无线有组织网络

无线有组织网络是网络节点间有内在关系的无基础设施的无线网络,其除具有无基础设施无线网络的特征外,网络有中心节点,且节点位置关系相对固定。这种特殊的网络应用于野外救援、军事活动等临时性通信。首先回顾了对讲机系统、无线分组网络和无线自组织网络等无基础设施无线网络的结构和特点,它们都不能包涵无线有组织网络特征。详细定义了无线有组织网的相关模型,分析了无线有组织网络的特点和研究重点。     

基于对称二元多项式的全分布Ad-hoc密钥管理方案

通过研究对称二元多项式门限秘密共享,提出了一种全分布式Ad-hoc密钥管理方案.在方案中,无需可信分发者的参与,满足了门限条件的t个节点即可组建网络;新节点加入网络不需要在线节点间交互,并且新节点入网后可以获得和初始节点相同的功能,以及与其身份相对应的私钥.该方案首次将Newton插值公式应用于Ad-hoe网络密钥生成...     

Approximate Byzantine consensus in sparse,mobile ad-hoc networks

We consider the problem of approximate consensus in mobile ad-hoc networks in the presence of Byzantine nodes. Due to nodes’ mobility, the topology is dynamic. We propose a protocol based on the linear iteration method. The nodes collect information during several consecutive rounds: moving gives them the opportunity to gather progressively enough values. A novel sufficient and necessary condition guarantees the final convergence: from time to time only the correct nodes that own a value equal to (or very close to) either the minimum or the maximum value have to receive enough messages (quantity constraint) with either higher or lower values (quality constraint). Of course, nodes’ motion should not prevent this requirement to be fulfilled. New concepts are introduced to prove the correctness of the protocol. Based on particular mobility scenarios, simulations are conducted to analyze the impact of some parameters on three variants of the protocol.     

Evaluating the limitations of and alternatives in beaconing

In position-based routing protocols, each node periodically transmits a short hello message (called beacon) to announce its presence and position. Receiving nodes list all known neighbor nodes with their position in the neighbor table and remove entries after they have failed to receive a beacon for a certain time from the corresponding node. In highly dynamic networks, the information stored in the neighbor table is often outdated and does no longer reflect the actual topology of the network causing retransmissions and rerouting that consume bandwidth and increase latency. An analysis on the possible impact of beacons due outdated and inaccurate neighbor tables is needed. We quantify by analytical and simulation means the possible performance loss and explore the limitations of position-based routing protocols which use beaconing. In highly mobile ad-hoc networks, the delay can increase by a factor of 20. The neighbor table inaccuracy is the main source of packet loss in uncongested networks. We propose and evaluate several concrete mechanisms to improve the accuracy of neighborhood information, e.g., by dynamic adaptation of the timer values when beacons are broadcasted, and show their effectiveness by extensive simulation.     

Sufficient rate constraints for QoS flows in ad-hoc networks

The capacity of an arbitrary ad-hoc network is difficult to estimate due to interference between the links. We use a conflict graph that models this interference relationship to determine if a set of flow rates can be accommodated. Using the cliques (complete subgraphs) of the conflict graph, we derive constraints that are sufficient for a set of flow rates to be feasible, yet are guaranteed to be within a constant bound of the optimal. We also compute an alternate set of sufficient constraints that can be easily derived from the rows of the matrix representation of the conflict graph. These two sets of constraints are particularly useful because their construction and verification may be distributed across the nodes of a network. We also extend the ad-hoc network model to incorporate variations in the interference range, and obstructions in the network.     

Toward path reliability by using adaptive multi-path routing mechanism for multimedia service in mobile Ad-hoc network

Traditional multi-path routing mechanisms aim to establish complete node or link disjoint paths.However,under some circumstances if multiple paths cannot be established based on the current network topology,the traditional multi-path routing mechanism will degenerate into single path routing mechanism,thus the advantages of multi-path routing cannot be exhibited.To enhance the end-to-end path reliability,an adaptive multi-path routing mechanism with path segment is proposed,in which multi-path can be establ...     

Cross-layer optimized Chord protocol for separated ring convergence in MANET

an acceptable overhead for the system maintenance. Moreover, the proposed protocol can ensure the stability and scalability of the system.     

Reliable routing mechanism based on neighbor stability for MANET

One critical issue for routing in mobile Ad-hoc networks (MANETs) is how to select a reliable path that can last longer because mobility may cause frequent breakdown in radio links. A novel routing mechanism based on link lifetime estimation is proposed in this article. In this mechanism, the node's received signal strength is obtained continuously by using Newton interpolation polynomial, and by method of middle value and interception, the reference points are selected to estimate the link lifetime. With the constraint of link lifetime and hop counts, the source nodes set up the route hop by hop. The simulations show that link lifetime can be predicted regardless of mobility pattern. Moreover, the route discovery times and packet drop ratio can be reduced by the proposed mechanism, and thus improving the performance of MANETs.     

基于路径收集的Ad-hoc网络路由协议的研究

针对Ad-hoc网络中由于节点移动导致的链路断裂和RREQ(Route Request)分组泛洪的问题,提出了基于路径收集的路由协议.采用路径收集机制和链路不相交的多路径算法,提高节点获取路由的能力,增加节点的平均有效路由数量,提高RREQ分组被应答的可能性,从而限制RREQ的广播范围和转发次数;依据路径维持时间的概率密度呈指数分布的特点,设计优先使用最新路径、兼顾路径长度的路由选择策略,以在概率上延长通信路径的维持时间.NS2的仿真结果表明,与AODV、AOMDV以及AODV_PA协议相比,提出的协议提高了分组投递率,并显著地减少了路由开销和通信时延.