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.     

Loop-free hybrid single-path/flooding routing algorithms withguaranteed delivery for wireless networks

In a localized routing algorithm, each node makes forwarding decisions solely based on the position of itself, its neighbors, and its destination. In distance, progress, and direction-based approaches'(reported in the literature), when node A wants to send or forward message m to destination node D, it forwards m to its neighbor C which is closest to D (has best progress toward D, whose direction is closest to the direction of D, respectively) among all neighbors of A. The same procedure is repeated until D, if possible, is eventually reached. The algorithms are referred to as GEDIR, MFR, and DIR when a common failure criterion is introduced: The algorithm stops if the best choice for the current node is the node from which the message came. We propose 2-hop GEDIR, DIR, and MFR methods in which node A selects the best candidate node C among its 1-hop and 2-hop neighbors according to the corresponding criterion and forwards m to its best 1-hop neighbor among joint neighbors of A and C. We then propose flooding GEDIR and MFR and hybrid single-path/flooding GEDIR and MFR methods which are the first localized algorithms (other than full flooding) to guarantee the message delivery (in a collision-free environment). We show that the directional routing methods are not loop-free, while the GEDIR and MFR-based methods are inherently loop free. The simulation experiments, with static random graphs, show that GEDIR and MFR have similar success rates, which is low for low degree graphs and high for high degree ones. When successful, their hop counts are near the performance of the shortest path algorithm. Hybrid single-path/flooding GEDIR and MFR methods have low communication overheads. The results are also confirmed by experiments with moving nodes and MAC layer     

A probabilistic and opportunistic flooding algorithm in wireless sensor networks

In wireless sensor networks, many communication protocols and applications rely on flooding for various networking purposes. Prior efforts focus on how to design efficient flooding algorithms; that is, they seek to achieve full reliability while reducing the number of redundant broadcasting across the network. To achieve efficient flooding, most of the existing protocols try to reduce the number of transmissions, which is decided without considering any online transmission result. In this paper, we propose a probabilistic and opportunistic flooding algorithm that controls rebroadcasts and retransmissions opportunistically. It seeks to achieve a target reliability required by an application. For this purpose, it makes a given node select only the subset of its one-hop neighbors to rebroadcast the same message. It considers node relations such as link error rates among nodes in selecting eligible neighbors to rebroadcast. The sender controls the number of retransmissions opportunistically by tracking the current status of message reception at its neighbors. Simulation is carried out to reveal that our proposed scheme achieves the given target reliability with less overhead than other flooding algorithms in most cases, thus prolonging the network lifetime.     

Efficient DSR route request flooding with directional antennas

In this paper, an efficient scheme for flooding the DSR route request in ad hoc networks using directional antennas is proposed. The scheme makes use of the local neighbor information provided by the neighbor discovery scheme. Route request packets are forwarded to selected representative neighbors using directional transmissions instead of being broadcast to all neighbors. Two strategies are proposed to efficiently select the representative neighbors: fixed branching and honeycomb strategies. The fixed branching strategy selects one representative neighbor in each predefined forwarding direction, while the honeycomb strategy selects representative neighbors to create a hexagonal tiling pattern. Simulation results show that the proposed strategies are able to achieve a high route discovery success rate while keeping the number of involved nodes and the number of transmissions low.     

传感器网络中节点个数约束查询处理算法

对传感器网络中一类新查询--节点个数约束查询,提出能量有效的查询处理算法.算法主要由查询下发和结果回收两部分构成.查询下发算法首先根据节点个数约束查询的特点提出相关节点选择以及基于Steiner树的查询下发算法.然后对该下发算法以及一种基于洪泛的能量有效查询下发算法的能量消耗进行分析,并对比两种算法的能量消耗从中选择适当的下发算法.结果回收算法提出直接和间接两种结果回收方式,并给出两种方式在进行结果回收时能够节省能量的条件.仿真实验表明,提出的能量有效节点个数约束查询处理算法能够在满足用户查询精度的同时,使其能量消耗低于其他查询处理算法.     

移动社交网络中基于网络中心度的链路预测方法*

移动社交网络中的链路预测是指通过已知的网络节点以及移动社交网络结构等信息预测网络中尚未产生连边的两个节点之间产生链接的可能性。基于网络中心度的思想,提出一种适用于移动社交网络的链路预测算法。在该算法中,根据节点网络中心度和共同邻居数来计算两个节点的相似性指标,两个节点的共同邻居数越多、共同邻居的网络中心度越高,则两个节点的相似度越高。另外,由于移动社交网络的动态性特征,还将考虑时间因素对预测结果的影响。将该方法与其他4种常用的链路预测方法进行比较,实验结果显示所提方法要优于其他方法。     

Probabilistic flooding in stochastic networks: Analysis of global information outreach

This article investigates probabilistic information dissemination in stochastic networks. The following problem is studied: A source node intends to deliver a message to all other network nodes using probabilistic flooding, i.e., each node forwards a received message to all its neighbors with a common network-wide forwarding probability ω. Question is: what is the minimum ω-value each node should use, such that the flooded message is obtained by all nodes with high probability? We first present a generic approach to derive the global outreach probability in arbitrary networks and then focus on Erd?s Rényi graphs (ERGs) and random geometric graphs (RGGs). For ERGs we derive an exact expression. For RGGs we derive an asymptotic expression that represents an approximation for networks with high node density. Both reliable and unreliable links are studied.     

Neighborhood tracking for mobile ad hoc networks

In mobile ad hoc networks (MANETs), node mobility causes network topologies to change dynamically over time, which complicates such important tasks as broadcasting and routing. In a typical efficient localized approach, each node makes forwarding decisions based on a neighborhood local view constructed simply by collecting received “Hello” messages. That kind of neighborhood local view can become outdated and inconsistent, which induces a low-coverage problem for efficient broadcasting tasks and a low-delivery ratio problem for efficient routing tasks. In this paper, we propose a neighborhood tracking scheme to guarantee the accuracy of forwarding decisions. Based on historical location information, nodes predict the positions of neighbors when making a forwarding decision, and then construct an updated and consistent neighborhood local view to help derive more precise forwarding decisions. The inaccuracy factors of our scheme are also discussed and an accessory method is provided for possible usage. Simulation results illustrate the accuracy of our proposed tracking scheme. To verify the effectiveness of our scheme, we apply it to existing efficient broadcast algorithms. Simulation results indicate that our neighborhood tracking scheme can improve the protocols coverage ratio greatly.     

无线传感网优化生存时间的分布式功率控制

为延长无线传感网的生存时间,提出优化生存时间的分布式功率控制算法(DPCOL).该算法分析节点发送功率变化下的链路流量平衡约束,链路最大传输速率约束,节点能耗约束等条件,建立最大化生存时间的网络模型.采用分布式功率迭代和次梯度算法求解该模型.节点获知与各邻居节点通信所需要的最低发送功率集,随机选择发送功率集中的功率作为...     

基于弹簧模型的重要节点排序算法

重要节点排序是复杂网络研究的重要问题.用网络的鲁棒性和脆弱性指标评价基于引力模型的重要节点排序算法GM(gravity model)和其局部算法LGM(local gravity model)时,当度大的节点从网络中移除后,其引力较大的近邻节点的后续移除通常并不能在很大程度上影响网络的结构与功能,说明算法在重要节点排序...     

一种基于节点位置余弦相似度的机会网络转发算法

针对机会网络中数据送达率较低的问题,文中根据节点历史接触信息即节点相遇次数、相遇时间长度、节点关系稳定性来计算节点转发效用值。首先选择通信范围内效用值最大的邻居节点作为初始转发节点,再根据余弦相似度选择其他转发节点,使得转发节点能够尽可能均匀地分布。在此基础上,提出一种基于节点位置余弦相似度的机会网络转发算法(Opportunistic Network forwarding algorithm based on Node Cosine Similarity,ONNCS)。该算法使得转发节点能够均匀地分布,因此数据报文能够尽快地被转发到目的节点。实验结果表明,ONNCS具有较高的转发成功率和较低的转发能耗,转发成功率高出其他算法5%～8%。     

Distributed topology control algorithm based on one- and two-hop neighbors’ information for ad hoc networks

In this paper, we present a topology control algorithm for ad hoc networks. By considering the weight of the links, each node orders its one-hop neighbors in an ordered list and then the ordered lists are exchanged between the neighbors. This information enables the nodes to compute their transmission radius on the basis of its one- and two-hop neighbors’ information. We demonstrate that compared to the best known algorithms, the degree and transmission radius of the nodes in the topology produced by the proposed algorithm are smaller. In addition to Euclidean graphs, the algorithm works correctly on general weighted graphs. Also an extension of our algorithm is proposed which adapts its topology to network changes. Finally, we use the four metrics, node degree, transmission radius, the power stretch factor and, packet loss ratio to measure the performance improvements of the presented algorithms through simulations.     

mesh网络中基于效用转发的网络编码算法

在已有的无线Mesh网络路由算法的基础上,针对网络的动态变化性和差异性等因素带来的问题进行了研究,提出一种基于效用转发的网络编码算法.首先利用节点间的历史通信数据,动态获取不同网络环境下影响效用值的各因素所占的权重值;然后在簇头节点和汇聚节点处进行二维随机线性网络编码,结合节点的剩余能量、效用值和丢包率判断节点能否进行编码,并且采用编码包优先传输的策略转发数据包;最后综合利用网络时延、效用值和节点间的跳数,选择最优的下一跳转发节点.仿真结果表明,该算法能更好地提升数据包的转发效率,降低传输时延,提高网络的性能.     

应用IPSO的无线传感器网络分簇路由算法

在基于分簇的无线传感器网络中,网络是通过附近传感器节点在转发信息到目的节点前进行冗余数据的融合实现节能,从而延长了网络的生命周期。但现存的算法在选择簇首节点的过程中由于忽略了邻居节点的状态信息,容易导致簇内节点过早出现盲节点的现象。进化类算法已经成功应用于许多方面,微粒群算法就是其中之一。提出了一种基于改进型微粒群算法的无线传感器网络分簇路由算法来优化分簇过程。簇首节点的选取综合考虑候选节点和邻居节点的状态信息。仿真结果表明算法的性能得到了较好的改善,并延长了网络的生命周期。     

Efficient Broadcasting Using Network Coding and Directional Antennas in MANETs

In this paper, we consider the issue of efficient broadcasting in mobile ad hoc networks (MANETs) using network coding and directional antennas. Network coding-based broadcasting focuses on reducing the number of transmissions each forwarding node performs in the multiple source/multiple message broadcast application, where each forwarding node combines some of the received messages for transmission. With the help of network coding, the total number of transmissions can be reduced compared to broadcasting using the same forwarding nodes without coding. We exploit the usage of directional antennas to network coding-based broadcasting to further reduce energy consumption. A node equipped with directional antennas can divide the omnidirectional transmission range into several sectors and turn some of them on for transmission. In the proposed scheme using a directional antenna, forwarding nodes selected locally only need to transmit broadcast messages, original or coded, to restricted sectors. We also study two extensions. The first extension applies network coding to both dynamic and static forwarding node selection approaches. In the second extension, we design two approaches for the single source/single message issue in the network coding-based broadcast application. Performance analysis via simulations on the proposed algorithms using a custom simulator and ns2 is presented.     

一种高效的最小连通支配集贪心算法

连通支配集（CDS）在无线网络设计中有着广泛应用,现有多数连通支配集算法每次处理一个节点。提出了一个同时处理多个节点的贪心算法（GCDS）,依次选取最小度数节点以及该节点两跳内的一至两个节点为处理节点,当删除处理节点后剩余点不连通时减少处理的节点数,进而把节点分为支配点和受支配点;最终所有支配点构成一个近似最小连通支配集。在模拟无线传感器网络的单位圆盘图上的仿真结果表明,GCDS算法具有较低的时间复杂度,所得到的连通支配集大小优于已有算法。     

An efficient network-wide broadcasting based on hop-limited shortest-path trees

We propose a technique for reducing the number of message duplicates during network-wide broadcasting in wired networks. The key feature of our proposal is that each node keeps the information on hop-limited shortest path trees whose roots are within a certain number of hops from each node. When receiving the message, each node generates its duplicates and forwards them to a subset of neighbors, which are on the hop-limited shortest path tree rooted at the message source. The information on hop-limited shortest path trees is stored in message forwarding table of each node. We show that the hop-limited shortest path tree can be constructed in a fully-distributed manner by simply using dummy message flooding or exchanging distance vectors with poisoned reverse. Our proposal can largely reduce the number of message duplicates compared with the flooding while it is more scalable than the global-shortest-path-tree-based delivery. We also note that it guarantees the full reachability in static conditions and the time to reach of the proposal is the same as that of the flooding or the global-shortest-path-tree-based delivery. Duplicate reduction effect of our proposal is theoretically evaluated and numerically examined by simulation experiments.     

机会网络中高效的文件传输机制UH-EC

为高效地在机会网络中进行文件(音、视频)传输,提出一种基于节点性质特征的编码与效用值混合的路由算法UH-EC。将源文件编码成较小数据块,在节点的下一跳转发选取上采取基于节点特征的效用值,不断寻求转发能力强的节点承担转发任务,直到数据转发到目的节点。理论分析与仿真结果证明,与经典的H-EC路由算法相比,该算法能有效降低网络开销、分组端到端时延与黑洞节点对文件传输成功率的影响。     

A self-similar super-peer overlay construction scheme for super large-scale P2P applications

Unstructured peer-to-peer (P2P) overlay networks with two-layer hierarchy, comprising an upper layer of super-peers and an underlying layer of ordinary peers, are used to improve the performance of large-scale P2P applications like content distribution and storage. In order to deal with continuous growth of participating peers, a scalable and efficient super-peer overlay topology is essential. However, there is relatively little research conducted on constructing such super-peer overlay topology. In the existed solutions, the number of connections required to be maintained by a super-peer is in direct proportion to the total number of super-peers. For super large-scale P2P applications, i.e. the number of participating peer is over 1,000,000, these solutions are not scalable and impractical. Therefore, in this paper, we propose a scalable hierarchical unstructured P2P system in which a self-similar square network graph (SSNG) is proposed to construct and maintain the super-peer overlay topology adaptively. The SSNG topology is a constant-degree topology in which each node maintains a constant number of neighbor nodes. Moreover, a simple and efficient message forwarding algorithm is presented to ensure each super-peer to receive just one flooding message. The analytical results showed that the proposed SSNG-based overlay is more scalable and efficient than the perfect difference graph (PDG)-based overlay proposed in the literature.     

WSN中有效的最小单位圆集覆盖算法*

针对具有不同传输半径的无线传感器网络覆盖与广播数据转发问题,提出了一种以最小单位圆覆盖集作为广播数据转发集的算法。该算法能有效计算出覆盖范围的轮廓集,具有最优的时间复杂度O(n log n)。对每个节点,该算法以其最少数量的邻居节点子集实现所有邻居节点的覆盖,并证明了该算法找到的最小单位圆覆盖集与其轮廓集是相等的。详细的仿真实验及与现有算法的比较表明,提出的覆盖算法不仅以最少数量的节点实现了网络覆盖与广播数据转发,同时延长了网络生命期。