基于时延约束的快速低代价组播路由算法

低代价最短路径树是一种广泛使用的组播树,通常不能满足实时多媒体应用中信息从源端到目的端传输的时延限制。针对该问题,提出基于时延约束的快速低代价组播路由算法,利用代价构建满足时延约束的初始树,将不满足时延约束的路径用最小时延路径代替。仿真结果表明,相比时延约束最短路径树算法,该算法的计算时间更少,组播树的总代价更低。     

基于关键节点时延约束低代价组播路由算法

针对时延约束下低代价组播树的构建方法,提出了一种基于关键节点的时延约束低代价组播路由算法.该算法对已有的动态时延优化的链路选择函数进行改进,并加入关键节点和关键次数的概念.在首次选择目的节点时,重点考虑关键节点和关键次数因素,降低了选择低代价链路的时间复杂性,再利用改进后的链路选择函数依次选择节点加入树中,进而产生满足要求的组播树.实验仿真结果表明,该算法不仅能正确构建出时延约束低代价组播树,且与其他算法相比,构成组播树所需平均时间更少.     

基于MPH的时延约束Steiner树算法

为了在时延约束务件下进一步优化组播树代价,并降低算法计算复杂度,研究了时延受限的Steiner树问题.分析了MPH(minimum path heuristic)算法的计算复杂度;在此基础上设计了一个时延约束Steiner树算法DCMPH(delay-constrained MPH)用于构造时延约束最小代价组播树.该算法中每个目的结点通过与当前组播树有最小代价的路径加入组播树;若时延不满足要求,则通过合并最小时延SPT(shortest path tree)树进而产生一个满足时延约束的最小代价组播树.仿真实验表明,DCMPH算法生成的组播树在保证时延要求的情况下,与同类算法相比取得了很好的代价性能和较低的计算复杂度.     

受时延约束的组播路由算法

提出了一种新的受时延约束的组播路由算法。算法借鉴了MPH算法的思想，最初的组播树只包含源结点，然后每次将到达组播树的代价最小且满足时延约束的结点及其相应的路径加入到组播树，直到所有的成员加入为止。谊算法能够快速地得到一棵满足时延约束的组播树，并且组播树的代价也很小。实验表明：该算法简单，复杂度低，性能良好，易于在分布式环境中实现，可应用于实际的应用系统中。     

基于局部信息的时延和时延差约束的组播路由

组播通信是从一个源节点同时向网络中的多个目的节点发送分组的通信服务,它一般提供一个以上的端到端的服务约束,实际的路由算法在应用时可以受到多重约束,解决这类问题的组播路由算法是NP完全的。在研究了构建组播树的相关算法后,提出了一种新的时延和时延差约束的低代价组播路由算法-DDVMC。该算法采用基于贪婪策略的Dijkstra最小生成树算法,利用局部信息来构建低代价组播树,很好地平衡了树的代价、时延和时延差。仿真表明,该算法能正确地构造出满足约束的组播树,同时还具有较低的代价和计算复杂度。     

一种时延约束的多点到多点组播路由启发式算法

多点到多点组播路由是组播研究领域内的一个重要问题。当单棵共享组播树不能满足时延约束时,需要建立多棵共享组播树,但同时又会增加管理开销。因此,如何尽量减少共享组播树的个数成为关键问题。本文提出了一种启发式算法DCMMHA,用来解决时延约束的多共享组播树问题(DCMSMT),该问题已被证明为NP完全问题。本文算法按照特定规则生成候选中心列表,在不违反时延约束条件下,将源节点和目的节点加入共享树,并且对已选择中心进行更新。仿真实验将DCMMHA算法同其它四种同类算法进行比较,结果表明本文的算法所获得的中心数最少,显著降低了共享树的管理开销。     

一种满足时延和时延差约束的组播路由算法

针对时延和时延差约束的组播路由优化问题,提出一种最优代价组播路由算法。基于Dijkstra最短路径树算法,通过指示函数调整新加入节点的优先级,利用局部信息构建低代价组播树,使其能较好地平衡组播树代价、时延和时延差之间的关系。仿真实验结果表明,该算法能正确构造出满足时延和时延差约束的组播树,同时具有时间复杂度低、求解成功率高等综合性能。     

一种具有时延约束的组播路由算法研究*

对于多媒体应用等实时组播业务而言,组播路由算法不仅要考虑优化代价,还要考虑时延约束。针对这一问题,提出一种支持动态组播的时延受限低代价组播路由启发式算法(delay-constrained multicast algorithm,DCMA)。该算法基于DDMC算法进行扩展,采用新的指示函数和链路选择函数,综合考虑了时延和代价,有效保证了组播树的性能,而且时间复杂度低,可用于实际的应用系统中。     

时延约束动态组播路由的快速低代价算法

提出一种时延约束动态组播路由的快速低代价算法。该算法利用改进的时延约束最短路径子图,在加入组播节点时避免非时延约束最短路径的搜索,提高算法的计算效率。通过使新加入节点与树上已有节点共享最短路径,降低整棵组播树的代价。仿真结果表明,该算法计算时间少,组播树总代价低,能使组播树更稳定。     

基于共享边的时延约束组播路由算法

为了优化在时延约束下的组播树代价,降低算法计算复杂度,研究了时延受限的Steiner树问题.分析了最短路径启发式(MPH)算法的执行过程,以此为基础提出一个基于共享边的时延约束组播路由算法ESAMPH.该算法在构建组播路由树时能够优先采用包含有较多的最短路径经过的节点,这样后面的组播成员节点到树上的最短路径也有可能经过这些节点,由此实现边的共享,降低了组播树的代价.仿真结果表明,ESAMPH算法在代价、延迟和计算时间之间能获得较好的平衡,综合性能较好.     

A Heuristic Algorithm for Core Selection in Multicast Routing

With the development of network multimedia technology, more and more real-time multimedia applications need to transmit information using multicast. The basis of multicast data transmission is to construct a multicast tree. The main problem concerning the construction of a shared multicast tree is selection of a root of the shared tree or the core point. In this paper, we propose a heuristic algorithm for core selection in multicast routing. The proposed algorithm selects core point by considering both delay and inter-destination delay variation. The simulation results show that the proposed algorithm performs better than the existing algorithms in terms of delay variation subject to the end-to-end delay bound. The mathematical time complexity and the execution time of the proposed algorithm are comparable to those of the existing algorithms.     

A distributed multicast routing protocol for real-time multicast applications

Multicast routing is establishing a tree which is rooted from the source node and contains all the multicast destinations. A delay bounded routing tree is a tree in which the accumulated delay from the source node to any destination along the tree does not exceed a pre-specified bound. This paper presents a distributed routing protocol which constructs delay bounded routing trees for real-time multicast connections. A constructed routing tree has a near optimal network cost under the delay bound constraint. The proposed algorithm is fully distributed, efficient in terms of the number of messages required, and flexible in multicast membership changes. A large number of simulations have been done to show the network cost of the routing trees generated by our method is better than the other major existing algorithms.     

结合集中式与分布式特征的多路径QoS组播路由协议

提出了一个结合集中式算法与分布式算法优点的多路径启发式QoS组播路由算法和协议,它以单播路由协议OSPF传播链路的代价信息为基础,运用最小代价Dijkstra算法计算端节点到当前在树节点的最小代价路径,然后启动一个分布式计算过程得到一个可选路径集,加入节点通过一个综合性启发式选择其中的最佳路径连接到组播树．算法能够有效地支持延时和带宽受限的代价优化组播树构造,具有无环选路、呼叫接收成功率高、呼叫建立时间短、伸缩性好等特点．     

A Delay-Constrained Least-Cost Multicast Routing Heuristic for Dynamic Multicast Groups

Many new multimedia applications involve dynamic multiple participants, have stringent end-to-end delay requirement and consume large amount of network resources. In this paper, we propose a new dynamic delay-constrained least-cost multicast routing algorithm (DDCLCMR) to support these applications. When group membership changes, the existing multicast tree is perturbed as little as possible. Simulation results show that DDCLCMR performs very well in terms of cost for both, static and dynamic multicast groups, when compared to the best multicast algorithms known. Our evaluation of the cost performance of the algorithms showed that DDCLCMR is always within 10% from BSMA which has the best cost performance among all the proposed delay-constrained static multicast heuristics, while NAIVE, the well-known dynamic multicast routing algorithm, is up to 70% worse than BSMA in some cases.     

面向输电线故障信息传输的多播路由

针对无线传感器网络应用于输电线路故障传输时存在通信代价高、实时性差的问题,提出一种输电线路故障传输多播路由算法(MRFT)。抽象出输电线路故障信息传输网络模型;根据时延最短路径树(SPT)的最大端到端时延确定多播树时延上限,将时延上限边接入多播树;设计最小代价启发函数将剩余叶子节点接入多播树。仿真结果表明,与KPP算法相比,MRFT算法构造的多播树在多播树时延、端到端时延方差和多播树代价3个方面均有良好表现。该算法能够有效保证输电线路故障信息传输的实时性,降低通信代价。     

广域网中的快速组播树生成算法

在组播树生成算法中,MPH(minimum path cost heuristic)的费用性能几乎是最好的,但它的计算时间相对较长,提出了两种新的组播树生成算法：TNS-MPH(tree-mode started minimum-cost path heuristic)和NTDS-MPH(non-tree-destination started minimum-cost path heuristic).同时提出了一种使节点平均度非常精确的随机网络产生模型。新算法的仿真结果表明,新算法用较少的费用性能恶化来换取更快的计算速度。新算法比SCTF（selective closest terminal first）算法有更好的扩展性。     

Bandwidth-delay-constrained least-cost multicast routing based on heuristic genetic algorithm

We present an heuristic genetic algorithm for the quality of service (QoS) multicast routing that depends on: (1) bounded end-to-end delay and link bandwidth along the paths from the source to each destination, and (2) minimum cost of the multicast tree, where the link delay and the link cost are independent metrics. The problem of computing such a constrained multicast tree is NP-complete. We show by experiments that our proposed genetic algorithm is efficient and effective.     

TMCP: Two-layer multicast communication protocol for Bluetooth radio networks

Bluetooth is a low power, low cost, and short-range wireless technology developed for Personal Area Networks (PANs). A Bluetooth multicast group is a set of Bluetooth devices that desire for periodically receiving the multicast messages from the same source. For reducing the propagation delay and saving the bandwidth and energy consumptions, a multicast tree which connects all multicast members serves for the delivery of multicast messages. However, a given connected scatternet topology may not be appropriate for constructing an efficient multicast tree and hence causes power consumption and end-to-end delay. This paper develops a two-layer multicast communication protocol (TMCP) using role switching techniques for constructing an efficient multicast tree. The proposed TMCP collects as many as possible the members into the same piconet, reduces the length of multicast paths and assigns each member with a proper role. The constructed multicast tree has several features including as few as possible the non-member devices, the smallest tree level and the minimal propagation delay. Experiment results show that the TMCP offers efficient multicast service with low power consumption and small delay.