络节点密度达到一定值时,满足网络接收率要求,且能够限制转发的信息总量,有效降低了无线传感器网络能耗。     

Ad hoc网络中的一种动态均匀区域广播算法

Ad Hoc网络是一种无固定通信设备支持、节点可自由移动的多跳全分布式无线网络。动态均匀区域广播算法是在概率算法和计数器算法的基础上,通过邻居节点与转发节点发送范围边界上均匀分布点的位置关系,以及网络中节点的分布密度动态地调整转发概率。文中给出了NS-2下的仿真结果。模拟实验表明,本算法在节省转发率和可达率两个性能指标上均优于概率算法和计数器算法。     

一种基于AdHoc的城市车联网广播算法

针对城市场景下道路的复杂性,提出了一种基于节点相对距离与消息类型的广播算法（The Broadcasting Algorithm based on Relatively Distance and Message Type, RDMT-BA）。该算法应用节点的相对移动速度和消息类型决定接听广播的节点,再依据转发闪值和等待时间决定对广播进行转发的节点,进而提高转发的投递率和降低信道中的广播冲突。通过改变节点的数目和速度,文章同时分析了转发参数对覆盖率、转发节省数和延迟等性能的影响,并与洪泛算法进行比较表明,该算法在性能上更加有利于城市交通的管理和改善。     

基于传输范围覆盖的无线传感器网络广播算法

广播在无线传感器网络中具有广泛的应用.泛洪广播虽然简单,但极为耗能.基于概率、基于计数以及基于位置等广播算法不使用任何邻节点信息,简单但性能改善有限.MPR以及多数基于连通支配集的广播算法利用2-hop邻节点信息计算转发节点集,虽然获得了较好的性能,但需更多的通信开销以获取和维护2-hop邻节点信息.为减少转发节点并节约通信开销,较好的实现无线传感器网络广播,本文利用1-hop邻节点信息提出了一种基于传输范围覆盖的广播算法TRCB.算法的主要思想是如果发送节点U的1-hop邻节点V被U和不包括节点V的其余1-hop邻节点集S覆盖,则节点V将不参与转发.分析与仿真表明,TRCB有效减少了冗余转发节点,从而节约了无线传感器网络能耗;并且利用1-hop邻节点信息,具有通信开销小、适应网络拓扑变化的特点;且其性能优于同样利用1-hop邻节点信息的边缘转发算法EFB.     

基于中继节点的多跳CR Ad Hoc网络广播算法

针对避免广播冲突的CR Ad Hoc网络的分布式广播协议广播成功率低和基于选择性广播信道集的低延迟广播算法广播冲突率高的问题，提出基于中继节点选择的多跳CR Ad Hoc网络广播算法。根据节点可用信道集的大小和基于邻居度的转发概率选取中继节点，并对相应中继节点的可用信道集随机左移，在保证一定广播成功率、广播时延和广播冲突率的前提下，降低节点转发率，减少网络中的冗余信息；建立综合评价函数对广播算法的综合性能进行了定量分析；给出广播冲突概率推导。仿真结果表明，该算法与分布式广播协议相比，提高了广播成功率，降低了广播时延；与低延迟广播算法相比，降低了节点转发率和广播冲突概率。根据综合评价函数，该广播算法的综合性能更好。     

基于主从支配点的无线自组网络广播算法及优化

文中提出了一种分布式主从支配点广播算法，节点利用局部拓扑结构选择支配点并对其进行主从划分，只有主支配点才对广播报文进行转发，从支配点负责监测网络的覆盖情况，当发现有未被覆盖的邻居节点时它就自动转化为主支配点，这样不仅降低了转播节点的数目，而且能够保证对网络的完全覆盖．在此基础上文中又提出了自剪枝规则对广播算法进行优化，自剪枝规则不会影响网络的完全覆盖性，并且能够进一步消除冗余转播节点，提高广播算法的性能．文章对算法的的正确性和有效性进行了理论分析，并通过仿真对它们的性能进行了验证和对比，结果表明它们优于其它广播算法．     

移动传感网中基于密度和距离的概率广播算法

广播是移动传感器网络(mobile wireless sensor networks)中最基本的信息传播方式,但现有的广播算法在广播时需要大量中间转发节点,造成大量消息冗余转发,从而导致能量浪费.因此提出一种基于节点密度和距离的概率(broadcasting algorithm named node density and distance-based probability, NDDP)广播算法.该算法平均转发率为5S/(Nπr2),这里S为网络区域面积,N为网络节点总数,r为通信半径.理论分析得出该算法的平均广播接收率超过95%.ns-2模拟结果表明平均广播接收率达到92%以上,并且网络节点密度越大算法的转发率越低,越节能.模拟实验结果表明NDDP算法无论在稳定性方面还是在节能性方面均优于Smite和Sidewinder中的广播算法.     

ZigBee网络节点选择性优化广播算法

针对ZigBee协议网络层广播算法产生广播暴和网络运行效率低的问题,根据ZigBee技术特点提出一种节点选择性优化广播算法。该算法利用部分节点的一跳和两跳邻居信息、节点接收信号强度信息、节点间父子关系等,将网络节点分成不同类型的工作节点,节点在进行广播时根据自身的工作类型处理广播帧。理论分析表明该算法能够完全覆盖网络。仿真结果表明,在相同条件下,与其他适用于ZigBee网络的广播算法相比,该算法的节点转播率低,节点平均开销小。节点选择性优化广播算法有助于提高ZigBee网络的运行效率,降低能耗,延长网络使用寿命。     

移动自组织网络中一种基于多点中继策略的优化泛洪广播算法

多点中继(multipoint relaying,MPR)是一种有效的移动ad hoc网络即时泛洪广播策略.选择尽量少的邻节点以覆盖2跳(2-hop)范围内所有节点是MPR策略的关键.然而现有的基于MPR策略的泛洪算法忽视了转发节点之间所存在的共有邻接关系对结果的影响.在分析转发节点之间连接拓扑关系的基础上,发现尚未被覆盖的2跳节点集合的势(cardinality)可以进一步压缩,从而进一步减少冗余的转发节点.同时,讨论了利用自裁减(self-pruning)提升MPR性能的可能性.据此提出了基于共有邻接关系消除的自裁减辅助MPR优化泛洪广播算法(ECARSP).理论分析和实验结果表明,ECARSP在转发节点数量和网络负载等方面均要优于现有的移动ad hoc网络MPR泛洪算法.     

无线传感器网络中 d-BIP 算法的改进

无线传感器网络的广播问题中,能量有效是其重要目标和首要难题.如果对广播算法进行优化就可以极大地节省节点能量、提高传输效率.所以在 d-BIP 算法的基础上,通过改进自适应定向天线模型调整波束宽度的方式,提出了性能更加优越的 c-d-BIP 算法.在建立支撑树时,每加入一个新节点,首先判断是否符合以增大波束宽度的方式来传输消息给新节点的条件,如果符合则以增大波束宽度的方式来传输消息,否则重新建立一个波束来传输.仿真结果表明 c-d-BIP 能有效地节约能量,特别在网络节点密度较大时性能更加优越.     

Performance improvements for network-wide broadcast with instantaneous network information

We study the performance of network-wide broadcasting as a function of the information implicitly available at nodes from neighbourhood transmissions. We term this set of instantaneous information as network information. Our discussion is focused on stateless broadcasting algorithms in which nodes decide on their forwarding behaviour based on the available network information. While stateless broadcasting schemes in the existing literature use various design guidelines that take advantage of specific aspects of the information, we develop a unified analytical model by characterizing the information available during different stages of broadcasting. Thus, our results are applicable to all stateless algorithms. We analyze broadcasting performance in terms of the transmission probability and redundancy of transmissions. Subsequently, we use our results to obtain insights on the feasibility conditions governing algorithm design depending on the network density and costs. While the first part of the work considers ideal channel conditions modeled as a unit disk graph (UDG), we subsequently enhance the model using a quasi-unit disk graph model (QUDG) to understand the effect of dynamic channel conditions.     

An adaptive algorithm for resolving processor thrashing in load distribution

Processor thrashing in load distribution refers to the situation when a number of nodes try to negotiate with the same target node simultaneously. The performance of dynamic load-balancing algorithms can be degraded because processor thrashing can lead to receiver node overdrafting, thus causing congestion at a receiver node and reduction of workload distribution. In the paper we present an adaptive algorithm for resolving processor thrashing in load distribution. The algorithm is based on the integration of three components: (1) a batch task assignment policy, which allows a number of tasks to be transferred as a single batch from a sender to a receiver; (2) a negotiation protocol to obtain mutual agreement between a sender and a receiver on the batch size; and (3) an adaptive symmetrically-initiated location policy to select a potential transfer partner. Simulations reveal that our algorithm provides a significant performance improvement at high system loads because the algorithm can avoid processor thrashing so that CPU capacity is more fully utilized.     

A new dynamic counter-based broadcasting scheme for Mobile Ad hoc Networks

Broadcasting is an essential operation in Mobile Ad hoc Networks (MANETs) to transmit a message (data packet) from the sender to the rest of the network nodes. Although flooding is the simplest mechanism for broadcasting, where each node retransmits every uniquely received message exactly once, it is usually costly and results in serious redundancy, contention and collisions in the network. These problems are widely referred to as the broadcast storm problem. In the light of this, this study introduces a new counter-based broadcasting scheme to achieve efficient broadcasting in MANETs. This is achieved by using a counter-based scheme with a dynamic threshold to increase the successful delivery rate of packets and enhance the throughput of the network. Extensive simulation experiments have been conducted. Our results show that the new scheme outperforms the well known exiting schemes, namely the two counter-based broadcasting scheme and blind flooding.     

On communication models for algorithm design in networked sensor systems: A case study

Towards building a systematic methodology of algorithm design for applications of networked sensor systems, we formally define two link-wise communication models, the Collision Free Model (CFM) and the Collision Aware Model (CAM). While CFM provides ease of programming and analysis for high level application functionality, CAM enables more accurate performance analysis and hence more efficient algorithms through cross-layer optimization, at the expense of increased programming and analysis complexity. These communication models are part of an abstract network model, above which algorithm design and performance optimization is performed. We use the example of optimizing a probability based broadcasting scheme under CAM to illustrate algorithm optimization based on the defined models. Specifically, we present an analytical framework that facilitates an accurate modeling and analysis for the probability based broadcasting in CAM (PB_CAM). Our analytical results indicate that (1) the optimal broadcast probability for either maximizing the reachability within a given latency constraint or minimizing the latency for a given reachability constraint decreases rapidly with node density, and (2) the optimal probability for either maximizing the reachability with a given energy constraint or minimizing the energy cost for a given reachability constraint varies slowly between 0 and 0.1 over the entire range of the variations in node density. Our analysis is also confirmed by extensive simulation results.     

基于感知位置与择优连接的P2P网络搜索方法

P2P技术使互联网计算机间数据交换和信息价值共享至最大化.无结构化P2P系统已得到广泛应用,但在无结构化P2P网络中,绝大部分资源搜索方法采用泛洪或随机游走等简单机制,易加重网络通信负担和导致搜索不确定性.基于P2P网、络幂律分布和小世界特性,提出一种结合流言传播中兴趣衰减机制、感知节点位置和择优连接原则的资源搜索算法.该方法分析网络层路径性能信息以感知节点位置,利用节点度信息扩大广播范围,应用流言传播机制建立概率广播模型.采用概率方法,将搜索导向与目标相关的节点,提高搜索性能.仿真实验结果表明该模型能有效降低查询通信的开销,并快速命中目标.     

随机反馈延时下回退式ARQ协议的延时分析

对无线网络中数据业务的延时情况进行研究,在动态自适应传输模式中,提出一种反馈延时随机可变情况下的回退式ARQ协议队列模型,通过采用矩阵几何的方法计算出数据包在发送端延时的概率分布函数。对反馈延时随机可变时每个数据包传输的延时进行仿真,将仿真结果和新模型结果进行比较,验证了计算方法的正确性。     

The role of congestion in probabilistic broadcasting for ubiquitous wireless multi-hop networks through mediation analysis

Broadcast schemes play an important role in the performance of mobile ad hoc networks, which are a clear example of ubiquitous wireless multi-hop networks where nodes collaborate in a distributed way. They are widely used as a dissemination mechanism and as a part of the discovery phase of routing protocols. The simple flooding algorithm is the usual mechanism employed in mobile ad hoc networks, but its inefficiency has been demonstrated in congested scenarios due to the high number of collisions and contentions. However, these problems can be partially alleviated by using a probabilistic broadcast approach in which every node forwards the incoming packets according to a certain forwarding probability. In this paper, we use a simple probabilistic broadcast protocol to evaluate the effects of congestion on the performance of broadcasting in ad hoc networks through a mediation analysis. We hypothesize that the congestion mediates in the relationship between the forwarding probability (independent variable) and the output metric (dependent variable). We consider several output metrics according to the application of the broadcasting protocol such as reachability, broadcasting delay, packet delivery fraction and end to end delay. The simulation results show the existence of the mediating effects and how such effects may be counterbalanced depending on the target use of the probabilistic broadcast scheme.     

一种基于跨层设计的无线传感器网络自适应概率广播策略

针对盲目泛洪带来的广播风暴问题,提出了一种基于跨层设计的无线传感器网络自适应概率广播策略(APBCL).APBCL通过MAC层接收信号的强度估算发送节点和接收节点的距离,根据距离计算出转发分组的概率.APBCL减少了分组在网络中的重复传输,降低节点间的竞争和碰撞.仿真实验表明:相比泛洪和概率泛洪,APBCL在不牺牲网络吞吐率的前提下,提高了转播节省率,降低了平均端对端延迟和节点平均丢包率.     

一个基于网络并行计算环境的动态负载分配算法

网络并行计算系统具有大量的自主的计算资源,如何充分发挥它们的潜在性能,这正是负载平衡的研究内容。文中描述一个基于网络并行计算环境的动态负载分配算法,该算法能够根据系统的状态和任务之间的通信关系动态地分配系统中的负载,以实现系统的动态负载平衡。通过应用实例测试说明该算法在稳定性和性能上,优于稳定的发送者动自适应算法。     

Near-optimal message routing and broadcasting in faulty hypercubes

A distributed routing algorithm for faulty hypercubes is described. This algorithm uses a directed depth-first approach to find a path between the sender and receiver of a message whenever at least one non-faulty path exists. We show that, when an arbitrary number of elements of the hypercube can be faulty, the algorithm always routes messages using fewer than 2N hops, whereN is the number of nodes in the hypercube. This performance is shown to be within a factor of two of the optimal worst-case routing efficiency. Through foult simulations, we show that, even when up to half of the elements in the cube are faulty, complete the analysis, we prove that our algorithm is deadlock-free. Finally, we present two extensions of the algorithm. The first uses local storage to reduce the overhead of the algorithm while the second allows reliable broadcasting in the presence of an arbitrary number of faults.Supported in part by the National Science Foundation under Grant CCR-9010547.Supported in part by the National Science Foundation Instrumentation Grant CDA-8820627.